Nov. 10, 1953 F. H. ROBERTSON 2,658,701 FLYING CONTROL FOR AIRCRAFT Filed Oct. 12, 1949 2 Sheets‘Sheet 1 Nov. 10, 1953 F. H. ROBERTSON‘ ‘ 21553;?“ FLYING CONTROL FOR AIRCRAFT Filed Oct. 12, 1949 2 sheetsisheet 2 [:IIIIIHHHIIHIIIIHI lllllHHl. -_ v v 29 Patented Nov. 10, 1953 2,658,701 UNITED STATES PATENT OFFICE 2,658,701 FLYING CONTROL FOR AIRCRAFT Frank Henry Robertson, Carisbrooke, Isle of Wight, assignor to Saunders-Roe Limited, Isle of-Wight, England, a British company Application October 12, 1949, Serial No. 120,917 5 Claims. (Cl. 244—82) 1 2 .In modern large and/or high speed aircraft, Since the power unit only has to move the servo the aerodynamic loads on the control surfaces tab relatively to the control surface, it may be (i. e. the elevator, rudder, ailerons) are such that made considerably smaller and lighter than is the pilot, with his own unaided strength, is often possible when the power unit has to develop the unable to exert sufficient force to move the con 5 greater power required to effect direct displace trol surfaces manually or to hold them against ment of the control surface in relation to the air the applied loads. craft structure. A further saving in weight re To meet this difficulty, two alternative solu sults from the fact that the power unit consti tions have been proposed. The ?rst is the use of tutes part, and may in some cases constitute the power operation for the control surfaces. The whole, of the mass balance required for the con mechanisms involved are, however, complicated trol surface. and expensive, and there is always the danger The saving in weight which can be achieved of failure, with the result that duplication of the by the invention is illustrated by the following power units is advisable, as described for example example, which provides an approximate com in United States Patent 2,517,680 and in United 15 parison of the relative weights of three forms of States application Serial No. 92,794/49. The mechanism required to operate the control sur second is the use of servo tabs. In this system a faces of a given large aircraft: mechanical connection is provided from the pilot’s control member not to the control surface ((1) Pounds itself, but to a tab hinged to the trailing edge of Power control system operating directly on the control surface, the tab being arranged to the surfaces as described in United States move in relation to the control surface, on opera tion of the control member, in the direction op Patent No. 2,517,680 __________________ __ 1800 posite to that in which the control surface is to (b) move in relation to the aircraft, with the result 25 Pounds that the aerodynamic load on the tab, when dis Mechanical linkage for operating servo placed, serves to move the control surface to the tabs _ ___ ___ 1700 desired position. Thus, in the case of an ele Mass balance __________________________ __ 900 vator, when it is desired to depress the elevator the tab is raised, and when it is desired to raise 30 2600 the elevator the tab is depressed. Where servo (c) Mechanism according to the invention tabs are used the control surface must be mass balanced, both to hold it in adjusted position and _ Pounds to prevent flutter, with the result that the weight Electrical linkage for operating the power of the mechanism required to operate the control units ___ _____ 500 surface will exceed that involved by the use of Small power units for operating the servo a properly designed power control installation tabs ________________________________ __ 300 with which, if irreversible operators are included, ‘Mass balance __________________________ __ 600 mass balancing is unnecessary. The invention makes use of the advantageous 40 1400 features of both of the above described systems This example shows that the power control and provides, in an aircraft, the combination, system of United States Patent No. 2,517,680 is with a control surface ?tted with a servo tab, of considerably lighter than a comparable system a, variable speed power unit mounted on the con embodying mechanical operation of servo tabs, trol surface, so as to constitute a part at least and that the system according to the invention, of the mass balance thereof, operatively connect in which power units, constituting part of the ed to the servo tab and operable by the pilot’s mass balances of the control surfaces, operate control member to displace the servo tab to a the servo tabs, produces a further reduction in position in relation to the control surface deter weight. mined by the position of the pilot’s control mem 50 Another advantage of the system according to ber, and at a rate corresponding to the rate of the invention is greater safety. Having regard movement of the pilot’s control member. to the fact that the control surfaces are not Power operated ?ying control systems, in gen irreversible, as in normal powered controls, other eral, can be made lighter than manual ?ying outside agencies may be employed as safety de control systems. The system according to the 55 vices to move the control surface in the event of invention provides further saving in weight. failure of the power system. Moreover, even if 2,658,701 3 4 no such emergency safety devices are provided, electric motor 29 (Fig. 2) which runs continuous the control surface is free to float to a neutral ly to drive a variable delivery hydraulic pump 32; ' and relatively safe position under the aero this pump 32 drives a hydraulic motor 33, and dynamic loads in the event of power failure. this in its turn operates one of the sections l9 of Furthermore, as a safeguard against failure of 5 the servo tab. The hydraulic pump 32 is of the the power unit, the control surface may be pro swashplate type and its delivery mechanism is vided with. a- plurality of power;v unitsathe. tab -~.-.control1ed byithe planet carrier-=34 .of a differen being .split; into; sections each? operatedjby‘ onezof i .tial gear35,:one=sun‘wheel 36 of which is driven the power units and the power units being oper by the associated receiver 2| and the other sun ated in synchronism by the pilot’s control mem- .: 1c ‘wheel 31 of which is driven by a feed-back shaft her, as described in United States application 38 from the output side of the hydraulic motor Serial No. 92,794/49. Then, notwithstanding "’33,"“the‘-shaft'-i38 and sun wheel 31 constituting a failure of one of the powerunits, thep?otwill be ;. follow-upmechanism. able to maintain sufficient»controlaoventhe posi .~ *Norrrially, when. the elevator is stationary, there tion of the control surface with.;;,the;;aid :ofzthe .15 .;is.-no:delivery§from the pump 32 and the hydrau others. 110 motor 33 is,,of course, stationary. As soon as In the case of large aircraftjlthe’power "unit * the 'control'c‘olumri I0 is moved the receiver 2! is will normally be operated from the pilot’scontrol .caused to execute a corresponding movement and member by a master and slave unit, comprising a turns the ?rst sun wheel 36. Since the follow , ,transmitterconnected to the pilot’s control mem 20..up...mechanism,. and thus the second. sun-wheel ...ber.,and.' a remote -receiver located. adjacent the f. .3 l, ..are stationary‘, the‘effect isto' turn‘ the "planet power unit and serving to followfthemovement . .carrief 34..and'thus,to' move a‘leverK-not’shown) imparted-to. the , transmitter by the .pilot’s control utolstart“ delivery in theappropriate direction‘from member. .An appropriate’ form ‘of. master. and "the pump. "This .causes ‘the hydraulic‘ motorrto slave-unit , is .an ,electricalnnit .ofthe Selsyntype. 25rstartand toy drive, ‘at a speed 'determin'ed'byithe . Preferablythe power. unit. is constituted. by a rate of movement of ‘thecontrolc'olumn "10-;’the continuously. running '.e1e.ctric.motor,. a ‘variable associated section i9 of.the servoitabthrough' a .. .delivery . hydraulic pumplidriven- by the...electric . reduction gearing Z3, alsh‘aft‘24 and bevel gearing motor, and a.hydraulic.motondrivenbythe pump T25. ' The section'i9 of‘the‘servo‘tab is‘hin'ged'to and arranged to actuate the tab, thenpi-lot’s'con 30'. the elevator on an axis“26.“"The Zshaft1 il-drives 51.131101, member. serving .to- vary. the delivery of: the pump .. and: a. f0l-10W.-.-.up..gear. being provided .for causing i the. second‘ 'sune'wheel‘ 3 1‘ :of the-differen returning the. pump .deliveryto zerolwhenthe tab . tial gear to r'otate.."Since"'.the'?rst sun=wheel1"3& : hasexecutech the desired rnoven'1ent.-~v Othenforms -isnowistationary,;theieffect is; agaimto‘rotate‘the .of. variable .speed . power-unit = may, however, .-be' 35. planet-carrier;34,...the gearingUoFthe followaup used if desired. .mechanism. being such as'tdm'ake'the rotation A preferred ?ying control system according to vOpposite. to its original' dire'ct'ron. “The 'delivery I the invention will nowvbe described in detail, by “way of example, with reference to its application ., movement of 'the. tab ‘section’ "I 9 "corresponding‘to to the control of an elevator; but" it “will be under 40 that ‘of-the control ‘column 'io'has'been- produced, stoodthat an exactly similar ‘system may- be‘ used the‘ deliveryiis ‘stopped'and‘ movement‘ ‘ceases. "- tin-‘conjunction with anyor all; of the other con "The. power u'nit'iil is vmou'ntednon'.a‘“blacks-t trol surfaces, i. e. the rudder or ailerons. , 39 ."(Ffigf3)" ?X‘ed'to ‘the ‘elevator’ "16 'on' theiside -.The preferred system in question is shown in the accompanyingwdrawings; .ini- which: 45 the velevator.