Rest and Activity Cycles for the Maintenance of Efficiency of Personnel Concerned with Military Flight Operations

I aGaED ADVISORY GROUP FOR AEROSPACE RESEARCH 81 DEVELOPMENT

7 RUE ANCELLE 92 NEUILLY-SUR-SEINE FRANCE

AGARD CONFERENCE PROCEEDINGS No.74 on Rest and Activity Cycles for the Maintenance of Efficiency of Personnel Concerned with Military Flight Operations

bY A. J. Benson

NORTH ATLANTIC TREATY ORGANIZATION -

' 'I ". ,"I,,k DISTRIBUTION AND AVAILABILITY -' ..

,/--

LGARDConference Proceedings No. 74 i ~

NORTH ATLANTIC TREATY ORGANIZATION

ADVISORY GROUP FOR AEROSPACE RESEARCH AND DEVELOPMENT

(ORGANISATION DU TRAITE DE L'ATLANTIQUE NORD)

~ *_--.-----

,," f REST AND ACTIVITY CYCLES FOR THE I MAINTENANCE OF EFFICIENCY OF PERSONNEL !I, !I, \ CONCERNED WITH MILITARY FLIGHT OPERATIONS '

Eaapers-pfesee AGARD Aerospace Medical Panel Specialist Meeting held in Oslo, Norway on 13 and 14 May 1970 The material in this publication has been produced directly from copy set and supplied by each author.

Published November 1970

613.79 : 629.7.'072

Printed by Technical Ed'dztang and Reproductton Ltd Havford House, 7-9 Charlotte St. London, RP iH!l.

ii PANEL MEMBERS AND PROGRAMME COMMITTEE

PANEL CHAIRMAN Group Captain T.C.D.Whiteside, MBE, RAF

DEPUTY CHAIRMAN Mhdecin en Chef de lkre Classe F.Violette, FAF

PROGRAMME CHAIRMAN Dr A. J.Benson

HOST COORDINATOR Colonel O.Nyby, RNoAF. MC

PANEL EXECUTIVE Major A.M.Pfister. FAF, Mc

iii SUMMARY

This volume contains the text, discussion and technical evaluat’ion of ten papers presented at the AGARD Aerospace Medical Panel’s Specialist meeting which was held in Oslo on the 13th and 14th May, 1970. The meeting was convened in response to a request from the Military Committee of NATO for advice on the influence of work and rest schedules on the operational efficiency of personnel concerned with flight operations. The papers presented fell into three main categories: a) laboratory investigations of normal and abnormal work/rest schedules, b) in-flight studies of aircrew operating long-haul transports, c) duty cycles in air traffic control tasks. Specific recommendations made during the meeting will be incorporated in a comprehensive report to be prepared by an ad hoc Working Group.

SOMMAIRE

Le present ouvrage comporte le texte. la discussion et l’evaluation technique de dix exposes faits h 1’ occasion de la reunion de specialistes organisbe par la Commission de la Medecine Aerospatiale de 1’AGARD et tenue h Oslo les 13 et 14 mai 1970. La reunion a et6 convoquee pour repondre h une demande d’avis de la part du Comite Militaire de 1’OTAN en ce qui concerne 1’ influence des programmes de travail et de repos sur l’aptitude operation- nelle du personnel charge des operations de vol. Les communications presentees ,se divisent en trois categories principales: a) Etudes en laboratoire de programmes de travail/repos normaux et anormaux; b) Etudes en vol de personnel navigant a bord d’un avion long-courrier; c) Rotations de personnel charge du contr8le de la circulation aerienne. Un rapport de synthkse h dtablir par un Groupe de Travail ad hoc comportera les recommandations formulees au cours de la reunion.

iv WELCOMING ADDRESS

Colonel Olaf Nyby, Surgeon General Royal Norwegian Air Force

Dear Members - dear Guests!

On behalf of the Royal Norwegian Air Force, hosts for this conference, it is my great pleasure and honour to wish you all a hearty welcome to these two specialist meetings, to Oslo, and to Norway.

The idea of Agard is, through a close contact between research institutions and persons - military and civilian, to stimulate and to co-ordinate scientific efforts in areas of importance to air missions in our NATO alliance - and to spread information in this field to all those who may benefit therefrom.

As Norway this time has the privilege to be the seat of the conference, we are happy to have the opportunity to see as our special invited guests representatives from agencies and groups of persons in our country who are daily facing the problems under discussion in these panel meetings. We are honoured to welcome representatives from the Armed Forces Medical Service - and from the Armed Forces department of psychology, from the Navy Medical Service, from the faculty of Medicine, University of Oslo, from the Directorate of Civil Aviation, from the State Inspectorate of Safety in Work, from the Medical Service of Scandinavian Airlines System and from the group of industrial officers in Norway - who have long been highly dedicated to the task of solving the health problems of shift work. I hope that the coming days will be valuable for all participating and attending the meetings.

V F 0 RE \V 0 R D

This Specialist Meeting was arranged in order to answer a specific question relating to rest and duty cycles in the various tasks associated with military flying. The general subject of watchkeeping has, of course, been well and truly studied in the past, particularly in the 1940s and early 1950s, but the findings cannot always be directly applied to current operational situations in which there may be greater emphasis on, for example, decision taking, work load, and the complexity of information presented.

This collection of papers brings together the views of experts in regard to some of the tasks of military aviation. The problem is essentially a practical one, which must therefore be geared to the operational situation, and the large preponderance of military scientist authors ensures that this balance is maintained. The role of the civilian academic scientist, however, is equally essential since one is applying to the practical situation the fundamental information with which both the military scientist and his civilian academic counterpart are concerned.

(T.C. D.WHITESIDE) Group Captain, Royal Air Force, Chairman of the Aerospace Medical Panel, AGARD CONTENTS

Page

PANEL MEMBERS AND PROGRAMME COMMITTEE iii

SUMMARY iv

WELCOMING ADDRESS by Col. O.Nyby V

FOREWORD by ~p Capt. T. C. D. Wh-iteside vi

Ref e rence

CONDITIONS by R.Wever 1

INVESTIGATIONS CONCERNING REACTION TIME IN RELATION TO DURATION OF /* cI SLEEP AND TIME OF DAY ( by J.Rutenfranz, J.Aschoff and H.Mann \ ,+SLEEP AT UNUSUAL HOURS, DRUGS AND SUBSEQUENT PERFORMANCE by M.F.Allnutt

EVALUATION OF SLEEP, PERFORMANCE AND PHYSIOLOGICAL RESPONSES TO ,,FROLONGEDDOUBLE CREW FLIGHTS. c-5 OPERATION COLD SHOULDER, A PRELIMINARY REPORT by V. Pegram, \V.Storm, B. 0.Hartman and D.A.Harris

\A \A SUBJECTIVE ASSESSMENT OF FATIGUE IN TRANSPORT AIRCREW by L. G. Innes

SIMULATED TIME-ZONE SHIFTS AND PERFORMANCE ABILITY: BEHAVIORAL. \%. ELECTROENCEPHALOGRAPHIC AND ENDOCRINE EFFECTS OF TRANSIENT ALTERATIONS IN ENVIRONMENTAL PHASE by J. Berkhout 6

INFLUENCE OF DUTY HOURS ON SLEEP PATTERNS IN AIRCREW OPERATING IN HE LONG-HAUL TRANSPORT ROLE. A STUDY OF SINGLE CREW OPERATIONS AND bDOUBLE CREW CONTINUOUS FLYING OPERATIONS by A.N.Nicholson 7

>DIFFERENCES BETWEEN MILITARY AND COMMERCIAL AIRCREWS' REST AND ACTIVITY CYCLES by K.Staack 8

,WORKLOAD AND PERFORMANCE LIMITING FACTORS OF AIR TRAFFIC CONTROL RADAR "SP ERA ~p R s by H. J. Zetzmann 9

'>WORK-REST CYCLES IN AIR TRAFFIC CONTROL TASKS ' by V. D.Hopkin 10

ATTENDANCE LIST 12

vii

Circadian Rhythms of Some Psychological Functions

under Different Conditions

R. Wever

Max-Planck-Institut fur Verhaltensphysiologie, 8131 Erling-Andechs und Seewiesen / Germany 1

Summary

Just as nearly all physiological functions, most measurable psychdogical functions show clear circadian'rhythms. Their measurement requires, in contrast to that of physiological functions like rectal temperature, the wakefulness of the subjects- Therefore, measurements during night time can only be obtained, either when the subjects become awakened several times from sleep, or when they are continuously awake. In the first case, there are clear circadian rhythms, for instance in reaction time, with high performance during day time and low performance during night time, In the second case, the circadian amplitude of several functions decreases, coming from an approximation of the night values to the day values. This means: performance during night time is higher when subjects are continuously awake than when they are awakened from sleep at the same time, and this difference seems to be the greater the more performance depends on decisions. This may be of interest with regard to alert readiness.

Furthermore, it would be advantageous with regard to a continuous readiness if circadian rhythms of parts of'a crew could be shifted, in order to have available at any time of the day a part of this crew at its maximum of efficiency, It has been proved, on the one hand, that, in strong isolation from the environment and under the influence of an artificial Zeitgeber being strong enough, human circadian rhythms can be shifted to any phase in relation to local time. But on he other hand, in shift workers which are under the influence of a reversed work-rest schedule, circadian rhythms remain unshifted; the reason is that they cannot avoid social contacts with unshifted people. Shifts against local tine are only possible, (1 if personnel do not perceive the shift, (2) if personnel have no direct contacts with unshifted people, and (3) if the shifted Zeitgeber is strong enough. In order to have available two groups of a crew with circadian rhythms being reversed against each other, it is proposed to try to shift both groups for each 6 hours but into opposite directions, instead of shifting only one group for 12 hourso 1-1

It is well established that nearly all measurable biological functions change their values with a period of 24 hours (1). This holds true also in men, for psychological functions as well as for physiological ones (2). This means that all these functions vary periodically, with different ranges of oscillation or different amplitudes, and with different temporal positions of their maximum and minimum values, but with equal period values of 24 hours. 0

An example for the 24-hour rhythm of some different functions is given in fig. 1. It shows results obtained from a young man, living under the influence of a strong 24-hour routine in a very constant environment (underground bunker). Rvery three hours, he was instructed to give an urine sample, and to do some tests (3). The figure ehows the 6-day course of various functions from top to bottom, the course of wakefulness and sleep, the course of calcium and of potasmi* excretion as analyzed from the urine samples, the course of rectal temperature as measured continuously, the course of the estimated duration of a lo-eec interval, and that of the oubjectively determined drive for activity (1-2-3 scale). All those different functions show a clear periodic course, the time estimation at least after the second day. As a result, excretion of electrolytes, rectal temperature, subjective 6peed as measurable in the time estimation, and subjective drive are lower during night time than during day time.

0 24 48 72 96 120 144 Time (hours) .I 3 6 9 12 15 18 zi 24 j Time of day (hours)

Fig. 1 Fig. 2 The course of some physiological and The 24-hour course of some physiological psychological functions, measured in a and psychological functions, averaged human subject under the influence of a from 12 human subjects under the in- etrong 24-hour routine in a constant fluence of a strong 24-hour routine environment for 6 successive days. in a constant environment. From (3) (From (3). 1-2

In fig. 2, results of another experiment are given, averaged from 12 human subjects. The figure shows the 24-hour course, not only for the niuue functions an in fig. 1 but in addition, the estimation of two different timo interval. (the results are very similar), the degree of acoustic adaptation of one ear a after/definite stimulus, and the subjective feeling of fatigue (thin function changes mirror-like40 the drive for activity). Also in this experiment, all 0 function. indicate a better performance during day time than during night time.

The different functions as demonstrated so far, need fundamentally different conditions for measurement. Whilst rectal temperature, for instance, is measurable continuously, and independent of the activity state of the subjectn, the other functions mentioned cannot be measured when the subject. are sleeping. As long as the urine samples have not been obtained by catheter in all our experiments, the production of urine samples needs the wakefulnes. of the subjects, but the results do not depend on the degree of wakefulnenn. In contrast to this, the measurement of psychological function. requires the active cooperation of the subjects, and this depend. on the degree of wakefulness.

In order to measure the time course of the functions mentionedl during night time, there are two possibilities: either the nubjectn are allowed to sleep, and they become awakened for several time6 for measurements, or the riubjectn ntay continuously awake during night time. In the first case, the question arinen concerning the influence of the rakenings on the circadian rhythm. In the pant years, we have done some experiment. in which the nubjectn partly were allowed to sleep during night time without rakenings, and in which the subject. partly became awakened from sleep several times during night time, in orderin do nome tests (4). Obviously, the circadian time course of psychological functions could be compared only during the day periods, and there wan no signif:icant difference. The only function which could be compared completely during the nights with and without wakenings, was the continuously recorded rectal temperature; if the tank demanded at each wakening time was emall, there was no influence of the wakening recognizable. Indeed, the greater the teat battery at each of these date., the more the rectal temperature increased when the subjects were wakened. In rueaary: there is not a great influence of rakenings during sleeping time on the rhythmic courne of biological functions.

The other possibility to get the course of psychological functions during night time, is to be awake continuously. To examine the influence of this condition, sleep deprivation experiments are necessary. A first result of nuch an experiment is given in fig. 3 which shows values of rectal temperature and of tapping with the most comfortable speed, each averaged from 12 human nubjects. The figure shows that the rhythm of rectal temperature continuem alno during sleep deprivation but with decreased amplitude, in such a ms~erthat the minimum value is higher whilst the maximum value remains unchanged. In oontrapt to thin, the course of the comfort tapping seems to be independent of nleiep (5). In summary: circadian rhythms are not a consequence of the change between nleep and wakefulness; they persist also,partly with a decreaned amplitude, when human subjects are continuously awake.

A psychiogical function of more practical interent is the reaction the to stimuli. It is known that this reaction time is the longer, and, in 1-3

asleep continuously awake

- Rectal Temperat Comfort Tapping

11111l11111111 21 0 3 6 9 12 15 1821 0 3 6 9 12 Time of day (hours)

Fig. 3 The courses of rectal temperature and of comfort tapping, averaged from 12 human subjects, for two days. During the first night, the subjects had slept and became awakened three times, in order to do some tests; during the second night, the subject stood continuously awake. From c5). addition, the amplitude of the circadian change in this time is the larger the more complex the stimuli situation. Therefore, in order to get a conspicuous circadian rhythm, and in addition, to make the task more comparable with practical applications, we use complex reactione, i.e. light signals of 4 or 5 different colours which must be answered by correepondingly different push-buttons. In fig. 4, the result of such an experiment is given, averaged from 6 male subjects (female subjects show shorter reaction times but same changes), reaction time being measured for 8 minutes in each 3 hour period (6).

Reaction time

L 600 -

580 -

560 -

540 -

520 -

500 -

rn 12 18 24 6 12 18 24 6 12 18 24 6 12 Time of day (hours)

Fig. 4 The course of complex reaction time, averaged from 6 male subjects, for three days. During thefirst and the second night, the subjects slept and were awakened each three times, in order to do some tests; during the third night, the subjects stood continuouily awake. From (6). 1-4

Within the first and the second night of the experimental time, the subjects slept for each 9 hours but they were awakened three times during each sleeping time. Within the third night, the subjects stood continuously awake. The result is that the rhythm nearly disappears without sleep. The reaction time during night time without sleep is nearly as short as during day time, and it is much shorter than during night time with sleep.

Very recent experiments with different measuring equipment and with a sleep deprivation of two successive nights confirm these results: the complex reaction time during night time is shorter if the subjects are continuously awake than if the subjects become awakened at the same objective time from sleep. Thim holds true, partly in contrast to the subjective feeling which seems to indicate a better performance after sleep. In other words: the reaction time is alway8 extremely long after awakening from sleep, in spite of the refreshed feeling after the sleep.

Theme results mean that the degree of performance depends on et least two parameters: firstly on the time of day, i.e. on the circadian phase, and secondly on the atate of activity before the performance is demanded (wakefulness or sleep). The comparison between the results shown in figs. 3 am.d 4 indicates that for some functiono (for instance, tapping frequency, or acoustic adaptation) the first influence is the stronger one, and that for other functions (for instance, reaction time, or time estimation) the second influence is the stronger one. The compari8on of all corresponding results obtained so far seems to indicate that the atate of the preceding wakefulness becomes the more important relative to that of the circadian phase themore the performance examined depends on decisions.

These results may have consequences with regnrd to alert readiness during night time, especially if decisions of the personnbl are demanded: the performance, and eopecially the efficiency with regard to decision making, is higher when personnel stays continuously awake during night than when this personnel becomes awakened before critical situations, and this is independent of the circadian variability. This holds true even if the subjective feeling of the personnel seemm to contradict to thio.

The propomal to improve performance during night time disregards circadian rhythms by ignoring the fact that the perforaace during night time is lower than during day time because of the circadian variability. In order to improve performance a160 with regard to this parameter it seems to be advantageous to shift the total circadian rhythm, for instance of partm of a crew. If this would be po8sible. at any the of the day at leaot a part of the total personnel would be available at its maximam of efficiency. But there ere some reasons to think that such a phase shift againat local the is difficult.

On the one hand, in complete imolation from natural time cue., and only under the influence of artificial Zeitgebers, circadian rbythm8 of human mubjects can be shifted to any pha8e in compari8on to local time. To illumtrate thi8 fact, two different examp1.ee will be given (7). Pig. 5 ohowon the activity rhythm and rectal temperature rhythm of a human subject under th0 influence of an artificial day of varying duration. Am can be peen, after the change to a 1-5

26.67-hour day, the phase of the artificial day, and with this, the phases of the biological rhythms, shift gradually against local time. During the third section with another 24-hour day, the phase relationship against local time is constant but nearly rever6ed.During the 4th section, the period of the artificial day (22.67 hour) is too short for the subject's circadian rhythm - it is aut of the range of entrainment. Fig. 6 shows the result of another type of experiment in which

Time (hours) Time (days) 12 24 12 24 12 24 0 12 24 2 - 4 6 8 2 10 12 4 14 16 6 18 -6 h 20 -8 22 24 23 10 - 26 3 28 2 12 t 30 L hu +6 h 34 36 :76 38 40 42 18 44 2 h 46 20 48 50 22 52

Fig. 5 Fig. 6 Circadian rhythms of human subjects under the influence of artificial Zeitgebers, with varying period (fig. 51, and with phase shifts of the Zeitgeber (fig. 6). Successive periods are drawn one beneath the other. Activity rhythms are indicated by bars (black bars: activity; white bar6: rest), and rectal temperature rhythms are indicated by the temporal position of their maxima and minima (triangles). From (7).

the phase of an artificial 24-hour day has been shifted twice against local time by phase jumps, simulating the time shift after a long-Gistance flight; the purpose of this type of experiment is to determine the dependency of the duration of re-entrainment on the direction of the time shift, as predicted by a special model. Also in this type of experiment, the circadian rhythms can be shifted to any phase in comparison to local time.

On the other hand, it is well known that shift workers who must be active during night time do not shift their circadian rhythms although their rhythm of rest and activity is necessarily reveroed (8). This holds true even in performance (9). The reason for this is that the shift workers have the knowledge of real time, and that they live in social contact with other people who are following the natural schedule. From different human experiments, w0 have the impression that the 'social' Zeitgeber is the most important one in human 1-6

subjects, and this social Zeitgeber includes the knowledge of real time. In shift workers, the social Zeitgeber is not reversed but only the rest-work schedule.

In nearly all animal experiments, a light-dark cycle is the very most important I Zeitgeber. In contrast to this, in human subjects, the social Zbitgeber seems to be more effective. In experiments in which under otherwise constant conditions only an artificial 24-hour light-dark cycle (15 hours light, 9 hours darkness, with twilight transitions) was given, all subjects showed a free running rhythm, with periods deviating from 24 hours. Obviously, the light-dark change concerned only the main illumination, and the subjects were allowed to switch on or off small additional lamps after their own choice, guaranteeing that activity rhythms deviating frodl the Zeitgeber rhythm were possible at all. An example for such an experiment is given in fig. 7; the autonomy of the rhythm (or its free running state)

0 12 24 12 24 12 24 hour

2 .4 6 8 10 12 14 16 18 20 22 24 26 28 30 days

Fig. 7 Circadian rhythm of a human subject under the influence of an artificial light-dark Zeitgeber, with a period of 24 hours. Indications: comp. figs. 5 and 6.

is proved by the amount,of the total phase shift of more than 24 hours or more than 360' against the Zeitgeber. This result means that the light-dark Zeitgeber was too weak to synchronize the circadian rhythm of this subject.

Only when the light-dark Zeitgeber is coupled with another, more social Zeit- geber, human subjects become synchronized to 24 hours. In the experiments shown in fig. 5 and 6, we used a gong which sounds every three hours during light time but only every 4.5 hours during night time (altogether 7 times per day). At each sound of the gong, the subjects must give an urine sample, and they must do some tests. If the light-dark Zeitgeber became shifted, or changed in period, the intervals between the sounds of the gong became altered correspondingly. This small additional stimulus has been found to be sufficient to make a light-dark Zeitgeber synchronize human subjects to 24 hours. 1-7

Similar results have been obtained in experiments in which crews lived in confinement, under a work-rest cycle with 4 hours on and 4 hours off duty (lo), or 4 hours on and 2 hours off duty (11). In all these experiments, a clear circadian rhythm of, for instance, heart rate or correctness of arithmetic computation, ham been observed, but in no case was the circadian period exactly 24 hours, as it has been expected from a l:3 ratio (or 1:4 ratio, resp.) to the schedule given. It has been shown (12) that in all these experiments the circadian period averaged'ak.3 hours. The obvious interpretation of this result is that the rhythm is free running, but the durations of all these experiments were too short to validate this interpretation (see above). If the interpretation given is correct, the results of theme experiments would be comparable with thoae obtained under the influence of an artificial light-dark Zeitgeber as shown in fig. 7. Furthermore a Zeitgeber consisting of a 4:k-hour or a 4:2-hour work-reet schedule, is too weak to synchronize human circadian rhythms to a period of 24 hours.

From all the results mentioned, it can be generalized that a synchronisation of human circadian rhythms to a Zeitgeber shifted against local time is only possible if social contact to local time is excluded, and if the artificial Zeit- geber is strong enough. This means, on the one hand, that the knowledge of local time, and even the perception of the shift, must be excluded. In order to fulfil this prerequisite, strong isolation from the environmental noises and from social contacts with unshifted people, is necessary. In all our experiments with single subjects or with small groups, this condition was fulfilled, but it seems to be difficult to fulfil this condition with large groups. On the other hand, the Zeitgeber shifted against local time must be stronger than, for inmtance, a 24-hour light-dark cycle, or an 8-hour (or 6-hour) work-rent schedule. In all our experiments in which subjects were synchronized to an artificial Zeitgeber (comp. fig. 5 and 61, they had not perceived consciously the change in the Zeit- geber period, or the phase shift. But in all experidments in which subjects were not synchronized to a 24-hour Zeitgeber (comp. fig. 71, they firmly believed that they had a 24-hour rhythm, and, correspondingly, that theylived under the influence of a light-dark cycle with a period devlrting from 24 hours.

Considering the results discussed so far, it would be, on the &ne hand, avantageous with regard to continuous alertness to shift the circadian rhythms of psrts of the personnel. For instance, it would be avantageoue to have available two groupm.with reversed rhythms. But it seems to be, on the other hand, hopeless to shift circadian rhythms of one group for 12 hours for practical purposes, because the shifted group must nbt have any social contact with the environment; at least during changes of guard between the two groups, social contacts are unavoidable. Perhaps, the chance to devide the personnel into two groups with reversed circadian rhythms, is a little greater if both groups become shifted by the same amount of 6 hours but into opposite directions. In this case, both groups are equivalent with regard to the temporal relationship to the environment. 1-8

References

(1) Aschoff, J.: Comparative Bhysiology: Diurnal Rhythms. Ann. Rev. F’hysiol. 581-600 (1963).

(2) Aschoff, J.: Human Circadian Rhythms in Activity, Body Temperature and other Functions. Life Science and Space Research. Proc. VII. Int. Space Science Symp. (Wien 19661, pp. 159-173. North-Holland Publ. Comp. Amsterdam 1967.

(3) Poppel, E. : Oscillatorische Vorgange in der menachlichen 2e:Lt-Wahrnehmung. Diss. Phil. Innsbruck 1968.

(4) Giedke, H.: Veranderungen der Tagesperiodik peychophysio1og:ischer Funktionen in Abhangigkeit yon den Versuchsbedingungen. Diss. med. Miinchen 1970.

(5) Poppel, E.: Tagesperiodische Veranderungen der akustischen Adaptation und des psychomotorischen Tempos mit und ohne Nachtruhe. Pfliigers Arch. 3001 11 (1968).

(6) Aschoff, J.C., H. Giedke, E. Poppel: Tagesperiodische Veranderungen der Reaktionszeit bei Wahlreaktionen. Z. exp. angew. Psych. (in press)

(7) Wever, R.: Untersuchungen zur circadianen Periodik des Menschen mit be- sonderer Berucksichtigung des Einflusses schwacher elektrischer Wechsel- felder. Bundesmin. wiss. Forschg. Forschungsber. W 69-31 (1969)

(8) Loon, J.H. van: Diurnal Body Temperature Curves in Shift Wurkere. Ergonomics 6, 267 (1963)

(9) Bjerner, B., A. Swensson: Schichtarbeit und Rhythmus. Acta med. scand. Suppl. 278, 102 (1959).

(lo) Adams, O.S., W.D. Chiles: Prolonged Human Performance ae a Function of the Work-Rest Cycle. Aerospace Medicine 132-138 (1963).

(11) Alluisi, E.A., T.J. Hall, G.R. Hawkes, W.D. Chiles: Human Group Performance during Confinement. Final Report, Contract No. AF 33 (616)-7607-M4, 1962.

(12) Aschoff, J.: Significance of Circadian Rhythms for Space Flight. In: Proc. 3rd Int. Symp. on Bioastronauticb and the Exploration of Space. (Ed. Th. C. Bedwell and H. Strughold), pp. 465-484, 1965. DISCUSSION: PAPIC2 OF DR WEVER

FUClIS Did you ever investigate the behaviour of nurses in hospitals staying on a night-time service for 5 or 6 weeks? And if so, did they show the same behaviour as the shift workers described in your presentation? In my opinion, these nurses do not have the same close social contacts as the shir"t workers and hence my not s:?o:v the same physiological. reactions.

WEVER The results obtained with nurses on night duty was similar even after long periods of night duty to those shown by shift vrorkers. There vas no reversal of the pattern of body temperature changes.

NICHOLSON How long after a normal period of sleep was reaction time tested?

WEVER Reaction time was tested and other tests were made, on average, 10-15 nins after wakening.

BENSON You employed subjective measures of drive and activity, and used an acoustic adaptation test. Could you please describe these tests in a little more detail?

\m The subject had a 1-3 scale upon which he had to indicake every three hours his own feeling of activity drive. For the acoustic adaptation tests the subject was presented with a tone for some 3 min in one ear and after that time had to match the subjective intensity of the tone with a signal presented to the other ear.

WHITESIDE In the light/daxk cycling experiment vias there a possibility of there being any other Zeitgeber other than light intensity?

WEVER No.

BERKHOUT Ability to operate a flight trainer after sudden awakening (US Navy experiments) is very poor 2nd erratic in the first 1-3 min after wakening, improves very greatly for 5-10 min thereafter, and reaches a nominal plateau between 10-15 min after wakening. This plateau is only reletively stable.

_._._.------Editorial Note

The discussion which follows each paper has been prepared from a transcript of the magnetic tape record and from discussion forms which mere completed by some of the speakers. In an atlempt to speed publication the discussants have not been submitted drafts of the edited proceedings which, in the interests of brevity and clarity, now deppart substantially from 'verbatim et litteratim'. I have attempted to convey the essential features of the discussion, though if speakers feel tht they have been misinterpreted or misrepresented, I tender my apologies, the fault is mine.

A.J. Benson

IWT!STICATIONS CONCERNMG REACTION TIME IN RELATION TO DURATION OF SLIUP AND TlME OF BAY

bY Professor Dr Dr J. Rutenfranz, Professor Dr J., Aschoff and Dr H. Mann Max-Planck-Institut f$r Arbeitsphysiologie Dortmund Max-Planck-Institut fur Verhaltensphysiologie Seewiesen 2

Investigations using a rotatiw shift operation system based on 4 hour periods/3 day cycles showed:

The maximal values of the reaction time were between mid night and 0400 hr.

Especially long reaction times were found on nights when the test persons were allowed to sleep without any additional shift-born interruptions.

The phenomenon mentioned in paragraph 2 was associated with a reduction in the duration of sleep to less than 5 hours during the preceding days of shift-operations.

The reaction time depended on the time of day as much as the preceding sleep duration.

The consequences of shift operations are discussed. 2- 1

Introduction

The maintenance of the efficiency of personnel who have to work shift duties depends upon an alteration of their circadian rhythm to match the new work and rest cycles or at least some form of adaptation to the duty at unfamiliar hours. The temporal transposition of an individual's circadian rhythm to coincide with vork and rest at unusual times of day is limited because it is very difficult to alter the prime synchronizers (Zeitgeber) of the rhythm, such as knowledge of tine of day and social contacts ("*). When a stabilized shift system is operated, the circadian rhythm may come into phase with the duty period after two or more weeks (314), but with a rotating shift system such as alteration in the phase of the rhythm cannot be expected to occur (5.6).

For certain duties a rotating shift system is obligatory. Accordingly information is required upon the factors which influence the performance of individuals who have to work at different hours of the day and night, and of the manner in which they adapt to this type of duty. Of special significance to flight operations is the mental performance of personnel engaged in rotating shift duties.

Methods

Our experiments were carried out on twelve healthy young midshipen who all volunteered to act as subjects. Preliminary studies were made on land and subsequently during a voyage of the training ship 'Jeutschland' to the Caribbean. &I land the subjects did not have to work shifts, but during the voyage a rotating shift system was operated which necessitated a watch on the first night from 00.01 hr to 04.00 hr, on the second night from 20.00 hr to 23.59 hr, and on the third night from 04.00 hr to 08.00 hr. In addition to these duties they also had to participate in the noma1 training programme from 07.00 hr to 19.00 hr.

All measures were made at 4 hourly intervals beginning at 08.00 hr. Thus it was possible to follow the circadian rhythm of a number of bodily functions, not only on days without watches, but also when sleep was disturbed by watches at different hours of the night.

The following functions were determined at every test session.

1) Oral body temperature (after 10 min bed rest) 2) Urine excretion 3) Excretion (m Equiv/hr) of sodium, potassium and calciun 4) Pulse frequency (after 10 min bed rest) 5) Multiple choice reaction time (Bettendorf-machine) In addition a daily record of sleeping hours was kept for each subject.

Results

Sleep patterns. The sleep behaviour of the midshipmen was found to be dependent upon the time of the duty watch. The mean duration of sleep in relation to time of watch is shown in Table I which shows clearly that subjects slept less than their habitual amount when required to stahd watch during the night. The greatest sleep loss was associated with the 00.01 - 04.00 hr watch, where sleep mas divided by the duty period. 3xing the time at sea, sleep was always disturbed by watch keeping, so the sleep deficit tended to become chronic, a phenomenon common to nearly dl1 types of shift work. I 2-2

TABLE 1 Mean Duration of Sleep related to Time of Watch Mean Duration of Sleep Land (no watch) 7 hr 5 min Watch (at sea) 20.00 - 23.59 hr 6 hr 24 min 00.01 - 04.00 hr 5 hr 20 min 04.00 - 08.00 hr 4 hr 38 min

ab d'l f c 'ons. king the initial test period when subjects were on land and did not keep watch, a clear circadian rhythm was demonstrated by all the variables measured. Thus body temperature and pulse frequency had maximum values at 20.00 hr and minima. at 04.00 hr. Potassium excretion reached a peak at 16.00 hr with a minimum at 04.00 hr. This paktern of activity was also reflected in the performance of the psychomotor task for the avesage reaction times were shortest when tested at 16.00 hr and 20.00 hr and longest at midnight and 04.00 hr.

When aboard the training ship the circadian rhythm exhibited by body temperature, heart rate and potassium excretion was not influenced by watch keeping duties. Only the reaction time measure showed a clear dependence upon the time at which the subject had to keep watch; the longest average reaction times were recorded in subjects who worked the 20.00 - 23.59 and 04.00 08.00 hr watches.

Devendence of reaction t ime upon duration of sleep. Subjects who had to work the night watches did not all have the same amount of sleep before they came on duty. This was in part attributable to the rotating shift system, and in part to individual patterns of behaviour. Tht? influenoe of the duration of sleep on reaction times was assessed at midnight and 04.00 hr. At both of these times, the shortest mean reaction time waa measured in subjects who had slept for 4 hr before beginning the watch. If the subject had slept for a shorter period the reaction times were proportionately prolonged, though when tested at the end of the 4 hr duty per:Lod the reaction time was shorter than that at the beginning of the watch.

Discussion

The study has revealed two factors which have a considerable influence upon the performance of a psychomotor task. Measurement of reaction times on a multiple choice discrimination task showed a clear circadian variation, with longer reaction times during the night than during the day. In addition, when subjects axe working a rotating shift system, then performance at night was further degraded and the prolongation of reaction times was a function of the duration of sleep before the duty period.

The conclusion to be drawn from these findings is that in special situations, such as flight operations or navigation where reaction times should be as short as possible, work schedules should be structured to ensure that personnel have at least 4 hr sleep before a night duty period. Because the duration of sleep depends not only upon the duty schedule but also upon personal behaviour, we consider that about 6 hr off duty is needed in the immediate we-work period if the minimal 4 hr sleep is to be obtained. 2-3

References

1. AsChoff, J.: Exogene endogene Kmponente der 24-Stundenperiodik bei Tier und Mensch. Natmissenschaften, 42, 569 (1955)

2. Rutenfranz, J.: Arbeitsphysiologische Aspekte der Nacht- und Schichtarbeit. Arbeitsmedizin, Sozialmediain, Arbeitshygiene, 2, 17 (1967)

3. Colquhoun, W. P.: Experimental studies in shift work. I: A comparison of Blake, M. J. K. and "rotating" and %tabilized" 4-hour shift systems. Edwards, R. S.: Ergonomics, U, 437 (1968)

4. Wilkinson, R. T. and Stable hours and varied work a8 aids to efficiency. Edwards, R. Se: Psychon. Sci., 11, 205 (1968)

5. van Loon, J. H.: Diurnal body temperature curves in shift workers. Ergonomics 6, 267 (1963)

6. Rutenfranz, J., Circadianrhythmik physischer und psychischer Funktionen bei H. MaM md 4-stLdigem Wachwechsel auf einem Schiff. J. Aschoff: Studia laboris et salutis (Ggteborg), 4, 31 (1970)

SLWP AT UNU3UAL HOURS. DZGS AND SUBSEQUENT PERFOIZMNCE

bY M.F. Allnutt Royal Air Force Institute of Aviation Medicine, Farnborough, United Kingdom. 3

If a pilot has to get up early in the morning to fly it long and difficult sortie, should he be given drugs to aid his sleep?

This paper reports a recent experiment in which eight trainee pilots were sent to bed at 20.00 hours, and then woken up at 03.00 hours to spend the rest of the day carrying out tests of performance.

There were four experimental conditions (No drug, Placebo, Flogadon, and Seconal), each subject spending two nights under each condition. During every alternate 24 hour period of the three weeks for which the experiment lasted, the subjects were off duty and free to sleep as they pleased. In addition to objective measures of performance and subjective measures of mood and sleep, oontinuous EEG recordings were made throughout each "experimental" night. 3-1

Introduction

A problem common to aviation is that of the pilot who is scheduled to take-off for a long flight very early in the morning and mho has trouble in getting to sleep at an atypical hour on the evening before. The study which I wish to report was carried out in the Autumn of last year and was designed to look at one solution to this problem, that of giving the pilot drugs to aid his sleep. The object of the study was to simulate the time-course of the events surrounding a sortie and to compare two possible sources of performance decrement: that due to loss of sleep, and that due to any after-effects of the drugs. There are, of course, many other consequences of us* sleeping d.rugs, such as increasing depcndonce on them, bnt these were outside the scope of this study. The basio design of the experiment was to send the subjects to bed early in the evening, either with or without a drug, and then to get then up at 0300 hours to spend the remainder of the day performing behavioural tests.

Method -1 The subjects were eight trainee aircrew whose ages ranged from 18 to 26. They had jus% completed their 15 week basic training course and ivere waiting to start flying training, All subjects were volunteers (from a pool of twelve) and the only incentive offered was an extra week's leave on the completion of the experiment. Eysenck Personalit Inventory profiles on them revealed no atypical patterns. (N = 7.60 4.3. E = 11.80 2.37. There were four experimental conditions: No Drug, Placebo, I(logadon* (5 mgs) and Seconal* (100 mgs). These were administered in a double blind balanced design, with the limitation that a subject never had drugs on two successive nights. All subjects spent two nights under each condition, making a total of eight "experimental" ni5hts per subject.

The experimental procedure was based on a 48 hour cycle. Those subjects who were scheduled to take a clrug or a placebo took it at 1900 hours. Between 1900 hours and 2000 hours they prepared for bed and vere wired up for the forthcoming EXG recording. Lights .:rere extinguished at 2000 hours and the subjects woken again at 0300 hours. They mere given one hour in which to get washed and have breakfast before testing started at 0400 hours. Testing continued, with certain breaks for breakfast and lunch etc., until 1515 hours. The subjects mere then conpletely free to do as they pleased until 1900 hours on the following night. Their sleep on the off-duty nights was uncontrolled, though its duration was recorded in their diaries. This policy of not controlling the amount of sleep two nights before a sortie was thought to be fairly typical of an operational situation. There vere tvo 48 hour base-line cycles before the start of the main experiment. These were to allow the subjects to become used to the sleeping environment, particularly the aspect of wearing electrodes throughout the night. On these base-line nights the lights mere extinguished at 2400 hours 2nd the subjects were woken at 0700 hours. Drugs were not used.

Three types of measure were obtained from the experiment, namely FXG recordings, performance measures and subjective ratings and reports. Bipolar EEC recordings .?rere taken frog each subject throughout all "base-line" and "experimental" nights. These recordings were then analysed by a

trained and experienced EEG technician. Terformance was assessed throughout the test day by means of two tests, one of calculation ability and one of vigilance. In the former, the subject was required to add columns of five 2 digit random numbers as quickly as possible, being scored both on the number that he attempted and on the number of mistakes made. The vigilance task was an auditory one consisting of a series of -5 second tones at 2 second intervals, these tones being ' presented against a background of 85db white noise. Forty of the 1,800 tones ?resented in an hour were of slightly shorter duration, and it was the subject's task to spot these shorter tones and to

* 'Mogadon'is Nitrazepam; 'Seconal' is Quinalbarbitone Sodium. 3 -2

record his confidence in this judgement on a panel of three confidence buttons. Correct detections and false-positives were recorded and the data

A major problem in this, as in other areas of stress research, is the choice of a suitable Ineasure of perfonnnce. It has been sho?;ni that the effects of sleep-degrivation are heavily task- dependent (1). The more complex the task, the more that performance is likely to suffer; but the more interesting the task, the Yess that ?erformance suffers, and this latter factor often outweighs the former. Thus it has been shom that performance on an interesting task rnay not suffer even after quite severe sleep-loss, whereas on a dull task a decrement may appear after quite a small sleep-loss. The t'uo tasks used in this experiment were designed to be simple and non-arousing and have been used both extensively and successfully in other investigations of sleep-deprivation (2). Both tasks lasted for one hour and each "test" day consisted of four alternating sessions of each test, making an overall total of eight hours. There was a ten minute break betaeen tests .:?ith a 1one;er interval for breakfast and lunch. ?he subjects slept ig individual cukjicles in a quiet well-ventilated dormitory, the temperature of vrhich averaged 16 C. On the day fol1o:ving the second base,-line night there was a total of 23 hours practice on each task, Tor the testing sessions 'subjects sat in small undecorated cubicles.

Subjective rating scales were used throughout the experiment and farther attitudes and opinions were elicited at the debriefing session held at the end of the xhole experiment;. At 1900 hours every night ("experimental" or T'off-duty") the subjects rated their inood

llesult s

Both a ??o 3rug 2nd a Placebo condition vere included in the trial. Preliminary analysis revealed no statistically significant differencesbetween these tno conditions .on any of the three types of neasure used, and so the results !vere combined and are referred to as the "KO Drug" condition. Ireither were there significant differences between the two replicrkes of each drug condition nnd so again these results are combined.

The first conment to be made about the results of the trial is that the 33G record shried that all subjects obtained an adequate night's sleep, both with and without drugs. Out of a maximum possible sleep period for each night of seven hours, subjects averaged between five and six hours. As would be expected, there was a significnnt difference botieen Seconal and the ITo Drug condition on Total Sleep time and significant differences between both drug conditions and the No Drug condition on amount of Stage 2 sleep an3 on 3elay to Sleep (more sleep/shorter delay with drugs). There were other differences in sleep patterns between the various drug

SLEEP STAGES,

Nodrug Mopoda

DEL4 10 1s1 STAGE I

TOTAL STAGE 3 AND L TOTAL REMS Tim 50 50 Imin)

LO LO

30 30

FIG 2: SU3P BY STAG73 AND COITDITION 3 -3 conditions, but few of these reached statistical significance as they were swamped by large inter- subject variations.

Sleep was rated as being significantly better under both drug conditions than under the No Drug condition, but even without drugs subjects reported that they had had an "average" nights sleep. The sleep diaries of the subjects indicated that they had slept well on their nights off *

SUBJECTIVE RATING OF SLEEP BY ORUQ.

Nodrug Mogadon

Plocebo Seconal

(when they slept in their own quarters) and this was confirmed at the de-briefing where subjects reported that they felt they could continue indefinitely with this sleep regime. A comman comment at the de-briefing was that one or two nights (often the first night without a pill) had been "bad" with the subject feeling very tired on the following day, but it was usually not possible to find a ready explanation for this poor night's sleep in terms of any EEG measure.

The subjects were questioned about the daily fluctuation of morale and it was reported to be at its lowest at lunchtime on test days, when minor quarrels were frequent. Apathy set in on the evening of the test day. This was probably exacerbated by the fact that they felt that they had exhausted the limited night life of the area and, as it was near the end of the month, money wits limited. The subjects reported that drugs were neither a help to their sleep nor a hindrance to their performance, though both these points were partially contradicted by the evidence of rating scales and performance.

The results of the calculation task revealed large betweer,-subject and between-times differences, but no statistically significant differences betweer. drug conditions. Indeed,the largest overzll difference between any two drug conditions vas very low, being of the order of three Der cent. It might be argued from this that these drugs do not affect that factor which determines the nunber of questions vhich a subject attempts. A similar pattern of response was shown on the vigilance task except that one of the derived measures, d', was significantly lower under both drug conditions than under the No Drug condition for the last two runs of the day. That is to say that the subject's ability to detect signals, if this is a fair descriptor of d', was lowered by the drugs, but this was so only for the later runs of the day which took place some 16-20 hours after the drug had been taken. There was also a significant overall drop in performance for the runs occurring just before and just after breakfast. This decrement occurred under all drug conditions and on both tasks. A correlation matrix for all the measures taken during the experiment (EEC, performance, and subjective) was produced for each of the three drug conditions. In such large matrices several of the correlations would be significant by chance, and so all isolated correlations were ignored. Those which are reported are ones in which there was a cluster of supporting correlations (ie the runs at different times of day correlated with a particular EEG measure, rather than performance on only one of the rum correlated with the EZG measure).

There was a negative correlation between vigilance performance (correct detections) on the later runs of the day and the amount of time for which the subjects were awake in the night. This occurred under the No Drug condition, but not under either of the drug conditions. Again, the effects on vigilance occurred later in the day, as would be expected from the literature (4). But there was also an effect on vigilance performance (correct detections) on the first run of the day where there was a positive correlation between the number of correct detections and Delay to Sleep under both drug conditions, but not under the No Drug condition (ie if a subject took a long time to get to sleep under the drug condition, his performance tended to be better on the first run of the following day). VIGILANCE BY TIME OF DAV. 80 CORRECT DETECTIONS

3.1

3.2

DETECTION ABILITY d'

3.3

FIG 48 VIGILANCS ~~0;lllrSINcEBY RUN AND CONDITION

Subjects ha3 rated their sleep as being better under both drug conditions than under the Ho Drug condition; and, under the drug conditions, there was a positive correlation between this rating of sleep and total amount of Stage 3 SC 4 sleep, which did not occur under the No Drug condition. However, under the No Drug condition there was a positive correlation between vigilance and subjective rating of sleep, and a negative one with subjective rating of mood. This latter finding showed thzt if a subject's mood was low in the evening, his vigilance perfornance on the subsequent day tended to be high, while if his rating of sleep was low, so too 'vas his vigilance performance. Although there were correlations between all three types of measure, few clear patterns emerged. The within-test correlations were high, as would be expected on fairly simple tests. The subjective rating of sleep correlated with oerfomance data at least as well as any of the ZZG measures, though this subjective measure of sleep did not correlate vel1 with the objective neasure. However correlations between the various measures may only be pronounced when the sleep-loss is greater and more variable.

Discussion

In the intro6uction to this Faper it was said that there vere two parts to the aroblem: "Thether the sleep loss produced by having to sleep at atypical hours caused a decrtment in performance, and whether there mere behavioural after-effects due to the drugs. No answer to the first Dart of the question can be given as both XI% and subjective ratings showed that the subjects suffered little sleep-loss. Other evidence using the sane tests (5) has shown that vigilance perfomance undergoes a steep decline when there is a drop in the amount of sleep from five to three hours a night; while a decline in performance on the calculation task only becones apparent when sleep is reduced to less than three hours a night. The perfornance levels on both tasks in this experiment were in accord with those obtained under the "no denrivation" condition in other experiments in which these tasks have been used (5).

The subjects were young, worry-free, and were sleeping in a comfortable environment. There were at least three differences betseen these people and the operational pilot who has difficulty in sleeping. The first two, age and a uncomfortable environment, can be overcome by a suitable choice of subjects and conditions; but the third, that of sleep-loss due to worry about the resoonsibility of a flight on the following day, cannot be simulated. Therefore, in future experiments, sleep may hme to be artificially interrupted in order to simulate a typical amount of sleep-loss.

To the second ?art of the question, that of whether these drugs affect perfomance, it can be said that they had no effect on the calculation task and only slight effects on the vigilance task, these occurring in the later rather than the earlier runs of the day. A decrement in d' some 16-20 hours after the drugs had been taken is not easy to interpret in operational. terms. ?or the reasons stated previously, the tasks used in research into sleep-deprivation have to be non- arousing; so simulating the in-flight phase of the sortie rather than the high interest and workload of the take-off or lnnding phases. However, it is slightly disturbing l;o see a decrement inscognitive function some 16-20 hours after a sleeping drug has been taken, particularly as this time may coincide with the difficult and potentially hazardous landing-phase of the flight. 3-5

The limited number of correlations between EEC, performanoe, and subjective measures would suggest that all are necessary for this type of research. Each type of measure provided information, but were sometimes in conflict with each other, such as over the assessment of the "goodness" of a night's sleep. There is no short-cut to predicting successfully the changes that occur when work/rest cycles are disturbed. References 1. WIXINSON, R.T. Ergonomics 1: 2. April 1964. 175-186. 2. 'IIIIKINSON, R.T. Sleep deprivation: Performance tests for partial and selective sleep deprivation. In AB", LA. & REISS, B.F. (Eds). Progress in Clinical Psychology Vol. 7. New York: Grime & Stratton. 1968. 3. GEDYE, J.L., Al", R.C. & FERRES, H.M. Brit. Med. J. June 24th 1961. 1828-1834.

4. BUCKNER, D.N. & McGRATH, J.J. (Eds) Vigilance. London: hlcgraw-Hillo 1963. 5. WIKINSON, RT., ETX'fAFfDS, R.S. & HAINES, E. Psychon. Sei. 5: 12. 1966. 471-472. 3-6

DISCUSSION: PLPER OF DR ALLNUTL'

RUTENFR4NZ What is the effect of taking drugs every day over a period of tine? iiL LIrn'PT I have no experimental data on the possible cumlative effect of either 'Mogadon' or 'Seconal' on performance, In this experiment 96 hr elapsed between drugs being given so that the results were not likely to be disturbed by cu::iulative effects.

RUTEIWIn Hovr lori did the sub:jects prnckice the tasks before the trial began? Alxl vias there any learniw efl'ect during the cmrse of the experiment?

ALLNLTl'l' Each task was performed for 2& hr in the practice period. Over subsequent days the performance aeasures were surprisingly steady, the vigilance task being better in this respect than the calculation task.

Did your subjects have brealcfast im.:tediately on vrakiw or later? I am concerned about the efi'ect of blood sugar level on perfornance.

On waking at 0300 hrs subjects hod a snack of sandniches and full. breakfast at 0800 hrs. ;Se should have controlled cdfeine intakc but if we had done this, the experinent might not have been carried out at all, 4

EVALUATION OF SLEEP, PERFORMANCE AND PHYSIOLOGICAL RESPONSES TO PROLONGED DOUBLE CREW FLIGHTS C-5 OPERATION COLD SHOULDER, A PRELIMINARY REPORT

Vernon Pegram, Ph. D. William Storm, Ph. D. 6571st Aeromedical Research Laboratory Holloman AFB, New Mexico

Bryce 0. Hartman, Ph. D. D. A. Harris, l/lt, USAF Henry B. Hale,Ph. D. USAF School of Aerospace Medicine Brooks AFB. Texas 4

SUMMARY

“Cold Shoulder was a real-world experiment designed to determine the effects on aircrewmen of marrying two crews to a jet transport and flying operational missions. Two basic crews were flown in a C-141 aircraft, utilizing either a 414 or 16/16 worklrest cycle. A battery of measures were conducted on each crew (a) oral temperature, (b) endocrinemetabolic trends, (c) electroencephalogram (EEG) for determining sleep, and (d) crew performance evaluations. The oral temperature data showed that flight per se induced a low-grade hypothermia which was more pronounced in individuals occupying key crew positions. The endocrinemetabolic data tentatively suggested that the Aircraft Commanders, as a group, experienced more stress than the other crewmembers. The sleep EEG analysis showed that both human and primate subjects suffer a significant reduction in deep sleep and dream sleep when exposed to actual or simulated flight conditions. When combined with the sleep and physiological changes, the performance data from both humans and primates suggests caution in the application of in-flight double crews. 4-1

Evaluation of Sleep, Performance and Physiological Responses to Prolonged Double Crew Flights. C-5 Operation Cold Shoulder, a Preliminary Report

Cold Shoulder was one of the major research efforts of the C-5 Crew CompositionfManagement Study. The initial statement of the study objective was to evaluate altered inflight workfrest schedules, The focus was on the bio-medical effects of marrying two crews to an airplane and flying operational missions through the system without staging. The variable of immediate pertinence is the schedule on which the two crews should alternate, the workfrest cycle. Consultants to the in-house study group suggested 4/4 as an efficient (lower limit) schedule. A workfrest schedule at 16/16, which fits well with the basic crew concept of 16 hours on duty (maximum without waivers) and 15 hours of crew rest at stages, was selected as a reasonable upper limit. It was not the intention of this program to test work/rest endurance, but simply to explore a reasonable envelope. Workfrest schedules within this envelope are also of interest (e. g., 12/12, etc) but we chose to keep the cost of the study down by looking only at the upper and lower values for this reasonable envelope. GENERAL PROCEDURE Six special flights, utilizing two basic crews, were flown in a C-141 aircraft. The C-141 utilized a DV-1 kit as seen in Figure 1 to make the sleeping conditions as close as possible to the proposed C-5 crew bunk area. Three mission profiles and two workfrest cycles were used. Mission I, which required approximately 56 hours, consisted of a series of long legs. Mission 11, which required approximately 54 hours, consisted of a series of short legs followed by a series of long legs. Mission 111, which also required approximately 54 hours, consisted of a series of long legs followed by short legs.

Each mission was flown twice, once using a workfrest schedule of four hours duration (Mode 1) and , once using a workfrest schedule of 16 hours duration (Mode 2). The resulting study of design can be seen in Table 1, and the Mission legs can be seen in Table 2. TABLE I BASIC DESIGN OF THE STUDY 1 2 3 MODES All Long Legs ShortfLong Legs LongfShort Legs 1. work/rest first fifth third 414 2. workfrest fourth and second sixth 16/16 seventh:: * repeat of aborted mission

TABLE I1 Mission No. 1 KCHS- KTIK- PAED-R JT Y -VVVS -RODN-PAED-KTIK- KCHS - (all long legs) No. 2 KCHS - KTIK- KSUU - KT CM- KDOV-E GUN- PAED - KTIK- KCHS - (short legs followed by long legs) No. 3 KGHS - KTIK- PAED-E GUN- KDOV - KT GM- KSUU - KT IK- KCHS - (long legs followed by short legs) KCHS - Charleston AFB, S. Carolina KTIK - Tinker AFB, Oklahoma PAED - Elmendorf AFB, Alaska RJTY - Tokota AFB, Japan VVVS - Tan Son Nhut AFB, So. Vietnam KSUU - Travis AFB, California KTCM - McChord AFB, Washington KDOV - Dover AFB, Delaware EGUN - Middenhall RAF, England The subjects were line-assigned aircrewmembers from the 3rd Military Airlift Squadron. They were formed into two basic crews (six men per crew) representing a cross section of all crews in the squadron. Nine of the aircrewmembers (two Aircraft'commanders, two CO-pilots, two Flight Engineers, two Navigators, and ore 'Loadmaster) were the prime test subjects. Furthermore, a team consisting of a Flight Surgeon, Research Scientist and a Project Officer (qualified C- 141 flight examiner) accompanied each flight. Finally, a presentation of the schedule followed and the type of data collection requirements can be seen in Figure II. This example shows how both Mode 1 and 2 were conducted under Mission 1 (all long legs). COMFORT PALLET

SLEEPING QUARTERS A

LOUNGE 5

QUARTERS C a nl

Workload Form x # # # (Start here and obtain data after every crew change)

# # # # (Star? here and obtain data during each sleep period) ### ############ ### ############ ### ########I/###

Elapsed Time 0 4 8 12 16 20 24 28 '32 36 40 44 48 52 56 60

Mission I Mode I I Crew A -Do-0 ----- 0 -00 Crew B nu0 0 n o

DATA COLLECTION SCHEDULE FOLLOWED DURING A TYPICAL RECOVERY PERIOD Elapsed Time 68 72 76 80 84 88 92 96 100 104 108 112 116 120 124 128 Workload Form # # # # Sleep Survey # # # # Fatigue Rating ### ## #### ## Urine ### ## #### ## Oral Temp ### ## #### ## Sleep Periods Figure II: Diagrammatic presentation- of the work/rest- and data collection schedule followed during the flight and recovery periods for Mission # 1. 4-3

100.0 -.-.- MODE I 99.5 MODE 2 (2) ELAPSED TIME RECOVERY

98.0 97.5 97.0 96.5 - (2) (6) (IO) (14) (18) (22) (26) (30) (34) (38) (42) (46) (50) (54) I I I I I I

Figure 111: Mean oral temperature during Mode 1 and Mode 2 for 54 hours of flight and recovery conditions. The Mean is based on eight aircrewmembers.

100.0- -.-.- h MODE I LL 99.5- 0 MODE 2 U W 99.0- LOADMASTER K 3 F 98.5 - a K - W 98.0 a 5 - w 97.5 I- - J 97.0 a K 96.5- AIRCRAFT COMMANDER 0 96.0’ I I I 1 1 I I I I I I I I I 1000 1800 0200 1000 1800 0200 1000 TIME OF DAY (HOURS)

Figure IV: Mean oral temperature during Mode 1 and Mode 2 for aircraft commanders and loadmaster. I 4-4

RESULTS AND DISCUSSION The results will be presented and discussed under four major headings: a) oral temperature, b) preliminary endocrine -- metabolic trends, c) EEG sleep data and d) in-flight evaluations. Oral temperature - the factors of interest were: a) time of day, b) flight modes, and c) crew position. The times at which temperature determinations were made during each of the s'uc flights corresponded to 1000, 1400, 1800, 2200, 0200 and 0600 hours, Eastern Standard Time. During post flight periods, which were also of 54 hours duration, oral temperature determinations were made at 1000, 1400, 1800 and 2200 hours EST. The crew means can be seen in Figure I11 and show that the flight curves for both 4/4 and 16/16 are low relative to the recovery curves. This variability related to test conditions indicates that flight induced low-grade hypothermia which, according to Seyle (1) is characteristic of acute stress, regardless of the nature of the stressor. Circadian periodicity is evident on the flight days, as well as on recovery days (Figs. 111 and IV); but the amplitudes of the cycles on the flight days are subnormal. The present findings show qualitative agreement with those of van Loon (2), who studied persons changing from dayshift to nightshift work and noted that in association with accustomed sleep/wake schedules, oral temperature cycles tend to flatten. The present study and the van Loon study had, as a common feature, unusual sleep/wake schedules. However, since flying was not a factor in the van Loon study, only qualitative agreement with the present findings could be expected. The variability related to crew position indicates that different crew positims are subjected to differential grades of acute stress (Fig. IV). The primary conclusion reached from this evidence is that flight per se induced a low-grade hypothermia which was more pronounced in individuals occupying key crew positions. A secondary conclusion reached is that flight affected the oral temperature periodicity by reducing the amplitude and possibly changing the time of occurrence of the minimum temperature. Finally, these differences were more pronounced for the 4/4 schedule, suggesting that the 4/4 schedule is more stressful than the 16/16 schedule. Due to a combination of factors no significant phase shift related to time zone transition occurred during these flights. These factors were: (a) the speed of the round trip (54 hours), (b) flying both westward and eastward in each mission, and (c) the short amount of time spent in each time zone. Pre- vious studies of phase shifts in the body temperature rhythm have not made a continuous round trip (3,4). This experiment was unique in that the missions were roundrobins without stopping in any one location for extended periods of time. For example, Mission I was flown to SE:A and back in 56 hours. We suggest that because the trip was completed in such a short time, a phase shift did not start. Ac- cording to Sasaki's estimate (5) the maximum shift would have been only two hours if the entire period encompassed by the flight had been spent in one locale. However, the brevity of the time spent in each locale seems to have precluded any effects changing time zones may have had. Additionally the direction of any possible phase shift would be speculative since time zones were traversed in both an eastward and westward direction. In fact approximately half of each flight was eastward and half westward. So it would seem that any effects of going eastbound were cancelled out by turning around and going westbound at the half-way point. Endocrine-Metabolic Effects - This preliminary report will only deal with the specimens which were collected late in each of the six test flights since the total analyses will exceed 25,248 and require many months. We reasoned that flight effects would tend to be maximal as flight (mission) time approached 50 hours, thus the results presented will cover the findings in this phase of the study. This report gives data for urinary epinephrine, norepinephrine, 17-hydrosycorticosteroids (17- OHCS), urea, phosphorus, potassium, and sodium. Stressors of various types are known to induce elevations in these particular urinary constituents. Epinephrine reflects adrenomedullary activity, norepinephrine reflects sympathetic nervous system activity, and the 17-OHCS reflect adrenocortical activity. The remaining urinary constituents reflect catabolic activity. The data given in this report are for two Aircraft Commanders, two CO-pilots, two Flight Engineers, and two Navigators. The Loadmaster is not considered at this time. In organizing these data, those for the three Mode- 1 flights were pooled, as were those for the three Mode-2 flights. In the Mode-1 flights, the work and rest periods were each of four hours duration; in the Mode-2 flights, the work and rest periods were each of 16 hours duration. Regardless of flight modes, the flyilig and urine collection schedules were kept constant. Consequently, in each flight, the u-rine collections were made at times which corresponded to 1400, 1800, 2200, 0200, 0600, and 1000 hours, Eastern Standard Time. Thus, it was possible to deal with the circadian periodicity which is known to exist among those particular physiologic processes under ordinary circumstances. The pre- existing periodicity was entrained to Eastern Standard Time; and this periodicity was expected to carry over into the 50-hour flight periods. Table ILI gives 24-hour values for the urinary variables, with Mode-1 values presented separate from Mode-2 values. Each 24-hour value is the mean for eight men, each of whom was studied during three flights, with six determinations per flight. The central tendencies thus brought out can therefore be expected to meaningful, despite the lack of statistical testing. Table JII also presents data obtained in a 4-5

previous investigation (Aerospace Medicine 40: 418, 1969). These additional data provide perspective, for they represent dissimilar circumstances, namely, nonstressful ground duty and a 24-hour flight. The flight was made in a different type of aircraft from the one used in the previous effort; but the factor of flight duration, rather than aircraft type, is to be emphasized. The previous and present data give a composite picture of the stress responses induced by flight of extremely long duration, ranging from 24 to 50 hours. Verification of the early trends will be possible when the full set of data for the C-141 crewmembers is available. TABLE I11 DATA SUMMARY

Previous Study Present Study URINARY 24-Hr 50-Hr Flight 50-Hr Flight VARIABLE* Control Flight (Mode- 1) (Mode-2) Epinephrine (mg) 0.73 1.61 0.99 1. 09 Norepinephrine (mg) 3.42 4.10 4. 91 4.45 17-OHCS (mg) 236 224 310 3 14 Urea (mg) 1113 1427 1331 1365 Phorphorus (mg) 53 45 45 42 Potassium (m Eq) 2. 6 2.2 3.7 3.4 Sodium (m Eq) 7.1 7.4 11. 6 12.1 Ratio: Na/K 3.2 3.4 3.8 4.1 *Each urinary variable except Na/K is expressed as a creatinine-based ratio (quantity/100 mg creatinine). Each value is a 24-hour mean which represents three flights, with six determinations per flight per man.

The 50-hours flights appear to have induced more intense stress than resulted from the 24-hour flight, for all of the urinary variables except phosphorus were relatively high during 50-hour flights and only three (epinephrine, norepinephrine, and urea) were relatively high during the 24-hour flight. Particular significance is the finding that adrenocortical hyperactivity developed only in the longer flight tests. As a tentative conclusion, we offer that the flight modes did not have differential influence on the 24-hour values for these particular urinary variables, when evalbated by means of amplitude changes (Table 111). Crew position was thought to be a factor contributing to the severity or intensity of the stress responses. Table IV shows a breakdown of the urinary data by crew position. Flight modes are also considered in this breakdown. The values are all 24-hour means. The control values given in Table III have been repeated here. As the most important finding, the Aircraft Commanders had values for epinephrine, norepinephrine, 17-OHCS, phosphorus, and potassium which exceeded those of the remaining crewmembers. Furthermore, the Aircraft Commanders had, for certain of these variables, higher values in Mode- 1 flights than in Mode-2 flights. Specifically, the Aircraft Com- mander's epinephrine, norepinephrine, potassium and sodium values were all higher during Mode- 1 flights than during Mode-2 flights. We conclude tentatively that, in certain respects, the stress responses of the Aircraft Commanders to Mode-1 flights were more intense than those to Mode-2 flights; and we further conclude tentatively that the Aircraft Commanders, as a group, experienced more intense stress than the other crewmembers. The Flight Engineers in a number of ways seem

' to be a close second to the Aircraft Commanders. The Navigators, when involved in Mode-1 flights, had nearly normal values for a number of urinary constituents. TABLE IV URINARY VALUES IN RELATION TO CREW POSITION URINARY FLIGHT CREW POSIT ION VARIABLE* MODE Commander CO-pilot Engineer Navigator CONTROL Epinephrine 1 1.49 0.82 0.91 0.72 0.73 (mg 1 2 1.12 1.01 1. 18 1. 03 Nor epinephrine 1 6. 31 4: 23 5.22 3. 88 3.42 (mg) , 2 5.40 3.87 4.29 4.24 17-OHCS 1 355 322 3 14 249 236 (mg) 2 38 1 309 295 270 Urea 1 1280 1379 1412 1253 1113 (mg) 2 1268 1346 1575 1270 DlSCRlMlNATED AVOIDANCE PROGRAM

WHITE RED

LEVER

RED 10" WHITE 30" I SMOCK PRE-AVERSIVE WARNING

FOOD REINFORCEMENT PROGRAM

GREEN

FOODHOPPER m FOOD LEVER

FOOD PELLET AVAILABLE ON

THE AVERAGE OF EVERY 60 SECONDS

Figure VI: Schematic representation of stimulus panels and temporal sequences of the behavioral programs used during the primate experiments.

C 4 -AI (EEG)

Figure V: Electroencephalogram (EEG), electroculogram (EOG) and electromyogram (EMG) placement used for monitoring aircrew sleep. 4-7

TABLE IV (CONT'D)

URINARY FLIGHT CREW POSITION VARIABLE* MODE Commander CO-pilot Engineer Navigator CONTROL Phosphorus 1 48 48 43 40 53 (mg) 2 44 42 44 38 Potassium 1 4.6 3.3 3.5 3.3 2. 6 (mE4 2 3.7 3.2 3.5 3.2 1 12.6 10.8 14.0 9. 0 7. 1 2 10.5 11.2 15. 1 11.4 Ratio: Na/K 1 3.4 3.7 4. 7 3. 2 3.2 (mEq/mEq) 2 3.2 3.8 5.0 4. 3

*Each urinary variable except Na/K is expressed as a quantity per 100 mg creatinine. Each value is a 24-hour mean which represents three flights, with six determinations, per flight per man. EEG Sleep Data: Two experimental sleep studies were initiated to validate the concept that the C-SA aircraft could efficiently remain airborne for extended periods of time by flying with a double crew. Of critical importance to this concept is the ability of crew members to obtain adequate sleep during "off-duty" or rest periods to prevent deterioration of performance, crew interactions, and overall motivational levels. The first series of experiments (Cold Shoulder Sleep Studies) investigated sleep patterns recorded from human subjects during flight in the (3-141. A problem of experimental control existed in these studies in that it was not possible to have exact knowledge of the activities and sleep habits of the subjects immediately before and after the experimental flights. In order to attain such control and supplement the human in-flight data, a second series of experiments were performed using primates as subjects. a) Human in-flight sleep data. Before the C-141 flights ended it was possible to record six navigators during their sleep periods on Mode-1 and Mode-2. The EEG flight package consisted of an FR-1300 recorder with a locally built voice channel, Leach EEG amplifiers and ECG amplifiers used in cascade (powered by 45 volt and 6 volt dry cell batteries), a dual beam 564B storage oscilloscope (to monitor EEG before it went to tape), Beckman Ag-Agcl min- iature biopotential skin electrodes, NASA electrode paste and solid state inverter (28 VDC to 110 VAC at 60Az). The procedures for recording the navigators during the sleep periods were those established in "A manual of standardized terminology, techniques and scoring system for sleep stages of human subjects" (6). The electrode configuration can be seen in Figure V. After each flight the magnetic tapes were played back on a polygraph machine and then staged according to the above-mentioned manual. The sleep recordings staged into four categories: awake, Stage 1-2 (light sleep), Stage 3-4 (deep sleep) and dream sleep (rapid eye movement, REM). Even though the Mode- 1 and 2 schedules were not normal diurnal patterns, an attempt was made to combine the sleep stages percentages so that these results could be compared to laboratory data. Thus, we were able to compare these results with some "norm" and talk about what changes in sleep quality and quantity might occur in a 50-hour flight while flying double crew. First in terms of quantity, we simply added up the total amount of readable EEG tracings for each subject. The average resting and sleep time for the six subjects was 12.2 hours. This figure compares very favorably with the 14 hours normally obtained during a similar period at home or in a laboratory setting. In terms of quality, the picture is quite different. As seen in Table V when the over-all percentages for the two schedules were compared with a male population of approximately the same ages, there were striking differences (7). TABLE V COMPARISON OF SLEEP PERCENTAGES Stage 16/16 -414 Normal A 15. 0 22.0 1.0 1-2 67. 0 63.,0 54.0 3-4 10.0 11.0 21.0 REM 8.0 4.0 24. 0 40 -

30 -

20 -

IO -

BASELINE-2 SIYULIIION RECOVERY - I RECOVERY -2

Figure VII: Primate sleep and awake percentages recorded 'during Mode 2 (16/16 schedule).

AWAKE

s a w I STAGES 1-4 'I50 v-

~ I 2 3 4 5 6 FLIQHT I BASELINE 1 I RECOVERY I

DAYS Figure VIE: Primate sleep and awake percentages recorded during Mode 1 (4/4 schedule). 4-9

Compared to Williams' subjects, these navigators had about 18 times more awake, 112 the amount of deep sleep and 114 the amount of REM or dream sleep. The results are highly suggestive and indicate that care must be taken in planning flights involving double crews. The fact that none of the six navigators was able to obtain a normal amount of the most important sleep stages is a strong warning. This loss of deep sleep and REM sleep during both schedules is disturhing for laboratory simulator work would predict "better" sleep in Mode-2. Perhaps during flight the schedule is less important than the actual flight conditions of noise, turbulance, inter- ruption of circadian cycles, interpersonal crew interactions or concern about aircraft responsibility. The last point that should be stressed is the adaptation to flying double crew. It appeared from these records that some of the men slept good at first and then began to have difficulty getting any deep sleep. Others slept very fretful at first and then improved as the flight progressed, probably due to fatigue. The important thing in this regard is the lack of control over the pilots before and after the flight. If projects of this nature are to be successful, then exact knowledge of the activities and sleep of the crews must be known both before and after the flight. Otherwise it will be impossible to answer the important question of whether or not crews could adapt to the proposed double crew schedules. This study has given us enough information to suspect that obtaining "good" sleep on an aircraft will be difficult. Exactly how this sleep loss can effect performance, interfere with crew interactions or effect the overall motivational levels cannot be understood until better controlled studies are conducted. b) Primate data - the subjects were five adolescent Macaca mulatta monkeys, which were surgically implanted to record brain temperature, electroencephalogram (EEG), electroculogram (EOG) and electromyogram (EMG). During eight waking hours each day, the subjects were trained to respond on a multiple reinforcement schedule for food reward and shock avoidance (See Figure VI). After behavioral stability had been achieved, the subjects were sequentially exposed to the experimental series of simulated flight environments. A temporal description of the experimental sequence is given in Table VI. A total of six experiments were performed utilizing the 16/16 worklrest schedule. During the 48-hour Flight-Simulation phase the levels of noise, temperature, vibration, lights and altitude was adjusted to match the specification requirements of the C-5A crew rest area. TABLE VI EXPERIMENTAL TEMPORAL SEQUENCE

Monday 8:OO AM Tuesday 8:OO AM Thursday 8:OO AM Saturday 8:OO AM to to to to Tuesday 8:OO AM Thursday 8:OO AM Saturday 8:OO AM Monday 8:OO AM

Placement and Ba s eline Flight-Simulation Recovery Checkout 8-16-8-16 16-16-16 24-8- 16 cycle cycle cycle

Work/Rest/Work/Rest Work/Rest/Work Rest/Work/Rest

For purposes of analyses, the data from each of the six experiments were combined, yielding a total subject sample of 23. The EEG, EOG, and EMG analog sleep recordings obtained during the first 10 hours of each rest period were sleep staged by hand in accordance with Rechtschaffen and Kales (6). The percentage of time spent awake, in Stages 1-4 (slow wave sleep), and in REM were obtained for each subject. These data were submitted to a Friedman two-way analysis of variance (8). When compared to the average sleep pattern during the second rest period of the Baseline phase (14.4% REM, 72.8'7" Stages 1-4), the conditions of Flight-Simulation resulted in a significant reduction (p > .001) in both cases in time spent asleep (7. 9% REM, 59. 0% Stages 1-4). While the amount of lost sleep varied greatly between subjects, 22/23 subjects revealed a decrease in REM and 19/23 a decrease inStages 1-4. During the Recovery phase, the average sleep patterns recovered toward pre-Flight- Simulation levels. These changes, and the corresponding reciprocal changes in wakefulness, are presented in Figure Vu. As can be seen in Figure VIII, the primate 414 sleep data also shows a significant reduction in Stages 1-4 and REM sleep. However, the severity of this reduction is much less as the "50-hour flight" progress, showing a definite sleep adaptation to the 414 schedule. Also for the primates the performance was less effected during Mode- 1 than during Mode-2. The performance data were also responsive to the environmental changes accompanying Flight- Simulation (Fig. IX). Again using the Baseline phase as a reference, the first work period of the Flight-Simulation was accompanied by a significant increase (p > . 01) in the number of responses per hour occurring during the pre-aversive 30-second interval. However, the most impressive effect of Flight-Simulation upon performance was the six fold increase (p > .05) in the average number of shocks delivered during the second work period of Flight-Simulation (Fig, IX). As was the case in the sleep data, there were great individual differences in the amount of increased shock deliveries, but an increase occurred in 19 of 23 cases. Following a period of rest during the recovery phase, the number of shocks 4-1 0

120 -

a ;loo- w z :80- =

o(z Z 60 - Y 3) 40 L 0 - PRE-AVERSIVE 30 SEC INTERVAL - IO-SEC WARNING INTERVAL

I 1 I I

K 5- .v) 5 4- 0 In z 3- z aY 2- 3)

I-

BASELINE-2 FLIGHT RECOVERY SIMULATION -I SIMULATION- 2

EXPERIMENTAL PHASE OF WORK

Figure IX: Mean number of lever presses and number of shocks administered during four work periods.

E XPE R I MENTAL RECOVERY - I Y v) W BASELINE 2 W 37 - e 3 RECOVERY -2 n

I I I I I I LIGHTS 2 4 6 8 IO OUT

HOURS OF REST

Figure X: Changes in average brain temperature between and within four rest periods. 4-1 1

presented during the Recovery work period was reduced to about one-half. The findings of the primate experiments reinforce and emphasize the previous findings of the Cold Shoulder Sleep Studies. Both human and monkey subjects suffer similar disruption of normal sleep patterns when exposed to the conditions of simulated or actual flight. The possible severity of such sleep disruption is suggested by the performance findings presented in Figure M. In terms of the average number of shocks administered, performance was not affected during the first Flight-Simulation work period. That is, the conditions of increased noise, vibration, and altitude did not directly result in an increase in shocks. However, following the Flight-Simulation rest period, during which normal sleep was not acquired, performance was affected as indicated by a radical increase in the average number of shocks delivered. As suggested in Figure IX this increase in shocks cannot be attributed to a decrement in responding. In fact, the net amount of responding was greater during this work period than the amount during Baseline, when very few shocks were delivered. Thus, the loss of normal sleep led to a reduced efficiency in performance. The brain temperature data further support the finding that normal sleep was disrupted during the Flight-Simulation rest period. Brain temperature typically decreases during sleep. As presented in Figure X average temperature did decrease during the rest intervals of all experimental phases. How- ever, the decrease during the Flight-Simulation rest interval was never as great as that during other rest periods. Although lower than that during Flight-Simulation, brain temperature was still elevated during the initial Recovery phase rest interval. During the second Recovery rest interval, brain temperature dropped even lower than that attained during Baseline. This occurrence most likely represents a recovery or compensation effect. Eva hations : Table Vu summarizes the general analytical approach to the psychological data obtained during Operation Cold Shoulder. It gives the factors of major interest, the areas measured, and the instruments used to measure these areas. It is very interesting to note that while the subjective fatigue ratings show a significant change, the crew performance ratings show little or no decrement, even though they were unquestionably experiencing partial sleep deprivation. It should be pointed out that the above mentioned interactions did result in the abortion of mission number four, which was a 16/16 schedule. This was the only mission where definite performance decrements were noted by the evaluation team. These errors were missed clearance, variations in airspeed, climb rate and slow course corrections and long reaction ti= to notice the boost light flashing. TABLE VI1 GENERAL ANALYTICAL APPROACH Factors of Interest Areas Measured & Instruments used WorkIRest Cycle Mission Profile Recovery Crew Position

N. S. p 4.01 1

Crew Performance 1. Debriefing 414 vs 16/16 I, vs II, vs Lu 1. N. S. N. S. 2a. N. S. N. S. 2b. N. S. N. S. 3 N. S. p<.O5 2. Rating (overall) 414 vs 16/16 N. S. I, vs II, vs III N. S. a. preflight &T.O. N. S. N. S. b. inflight N. S. N. S. c. descent &landing N. S. N. S.

Sleep 1. Sleep Survey 4/4vs 16/16 I, vs 11, vs ILI 414 vs 16/16 414 VS 16/16 N. S. N. S. I, vs 11, vs Lu I, vs II, vs III 2. EEG tracings 414 vs 16/16 p<.o1 All flights for days

Mis c e llane ous 1. Workload report 414 vs 16/16 I, vs 11, vs LTI 4/4vs 1611.6 . 414.v~16/16 I, vs 11, vs.III I, vs 11, vs 111 All flights REFERENCES

1. Selye, H. The physiology and pathology of exposure to stress. Montreal: Acta, Inc., 1950.

2. van Loon, J. H. Diurnal body temperature curves in shift workers. Ergonomics 6: 267-273 (1963).

3. Hauty, G. T. and T. Adams. Phase shifts of the human circadian system and performance deficit during the periods of transition: U. West-East flight. Aerospace Med. 37: 1027- 1033 (1966).

4. Hauty, G. T. and T. Adams. Phase shifts of the human circadian system and performance deficit during the period of transition: III. North-South flight. Aerospace Med. 37: 1257-1262 (1966).

5. Sasaki, T. Effect of rapid transposition around the earth on diurnal variation in body temperature. Proc. Soc. Exp. Biol. Med. 115: 1129-1131 (1964).

6. Rechtschaffen, A. and Kales, A. A manual of standardized terminology, techniques and scoring system for sleep stages of human subjects. U. S. Department of Health, Education, and Welfare, NIH, 1968.

7. Williams, R. L., Agnew, H. W. and Webb, W. B. Sleep patterns in young adults: An EEG study. EEG and Clinical Neurophysiology, 1964, 17: 376-381.

8. Siegel, S. Nonparametric statistics for the behavioral sciences. New York: McCraw-Hill, 1956. 4-1 3

DISCUSSION: FAPER OF DR PZGRAEI et AI.,

,TrlITESLUE In your operational study thc aircrew felt tired but no performance decrement was detected. This could be because the men were making a deliberate effort to maintain arousal. But vrouylyou expect that in such conditions their ability to deal with emergencies - their spare capacity - would be decreased? ?EGWi Yes, I agree. But it is almost a physiological law that arousal is maintained in order to inaintain performance. Je had no task, indeed I find it difficult to design such a task, which would allow the likely decrement in capaqity to be detected.

In subjects who are tired, continuous performance tasks will show an increase in errors, but important command functions will be maintained at a high level until a general breakdown occurs.

You said that from the physiological viewpoint there vias no difference between the 16-16 hr scoedule and the 4-4 hr schedule. However, the 4-4 hr schedule snowed a substantially greater reduction in REEJ sleep than the 16-16. Do you put no significance on this finding at all?

PEGFWI I fear that I over-generalised. However, when there is more than a 50';; reduction in RE31 sleep the.efr;'ects are severe,

NICHOLSON But with a 4-4 schedule man could quickly become REZd deprived, while with the 16-16 schedule this is unlikely.

PEGWd This may be true, but we must not forget the adaptation which occurs with the shorter rest and duty cycles. On a 4-4 hr schedule deep sleep is established sooner, so that over a period the man may not become deprived of REM sleep.

UICHOLSON Wmt did the aircrew consider to be the optimum rest and duty cycles and the optimum period dor which this schedule could be worked?

PZGMrE We chose schedules which vre considered represented the upper and lower limits of rest/duty cycles. On debriefing many aircrew expressed the opinion that a 10-10 hr or 12-12 hr cycle would be more acceptable than the 4-4 hr and the 16-16 hr schedules employed.

NICHOLSON That is interesting, for in thc W we have found a 10-10 hr schedule for double crew operation to be satisfactory over a 48 br period.

BEIFSOX The effect of loss of ZEiI sieep was raised earlier, but Johnson has stated that it is not the type of sleep vrhich determines subsequent performance, rather the total amount of sleep. Vlould any speaker care to clarify this problem for me?

Many studies have shown that continued loss of REEJ sleep produces performance or behavioural decrements. Johnson's study to which you -qiere probably referring was made on subjects,who were already sleep deprived, who were selectively deprived of REM or Stage 4 sleep in the following rest period. It is in such sleep deprived subjects that the total amount of sleep rather than the,quality of the sleep is the more important.

'iIEVER In your special conditions, sleep deprivation seems to be correlated with decreased body temperature. In all our experiments in constant environmental conditions, sleep deprivation is correlated with an increasing rectal temperature. Nay this difference be based on environmental temperatures in the flight environment compared with our laboratory conditions?

PZGWJ This is possible, because in flight the cabin temperature varied between 70-80$ perhaps even more. I would not care to conclude that the decreased body temperature was a consequence of sleep deprivation.

RUTEIJFRANZ What have the pilots to do during the 16 hours work period? Have they to fly the aircraft manually during this period or is it on automatic 4-14

pilot most of the time so that in effect they have rest cyc.Les during the 'work' period?

On the tests of double crew flying, the 'on-duty' crew had to redn at their stations for the full time onduty, either 16 hrs or 4 hrs. There is no doubt that at tines the pilobs were at minimum vigilance, and shifted the flying responsibility to the co-pilot. The 'on-duty' crew was not supposed to sleep, but lheir vigilance unquestionab:ly viaxed and wined during the 16 hr duty. 5

A SUBJECTIVE ASSESSMENT OF FATIGUE IN TRANSPORT

AIRCREM

Captain L.G. Innes* Canadian Forces bstitute of Environmental Medicine Toronto, Ontario

*The author waa prevented from presentillg: this paper orally, because of illness: Editcr. Two questionnaire studies were carried out on fatigue reactions of transport aircrew on transatlantic flights of approximately 12 hours duration. The first questionnaire assessed exhaustion fatigue due to the flight for all crew positions, and identified crewmembers having unusually high ratings. The second questionnaire study assessed nervous fatigue in the same type of operation, and again tu0 crew positions only were identified as being of concern. There was no relationship between fatigue ratings and sleep patterns, nor with easterly or westerly direction of flight. Analysis of the use of questionnaire items showed that frequency of check marks against "fatigue" statements did not correspond well with fatigue rating. From time to time accident investigators have disclosed fatigue as a contributing factor in aircraft accidents, and a survey carried out on 42 RCAF aircrewmembers involved in accidents, when fatigue was identified as a factor, showed that 43$ were on non-jet transport aircraft, accounting for more than. Jet fighters and jet trainer combined. But we have corroborating evidence for this problem in transport operations in the form of verbal reports by crewmembers of fatigue reactions after 12 to 14 hour transatlantic flights which they feel may impair their ability to maintain an adequate standard of performance. The approach of this investigation was not therefore to state that there was fatigue present which had to be quantified by some physiological or biochemical investigation. It was rather that fatigue was present as a self evaluation of inadequacy. As described by Bartley (1) it is regarding the total organism, not sub-systems or tissue within the organism. And as it is in this case a subjective self assessment of inadequacy it is not appropriate to look at performance changes to assess the degree of fatigue present.

When aircrewmembers report that they feel fatigued they are using the term fatigue as a summary of certain aspects of their current situation. It is a diagnosis, and it was the aim of this study to identify what they were using as a basis for the diagnosis. It cannot be assumed that similar operations in different types of aircraft will produce the same crew reactions, nor that all crewmembers in one type of aircraft will have the same degree of complaint. Also the schedule of the aircraft introduces the aspects of diet, or dietary indiscretions due to inconvenient take-off and landing times; exercise, which can be difficult to maintain routinely and can be unattractive as an interlude between flying missions; and rest, which is upset by time zone changes and may be difficult to coordinate with take-off schedules. The work-rest schedule for a particular crew position during flight can influence subjective reactions and may introduce problems by comparison with other crew positions. Also the relationship of number of days on duty to rest days between flights is an issue of some considerable interest. Wolf (7) analysed scores on descriptions of fatigue feelings which yielded three interpretable factors: nervous, drowsy, and exhaustion, which correspond to Bartley's (1) descriptions of disorganization after carrying out an intellectual task; boredom; and bodily discomfort after muscular activity. Since these can be viewed against a lou or high motivational state, while doing either a sedentary, intellectual, task, or a non sedentary, muscular task, the tasks involved in a multi-place transport aircraft could be expected to produce different types of reactions which may all be classified by the individuals involved as fatigue. EXHAUSTION FATIGUE STUDY

IO, naire scores so the larger the rating the greater the change in self evaluation during the flight. The A PX. ratings for the passenger flights are relatively the same for all crewmembers except for the pilot and copilot who record a smaller increase for the transatlantic flight. Ratings for the cargo flights are a- 4- 'VI more varied between crewmembers. ranging from 4.0 0 for the Radio Officer to 8.7 for the Flight Engineer 2- and 9 for the Navigator. These values are averages c 2- *--- Hercules for the eastbound and westbound flights, and when -Yukon these are plotted separately it is seen that the 5-2

after either one or two days stopover. Physiologically they would be closer to the Canadian time of 0600 hours, producing a law point in the diurnal cycle at take off time in the middle of the day.

-Canada - Europe --- Europe - Canada

12 -

10 -

'1''YUKON HERCULES

01: 1 Capt Coplt Nav RO FE Ldmtr Capt Coplt Nav RO FE Ldmtr

Exhaustion fatigue ratings: Canada/Europe - Europe/Canatla comparisons Fig. 2

Cargo flights shuw a reverse trend, with slightly higher ratings on the eastbound flight to Europe. These leave eastbound at 1000 hours arriving in hbrope at 2400 hours, or 0600 local, with one or two stopovers en route. The return flight is continuous to Canada with two stopovers locally before the final -destination, lasting from 0730 hours to 2000 hours Canadian time. In terms of crew positions, the Navigators and Flight Engineers on cargo flights seems to have the greatest consistent amount of complaint, while the Loadmasters on the passenger flights seem to wilt. especially with passengers leaving Canada. The pilots do not appear to be a matter of concern on this type of complaint. TABU I

FEELING TONE CHECKLIST (A)

NO. Better than Same as Worse than Statement 1 0 0 0 Slightly tired 3 2 0 0 0 Like 1%bursting with energy 2' 3 0 0 0 Extremely tired 4 4 0 0 0 Quite fresh 1

5 0 0 0 Slightly pooped 3 6 0 0 0 Extremely peppy 2 7 0 0 0 Somewhat fresh 1 8 0 0 0 Petered out 4

9 0 0 0 Very refreshed 3 10 0 0 0 Ready to drop 4 11 0 0 0 Fairly well pooped 3 12 0 0 0 Verj lively 2 U 0 0 0 Very tired 4

Have you checked each statement? LEG FROM -TO SUBJECT 5-3

18 - -YUKON In: 56) 17.5 to 9.5, compared to the present figures of 16.2 .*-...-*.-HERCULES 1 n: 42) to 9.5 after 12 hours flying.

2 14 A study of BOAC Boeing 707 captains on transatlantic flights was carried out by a team from the British Ministry of Aviation and the Royal Air Force (3). 00,5 1012 *.. The fatigue checklist used was the shorter 10-item :4c.c form suggested by Pearson and Byars (6) with a 8- modification in the scoring procedure. The results

-'same as'. mild fatigue loo90 1 .O.U**OW- 'same as' high fatigue ---'worse than' mild satisfaction -*-*-'worse than' mild fatigue

--e- 'worse Ihen' high fatigue

Pre In Post Pr e In Post Analysis of types of statements : Yukon Fig. 4 5-4

The use of the stronger statements, such as "same as" high fatigue, or "worse than" both mild and high fatigue are only used after the flight, and then only to a small extent.

100 -

90 - I -'same ab' mild fatigue ao - 1 .mbbb.brb. 'same as' high fatigue / --e 'worse than' mtld satisfaction 70 - E / -a-.- 'worse than' mild fatigue 60 - 'worse than' high fatigue in inP) '0 50 - !? 40 - -0 S 30 -

20 -

10 -

-10 ' , I I I 17 Pre In Post Pre In Post Analysis of types of statements: Hercules Fig. 5

The frequency of use of the 4 different types of statements by cargo crews is almost identical to the Yukon crew pattern (Fig. 5). The maSn difference is in the even wider gap between their willingness to say that they feel the same as mild fatigue statements as opposed to saying they feel worse than mild satisfaction, The Hercules post flight usage shows that of all the mild fatigue statements responded to, 56% were classified as the same as. compared with 63 for Yukon crews, while mild satisfaction statements received 93% "worse than" responses from Hercules crews and 85s from the Yukon crews. This suggests that the fatigue statements in this checklist reflect the feelings of Hercules crewmembers even less than they do the feelings of their Yukon counterparts.

SLEEP BF&UVIOR. The number of hours sleep obtained prior to the flight, and the number of hours since that period of sleep prior to take-off were recorded for each flight. When these were correlated with the fatigue ratings obtained on the Exhaustion Fatigue Checklist, the values wern found to be non- significant for Yukon crews, for Hercules crews, and for all assessments totalled. There is therefore no identifiable relationship between sleep patterns as voluntarily reported and the self-ratings of fatigue.

NERVOUS FATIGUE STUDY

A fatigue checklist was developed in the same format as the exhaustion fatigue checklist. but incorporating statements which reflect more the concept of nervous fatigue as isolated by Wolf (7) in his factor analytic study. This questionnaire was administered prior to take-off, during the flight after about 5 hours, and again after landing. Again the crewman was required to state whether he assessed himself as better than, the same as, or worse than the statements before him. The assessments were made on Cl3O cargo flights on the transatlantic run, but the Yukon flights used in this study were long range training flights which included eleven legs of approximntely 10 hours duration. NEXVOUS FATIGUE RATING BY CREW POSITION: CUO. The cargo flight ratings were extremely low for the officer crewmembers, ranging from -2 to 2.2, suggesting that nervous fatigue as described by the checklist statements is not a problem to these crew positions. There was a sharp rise in self ratings for the other two positions, that of the Flight Engineers and Loadmasters, whose mean ratings were 7.7 and 13.2 respectively.

When these are broken down by eastbound and westbound flights it is evident that the more extreme values are recorded on the eastbound trip to Europe. The figure for the RO is not very reliable since only one flight carried this crewman. so these values.are based on one individual only. The extremely high rating from the Loadmasters is largely due to the eastbound flight rating of 19 compared with 7.3 for the westbound rating. 5 -5

COMPARISON WITH EXHAUSTION FATIGUE SURVEY: c130. The general rating level reported by Cl30 crewmembers on the exhaustion fatigue questionnaire was between 6 alad 9. with a rather high variability between crew positions. The nervous fatigue ratings for the same 2o16 1 type of flight in the same type of aircraft are generally between -2 and +2 suggesting that this type of reaction is lower for the crew as a whole. The high exhaustion ratings were recorded by the Navigators and Flight Engineers while high nervous fatigue ratings are Froduced by the Loadmasters and Fllght Engineers. In both surveys the Radio Officer

-7 reported very low ratings, showing an absence of Capt Copll Nav RO FE Ldmtr both exhaustion and nervous fatigue reactions. Gn Nervous fatigue ratings for Hercules transatlantic flight eastbound and westbound comparisons only the Flight Fig. 6 Engineers have higher exhaustion fatigue westbound, and only the Loadmasters recorded a large increase in nervous fatigue on the eastbound trip.

It seems thersfore that there is a strong -Canada. Europe indication of the Flight Engineer position in the -..-..-UEurope - Canada Cl3O being conducive to feelings of physical weariness *O16 1 / and of nervous tension, in relation to the rest of the crew. The Navigator's task seems to produce a high degree of physical tiredness, but without an unusually high degree of emotional upset accompawing it. The Loadmasters' duties are such that, by their own self-assessments, they are willing to say they are tired by the duties of a flight, but that nervous fatigue is their main problem. 1, Capt Coplt Nav RO FE Ldmtr NERYOUS FATIGUE RATING BY CREW POSITION: YUKON. Average fatigue ratings for crew positions shown Nervous fatigue ratings: Hercules eastbound-westbound that four of the crew have ratings between 3.0 and Fig- 7 3.7. while the Copilot rates only 0.8 and the Loadmaster only 0.3. Nervous fatigue as described by the questionnaire statements is of no concern to these two CPeWmen, and does not appear to be a problem of any magnitude to the remainder of the crew in this type of operation. COMPARISON WITH EXHAUSTION FATIGUE WRVEY: YUKON. The different types of flights used in the two surveys makes any direct comparison difficult, mainly due to the difference in motivation levels one would expect from a routine schedule transatlantic flight as opposed to a once-only round-the-world training flight. It is hypothesised that the main effect of the latter would bo to increase feelings of well being prior to a flight, but that the effects of carrying out the required flying duties for approximately 10 Cap1 Coplt Nav RO FE Ldmtr hours in the air would be somewhat similar. Nervous fatigue ratings for Yukon flight The range of exhaustion fatigue ratings for Fig. 8 transatlantic Yukon crews was approximately 4 to 7, with the Captains and Copilots scoring low compared to the rest of the crew. The range of nervous fatigue ratings is from about -1 to 4, with the Copilots and Loadmasters scoring lower than the rest. The pattern of no serious divergencies above the crew average holds in both surveys however, with a suggestion that the Captain has a higher nervous fatigue state on the non-scheduled type of flight, and the Loadmaster t;as more of this reaction on the regular scheduled flights than on the round-the-world trip. ANALYSIS OF TYPES OF STATEMENTS. Each of the 25 items in the checklist was categorized into one of four groups: 0 (1) mild statements of lack of fatigue (2) strong statements of lack of fatigue (3) mild statements of feelings of fatigue (4) strong statements of feelings of fatigue The items are numbered according to this classification in the sample in Table 11.

The use of mild and high fatigue statements, either as "same as'' or "worse than" should be a measure of feelings of nervous fatigue at that stage of the flight. Figure 9 shows the frequency of use of different types of responses to the 4 classes of items,given as a percentage of the total number of 5-6

TABLE I1 FEELING TONE CHECKLIST (B)

No. Better than Same as Worse than Statement

1. 0 0 0 Quit relaxed 1 2. 0 0 0 ' Extremely tense 4 3. 0 0 0 Quite strained 3 4. 0 0 0 Slightly tense 3 5. 0 0 0 Extremely relaxed 2

~~~~ ~ 6. 0 0 0 Very jumpy 4 7. 0 0 0 Quite composed 1 8. 0 0 0 A bundle of nerves 4 9. 0 0 0 Slightly jittery 3 10. 0 0 0 A little calmer than usual 2

11. 0 0 (1. Very coolheaded 12. 0 0 0 Too keyed up U 0 0 0 Extremely unruffled 14. 0 0 0 Pretty edgy 15 0 0 0 Not too composed 16. 0 0 0 Extremely irritable 4 17 * 0 0 0 No more cranky than u,md 1 18. 0 0 0 In very good humor 2 19 0 0 0 Somewhat touchy 3 20. 0 0 0 Quite even-tempered 1

21. 0 0 0 A bit oversensitive 22. 0 0 0 Very snappish 23 0 0 0 Extremely sociable 24. 0 0 0 Slightly quarrelsome 25 0 0 0 Quite amiable

Have you chocked each statement?

UGFROM TO

SUBJECT

that class of item, for transatlantic and all flights separately. There is a considerable increase through the course of the Hercules flights in the "same as" rating for mild fatigue items, rising from 11.5% pre-flight, to 15.3% in-flight, to 23.5%post-flight. There was a lover frequency of "worse than" ratings to mild satisfaction items, ranging from 6% pre-flight to 14.8% postflight. In contrast Hercules crews rated themselves on the exhaustion fatigue checklist as the "same as" mild fatigue on U.4$ of the items pre-flight, 39.5% in-fll ht. and 55.9% post-flight, and "worse than" mild satisfaction on 10.55 pre-flight, 52.68 in-flight, and 92.2% postflight. Therefore, apart from the difference in amount of use, there is a greater villingness to describe themselves as the same ao the nervous items than there was for exhaustion items. fn relation to the use of worse than mild satisfaction. The same holds txue for Yukon non- scheduled flights, although the actual percentage use is very low.

The pattern for Hercules crews is to increase their self assessments of being worse than mild satisfaction by the half-way stage of the fiiight, such as "worse than quite relaxed", but prefer to . assess themselves as being the same as mild fatigue at the post-flight assessment. The use of "same as" or "worse thann responses to the more serious fatigue statements such as "extremely irritable". is very limited. being reserved for&ost-flight assessments in most cases (Fig. 9). When the figures are examined in detail it is found that, of the number of "same as" responses to mild fatigue statements, 41 of the 143 from Hercules crewmembers were given by the Navigators, or approximately 29% from 1 of the 6 crew positions. For Yukon flights the number of mild and high discontent statements from Navigators and Flight Engineers was very high, producing 159 of 323 responses, or 49% from 2 of the 6 crew positions. One Navigator and one Flight Engineer on Yukon ilights were suffering from nervous fatigue to such a degree that they were completely uncooperative in completion of the checklists. 5-7

24 -'same as' mild fatigue 22 ---====- 'same as' high fatigue

20 .I,-- 'worse than' mild satisfaction ---=- 'worse than' mild fatigue 18 **.-.=- 'worse than' high fatigue

9) 14

C : 12 -0 10 % 68 / P 0. b: 0 a6- 0 s4

0 Pre In Post Pre In Post Pre In Post Pre In Post Transatlantic flight Total flight Transatlantic flight Total flight

Analysis of types of statements

Fig. 9

CONCLUSIONS

From an initial positLon of knowing only that reports of fatigue in long range transport aircraft crews had been submitted, we have managed to clarify the complaints to some degree. At a general level these questionnaire studies have shown that the feelings measured by the Exhaustion Fatigue Checklist are only mildly present after a transatlantic flight of 12 hours or more. The crew positions which produce this reaction more than for the crew as a whole were pinpointed. The reaction to the Nervous Fatigue Checklist on two different types of long range flying were extremely mild, but again specific crews positions could be identified which were considerably worse than the crew as a whole.

The checklists require further validation however due to the discrepancies evident between the fatigue rating for the flight, and the incidence of checks on strong fatigue statements. It would appear that the scoring procedure for computing the fatigue rating is too gross to reflect the expression of subjective reactions.

REFERENCES

1. BARTLEY, S.H. Fatigue: Mechanism and Management. Springfield: Thomas. 1965. 2. BARTLEY, S.H. and CHUTE, E. Fatigue and Impairment in Man. McGraw-Hill: N.Y. 1947. 3. HOWITT. J.S. A Preliminary Study of Flight Deck 'UJorkloads in Civil Air Transport Aircraft. FPRC 1240, Ministry of Defence, London. 1965.

4. INNS, L.G. Aspects of Fatigue in Aviation. Report 68-m-6, Canadian Forces Institute of Aviation Medicine, Toronto. 1968. 5. PEARSON, R.G. Task Proficiency and Feelings of Fatigue. Report 57-77, USAF School of Aviation Medicine, Texas. 1957.

6. PEARSON. R.G. and BURS. G.E. The Development and Validation of a Checklist for Measuring Subjective Fatigue. Report 56-115, USAF School of Aviation Medicine, Texas. 1957. 7. WOLF, G. Construct Validation of Measures of Three Kinds of Experiential Fatigue. Perc. Mot. Skills, 1967, 24:1067.

SIMULATED TIME-ZONE SHIFTS AND PERFORMANCE ABILITY: BEHAVIORAL,

ELECTROENCEPHALOGRAPHIC AND ENDOCRINE EFFECTS OF TRANSIENT

ALTERATIONS IN ENVIRONMENTAL PHASE.

Jan Berkhout, Ph.D. Space Biology Laboratory Brain Research Institute University of California Los Angeles, California 90024 6

SUMMARY

Three subjects were maintained on an experimental sleep- activity time-line which simulated a flight assignment crossing ten time-zones eastbound and return within 72 hours. The subjects were required to operate an automobile and an array of electronic equipment during the simulated flights. Sleep periods were assigned during the simulated local night, involving a ten hour translation of normal habits, and occasioning two 12 hour epochs of sleep deprivation. Including baseline and recovery periods, the subjects were studied continuously for nine days. Mental calculating ability, motor coordination and auditory perceptual acuity were determined several times per day throughout this period. Electroencephalograms were recorded during all assigned sleep periods and during the administration of behavioral tests. All urine produced during the experiment was collected, and volume, osmolarity, creatinine and 17-OHC levels were determined as a function of time-of-day. The EEG recordings provided useful monitoring of the subjects' transient arousal status, and permitted the resolution of observed behavioral deficits into sleep-induced, stress-induced and idiopathic classes. The urine chemistry determinations provided measures of circadian physiological fluctuations and their distortion following sleep-activity dislocations, and provided independent estimates of endocrine stress and energy expenditure. Behavioral capability was observed to depend on several factors, including baseline circadian phase, time-since- waking (an approximation of local circadian phase), endocrine stress and subjective fatigue. Conclusions will be drawn concerning the optimum scheduling of crew assignments on extensive trans-meridional f 1 ights. 6-1

SIMULATED TIME-ZONE SHIFTS AND PERFORMANCE ABILITY: BEHAVIORAL, ELECTROENCEPHALOGRAPHIC AND ENDOCRINE EFFECTS OF TRANSIENT ALTERATIONS IN ENVIRONMENTAL PHASE

1 NTRODUCT I ON The scheduling of crew assignments during extensive transmeridional flights requires a special application of the theories and observations concerning the circadian periodicity of physiological and psychological functions in human subjects, if performance deficits due to the disruption of these periodic functions are to be minimized. Physiological and behavioral periodicity in humans has been studied by maintaining a single external synchronizer under experimental control and observing the stability or distortion of periodicity in the parameters of interest, which are treated as dependent variables. In simulated studies of transmeridional travel, the experimental synchronizer is ordinarily an artificial light-dark cycle, and the parameters of interest (typically sleep-activity cycles, stress-related urine components, and psychomotor performance capabilities with known circadian components) are allowed to "run free" as the light-dark cycle is manipulated to simulate given shifts in longitude within given periods of time. Such free running parameters have been observed to alter their phase relationships with each other under this condition, and many days under stable conditions are needed to re-establish the original phase relationships (I). Such observations have been confirmed during actual transmeridional displacements by Klein fi (2) who observed clear circadian fluctuations in performance ability of experienced pilots tested on a super- sonic flight simulator. Following an actual displacement of 8 time-zones, the subjects' circadian performance fluctuations shifted in phase to match the new local time within five days. Several similar displacement studies using less pilot-oriented behavioral indicators have been reviewed by Siege1 et fi (3). These results are of principle applicability to essentially passive travelers, whose sleep-activity cycles are unrestricted, and may be allowed to resynchronize with other biological rhythms ad libitum during the extensive period of adjustment to the altered local time. Reports of behavioral capability during the actual effectuation of changes in phase, and for changes of brief duration, are not currently available. Since the sleep-activity cycles of active flight-crew members necessarily follow an organized schedule, studies applicable to such personnel must incorporate an experimental design in which both light-dark cycles and sleep-activity cycles are considered potential entrainers of biorhythms, and maintained under experimental control. Thus, two distinct synchronizers, whose phase relationships between themselves frequently change, are imposed on the subjects' physiological and behavioral abilities. In this situation the analysis of biological rhythms must include evaluations of the following possibilities: I. The dependent variables continue to follow home-based clock time, synchronized by a biological clock which is not effectively reset during the term of the experiment. 2. The dependent variables follow the experimental light-dark cycle, equivalent to transient local clock time. This cycle is necessarily non-circadian, and may include Iadaysi1of 12 to 36 hours. 3. The dependent variables follow the experimental sleep-activity cycle, or clock time calculated from sleep-onset, waking or work-onset. Of course, the dependent variables may be influenced by any or all of these external synchronizers, and rather complex patterns of numerical fluctuations can be generated by the sumation of these simultaneous, potentially entraining step-functions. Other considerations enter into this experimental design. The timing of the usual intercontinental flight mission does not permit the flight crew to get acclimatized to the time zone of their destination. Long before resynchronization to local time is complete, the crew will have returned to their home base. The return trip will cause additional desynchronosis stress in proportion to the adjustment the crew has made to the distant time zone. Performance both during and after the return flight may be severely affected if the timing of flights and layovers makes these effects cumulative. In addition, a strictly organized sleep-activity cycle which alters home-base habits can entail a certain amount of sleep deprivation. This is expressed within single cycles in hours-since-waking (HSW), where HSW excedes 16, and within longer epochs, or where brief sleep episodes occur, as the number of hours of cumulated sleep deficit within a given experimental regime. Biological variables may be correlated with either or both of these expressions of sleep deprivation. The present study involved a ten-hour dislocation and recovery in an artifically constrained sleep- activity cycle. The scheduling of sleep-activity dislocations was intended to maximize the cumulative stress of anomalous peaks in distorted endocrine activity rhythms. Constant monitoring of brain electrical activity (EEG) made it possible to specify the timing of sleep episodes with great precision, and to monitor alertness and fatigue patterns in the EEG as a function of cumulative endocrine and desynchronosis stress. The behavioral abilities tested included arithmetic calculating, auditory flutter fusion threshold and digital motor coordination. We were primarily interested in the relationships of endocrine, EEG and behavioral activity during the actual displacements of sleep-activity cycles. Our protocol involved a return to base local time within 72 hours of departure, and did not permit resynchronization of biorhythms to a new and stable zeitgeber. We tested behavioral abilities during two eight-hour automobile drives which simulated the trans-meridional displacements, and which required active participation of the subjects as drivers. The protocol was intended to simulate an active duty time-line for transmeridional aircrew service under worst-case turnaround conditions. METHODS Three subjects were maintained under experimental control from noon, Friday, July 18, to noon, Sunday, July 27, 1969. A log was kept of all food and liquid intake during these ten days. All urine excreted was collected and stored, comprising a total of 122 samples for the three subjects. A ten-hour phase shift in the subjects' sleep-activity cycle was established during July 23, 24, and 25. This shift followed four days of baseline monitoring of behavioral, EEG and endocrine activity. Baseline sleep-activity phase was restored during July 26 and 27. Eight 8-hour sleep periods were assigned during these days, resulting in a net sleep deficit of eight hours over the ten day experiment. Nonprogrammed napping reduced this deficit to about six hours for all subjects. Twenty-two behavioral test sessions were performed by each subject, incorporating auditory flutter fusion (AFF), digital tapping and abacus calculation tests. Subjects. The subjects were three 21 year old male college seniors (B, Q, and M) of unremarkable build and habits, and in good health at the time of entering the experiment. Subject Q had a history of surgery for a thyroid aneurism and haematoma, but had recovered normal 6-2

Excursion I E.c"r.,on iI TEST BATTERY rn rn .I I I .I 1 ADMINISTRATION rn I

0- SLEEP EPOCHS m Ix (STAGE U. m. lX 4ND REM ONSETS NOTED) - Meols

LOCALTIME,. I I I I , S. I I, I I I I I I I I I I I..IIIII...IIIII 12N 12M 12N 12M 12N 12M 12N 12M 12N 12M 12N 12M I2N 12M 12N 12M 12N Day1 I 2 I 3 I 4 I 5 I 6 I 7 I 8 19

Fig. 1

PATTERNS OF URIN4RY EXCRETION IN HUMAN DESYNCHRONOSIS STUDY

Fig. 2 6-3 thyroid function, was asymptomatic, and did not require medication. Subject B had recently recovered from a respiratory infection, and had completed a course of antibiotic therapy the day prior to the beginning of the experiment. All subjects refrained from coffee, tobacco and other drugs during the study. None were accustomed to these stimulants in private life. No medications, including aspirin, were used during the course of the experiment. A. Experimental activity profile. Sleep-activity cycles includinq meal times, assiqned sleep.. periods. vehicular excursions and behavioral test battery administrations are iniicated in Figure i. The subjects were maintained in a small suite with bath and kitchen facilities at the UCLA medical center in Los Angeles. The rooms could be made light-tight when desired. During baseline days, the quarters were open to natural light. During the interval between excursions I and II, when the subjects were nominally living on local time minus ten hours, the room was closed to natural illumination. During the nominal shifted day a relatively bright level of incandescent i 1 lumination was maintained (600 watts). During nominal shifted night a lower level of illumination was used (100 watts). During assigned sleep periods, only a dim night light (I5 watts) was kept burning. This artificial lighting regime is not considered an effective simulation of a solar light-dark cycle. Circadian changes in temperature and ambient noise levels could not be controlled. We do not consider our experimental protocol to be a realistic duplication of an actual geographical displacement, but rather an artificial alteration in the subjects' sleep-wake activity phase. The excursions indicated in Figure 1 took place in a 9-passenger station wagon equiped for behavioral testing and physiological recording. The subjects alternately drove the vehicle, administered the behavioral tests and operated the recording apparatus. The excursions covered several hundred miles of road in Southern California. There was no attempt made to simulate a gradual transition from local to shifted time, as would occur in a true geographic displacement. We felt that the imposition of genuinely stressful and demanding tasks and responsibilities during the excursions was desireable in this protocol, and this was not compatible with conducting the experimental excursions in isolation from the local environment. The nominal shifted environment was maintained only during the 48 hour period between the two excursions, and the subjects' sleep-activity cycles were often out of phase with both true local time and nominal shifted time. In this respect the experimental protocol closely corresponds with the experiences of active flight-crews on intercontinental missions. However, due to the incomplete simulation of the environmental phase shift, many potential environmental entrainers of biorhythms were anomalously maintained on local time throughout the experiment. B. Behavioral data. The behavioral tests incorporated into this study were based on tasks having a demonstrable circadian fluctuation in performance levels under stable environmental conditions. This insured that the tests would in fact monitor those phychological performance factors which are sensitive to disruption of circadian periodicity. Since the tests were given more than 20 times to each subject, they had to be relatively insensitive to practice effects, habituation of response levels, and stereotyped response patterns. A final constraint on these tasks was that the testing apparatus had to be portable and electrically self-contained. Three tests were used: Calculatinq ability. Exhaustive documentation of a stable circadian periodicity in instrument- reading and calculating ability has been provided by Bjerner, Holme and Swennson (4) in their study of a Swedish gas-works' log books. They identified the errors committed in reading an array of meters, transcribing the data onto log sheets and performing addition and multiplication on the resulting columns of figures. Datt was available for 61,296 entries spanning 41 years, with an even distribution of entries over all the hours of the day and night. A persistent error curve with a maximum at 0300 hours and a smaller peak at 1500 hours was observed to hold over all variations in personnel, season, temporal acclimatization of shift workers, and the total work load. To test this type of coding and calculating ability we utilized a modified six-row abacus on which the subjects added rows of five-digit numbers, transcribing subtotals onto paper. By magnetizing the abacus beads and inserting small coils into the rods on which they were suspended a DC pulse could be obtained whenever a bead was moved. These pulses were recorded on the same magnetic tape and paper charts as the simultaneously generated EEG activity OF the subjects. From these pulse trains, the rates of calculation within different problems could be determined and related to overall elapsed-time and error scores. Calculating ability and the individual's EEG could also be closely related in time. Auditory perceptual acuity. We excluded any tests of visual acuity because of the difficulties in maintaining equivalent ambient lighting conditions and subject dark-adaptation for the various circumstances in which the tests were to be given. An auditory flutter-fusion (AFF) test was selected, based on a neurophychological dianostic test originally developed by Chapman and Symmes (5). This test is analogous to the visual flicker-fusion determination. Although this test has not been previously used in circadian evaluations, we found it convenient to present and easily instrumented in a portable form. The results obtained demonstrated a clear circadian periodicity in subjective fusion thresholds, and also reflected the experimental distortions of environmental phase. Our version of the AFF test utilized the method of paired comparisons, the subjects being required to determine whether two bursts of sound were alike or different. Each burst consisted of a white noise envelope with a 90 percent On, IO percent Off duty cycle, the duration of each cycle ranging from 1/10 sec to 1/100 sec, consistent within each burst. Each burst lasted 1.5 sec, regardless of the flutter rate. One burst in each pair was fluttered at the 100 cps rate, which was above apparent fusion frequency at the sound levels used, while the other burst was fluttered at one of nine available lower rates. Each pair was in fact different, but the difference was not perceived if both flutter rates were above the fusion threshold. The stimuli were tape recorded and played back to the subjects using a battery powered tape unit and headphones. Each test consisted of 40 pairs of fluttered white noise bursts. Several formats of the test were used, each with a different sequence of flutter frequencies, to avoid developing stereotyped response patterns among the subjects. Coordinated motor ability. Klein (6) has demonstrated a circadian influence on absolute reaction time, and on performance of a complex sensory-motor task involving the matching of various sized balls and holes. Jansen (7) has found a similar circadian component in performance on a tracking task. We chose a tapping task, performed under time pressure, to test these abilities. The subjects were required 6-4

:,,I $ I, I I I,I !! ! SUBJECT B AFF TEST NO. 21 ;.--I. I- j 7-26-69 23:50 Hours I! j I Orowsy episode of four seconds 1 I I il i I i 4.2 L i\ I ij I I !I - 1

I,Il'l

'V -7- I

Fig. 3

PERCEPTUAL ABILITY AS A FUNCTION OF TIME AND'ACTIVITY CYCLES SUBJECT 0

111

P- / ,./ . -. '. / \/,* v) I I 0 I U

It12 HOURS SINCE WAKING LOCAL TIME - Bosallna day. - Shifted day- ___- recover^ days

Fig. 4 6-5 to operate a short lever attached to a counter as often as possible within ten seconds. Each tap produced a OC pulse, which was recorded. The parameters scored included total taps per IO seconds, rates of increase and decrease of performance within this period, and the comparative performance of dominant and non-dominant hands after brief periods of rest. C. Electroencephaloqraphic data. Continuous circadian fluctuations of several elements of the human EEG have been observed to be superimposed on the predominating daily alternations of sleep staging and wakefulness. lvanov et C (8) and Frank (9) have both noted a circadian component in spectral intensity within delta, theta, alpha and beta frequency bands. Othmer et fi (IO) have noted that rapid eye movement (REM) epochs occur during waking hours as well as during sleep, and appear to follow a recurrent circadian pattern in their appearance. However, no external entrainers are known to be intimately correlated with these events, their response to distortions of environmental phase has not been documented, and their influence on behavior remains obscure. Nevertheless, EEG recordings do provide an extremely useful adjunct to the study of environmental desynchronosis. The exact timing of the onsets of sleep and waking is fundamentally an electroencephalographic determination, and without this indicator it is very difficult to establish a precise sleep- wake cycle. The exact timing of deep sleep (EEG stages Ill and IV) and REM activity within a given sleep profile is particularly important, as these points i'n the sleep-wake cycle may be more influential entrainers of biorhythms than the actual moments of rising and retiring. While the EEG appears relatively insensitive to the initial stages of sleep deprivation,it is a sensitive indicator of the normal fluctuations of alertness within the ordinary waking day (11). Continuous monitoring of the EEG during behavioral testing permits discriminating between the several alternative physiological substrates of observed behavioral deficits. Such deficits may be due to a transient state of central nervous pathology, resulting from cumulative desynchronosis stresses, and appearing as transient pathological signs in the EEG (e.g., sharp waves, slow waves, amplitude asymetries or focal arhythmias). Behavioral disabilities may also accompany the infiltration of sleep activity into the ongoing EEG, or may occur idiopathically in the presence of normal and alert patterns of neuro- electrical activity. These three conditions can be reliably discriminated by visual examination of the gross EEG. If high-resolution spectral and cross-spectral analysis of the EEG is available, finer judgements of levels of alertness during behavioral tasks may be made, and EEG patterns discriminating good from poor performances may be determined. In the present study, four channels of EEG and an electro-oculogram were recorded continuously from all three subjects during their assigned rest periods. Four-stage plus REM sleep profiles were derived from these records with 15 minute resolution. Such critical points as the initial onset of deep sleep or REM epochs were determined to the nearest ten seconds. Eight channels of EEG were recorded from each subject during the sessions of psychomotor testing. These were visually evaluated for arousal levels and transient pathology. This data was recorded on tape, as well as on paper charts, and a detailed spectral pattern analysis is currently in progress for selected epochs of psychomotor activity. 0. Renal parameters. Our evaluation of circadian rhythms in biochemical processes was based entirely on constitutents of urine. The subjects were instructed to void their urine directly into 500 cc sample containers previously charged with 5 cc HCL. The time of sample collection was determined to the minute. The specimens were refrigerated within eight hours, and subsequently frozen. All urine voided during the experiment was collected and, as all food and liquid intake was monitored, urine volume could be expressed as a function of both time and total fluid through-put. In addition to total volume and osmolarity, we determined the output of creatinine, 17-hydroxycorticosteroids (I7-OHC) and phosphorous as a function of time. These three parameters are known to have a strong circadian periodicity in normal subjects maintained on stable sleep-activity regimes. This array of parameters wa5 chosen to reflect transient emotional stress, metabolic workload and fatigue, as well as deformations in sleep-activity periodicity. Volume and osmolarity. These measures reflect recent sleep and fluid-ingestion habits very closely, dnd provide an independent indicator of the extent to which our experimental protocol achieved an effective distortion of the subjects' physiological environment. Persistent circadian rhythms are not usually seen in these parameters when sleep-activity cycles are effectively altered. Creatinine. The output of this metabolic product exhibits a strong circadian component which resists change for weeks following shifts in environmental phase. Fluctuations of creatinine output are frequently out of phase with short term changes in sleep-activity cycles. This parameter also reflects overall physiological health and well being, and the antecedent physical work load, these components being superimposed on the fundamental circadian fluctuation. The total volume of creatinine excretion should be nearly constant from day to day. Output is lowest at night and highest during the most active portions of the waking day (12). 17-OHC. This endocrine parameter reflects pituitary-adrenal-cortical activity. Output fluctuations are strongly circadian, with a minimum level at night and a period peak output during early waking hours. The rise to peak levels and initial decline is rapid, but there is a gradual further decline throughout afternoon and evening. Both physical and psychological stressors result in increased output, and the parameter is specifically sensitive to the stress of sleep deprivation. Circadian patterns are maintained after changes in environmental phase, but are not as persistent as creatinine rhythms (9, 13). Phosphorus. The individual-specific oscillations of phosphate excretion reflect the operational effect of environmental phase shifts in areas specifically implicated in metabolic processes, and follow imposed phase changes very closely. This parameter is sensitive to transient stress episodes in a manner correlated with adrenocortical activity, but does not share the persistent circadian rhythm of 17-OHC output. Phosphate excretion also follows changes in diet and other personal habits affecting metabolism (13) RESULTS The three subjects endured the ten day experimental period with no serious deficits in their medical or psychological well being. Although they had some difficulty in sleeping comfortably while wearing EEG electrodes, they had adjusted to this by the fourth sleep period, and were obtaining a normal amount of sleep, with few interruptions, by that time. They performed well during the automobile excursions, experiencing no difficulty in coping with several unplanned emergencies which occurred despite considerable 6-6

sleep deprivation. The subjects ate and drank normally during the session, and had no complaints of transient physical discomfort, apart from drowsiness and occasional mild irritability associated with fatigue. Their eating and drinking habits were noted, and appear schematically in Figures 1 and 2. A. Renal data. The fluctuation of renal parameters during the experiment is graphed in Figure 2, for each individual subject. Urine volume, subject B: Urine volume per urination (UV/U) showed the usual peak at waking which followed all time shifts of the scheduled sleep periods. When corrected for inter-urination intervals (volume per hour, or UV/H), a persistent circadian rhythm of urine formation in the hladder was seen, peaking ax 1800 hours, which was maintained throughout the experimental period, despite sleep-activity shifts. Subject M: UV/U was similar to subject B. UV/ti was erratic, with a large peak following the second post-shift sleep period. This is interpreted as a stress-related epi'sode of diuresis. Subject Q: UV/U and UV/H were both erratic, with no persistent rhythms. There were small episodes of diuresis following both driving excursions and the second post-shift sleep period. Creatinine, subjects B and M: Both subjects displayed peaks of creatinine excretion shortly after rising which followed all phase shifts of sleep-activity cycles. Superimposed on this were smaller peaks correlated with driving excursions and transient work load. No marked circadian persistence appeared. Subject B required 48 hours to adapt to the first shift, with a progressive displacement of attenuated peaks, and returned to base-line synchrony after the return shift with no lag. Subject M adapted to both shifts with no lag, but with some aberrations of wave form during recovery, possibly associated with brief cat-naps (noted on Figure 2; UV/H panel). Subject Q: A completely persistent circadian rhythm of creatinine excretion appeared in this subject, unaffected by the experimental procedures. 17-OHC. Subjects B and M: These subjects had a peak output of 17-OHC during early waking hours which closely followed the alterations of sleep-activity cycles. Subject B displayed a stable base-line circadian pattern, which was abruptly phase shifted during transition periods. Subject M had a less stable base-line pattern, and displayed erratic oscillations of output during transition periods. Subject B showed a remarkable peak of 17-OHC output immediately after the second driving excursion, superimposed on the rhythms described above. 17-OHC and creatinine output are strongly correlated for these two subjects. Subject Q: No organized rhythm of 17-OHC excretion appeared, although small peaks were usually present at rising time and after excursions. 17-OHC output for this subject was dissociated from his strongly persistent creatinine output cycle noted above. Phosphorous. Subjects B and M: Strongly circadian baseline fluctuations were established in the first four days, with peaks upon arising and minimum levels in the late afternoon. This pattern followed the experimental activity phase shifts exactly. and was resynchronized with baseline phase at the end of the first return-shift sleep period. Subiect Q: This subject showed the same general pattern of fluctuations, but with smaller amplitude and with greater persistence. The phase shifts were completed within thirty-six hours for this subject, although they were completed with no discernible lag for subjects B end M. Summary: Endocrine activity for subjects B and M was distinctly different from activity of subject Q. Creatinine, 17-OHC and phosphorous excretions of B and M were all strongly circadian. All followed the ten-hour experimental phase shift and return with little discernible lag and only slight oscillations and aberrations of wave form. Work- and stress-related peaks were cleerly superimposed on these patterns. The only rhythm persisting unchanged was the rate of urine formation in the bladder of subject B. Subject Q showed a pattern of circadian variations much more resistant to change. Creatinine excretion did not reflect changed sleep-activity cycles at all, and phosphorous excretion changed comparatively slowly, within a low and narrow range of values. 17-OHC was chaotic, again within a comparatively low and narrow range of variation. We concluded that subjects B and M were remarkably adaptable to the experimental conditions, and their physiological rhythms responded immediately to both the altered sleep-activity schedule, ar,d to the occasional added stress and work loads. Subject Q was much less responsive to external stress and work loads, and showed greater stability of circadian endocrine activity. The observed phase-shifts in endocrine output for subjects B and M were completed with much greater rapidity than the literature suggests is normal, particularly in the case of creatinine (12). The persistent rhythms reportedly maintained in the face of environmental phase shifts are based on passive reactions to light-dark cycle fluctuations, and not on alterations in the subject's complete sleep- activity time-line. We feel that the imposition of assigned bed rest and.stressfu1 activity periods during both the shifted periods and returns served to resynchronize these cycles to the nominal light-dark patterns much more rapidly than would have been the case if the subjects were passive and slept libitum. These rapid shifts in endocrine output were provoked by an incomplete laboratory simulation of longitudinal displacement, in which some sensory evidence of true local time was always available to the subjects, and the shifts would have presumably been even more rapid and complete under conditions of actual geographical displacement. It is worth noting that fluctuations in endocrine output during transition periods were usually of lower amplitude than base line circadian variations, and peaks appearing at anomalous times were never as high as those appearing at the habitual times on either base-line or shifted days. B. Electroencephaloqraphic data. EEGs were scored for sleep staging during all'assigned rest periods. The subjects displayed similar overall sleep habits. In novel and uncomfortable surroundings, sleeping with unfamiliar companions and machinery while wearing EEG electrodes, the three subjects slept pocrly for the first two periods, never achieving continuous episodes of stage IV sleep, or clear REM periods with reportable dreams. During sleep periods 3 and 4 a more normal sleep profile was obtained, with the subjects achieving deep sleep at various points in the first 4 hours of the period and occasional REM periods in the two hours before waking. Periods 5 and 6 were on shifted time. The subjects were sleep deprived and fatigued entering period 5, which took place between 10 am and 6 pm of their normal waking day. The subjects again slept fitfully, and again showed no evidence of continuous episodes of deep sleep or of REM periods. Periods 7 and 8 were again at local night and followed a further period of sleep deprivation and fatigue. All 6-7 three subjects imnediately fell into deep sleep upon being permitted to retire, and had numerous episodes of REM sleep during the last four hours of the period. This pattern was duplicated on both nights. Our subjects were stressed considerably beyond our intentions by the poor sleep patterns they experienced during the early nights of the experiment, and during the two, daytime sleep periods. Considering recurrent constrained bed-rest periods as an independent zeitgeber, the crucial point in the period would appear to be the time of awakening. Our least persistant endocrine rhythms were all closely correlated with times of waking, rather than with the moment of entering bed, or the occurrence of stage IV sleep and REM episodes. EEG recordings made concurrently with behavioral tests showed normal, alert, alpha-blocked patterns during most sessions, including best ?nd worst performances. On the basis of these recordings, we excluded any possibility of the observed performance deficits being associated with transient central nervous pathology. Even during poor performances, the subjects' EEGs showed a normally responsive organization of alpha activity, and an absence of patterns associated with severe psychological or endocrine stress. Those circadian fluctuations in performance ability which were observed took place in a context of normal organization of cortical electrical activity. However, during periods of immediate (not cumulative) sleep deprivation, with HSW above 16, some brief EEG signs of drowsiness and fatigue appeared, usually of 2 to 5 seconds duration, and never leading to continuous stage I sleep. While these infiltrations of light drowsiness during test sessions were not necessarily associated with the poorest overall performances, they did often coincide with single errors. Figure 3 illustrates such an occurrence of brief drowsiness during a section of the AFF test, coinciding with a scored error. C. Behavioral data. The auditory flutter fusion test (AFF) produced a clearly circadian distribution of results in 2 of our 3 subjects. Figure 4, A-D, illustrates the distribution of error scores for subject Q, who had the most persistent endocrine rhythms. The results are plotted on several different horizontal axes, each emphasizing a different aspect of the data. Plotted on true local time (4A), the data shows a definite circadian performance factor, with a peak of perceptual acuity at 1000 to 1400 hours and maximum error scores at 0400 to 0600 hours, with a smaller error plateau between 1900 and 2400 hours. Plotted as a function of hours since waking (k), the same data illustrates a definite trend to lower error scores in the first twelve hours, declining most steeply in the first four hours. A gradual rise in error scores is seen as HSW excedes 16, entering the area of sleep deprivation. These HSW curves are plotted separately for the baseline days, shifted days and recovery days, which illustrates the common trends, despite the improvement factor clearly present in this data (46). Five test scores determined during sleep deprivation were excerpted and plotted against true local time (40). This distribution emphasized the circadian trends of the average curve in Fig. 4A. This subject appears to have maintained a fairly steady circadian pattern of perceptual acuity, which was generally time-locked to time-of-waking during sleep-activity shifts, but reverted under the influence of true local time during periods of sleep deprivation. Subject B showed similar AFF error distributions, though with less marked circadian base-line fluctuations. This subject also displayed a continuing improvement in perceptual acuity during the first few hours after waking. This trend followed all shifts in the timing of assigned sleep periods. Subject B was unaffected by sleep deprivation but his performances,although very good, did display the base-line circadian pattern of fluctuations, optimum performance occurring at 1600 hours true local time. Mental calculatinq ability proved to be generally correlated with true local time for all 3 subjects, with best performances (as measured by time scores) occurring on a broad plateau between 0900 and 1500 hours. Poor performances were clustered at 0400 to 0800 hours, with a slight tendency to poor performance between 1500 and 1800 hours noted for subject Q. These fluctuations were not resynchronized to shifted sleep-activity phases, and this ability was not diminished by sleep deprivation. Improvements due to practice effects continued across all shifts in sleep-activity phase. These results agree with the literature (4) on circadian rhythms in calculating ability. Lever tappinq (motor coordination). For subject B, this ability was persistently synchronized with local time, did not reflect hours-since-waking intervals, and was not impaired during sleep deprivation. As with auditory perceptual acuity, and in contrast to calculating ability, the stress of sleep deprivation served to emphasize circadian fluctuations based on true local time. Tapping ability was greatest in the early afternoon (1600 to 1900 hours) and poorest in the early morning (0500 to 1000 hours). Subject M produced a remarkably steep and persistent improvement with practice which obscurred most other influences. No effect of sleep deprivation was observed. Subject Q displayed neither circadian nor practice effects on this task, and little variation of any kind in his stereotyped and stable behavior. It is difficult to discern any correlation between behavioral and endocrine output for these subjects. Neither stress-related peaks of endocrine output nor anomalous output peaks during phase shifts could be associated with particularly poor test results. At the moment, we have no evidence concerning the physiological substrates of behavior which are responsible for circadian fluctuations in performance ability. We noted anecdotally that the subjects' psychological perception of imposed time, true time and debilitating fatigue fluctuated rapidly in response to social stimuli. Such fluctuations seem independent of the longer term changes in endocrine output by which the physiological effects of environmental time shifts are estimated. 0 I SCUSS I ON AN0 SUMMARY We observed that endocrine patterns and sleep profiles do follow a IO hour dislocation and return of imposed environmental phase completed within 72 hours. Nevertheless, circadian fluctuations of certain behavioral abilities, particularly numerical calculating skill, remained influenced by true local time during this brief interval. This influence was most prominent in the one subject with particularly. persistent endocrine rhythms, but was also observed to a lesser extent in the two subjects whose endocrine output was completely resynchronized with experimental shifted time. Behavioral performance correlations with true local time were strongest during periods of sleep deprivation, defined as hours-since-waking exceding 16. Cumulative sleep deficits over a 3 or 4 day period were of little significance compared to HSW figures. The desynchronizing and resynchronizing of endocrine rhythms within this brief period did not entail 6-a

any significant increase in the cumulative output of IT-OHC, and the range of (circadian fluctuation for 17-OHC was attenuated rather than exaggerated during the nominally stressful periods of transition. Sleep deprivation confirmed by episodes of drowsiness monitored in EEG tracings, appeared to be responsible for the limited degredation of performance capability which was observed. Sleep deprivation caused this performance capability to vary according to true local time even in subjects whose endocrine activity was resynchronized to a shifted pattern of environmental phase. Both endocrine and behavioral activity were more closely correlated with times of arising from bed than with other salient points in the sleep profile, including entering bed, stage IV sleep onset, or the onset of REM periods. Sleep deprivation may have sensitized the subjects' awareness of true local time, despite our attempts to simulate a time shift, or may have exaggerated persistent circadian rhythms that had not yet resynchronized to the shifted environmental phase, despite the apparent rapid resynchronization of endocrine rhythms. This issue can only be resolved by experiments incorporating actual geographical displacements. In either case, we suggest that aircrew scheduling should be aimed at achieving the stablest possible sleep-activity cycles and avoid sleep deprivation. At present, reconciliation of crew activity cycles with ephemeral local time would seem to be less important than maintaining stable sleep habits. While this may not be possible outside the context of a synchronous social environment, our data suggests that such a social setting can be constituted with as few as three individuals. REFERENCES- - .~ 1. Aschoff, Jurgen. Desynchronization and resynchronization of human circadian rhythms. Aerospace Medicine, 1969, 40(8): 844-849. 2. Klein, K.E., H. Bruner, H. Holtman,, H. Rehme, J. Stolze, W.D. Steinhoff and H.M. Wegmann. Circadian rhythm of pilots' efficiency and effects of multiple time zone travel. Aerospace Medicine, 1970, 41: 125-132. 3. Siegel, P.V., S.J. Gerathewohl and S.R. Mohler. Time-zone effects. Science, 1969, 164: 1249-1255. 4. Bjerner, B., A. Holm and A. Swensson. Diurnal variation in mental performance. U. J. M. w., 1955, 12: 103-110. 5. Chapman, L., D. Symmes, and W.C. Halstead. Auditory flutter fusion in patients with cortical ablations. J. Comp. Physiol. Psychol., 1955, 48: 421-425. 6. Klein, K.E., H.M. Wegmann and H. Bruner. Circadian rhythm in indices of human performance physical fitness and stress resistence. Aerospace Medicine, 1968, 39: 572-578. 7. Jansen, G., J. Rutenfranz and H. Singer. Uber eine circadiane Rhythmik sensumotorischer Leistungen. -Int. I. Angew. Physiol., 1966, 22: 65-83. 8. Ivanov, D.I., V.B. Malkin, V.L. Popkov, Ye.0. Popova and I.N. Chernyakov. Automatic analysis of diurnal periodic changes in human electroencephalogram. Problems of Space Bioloqy, 1965, 4: 609-612. 9. Frank G., F. Halberg, R. Harner, J. Matthews, E. Johnson, H. Gravem and V. Andrus. Circadian periodicity, adrenal corticosteriods, sleep deprivation and the EEG in normal men. d. Psychiatric E.,1966, 4: 73-86. IO. Othmer, E., M.P. Hayden and R. Segelbaum. Encephalic cycles during sleep and wakefulness in humans: a 24-hour pattern. Science, 1969, 164: 447-449. 11. Naitoh, P., A. Kales, E.J. Kollar, J.C. Smith and A. Jacobson. EEG activity after prolonged sleep loss. Electroenceph. clin. Neuro h siol., 1969, 27: 2-11. 12. Hawks, S. Physioloqicmhee, pp. 1235. 13. Mills, J.N. .Human circadian rhythms. Physioloqical Revues, 1966, 46: 128-171. CAPTlONS .. .- Figure I. Experimental activity profile. Figure 2. Renal outputs of subjects B. M and Q, plotted individually. Figure 3. EEG tracing illustrating sporadic drowsiness during auditory perception test. Figure 4. Auditory flutter-fusion error scores for subject Q. Lower scores indicate better perceptual acu i ty.

The author acknowledges the generous technical and medical assistance of Dr. John Hanley of the UCLA Neuropsychiatric Institute, and the work of Mrs. Irene Sabbot, UCLA Space Biology Laboratory, who supervised the biochemical analyses of the urine specimins.

This investigation was supported by the AF Office of Scientific Research of the Office of Aerospace Research, under Contract AF49!638) -1387. DISCUSSION: PAZX OF '3R BEKHOUT

PFESTON I nas interested in your wine peak volur'ies and an reininded that the volum or' urine is a problem in clircrevr of civil transports both on eastvrard and westward bound fi-ights. They tell mc that one of their biggest problems is not in getting ofi to sleep, but that their sleep is disturbed by tiie need to micturate. Once thus awoken they have difliculty in going to sleep again. Similarly sleep imy be disturbed by the untimely call of an established bowel rhythm.

BEXKHOUT lib impression is that the volume of urine per urination has a strong cyclical shift, yet the rate of formation of urine in the bladder is relatively constant. On considering the Zeitgeber for this aspect excretory function the resul-ts sugzest that it is the time of wakeniw and getting out of bed, that is of prfinary imnportiince, rather than the time at which the subjects went to bed.

WHITESIDE The presence of Zeitgeber is good or bad according to vihat you are trying to do. A Zeitgeber is not required if one is trying to maintain an established circadian rhythm in a different time zone, but is required if a new rhythm is being established.

One real problem is that of the short haul operator vrho has to sleep at home during the day in order to make an eveniw [light. In this respect your experiments were realistic, for Zeitgebers were still present and created an environment similar to that experienced by operational people working a shift system.

BERKHOUT One obssmration concerning the scheduling of the civilian crew is that the closer they can be kept to home base time the better their operationdl ability. One solution to this problem may be that at each major airport there should be a lounge kept at the crews' home base time. In the absence of external Zeitgebers a transit crew should be able to have adequate rest wi.thout disturbance of their home base circadian rhythm.

NICHOLSON 'Ilouldn't you need a lot of lOUn(pi~?

BERKKOUT This is a big problem and I do not pretend it can be solved cheaply. But each time-zone lounge could cover several hours - perhaps 4 louxes ~!ouldbe Sufiic ient . WEVrn In urine excretion, only the absolute rate of excretion and not the concentration is relevant with regarci to circedian rhythms. In ,all your slides (with one exception) volume per urine sample, or concentrations was shovrn. As is well established, these measures are determined by arbitrary work-rest schedules and therefore ore not relevant with regard to circadian rhythms. The only slide in which volume per hour was demonstrated seemed to indicate a persistent 24 hr rhythm. Have you calculated the excretion of electrolytes and other substances in this manner?

A necessary prerequisite of simulated time-zone nhift experisents is that all Zeitgebers related to local time are excluded, otherwise, the experimental situation will correspond to shift work.

BERKHOUT No, we have not calculated excretion per hour. I will do this and let you see the results.

INFLUENCE OF DUTY HOURS ON SLEEP PA!RXWS IN AIRCFW OPERATING IN THE MNG HAUL TRANSPORT ROLE. A STUDY OF SINGLE CWOPERATIONS AND DOUBLE CREW CONTINUOUS FLYING OPERATIONS

Squadron LeaderA. N. Nicholson, RAF Royal Air Force Institute of Aviation Medicine, Farnborough, Hampshire, United Kingdom. 7

SUMMARY

Military aircrew operating in the strategic long haul role experience repeated time zone changes and irregular and often long hours of duty. A satisfactory sleep pattern is of prime importance in maintaining their well-being and operational efficiency.

The normal regular nightly period of sleep during non-flying duty at base is replaced by a complex sleep pattern while operating world-wide East-West routes. However, the sleep obtained over three days preceding each duty period is usually similar in duration to that obtained over three day periods while on non-flying duty and the ability of the pilot to obtain a similar amount of sleep appears to be an essential factor in preventing subjective fatigue.

There is a cumulative effect of repeated adaptation to time zones and irregular hours of duty. Aircrew find it increasingly difficult to maintain an acceptable sleep pattern as the number of days route flying increases. It would appear that the work load (average hours duty/day) compatible with an acceptable sleep pattern diminishes in a logarithmic manner with the number of duty days. This implies restrictions to the deployment of aircrew if serious sleep disturbances are to be avoided.

To increase the effectiveness of a strategic transport force in the absence of positioned crews, double crew continuous flying operations have been studied. In these missions the off duty crew rests within the aircraft. The success of such operations depends to a large extent on the crew which operates during the period in which they are normally accustomed to sleep.

It is considered from experience within the Royal Air Force Air Support Command that the optimum duration of such a mission is about 48 hours. Beyond this period serious sleep disturbances appear. An operation of 48 hours using a fast strategic transport provides a world-wide capability and during this time the aircraft can circumnavigate the world. 7- 1

Aircrew operating in the strategic long haul role experience repeated time zone changes and irregular and often long hours of duty. An'acceptable sleep pattern is, therefore, of prime importance in maintaining their well-being and operational efficiency. In the present paper the sleep patterns of aircrew operating in the normal transport mode as a single crew and of aircrew during continuous flying operations using double crews are described. The work load (average duty hours/day) compatible with an acceptable sleep pattern is examined and the operational limitations imposed by sleep disturbances on single and double crew missions defined.

SINGLE CREW OPERATIONS

The observations were made on a captain within the Boeing 707 fleet of the British Overseas Airways Corporation. The routes covered by this fleet form essentially an East-West pattern and three types of operation were studied.

1. Western Transatlantic Return Schedules The schedules had in common the initial rapid time zone change (5 hours) of the Atlantic crossing. A North Atlantic shuttle consisted of two return flights between London and Toronto and was completed within seven days. A New York-Nassau shuttle consisted of two daily return flights between New York and Nassau between the North Atlantic flights and the schedule was completed in just over four days. In a Bermuda-Mexico City shuttle the initial time zone displacement from London to Bermuda was extended temporarily on two occasions and the complete schedule took less than seven days.

2. Eastern Return Schedules In these two schedules time zone displacements of % hours to Sydney (GMT + l@) and 13 hours to Honolulu (GMT - 10) were experienced in about six days and were followed by the return flights westwards.

3. Round the World Schedule The schedule studied involved a flight in a westward direction via Sydney. The time zone displacement was maintained in the same direction throughout the operation.

The work/rest cycles of the pilot were recorded in a diary which provided the duration of duty periods (flying time + ground duty time), the time of retiring to bed and of rising from bed and the estimated duration of sleep. The information was recorded for a period of eighteen months and a control period of approximately one month was included during which the pilot was not involved in route flying and was, at that time, permanently within the European time zone (GMT + 1). From the diary the day to day life and sleep patterns of the pilot were reconstructed and are given in detail in a previous paper (2). The control period provided information on the estimated duration of sleep for each day and the average sleep per day was calculated for successive three day periods. During route flying the estimated duration of sleep periods was obtained and the average sleep per twenty four hours for three days preceding each duty period was calculated. This information indicated when the average amount of sleep over a three day period during route flying fell below the minimum observed during the control period.

The work load of route flying was obtained from the duty periods and the number of days on route. Work load was oalculated as cumulated duty hours for route at completion of each flight divided by (number of days on route + 1). The additional day in the denominator indicated that the pilot was in preparation for the initial flight from base during the twenty four hours preceding duty.

RZSULTS During non-flying duty the range of the individual sleep periods was 5 hours 25 minutes to 7 hours 50 minutes and the range of sleep per day averaged over successive three day periods was 6 hours 17 minutes to 7 hours 25 minutes with a mean of 6 hours 52 minutes (Figs 1 and 2). These findings are consistent with the observations of Tune (5) for an adult in the fifth decade.

During route flying the sleep of the pilot was grossly modified (Fig 1). The duration of about half of the sleep periods (53%) was within or exceeded the range of the duration of sleep periods observed during the control studies, i.e. the range was 5 hours 50 minutes to 11 hours 0 minutes with a mean of 7 hours 21 minutes. The remaining sleep periods were divided into naps of up to two hours duration (mainly of 15 minutes to 45 minutes duration) and into periods of sleep with a mean duration of 3 hours 49 minutes (range 2 hours 45 minutes to 4 hours 50 minutes). The range of sleep per twenty four hours averaged over seventy two hours preceding each duty period was 5 hours 0 minutes to 8 hours 35 minutes with a mean of 6 hours 57 minutes (Fig 2). The operational and physiological significance of this complex seep pattern is discussed in a previous paper (2). In U I Route Flying

c 0 z0/:I 0

2t "r

2 10 't Non Flying Duty

Fig. 1. Histogram of duration of individual sleep periods during non-flying duty and during

route flying. I

10 - Route Flying

VI 5- .-'CI a& a

15 L t

Fig. 2. Histogram of averaged sleep over successive three day periods during non-flying duty and over seventy-two hours preceding duty during route flying. 7-3

Full details of duty hours and work load of the flights studied are given in a previous paper (3). Flights in which the average duty per day exceeded five hours have been plotted against the number of days on route in Fig 3. Flights in which the average sleep duration preceding duty was within the range of the control observations are presented as circles and those in which the average sleep duration preceding duty was less than the minimum observed during the control period are presented as triangles. A zone has been constructed which separates work load in which the average sleep preceding duty was always above the minimum of the range of the average duration of sleep observed in the control period from flights in which the average duration of sleep preceding duty was always less than the minimum observed in the control period. From the boundaries of the zone cumulative duty hours for days on route below which sleep difficulties are unlikely to arise (optimum work load) and the cumulative duty hours for days on route above which an acceptable sleep pattern is unlikely to be maintained (maximum work load) have been calculated (Table I). The optimum and maximum work load for days on route are illustrated in Fig 4.

Oayr an Route I I I 1 I I I I I I 1 1 1 2 3 L 56 7 8 9 10 11 12 I3 I4 15 16 Duty Period ldayl

Fig. 3. Workload plotted against the number of days on route. Circles indicate that the workload is compatible with the control sleep pattern. Triangles indicate that the average sleep per 24 hours over 72 hours preceding duty was below that observed during the control period. A zone has been constructed which separates workload compatible with acceptable sleep patterns from workload unlikely to maintain an acceptable sleep pattern.

Optimum Maximum Data obtained by calculation from Fig. 3. Days on Route Workload Workload Optimum workload is the cumulated duty hours for days on route above which sleep diffi- 2.0 26 2% culties may be encountered. Maximum work- 3.0 32 36 load is cumulated duty hours for days on 4.0 373 42 route above which an acoeptable sleep 5.0 42 47 pattern is unlikely to be maintained. 6.0 46 51 7.0 54 8.0 54 Note:- Calculation of workload is given 9.0 62 by (No. of days on route + 1) x 10.0 Average hours duty/*. The 11.0 6568 (number of days on route + 1) is, 12.0 866 71 termed the duty period. 13.0 70 74 14.0 73 7@ 15.0 76 79 16.0 79 82 7-4

Fig. 4. Cumulated duty hours for days on route obtained from Table 3.

DISCUSSION The data, which are dealt with in greater detail elsewhere (2, 31, indicate that the work load compatible with an acceptable sleep pattern reduces, probably in a logarithmic manner, as the number of days of the schedule increases. The effect of irregular duty hours and time zone changes ie, therefore, reflected in a reduction of the average work load as the duration of the schedule increases. It would appear possible that the critical parameter in maintaining an acceptable sleep pattern is not the duration of each duty period but the overall du.ty hours in relation to the duration of the schedule.

Work load unlikely to lead to sleep difficulties can be separated by a zone from work load unlikely to be compatible with an acceptable sleep pattern and the borders of the zone may be termed, in the present context, the optimum and maximum work loads respectively. The increase in duty which converts an optimum to a maximum work load is small. In a schedule of ten days duration the optimum and maximum work loads are 5.5 hours per day and 5.9 hours per day leading to cumulative duty of 603 and 65 hours respectively. It may, therefore, be expected that minor modifications to schedules would be of considerable benefit. For instance, extending a schedule by several hours can be crucial as it provides the opportunity for a further period of sleep or greater flexibility in determining a critical sleep period.

Planning an operation for the work load to remain below the zone has the advantage of maintaining aircrew in a satisfactory condition to cope with a hastened operation and its extra work load. It is, therefore, advantageous to schedule operations at or below the optimum work locxd although schedules within the zone may be satisfactory. There is, however, no evidence from the aeromedical literature to suggest that limited sleep deficits, which may be experienced with work loads just above the zone, would lead to decrement in performance of the flying task.

The military implications of this study have been discussed elsewhere (4). , In this communication it was pointed out that to ensure an acceptable sleep pattern in military aircrew restrictions must be placed on the deployment of transport force. For instance a fast strategic transport aircraft operating without positioned crews from Europe to North Australia across the United States would take about four days and to increase the mobility of a transport force, double crew continuous flying operations have been investigated.

M)UBLE CRFW CONTINUOUS F%YING OPERATIONS

Continuous flying operations, in which aircrew sleep aboard the aircraft instead of sleeping at route stations, provide an operational capability independent of positioned crews. During such missions alternate duty periods of less than twelve hours duration lead to progressive desynchronisa- tion of the rest-work cycles from the original sleepwakefulness pattern and in any case an immediate reversal of the sleepwakefulness cycle is required in one crew. Such missions are demanding and lead to sleep difficulties.

In 1968 and 1969 two continuous flying missions, operated by Royal Air Force Air Support Command, were studied. The first operation was carried out using a Belfast aircraft with a cruising speed of 280 mph on a return flight between the United Kingdom and the Far East and the second operation was a global mission using a VC 10 aircraft with a cruising speed of 530 mph. In each case the sleep patterns of the individual aircrew were obtained preceding, during and following 7-5

the flight. This provided information on sleep patterns during each mission and on the time required to re-establish a normal sleep pattern following the operation. Complete details of these missions have been published elsewhere (1).

The Belfast mission was scheduled from RAF Brize Norton (United Kingdom) to RAF Changi (Singapore), via RAF Akrotiri (Cyprus), RAF Muharraq (Bahrein) and RAF Gan (Indian Ocean). The flight from RAF Gan (Indian Ocean) to RAF Changi (Singapore) was aborted and was followed by a delay at RAF Gan for about 18 hours. A diversion on the return flight fromRAF Akrotiri (Cyprus) to RAF Brize Norton (United Kingdom) was made via RAF Gibraltar. The mission, which was scheduled to take 72 hours,was of 112 hours duration.

The VC 10 mission operated from RAF Brize Norton (United Kingdom) via USAF Elmendorf (Alaska), USAF Wake Island (Pacific Ocean), RAF Changi and RAF Muharraq. The mission was scheduled to take 47& hours and was completed in just over 45 hours.

WULTS For the Belfast mission the sleep records of the individual members of each crew are given in Fig. 5. In the case of the VC 10 mission analysis of the duty patterns revealed that two of the three sectors operated by the first crew were within their normal wakefulness period. The second crew operated during their normal hours of sleep but they were required only to operate two sectors and their task was completed within 36 hours. The disturbance of sleep was, therefore, more evenly distributed in the VClO operation compared with the Belfast operation. In the sleep pattern obtained from both crews there was evidence of sleep deficit but nodsleep patterns were established in the Belfast after six days and in the VC 10 operation after three days.

Hours 9 r Aircraft Commander Hours 9 ,- CO-Pilot Crew I Hours 9 CO-Pilot Crew 2

It 51 4L IIIIII is 23 28 z 7 12 18 23 28 2 7 I2 I8 23 28 2 7 I2 MOY June May June MOY June Houri 9 A Captain Crew 2 Hours 9 r Engineer Crew I Houri 9 r Enginrer Crew 2

4- 4- 4- 41 v, 1 I 18 23 28 2 7 I2 18 23 28 2 7 I2 18 23 28 2 7 I2 Junr June June

Fig. 5. Movement of individual estimated sleep durations averaged over three days during the Belfast operation. The operation commenced on May 28th. The vertical bars are the range of sleep duration averaged over three day periods during non-flying duty.

DISCUSSION It was evident from the Belfast mission, and to a limited extent from the VC 10 operation, that the crews with duty periods involving the usual time of sleep exhibited sleep deficits of a more serious nature than crews with duty periods covered by the usual working day. The success of double crew continuous flying operations is, therefore, dependent on the fitness of the crew which has to reverse thei.r nornial rest-work cycle. Rest periods should be of sufficient duration to provide an adequate sleep period. In the present operations rest periods approached 10 hours duration and it is considered that if rest periods (and therefore duty periods) longer than this are possible then the sleep patterns would be improved. This may not be possible in the case' of a fast strategic transport aircraft.

The five day Belfast mission was extremely arduous and it is probable thiit this represented the limit of such missions. It is considered that missions of approximately two days duration present a reasonable operation and further experience, using the Belfast aircraft, has tended to confirm this observation.

CONCLUSIONS

Observations on the sleep patterns of aircrew during single and double crew operations high- light their fundamental difference. In a single crew operation it is essential to plan for an acceptable sleep pattern throughout the schedule but in double crew operationes sleep deficit is inevitable. A single crew operation can support an operation of long duration but limited deployment capability whereas a double crew operation is of short duration but highly mobile. The relation, compatible with an acceptable sleep pattern, between duty hours and the periods of time in which the duty hours are completed for single crew operations are plotted in Fig. 6. From experience within Royal Air Force Air Support Command the optimum duration of double crew operation is considered to be 48 hours although operations up to 72 hours are feasible. From an operational point of view this provides a world wide capability for a fast strategic transport aircraft.

Elapsed limo Hours Day5 150,

Fig. 6. Relation between duty hours and period of e:lapsed time compatible with an acceptable sleep pattern for a single crew operation. In the case of a double crew operation duty hours are equivalent to elapsed time.

Houri duly

ACKNOWLEEEMENTS

The author is indebted to the Principal Medical Officer, Royal Air Force Air Support Command and Principal Medical Officer (Air), British Overseas Airways Corporation for the opportunity to carry out this study. 7-7

REFERENCES

1. Atkinson, D.W., Borland, R.G. and Nicholson, A.N. Double Crew Continuous Flying Operations. A study of aircrew sleep patterns. Aerospace Med 190. In Press.

2. Nicholson, A.N. Sleep patterns of an airline pilot operating world-wide East-West routes. Aerospace Med 190. In Press. 3. Nicholson, A.N. Duty hours and sleep patterns in transport aircrew operating long haul routes. Flying Personnel Research Committee Report, Ministry of Defence (Air Force Department) London, 1970. In Press.

4. Nicholson, A.N. Military implications of sleep patterns in transport aircrew. Proc. roy. Soc. Med. 1970. In Press.

5. Tune, G.S. Sleep and wakefulness in a group of shift workers. Brit. J. ind. Med. 1969, 26, 54-58. 7-8

DISCUSSION: PAPER OF DR XICIIOLSOB

PERRY Reference double crew operations. \Vhat was the change-over period between crews?

NICHOLSON The take-over crew would come up to the flight deck about &-$ hr before their shift started, so that they would lose some of their rest period,

RUTEIFRANZ You showed sleep duration histograms for aircrew, but can this be considered a normal pattern if it WB~disturbed by flying duties?

NICHOLSON Sleep patterns were followed over a period of four weeks during nan-flying duty so I consider that the histograms obtained reflect the normdl sleeping behaviour of these aircrew. Some individuals habitual:Ly sleep less than others, single men have an irrebwlax pattern compared aith married men. However, there are considerable day to day variations so records must be taken over at least a month if they are to be valid in studies of this type.

RUTENFRANZ &we you peqformance data on short and long sleepers? \ NICHOLSON This would be interesting, especially for selection, but it is not known.

BENSON In aircrew who were sleep deprived during double crew operation, was there any evidence of a decrement in performance or any correlate in their subjective as se s sme nts?

NICHOLSON The aircraft commander, who did not flying the aircraf't, considered that the quality of aircrew performance was satisfactory at all. times. At the end of 5 days the aircrew said that they had had enough and would not like to continue this type of duty for a longer period. BZNSON This was a peacetime operation. Hog long do you thinlc 10-10 hr duty cycle could be continued in the stress of conflict?

NICHOLSON A 48 hr period is quite satisfactory and this require:; another 2 days for the sleep rhythm to return to normal., If double crew operation is continued for 4-5 days then it may take 7 days for no:cmal sleep rhythm to be established after the flight, In the event of 'mr I would think that 3 days could be operated routinely without decreinent.

PRESTON Have you any comment on the re-establishment of normal sleep pattern following eastward compared with westward flights?

NICHOLSON This may not be a popular answer, but I have not found any difi'erence between the two. Civilian aircre.:r rarely adapt fully to local time. Among the large number of factors which influence the restoration of a normal sleep rhythm, the direction of flight does not appear to have a significant effect.

PRESTON In BOAC, crews take about I5 days to go round the world and may have to spend up to 3 days at slip stations. Inevitably these crews try to adapt to local time and hence have problems with sleep. In contrast TiiA and Pan American send their crews round the world in 7 days with lay-over times of only 12-24 hours. These crews stay on home base time and stick rigidly to it so they do not have the same problem with disturbances of sleep rhythm.

NICHOLSON The work load of BOAC and Pan American pilots is very similar in terms of hours flying per day. However, as you point out, the American crews don't have this problem of tryix to adapt to local time. I think the amount one adapts at each place one lands is a significant istress to long distance transport aircrew.

WHITESIDE Do civil airlines give their staff formal instructions to keep to home base time or to adapt to local time7 I believe that Air Ikance tell their pilots to stay on Paris time.

PRESTON BOAC have no viritten instructions, but leatures are given on sleep habits and the desirability of keeping to home base time. If this policy is to be achieved very good hotels are required which provide meals at the right times. Unfortunately not al.1 stop-over centres can provide such facilities, and social pressures to adapt to local time are often very strong. 7-9

IIOPKIN The ICAO formula to minimise disturbance due to travel includes four factors: travel time, time zones in excess of four, and departure and arrival times expressed in local time. Could you comment on the importance of this and of the last two factors in particular?

NICHOLSON The ICAO formula was devised by Dr Buley for members of the organisation viho had to aaapt to a local time, that is a permanent translation of time zone, I do not think this kind of formulation is relevant to transport aircrew in either a civil or a military organisation.

BERKHOUT Part of the problem of double-crew operation is the difficulty in establishing a new sleep pattern in the aircraft environment. Do you not think that crews should spend 2-3 days before such a flight adapting to the ner'i duty cycles?

NICHOLSON A period spent before a flight adaptiw to a new duty cycle would effectively remove aircrew from operational duties, and the benefits of double crew oaeration axe likely to be lost.

MACLA.%l? I would like to point out that transport aircrew are, probably, already adapted to unusual rest/duty cycles, which is after all, their normal working environment. For this reason I wonder if prior adaptation to the specific duty cycles associated viith double crew operation is really necessary.

Differences between Military and Commercial Aircrews'

Rest and Activity Cycles

Dr. Kay Staack

Colonel, GAF,MC

Command Surgeon,

Air Transport Command 8

During the past years we have gained considerable experience on fatigue during long distance flights under conditions of disturbed diurnal rhythm. The object of our investigation was to find out, whether - in addition to the dwcation of flight and the diurnal rhythm factor - there exist any other factors contributing to the difficulties arising in connection with the rest and activity cycles. For this purpose, aircrew members of the FMOD Air Transport Wing flying the Boing 707 have been in- terviewed with respect to their flying duty, ground duty and duty-free time.

The results of these interviews show, that the difficulties arising are not so much caused by the duration of flights and even less by the disturbed diurnal rhythm, but very much more by certain administrative procedures, by prologned layover times and, most of all, by the ground duty times.

In this respect, there is a marked difference between military aircrews and aircrewa of commercial airlines. Good leadership and team spirit as weXL as an effective organization are of great importance. 8-1

-Differences between Military and Commercial Aircrews: --Rest and Activity Cycles The GAF Air Transport Command includes 2 Noratlas 2501 ‘iJings, 1 Transall c-160 ljiing and 1 helicopter Bell UH 1-D Wing for tactical air transport operations and 3 Flying Training Bings plus the FMOD Air Transport Wing. The latter is a multipurpose flying unit, its main task being the transportation of military as well as government’s VIPs and, secondly, to establish a routine air lift between the Federal Republic of Germany and the United States.

The need for this standing airlift capacity arose from the fact that certain specie1 training for the Armed Forces, especially for the Air Force, is being acconplished jn the United States, for example basic jet pilot training and guided missile traininE. Thus, a certain amount of personnel and materiel has to be transported constantly in both directions. During the first years after the build-up of the Bundeswehr these transports were carried out by the German Lufthansa Airlines. Be- cause of the high costs involved the Air Force later on was equipped viiLh 4 DC-6 aircraft and in 1969 the Long Distance Air Transport Squadron was converted to 4 Boing 707 aircraft.

These aircraft operate regularly from Cologne-Bonn via lashington D.C. to E1 Paso or other air bases in the south-west of the United States, where the main centers of the German Training Command USA are located. For the operation of these 4 aircraft the following crew strength is available:

17 pilots; 8 of them qualified as aircraft commanders or, according to the terminology of the commercial airlines, as flight captains;

8 radio operators/navigators;

12 flight engineers;

15 stewards.

The average age of the aircraft commanders and co-pilots is 33 years, the oldest one being 51 and the youngest one 26 years of age. When excluding the oldest aircraft commander from the statistics (he is the wing commander aged 51 years) the average age of the pilots drops to 31 years. The average total flying time of the pilots amounts to 3.700 hours; the average per year is around 600 - 700 hours and the monthly average about 65 hours. They rank between LtColonel and 1st Lieutenant, the majority of them holding the rank of Major/Captain.

A Lufthansa flight captain has an average age of 45 years; to become captain on the Boing 707 he must have a flying experience of lo years and a total flying time of 5000 - 6000 hours. His maximum flying time per month should not exceed 70 hours.

The age figures for the other military crew members are as follows: The average age of the radio operators/navigators is 30 years, the oldest one being 35, the youngest one 26 years; they rank between Captain and 1st Lieutenant. The flight engineers are the oldest crew members, their average age is 38 years; they rank between Master Sergeant and Senior \‘/arrant Officer. The stewards’ average age is 24 years, they rank between Private 1st class and Sergeant. In general it can be stated that the military aircrews are younger and have less flying experience than the comparable commercial aircrews.

The routine schedule of the flights from Germany to the United States is as follows:

Monday: 1 aircraft to El Paso, 1 aircraft towashington D.C.; Wednesday: 1 aircraft to El Paso; Thursday: 1 aircraft to Washington D.C.

All flights to Washington D.C. are accomplished with basic crew, i.e., one aircraft commander and first pilot, one co-pilot, one radio operator/navigator, one flight engineer and for each 30 passengers one steward. If the flight is continued to El Paso or other air bases in the western United States, the crew will be augmented by a third pilot and a second flight engineer.

It must stressed here, that in excess to these regulhr flights special missions have to be flown by the same aircrew and aircraft, for example disaster support as it was the case during the past months for Tunisia and Turkey as well as VIP-flights with the President, the Chancellor or other high ranking government officials. These flights sometimes go around the world, for instance to Japan, and are usually more stressing for the aircrews, because the routes are unfamiliar to them and the time zone shifts and climatic differences have a greater negative effect on their performance.

With regard to crew duty time limitations, as well as crew rest and free time all flights are scheduled strictly in accordance with the MAC Manual 55-1 (Airlift Operations Manual USAF). A routine round trip to El Paso is accomplished on the following schedule: 1st day: Departure Cologne-Bonn 08.30 Z = 09.30 Local = 09.30 Central European Time Arrival Washington 16.30 Z = 11.30 Local = 17.30 Central European Time Departure Washington 18.00 Z = 13.00 Local = 19.00 Central European Time Arrival El Paso 21.30 Z = 14.30 Local = 22.30 Central European Time

2nd day: Free Time

3rd day: Departure El Paso 17.00 Z = 10.00 Local = 18.00 Central European Time Arrival Washington 20.30 Z = 13.30 Local = 21.30 Central European Time Departure Washington 23.00 Z 17.00 Local = 24.00 Central European Time

4th day: Arrival Cologne-Bonn 06.30 Z = 07.30 Local = 07.30 Central European Time

For the rest of the 4th day adon the following day the crews are off duty. It does not make any difference, vihether these two days are nornal vorking days or happen to be holidays, If a flbht en&on a Saturday morning it i6 possible that the crew has to fly again on Monday morning. On the average each crew is scheduled for 3 - 4 standard flights per month, 2 - 3 long flights to El Paso and 1 or 2 flights to !‘iashington.

The time schedule for the Washington flights corresponds to the above schedule, with the exception that the departure for the return flight takes place on the evening of the second day and the arrival at Cologne-Bonn on the morning of the 3rd day. These flights can be best compared with the Lufthansa flights on the North Atlantic route (Germany-New York), as the actual flying time is about the same as well as the timing of the flights, i. e. East-Best in the morning and Uest-East in the afternoon or evening. The main difference is that the commercial aircraft is being turned round to fly back on the same day with another crew. The East-Nest crew goes back on the following day.

The question is now, what are the differences between military and commercial aircrews in these scheduled flights? First, we have to consider the total duty time spent during one flight, or in Air Force terminology, the flying duty time. Showtime for the military aircrews is 2 hours before take-off; for VIP flights it is even f, hours. The crew has to go through the whole technical pre- flight check according to the check list, the flight plan has to be prepared and filed, ATC clearance has to be obtainad. The flight engineer has to check the fueling, the stewards have to insure the timely delivery and storage of the inflight meals. Also the loading of cargo has to be supervised. So, these 2 hours before take-off mean already hard work for the whole crew, whereas on a commercial airline the aircraft is being handed over to the aircrew by the ground crew chief ready for take-off. Consequently the coamercial aircrew’sshowtime is only 1 hour. The aircrew usually boards the aircraft about haan hour before take-off and only perform a final cockpit check. The flicht captain is only responsible for obtaining the weather brioIing; flight plan, clearance, cargo certificate, passenger list etc. are prepared for him by the @;roundservices. This procedure is not only znplicable for the airport of departure, but also for any intermediate stop. Everything is pre-arranged by the stationary ground services of the own airline or another airline under contract. On the other hand the military aircrew has to take care of everything necessary at intermediate stops: refueling, unloading and loading of cargo, checking-out and -in of passengers- against- PassenRer- lists etc. So. at short stops of one or two hours, there is actually no rest time for the military aircrew.

After block-in time and de-briefing at airports of destination and after having completed the necessary administrative procedures, both military and commercial aircrews are usually off duty.

The duty-free day for the military aircrews on the flight to El Paso must be granted in order to comply with the regulations for crew rest. Despite the fact that the crews are thus able to relax, they still claim that they do not really feel Iton optt at the time of take-off and that the return flight (West-East), especially the last part of it is more tiring than the Eai;t-:!est flight. Of course, the reason for this is that they just star e6 to acclimatize themselves to the time zone change and that this process Is being interrupted.

The relatively long intermediate stop at Y!ashington on the return flight (2 1/2 hours or more) has only financial reasons. The aircraft has to arrive at Bashington early enough to be loaded before 5 o’clock in the afternoon, because otherviise the civilian ground crew would have to be paid overtime. On the other hand, the aircraft cannot leave Vashington too early, in order not to arrive in Cologne-Bonn during night time, since the pmssengers would then be unable to c.?.tch any means of connectin;. transportation to their final destinations within Germany.

A.t this point I should like to call your attention to the somewhat curious or sometimes even ridiculous administrative regulations aithin the Armed Forces, which are not always fair on the crews and not likely to increase their enthusiasm. The military aircrews’ travel expenses are paid the same way as those for soldiers being on field duty, for example during manoevers. Thus, the aircrew being on duty during the night flight West-East gets much less travel allowance than the military passengers, who are comfortably asleep in their seats and get the full travel allowance far overnight-TDY. There is a difference in the proportion of about 1 : 5!

So far we have considered only the differences in the flying duties. But there is another very significant and weighty difference in the rest and activity cycles between military and commercial aircrews, namely the fact, that the military aircrews are soldiers of the Armed Forces. As such, they are, of course, not officially entitled to a. fixed viorking time per week or month. They have to be on duty at any time if need arises. Nevertheless, the norm1 working time is 42 hours per week for all personnel of the nrined Torces. The aircrews have to be on duty the full length of that time, even if they do not fly. This is not so much a problem of overtime duties, but more one of an additional stress in the form of extra tasks and responsibilities. Here, the heaviest burden 8-3 lies on the officers (pilots and navigators). ThHhave to fill the following positions in the peacetime organization of their units: - wing commander - squadron leader - flying safety officer - NBC control officer - flight operations officer Boeing 707 - s 6 officer (communications) - chief of statistics - physical training officer Furthermore, they have to take part in rotating alert duties as aerodrome officers (the non: commissioned officers in the base ops.). The career officers also have to participate in a multitude of different courses, some of them combined with examinations. For example, it is necessary to pass a staff officer course in order to be eligible for promotion to the rank of Major. - Beside all these tasks and duties they must keep themselves up to date with regard to any new flying regulations, notams and technical changes concerning their aircraft.

Because these ground duties are usually connected with paper work and sometimes rather boring, it is quite understandable that the aircrews are eager to fly and that they feel happy each time the weels are up again. Furthermore, the right team spirit and good leadership help to overcome the disadvantages resulting from a clumsy and obsolete military administration and the lack of M efficient ground service organization. It must be emphasized here, that the aircrews of the Boeing ?o?-flight are handpicked from a11 Air Force units.

On the other hand, the duty of the commercial air crews is only to fly their missions; if they do not fly they are off duty. Also their flying task is easier insofar as they usually stay on the same route for prolonged periods of time (one or more years). If their monthly flight schedule is favorable enough to enable them to fly their 70 hours during the first half or the first two thirds of the month they are even able to work out some additional time of leave. Of course, their payment is better than that of the military air crews, but they are employees of a private company and therefore do not enjoy the same degree of security with regard to old age, illnemand injuries or death in line of duty as the military personnel. DISCUSSION: PAPER OF IIR STIACK

WICHOLSON In your experience do military transport pilots fly more or less hours than their counterpart in civilian airlines?

STAACK Military pilots flying 707's commonly average 70-80 hr a month, a value which I think is close to civil airline pilots. The recomendbd maximum is 60 hr with an absolute maximum of 80 br.

NICHOLSON Then their workload is quite high?

STAACK Yes, it is,

VWITESTDE Your paper highlights an operational factor which should be brought to the attention of the BIilitary Committee, In military aviation, particularly in the transport role, aircrev should not be loaded with duties that can adequately be performed by ground personnel; civilian operators provide a clear example of how pilots may be unburdened of these ancillary duties, F'UCHS I agree with your comments and stress the importance of bringing these recommendations to the attention of the Military Cornnittee.

PERRY If recommendations about off-duty times are to be made, due allowance must be made for necessary military duties. Consideration should also be given to problems of manning in contracting military forces.

NICHOLSON In the IulF aircrew are General Duty officers, and as such their responsibilities are wider and also different irom their counterparts in civil aviation. ;Ye should take care and not make invidious comparisons between flying personnel with similar in-flight duties in civil and military aviation. It is our responsibility to make recommendations about the duration of duty cycles and the time required for rest and recovery, but I do not think it is our responsibility to say how these recommendations should be implimented in relation to other riilitary duties.

STUCK I agree that we should be careful in the comparisons that are made between military and civil practices, though om findin&s do underline the differmces which exist between military administration and concepts of modern management,

FUCHS The AS1.P have been asked by the Military Cornnittee f'or advice on rest and duty cycles, AWwill make recommendations in the form of an Advisory Report. It is the rcsponsibility of each nation to make use of these recommendations in a manner appropriate to local coixlitions. 9

'Workload' and 'Performance Limiting Factors' of Air Traffic

Control Radar Operators

Hans J. Zetzmann, Dr.-Ing.

Deutsche Forschungs- und Versuchqanstal t fijr Luft- und Raumfahrt e.V. Institut fur Flugfunk und Mikrowellen Oberpfaffenhofen I 9

Summary In the 'servo loops' of the man-machine system of Air Traffic Control man continues to play a decisive role in ensuring safe and expeditious running of traffic. An important source of information in this system is the radar equipment whose display gives the controller an important basis for evaluating the air situation. These displays are discussed from the aspect of 'human engineering'. Where traffic is dense, particularly high demands are placed on correctness and rapidity of controller decisions to ensure a safe dispatch of traffic.

The paper deals further with the physiological environment of ATC activities and points out how readily human beings may here be subject to 'stress'. The definitions of the terms 'workload' and 'stress' are discussed; it is shown that, and why, all efforts towards an exact assessment of controller capability under peak loads have failed to lead to fully satisfactory results so far. Further research work has to be done. 9-1

THE TERMS 'WORKLOAD' and 'performance limiting factors ' mentioned in the heading are attractive and might arouse the expectation that this report will come forward with remarkably new things in addition to those already known about this subject. However, I have chosen these terms merely after much hesitation since the term 'stress' so often used in both German and foreign literature can express the points, about which I wish to present a few special ideas with respect to the capability of Air Traffic Controllers, with even much less clarity and definition than what seems possible with the terms used in the heading.

The sum of problems which I wish to deal with is the behavior and temporary limitation of human capability in a man-machine system such as represented by work in the ATC servo loops in situations when high concentration of air traffic places particularly high demands on the controller with respect to correctness and rapidity of the decisions he must make to ensure a safe dispatch of traffic.

However, let us first say a few things about radar observation proper. Only about ten years ago when primary radar was employed in air traffic control alone and when the segregation of the moving targets of interest from undesired permanent echoes (c1,utter) constantly added to the hardship of controller work, many problems were awaiting solution from the medical aspect. Let me briefly mention four principal groups: - the inherent below-threshold character of the information as such, - the visual problems of target recognition with their ophtalmological parameters such as brightness contrast of the signals (l), 'focus effect' in the case of poor focussing of the radar picture, heterophory due to non-parallel orientation of the eyes (2), problenis of peripheral vision (3) and many others more, - the effects of environmental brightness with the weak illumination of the radar screens, dark-field adaptation of the eyes, stimulation of the ciliary muscles and contraction and elongation muscles of the eyes, as necessary against fatigue, the related diversion of the eyes towards the control strip board, - the problems of observation performance as referred to the time of observation.

A comprehensive literature is available today concerning these psycho-physiological relationships, their specific valences and their satisfactory mastering in radar screen observation. Unlike that situation in past days, present-day, modern secondary radar facilities, with their 'synthetic' display purified of annoying clutter and showing merely the moving targets of interest plus certain alpha- numerical symbols and information on their specific nature will allow a superior adaptation of man to the machine in the form of the more easily interpreted information offered as well as more relief in the sense of 'human engineering'; all the more so when non-flickering daylight-imnune radar displays are available as derived in the TV converter. The stress, at first only of a physiological nature, can be reduced at this point. However, such advanced facilities are at present far from being available everywhere. From the operational aspect the following situation results. The improvements introduced by superior radar facilities in the specific controller function will be largely offset by the considerably higher density of traffic with respect to space and time on the one hand and by closer separaticn of aircraft on the other, as made possible - and therefore implemented - by these modern means, with a resultant increase in collision hazards. By and large, the purely intellectual stress on the controller which I wish to describe with the recently coined term of 'mental workload' (19,ZO) remains the same and the effects of observation time on observation performance, hence the fourth item enumerated before, has considerable weight even today. Let me report on a number of recent German investigation results in this respect.

The vigilance problem is known to have two aspects. It is well known that vigilance is at a rather poor level at times of low traffic. Time and again mistakes in traffic control activities are made just at times when no particularly trying demands are placed by the traffic situation as such, but the radar air traffic controller only has to perform a mere routine in watching the progress of traffic. In the case of dense traffic and strong conflict potentialities the air traffic controller at the radar screen will normally operate with strong mental exertion and concentrated attentiveness. Mistakes comnitted in such situations can then always be traced down to pure fatigue (e.g. because of excessively long watches) or/ and to flooding with complexities which I wish to describe as particular stress situations. I shall revert to the concepts of 'workload' and 'stress' later.

Fig. 1 is derived from investigations of SCHMIDTKE (4) and clearly illustrates this observation problem; the results are in good agreement with those of other authors (5,6). The curve shows the relation between echo or stimulation rate and recognition quota. It has the shape of an inversed "U". With a low stimulation rate ('undertaxing' situation) the recognition quota is distinctly poorer than with average stimulation rates that obviously reflect the normal performance dependence of controller activities. The differences in observation performance as compared to the stimulation rate are shown combined in Fig. 2 (table) as taken from the aforementioned paper of SCHMIDTKE. This is a series of experiments made with high and low stimulation rates. It is evident that the percentages of overlooked stimuli (omissions) are distinctly differing from each other. While less than 3% were overlooked in the experimental series with high stimulation rate, the related percentage closely approached 16% in the case of the series of experiments with low stimulation rate. SCHMIDTKE here points out that particularly large differences between the two experimental conditions appeared in the performance decrease from the first to the second hour of observation work. In agreement with what time and again has been confirmed in actual practice this means that there is a distinct dependewe of the vigilance of radar observers on echo rate, This brings us to the influence of time.

Fig. 3 shows the results of series of special experiments conducted likewise by SCHMIDTKE for this purpose. The influence of the duration of the watch onto the recognition of collision courses is here shown, if indeed in the merely two-dimensional radar supervision of moving ships at sea. The curves of the mean recognition times are plotted over an observation period of four hours as a percentage of the running time of the collision courses. The shaded regions denote the ranges of dispersion (spread); the upper curve holds for a single radar observer, the lower one for a team of two observers. The diagram shows two essential reFT€K The reliability of collision course detectiofiecreases with increasing time of observation. A striking fact is the nearly linear increase in the dispersion of recognition with the time of observation. With a team of two simultaneously working observers the degradation grows at a far lower rate and the resultant increase in dispersion is hardly noticeable. These results back up the often voiced demand that watch times should not exceed two hours and that 'teawork' on the 'radar display' should be preferred practice.

Although for a number of reasons which I do not intend to discussresults gained in maritime radar surveillance cannot be exactly transferred to the air traffic control environment, it will probably be certain to make the general conclusion that the performance decrease of the radar air traffic controller will not be smaller, but that the higher inherent complexity will give rise to an even stronger performance drop at certain times. How can we get an account of this drop?

I am going to attempt an outline of the complex functions of the radar controller in terms as generally understandable as possible. According to definition the duty of air traffic control is ensuring safe and expeditious movement of air traffic. For these tasks the controller has available the information on the radar screen display, combined with supplementary control strip information and the information on other data panels. From these data he must develop a geographical and spatial concept, with a corresponding scale transformation with respect to the data display, followed by a continuous translation of the 'static' information offered to him into a 'dynamic' pattern. As compared to the space transformation which an aircraft pilot has to make of his flight path this is a task that calls for many times as much brainwork. Within the scope of our psychological considerations subdivision of the attentiveness here also plays a big role which is characterized by the concept of 'respondability'. The comp1exit.y of air traffic control shown in the typical example of Fig. 4 calls for very close continuous coordination with other radar air traffic controllers and other related personnel. Besides a varying amount of concentration on the matter on hand, the controller thus has to be approachable any time for coordination problems and he must, as it were, 'filter' and correctly evaluate from a host of individual information items those just required for smooth handling of his work. Besides determining the position on the screen of the target just being handled, the controller has to store information concerning other objects and take fitting action when a collision hazard develops as a result of flight level, heading, rate, and climb/descent movements of aircraft. It must here be further considered that not every target observed on the radar screen in a given position will endanger other objects in the same air space.

Unfortunately a film that had been prepared to show you the movements on a radar display has not been completed in time so that Fia. 4 can merely provide a graphical presentation of the progress of the flights. It shows the progress of five outbound and five inbound flights along an air lane with terminal area within a time interval of a few minutes. I have attempted so to present the variation in time of the horizontal and vertical guidance by the controller that the collision protection achieved by him comes into evidence. It must here be pointed out that, in the same way as with all advanced technical approaches, thought must be given to possibly occuring sudden system trouble. Weather and other atmospheric conditions and suddenly developing anon:alous flight conditions are here of importance.

The availability of radar equipment greatly facilitates controller work, but he should never be misled towards depending on this backing altogether. It must be possible any time to make the switch from traffic movenients under radar control to the more exacting standard spacing procedures. A1 1 these things mean that situations may develop any time during controller activities that put him into time pression and give rise to specific stress situations. Since the time when elctronic computers became a reasonable element, one has always endeavored so to engineer the technical side of the equipment that, by specific processes of data acquisition and processing, these resources relieve man from a number of manual and mental operations. This shall adapt as efficiently as possible the intelligibility and interpretability of information items to human capabilites, hence in an 'anthropotechnical' manner. However, despite the great technical complexity, there remains surprisingly enough a lack of quantitative data concerning the 'activity value' proper of the controller in the way it exists in particular in the critical approach zone of airports. And it is just this value which is to be improved by automation.

In the last years the word 'worklnad' has been introduced for describing the functional load imposed on both aircraft pilot (20) and air traffic controller. The analogy with the well-known term 'working load' (=effective load) of engineering, in particular electrical engineering, is obvious but there is no strict definition available in our case. If the suhjective difficulty of work is to be understood by this term, one rightaway faces the conflict that a determination or definition is required of the controller capability as included implicitly in 'workload' which obviously is variable with respect to time and matter involved. 'Workload' and 'ability', unlike the case of a technical device, are interrelated when man is involved. We must therefore be prepared - as once stated by RATCLIFFE (7), the English ATC expert, - to accept the term of 'workload' in any definition ''that is not in conflict with comn English usage and which lends itself to measurement I.

Let me here say a few thinas about 'stress'. Those that have not grown up in an English-language environment will not have rightaway the correct grasp of the flexibility with which this word can be employed for the various concept of technical, physical or physiological load. Therefore it seems astounding to me, a foreigner of a mother tongue other than English, and it seems to reveal a certain concept modification that, in a medical sense, the word 'stress', according to what. I see from the German usage of the word, both denotes stress in the sense of a 'workload' as such, and the response of the human system to such a load (25). Using the word 'stress' we Germans mean load, and factors that give rise to stress. The related response of the human system is called 'stress reaction'. It can thus be defined as an alarm reaction of the secretary glands as well as of the entire vegetative nervous system to effects inimical to the human organism. One therefore also refers to 'stress disease', namely bodily exhaustion to which pilots or controllers may be subjected in their activities in a quite characteristic manner. 9-3

These defense reactions of the human system to exogenous or endogenous stimuli have been given different expressions in 1 iterature such as 'emergency reaction' (CANNON), 'ergotrope Umstimmung' (HESS) or quite generally 'adaptation syndrome' (SELYE). The adaptation syndrome thus is the reaction to stress of short or long duration such as occurs when life is at stake or strong emotional stimuli of other genesis are on hand - responsible controller activities in this case. The stress response has three phases : 1. alarm, 2. resistence, 3. exhaustion. Biological experiments have revealed that acute ulcers in the gastro-intestinal tract and an irritation of the suprarenal cortex with increased secretion of adrenalin can be observed as typical changes in the alarm reaction. Since thus neurohormonal mechanisms determine the progress of the adaptation syndrome, a 'real- time' assessment or measurement of the respective instantaneous biological condition is not readily possible. This may explain the fact that the present, not exactly physiological, measurements on controllers to be delineated in the following have failed to lead to full success so far. But let us first revert to the more general concept of controller 'workload'. In the last 6 to 8 years a host of experiments have been conducted to cope with this set of problems, if indeed not with a physiological, but with a physical approach by developing related mathematical models (8,9,10). Such a model has the form of one or several algebraic expressions whose function is the determination and prediction of a workload by computation. The related approach is as follows: the controllers task is broken down into a number of rudimentary components, the time required for each sub-task is measured, the so found time values are multiplied by suitable weighting factors and added up to give the total workload. Here it now turns out surprisingly enough that the enomus effort expended on mechanization of air traffic control so far has merely resulted in a minimum of quantitative values concerning the very nature of 'workload'. This is on the one hand regrettable for the controller himself since the last word about the rating of his activities is here still missing, and on the other hand it is regrettable for the ATC organization since in critical borderline cases it obviously has no means to determine the relative economical merits of various possible control configurations. This is a striking example of the fact that, in a highly complex man-machine system, obviously not only absolute limits of capability result but that also system econonly can no longer be properly assessed, let alone improved. For lack of time I cannot deal with the comprehensive mathematical calculations for determining the workload but I wish to report at least a little about a study of BAR-ATID ARAD, made at FAA in 1963, for an understanding of the underlying philosophies. This study, breaks down the problem into three components: - formulation of a workload model - experimental determination of the weighting coefficients mentioned above - effect on workload of changes in the sectorization of radar surveillance. This study is based on the following (not proven) axiom that the 'control workload' consists of three terms: - a 'background' load Lo which is independent of the number n of aircraft under control, - a 'routine' load L1 which is directly proportional to n and, 2 - an 'air space' load L2 which is proportional to n . Particularly elaborate formulations were set up for weighting the coefficients; various models were established depending on the kind of concepts chosen. As far as I know one has not been able to reach agreement on a certain model or combination so far. As already mentioned, 'controller workload' has resisted so far any attempt towards a clear and unique defintion. If we assume that the definition of workload is suitably assigned to the measurement method there are five technical possibilities of measurement which I want to descrlbe and dlscuss briefly:

- extraneous observation of the control activities such as made, for instance, in France by LEPLAT and BISSERET (11).

. This method has the inherent drawback that the desired knowledge must be obtained by interviews with the controllers. Psychologists have developed the method of 'instigated introspection'. The drawback is that the result cannot furnish sufficient objectivity since, by his comnentary alone, the interrogated person will introduce irreality into the situation and not describe the things he usually does but those he thinks that he does or even those he should do. Besides, there is a great temptation to restrict the description to straightforward things while the ATC functions proper that are difficult to explain to outsiders anyhow are not covered fully enough. - Physiological investigations concerning the effects of 'workload', 'strain' and 'stress' in the organism of the controller. It seems that such investigations have not been carried out with sufficient broadness and success so far. The underlying reasons have been intimated above. I shall revert to them later. - Simulator tests where the artificial traffic level is pushed up to the point where the controller is 'saturated'. 9-4

Such tests indeed allow a qualitative estimate of the relative capacities of different systems but no objectively accurate, down- to-practice definition of the level where the control system breaks down, For a statistically relevant evaluation of 'workload' and its growth until the 'stress' level is reached series of experiments must be made on many controllers with highly different traffic patterns which is expensive with respect to both time and effort. Besides, simulation will never be able to realize the hazard aspect inherent in actual controller activities. - Methods for determining controller overload by measuring his error rate, either in performing his normal duties or under an artificial basic load, e.g. on the basis of elementary arithmetical calculations.

There do not exist as many objections to this method as to the former one, but it presents the serious drawback that a determination of performance errors of the controller becomes difficult and often is downright ambiguous. I refer to related research results (7). - Assessment of the respective situations by experienced control1,ers in filling in questionnaires and in interviews held with the controllers, as carried out by ARAD and JOLITZ in five control centers of the FAA with a total of 16 different range sectors with complete radar capability (12, .. 13). According to English opinion this method, while being rather down-to- earth, has not led to fully satisfactory results SO far either (7).

On the basis of what has been said so far we can conclude that, despite the very high investigation efforts and expenses made so far it has not been fully clarified neither theoretically nor practically how the human reaulatinq element named 'controller' oerforms at the limits of caoabilitv of the overall air traf ic control ;ystem.-The following will explain to some extent the partial failure if the investigations made so far. A controller who, by an ever increasing growth in his control functions, is brought to saturation leading to a stress that cannot be straightened out by him any longer will automatically proceed towards reducing his workload by tricks of any kind. This will generally be at the expense of an expeditious traffic flow and delay of traffic. This may be favorable if,due to a reasonable human regulatory mechan sm Y a danger situation of traffic is prevented - or possibly not prevented - not by processing under stress 0 the limit of exhaustion but at an indeed uneconomic additional expense to be defrayed by the airline companies. Nevertheless, from a basic aspect, the set of investigation problems is not lacking interest, but remains worthy of further attempts and endeavor even in the future.

In concluding let me therefore once more revert to the physiological aspect of the problem. We had said that no fully satisfactory results have emerged so far with the measuring possibilities to get a physiological account of a human acting as a controller. This is inherent in the matter since, as already stated, a physical-instrumental observation of the biological condition of the controller right at his work in the station is by no means simple. Nevertheless I wish to derive the need for such measurements from results of American investigations which have been obtained within the scope of the 'Air Traffic Controller Health Program' effective since 1966. In so doing I think of the methods of biological supervision of astronauts which obviously have been specifically well developed, but I refrain here from going into details in this respect . The aforementioned American program is an amplification of the 'Airman Examination Program' with specific modifications towards expanded usability as a measurement for the effects of 'long-term stress'. It has here been attempted to develop an objective standard that tries exactly to describe the effects of stress on the human organism and in particular onto the controller at work.

It is absolutely impossible at this point to present any details of the investigation program set up at a tremendous scale, but of which no decisive ultimate results have been obtained so far. I have to confine myself to enumerating a number of investigation parameters which give an idea of the broad scope of the program and to render a few general conclusions for which I am indebted to a personal interview with Dr. H.W. WITHERS, Chief of the Aeromedical Services Division of the FAA at Washington. A remarkable fact is that a questionnaire also plays a great part within the scope of these investigations, i.e. "the 16.P. F.Test" - the "Sixteen Personality Factor Questionnaire". In the realm of psychological questionnaire preparation this is a reply, framed with great attention to detail, in order to answer the question for a test that yields the most comprehensive information concerning most of the personal traits in a minimum of time. The main objective and value of this test can be seen in the assistance it can lend a psychiatri- cal surveillance and health program. Among important parameters of the 'Air Traffic Controller Health Program' I wish to mention the relations between the age of the controller, the years of work he passed with the authority, the influence of the salary group, the amount of experience, and the professional performance rate of the controllers (15), as well as general studies concerning the aging of aeronautical personnel (16), the investigation of stress-related symptoms on active control personnel (ATCS = Air Traffic Control Specialists) as contrasted to other technical ATC staff (16). To mention at least one significant result it turned out that ATCS people declared to have more headaches, indigestion, chest pains and ulcers than non-ATCS personnel. It further turned out that e.g. ATCS radar journeymen exhibit predominant ECG abnormalities and higher prevailing hypertonia than ATCS personnel 'in general. An additional load from radar observation (18) is here in evidence.

Also investigated is the question whether a given stress is 'job-related' or 'home-related' when a controller exhibits increasing stress effects or premature giving out. This is a sociologically important problem. 9 -5

The Americans admit (14) that, if it is true that 20 years of ATC work tax a human being more and make him literally age faster than 20 years of less stressing work this is a case for individualized career handling which, under these circumstances, the ATC specialty would deserve. I now wish to give an itemization by medical causes of an investigation that took 25 months and resulted in 147 professional disqualifications of controllers (Fig. 5). This reveals that diseases that can be attributed to stress have been detected at least in three groups which combine to more thm half of the controllers disqualified during the 25-month period. Subsequently a few figures out of the 16.P.F. questionnaire drive: a total of 12,500 controllers have been tested. 1.2%, i.e. 151 controllers, revealed a certain amount of stress effects. Further medical checkups revealed a need for a complete psychologicallpsychiatrical checkup of 90 controllers. Significant psycho- neurotical diseases were detected in 31 instances, but it was only in 15 cases that these diseases were ' rated serious enough for retirement from active control duty. However, these are data of the past. In the future, service disqualifications as a consequence of stress will go up. It has turned out that, if controllers are employed after a correspondingly correct psychotechnical employment checkup (22,23,24) they will obtain more favorable results in such tests than ordinary people. A highly significant fact turned out to be that controllers were found to he more intelligent, realistic, conscious and tough and also to possess more self-discipline and control while exhibiting less anxiety or anxious insecurity than ordinary average people. Let me sumnarize my speech in two basic statements: 1. The technical evolution of control aids of radar engineering and its periphery fails to keep , abreast with the growth of traffic, and 2. The active and decisive capability of the human controller with its full load of responsibility and time pression, in any form conceivable, will remain a decisive factor in air traffic control for a long time to come despite all automation. In the interest of air traffic security it must therefore be demanded that this precious living asset - throughout the world and not only with a few aeronautical administrations - is always given the best of anthropotechnical and human care even in the future, and that all facilities of the medical art are turned to use for its benefit.

t 9-6

% t recognition quota 90

10 50 100 500 1000 stimuli (per 30 minutes) -e Relationship between stimulation rate and recognition quota Fig. 1

3ifferences in the Performance of Observation ?elated to Stimulation rate

High Stimulation Low Stimulation Rate Rate ( 240 stimuli / hr (24 stimuli/hr)

Percentage of overlooked echoes 29 Yo 15.8Olo (Omissions)

Avemge recog - nition time in 712 1176 milliseconds

Trend slight increase sharp increase

Errors in 'lo (Response without 7 O/O 34.5% stimulus) Fig. 2 9-7

A 100 - I 90 - Mean reco nition 80 - time for CO9 lision headin s and its 70 - zone o9 dispersion 60 - 50 - 40 - 30 - 20 - 10 -

01 1 1 1 I I I 1 30 60 90 120 150 180 210 240 Fig. 3 Observation time - minutes

Fig .4 Annotations to Fig. 4. Terminal Area Chart

Traffic Situation: 5 departing aircraft between 1306-1314 and 5 landing aircraft between 1328-1334

Inherent static information on the control strips: 1. 2. 3. 4. 5. 6. 7. ND 180 DM B1 DF 120 1306 1320 1335 BE 190 DM B1 DF 140 1308 1320 1334 727 440 DM B1 DF 200 1310 1318 1325 outbound 707 465 DM B1 LL 340 1312 1320 1327 737 460 DM 61 DL 240 1314 1322 1328

1. 2. 3. 4. 8. 6. 9. 10. 707 470 PO 86 DM 330 1312 1318 1322 1328 BAC 460 LL 86 DM 290 1314 1320 1324 1330 CV 200 LL 86 DM 150 1307 1320 1325 1334 inbound ND 180 DS 86 DM 110 1305 1320 1326 1336 727 440 AM 86 DM 310 1317 . 1324 1329 1333

Meaning of numbers 1-11: 1. Type of aircraft 2. True airspeed in knots 3. Point of departure, route, point of des i nation 4. Flight level 5. Departure time 6. Time passing WALDA 7. Time passing DINKELSBUEHL 8. Time passing MLEN 9. Time passing MIKE 10. Landing time 11. Flight path according to arrows

Conclusions to be drawn and decisions to be made over departing aircraft:

Aircraft 1 Climbing via standard instrument departure route to WALDA. Nord Atlas

Ai rcraf t 2 Climbing on runway heading to 4000 feet then right turn to heading 350' to Beechcraft flight level 130 before setting course to WALDA. Radar vector is necessary due to preceeding yellow, departure. Aircraft 3 Right turn imnediately after take off to heading 350' to flight level 150 Boeing 727 before turning left to WALDA. This radar vector brings him clear of aircraft I ,(yellow) and also to a paralell course of aircraft 2 (blue) until flight level 150, which is above aircraft 2. U, Aircraft 4 Climbing on runway heading to FL 60 then right turn to heading 030' until Boeing 707 passing flight level 150, then left turn to heading 320° until passing flight level 260 before turning left to DINKELSBUEHL. Radar vector is necessary to climb him above all preceeding aircraft and aircraft number 5 (brown). )))), Aircraft 5 Climbing on runway heading to flight level 60 then turning right to heading Boeing 737 030° until intercepting radial 160° from WALDA VOR. Aircraft has to expedite climb until passing flight level 130 on account of aircraft 1 (yellow). Radar vector is necessary due to preceeding aircraft 4 (red). n , 9-9

Conclusions to be drawn and decisions to be made over landing aircraft: Aircraft 1 Descending to FL 160 (further descent momentarily not possible due to same Boeing 707 direction landing aircraft 3, blue 44 ) to sake sure that flight level 190 is crossed not later than 15 NM before WALDA on account of departure 3 (green ) at flight level 200 when crossing WALDA. Further descent after passing MIKE NOB on heading 150° to initial approach altitude. Number 1 for landing. Aircraft 2 Descending to flight level 170 (further descent not possible due to landing BAC 1/11 aircraft 1, yellow 4 and landing aircraft 3, blue a ). Leaving FL 170 after MIKE on heading 150' to initial approach altitude: number 2 for 1andi ng . Aircraft 3 Leaving MIKE on heading 130" descending from flight level 150 to altitude Convai r 5000 feet. Aircraft will be vectored by radar to be number 4 for landing. Aircraft 4 Leaving MIKE heading 110' descending to flight level 60. Aircraft will be Nord Atlas vectored by radar to be number 5 for landing. Aircraft 5 Descending to initial approach altitude, leaving MIKE on heading 150'. Boeing 727 Aircraft is radar vectored clear of blue. 44 and green 444 , landing number 3. This typical traffic picture can be solved only by using radar, otherwise delays and holdings are unavoidable. The controller also has to take into consideration other factors as the available airspace, which in this example, using the.Munich area, is very limited due to a lot of military airfields and their departure routes, also the obligation to use standard departure routes whenever possible, on account of noise abate- ment procedures etc. Finally &e controller is overloaded in giving traffic information of unknown targets on conflicting courses to all aircraft under his control. Diagnosis of Controllers Dis ualified for Medical Reasons (1966-19689 ' Hypertensive cardiovascular disease 24 Myocardial heart disease and coronary thrombosis Valvular heart disease Other heart (arrythmias) 3 Pulmonary disease, chronic 3 Pulmonary infections disease ( Tbc.) 1 Pulmonary, other ( pneumofhomx) 1 Gastrointestinal disorders, incl. peptic ulcer Diabetes mellitus 4 Other metabolic disorders 2 Drugs (requiring use of disqualifying dosage levels) 4

Neuropsychiatric l3 18 Neurological 5 } Renal ( GU) 2 Visual deficiency 30 Hearing deficiency 26 Otitis media 3 Arthritis 2 Other neuromuscular skeletal 1 Hernia 2 Malignancy (?I 2 Miscellaneous -1' total 147

I Fig.5 9-1 1

References 1 C. H. BAKER Man and Radar Displays, New York 1962

2 L. M. FENNING Eye Protection for Observation Opt. Joirrn. and Review of Optometry, Dez. 1960

3 H. J. JERISON Experiments on Vigilance R. A. WALLIS WADC-TR-57-318 Aero. Med. Lab. Wright Air Development Center Wright Patterson AFB, Ohio, 1957

4 H. SCHMIDTKE Leistungsbeeinflussende Faktoren im Radar-Beobachtungsdienst Forsch. Ber. Nordrh./Westfalen Nr. 1736 Westd. Veriag, Koln U. Opladen, 1966

5 N.H. MACKWORTH Researches on the Measurement of Human Performance, London, 1950

6 H. SCHMIDTKE Untersuchungen uber die Reaktionszei t bei Dauerbeobachtung H. C. MICKO Forsch. Ber. Nordrh./Westf, Nr. 1360 Westd. Verlag, Kijln U. Opladen, 1964

7 S. RATCLIFFE Mathematical Models for the Prediction of Air Traffic Controller Workload The Controller 9 (1970), No. 1, p.18 ...22 8 S. RATCLIFFE Congestion in Terminal Areas Journ. Inst. Navigation 17 (1964) p.183 ...186 9 G. A. CHANDLER ATC Capacities at Sydney Kingsford Smith (Mascot) Airport and Control 1 er Saturation Levels Journ. Inst. Navigation 18 (1965) p.42. ..48

10 M. ROSENSHINE The Application of Automation to the Solution of Air Traffic Control Problems FAA Third International Aviation R. & D. Symposium - Automation in Air Traffic Control, Nov. 1965 11 J. LEPLAT Analyse des Processes du Traitement de 1 'Information chez A. BISSERET le Controleur de la Navigation Aierienne English translation in The Controller 6 (1966) No.1 p.13 ...22 12 ARAD, BAR-ATID FAA. SRDS, June 1964 et. al.

13 G. D. JULITZ FAA SRDS, June 1965

14 H. W. WITHERS Reflections in the Doctor's Eye or a Two J. Z. DAILEY Year Look at the Air Traffic Controller Health Program Internal FAA-Report, 1969

15 B. B. COBB The relationships between chronological Age, Length of Experience, and Job Performance Ratings of Air Route Traffic Control Specialists FAA AM 67-1 June 1957

16 A.E. WENTZ Studies on Aging in Aviation Personel FAA AM 64-1 Georgetown Clinical Research Institute, Wash.D.C. , Aug. 1964

17 J. D. DOUGHERTY Se1 f-reported Stress-rela,ted Symptoms among D. K. TRITES Air Traffic Control Specialists (ATCS) and J.R. DILLE Non-ATCS Personel 1 Aerospace Medicine, Oct. 1965 p. 256...259

18 J. D. DOUGHERTY Cardiovascular Findings in Air Traffic Controllers Aerospace Medicine, June 1965 p.26. ..30 19 J.W.H. KALSBEEK Measurement of Mental Work Load and of Acceptable Load: Possible Applications in Industry The Int. Journ. of Production Res. 7 (1968) No. 1

20 J.W.H. KALSBEEK Objective Measurement of Mental Workload; Possible Application to the Flight Task. Preprint, Symposium AGARD Aerospace Medical Panel , Brooks AFB, Texas, May 1969 9-1 2

21 H. J. ZETZMANN Zur System-Philosophie der Flugsicherungskontrol le Luftfahrttechnik 5 (1959) Nr. 12, p.316. ..324 22 H. J. ZETZMANN Der Mensch als informationsverarbeitendes Glied im F1 ugs icherungs- Kontrol 1dienst Nachr. techn. Fachberichte, Fernwirktechnik IV (1961) p.43.. .49

23 , H. J. ZETZMANN Der Flugleiter - Mensch oder Automat Der Flualeiter 7 (1960) No. 2 p.2 ...7 24 H. J. ZETZMANN Psychological Aptitude Tests for Air Traffic Control Officers The Controller 1 (1962)'No. 2 p. 5...7 25 L. HEILMEYER Lehrbuch d. spez. patholog. Physiologie G. Fischer Verlag, Stuttgart 1968 26 S. RATCLIFFE Automation in Air Traffic Control The Controller 3 (1970) No. 1, p.6 ...11 10

WORK-REST CYCLES AIR TRAFFIC CONTROL TASKS

V.D. Hopkin Royal Air Force Institute of Aviation Medicine Farnborough, Hampshire, England. 10

SUMMARY

There is no established practice or international agreement on the total weekly hours worked in air traffic control tasks, or on the optimum lengths of watches or shifts. Tasks range from those with a high vigilance component, where efficiency is associated with short work periods and frequent brief rests, to those requiring long hand- over periods, where unacceptable double-manning would occur if the work periods were short. Continuous eight hour shifts, with meals at the working position, are not unknown; these shifts may include high workload, though not all the time.

The air traffic controller has little influence on his own workload. Traditionally, his colleagues expect him to deal with whatever traffic enters his sector. He does so, at the cost of hard and sustained effort when workload is high, which sometimes results in extreme tiredness which may prevent him from relaxing after the end of his shift.

The effects of work-rest cycles on performance have been the subject of much discussion in air traffic control circles, but of relatively little scientific work. What has been done is reported; what could be done is suggested. 10-1

Air traffic control normally provides a service for twenty-four hours every day of the year. It is therefore taken for granted by controllers that their conditions of employment include shift work, unusual work-rest cycles, and periods of work while most other people are not working, such as on public holidays when the air traffic controller may have exceptionally high workload. In this paper, the concept of work-rest cycles has been interpreted broadly, to include shift work, schedules of work extending over several days, and short breaks within a single period of work.

The way in which the work is divided into shifts in air traffic control varies greatly in different parts of the world. The division is influenced to some extent by factors such aa workload but mainly by other factors which have nothing directly to do with the task being performed. In many countries the controller is a government employee, and he is therefore expected to work the same total number of hours as other government employees, with extra work counting ae overtime. Similarly the lengths of watches are often governed more by current norms of working hours in a particular country than by the length of time the task can be done efficiently without a break.

Common Shift Schedules.

A survey conducted by S henkman about eight years ago on conditions of employment in air traffic control throughout the worldPl) highlighted the very different national practices in determining working conditions, in specifying hours of work, in defining overtime, in scheduling shifts, in dealing with night work, in requiring weekend and holiday work, and in planning breaks and rest periods. This remains the most thorough survey of its kind. Although many countries have introduced detailed changes in conditions, its broad findings are still true. The sheer diversity of practices in different countries is in itself a clear indication that they are not based on scientific evidence on what would be most efficient but rely much more heavily on what is practical, convenient, or traditional. This cannot be attributed to any wilful disregard of scientific findings or to a failure to implement them. On the contrary, apart from one or two isolated studies of detailed features of the problem the necessary work to assess the effects of work-reet cycles on air traffic control tasks has never been done. Findings on the effects of work-rest cycles on other jobs may at best be treated as hypotheses for testing in air traffic control. They should not be extrapolated to air traffic control since no scientific work has been done on jobs and work schedules sufficiently similar to those in air traffic control to warrant such extrapolation.

In most countries work-rest cycles in air traffic control follow a pattern in which a three or four shift system is worked which re-cycles after a fixed number of days, commonly three or four. In such shift cycles, the controller does not work the same shift on two consecutive days. He never works for several days or weeks on the same day or night shift, as is common practice in industry. The problems of adaptation are therefore not normally the same as those enoountered in industry and typical studies showing the adaptation of diurnal rhythms to a shift system after several days do not therefore apply to air traffic control which does not normally have that kind of shift system.

The actual lengths of shifts vary greatly between countries and also within a single shift pattern in a given country. In some countries, admittedly where the traffic is less dense than it is in most of western Europe and in the United States, it is not unknown for continuous shifts lasting over twelve hours to be worked. This does not imply that the controller is actively talking and controlling aircraft for every minute of such a shift. However, he is continuously on watch in the sense that meals and refreshments are often brought to the controller and he cannot leave his working position for long enough to eat elsewhere. More commonly where there is a long shift, for example a twelve hour night shift it includes an official rest period, often of two hours duration, which unofficially may be extended if traffic conditions permit. A further factor is that although some hand-over procedure lasting for a few minutes is often necessary when shifts change, countries vary in whether this is officially recognised by being included in official working hours.

Factors Relevant to Work-Rest Cycles.

C It is possible to list a very large number of factors relevant to the scheduling of work-rest cycles. These are too numerous to consider here individually, but they can be claesified under the following main headings.

1. Efficiency of Task Performance

T e e is an extensive literature on the relationship between human performance and work-rest cyclesAr . The paramount consideration is that the work-rest cycles must maintain the efficiency of air traffic control. It could be argued that work-rest cycles should be chosen solely to make the safety and efficiency of air traffic control as good as they can be. Although this is agreed to be the main aim, in practice it cannot be the only aim and should not be interpreted narrowly since certain other factors are also important, yet tend to be incompatible with it. If this aim were taken literally as the sole purpose of work-rest schedules then the total weekly hours which controllers work would probably be very short, the total lengths of shifts would be much reduced, a mmregular shift schedule might be imposed, younger controllers would probably do a dispro- portionate amount of the night work, and numerous similar consequences would follow. Many of these would be impractical to administer, exceedingly costly to implement, and unacceptable to the controllers themselves because they would violate professional practices and canons of conduct. 10-2

The aim must therefore be to ensure that any schedule of work-rest cycles does not compromise safety standards, increase delays, or disrupt traffic flow. It is probably neither desirable in principle nor attainable in practice to search for the precise optimum work-rest cycle for maximum system efficiency. Even if such a schedule exists, it is probably unacceptable on other grounds. Any intention to establish its existence would in any case be thwarted at an early stage by the lack of sufficiently quantitative, exact and internationally agreed measures of what constitutes efficiency in the performance of most air traffic control tasks. Certainly the factors to be taken into consideration are numerous and all would have to be quantified; equally ceFtainly they are not all of equal importance so that some weighting would be needed. Different national conditions, procedures and facilities for air traffic control would mean that measures and weighting6 would have to be modified for different countries. In the present state of our knowledge of air traffic control tasks and their quantitative measurement, the precision with which task performance would have to be measured in order to specify optimum work-rest cycles cannot be attained and the effort to establish optimum schedules derived solely from performance measures is not likely to be fruitful and not likely to be justified. This is not an argument that the effects of major differences in work-rest cycles on performance cannot be measured; they can be, and should be, studied. It is an argument that the necessary performance measures are probably not available now to permit valid and reliable differences between basically similar work-rest schedules to be measured in quantitative terms of system efficiency.

2. Characteristics of the Operator

To some extent work-rest cycles have to be adjusted in relation to characteristics of the operator other than his task performance. Recently there has been considerable emphasis on the physiological effects of shift work on the operator, particularly on the scheduling of work-rest cycles to minimise the effects of physiological changes. Trumbull(3) was able to suggest about 50 fluctuating functions within man affected by work-rest cycles and in turn influencing his performance. Physiological effects are of sufficient importance to be treated seriously in devising the schedules for pilots crossing time zones and many of the factors relating to the pilot relate also to the controllers, since neither is following a regular schedule of work within each twenty-four hour period. A further factor relating to the individual operator is the suspected inter-action between the work-rest cycle and the age and efficiency of the operator. There is some scientific evidence to demonstrate that this relationship exists in air traffic control (4; 5) and much anecdotal evidence of the reduced adaptibility and greater social disruption of shift work with increased age. People often think that they work less efficiently at night, but the practical importance of this might be less in air traffic control than in many industrial environments. The controller's workload is usually much less at night than during the day dthough it could be forcibly argued that the first day shift should come on duty before the traffic loading begins to rise substantially about breakfast time. The inter-action between the compensations such as extra pay, given to all controllers working at night, and individual differences in the efficiency and adaptability of controllers has not apparently been studied at all.

3. Task Characteristics

The effects of work-rest cycles on performance depend considerably on the nature of the task. At one extreme, performance of many vigilance, search and monitoring tasks is probably at its most efficient when the operator has frequent breaks, which may themselves be short. However, it is one thing to show in the laboratory that a work-rest cycle of half an hour work followed by five minutes rest is the most efficient way of dividing a one and three-quarter hour period (61, and quite another matter to try and implement such a work-rest cycle in any operational environment, where the physical change-over of operators can cause disruption and the administrative arrangements become unwieldy. In any case there is no guarantee that a finding obtained in the laboratory over a two hour period will hold true when the same task is being done for months on end.

Current and future air traffic control systems contain some tasks, such as the routine up dating of information by qual and automated means, which require a brief hand-over period but many tasks require a more protracted hand-over. Evidence has been obtained in a simulated air traffic control task (7) that a significant but short term decrement occurs at hand-over which can be reduced but not eliminated by a hand-over period with some form of joint control by both controllers. This should be treated as a hypotheses for testing in current systems rather than as a finding which necessarily applies to all tasks in them. Evidence of this kind however indicates that an appreciable hand-over period is desirable and this is not readily associated with very short work periods.

For many air traffic control positions each aircraft is under the control of an en-route or terminal area controller for ten minutes or quarter of an hour or longer, so that some of his units of work extend over a considerable time period. Thus, the continuous nature of air traffic control, and the amount of background information to be learned about a developing air traffic situation before control of it can be assumed, tend to encourage fairly long work periods, certainly of the order of two hours or more. It is not clear from current knowledge whether this is in the interests of system efficiency. The task loading is obviously relevant here but this tends to be confounded with any schedule of work-rest periods because at most airports there are very large and relatively stable fluctuations in traffic loading associated with time of day. The effects of continuous work periods on the ability to perform air traffic control tasks, with their large 10-3

components of decision making and problem solving, are not clear.

An important confounding factor is the traditional attitude of the controller that he accepts traffic entering his sector no matter how busy he becomes. This is a part of his expected and traditional behaviour, tempered by the fact that any refusal to accept a particular aircraft may lead in its turn to more workload for himself and for others than would have occurred had he accepted the aircraft in the first place. As a result performance measures may not give a good indication of the effects of the work-rest cycle, because the controller may maintain a satisfactory performance at the cost of increased effort which may be assessed not in any performance scores, but by physiological measures while he is doing the task, and by subjective impressions of fatigue. Certain other measures such as the inability to forget about his work when off duty or difficulty in sleeping properly when he has been over-worked may also be better than performance measures as indicants that the task loading or the work-rest cycle, separately or in conjunction, are imposing excessive demands on the controller. This factor is a further indication that measures of performance may in themselves not be an adequate guide to assess the effects of work-rest cycles. On existing evidence perhaps the best performance measure is likely to be the proportion of time spent on long term planning tasks. When task loading becomes excessive in an air traffic control context the controller's actions may be determined almost entirely by immediate circumstances, SO that actions are seldom the result of long term planning and anticipation (8). This should also be treated as a hypotheses rather than as a finding.

4. Social Factors

To determine work-rest cycles solely on the grounds of system and job efficiency is to neglect their social implications. One of the reasons why the practice in industry of working several consecutive nights is not followed in air traffic control is quite simply that most controllers are against this, mainly because of its disruptive effects on social and family life. Many controllers in existing systems value highly their days off and the opportunities for family outings. They also find that the current shift schedules permit a reasonably normal social life to be planned. One important factor in relation to this appears to be age although much of the evidence for this is anecdotal. If a controller has been on night shift during which he has officially had a two hour rest period and perhaps in practice has had three or four hours rest, younger controllers seem much more able to do without sleep until the following night and have a normal day's activity with their family before sleeping. Older controllers tend, after such a night shift to feel the need for sleep as soon as they get home and therefore to spend part of their rest day asleep. Not surprisingly it is common to find that night work and shift work is often more acceptable to younger controllers than it is to others. The evidence for this is largely anecdotal but it would be relatively easy to obtain more scientific evidence on this point. The problem arises of what action should be taken if it is found to be true. The logical conclusions of allowing younger people to work more at night (and hence be paid more) would be resented. In favouring one work-rest schedule over another a very important factor for many controllers is the effects of the work-rest schedule on their home life, and particularly the length of continuous free time that they have at home within any given short period such as a fortnight.

A further important factor related to the timing of work-rest cycles is the availability of off-watch and other facilities. One reason often quoted for avoiding shift changes at midnight is the lack of public transport at that time; this factor is easily exaggerated since most personnel in air traffic control have their own cars. However there is often a preference for a longer night shift in order to extend its beginning and end into more normal working times. A controller may not reach home for an hour or so after his shift officially ends. Availability of canteen and rest facilities is important. There is some evidence that work may improve when coffee, snacks, sweets, etc. are available whenever the individual worker wants them (9). Factors of this kind may have little direct bearing on the relation between work-rest cycles and efficient task perfornance but have an important bearing on any attempts to implement recommendations derived solely from performance measures, since such recommendations are very unlikely to concur with the long night watches which may cottrollers prefer.

5. Standards of Performance

In air traffic control controllers set themselves high standards of performance. They are acutely aware of any occasions when in their own eyes they have not performed the task quite as well as they could have done even although their performance has ensured safety and been acceptable to everyone else. This factor again hinders the discrimination by performance measures between different work-rest cycles although it might aid such discrimination in terms of the controller's own satisfaction with his work. There is a growing body of opinion that the primary relationship is that between job satisfaction and the effort made rather than between job satisfaction and the performance achieved (10). If this is so it is possible to reduce too far by automated aids the effort needed to perform certain tasks in the sense that one would expect that if effort were reduced substantially it might lead to reduced job satisfaction. A factor in current attempts to adjust work-rest schedules and task loading to make the controller's task easier is that there comes a point when the desirability of doing this should be questioned. The controller's task is a mixture of periods of relative boredom and little activity with periods of very high task loading indeed, after which he may report that he only managed to maintain his performance because he knew that a lull would eventually occur. If the job is made less demanding and requires less effort it may also become less satisfying. A major factor in deciding the optimum work-rest schedules is the well-being of the operator but this should not necessarily be 10-4

equated with making his task easier. Existing evidence derived from other sources (10) suggest that the controller's job should be fairly difficult, with clearly defined short-term goals.

'Previous General Work.

Progress in the study of work-rest cycles and their effects on performance has not on the whole be'en rapid during the last few years. Often the need to justify work-rest cycles in terms of demonstrated performance decrements or improvements has led to difficulties in tasks where appropriate precise quantitative measurements to measure such decrements are not always available. A paper by Chambers (11) surveyed many of the reports produced by the Industrial Fatigue Research Board between the two world wars. This shows that many of the principles for judging the effectiveness of work-rest cycles have been established for 40 years or more and that the history of adjusting hours of work and rest as a means of improving efficiency extends back for at least fifty years. This paper is a useful source of hypotheses which have never been tested in an air traffic control context or indeed in most military contexts but miEht well re-pay study. One difficulty is that the optimum number of hours for a task can normally be established validly only by observation over a long period and that the process of observation or measurement itself is likely to distort what is being measured sufficiently to invalidate some of the findings. This is a factor which from the days of the classic Hawthorne experiment (12) has been acknowledged but in practice is often still ignored. The long term adaptation processes associated with changes in work-rest cycles areintrinsically difficult to study and have therefore often been ignored. It has been known for a long time that the relationship between hours of work and production does not depend simply on factors such as "fatigue", whether this is defined by performance, in physiological terms or subjectively, but that many less quantifiable factors,such as motivation and morale and relations with ones fellow workers, may have substantial effects. These are prominent in most air traffic control contexts.

Much work on rest pauses has followed scientific methods by assessing the effects of known work-rest cycles with controlled work periods and imposed rests of known duration. However, voluntary rest pauses are common in many jobs, and can defeat such precise control of variables. In an air traffic control context the workload is seldom constant for any protracted period. Substantial fluctuations of task load over relatively short periods can make it very difficult in practice to isolate all formal rest pauses from the informal ones which the operator takes whenever the opportunity arises. A common finding has been that, when a rest pause is introduced, activity increases and performance improves not only after the rest pause but also before it. The end spurt in a shift may be an example of this. A practical consequence is that measurements of the effects of re& pauses should not be confined to the level of performance achieved after the rest but the level of performance achieved throughout the whole work-rest cycle must be the main means of assessing its effects.

Further hypotheses derived from this early work reported by Chambers(ll)> are that rest pauses may be particularly effective in repetitive monotonous work and that the effects of work-rest cycles are normally most readily measured when the task is highly dependent on what the operator does. A conclusion reached by Chambers from his survey was that the existing findings tended to raise more problems than they solved. Much of the work has been empirical and task specific, and work on the best ways of utilising rest pauses is lacking. The relationship between rest pauses ayd team work has not been adequately explored.

Previous Air Traffic Control Work.

If we consider the evidence available specifically on air traffic control, the relatively sparse existing literature can be summarised. A paper by Cobb(5) reviewed some Canadian and other work on the effects of shifts from several points of view. The question of the long term effects of shift work in relation to health has not been adequately studied but there is some evidence of a relationship between long term shift work and subjective impressions of illness. A study (131, on self-reported stress symptoms and shift rotation suggested that there was some relationship but not a simple linear one, because short and long intervals between successive shifts tended to produce more self-reported stress symptoms than intermediate intervals. In another context Rahg(l41, studied illness incidence among personnel at sea in war and peace zones but found that although illness was to some extent associated with risk, in the sense that the greater the risk the greater the incidence of illness, numerous other factors including race, age and anxiety over health were also important. There is supporting evidence on the importance of age in relation to stress related symptoms (4). There is some evidence that in the United States air traffic control may be more stressful than other occupations in so far as it is associated with a higher incidence of health problems, such as headaches, chest pains, indigestion and ulcers (15). A factor here is that those who volunteer and are willing to fill in questionnaires are likely to be themselves more prone to health defects than those who do not (16). This study on cardiovascular findings in air traffic controllers found lower hypertension amongst air traffic controllers than amongst non air traffic controllers and a greater incidence of ECG abnormality among controllers than non controllers. However, these differences were small and scarcely warrant consideration as being statistically significant.

Tentative conclusions which most people currently accept in relation to the effects of work- rest cycles appear to be that shift work itself does not appear to cause directly any occupational disease or affect morbidity or mortality. Examples of reported cases of such effects in the I

10-5

literature tend to be isolated. However, certain latent disease conditions may be aggravated by shift work, particularly individuals who have difficulty in adaptinq to the work-rest cycles. Sufferers from sleeplessness, nervous illness or digestive complaints may be much less suitable for shift work. There is a considerable body of anecdotal evidence that the ability to adapt to shift work decreases substantially with age in contexts such as air traffic control, particularly after the age of fifty or thereabouts; in particular that individuals of this age group should not at that age start to do shift work if they have not previously been accustomed to it. It has been forcibly argued (17) that air traffic controllers should have an earlier retirement age, a practice which is now gaining wider acceptance.

There are substantial individual differences between people in their ability to adapt to shift work, to the extent that some people may never be able to do so completely. The time required to adapt varies also with the task but on ;he whole adaptation is quickly lost. Much of the work in industry on shift work does not apply to air traffic control because in industry the period of shift work is generally between one and four weeks whereas in air traffic control the cycle of shifts is repeated every few days. The effects of working shifts on the attainment of goals such as promotion in air traffic control may well be of importance.

One problem associated with studying air traffic contrcl tasks is that detailed job descriptions of current air traffic control tasks are seldom available because the necessary work has not been done. Numerous attempts at classifying the elements of air traffic control tasks have been made but none has proved sufficiently reliable, valid and practical to gain wide acceptance. Controllers at a busy airport have been reported as feeling tired and when the work that they do is studied this is not surprising. A study reported by Grandjean (18) established that controllers at Zurich Airport had a high mental load. This was supported by the subjective inpressions from the controllers and by a job analysis showing that a high proportion of the working day involved activities demanding concentrated visual attention and that other substantial proportions of the day were spent in speech communication and in writine notes. This sort of technique might be extended to study the effects of work-rest cycles and also the self-rating techniques used may be of value although they would appear to be measuring mainly a single general factor of'Yatipe1' rather than the numerous postulated dimensions. In many tasks the study of fatigue is associated with lost motivation to work but the effects of this in a situation, such as air traffic control, where the work has got to be done have not been thought through. A loss of motivation is not necessarily always apparent to others (19).

In air traffic control motivation may remain high because the controller feels that to meet his own professional standards he must perform adequately no matter how tired he feels. It is common to hear reports of ccntrollers towards the end of a night shift being aware that they were performing at less than their best level, but this coincides with a period of low task loading and has no unacceptable consequences. Performance in a stressful operational environment would be expected to be poorer than under comparable laboratory conditions, particularly with a difficult task (20). The need to maintain an acceptable professional standard of performance despite tiredness may indicate that measures of the effects of different work-rest cycles may be more likely to appear in subjective assessments and in physiological reasures than in measures of system or operator performance. Some exploratory studies of physiological measures into air traffic control have been made. In addition to those already mentioned a study by MacKenzie and his colleagues (21) suggested that psychogalvanic skin response and heart rate have sufficiently discriminatory value in relation to traffic loading that they may be worth exploring as criteria for measuring workload and for measuring the effects of work-rest cycles on performance. This work is being followed up but can be expected to encounter the sort of difficulties in taking such physiological measures as heart rate which have been encountered in work on pilots. For most purposes simple heart rate measures, averaged over an appreciable period of time, are insufficiently sensitive to discriminate between most of the relevant factors.

The present knowledge on the effects of work-rest cycles in air traffic control can therefore be summarised as follows. The amount of acceptable scientific work on work-rest cycles in air traffic control is very small indeed. The paper by Schenkman showing the very large differences in national practices is in itself a testament to the lack of scientific evidence and to the failure to use what evidence exists in assessing what work-rest cycles are most appropriate. Vhen work- rest cycles are changed this may be done when most of the people concerned do not want to chanee and when the evidence favouring the proposed change is tenuous. The situation is complicated by the wide discrepancy which can occur between the formal rest periods and the actual ones, particularly in an air traffic control context where the rest pauses which an operator may safely take are more dependent on features of the task such as the traffic loading. For this reason codes of official practices in relation to work-rest cycles must be interpreted with caution. There is clearly a case for comparing the type of work-rest cycle normal in air traffic control, where the cycle is complete after a few watches and is repeated everj few days, with the type of work-rest cycle normally found in industry where the same shift is often worked for several consecutive weeks. The adaptation problems are quite different for these two situ-ttions adcare must therefore be taken in extrapolating any findings from one to the other.

Most of the evidence available is very specific to particular tasks in particular contexts. Although this does not provide much evidence directly applicable to current air traffic control systems it can be a useful source of hypotheses to test in such systems. A profitable line of research might be to take some of these findings and see whether or not they do remain true in air traffic control environments. These findings relate to many factors including the nature of the task, the detailed structuring of the work-rest cycle, the length of rest periods within each work period and the impact of numerous extrane'ous factors such as off-watch and canteen facilities and the family circumstances of the controller. One of the most important factors in relation to work-rest cycles is clearly age, particularly in its interaction with the ability to adapt to shift work. The consequences of this on the task and on the individual operators should be studied, particularly in relation to career prospects and the ways these relate to shift work. Current evidence from numerous sources suggests that it'may be profitable to emphasise subjective measures and impressions and collect these formally, and to study physiological variables as well as to measure task performance in relation to shift work. The nature of air traffic control makes it difficult to obtain suitable quantitative measures of performance. Air traffic control tasks tends to make the controller work harder in order to compensate for potential performance decrements rather than to maintain his existing effort and accept a decrement in performance.

For certain tasks there is probably a conflict between what is desirable, which would lead to relatively short periods of work and relatively short rest periods, and what is practical, which would lead to long continuous periods of work with long rests because of factors such as the need for a fairly protracted hand-over. The conflicting requirements of these factors should be explored with a view to finding an optimum which would not necessarily be the same for different kinds of controllers such as terminal area and en-route controllers and would not necessarily lead to equal shift lengths. In doing all this it should not necessarily be assumed that to minimise the workload of the controller or to minimise the effort he needs to make are necessarily desirable ends to be achieved, since too little workload or too routine tasks mag lead to boredom and too little effort may reduce job satisfaction. 10-7

REFZRENCES

1. SCHENKMAN, J. Conditions of employment in Air Traffic Control Service. The Controller 2.4. 1963, 5-20.

2. RAY, J.T., MARTIN, O.E. & ALLUISI, E.A. Human performance as a function of the work-rest cycle. Washington, D.C.: National Academy of Science - National Research Council Publication 882. 1961. 3. TRUMBULL, R. Diurnal cycles and work-rest scheduling in unusual environments. Human Factors. 8.5. 1966. 585-1398.

4. HAUTY, G.T., TRITES, D.K. & BERKLEY, W.J. Biomedical survey of AE facilities. 2: Experience and Age. Oklahoma City, Okla: Federal Aviation Agency, Office of Aviation Medicine Report No. AM-65-6. 1965.

5. COBB, B.B. Commentary regarding research on work shifts, work shift rotation, stress and ageing effects. Oklahoma City, Okla: Federal Aviation Agency, Civil Aeromedical Institute. Un-numbered Report 1966.

6. BEEUM, B.O. & Lm, D.J. Vigilance performance as a function of interpolated rest. J. appl. Psychol. 46.6. 1962. 425-427.

7. KIDD, J.S. & KINKADE, R.G. Operator change-over effects in a complex task. Columbus, Ohio; State University Research Foundation. WADC Technical Report 59-235. 1959.

8. KIDD, J.S. Some sources of load and constraints on operator performance in a simulated radar A.T.C. task. Wright-Patterson Air Force Base, Ohio: Wright Air Development Division Report WADD - TR - 60-612. 1961. 9. CASS-BEGGS, R. & EMERY, F.E. Food, drinks and sweets in the reduction of industrial fatigue. Occup. Psychol. 39.4. 1965. 247-259.

10. SMITH, P.C. & CRANNY, C.J. Psychology of men at work. AM. Rev. Psychol. 19. 1968. 467-496.

11. CHAMBERS, E.G. Industrial Fatigue. Occup. Psychol. 35. 1 E 2. 1961. 44-57.

12. ROETHLISBERGER, F.J. l? DICKSON, W.J. Management and the worker. Cambridge: Harpard University Press. 1939.

13. HAUTY, G.T., TRITES, D.K. & BERKLEY, W.J. Frequency of shift rotation in air traffic control facilities and incidence of stress-related symptoms. Aerospace Med. 36.4. 1965. 350-356- 14. 'RAHE, R.H. Life-change measurement as a predictor of illness. Proceedings of the Royal Society of Medicine. 61.11. 1968. 1124-1126.

15. WUGHERTY, J.D., TRITES, D.K. & DIUE, J.R. Self-reported stress-related symptoms among air traffic control specialists (ATCS) and non-ATCS personnel. Aerospace Med. 36.10. 1965. 956-960. 16. WUGHERTY, J.D. Cardiovascular findings in Air Traffic Controllers. Aerospace Med. 38.1. 1967. 26-30.

17 RYAN, 0. Why earlier retirement for air traffic controllers? Journal of ATC. 6.5. 1964. 16-31. 18. GRANDJEAN, E. Fatigue: its physiological and psychological significance. Ergonomics. 11.5. 1968. 427-436. 19. JERDEE, T.H. Supervisor perception of work group morale. J. appl. Psychol. 48.4. 1964. 259-262.

20. WALKER, N.K. & DE SOCIO, E. The effect of combat on the accuracy of various human operator control systems. Bethesda,Maryland: Norman K. Walker Associates Inc. Contract No. DA - 36 - 034 - AMC - 0032R, 1964. 21. McKENZIE, R.E., BUCKLEY, E.P. E SALANIS, K. An exploratory study of psychophysiological measurements as indicators of Air Traffic Control sector workload. Atlantic City, N.J.: Federal Aviation Memorandum Report. Project 157-524-03R. 1966. 10-8

DISCUSSION: PAPERS OF DR ZET~~AM) It$=( HOPiCIN

MACLAFEN The RAF use women in Air Traffic Control duties and one hears widely varying amounts of their performance in this role. Would you care to comment on sex as a possible factor of importance?

HOPKIN In ~qyexperience women axe rarely full Air Traffic Control Officers, but act as ATC assistants. This may be because they are more readily recruited into the grade. Nevertheless, in many tasks requiring routine data imput women on average perform better than men. Their employment in this role may not be entirely fortuitous.

NICHOLSON In your presentation, Dr Zetzmnn, you showed slides comparing the performance of one radar observer with a two man system. The fomer showed an initial rapid decline in performance and then levelled off, while the two observers showed a progressive decrement in performance over the 4 hr period. Why do YOU think there is this differcnce in behaviour?

ZETZWINN The slide, which vias taken from a paper by Prof Schnidtke, shows a deterioration of performance both in the one and in the two observer system, though the decrement in pcrformance during the 30-60 min period is more apparent with one observer than xith two. However, the standard deviation of the measures is high so I would not be prepared to say that the manner is vhich pcrformance deteriorates with time is significantly different between one and two observers. The quality of performance was nevertheless substantially better over the greater part of the 4 hr period when t.vo observers were employed.

HOPKIN Work in the U.S.A. has shown that two observers behave as if they were mathe- matically independent sin& observers. The results Dr Zetzmann presented appear to be more or less in accord with this theory.

WHITESIDE To many Air Traffic Controllers English is a foreign language. Does this impose an extra strain on these controlJeru?

ZETZMANN The words and expressions used in Air Traffic Control are essentially in coded form - a code which has to be learned even if English is onels native language. In my experience I have not found the requirement to speak ?&&ish an additional stress in ATC operations.

WHITESIDE I'm not so sure, In some countries controllers under stress beoome incomprehensible.

HOPKIN The problem in some emergent nations is that the desire to place Air Traffic Control in national hands has led to the employment of some Controllers who are relatively inexperienced and the qudity of control is belo-w standard. I think that this stata of afZairs is temporerg. and vi11 improve with tinie.

WHITESIDE Is any attempt made to de-synchronize the change-over of controllers?

HOPKIN In most major airports controllers change over at set tines, rather like watches at sea. Usually 15 min is allovred as 'hand-over' tine and the actual change is made at a slack moment.

WNITFSIDE The change over times would appear to be determined primarily by administrative convenience, but I would suggest that de-synchronization of change over times might serve to minimize the degradation of pezformance with time which un- doubtedly occurs during a sustained period of duty.

HOPKIH This specific point has not, to the best of my knowledge, been tested. What is known, is that a decrement of perforname occurs at hand-over, no matter how this is achieved,

BENSON You have both been speaking about civilian Air Traffic Control. Are there any important differences between nilitary ATC duties and civilian?

HOPKIN My experience on this matter is restricted to the U,K., but an important difference between the militzry Air Traffic Controller and his civilian counterpart is that the former often has ancillary duties to perform in off- duty time. The civilian Controller is free and away from his place or employment vihcn off -duty.

BENSON So you are making a sinilar point to that which Col Staack deearlier, mmely the influence of duties additional to those of the basic task iJhich military personnel are obliged to perform.

ZETZMANN In Germany there is close co-ordination betvreen civilian and TrLlitary ATC operators. Only local approach to military airfields is tho solc 10-9 I

responsibility of military controllers.

JOHNSON Is there a problem associated with the employment of Air Traffic Controllers who have taken up these duties folloivirg aircrem training? HOPKIN In the U.S. and to a lesser extent in the U.K. a number of aircrew who have become Air Traffic Controllers became disenamoured with the job. The tendency is now to recruit 19-20 yr olds without flying experience into ATC duties. &perienco has been that these individuals are .just as proficient, sometimes better, than older men who have taken up this occupation after aircrew experience. 11

TECHNICAL EVALUATION

A. J. Benson

RAF Institute of Aviation Medicine Farnborough, Hants. UK

11-1

TEZHITICAL EVALUATION

The meeting was opened by the Chairman of the Aerospace Medical Pam1 of AGLX), Group Captain T.C.D. Uhiteside. He welcomed the participants and explained that a meeting on rest and activity cycles had been convened by AWZ in response to a request from the Military Committee of NATO for advice on how duty schedules influence the operational efficiency of personnel concerned with flight operations. The topic was a broad one, and unlikely to be covered in a comprehensive manner during a short meeting, Nevertheless, it was considered that duriw the limited time available some of the important problem areas viould be delineated and experimental evidence presented. This information would be of practical value to operational staff responsible for the organisation of work and rest schedules of flying personnel and ground based personnel concerned with flight operations.

During the course of the neeting, which occupied two half day sessions, 9 papers were presented. These fell into three main categories: a) laboratory investigations of physiological variables and task performamce during normal and abnormal work-rest schedules. b) in-flight studies of aircrew operating long-haul transport aircraft, and c) duty cycles in Air Traffic Control Tasks.

1. L&oratory,Studies

Evidence was presented, during formal presentations or ensuing discussions, that performance of simple psychomotor tasks such as reaction time or tracking showed a circadian variation. The poorest performance was recorded in the early morning in subjects wcustomed to working during the day and sleeping during the night. Although subjects who viere awakened from sleep had longer response times than those who viere required to stay awake all night, this normal circadian rhythm was still detectable in shift workers who normally slept during the day, and in personnel operating a 4 hr shift system. It was suggested that if optimum operator performance is required during the night period then the circadian rhythm of the operators mst be shifted in relation to local time. Such an adaptation is not achieved by nom1 shift working because of the knowledge of time of day provided by clocks, social interactions and other environmental cues. It would appear that temporal transposition of the circadian rhythm can only be achieved if the individual is completely isolated from local time and is provided with strong 'social' stimuli and other Zeitgebers which axe shifted with respect to local tirile.

It was recognised that the demonstration of circadian variation in the performance of laboratory tasks did not necessarily imply that performance of operational tasks in the flight enviroment viould suffer a comparable decrement. Nevertheless, it was agreed that the fundamental laws governing the cyclical variation of physiological and behavioural functions must be established, if recommendations on schedules of rest and activity are to nave a rational foundation. b) &ep loss

Although no paper dealt specifically with the performance decrement associated with sleep loss, this topic vas a recurring theme in many of the presentations. The opinion vias expressed that loss of sleep, brought about either by disruptive duty cycles (e.g. 4 hr duty, 4 hr rest) or by adaptation to a new time zone, was probably a more potent cause of impaired performance than the 11-2

inherent circadian variation. The need to maintain a stable sleep habit was emphasised and the role of drugs in the regulation of sleep was discussed. It was shorn that the performance of a vigilance task was degraded 16-20 hr after hypnotics were taxen to aid sleep at a non-habitual time. The effect of the administration of hypnotics over a longer period of time to individuals who axe trying to adapt to a new time zone, or alternatively axe attempting to maintain a home- base rhythm in the presence of local time Zeitgebers, awaits investigation.

2. Transport Operations

a) Double crew operations

The results were presented of in-flight studies carried out in long-haul transport aircraft , operated by double crews working 4/4, 10/10 and 16/16 hr duty/rest cycles. This type of operation disrupts normal sleep rhythms and leads to sleep deficit with consequent subjective fatigue and possible impairment of performance, The short (4/4 hr) work/rest schedule would appear to cause the greateet loss of dream and deep sleep, though there was some evidence that during the course of a protracted mission aircrew make some adaptation to the new duty cycle. Irrespective of the duration of the duty/rest cycle, half the crew are obliged to rest on entering the aircraft. The adequacy of sleep obtained during this period depends, inter alia, upon whether it coincides with their normal sleeping time, and the environmental conditions within the aircraft.

In 10/10 hr operations, the greatest problems are experienced by those crew members whose rest/work schedule is out of phase with their established sleep/wakefulness rhythm, though during the mission all crew members suffer a progressive desynchronization of the rest/work cycle with respect to home base time.

The principle factor which determines the duration of double crew operation is the accumu- lated slee;] deficit of crew members, in particular that of the crew whose duty schedule suffers the greatest temporal shift from normal duty times, A mission of 48 hr duration would appear to be satisfactory, but missions longer than 72 hr become extremely arduous. The other penalty imposed by prolonged double crew operation is the time taken at the end of the mission for sleep deficit to be made up and a normal sleep rhythm established. After a 2 day mission this may take a further 2 days, but after a 5 day mission some 7 days may be required.

b) Single crew operation

Irregular duty hours and repeated time zone shifts appear to be the principal factors influencing the efficiency of aircrew operating long range transport aircraft. In the absence of adequate 'in-flight performance measures it was considered that work/rest schedules which minimized the sleep disturbance associated with irregular duty schedules would lead to optimum performance and minim subjective fatigue,

The problems associated with this type of operation are well recognised by civilian airlines, This is manifest by the organisation of work schedu1.e~which attempt to maintain the work/rest cycles of crews close to their established (home base) times, and by instructions to dntain their normal sleep habits, even though these may not be in accord with local time. However, environmental and social conditions at lay-over stops may not allow this to be achieved. Pressure to adapt to local time becomes the more severe the longer the lay-over periods and time on route. Analysis of duty hours and durationnof sleep in relation to days on route has shown that if sleep deficit is to be avoided then the duration of duty per day must decrease as an exponential 11-3

function of days on route. The data upon which this analysis was based came from commercial airl'ine operatora but has immediate relevance to military transport operations,

Attention was drawn to the special problems of military aircrew operating long haul routes, Duty hours were extended by pre and post flight ground duties, prolonged lay-over periods necessitated adaptation to local time, and on return to their horns station aircrew were required to perform various ancillary, but obligatory, military duties. It was concluded that the 'work load' of these personnel was considerably higher than of their civilian counterparts. It was recommended that the attention of those responsible for the planning of work/rest schedules for military operations should take into consideration not only the hours flown, but also the other duties which the aircrew were required to perform,

3. Air Traff$q-Cp_ntrol Operations

The review of factors influencing work/rest sohedules of personnel engaged in Air Traffic Control operations made clear that standards of practice differed widely and were baaed on what was practical, convenient or traditional, rather than on scientific evidence.

Measures of operator performance on synthetic displays have demonstrated the manner in which the ability to recognise echoes or collision headings deteriorates with duration of observation of frequency of stimuli. However, the extrapolation of these findings to the practical situation awaits validation, for task loading and structure may have short and long term variation and differ substantially from one Air eaffic Control centre to another. For tasks requiring high vigilance, laboratory findings suggest that the optimum work period may be as short as 30 min. But frequent ohanges of operators, apart from the administrative difficulties, may give rise to a lower overall standard of performance than if longer periods are worked and the 'hand-over' period is extended. In control positions where each aircraft is under the control of a single operator for 10-15 min a long 'hand-over' period is obligatory if the new controller is to be fully informed about the developing current air traffic situation. Thus fairly long work periods, typically of 2 hr duration, are worked. However, it has not been shown that this time is the optimum for system efficiency.

There is a definite need for the systematic study of the influence of vrork/rest schedules on Air Traffic Control operators. In addition to the detailed structure of the work/rest cycle, the im_oortance of other factors, notably the length and frequency of rest periods within the work period, the age of the controller, and the nature of his task, should be assessed. Consideration should also be given to extraneous factors such as off-watch and canteen facilities and the influence of ancillary duties.

RECOMMENDATION

Formation of Ad Hoc ?lorking Group

During the general discussion which followed the formal presentations it was apparent that only specific aspects of the broad problem raised by the Military Committee had been covered. The Chairman of the Aerospace Medical Panel suggested that before a Report could be prepared for the Military Committee, the particular operational problems with which they were concerned should be determined, It was agreed that a small Ad Hoc Working Group should be established. 11-4

This group was tasked with the preparation of a comprehensive and practical Report once the detailed requirements of the Military Commit-tee had been established.

A J Benson Head, Vestibular Pnysiology RAF Institute of Aviation Medicine Farnborough, Hants, UK

Chairman, Behavioural Sciences Committee ASMP ATTENDANCE Dr. M. ALLNUW Sjefpsykolog GERdUtDT RAF Institute of iwiation Medicine Porsvarets Psykologiske avedling Farnborough, Hanis, England Sannergt. 14 Olso Mil, Norway Major Nddecin J. BAmE Centre de HedBcine dronautique I&. V.D. HOPICTN Caserne Mmzet E@ Institute of Aviation Medicine Boulevard Mn&x,l Jacques Farnborough, Hants, England 1040 Brussels, Belgium Squadron Leader A.T. JOHNSON Dr. A. J. Benson RAF Institute of Aviation Medicine RAF Institute of Aviation Medicine Farnborough, Hants, England Farnborough, knts, E~@uI~ Professor Dr E.A. LAUSCHICB Dr. J. BL'RKHOUT Brigadier General, ad?, 1.iC Space Biology Laboratory Flugmedizinisches Institut der Luftvraffe Brain Research Institute (308 FUrstenfeldbruck, Germany UCLA Medical Center Los Angeles, 90024, USA Surgeon Captain S.G.F. LIiZON RN Air LIedical School Brigadier General J. BOLIJGKJD, US@?, TIC Seafield Park DCS/ Bioastronautics eC Medicine Hillhead, Nr Fmeham, Hants, England Hq Air Force Systems Connand Andrews AFB ?ling Comiander R.B. MACLIW Washington DC, 203j1, USA Royal Air Force Aeromedical Training Centre North Luffenham Dr.Arne BORG Oakham, Rutland, England Sjeflegen for Luftforsvarets ISyntgaten 2 Lt.Colone1 Xedecin R. 1,TOORTHA;tLiXS Oslo lil, Norway Inspection du Service de Sante Force Rerienne Belge Colonel S.J. BWR 14, Avenue de la Cavalerie US&' School of -4erospace Itedicine 1040 Brussels, Belgium ( SKPPA) Brooks AFB, Texas 78235, USA Squadron Leader A.N. NICIIOLSON RAF Institute of Aviation Medicine Dr. Arne BRULTSGALRD Farnborough, Hants, England ( Statens Arbeidstilsyn) Almev. 28, 8, ITorviay Corn Captain T. "L Sjeflegen for Sjbforsvaret Major F.A.F. CARTENS Oslo Mil, Norway Aeromedical and Industrial Medicine Section, RNetMF Colonel 0. f,RNoAF, IX 2 Kampveg Surgeon Gcneral, R14oAF Soesterberg, Netherlands Sjeflegen for Luftforsvaret Oslo Mil CO~OXE~J.F. CULT&, USAF, IilC Oslo 1, Norway Chief, Medical Research Group Office of the Surgeon General, USAF Lt.Colone1 D.P. PARKS Hqs USAF (AFMSFG) Lledical Research Group i'iashington E, 20333, USA Office of the Surgeon General, UW Hqs USAF (AFMSPG) Generallt T. DALE Washington DC, 20333 USA Forsvarets sanitet Aslakveien 14 Drv. PzXxAM Rba, Oslo 7, Nomay Chief, Bio Effects Division 6571 st Aeromedical Research Laboratory Lt.Colone1 J.M. DUMi, WAF, EiC Holl.oman AFB, New IJexico Chief, Physiological Mucation Division 08330, USA Education Division USAF School of Aerospace Medicine Xajor I.C. PERRY, W.IC Brooks AFB, Texas 78235, USA Senior Medical Officer IQ Arv Aviation Centre Wing Coder D.I. FRYER, OBE liddle Ulallop, Hants, England RAF Institute of Aviation Medicine Farnborough, Hants, England Najor A.M. PFISTJZR, LIC, FAF Fkecut ive Brigadier General 1I.S. FUCHS, GAF, LIC Aerospace Medical Panel Surgeon General, GAF AGILRD 505 Porz-Wahn 2 7 Rue Ancelle Postfach 5000/501/16, Germany 92 - Neuilly s/Seine, France Lt.Colonel J.J. GARBE, CAE', IiIC Dr. F.S . PRZSTON Flugmedizinisches Institut der Luftwaffe Principal Medical Officer (Air) 808 Flbstenfeldbmck, Gemany Air Corporations Joint Medical Service Speedbird House London Airport, HounsJow, Ididdlesex, England Squadron Leader B.H. RANCE Group Captain T.C.D. WHITZSIDE Royal Air Force Aeromedical IWF Institute of Aviation Medicine Training Centre Farnborough, Hants, England. North Luffenhem Oakham, Rutland, England R.A. WILLAW Director, Plans and Programmes Dr.E. RIIS AGARD Forsvarets Psykologiske avdeling 7 rue Ancelle Sannergt. 14 92 - Neuilly s/Seine, France OsloMil, Norwa~r Dr.-Iw, H.J. ZETZ~WQI . Dr.R. RINGDAL Deutsche Forschungs- und Vereuchsanstalt S jeflegen for SjtJforsvaret ftlr Luft- und Raumfahrt e.V. Oslo Mil, Norway Inatitut ftc Flugfunk und Eiihosellen 8031 Oberpfaff enfof en/Flugplatz Air Commodore H.L. ROXBURGH, CBE Germsny RAF Institute of Aviation Medioine Farnborough, Hants. England

Professor Dr. RUTEKTIUNZ Direktor des Institutes ftlr Arbeitsmedizin an der Just-Liebig-Universitllt Giessen 63 Giesoen Kugelberg 78 Germany Brigadier General Professor A. SCANO, IAF, bzC Direttore Scuola Militare di Sanita Aeronautica Via Piero Gobetti 2A 00185 Row, Italy

Colonel K. STUCK, GAF, MC Conmand Surgeon/Air Wansport Command GAF 505 Porz-Wahn Postfach 5000/507 Germany

Oberstlt Dr. Arvid STEEN Sjeflegen for Luftforsvaret Oslo Mil, Norway

Dr. C.W. SN-JACOBSEN EEG Lab Gaustad Sykehus Vinderen, Oslo, Norway

AvD Direktbr 0. SJdRAAS Directorate of Civil Aviation Konglefaret 18 1343 Eiusma.rka, Norway

Brigadier General J.J. VARICLA, PAF, MC Secretaria de Estado da Aeronautica Gab. do CEUFA Avenida da Liberdade 252 Lisboa 2, Portugal

Lt.Colone1 T. VERHEXJ Aeromedical and Indutstrial Medicine Section, RNethllF 2 Rampweg, Soesterberg Netherlands Dr &.VOGT LORENTZEN Sjeflegen for Luftforsvsret Oslo Mil, Oslo 1, Norway

Prof, Dr. med. WAALE3 Rikshospitalet Oslo 1, Norway

D1: rer. nat. R. Max-Planck-Institut ftk Verhaltensphysiologie 81 31 Erling-Andechs Germany V V t' t' 0 ?

? 0 0-1 N4 N

V H P

U3 r B w I^' 4 z4 '0 m U3N N ? ?J ? 4 0 0 4 -1N N

N N E- t- O 0 t- t- m ai N N W W.. m m L- L- m m d W W

0 0 G d a

N N t- t- 0 0 t- t- d m WN NW m m t- t- m m d d W W

NATIONAL DISTRIBUTION CENTRES FOR UNCLASSIFIED AQARD PUBLICATIONS Unclassified WURD publications are distribvted to NAlO Wlwr Nation6 , tbrou#b ths unclassified National Distribution Centre6 listed below , BEutmY ITALY amera1 J.- Aeronautics Militare Oomdinateur MARD - V. aL. .- Ufficio del De1egnt.o Ntazionale all' MARD Etat Maor hroes Uriennes Cneerne Prince Baudouin Place Dsillr, Bnuelles 3 LUXEMBDURQ CANADA Obtainable through B&Ix(ICM Director ai Scientific Information Services NETHERLANDS Defence Reebvch Bowd Netherlsnda tmlegation to W Deputment of National Defence 'A' Building - National Aeruspnce laboratory. NU Ottawa. Ontario Attn: Mr AH.- DEWARK P.O. Box las mish Defence Reeamh Board Delft Nsterbrogadss Kneerne NORWAY cop~soenB Norwegian Defense Research Establishment FRANCE Main Library. c/o Mr P.L.m O.N.E.R. A, (Direction) P.O. Box 25 20, .Avenue de la Division Leclerc N-2007 gjeller ea. m&tiiion-sous-eaeneux PORrnmL QEmm Direcod0 do Servico de Material ~tr.letalle fir Liiftfahrtdokunentation da Form &rea und Information Rna de Effiola Politecnica 42 Yula-lkeresia Str. 21 Lisbon 8 6cbm 2l Attn: Brig. aenenl Jose de 60-a CLI~M Attn: Dr Ins. H.J.RAU1EY- mm 0-E mrkish oeneral Staff (ARsr) nellenic hdForces Caamand llnkara D mulch. Athens UNITED KIN(m0Y 1CEAND Ministn of Technolorn Reports Centre Director of Aviation Statim Spuare House do Plurr.d St. Mary Crw Rwkjavik Orpington, Kent BR5 3RE @tIlSD STABS #&mal Aeronautics end Spsce Administrstim (NASA) . ' Laelw Field. Virginia 23365 Attn: Report Distribution md Storage Ulit

,I rl.. *** IF a= Xf -lea of the original publ~cationare not available at tbese csntres. the Polloring mw be porchneed frm: Microfiche or Photocopy Microfiche Microfiche Natloual Techaical E8Ro/QIw mace Ministry of Whnolow Information senice (RRS) Domntation Service Reparts Centre 5285 Port Royal Road mropem Space Station Swam Wuue Springfield Reaearch Orproizution St. Mu7 Qw , Virginia 22151, USA 3 114. Aveoue de lysuilly Owinston. Kent BR5 SPg r** 92, Neuilly-anr-Seine, Frmce paglad a, I Ibe rspaest for microif& DT photocwy of ul AQARD dOCument should include the MARD serial nunher. title, 'author or editor, and publication date. Requests to cp8~1should include the NASA mceIuIIon mort number. Full Mbliogmbical references md abstracts of the newb isnred MARD Dublications are given in the rollodng bi-mmUrly .hstrMt journal8 dtb indexe8: Bcientific and mchaical Asroepace Reports (STAR) united Btates Qommment Research md DBIleloRent published iw MBA, Report Index (IJsrorU). ablisbed iw the OlearintSIouSe Wentitic end %chi for Federal Scientific md Technical Infomtlm. p.b. mx 3s. College Springfield. Virginia 22151. USA Ymlatd 20740. USA

Pnnted by Tcchnrcal Efsting md Rapmduction Ltd #wfod nouse. 7-9 Charlotte $t, London. YIP SD