Nov. 10, 1953 F. H. ROBERTSON 2,658,701 FLYING CONTROL FOR 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

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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 , , ) 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 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. ‘It’th'er'efore constitutes'part?at aiFig. 1 is a diagrammatic layout ofthef-com least; ‘of .the' mass" balancewequired 'for the ‘ele epletesystem insofar as it relates to,thew.eleyator, vator. “.As indicated in‘chahrdottéd'linest‘in‘Fig. . . Fig. 2 is a plan view of one of the power units .3, .when‘the servo» tab‘iS is raised‘inrelati'on and associated receiver and gearing, and ,toilthe ‘elevator3’l6,"‘the‘ latter.‘ is depressediiin Fig. 3 is adiagrammatic section through the 5'9 relation ,tolthe ‘tail plane ‘llifoy'the‘aerodynamic elevator ‘showing‘the power unit and'the mech jforcesuacting onithe. servo tab,‘.lthe"elevatorias aianism whereby it actuates the servo tab. .~ ,suming. a~ . position‘ determined .by i the, displace =ment .of'-_the::servo...tab. from -the -neutral, posi~ m-to a .shaftina gearbox I I .so. .that-forecand aft n .».tion~.shown in fulLlines. -. Sim-ilarlyr if..the .servo movementvofl the. controlizcolumn '1 lhwillwrotate "0vtabsissdepressed,» the: elevator~will be raisedin ;the shaft. - .As fully . described in .United; States relation-to the tail‘ plane to a~position-,-determined zapplication. Serial .No.. .92,'794,/.49,.-the1lshaft i ?xed tbylthe displacement of the-servo.v tab. ~to-the control column in is geared to a shaft l2 What I claim asirnyzinyenti'on-zand;desirerto FzfOll‘. operating four Selsyn transmitters l3, so that r~~esecure .rby. . Letters-Patent wis: .the. actuating member ofv .eachetransmitter re-l '. 1;.111 arr . aircraft,‘ . the" combination of. 9.11601] ._ ceives. a. movement .corresponding. -.in ‘magnitude .ztrolasurface, asservo :tab hinged to Ethe itrailing .and...direotion. .to. that. or the control column .I 0. *edgeeofrisaid: .contr‘oL surfaceg-aipilot’s .control Associated _with. the, gearbox. .l L. and. as. fully -memb_erioperati~vei on ‘said =servo‘ .tab only, {to .the "described in United States application Serial No. 65T'6X01US1OI1‘ of .saidrzcontrol :surface itself, .tolini " '92,'7>9.1i/4_9,_ are .the servomotorl 4 of. an ‘automatic . tiate‘rmovement of.~ said: control-"surface; a‘ ‘vari , pilot and a feel generator 15. :able' i speed-3: power ‘ unit mounted; on said. control "The elevator .! 6 (see also Fig. 3) ,is-freely hinged :surface: andwzcon'stitutingy. in' part". at 1east,~-a to a tail plane I‘! for movement about an axis l8 mass. balance ‘therefor; :an, operative rconnection .and. carries aservo tab .~I9_dividedrinto four :sec 70 -~between";said‘ power unit: and-said. "servottabp- a .itions. Each‘ section of ,thesservo tab >l9~is oper vconnection bEtWBEIl‘iSaldTDi‘IOt’S controlv member ated. by apower unit 211, which is-in turn‘actuated and saidspower :unit 51501" rendering: said ‘power .bywa 'Selsyn receiver; 21, each -.-receiver; 2 Lbeing unit operative; when'everthe pilot’s’control mem ‘electrically connected ,bya .cable. 22 -to..the. associ Eben-is 5 moved, =tottdisplace' said:»servo tab to 1a atedLtransmitter .I 3. sposition'ande at a rate, determined‘ respectively Each powerunit 20 comprises-a constantqspeed 75 bythe amplitude, and. rate of-movementof the 2,668,701 5 6 pilot’s control member, and thereby to impart constantly running electric motor, a hydraulic corresponding movement to the control surface. pump, having a variable and reversible delivery, and means for terminating operation of said driven by the electric motor, a hydraulic mo power unit on arrival of the servo tab at a posi tor driven by the hydraulic pump and serving tion in relation to the control surface selected to operate the servo tab, the pump being ad by the movement of the pilot’s control member. justable by the pilot’s control member to drive 2. In an aircraft, the combination of a con the hydraulic motor in a direction and at a. trol surface, a servo tab hinged to the trailing speed corresponding to the direction and speed edge of said control surface, a pilot’s control of movement of the pilot’s control member, and member operative on said servo tab only, to the 10 a follow-up gear between the output side of the exclusion of said control surface itself, to ini hydraulic motor and the pump for terminating tiate movement of said control surface, a vari the delivery of the pump when the servo tab has able speed power unit mounted on said control assumed the position selected by the pilot’s con surface and constituting, in part at least, a trol member. mass balance therefor, an operative connection 15 5. In an aircraft, the combination of a control between said power unit and said servo tab, a surface, a plurality of independently movable master and slave unit comprising a transmitter servo tabs hinged to the trailing edge of said connected to said pilot’s control member and a control surface, a pilot’s control member opera remote receiver connected to said power unit tive on said servo tabs only, to the exclusion of and serving to ‘follow the movement imparted 20 said control surface itself, to impart movement by the pilot’s control member to the transmitter, to said control surface, a plurality of variable said master and slave unit serving to render said speed power units mounted on said control sur power unit operative, whenever the pilot’s con face and constituting, in part at least, a mass trol member is moved, to displace said servo tab balance therefor, each of said power units being to a position and at a rate determined respec connected to one of said servo tabs, connections tively by the amplitude and rate of movement between said pilot’s control member and said of the pilot’s control member, and thereby to power units for rendering said power units op impart corresponding movement to the control erative in synchronism, whenever the pilot’s con surface, and means for terminating operation of trol member is moved, to displace said servo tabs said power unit on arrival of the servo tab at 30 to a position and at a rate determined respec a position in relation to the control surface se tively by the amplitude and rate of movement lected by the movement of the pilot’s control of the pilot’s control member, and thereby to im member. part corresponding movement to the control 3. In an aircraft, the combination of a con surface, and means for terminating operation trol surface, a servo tab hinged to the trailing 35 of said power units on arrival of the servotabs edge of said control surface, a pilot’s control at a position in relation to the control surface member operative on said servo tab only, to the selected by the movement of the pilot’s control exclusion of said control surface itself, to ini member. tiate movement of said control surface, a vari able speed power unit mounted on said control 40 FRANK HENRY ROBERTSON. surface and constituting, in part at least, a mass balance therefor, ‘ an operative connection be References Cited in the ?le of this patent tween said power unit and said servo tab, an elec trical master and slave unit comprising a trans UNITED STATES PATENTS mitter connected to said pilot’s control mem Number Name Date her, a remote receiver connected to said power 1,827,304 Thurston ______Oct. 13, 1931 unit and an electric cable connecting said trans 2,057,877 Bragunier ______Oct. 20', 1936 mitter and receiver, said receiver being adapted 2,325,548 Roos et a1 ______July 27, 1943 _ to follow the movement imparted by the pilot’s 2,340,524 Fischel et a1 ______Feb. 1, 1944 control member to the transmitter, and said 2,371,388 Glenny ______- Mar. 13, 1945 master and slave unit serving to render said 2,470,968 Aske ______May 24, 1949 power unit operative, whenever the pilot’s con 2,517,680 Knowler et a1 ______Aug. 8, 1950 trol member is moved, to displace said servo tab 2,601,962 Douglas ______July 1, 1952 to a position and at a rate determined respec tively by the amplitude and rate of movement 55 FOREIGN PATENTS of the pilot’s control member, and thereby to Number Country Date impart corresponding movement to the control 572,494 Great Britain ______Oct. 10, 1945 surface, and means for terminating operation 627,858 Great Britain ____ .d Aug. 17, 1949 of said power unit on arrival of the servo tab at a position in relation to the control surface 60 OTHER REFERENCES selected by the movement of the pilot’s control “Aviation Week,” published weekly by Me member. Graw-Hill Publishing 00., 99-129 N. Broadway, 4. In an aircraft, a combination as claimed in Albany 1, N. Y.; Sept. 12, 1949; pages 23 to 30 claim 1, wherein said power unit comprises a and 33, page 30 relied on.