1、. REPORT 1304FLIGHT INVESTIGATION OF THE EFFECTIVENESS OFCONTROL DEVICE FOR PERSONALBy WILLIAM H. PHILLIPS,HELWT A. KUEHSEL,and .AN AUTOMATIC AILERON TRIMAIRPLANES JAMESB. WEIITTE.NSUiVfMARYAight investigationto determinethe eectivenew of an au.to-rnaticaileron trim control deviceinstalledin a perso
2、nal airplaneto augment the apparent spiral stability has been conducted.The deviceutilizeg a rate-gyro sensing elementin order to switchan on-o type oj control that operatesthe ailerons at a$xed ratethrough control centering springs. An analytical study usingphase-plane and analog-computermethodshas
3、 been carried outto determine a desirable method oj operation jor the automatictrim control.Rmult$ indicate that tb device is capable oj maintaining theairplane in equilibrium over its operational speed range underdirectional out-oj-trim conditions that would cause rapid diver-gence oj tlebasic airp
4、lane. The device also prevents excessiveheading wander and airplane gyrations in turbulentair withoutpilot control, A meansjor holding the airplane in a stabilizedturn tofacilitate mild maneuveringthroughthe automaticcontrolis provided.INTRODUCTIONAs a result of the present interest in the spiral-st
5、abilityproblem associated with most personal-owner airplanes, theNational Advisory Committee for Aeronautics has undert-aken a program to investigate the eflactiveness of a spiral-stlability augmenting device, The specific problem facingthe pilot of u personal-owner airplane is to maintain his air-p
6、h-me in wings-level fllght during times when ho has no natu-ral-horizon reference and to keep the airplane. from divergingspirally while he may be preoccupied with navigational prob-lems. It is demonstrated in rofwence 1 that tk pilots senseof orientation is unreliable in the absence of u visual ref
7、er-ence, as may he the case when inadvertently or unavoidablyencountering instrument weather. Also, many personal air-pknos are. equipped with only the bnsic instruments for in-strument fligl t (turn inclicator, ball-bank indicator, alti-meter, and airspeed meter). Considerable proficiency iinstrume
8、nt flying is required t,o int crpret tlm indications ofthese instruments properly and, in many cases, personal-airplane pilots are not sufficiently skillecl in instrument flyingto undertuke it with safety,AILhough most present-day personal-owner airplanes,particularly those with high-wing designs, p
9、ossess a slighLdegree of inherent spiral stabiliLy in cruising flight (ref. 2),they show unstable spiral tendencies under operational con-ditions. The main reasons for this apparent spiral instabilityare a lack of means for trimming the airplane laterally ordirectionally, a variation of lateral and
10、directional trim withairspeed, ancl control-system fric Lion wilich prevents thecontrol surf aces from returning to trim position after a con-trol deflection, even if there had been a means for initiallytrimming the airplane.The use of preloadcd control centering springs to allwititethe control fric
11、tion problwn is reported in reference 3. Inreference 3, con Lrol centering devices were used on theailerons and rudcler with mechanical trim devices built. intothe centering units, The results of this investigation showthat the apparent spiral stability is improved by the use ofcontrol centering spr
12、ings as long w the surfaces arc preciselytrimmed for a particular flight condition. III order to becompletely satisfactory, however, there is need for a means ofautomatically compensating for the late.rul and directionaltrim changes resulting from changes in airspeecl, power,lo,acling, and altitude.
13、The purpose of the present investigation is to cletwminethe effectiveness of an automutic trim device intended tocompensate for the aforenumtioneci variables aflecting lat eraland directional trim. The automatic trim device is designedto cleflect the ailerons by shifting the trim position of prc-loa
14、ded control centering springs in order to maintain zeroyawing velocity,In the course of the analyses and tests, itt became pparentthat with certain minor additions the aileron cent rol devicecould perform functions o tl.wr than simply keeping tho air-plane trimmed laterally. It was possible for the
15、device toprovide rapid recovery to level flight from a banked attitude,to maintain a heading in smooth air with controls free forfairly long periods of time, to discourage large headingchanges during flight in turbulent tlir, and to allow accuratecorrections in heading for navigation purposes. In th
16、eserespects, the aileron control d wice performed funct ions of anautopilot with consiclembly less complication Lhan tinyconventional autopilot known to be in use at present,ISwm?edes NACA Twlmical h-ote3637by WilliamE. Phillips, Helmut A. Kuehnel,and James B, WhItten, 1956505Provided by IHSNot for
17、ResaleNo reproduction or networking permitted without license from IHS-,-,-REPORT 1304-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICSSYMBOLSwitlg spat, ftmljitlrary c.onstantl of ilt egrut ionlift coefficient, Lift/qSlateral-force cocffic.ientva ritit.ion of Iateral-force coeffic.ientl with sideslipwla
18、pwriation of lateral-force. coeflkientl with ruddercleflec.tion, wylad,Rolling momentrolling-momenl coefficient,(JYbVarifl.tion of rolling-moment c.oeffichmt with rolling-1pbwygulw-velocitly factor, aol ot hwwise, t h.lfig in the colrwl opw:ll ion mightcause dynamic instti.bility, The resulting powe
19、r rwpirr-mcnts are much grent w tlml WOUMbe nwdwl t o op(mit rthe controls ut n slow rate to oftwt. t.h spi.rid diwrgcnw of una.irphme.A gyro sensing angulw wlociiy was select cd to opww t i!the device because. such a gyro is simpler wd Iess expwsi wthan a displac.envmt gyro, Bwausc tingh: of roll i
20、s propnr-tiomd to yawing velocity during a st wwly t mm, u yilw rut rgyro performs the wune function in t.lw pwsont appliwt hmas a. roll a tt it.ude gyro. Both these instrunwtlis wwuld tlvtthe clisaclvs,nttige of allowing slow chunges in hewling withilthe resolution of the instrument. A nwms of Wwil
21、g (lirw-tion with respect to geographical or nmgwt iv rrfwww(:swoukl be required t.o nmint nin hcnd illg m 1M unt ovw 1(-)IlxProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-INVESTIGATIONOF THE EFFECTIVENESS OF AN7AUTOMATICAILERON TRIM CON1ROLDEVICE 5
22、07periods of time. Because the main purpose of the presentdevice is to prevent excessively steep spirals during instru-ment flight, the rato gyro was considered adequate.The preloaded centering springs were considered anessential featu.rc of the device in contributing to safety underemergency condit
23、ions. These springs require a definite forceto displace the aileron control from the trim position. If,under instrument conditions, the pilot, becomes disoriented,he is assured that on releasing the control the ailerons willsnap to the position required to maintain the wings level.With a less positi
24、ve method of applying torque to the aileroncontrol system , coutrol friction might, interfere with thecorrect operation of the device. The prelocided cent wingsprings were shown in reference 3 to be deshwbe duringcross-country flight where frequent maneuvering is notrequired. Provision could bc made
25、, of course, for reaclilydisconnecting the device under contact flight conditions ifdesired.The preceding discussion has presented the justificationfor the basic idea of the aileron trim device. This cleviceis now analyzed by using phase-plane and cumlog-computermethods. Ilodifications for overcomin
26、g stability problemsassocicd ed with the basic system me discussed.ANALYTICAL STUDY OF AUTOMATIC AILERON TRIMCONTROL DEVICEPHASE-PLANE AND ANALOG-COMPUTERSTUDYA nonlinear system such as the aileron trim device maybeanalyzed by the phase-plane method. In this rnethocl, themotion of the system is calc
27、ulated by plotting velocityagainst clisplacement, For the present system which isintended to maintain the airplane near zero roll, a plot ofrolling velocity as a function of roll displacement is mostsuitable.The trajectories of the motion in the phase plane may bereadily talc.ulate.d under the simpl
28、ifying assumption that,for the long-period motions under consideration, the rollingvelocity is proportional to the aileron deflection. Thisassumption neglects lag in development of the rolling motionand considers the inherent spiral stability or instability ofthe airplane to have a minor effect on r
29、oll rate as compared-with aileron deflection. The rolling velocity is then givenby the formulab 6.C18_=s277 cl,orIf the ailerons are assumed to move at a constant rate =+lthis trajectory, it. mayThe value of is zero for this trajectory, and the minus signis used to correspond to trajectories for whi
30、ch d and hu.veopposite signs. Substituting the value of from ecluation(5) into the left-hancl side of this ecuat ion gives! (%,”-=*PIf this value. is equt-ttwl to the value of r/p in equation (7),the value of gyro tiIt, which gives a dead-beat return fromany given rol! angle may be determined as fol
31、lows:For the conditions given in table I (= 140 mph) aucl aninitial roll angle of 40, the gyro-tilt angle is 38.4, withthe gyro inclinecl nbove the flight path. If the airspeed isreduced to 90 mph! the tilt is 55. PiTotc thut the changein angle of a.ttad due to the. reduced airspeed automat,ictdlypr
32、ovides some irtcremw in gyro tilt in the required direction.For the part.icuhw condition um.ler c.onsiclerwtion, the amgle-of-ti.ttacli change of about 10 M the airspeed is reducedfrom 140 mph to 90 mph is compmwd with a change in t.iltof 16.6 mlcula ted for optimum response.DESCRIPTION OF APPARATUS
33、 picto-rid diagram and circuit-wiring diagram of the aut.o-nmtic. control device is shown in figure 6. The pictorialdiagram indicates schematimdly the int erconnect,ion of thevarious components deseribcd substqlwntly. 1lw iutw-connection is shown iu detail itl t k circui-w king ditlgranl.A photogmph
34、 of the rate-gym imt alhl timl is slmlrl illfigure 7. This gyro is U Vell-c(lllstrlctctl unit t:dwll fromother equipment and is pmlmps larger and more sensit iwthan necessary for the job. The unit has u 5.2-wmr(! rolorwith a rotor monwnt of inwt iti of about 0.24 1-in.illu Ir-quires 2S vohs tit: 0.2
35、2 wnpwv. Tlw unit hm Imill-illelectrical contacts aud a means Ior clcclricully Uppl.villg Ittorque about the gyro precession axis.The a.ctualor unit, wmsist ing of t.ho prohmltvl tilwt.1centering springs and the clec.tric motor tmd gym Im, isshown moun t.cd on the. control cuhunu it figure $. Jiglr,
36、*9 shows the force chmuctwistirs of the ttilwon cotlrol sysl (mas measured on the ground. As seen from this ilgurl, Ilitpreload is about. equal to tht st.wtic (tltl(1-systcrfrictiowThe electric motor is a small, pwmanmt -niglwt typ( ofunit internally reared down to 250 rpm. I?xlernul gv:wing- .,of t
37、he motor reduces the jark-wrew rot 11tiold spwd to tltmu 42.4 rpm. The resulting linear speed of the jtirk-srrew uu 1is about 4 in,/min and results in total dcftwtioll rtllu of lhuaileron of 1.5 per second. Automat it-lot al-ailwm lmvvlis lirnit.ecl to about, + 5. The power req uirenwnt for t twactu
38、ator is about. 0.2 to 0.3 ampcru at 2S wlts umlw mwnmlload. hmutd aikron rent.rcd of dw Uirphuw is avniu lJkat, all t.imcs by overpowering W preloadwl mn trol C(W1wi tlgsprings.Swit chw sensitivo to tiilemn wheel form are moullf WIbetween the control-wheel shafh and th cent rol wmd.About 2 of rotati
39、ontil free play is provided WWW11 t I(?wheel and shaft Two nticroswitc.hes me mount ell rigidlto the wheel shuft, md an mm that rests betwctm the nlicro-switeh buttons is mounted rigiclly to the mm t.rol wlm. I%(control wheel is prdoadwl to tlw centrr of thu frre-pl,szone between wheel and wheel sht
40、dl. This preloiid is ad-justed to maintain both of the switches in wl oft comlit iwlwhen no force is applied to the wheel. - JlOttJJttll Of III*force-switch illst.allaf ion is shown in iigurc 10, tuld t.hc posi-tion of these switches in the system is shown ill figurr 0.These switches tire ac.tuaictl
41、 by m rulatiyely light whrclforce (less than that of the aikmm preloMI,I ttnd, tw SW1lfrom figure 6, upply a voltage t.o the torqui! coil huih ituthe gyro unit. By this means, a t orqm is qplid t u t.lwgyro about its prwession axis, thus chwiug II gyro WIWIWand exciting the aihuun servornot.cw. Thr
42、rwult ilg tlilwt HIcleffcctiou establishes a turn mte which will st ililiw LIipoint Where the precession torque due to t IN: turn rat( isequal and opposite to the ehctlricnly tippliwl prwwsiotltorque. An electlrictil prwwssion torquu cquivolellt, to tlultresulting from a turn rtlte of 3 per second w
43、as usml.The control circuitry consists of a relay pair w:tln t rd 1).sthe gyro contacts for the purpow of switching he AI t.ivcl.vhigh current. t.o the tictuu._. -_ -_-, ,-1 1 n ! Forceswkhes1, 1h1It/I1 - . - - -.-_-_ - -,; Tya.yez- J!28VORC 6-C II+offPower ,switch ,+ Inchco+es .0 connectan11+ Mmate
44、s electrical CxmnecticmAilerons ,/ motor(b) A(b) Schematic wiring digram of control circuit.I?IGITREfiCOnChMIfxi,F1ouR 7.Phot.ograph of rate gyro im.tailed in the test airplane.TEST AIRPLANEThe test vehicle- used for this investigation is a tiypicdhigh-wing personal-owner nirplane shown in the photo
45、graphin figure 11. (20mp1et details of the airplane are td.mlatedin rc.ferenc 3.The basic airplane does Dot incorporate tiny means fordirectiomd trim but does have an adjustzdk bungee ailerontrim device,INSTRUMENTATIONStamla.rd NAQA recording instruments are employed torecorcl indicated airspeed; pr
46、essure alt,itude; yawing velocity;rolling veloc.it y; heading change; pitch angle; sidedip angle;roll angle; and nornd, t.mmsverse, and longitudial accelerat-ion and control positions, referred to the fixed surfaces.Static and clynwnic pressures for the altitude and airspeedrecorders are t.ake.n fro
47、m the a.irplanc system which Ims anapproximate ?4 16 8 0 816” 24 32 4(3Left RightTotal oilemn cteflectian, S., degFIGURE 9.Grmmcl measurement of thu prtkmdrd :tilwon wntlv-ing-spring force-deflect ion char: tctcrist im with inrrwtsing Nnd dwm ,:tsitgwheel force.Provided by IHSNot for ResaleNo reprod
48、uction or networking permitted without license from IHS-,-,-INVESTIGATION OF THE EFFECTIVENESS OF ANFIGITRII10.Photograph of the force switches nwunkd on the controlwheel shaft of the test airplane.FIGURE 11.Photograph of test airplane.of the wing at ubout one-half span. The airpkme pilotsinstruments are supplemented with a gyro horizon anddirectional gyro to assist in pilot evaluation of the effec-tiveness of the automatic device.AuLomatic-control actuator position is recorded and pre-sent ed as control aihwon deflection on the time-history plotspresented subsequently. This record trace pr
