36499®Fli ISSUE g ht 73

S a f e ON COMMERCIALAVIATION SAFETY t y i ss 73

25/3/09 The official publicationoftheUnitedKingdom FlightSafety Committee

11 : 56

P age 1 ISSN 1355-1523

WINTER 08 36499®Flight Safety iss 73 25/3/09 11:56 Page 2

goodbye RIS and RAS from 12 March 2009 the UK’s Air Traffic Services Outside Controlled Airspace change. You can get find full details and an interactive tutorial guide to the new services at www.airspacesafety.com

UK CAA licensed commercial pilots and controllers have been sent a CD guide in the post and private pilots’ CDs are being despatched in January 09. (MoD staff will receive details direct from the MoD)

in the meantime the existing ATC services outside controlled airspace remain available.

The Airspace & Safety Initiative (ASI) is a joint CAA,NATS,AOA,GA and MoD effort to investigate and tackle the major safety risks in UK airspace. 36499®Flight Safety iss 73 25/3/09 11:56 Page 3

Contents

The Official Publication of THE UNITED KINGDOM FLIGHT SAFETY COMMITTEE ISSN: 1355-1523 WINTER 2008

FOCUS is a quarterly subscription journal devoted Editorial 2 to the promotion of best practises in . It includes articles, either original or reprinted from other sources, related to safety issues throughout all areas of air transport operations. Besides providing information on safety Chairman’s Column 3 related matters, FOCUS aims to promote debate and improve networking within the industry. It must be emphasised that FOCUS is not intended as a substitute for regulatory information or company publications and procedures. Fighting the War on Maintenance Error 4 by Squadron Leader John Franklin MBE RAF DACS S02 Eng FW Editorial Office: The Graham Suite, Fairoaks Airport, Chobham, Woking, Surrey. GU24 8HX Tel: 01276 855193 Fax: 01276 855195 e-mail: [email protected] Communication Error 6 Web Site: www.ukfsc.co.uk Office Hours: 0900 - 1630 Monday - Friday by Ross James MacDonald, ATC Watch Manager,

Advertisement Sales Office: UKFSC The Graham Suite, Fairoaks Airport, Chobham, Clear Air Turbulence 8 Woking, Surrey GU24 8HX Tel: 01276 855193 Fax: 01276 855195 by Jim Galvin, World Area Forecast Centre Forecaster email: [email protected] Web Site: www.ukfsc.co.uk Office Hours: 0900 - 1630 Monday - Friday

Printed by: The Operation & Interpretation of Weather Radar 11 Woking Print & Publicity Ltd by Ratan Khatwa PhD FRAeS, Honeywell Aerospace, Seattle, USA The Print Works, St. Johns Lye, St. Johns, Woking, Surrey GU21 1RS Tel: 01483 884884 Fax: 01483 884880 e-mail: [email protected] Web: www.wokingprint.com Members List 16

FOCUS is produced solely for the purpose of improving flight safety and, unless copyright is indicated, articles may be reproduced providing that the source of material is acknowledged. Overrun – TEM Analysis 18

Opinions expressed by individual authors or in by Peter Simpson, Manager Air Safety advertisements appearing in FOCUS are those of the author or advertiser and do not necessarily reflect the views and endorsements of this journal, the editor or the UK Flight Safety Committee. Wind Reports – Not the Full Story 23

While every effort is made to ensure the accuracy of the information contained herein, FOCUS accepts no responsibility for any errors or omissions in the information, or its consequences. Front Cover Picture: Photograph by Mike Moores. Specialist advice should always be sought in B747-400 landing on Runway 27 left at London Heathrow Airport, immediately before relation to any particular circumstances. the inaugural A380 arrival.

focus winter 08 1 36499®Flight Safety iss 73 25/3/09 11:56 Page 4

EDITORIAL Is Flight Safety Our Primary Concern or Our Primary Target for Savings?

by Rich Jones

long with most industrial sectors, the territory of Chief Executives and Finance knowledge and airmanship; training is the key Acommercial air transport sector is Directors. They permeate the minds and element which delivers this capability and beginning to suffer a serious downturn in thoughts of the entire workforce of any airline, ensures safe endings occur and not accidents. business which has been created by the loss particularly at times like these. These of confidence in the economy generally, the distractions, and the potentially negative effect Despite many years of exchanging aviation safety lack of flexible and reliable financial support on an individual’s concentration on the job in information, and the same mistakes being made and an uncertain and variable oil price. In hand, be they pilot, cabin crew or engineer, will time and again, the number of incidents in today’s addition, the industry, which has always been tend towards errors and mistakes being made sophisticated, risk-aware, commercial air transport extremely competitive has also to operate in more easily and more often. sector remains more than sufficient to justify the a global market where the population has continuing need for the constant reiteration of become increasingly aware and protective of During such times of personal pressures, it must aviation safety lessons. For example, as winter the environment and where political be worth considering greater emphasis on approaches the perennial threat of aircraft icing interference and legal scrutiny bring yet supervision, communication and support as a will be upon us and there will undoubtedly be further pressures from both sides of the business-positive incentive to counter instances of loss of control caused by insufficient aviation argument. Nevertheless, the airline potentially extremely costly errors – it is an attention being paid to it. Does your training sector continues to perform with remarkable investment which could pay dividends to the include seasonal reminders of the importance of resilience and dynamism; it has seen and bottom line in an industry where mistakes can appropriate measures to counter the effects of successfully dealt with many of these be expensive, if not business threatening. ice? The aviation safety website – Skybrary - challenges on many occasions in the past 40 offers up some sound advice to counter aircraft years or more, although it has probably never Training is another area for careful consideration icing that you may wish to consider! had to face them in such depth, coincidence during these financially taut times. Over recent and complexity as it is having to do today. years, both initial and continuity training courses Turning from an old chestnut to a more recent have been steadily squeezed in terms of content phenomenon; the introduction of more efficient Why should FOCUS, a magazine primarily and time allotted, on the basis of the training fuel loads is making an important contribution concerned with aviation safety, wish to rehearse provider’s assurances that simulation and training towards the bottom line, but do your pilots have the many pressures being simultaneously aids have become more effective and therefore a clear understanding of the diversion criteria for exerted on the modern airline business in 2008 much more cost efficient.Yet, over a similar period, the airports and air traffic service providers they – they are very familiar to most of us and clearly commercial aircraft have become highly are using? Should circumstances of weather or a source of serious concern. The rationale for automated and somewhat easier to fly and sudden runway closures conspire against them, doing so is to set in context the obvious operate – at least whilst they remain fully do they know enough about the constraints and temptation in these difficult times for the flight serviceable. However, the on-board systems to assumptions which those supporting the safety message to be pushed down the priority provide the necessary situational awareness and to aircraft’s safe operation will apply, in order that list and off the agenda. Significant pressure to enable the aircraft to be flown accurately in ever sensible decisions on fuel uplift and diversions quickly reduce costs by shedding those more congested airspace have become increasingly are being taken? resources and people dedicated to delivering complex when things start to go wrong. safety, whilst continuing to utter the ‘safety is our primary concern’ mantra can be seen an Nowadays aircraft, and the systems that make easy win for the bottom line. them simple to operate, are becoming more reliable but this is tending to drive us towards However, there is strong business argument becoming increasingly reliant and trusting of against the initially seductive approach of them. In the rare event that they fail, hopefully reducing the sector’s investment in aviation with all the clues to signal such a failure, then the safety in order to transfer the weight of financial necessary depth of training must still have been effort to areas which appear to contribute more provided in order that the accurate diagnosis is directly to business survival. For a start, financial reached and the appropriate corrective actions worries about the future are not the exclusive are deployed through the application of sound UK FLIGHT SAFETY COMMITTEE OBJECTIVES ■ To pursue the highest standards of aviation safety. ■ To constitute a body of experienced aviation flight safety personnel available for consultation. ■ To facilitate the free exchange of aviation safety data. ■ To maintain an appropriate liaison with other bodies concerned with aviation safety. ■ To provide assistance to operators establishing and maintaining a flight safety organisation.

2 focus winter 08 36499®Flight Safety iss 73 25/3/09 11:56 Page 5

CHAIRMAN’S COLUMN

The ‘Basics of Safety’

by Steve Hull, British Airways

s I leave British Airways after a 38 year an incident, as there is no doubt that the up and use impressive acronyms, but the Acareer that has spanned engineering, smoking hole will be met with an immediate basics are the same. Safety is the flying and for the last sixteen years safety, and impressive response, as history shows us. identification, analysis, management and it could be assumed that I would have seen A near miss will never get the same company elimination, and/or mitigation to an many changes in aviation, but in actual reaction as an accident, although the process acceptable , of risks that threaten the fact there have been remarkably few. leading to both events may have or will have capabilities of an organisation. been identical. I joined, as it was then British European So how can we progress safety for the future? Airways on 2nd September 1970 the same As safety professionals it then becomes our There are a number of initiatives in the year that the Boeing 747 took to the sky. The duty to constantly press for the latent workplace e.g. IOSA, SMS, ISAGO, Safety Plans, Boeing 747, affectionately known as the conditions firstly, to be recognized and then, LOSA etc, all of which have good intentions. ‘Jumbo Jet,’ held the passenger capacity record acted upon. If latent conditions are not But how effective are they? That is the for 37 years until it was surpassed by the recognized then incidents must be question that needs to be asked. What ever Airbus A380 last year. A year before, in 1969 highlighted.The danger of course occurs if it is happened to the safety basics? Complicated Concorde made her first test flight and in 1973 only the serious incidents that are reacted to. processes can be confusing and can be less supersonic passenger travel became a reality. It takes a very mature and enlightened than helpful and even considered to be an company to put resources into searching out excuse to carry out those safety basics. So what changes have there been, Concorde is and remedying latent conditions, as this is the a distant memory and supersonic passenger area where the most value will be obtained. Safety can be taken for granted and this is travel has become a dream that once again Airline safety is primarily identifying areas of certainly true in some airlines. But if safety is appears to be years away, the world has concern and then mitigating them, it cannot genuinely the ‘No.1 Priority,’ then safety realised the effects of carbon emissions and be based solely on ‘gut feel.’ departments must be manned by the best the push is to try to produce aircraft that fly qualified and motivated people, who receive ‘on thin air instead of, in thin air.’ Airline As I have quoted before, airlines have short suitable remuneration for their expertise. It passenger travel is more available to the memories when it comes to accidents. This is should never be an area that is classified as majority as opposed to the minority and most mainly due to our own success story. Aircraft ‘the rocking chair of the airline’, where good importantly aviation safety is every airlines are safer, pilots and engineers better trained servants are hired for a couple of years past No.1 Priority. and ATC is more sophisticated. The result is retirement age to top up their pensions. fortunately we do not have accidents often It would be inappropriate of me to ‘wax lyrical’ enough to become proficient in accident It can be argued, to become an effective over aviation history, but more appropriate to response etc. Unlike in recent history when it Safety Manager one needs an all round concentrate on today, and in particular aviation was expected that an airline would lose an knowledge of aircraft and the airline safety. So what progress has been made? Most aircraft or two, so extra were ordered. operation. I agree, but safety must be an area airlines major focus is on data collection and where energetic thinkers and analysts are information exchange. This means that there So as a Safety Manager how are you expected encouraged to join for a career, not as a are probably millions of pieces of data that to act? Having had first hand experience, it is stopgap for better things, or a retirement describe past events. For some airlines the data not a natural flow or a simple slip into home for aging employees. certainly helps in understanding the state of automatic mode, as an old colleague once the operation, but as has been quoted before described. It is more a case of intuition. For me, safety management is not about ‘data is important and will help, but data driven Arriving at an accident site is surreal, fighting fires, but more about stopping the safety only helps to fix what already went particularly if the accident is ‘one of yours.’ fires starting. wrong.’ Data has never prevented an accident, How are you trained to react, or more in fact the collection of data is reactive and of importantly how do you react? Certainly the course it is proactive safety management that old adage of sitting on your hands for 15 is preferred. minutes is useful. Firstly though it is important to establish links with the How easy is it to be proactive as a safety interested parties and manage the site from professional? Being proactive in safety an airline perspective. One thing for sure is, it management you attempt to identify the will be a long drawn out process that does not latent conditions and reduce them, then require quick fixes or knee jerk reactions, but equally you will reduce the incidents, serious a well constructed and thought out process incidents and ultimately the accidents. This is that will span several weeks or months but a great theory, but in practice there is hopefully not years. reluctance for airlines and also non-airline organizations, to take steps to identify and The basics of managing safety have not then remove the latent conditions. Airlines changed significantly from the first crash in response is usually based on the outcome of 1908, to what we do today. Sure we gloss it

focus winter 08 3 36499®Flight Safety iss 73 25/3/09 11:56 Page 6

Fighting the War on Maintenance Error

by Squadron Leader John Franklin MBE RAF DASC SO2 Eng FW

■ ith the current high levels of Incorrect installation of components from human error and although it will never Woperational tempo and the rapid during maintenance. be completely eliminated, we must changes in the way engineering support is understand its effects in order to control the ■ provided, more and more is being expected The fitting of wrong parts, such as bolts, risk they pose. of our aircraft technicians. With constant washers and seals of incorrect size. pressure on maintenance personnel to ■ achieve operational and training Electrical wiring discrepancies, such as Errors are not intrinsically bad imperatives, there is a very real chance that cross connections. maintenance error will occur and this could Error is one of the fundamental drivers of ■ lead to catastrophic accidents if not Loose articles left in aircraft. human learning. Without committing errors identified and managed. we would be unlikely to learn or acquire all of ■ Inadequate lubrication. the skills required for safe and efficient work. Here at the DASC we are evolving our Human The key is to ensure that lessons are learnt and ■ Factors programmes further to better Cowlings, access panels and fairings not importantly shared as widely as possible to understand maintenance error. Work has secured. minimise the chance of someone making the commenced to formally establish a same mistake. ■ Maintenance Error Management System Fuel/oil caps not secured. (MEMS) across the MOD. A key part of any ■ MEMS is the Maintenance Event Decision Aid Undercarriage ground locking pins not (MEDA), which provides a comprehensive removed before flight. approach for conducting thorough and ■ consistent investigations, determining the Contamination of systems. factors that lead to an error and making ■ suggested improvements to reduce the Aircraft damaged during moves, by likelihood of future errors. With the work in its vehicles or during functional testing. infancy, it is important that in the meantime all personnel involved in aircraft maintenance Figure 2 - KC135 over pressurisation during maintenance. appreciate that the first step in fighting the war on maintenance error is to understand what You cannot change the human condition, error is; only then, will we be able to effectively but you can change the conditions in which develop and implement such a system. humans work

The problem with most errors is not that they What is Maintenance Error? have been committed, but that they have been committed in a safety-critical

1 environment. Therefore it is important to Humans make errors frequently. In fact, Figure 1 – Tornado ground damage. humans make an error on average every 60 recognise that we are operating in such an seconds. These errors can be as simple as environment, recognise the error traps within typing the wrong letter in a word, or as Maintenance Error Management Principles the way we do business and base the way we serious as driving through a red light. In an approach the prevention of maintenance error aircraft maintenance context, maintenance There are a number of measures that can be put around this understanding. error is a discrete form of human error. A in place in a maintenance system in order to maintenance error is the failure of the catch a maintenance error before it becomes a maintenance system (including the people problem during the flight of an aircraft. However, The best people can make the worst errors involved) to perform in the manner we in order for these measures to be effectively expect it to. It is different from a violation as implemented, the following principles of error Errors are not just committed by inept the latter involves a deliberate departure management must be understood. individuals in the workplace. We must from established rules and regulations. understand that all humans are capable of making errors and that even the best technicians Common Maintenance Errors Human Error is both Universal are capable of making the worst mistakes. and Inevitable Before we consider some of the principles of maintenance error management, it might first Humans are not machines, so while the People cannot easily avoid those actions be useful to consider some of the most consequences of human error may be they did not intend to commit common maintenance errors that are seen undesirable, it is important to understand that here at DASC, from the incidents reports human error is as much a part of life as eating, Blame and punishment do not make much received from across all 3 services. sleeping and breathing. We are always at risk sense when the act that was committed was

4 focus winter 08 36499®Flight Safety iss 73 25/3/09 11:56 Page 7

unintentional. This is the cornerstone of a just identify those behaviours that are When it comes to investigating and reporting culture. This is not to say that people who inappropriate and undesirable. These technical faults and errors, the focus should have made an error should not be culpable for behaviours include poorly documented not necessarily be on what has been done to their actions; however punishment and blame maintenance, failing to use or follow approved the aircraft to return it to a serviceable will not stop error from recurring. maintenance procedures, high operational condition; this is the purpose of the tempo, perceived pressure, and a perception maintenance documents. It is more useful to that we work in a blame free culture where understand WHY the event occurred and Errors are consequences rather than causes personnel can deliberately commit violations what can be done to prevent it happening without fear of retribution. again. In Aviation Safety, there are rarely new In the past, investigation techniques involved errors – just old ones waiting for new people finding out who committed the error and These must be replaced with appropriate to make them, so the wider lessons must be then punishing that person as a warning and behaviours that ensure maintenance publicised as widely as possible. to try and stop others making the same personnel work within recognised risk mistake. However, it is better to see errors as boundaries using the established Maintenance error occurs because humans consequences rather than causes, in that maintenance regulatory framework at all are at the heart of it. Its prevention relies on every error has a history and a chain of events times, regardless of the external pressures. several quite simple measures: a just culture is that has led to the eventual outcome. This is especially relevant on operations, vital to ensure that unintentional errors are Determining the factors that contributed to where the temptation may exist to cut not punished. Investigation of the chain of the error, and removing one of these factors corners for perceived operational reasons. events leading to the error with the aim of from the error chain is far more beneficial. determining all the contributing factors, and If the system is wrong, it should be changed to enabling maintenance managers to develop ensure that it is right for others in the future. defences that will stop that event chain from Maintenance error is about managing the However, when doing so, we must be aware occurring again. In this way we can ensure manageable that what might be perceived to be the right that our skillful technicians are given every way to do something at the individual or assistance to enable them to deliver a safe We cannot control the uncontrollable. That is squadron level might not be considered correct and airworthy product to our flight crews. to say that there are certain human at higher levels of the organisation.To that end, characteristics, such as being prone to it is vital that changes are staffed appropriately Note distraction, forgetfulness and preoccupation, before they are implemented. A consequence 1 An error is the failure of planned actions to achieve their which although difficult to control, can be of this is that personnel in the command chain desired goal, where this occurs without some managed through training and experience. must ensure that suggested changes are unforeseeable or chance intervention. Situations and people cannot be controlled actioned, one way or the other, as quickly as but they can be managed. possible. A local work-around can only survive for so long before it results in an incident.At all

Managing Maintenance Error stages any change process must be clearly understood by all involved in it, regardless of There are a number of measures that we their position in the chain of command. currently have in place to prevent maintenance errors occurring. These include All maintenance incidents and near misses training, authorisations, supervision, should be reported and investigated with the inspection, quality audits, procedures, aim of identifying and eliminating error- publications, rules and regulations. However, promoting conditions. An example of the kind despite the many checks and balances in the of error-promoting conditions that regularly system, maintenance errors still occur and a pop up during Flight Safety occurrences are significant proportion of incident reports are summarised by the ‘Dirty Dozen’. put down as Human Factors (Non-Aircrew). Our understanding of these events could be better and we could certainly do more in the Lack of: Abundance of: way we investigate and learn from Communication Pressure maintenance error. This is one of the key Resources Stress purposes of the proposed introduction of Assertiveness Norms MEMS and MEDA to the military air Awareness Fatigue environment. Teamwork Distraction Knowledge Complacency As a first step, management techniques within any maintenance organisation must

focus winter 08 5 36499®Flight Safety iss 73 25/3/09 11:56 Page 8

Communication Error

by Ross James MacDonald, ATC Watch Manager – Gatwick Airport

viate, navigate, and then led to parliamentary debate on the subject circumstances to act as a check when a pilot Acommunicate. It’s an old adage that (they didn’t talk about my relationship may misinterpret a call not directed at them. we’ve most likely all heard before, whether mishaps however). An eastern European as pilots or controllers. However, simply airline Boeing 737 outbound from London More recently, and probably more widely- because communicate comes in last Heathrow suffered a navigation systems known, changes have been introduced to UK doesn’t make it any less of a critical part of failure, and found itself tracking all over our ILS phraseology, where ‘Cleared for ILS the safety systems we build into the skies. Why? Not as much to do with the approach’ is not deemed to be appropriate. It operation. navigation error as you may think. The was felt that pilots should be asked to ‘report communication between the pilot and ATC established’ on the localiser and further to “It’s important to de-stress away from work, suffered numerous problems, partly because ‘descend on the ILS’. This stems from you know” the pilots’ English was not good and they numerous incidents of aircraft descending struggled to explain the problem they had. below minimum safe altitudes believing it I was at the Isle of Wight Festival recently, was safe to do so. Controllers working in a something I would thoroughly recommend So what’s the solution? Well, requirements busy environments will understand the need (you’re never too old for live music). Whilst for language proficiency are in the pipeline. for flexibility in when they can use the RTF dancing away to ‘Scouting for Girls’ I decided Many states have committed to dates to and hence even more recently pilots may be to share the experience with a girl I’d been ensure that their pilots and controllers are up passed the instruction ‘when established on seeing. The message read something along to the International Civil Aviation the localiser, descend on the ILS…’. the lines of: Organisation’s minimum ‘level 4’ proficiency. However, I’ve witnessed personally incidents One UK exception that I can relate to as a ‘Dancing away to scouting for girls! What between ‘level 6’ pilots and controllers, where tower controller at a busy airport, is the UK fun! X’. confusion has prevailed! difference regarding conditional line-up clearances. Almost all pilots will have received Within 5 minutes the response was not Standard phraseology helps us out in these the instruction ‘after the landing, line up’ in favourable: situations - and I’d encourage us all to use it the UK and ‘behind the landing, line up where possible. It may be interesting to ask the behind’ abroad; but why this obvious ‘I don’t think that was meant for me.’ pilots among you the last time you were difference at such a critical phase of flight? It’s tested in any way on what constitutes a a subtle difference, but it’s felt that ‘after’ No kiss; always a bad sign. ‘standard phrase’; or where to find information much more clearly indicates a sequential on it? A group of NATS controllers and pilots following in the departure order than ‘behind’, ‘Read it again, it’s the name of the band! X’, recently undertook the task of producing a which could simply mean further back than multiple-choice test for pilots and it may well the subject aircraft of the condition. Finally, I sent, quickly trying to recover the situation. be coming to a line check near you soon. Of consider an airport with left and right runway course, you can always have a read of the designators and the possible interpretation of ‘Oh… Sorry. Xx’. CAP413 - the Radiotelephony Manual to ‘behind the landing aircraft, line up runway refresh your memory. ## right behind’…! Relationship normal, crisis averted; all but for the slightly hasty reading of a text and “Handover on an Andover over Dover, over” ‘After the sixth aircraft on the left that looks perhaps the skipping of the word ‘to’… like all the others…” In recent times many changes have taken Why share that with you? In my (so far) short place in the UK’s standard phrases - are you Runway incursions and conditional clearances time as an operational air traffic controller aware of them? It became clear a few years are subjects that I must consider every day at and supervisor at a major UK airport I’ve ago that the use of ‘Flight Level One Zero work. Using a runway to its capacity requires already encountered, investigated and indeed Zero’ and ‘Flight Level One One Zero’ was us to control the RTF so we can issue the been involved in many incidents involving causing many level busts. This led to the UK instructions as soon as we need to, and pass seemingly innocuous communication errors. introduction of ‘Flight Level One Hundred’ information that allows pilots to decrease If not always the direct cause of a problem which has led to remarkable improvements. their response times as much as is practical.To they often aggravate a situation and increase both these ends conditional clearances are the seriousness of an incident. In the more distant past the introduction of vital tools in our box. However, there is no ‘Pass your message’ to replace ‘Go ahead’ was doubt that from a human factors point of “We have a problem with the left phalange” taken to prevent crews (and aerodrome drivers) view, they can result in miscommunication. from believing that their request had been A serious event that occurred in London approved. ‘Recleared’ is not used in the UK, So how can we minimise the risk of airspace has highlighted this issue, and even rather ‘Climb’ and ‘Descend’ are preferred in all conditional clearances? Well controllers can

6 focus winter 08 36499®Flight Safety iss 73 25/3/09 11:56 Page 9

be sensible about how they use them. I was “Did he just say what I thought he said?” few minutes later, he was surprised to see two informed by a pilot colleague (a training aircraft line upon the runway - the aircraft captain!) recently that ‘If you tell me about Pilots of course can play their part. A full he’d instructed to and the aircraft that, having something that’s going to happen in more read-back, including callsign, means that the also read back the clearance but been than 30 seconds time, I’m not interested, and risk of a miscommunication is reduced ‘drowned out’, believed that it was his turn. will most likely forget”. Now I’m no expert on dramatically. Can you honestly say you use the human factors side of this but it makes your callsign with every transmission? How The opportunity for error will always exist, but some sense. Our short-term memories are many times have you heard something on even on busy frequencies we can all act as a vulnerable (seven items, plus or minus two the RTF and thought, that doesn’t sound check for each other. I for one know that I will depending on the person, I’m led to believe), right? How many times have you read back never be put out by having to say something and controllers should be aware of other a clearance only to be told it was something twice if you’re not sure of what I said; or if you pilot’s activities at this critical stage of flight. else and you hadn’t realised? think I haven’t noticed an incorrect read-back Do we really need to pass that conditional from another crew. Finally, if you happen to be line up clearance on the aircraft at five miles Expectation bias - where you hear what you unfortunate enough to be a prospective now? Or do we need to have a series of four, expect to hear, rather than what was actually girlfriend of mine, please read your messages five, six or even more aircraft committed to said, is a frequent factor in reported incidents. carefully before responding. the runway through the use of conditionals? A colleague of mine, when asked, told an aircraft that he was number two for departure. Having then changed his mind a

focus winter 08 7 36499®Flight Safety iss 73 25/3/09 11:56 Page 10

Clear-air turbulence and the sub-tropical jet streams

by Jim Galvin World Area Forecast Centre Forecaster

oes significant clear-air turbulence FL420 and the other (faster) stream near 40 oN forecast where the indicated probability of CAT Doccur in the tropics? When I first came and 35 oS, its core around FL370. Where the is greater than about 6% per 100 km of flight5. into forecasting, the general view was that flow splits, a tight Z-shaped fold forms in the is was extremely rare, even though the northern-hemisphere flow. It is S-shaped in the Given the high altitude of the STJ, air density strongest winds at the outer edges of the southern-hemisphere. These folds are found is relatively low, so the effects of acceleration upper tropical troposphere – the sub- close to the 180th meridian. Although this is and deceleration are relatively modest6. CAT tropical jet streams – reach 230 kn or more the most common area for folds to form in the is most likely close to the core of the jet at times. STJ, they sometimes occur elsewhere. stream and below it, on the cold (normally poleward) side. Turbulence occurs in the atmosphere as a Over land in particular, where large troughs result of the overturning of pockets of air. develop in the STJ, the cooler air aloft can As the component of the flow in the STJ that Much is associated with cloud, in particular at enhance deep convection, as the poleward does not follow altitude contours is generally lower levels, but in the upper atmosphere, it side of the jet stream is brought unusually small and accelerations are usually gradual, its often occurs in clear air, usually in small areas close to the equator, over warm moist air flow is not generally turbulent. However, the or pockets close to the bands of strong winds close to the surface. temperature difference between tropical and – the jet streams, where wind speed and that of the extra-tropics is often large in winter, direction change rapidly. Most turbulence at resulting in a large horizontal wind shear on the high levels is light, but forecasts often indicate Clear-air turbulence poleward edge of the flow. In these conditions, areas where turbulence may be locally especially where there is anticyclonic curvature moderate or severe (Figure 1). Although the flow of the STJ is relatively and the STJ speed is high, moderate turbulence modest in the contorted flow close to the may occur7 This is almost always in clear air, The sub-tropical jet streams (STJs) are equator (usually no more than 100 kn), there since the STJ is only associated with weather generally westerly winds that mark the edge is often considerable deceleration of the flow systems in limited areas8. of the tropics. The core of these winds is near into the fold, associated with curvature and FL390 and is usually found close to 30 oN and divergence – a measure of the rate at which Where the speed of the air flow changes 30 oS (Figure 2). In places, the jet stream may air is spreading away from the centre of the rapidly, either vertically or horizontally, have considerable depth (more than 30,000 flow, as well as convergence – a measure of turbulence is usually the result. Where this ft) and a horizontal extent of more than 10 o the rate at which air is moving into the centre occurs in clear air, it presents an invisible hazard latitude. Speeds are highest in winter and may of the flow – into the equatorward branch1. to aircraft and it is essential that significant be absent in summer, in particular in the (This is particularly true in the northern areas of CAT, despite their low probability in northern hemisphere, when its speed is rarely hemisphere, where the strongest flow of the any one place, are indicated on forecast charts. more than 80 kn, except across the Pacific STJ is usually found close to Japan.) The result Ocean. When there is a strong interaction of can be moderate (occasionally severe) Various mathematical, semi-empirical rules cold and warm air, the speed of the STJ turbulence (Figure 3), which almost always have been devised to predict CAT. Wind-shear reaches a peak, usually in spring and autumn. occurs in clear air. This was a particularly values of 20 kn per 100 km in the horizontal notable cause in investigations by Turner and and 20 kn per 1000 ft in the vertical may be Bysouth2. Close to the equator, the STJ is also expected to produce pockets of moderate CAT. Folds and bifurcations in the STJ only in weak balance with the forces that drive Values of 30 kn per 100 km in the horizontal it, so small-scale confluent and diffluent flow and 30 kn per 1000 ft in the vertical may Most waves in the STJ have only small may be expected, resulting in overturning and produce pockets of severe CAT6. amplitude and a long wavelength, which is one local pockets of light to moderate clear-air of the reasons to believe that there is generally turbulence (CAT). little turbulence associated with them. Interaction with mountain ranges However, the situation over the eastern Pacific CAT may affect flights at high levels and is a Ocean, where the warmest air is usually major cause of discomfort and disruption to The depth of the flow of the STJ tends to bring confined to a narrow band near the equator, passengers in flight. It is relatively rare in the its lower part into contact with several frequently causes the STJ to split into two tropics, but does occur at times in association mountain ranges, notably the Andes in the widely-separated streams. This development is with the STJ3. Table 1 shows the percentage southern hemisphere; the Rockies and the most marked in the winter. probabilities of a flight encountering turbulence Himalayan complex in the northern for every 100 km of flight within the tropics. It hemisphere. This interaction generates CAT When this bifurcation occurs, one stream is is usually accepted that moderate, or close to the level of the peaks, in particular found close to 15 oN or 15 oS, its core around occasionally severe turbulence should be those aligned across the flow. The highest

8 focus winter 08 36499®Flight Safety iss 73 25/3/09 11:56 Page 11

mountains that lie across the flow of the STJ in ranges at the tropical margins, generate areas 4) Atkinson, G. D. (1971) Forecasters’ guide winter is the Hengduan Shan of southern of CAT, locally moderate in strength. Over the to tropical meteorology. University Press China, which reaches more than 16,000 ft and eastern Pacific, turbulence may occur of the Pacific, Honolulu (2002 reprint) the Andes of South America, which reach surprisingly close to the equator. around 17,000 ft. Turbulence is very likely to 5) The Met Office issues ICAO GRIB occur to the east of these ranges, especially as bulletins for 36 hours at 6-hour intervals, there is a generally easterly flow below the Forecasts of clear-air turbulence showing areas of potential CAT level of the mountain tops, against that of the development (on an experimental basis) STJ9. In spring and autumn, the highest ranges Currently the main source of CAT forecasts is from model runs at 0000 UTC, 0600 UTC, of the Himalaya also interact with the STJ, as it SIGMETS (for severe turbulence) and SigWx 1200 UTC and 1800 UTC. makes its way, respectively, north and south.At charts, most of the latter issued by the World this time of year, speeds are usually high Area Forecast Centres in London and Kansas 6) Meteorological Office (1994) Handbook (typically reaching 130 kn to 150 kn). This City (see Fig. 1). However, as many of the of aviation meteorology. 3rd edition. turbulence, which may be within cloud during factors that generate CAT are represented by HMSO Press, London the winter monsoon season, may be numerical prediction models of the considered a serious hazard to aircraft flying at atmosphere2, the Met Office has been 7) Asnani, G. C. (1993) Tropical meteorology medium levels. Where large-scale atmospheric conducting a trial, issuing numerical GRIB10 (2 vols.). G. C. Asnani, Pune waves are generated by the stable flow over files direct from its weather-prediction model, these mountains, moderate turbulence may showing areas of CAT probability5. Pilots can 8) Where the STJ forms troughs, due to the occur throughout the troposphere and into the expect to use these CAT fields more and more equatorward advance of cold air, semi- lower stratosphere. in coming years, as they are expected to be permanent lines of cloud, similar to high- considered operational within two years or so. latitude fronts, but containing isolated or Associated with the STJ, but separate from it, occasional embedded cumulonimbus further areas of tropical CAT are also observed clouds may be found. These are most at times. These may be identified by their References and notes often seen over the south-west Atlantic high-cloud signature, as in many cases they Ocean, central south Pacific Ocean, occur where wind speeds are not above 80 kn. 1) Bysouth, C. E. (2000) Clear air turbulence south-west Indian Ocean and north-west Ribbons of cirrus may be seen and may persist – a reply. Weather, 55, pp 122, 147 Atlantic Ocean (see Figure 1). for days within areas where there is a large horizontal wind shear (Figure 4). This often 2) Turner, J. A. and Bysouth, C. E. (1999) 9) Galvin, J. F. P. and Walker, J. M. (2007) occurs within upper troughs previously Automated systems for predicting clear Weather image. Cloudy South-East Asia. associated with a cold front, the deep cloud of air turbulence in global aviation forecasts. Weather, 62, pp. 55-56 which has dissolved. These have been noted, Proc. 8th Conf. Aviation, Range Aerosp. in particular, over the Arabian Sea, close to the Meteorol., Dallas, Texas. American 10) Gridded Binary data, of a format similar wintertime trough in the STJ. Meteorological Society, pp 368-372 to that of the winds and temperatures used for flight planning 3) Roach, W. T. and Bysouth, C. E. (2002) Other causes of turbulence How often does severe clear air turbulence occur over tropical oceans? Although forecasters are most interested in Weather, 57, pp 8-19 forecasting CAT, there are two other areas that cause significant turbulence at medium and upper levels. Most important are areas of cumulonimbus Table 1. Percent frequency of CAT within the tropics per 100 km flight 4 and cumulus clouds, where vertical velocities are often very high – both up and down. Layer clouds Area Turbulance category No. of also cause light to moderate turbulence, but they None Light Moderate Serve Observations can be seen and turbulence can normally be o o expected within them. 0 – 30 N 91.3% 6.0% 2.7% 0.1% 12,619 Indian Ocean (0o – 15o S) 96.0% 2.7% 1.3% 0.0% 149 o The strength and local distortion of the STJ, as Africa (south of 15 N) 94.8% 3.7% 1.4% 0.1% 4,258 well as its interaction with the high mountain All zones 91.9% 5.5% 2.5% 0.1% 17,006

focus winter 08 9 36499®Flight Safety iss 73 25/3/09 11:56 Page 12

Figure 1. ICAO 24-hour high-level SigWx forecast produced by WAFC, London, valid 1800 UTC on 13 March 2008, extracted from the transmitted BUFR data set. Areas of probable CAT, in particular area 4, associated with the STJ over the Pacific Ocean are shown within zones enclosed by green dashes. The depth of the CAT fields appears in the “CAT areas”box (bottom left).

Figure 2. Typical wintertime flow of the STJ (both hemispheres). The core of the flow is shown with Figure 3 altitudes in hundreds of feet (International Standard Atmosphere) given opposite the fleches. Fleches show 50 kn as triangles and 10 kn as bars with the head and tail of the flow at 80 kn.

Figure 3. Wind speed and direction at 200 hPa (FL390) and values of Brown’s indicator of clear-air turbulence (10-5 s-1) over the eastern equatorial Pacific at 1800 UTC on 24 February 19991. The white line indicates the path of a flight from Fiji to Los Angeles which encountered turbulence for much of the journey on that day. It may be a surprise to see the greatest probability of CAT associated with a jet stream of only 110 kn, when the STJ upstream (near the 180th meridian) has a peak speed near 170 kn, but no more than moderate turbulence. [Note: this indicator has the dimensions of wind shear (s-1) and is a numerical measure of severity, as well as risk, whereas no measure severity is provided by the probabilistic indicator produced as GRIB files. [In very broad terms, 3 x 10-5 s-1 » 1 % 100 km-1.]

Figure 4. Satellite image of ribbons of cirriform cloud associated with wind shear over South America at 1800 UTC on 17 October 2006. (Courtesy NOAA/NESDIS)

© Crown Copyright 2008.

Figure 4

10 focus winter 08 36499®Flight Safety iss 73 25/3/09 11:56 Page 13

The Operation & Interpretation of Weather Radar

Ratan Khatwa PhD FRAeS, Honeywell Aerospace, Seattle, USA

Summary ■ Flight crew knowledge of weather radar becomes noticeable at ranges above 40 mi, fundamentals. and if ignored can lead to weather image his article presents a study that interpretation errors. The effect becomes very Tidentifies and analyses factors that are ■ The role of weather radar operation in significant as range increases. associated with the operational use of accidents/incidents. weather radar by flights crews. The 3) Fifty-five percent of pilots were unaware investigation included three main The techniques used to scrutinize these areas that a weather target partially within a radar activities: a human factors evaluation to included: beam may not be presented at its “true color” gain a better understanding of how flight on the weather display. The color selected for crews operate weather radar; a survey of ■ Survey of flight crews around the world. display is a direct function of the power flight crew designed to assess their returned to the receiver. In cases where the understanding of weather radar ■ Human factors evaluations involving beam is partially filled, the total power fundamentals and perceptions of current pilots using weather radar. returned (averaged over the beam) may not day training; and an analysis of represent the calibrated value associated with incidents/accidents involving the use of ■ Analysis of incidents/accidents where the the target cell. weather radar. The data revealed some flight crew operation of conventional shortcomings in the understanding of weather radar was included in the 4) Sixty-three percent of pilots were unaware fundamental concepts in the operation of investigation. that at cruise altitudes of FL > 310, green radar weather radar and that dedicated crew echoes at short range near the current Flight training for weather radar does not appear This article is limited to the role of flight crews Level should be avoided. Typically at these to be standard practice. Areas for using weather radar.There are always multiple altitudes, the targets are less reflective. At high improvements in training are covered. In factors associated with operational safety and altitudes there is a possibility of the presence addition, the role of new technology to the cause of accidents. The data presented of unstable air and above the storm cell. It improve pilot’s weather awareness and herein should be viewed with a balanced is therefore not advisable to penetrate the less decision-making are briefly described. perspective. The safety information and reflective part of the storm top.This factor was recommendations herein are not intended to also identified in the accident/incident supersede any policies, practices or analysis and the pilot-in-the-loop evaluation 1. Introduction requirements. described later in this article.

The primary function of airborne weather 5) Seventy-three percent of pilots were aware radar is weather analysis and avoidance. It is 2. Flight Crew Weather Radar Survey that tilt angle does not need to match a therefore not a “weather penetration tool”. climb, or descent, angle to detect weather on However, the proper operation and Forty-six ATP-rated pilots participated in a the flight path.The antenna should be pointed interpretation of airborne weather radar is survey conducted to gain insight into pilot at the base of the convective weather cell dependent upon pilots having an adequate knowledge of conventional weather radar during climb. Generally, the lower 18,000 feet understanding of its capabilities, the provision principles and their views on current weather is the most reflective part of the storm. Radar of dedicated crew training and appropriate radar training. The group comprised a should be used to analyze the weather standard operating procedures. During the culturally diverse population from North characteristics such as the vertical extent of development of Honeywell’s next generation America, Europe and Asia. Most participants cells and avoid strong convective activity. weather radar family, IntuVue™, part of the were airline pilots although some corporate Returns along the flight path angle may not design strategy was to establish a clear operators participated. Pilot experience varied necessarily provide a full indication of storm understanding of how current generation from 3,200 – 35,000 hours total time and intensity and turbulence levels encountered if weather radar is used by flight crews and to average age was 52. All pilots were penetrating the cell. identify areas of difficulty and concerns of line experienced in using weather radar. A pilots. A primary design goal for the various summary of survey data is presented below. 6) Eighty-eight percent of pilots were models within the IntuVue family was to unaware of the range at which their radar is simplify the crew’s task of system operation. 1) Eighty-five percent of the pilots no longer calibrated and returns are displayed An important number of findings related to understood the antenna stabilization concept. at their true levels. Radar beams broaden with the operational use of conventional weather Antenna stabilization maintains a constant distance, thus decreasing the proportion of radar were uncovered during subsequent angle between the weather radar antenna and the beam which is filled with moisture. At human factors investigations. the target area being scanned, regardless of shorter ranges, the returned power is more variations in aircraft pitch and/or roll attitude. representative of the target cell and therefore Those areas of the investigation are the focus it is more likely to be displayed at its true of the current article, namely: 2)Sixty-three percent of pilots did not calibrated value. Typically, weather radar ■ Flight crew perception of current weather appreciate that tilt angle needs to be returns are calibrated within a range of up to radar training. managed to compensate for Earth curvature 60-80 mi. effects. The effect of the Earth’s curvature

focus winter 08 11 36499®Flight Safety iss 73 25/3/09 11:56 Page 14

7) Sixty-eight percent of pilots felt that their radar operation are discussed here. Thirteen Multiple factors are always involved in any current weather radar training is insufficient. pilots with an average total time of 12,423 aviation occurrence, and the limitation of this Examples of specific pilot comments include hours experience participated in the study is that it does not include many other the following: evaluation with conventional radar. Average critical factors such as provision of timely subject age was 54 years. Pilots were required weather information, accuracy of weather ■ “Equipment specification and limitations to operate the weather radar in a wide range data, role of ATC, regulator, etc. not well understood. Line training of operational scenarios using a PC-based standards variable with few or ill-defined part-task simulator. The primary task was to An extensive review of formal occurrence standards”. detect and avoid potential weather hazards. reports from nine worldwide accident The weather detection and decision-making investigation bodies was conducted for the ■ “Imprecise knowledge of the system – data are presented in Figure 1. A “correct period 1987-2007. Sufficient data for fixed- vague guidelines about what to do with decision” implies avoiding penetration of wing aircraft engaged on public transport, information presented”. significant weather. In those cases where business/corporate and freight operations significant weather was penetrated, factors involved in 14 occurrences were identified. ■ “Insufficient information about included mis-management of tilt, gain and Unfortunately the role of weather radar interpreting radar display and use of tilt”. range. Mis-management of tilt was the most operation was either not discussed, or frequent factor and examples include using insufficient information was included in most ■ “Mostly taught by on-the-job training, only upward tilt or zero tilt, no change in tilt, final investigation reports. Some highlights of so myths and wrong concepts easily and over scanning the most reflective part of the results are presented below. passed on”. the cell. In these cases the cell of interest was either not displayed or appeared to have One-quarter of the injuries were fatal and half ■ “We learn by using weather radar out in green echoes and consequently subjects the aircraft was either substantially damaged the real world. Training is practically non- continued into the threat area. Also, in one or destroyed. Many incidents included existent”. scenario some subjects did not appreciate the substantial hail damage, typically to significance of green radar echoes at high windshields; nose radome; radar antenna; cruise altitudes at close range. In more than wing, horizontal stabilizer and vertical 3. Pilot-in-the-Loop Evaluation 80% of the cases pilots using conventional stabilizer leading edges; and engine inlet weather radar detected significant weather. cowls. Half of the events occurred during As stated earlier, part of the design strategy Note that pilots using the RDR-4000 display cruise with 35% occurring between top-of- for the IntuVue family of weather radars, and modes exposed to identical scenarios actually descent and the destination airfield. Figure 2 specifically the RDR-4000-the first model performed significantly better in detecting show the distribution of occurrences across developed for Air Transport platforms-was to and avoiding significant weather, e.g. flight phase. establish a clear understanding of how detection rates better than 95%. conventional radars are used by flight crews More than half the cases occurred in and to identify areas of difficulty and Instrument Meteorological Conditions (IMC). concerns of pilots. A comparative evaluation 4. Analysis of Flight Crew Operation were present in all cases of was performed that involved independent of Radar During Weather Encounters severe weather penetration and more groups of pilots using the new RDR-4000 importantly this signifies the presence of radar display modes and conventional The objective was to identify and analyze cumulonimbus cloud formation. A weather radar. This study is described in detail those factors related to the flight crew cumulonimbus cloud entails a risk of elsewhere (see Ref. 1,2) and only those operation and interpretation of weather radar moderate or severe turbulence, icing and hail aspects relevant to conventional weather from reports of actual weather encounters. as confirmed by the study data. Several of the occurrences involved multi-cellular storms or squall lines. In most cases, severe levels of turbulence prevailed.

Hail was present in almost two-thirds of the cases and was present in approximately onethird of the sample.

4.1 Weather Radar Operations

Figure 3 shows that in almost two-thirds of the occurrences, the operation of the weather radar and/or interpretation of the radar display were not necessarily optimal. Specific Figure 1 Weather Detection & Avoidance examples include:

12 focus winter 08 36499®Flight Safety iss 73 25/3/09 11:56 Page 15

Figure 2 Flight Phase Distribution

■ Improper tilt operation—such as over- scanning storm cells, maintaining a constant tilt and not actively managing tilt in areas forecasted with unstable/convective activity. Figure 4 Figure 3 Radar Operation & Display Interpretation shows that this occurred in at least 43% of the cases. To keep track of weather in the vicinity of the flight path, the antenna tilt angle should be periodically adjusted. As the altitude changes or as the aircraft gets closer to the storm cell, tilt angle needs to be changed so the radar beam keeps scanning the most reflective part of the storm. During over-scanning the centre of the radar beam scans above the most reflective part of the weather cells and hence significant returns may not be presented on the radar display: the actual top may still be in the aircraft flight path and inadvertent penetration of a storm top is possible. Figure 3 Radar Operation & Display Interpretation ■ Improper use of gain control. Note that these findings correlate with pilot feedback in the survey presented in Section 2. ■ Misinterpretation of ground returns (built-up city area) as significant weather.

■ Weather radar in OFF position despite forecasted cumulonimbus formation.

■ Not fully appreciating the limitations of the radar and impact on the displayed image (e.g., radar attenuation, absence of significant echoes (red/amber) at high cruise altitudes).

4.2 Radar Training and Operational Documentation

Figure 5 reveals that in at least half of all cases appropriate training for weather radar use was Figure 5 Radar Training not provided to flight crews, examples include: It should also be noted that in several instances inadequate operational documentation such as the Aircraft Operations Manual were cited by the investigation body:

focus winter 08 13 36499®Flight Safety iss 73 25/3/09 11:57 Page 16

■ Pilots without any formal training on the use of radar. Instances were revealed where pilots indicated that their training was limited to “trial and error experience and information from other pilots” and “learning by doing.” This approach can lead to improper radar operating procedures and techniques.

■ Insufficient training standards/ requirements by company management not requiring weatherradar training in recurrent, upgrade and re-qualification training.

■ The radar training provided did not adequately address the specific operating characteristics and procedures of the installed system. Figure 6 IntuVue Volumetric Buffer

■ Pilot Guides furnished to the operator by the radar manufacturer that contained information on the operation of the radar, and detailed advice on weather detection and interpretation, were not used during training or made available to flight crews.

■ No information on the operation of, or suggested techniques for use of, radar in day-to-day operation.

■ Not sufficiently clear in its description of the recommended technique for operating the radar for weather avoidance.

5. Technology Improvements Figure 7 RDR-4000 AUTO Mode Example

The advent of technology improvements for Information requirements were central to ■ The display mode selection task has commercial uses and the ability to store addressing many of the challenges that face changed from allowing the flight crew to reflectivity data in real-time in a 3-deminsional flight crews when using conventional select a single “WX” mode to either a volumetric buffer provide the opportunity of weather radar: “MANUAL” or “AUTOMATIC” weather presenting weather information that is more display mode. task-orientated than has traditionally been the ■ The tilt management task for the weather case. Honeywell’s IntuVue 3-D weather radar detection task has been eliminated – ■ The AUTOMATIC mode enables strategic has a range of 320 miles and supports there is no tilt control for the RDR-4000 weather detection information. An elevations of up to 60,000 feet. The radar weather display modes. automatic distinction is made between system continuously scans the entire three- weather associated with the intended dimensional space in front of the aircraft, and ■ The weather information presented to vertical flight path and weather that is stores all reflectivity data in an earth- the crew is automatically corrected for not. In this mode, “Flight Path Weather”, referenced three-dimensional (“volumetric”) Earth curvature effects by the RDR-4000 or weather near the altitude of the memory buffer. This buffer is continuously system. Judicious tilt management and intended flight path, is displayed updated with reflectivity data from new scans. cognitive effort is therefore no longer differently from “Secondary Weather”, The reflectivity data are extracted from the required for interpreting weather returns which is further away from the flight buffer to generate the desired display views at longer ranges. path. The separation is accomplished by without having to make (and wait for) view- applying an envelope around the specific antenna scans. intended flight path: weather within the

14 focus winter 08 36499®Flight Safety iss 73 25/3/09 11:57 Page 17

envelope is considered Flight Path 4) Operators should provide guidelines 2. Khatwa R. Pilot-in-the-Loop Evaluation of Weather; weather outside the envelope is relating to when, and if, radar should be Next Generation Weather Radar Displays, Secondary Weather. Secondary Weather selected OFF. 25th International Congress of the is visually distinguished from Flight Path Aeronautical Sciences (ICAS), Hamburg, Weather by black stripes. 5) Operators should ensure that the Aircraft Germany, 2006. Operations Manual provides a clear ■ The MANUAL (Constant Altitude) display description of the recommended techniques mode presents constant altitude weather for operating the radar for weather avoidance. on a plan view display for storm cell analysis and tactical avoidance tasks. This 6) Radar manufacturers should investigate the eliminates cognitive processing feasibility of developing radars that simplify associated with pilot’s mental both the system operation and interpretation computation of cloud tops/bases. The of the weather display. crew is required to select an altitude of interest on the control panel. As mentioned above, the data is also 7. References corrected for the Earth’s curvature. 1. Khatwa R. An Analysis of the Operation & ■ Terrain data is used to automatically Interpretation of Weather Radar by Flight reduce ground clutter in the weather Crews, Flight safety Foundation European display modes – the crew is not required Aviation Safety Seminar, Bucharest, March to adjust controls in order to discriminate 2008. between weather and ground returns on the display.

■ A vertical profile (side-view) display of weather is also available.

This system is in service on the Airbus 380, Boeing 777 and 737NG and C-17 platforms.

6. Recommendations

1) Operators should provide crews with formal initial and recurrent weather radar training. Fundamental concepts in the operation of weather radar (beam coverage, Earth curvature effects, antenna stabilization, tilt and gain management, calibrated weather and range) should be included. In addition, system limitations such as attenuation and significance of green radar echoes at high altitude should be included. 2) The significance of precision tilt management for detection, analyzing, and avoiding hazardous convective weather, and pitfalls of over-scanning storm cells should be emphasised during crew training. 3) The radar training program should include information on the specific radar that the flight crew will be using and should reference the information provided by the manufacturer concerning its limitations and recommended operating procedures.

focus winter 08 15 36499®Flight Safety iss 73 25/3/09 11:57 Page 18

Members List

Members of The United Kingdom Flight Safety Committee

FULL MEMBERS Belfast Intl. Airport European Aviation Air Charter Alan Whiteside Ron Hendrick Chairman British Airways Bluestream Aviation EVA Airways Steve Hull Marc Adams TBA

Vice-Chairman bmi regional FlightLine Monarch Airlines Peter Cork Capt. Derek Murphy Capt. Tony Wride British International Flight Data Services Ltd Treasurer Capt. Terry Green Capt. Simon Searle Air Contractors Capt. Anthony Barrett-Jolley CAA Flyglobespan Sarah Doherty - Safety Data Dept. Capt. Steve Rixson Non Executive Board Member Graham Rourke - MRPS RAeS Simon Williams - Flight Operations Policy Gael Limited Peter Richards Martin Bowman CargoLux Airlines Aegean Airlines Mattias Pak GAPAN Capt. Vassilis Anadiotis Capt. Alex Fisher Cathay Pacific Airways Aer Arann Rick Howell GATCO Joe Redmond Shaneen Benson Charles Taylor aviation Andrew Cripps GE Aviation Capt. Henry Donohoe Mike Rimmer CHC Scotia AIG Aviation Duncan Trapp Goodrich Actuation Systems Ltd Jonathan Woodrow Gary Clinton CityJet Airclaims Capt. Tom Murphy Gulf Air Co John Bayley Capt. Paulo Fitze Club328 Air Contractors TBA Hong Kong Dragon Airlines Ltd Capt. Anthony Barrett-Jolley Kwok Chan Cranfield Safety & Air Mauritius Accident Investigation Centre Independent Pilots Association Capt. Francois Marion Dr. Simon Place Capt. Peter Jackson

Air Seychelles CTC Aviation Services Ltd Irish Aviation Authority Ben L’Esperance Robin Berry Capt. Harry McCrink

ALAE Cyprus Airways Jet2.com Ian Tovey Andreas Mateou David Thombs

Astraeus Ltd DHL Air Libyan Airways Chris Barratt Gavin Staines Engr. Tarek Derbassi

BA Cityflyer Eastern Airways UK Ltd Chris King Capt. Jacqueline Mills Robin Freeman

BAA Limited easyJet London City Airport Tim Hardy Capt. Chris Brady Gary Hodgetts

BAE SYSTEMS Reg. A/C Eurocypria Lufthansa Consulting GmbH Alistair Scott Capt. Constantinos Pitsillides Ingo Luschen

Baines Simmons European Aeronautical Group UK Malaysia Airlines Bob Simmons Max Harris Capt. Ahmed Zuraidi

BALPA European Air Transport NV/SA Manchester Airport plc Carolyn Evan Vincent Lambotte Simon Butterworth

16 focus winter 08 36499®Flight Safety iss 73 25/3/09 11:57 Page 19

Monarch Airlines Thomson Airways RAeS Capt. Tony Wride Jez Last Peter Richards

NATS Virgin Atlantic Airways RAeS Eng. Karen Skinner John Dunne Jim Rainbow

NetJets Willis Nuno Aghdassi Paul Wren CO-OPTED ADVISERS

Panasonic Avionics AAIB Bob Jeffrey GROUP MEMBERS Capt. Margaret Dean

PrivatAir bmi CHIRP Jan Peeters David Barry Peter Tait

Qatar Airways bmi Eng. GASCo TBA Willam Taylor John Thorpe

QBE Aviation bmi baby Legal Advisor Jerry Flaxman Nicole Stewart Edward Spencer Barlow Lyde & Gilbert Rolls-Royce Plc Bond Offshore Helicopters Phillip O’Dell Tony Duff Royal Met. Society Rob Seaman Ryanair Bond Offshore Helicopters (Maint) Capt. George Davis John Crowther

SBAC Bristow Helicopters Martyn Graham - Secretariat Capt. Derek Whatling Vic Lockwood - FR Aviation Bristow Helicopters Eng. ScotAirways John Parker Nigel McClure flybe. SR Technics Ireland Ltd Neil Woollacott Frank Buggie flybe. Aviation Services Superstructure Group Steve McNair Eddie Rogan MOD TAG Aviation (UK) Ltd DARS Col. Steven Marshall Malcolm Rusby DARS Eng. Cdr Kevin Fox

TAM Brazilian Airlines QinetiQ Capt. Marco Castro Flt. Lt. Jacki Doncaster

Thomas Cook Airlines QinetiQ Eng. Capt. Roger Chandler Keith Wigmore

ADVERTISING IN THIS MAGAZINE Focus is a Quarterly Publication which has a highly targeted readership of 32,000 Aviation Safety Professionals worldwide. If you or your company would like to advertise in Focus please contact:

Advertisment Sales Office: UKFSC, The Graham Suite, Fairoaks Airport, Chobham, Woking, Surrey. GU24 8HX. Tel: +44 (0)1276 855193 Email: [email protected]

focus winter 08 17 36499®Flight Safety iss 73 25/3/09 11:57 Page 20

Air France Runway Overrun – TEM Analysis

by Peter Simpson, Manager Air Safety, Cathay Pacific

he aim of analysing this incident using to RWY 24L, they were advised that the crew passengers were seriously injured during the Tthe Threat & Error Management (TEM) of an aircraft landing ahead of them had crash and the ensuing evacuation. methodology is to enable crew to develop reported poor braking action, and Air France's strategies to manage the threats and errors weather radar was displaying heavy The incident is analysed using a TEM faced by this crew. It should be highlighted precipitation encroaching on the runway from framework. The Threats are listed, and then that TEM analysis does not cover the northwest. At about 200 feet above the the threat recognition and threat organisational (latent) failures in much runway threshold, while on the 24L ILS with management aspects are discussed. The same detail, rather it focuses on the aspects of autopilot and autothrust disconnected, the process is then applied to the Errors. The the incident that crew have some level of aircraft deviated above the glideslope and the Undesired Aircraft States (UAS) are described, control over.The organisational aspects are groundspeed began to increase. The aircraft and finally the lesson learnt are discussed. covered in the Transportation Safety Board crossed the runway threshold about 40 feet of Canada investigation report, which is above the glideslope. downloadable from their website at Threats http://bst-tsb.gc.ca/en/reports/air/ During the flare, the aircraft travelled through 2005/a05h0002/a05h002.pdf an area of heavy rain and visual contact with During the cruise and initial descent, the crew the runway environment was significantly displayed effective threat management reduced. There were numerous lightning strategies. However, as the approach Introduction strikes occurring, particularly at the end of the continued, the threats were no longer being runway. The aircraft touched down about recognised, and those that were recognised Air France flight 358, an A340-300 aircraft 3800 ft down the 9000 ft runway, reverse were not effectively managed. departed (CDG), France, at 1153 (UTC) thrust was selected about 12.8 seconds after ■ on a scheduled flight to Toronto (YYZ), landing, and full reverse was selected 16.4 Weather. Severe thunderstorms, heavy , with 297 passengers and 12 crew seconds after touchdown.The aircraft was not rain and hail, low visibility, lightning and members on board. able to stop on the remaining 5200 ft and changing winds. departed the far end at about 80 knots. The ■ Before departure, the crew obtained the aircraft stopped in a ravine at 2002 UTC Fuel Remaining. Due to delays and arrival weather forecast, which noted the (1602 Local) and caught fire. All passengers holding, diversion fuel was almost possibility of thunderstorms. While and crew members were able to evacuate the exhausted. approaching Toronto, the crew were advised aircraft before the fire reached the escape of weather-related delays. On final approach routes. A total of 2 crew members and 10

18 focus winter 08 36499®Flight Safety iss 73 25/3/09 11:57 Page 21

■ Runway Conditions. The runway was procedure and discussed the flight path ■ Fuel Remaining contaminated and braking reported as for a (non-standard) missed approach, Recognised: yes poor. including which cells to manoeuvre Managed: yes between.At this stage the crew believed a Due to delays at YYZ, holding was required, ■ Runway Length. The runway length left missed approach was still an option. The and the crew regularly reviewed their fuel little margin for error. PM was monitoring the winds and remaining calculations. After selecting advising the PF. YOW as an alternate, the crew calculated ■ Crosswind/Tailwind. Around 1000 ft their maximum holding fuel at YYZ, which there was a strong crosswind. Below 300 ■ Weather was initially 14 minutes. At one stage the ft the wind shifted with tailwind (approach and landing) crew were advised of an onwards clearance component of up to 10 kts, Recognised: yes time that would put the flight close to its Managed: no maximum holding time. The crew twice ■ Reduced visibility. Forward visibility was During final stages of approach, the crew reminded ATC that they were being lost in the flare due to rain. had visual contact with the ground about vectored away from the airport. Several 2-3nm from the runway.There was heavy minutes later the crew reviewed the Air ■ Unstable/High Energy Approach. At the lightning on both sides of the runway and France policy for declaring minimum fuel. threshold the aircraft was 40ft above red radar returns were showing at the glideslope and then landed deep. end of the runway area. For a 5 minute ■ Runway Conditions period either side of the landing, the rain Recognised: yes ■ High workload. During the final phase of and hail had been recorded at Managed: yes/no the approach and landing, the workload 1.6mm/min (almost 100mm/hour, which The runway surface was contaminated saturated the crew, who became fixated is 50% higher than a Black Rainstorm (greater than 3mm water). The pilots on landing. Warning in HKG). The lightning activity reported it was covered in water, was significant, with five ground strikes producing a shiny, glass-like surface. The ■ Missed approach path was obscured by reported near the runway threshold in a aircraft landing prior to Air France thunderstorms. several second period. After crossing the reported braking as poor.Autobrakes were runway threshold the aircraft entered an selected from Low to Medium several ■ Deep landing, 3800 ft down the 9000 ft area of heavy rain, with numerous minutes prior to touchdown (in response runway. lightning strikes and severely reduced to the previous aircraft report?). The visual contact with the ground. The crew Captain also discussed the need for a did nothing to manage these threats. positive touchdown. However, these Threat Recognition / Management strategies can not be considered adequate mitigation by themselves for a ■ Weather contaminated runway, given the runway (enroute and arrival) length issue (below) Recognised: yes Managed: yes Forecast thunderstorm activity was the primary threat faced by the crew and they had uplifted an additional 3 tonnes of fuel, giving an extra 23mins of holding to manage this threat. Enroute the crew obtained regular weather updates for YYZ and alternates. It was only in the last hour of flight that the weather conditions rapidly deteriorated. In response to the first report of poor weather and lightning (just over 1 hour before landing), the crew reassessed diversion airports, and eventually changed their primary choice to Airport (YOW) due to weather considerations. Ten minutes before landing the crew noted red weather radar returns along their approach path, and decided to continue the approach with caution. To manage the threat the crew reviewed the windshear recovery

focus winter 08 19 36499®Flight Safety iss 73 25/3/09 11:57 Page 22

■ Runway Length ■ Unstable/High Energy Approach Errors Recognised: no Recognised: no Managed: no Managed: no There were few error management strategies The crew did not calculate the landing The autothrust and autopilot were applied by the crew, as most of the errors distance required for RWY 24L, despite disengaged around 300 ft AGL. Due to a were initially inconsequential, and the full the weather reports, nor did they include manual increase in thrust and increase in consequences did not manifest themselves the runway length in the crew brief. The tailwind the aircraft arrived over the until late in the approach, when the crew runway was 9000ft. For a landing on a threshold about 40ft above glideslope. were already under high workload resulting in wet runway, at YYZ’s elevation (approx The PM made no callouts to indicate the landing fixation. It is unfortunate that some of 550ft), with autobrakes Low, nil wind, full deviation. After this, the control inputs these errors had very simple procedural fixes. flap and no reverse thrust (which appears and aircraft profile suggest the PF had to be the situation the pilots initially difficulty in controlling the aircraft, and ■ The briefing did not cover the runway planned), the Air France Flight Manuals workload was significant. The approach length and missed approach procedure calculate the landing distance required to became unstable only in the late stages. be 7203 ft (2196m). This increases 21% ■ Runway length required was not with a 10 kt tailwind, to 8715 ft. Adding ■ High Workload calculated ‘contaminated runway’ to the above Recognised: no results in 10250 ft with thrust reversers or Managed: no ■ Conducting an approach into heavy 11390 ft without. Passing over the During the final phase of the approach thunderstorm activity threshold at 100 ft (which the crew did) and landing, the workload saturated the rather than 50 ft adds another 950 ft to crew, who became fixated on landing.This ■ Crosswind limits exceeded then landed the landing (Airbus FCTM). meant the crew were not fully aware of with tailwind the wind shifts occurring, nor of how ■ Crosswind/Tailwind much runway was being used up, and it ■ Go-around not conducted Recognised: no also impacted on the delayed use of Managed: no reverse thrust. Ultimately, the high ■ Deep landing Due to high workload and task saturation workload impacted the decision making during the final stages of the approach, and judgement to continue the landing. ■ Delayed use of Reverse Thrust the crosswind threat was not recognised, nor was the change from crosswind to ■ Missed Approach Path Obscured By ■ Failure to use automation to full capacity tailwind component. Around 1000ft the Thunderstorms ND indicated an 80 degree right Recognised: yes ■ Crew assumed ATC would give guidance crosswind at 15-20 kts, which may be Managed: initially yes, finally no as to landing safety considered out of limits for a On final approach the crew had discussed contaminated runway. Below 300 ft the a non-standard missed approach between wind shifted direction to a tailwind two large cells. However, approaching the Errors Recognition / Managements component of up to 10 kts, thus threshold, the crew noted heavy increasing the groundspeed. The crew did thunderstorm and lightning activity on ■ Briefing Errors not notice nor comment on either of the missed approach path. At this point Recognised: no these wind conditions. the crew believed that a go-around was Managed: no no longer an option and became totally Approximately 20mins prior to landing, ■ Reduced Visibility committed to landing. the approach and landing brief was Recognised: yes conducted. The briefing did not cover the Managed: no ■ Deep Landing runway length or missed approach Late in the approach, at the flare stage, Recognised: no procedure- both critical items given the the crew lost forward visibility due to rain Managed: no situation. However, non-standard missed and were looking out the side windows The aircraft landed 3800 ft down the approach options were discussed later for runway information. This also 9000 ft runway, leaving 5200 ft. The crew during the approach when the crew contributed to the very long flare and did not realise they had landed deep or noted thunderstorms on the missed deep landing. The crew had briefed the that in the conditions the remaining approach path. use of rain wipe but these were runway was already already too short. ineffective under heavy rain. The aircraft Despite the deep landing, use of max ■ Runway Length Required had rain repellent capability reinstall reverse thrust was delayed by 17 seconds. Was Not Calculated about three years prior, but neither crew Recognised: no was aware of this reinstallation. Managed: no No runway distance calculations were determined for the conditions at the

20 focus winter 08 36499®Flight Safety iss 73 25/3/09 11:57 Page 23

time, ie, wet or contaminated runway. ■ Go-around Not Conducted Undesired Aircraft States Thus, the crew were not aware of the Recognised: no (minimal) margin for error available, nor Managed: no ■ Too high (90 ft) over the threshold which that the margin was eliminated in the The unstable approach, runway conditions, is 40ft above G/S. tailwind conditions. Two minutes before very poor weather and difficulty in landing, the runway length of 2743m controlling the aircraft during flare and ■ Deep landing 3800 ft down the runway. (9000ft) had been verbalised, although no touchdown were all cues by themselves to further discussion or action occurred. suggest a go-around. In combination, the ■ Unable to stop before departing the decision became even more prudent. runway end at 80 kts. ■ Conducting An Approach Into Heavy However, it was noted in THREATS, that Thunderstorm Activity the crew left this decision so late that a go- ■ The crew flew the aircraft into a ‘no-win’ Recognised: initially no, around also presented substantial risks, as situation, with both the continuation of finally yes the missed approach path was impacted the landing or the go-around resulting in Managed: no by heavy thunderstorms. The crew had potentially unsafe situation. Despite the threat of red radar returns committed themselves to a landing for along the approach path, the crew which they did not perceive there was any continued the approach. The error was alternative action possible. The crew had Other points of note: only recognised when the crew realised flown themselves into a no-win situation. the full extent of the severe weather, The initial CRM and communication between however by then the error was perceived ■ Deep Landing the pilots and between the cockpit and cabin as too late to manage (via a go-around). Recognised: no was, for the most part, good. The pilots Managed: no communicated their needs to ATC and ■ Crosswind Limits Exceeded The aircraft landed 3800 ft down the requested updated information on holding Then Landed With Tailwind 9000 ft runway, leaving 5200 ft. The crew status and weather. Recognised: no did not realise they had landed deep. Managed: no However, given the runway conditions, Approximately 2 hours before landing, AF358 The crosswind limitations for a wet tailwind and distance remaining after sent a revised ETA to Air France Ops in YYZ, runway had been exceeded, further adding touchdown the aircraft could never be and in return were sent parking gate to the workload of the crew in landing the stopped in time. information. However, the message did not aircraft. Then a tailwind component of up indicate that Red Alert had been in effect YYZ to 10kts was encountered on late finals. ■ Delayed Use of Reverse Thrust for over 1 hour. A Red Alert YYZ was similar to However, due to crew workload and Recognised: no a Red Lightning Warning at HKG, meaning distraction neither the crosswind or Managed: no that lightening strikes had caused ground tailwind issue was noticed. The PM failed to make standard after- operations to stop, although the airport was landing callouts for spoiler and thrust still open. Thus, there was significant terminal ■ Failure to Use Automation reverser deployment, delaying the PF's and gate congestion. It was not part of the to Full Capacity use of thrust reversers. Maximum reverse Station Manager’s requirement, to inform the Recognised: no thrust was not selected until 17 seconds crew of Red Alerts. Managed: no after touchdown. The PF was having a challenging time The airport operator is responsible for closing ■ managing the speed and disconnected Crew Assumed ATC Would Give the airport or any part of the airport. Toronto the autothrust at 300 ft. The pilot's Guidance as to Landing Safety Airport Authority does not close the airport mismanagement of thrust and speed lead Recognised: no for summer weather including rain, wind, to the aircraft being high and fast over the Managed: no thunderstorms and lightning.Although it does threshold. Leaving the autothrust The crew incorrectly assumed that ATC engaged may have minimised this error would provide guidance if the weather have procedures for closing a runway in and given the PF one less task to deal was unsafe to land in. ATC have no such winter conditions including ice, snow and nil with. Further, due to the high workload mandate. braking. Airports in Canada, USA and France situation, poor weather, and loss of visual INVESTIGATION REPORT cues near the runway, both pilots' attention was shifted outside the aircraft, “Having made their decision to land, the crew used all their energy concentrate on the task and thus airspeed and other instrument missed the cues that should have warranted review of that decision. The cues included; the runway scanning decreased. Use of autothrust looked like a lake; the aircraft deviated above the glidepath; the landing was going to be further down could have improved this situation. the runway than usual; the wind speed was reportedly increasing and the direction was changing; braking action was reported as poor; and the visibility became close to nil near the threshold.” Transportation Safety Board of Canada investigation report (4.2.2).

focus winter 08 21 36499®Flight Safety iss 73 25/3/09 11:57 Page 24

‘summer’ weather. Just because an airport is open, does not mean it is safe to land.

The Aim of TEM

The aim of using the TEM process to analyse this incident was to assist other crew in learning from the event. What would you do if this occurred on your next flight?

■ Review each of the threats encountered by the crew on this flight. What strategies do you have in place to anticipate and manage those threats?

■ Review the errors in the same way; what strategies do you have in place to recognise and manage such errors?

Reprinted with kind permission of Cathay Pacific KAI-TALK

(and many other countries) do not close for Officer had the ‘responsibility’ to ‘suggest’ a conditions of rain, wind and thunderstorm. missed approach if they deemed it necessary. However, many crew held the wrong perception that airports will close if weather conditions are too severe for landing. I’m sure Lessons Learned many CX pilots hold the same incorrect perceptions. ATC is only responsible to ensure 1 Have a ‘go-around mindedness’, rather the runway is clear of aircraft, equipment, than becoming fixated on landing. The people and other obstacles. ATC may restrict conditions where landing fixation is the flow of aircraft due to particular weather greatest (ie, very high workload) are conditions, but this is more to do with traffic usually the same conditions that most separation on ground or on air. The ultimate often require a goaround to be conducted. decision to takeoff or land lies with the pilot. Go-around any time a situation escapes your control or understanding. Within nine minutes, four aircraft had safely landed ahead of Air France, all in the same high 2 Understand the large increases in landing risk environment and at least one aircraft was distance due to small changes in conditions behind them. All of these crews had elected to (eg., tailwind, wet/ contaminated) or crew conduct an approach in similar conditions to Air actions (eg., slow selection of reverse France. This highlights the problem of hindsight thrust, high energy approach) bias based on outcome. I’m sure the airlines of 3 Approaches in thunderstorms and the preceding aircraft did not conduct an convective activity are hazardous, and the investigation into such a risky approach. risk is increased regardless of how many successful approaches a pilot has At the time of the accident, Air France had a previously made. policy that a go-around decision could only be made by the Captain, regardless of who 4 ATC do not close airports, and Airport was flying the aircraft. However the First Authorities may not close airports for

22 focus winter 08 36499®Flight Safety iss 73 25/3/09 11:57 Page 25

Wind Reports – not the full story

Prepared for UK Flight Safety Committee by Robert Seaman, Senior Applied Scientist, UK Met Office.

Robert Seaman is the Royal Meteorological Society adviser co-opted to the UKFSC. He is a Senior Applied Scientist at the Met Office, qualified forecaster, provides aviation meteorology training, holds a commercial pilots licence and is a part-time flight instructor with Aviation South West.

■ hreat and Error Management 2 minute average for local routine and T[Berman(Continental) & Dismukes special reports and for wind displays in air (NASA)] divides environmental threats traffic services units (ATSU).These reports into meteorology, terrain, airport and air must be representative of touchdown and traffic control. runway.

“Meteorological threats” may be defined as ■ 10 minutes for METAR and SPECI, except weather related events outside the influence that when the 10 minute period includes of flight crew that increase operational a marked discontinuity in the wind complexity of flight, increase pilot workload direction and/or speed, only data and require attention and management if occurring after the discontinuity shall be safety margins are to be maintained. used for obtaining mean values; hence, Figure 1: Concept of wind shear within the Combining FAA/CAA accident statistics from atmospheric boundary layer. Yellow 1995 to 2005 suggest that up to 43% of the time interval in these circumstances marker represents point of observation. weather related aviation accidents are due to should be correspondingly reduced. Colour indicates temperature (red= warm, wind meteorological threats, e.g. wind shear or METAR related anemometry provides the blue= cold). significant cross winds. A small sample of the general flow over an aerodrome. aviation community (conducted by Met Office The atmospheric boundary layer is the region 2005-2008) provided a useful insight into A marked discontinuity occurs when there is of air significantly affected by friction and heat pilot psychology and this particular threat. an abrupt and sustained change in wind transfer with the earth’s surface. At the top of When asked to rate in order of significance, direction of 30 degrees or more, with a wind the boundary layer there is typically a region wind threats were given a moderate to low speed of at least 20km/hr (11kt) before or of high velocity air, and at the bottom (close marking when compared to Cumulo-Nimbus after the change, or a change in wind speed of to earth’s surface) a region of nearly stationary (CB) clouds which resulted in only 2% of 20km/hr (11kt) or more, lasting at least 2 air, figure 1 shows a schematic representation. weather related accidents. Of course this does minutes. A different time scale is applied for The boundary layer “naturally” lends itself to not mean that CBs are any less dangerous, just gusts: “The averaging period for measuring wind shear in both speed and direction. In that pilots anticipate and recognise the threats variations from the mean wind speed(gusts) terms of direction, wind veers with height in posed by CB’s better than those posed by reported in accordance with 4.1.5.2c should the northern hemisphere, and backs with winds in general. This could indicate that the be 3 seconds for local routine and special height in the southern hemisphere. Indeed perception of winds as meteorological threats reports and for METAR and SPECI and for many pilots are taught to appreciate these compared to wind related accidents is wind displays used for depicting variations changes when applying wind correction during disproportionate. It could be a result of a from the mean wind speed (gusts) in air precision and non-precision approaches. shortcoming in the communication of traffic services units. [Recommendation]” relevant wind information (e.g. windshear ICAO Annex 3 sets out the various causes of associated with microburst USAir 1016 1994, It is important for flight crew to understand wind shear, including microburst associated NTSB/AAR-95/03) or indeed a reduced these definitions as the wind reported by ATC with thunderstorms/cumulo-nimbus, fronts, understanding of the context of wind reports on approach or take-off relates to a 2 minute turbulent boundary layer, inversions and that carries forward to errors in in-flight average at runway compared to a 10 minute topographical features. At some airports a decision making related to wind. average across the aerodrome that may be “windshear alert” is issued on ATIS broadcasts, obtained from METAR/ATIS. The 2 minute for example at Heathrow, where the criteria is ICAO Annex 3 sets out the regulations for wind report should resolve minimums and a mean surface wind greater than 20kt positioning of anemometers on an airfield, maximums in the surface wind field better (35km/hr), vector difference between the including measuring surface wind at a height and facilitate an improved decision on, for mean surface wind and the gradient at 2000ft of 10 metres (30ft) AGL, and how wind from example, whether to land or go around. Wind in excess of 40kt (71km/hr) and such instrumentation is reported. It states reports may be supplemented by onboard thunderstorm or heavy showers are within that “the mean values of, and significant instrumentation such as wind shear devices, about 5nm (9km) of the airport. If verified by variations in, the surface wind direction and with some airlines prescribing their use in an aircraft report, the alert becomes speed for each sensor should be derived and standard operating procedures. However, to “windshear forecast and reported”. If the displayed by automated equipment make best use of such information an overall criteria are met, but windshear is reported [Recommendation]”. These displayed values understanding of wind behaviour at low- then “windshear reported” is broadcast. should be averaged over a period of time: levels coupled with successful interpretation of weather forecasts and observations is necessary, improves decision making and augments flight safety.

focus winter 08 23 36499®Flight Safety iss 73 25/3/09 11:57 Page 26

and cannot be used solely on their own. Figure 3 illustrates a case where a surface wind observation can give a false picture of the wind threat on approach, climb or during take-off. When fast stable air flows perpendicular to a mountain range oscillations are set up in the flow i.e. mountain waves. To the lee of hills or mountains recirculation may occur over an airfield, otherwise know as a rotor. In this situation, anemometers placed at different Figure 2: The impact of atmospheric stability on turbulence and wind shear. positions on an airfield may show very different readings, for example, one may be indicating light and variable and the other a strong northerly.

To illustrate this figure 4 shows a rotor cloud over Mount Pleasant Airfield (MPA) in the South Atlantic with the camera facing north towards a small mountain range that runs from west to east across East Falklands. Generally, in the southern hemisphere stable air tends to arrive from the north, on this day ahead of a warm front and with a speed of 45KT (80km/hr) at 2000 feet (AGL). Yet the Figure 3: [Left] Concept of mountain waves in relation to a stable layer (thick red line) of air close anemometer at the airfield was reading to hill tops. [Right] The 747 air-bridge between UK, Ascension and Falklands regularly had to variable 5KT (9km/hr) at times as the rotor consider mountain waves at the Point of Safe Return (PSR). passed over it and northerly 40KT (71km/hr) when outside of the rotor (fig.4). Such mountain wave activity results in severe wind shear and turbulence typically in the vicinity of the rotor cloud top affecting approach and initial climb out, in this case at about 600 feet AGL. Flight crew of the air-bridge between the UK and Falklands (fig.3) had to consider Figure 4: Above: rotor cloud and mountain wave this wind threat frequently before and at activity over Mount Pleasant Airfield in time order. Point of Safe Return (PSR) it also affected Globally, this type of activity may occur near many daily commercial helicopter operations. airports in the vicinity of terrain. Interestingly, this type of mountain wave activity is behaving non-intuitively as the rotor retrogresses (moves north) against the strong northerly wind, highlighting the importance of understanding the Above: associated 2 minute average wind speed from airfield anemometer over period affected meteorological context of wind reports. by rotor activity. Wind reports oscillated from variable 5KT to northerly at 45KT (a significant cross wind at MPA). (Key: red = mean speed, blue = minimum speed, yellow = maximum speed). Once flight crew can visualise the concept of wind variation at low-levels it is then when a The stability of the atmosphere impacts on localised atmospheric instability it is not top-down analysis (fig.5) of meteorological the wind experienced by an aircraft at any difficult to see why they may be associated information comes into play, using weather particular altitude, highlighted in figure 2. with increased wind shear, gust strength and forecasts, wind reports and visualisation in Unstable atmospheres, such as polar frequency. Conversely, stable atmospheres, combination to increase situational maritime airmass, allow larger turbulent such as tropical maritime air mass, tend to awareness with respect to the weather and eddies to form through the vertical, resulting suppress turbulent eddies in the vertical anticipate impacts of wind threats on in occasional to frequent transfer of higher reducing transfer of higher velocity air handling or performance at critical flight velocity air from the top of the boundary between levels and increasing wind shear. phases. It is common to analyse weather layer to the bottom in the form of gusts. As It can be seen from figure 1 and 2 that surface from bottom up i.e. extracting relevant data rain showers are associated with greater, aerodrome wind reports do have limitations from and TAFs and then build up the

24 focus winter 08 36499®Flight Safety iss 73 25/3/09 11:57 Page 27

in figure 2 and 3. Using a low-level forecast limitations of such reports. The author also enables wind threats to be identified, such as hopes it has highlighted human factors in low level turbulence or mountain waves which meteorological interpretation as well as the are explicitly forecasted. This can be coupled importance to flight safety of placing any with wind reports, data from onboard wind report in a wider meteorological context, instrumentation, METAR and TAF output to through a top-down analysis process. quantify the impacts of the meteorological situation on wind at an aerodrome. Understanding the terrain around an airfield and the wind flow on any particularly day, coupled with forecasts then enables any wind report provided by ATC to be put into context and related to current in flight performance.

Figure 5: Top-down interpretation of Of course a lot of this process can be applied meteorological information in the pre-flight brief. In flight, that added piece of visualisation on how the wind is bigger (strategic) meteorological picture but behaving between the surface and airborne this is like constructing a jigsaw puzzle without reports, facilitated by full use of all available seeing the picture first. By interpreting the meteorological information, can help flight synoptic forecast a subjective assessment of crew better anticipate significant wind shear. stability and airmass may be obtained quite This brief article has defined wind reporting in quickly – relating the actual situation to ideas accordance with ICAO Annex 3 and suggested

Safety Management Systems Training and consultancy support

Safety oriented economic advantage, from the organisation chosen by EASA to train its staff in SMS

The aviation industry is facing significant challenges. With massive pressure and uncertainty on your business, it is doubly vital to effectively manage your business risks. We specialise in helping you to maximize opportunities and achieve your outputs with minimal losses. Having a compliant SMS will not help you in these challenging times, but having an effective SMS is proven to deliver proactive loss reduction. We have developed a training course specifically aimed at helping key decision makers understand how to do this... let us help you turn your SMS preparation into real advantage for your business.

Safety Management Systems for Decision Makers This one day, high-level course provides the necessary insight Dates: 28th January 2009 to contribute strategically to the Safety Management System 29th January 2009 discussions and planning. Location: Aviation Safety Centre, Fairoaks Airport, Surrey, UK

If you would like to know more or to book your place online visit our website at www.bainessimmons.com or call us on +44 (0)1276 855412

You know how to run your business - We know how to manage safety - Together we can be Great Partners

focus winter 08 25 36499®Flight Safety iss 73 25/3/09 11:57 Page 28

We may not know much about aviation....

For more information please contact Andrew Kirk on 01483 884884 [email protected]

proud printers of Focus Magazine