1、daNATIONAL ADVISORYCOMMITTEEFOR AERONAUTICS.TECHNICAL NOTE 3676INVESTIGATION OF LATERAL CONTROL NEAR THE STALLFLIGHT TESTS WITH HIGH-WING AND LOW-WINGMONOPLANES OF VARIOUS CONFIGUWTIONSBy Fred E. Weick and H. Norman AbramsonAgricultural and Mechanical College of TexasWashingtonJune 1956. . . Provide
2、d by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECHLIBRARYKAFB,NM+,. .NATIONAL ADVISORY COMMITTEElllllllllllpjpglgFOR AERONAUTICS - .INVESTIGATIONTECHNICAL NOTE 3676OF LNIERALCONTROL NEAR THE STALLFLIGHT TESTS WITH HIGH-WING AN!),IL)W-WINGMONOPLANES OF VAR
3、IOUS CONFIGURATIONSBy Fred E. Weick and H. Norman AbramsonSUMMARY.-, This report, the second in a series dealing with the problem ofcontrol near the stall, presents the results of flight tests with severaltypical light aircraft. It has been found that, for all of the aircrafttested, adequate lateral
4、 control is available up to some critical angle0 of the angle of attack for maximumof attack that is always within 2lift. The elevator deflection required to trim at this condition hasbeen found, with power off and power on, for each of the aircraft tested,as well as the elevator deflection required
5、 to make a three-point landing.Flight tests were made with one airplane having two different hori-zontal tail configurations in an attempt to provide an arrangement thatwould give near-optimum conditionswith regard to the effect of powerchange on longitudinal trim near the stall. This attempt was su
6、ccessfulwith one d the configurationstested, so that under all of the conditionsof power setting and center-of-gravityposition tested the availableelevator deflectionwas sufficient only to maintain the angle of attackat a point where lateral control remained adequate. The increase inminimum speed wa
7、s negligible.These results are intended to provide quantitative flight-testinformationwhich may be useful to designersfor adequate low-speed control and which mavanalyses as presented in the(TechnicalNote 3677).third and finaiINTRODUCTIONThis report presents the results of thetigation into the possi
8、bilities of obtainingthe lowest flight speeds of light airplanes.program was reported in reference 1.in attempting ;O providebe correlatedwith analyticalreport in this seriessecond portion of an inves-reliable lateral control atThe first portion of theProvided by IHSNot for ResaleNo reproduction or
9、networking permitted without license from IHS-,-,-, ,.2 NAC!ATN 3676This investigationwas based upon the hypothesis that satisfactoryrolling control is obtainableby a humsm pilot only if the lateral sta-bility factor, damping in roll, is positive. Positive damping in rollis, in turn, dependent on th
10、e slope of the lift curve where an increasein angle of attack is attended by an increase in lift. It then follows,- that, in order to retain,:ufficientrolling control under all conditions,the outboard elemenl% of a wing must be prevented from stalling at thehighest angles of attack maintainable.Flig
11、ht tests have shown that, when an airplane is in swing tesof tests.Determination of maximum angle of attack below stall at which lateralcontrol is still available in gusty air.- As explained in reference 1, thetest for satisfactory lateral control was made to simulate gusty ah condi-tions which are
12、more critical than still air conditions. The mive at the highest angleof attack and lowest speed that could be maintained. In the progran ofreference 1 this spin conditionwas investigatedfor comparisonwiththe critical angles of attack found in the roll-recovery tests. In thepresent, or second, porti
13、on of the investigationthe spin trials weremade with the hterstate S-IA and the Ag-1 airplanes but not with theFairchild FT-19 because of the age of the wood wing structure.With the Interstate airplane power-off spins could be obtained withmore than 15 of up elevator with the forward center-of-gravi
14、tycondition .and more than 6 with the rearward center-of-gravitycondition. Thesevalues me both about 8 lower than the elevator deflections givingsatisfactory lateral control under the simulated gusty air conditions, wProvided by IHSNot for ResaleNo reproduction or networking permitted without licens
15、e from IHS-,-,-NACATN 3676 9ha conditionwhich may possibly be explained by the powerful rudder.ofthis airplane.dThe Ag-1 airplane, with the center-of-gravitycondition tested,could not be made to spin under any condition of power or flap setting.Longitudinal trim change with application of power.- Th
16、e test resultsdiscussed thus far have shown that there is a critical angle of attack,within 2 of the angle for maximum lift, below which adequate la+erslcontrol is available. However, the attainment of this critical angleof attack required widely different elevator deflections for power-onand power-
17、off flight and for different center-of-gravitylocations.Therefore, the Ercoupe airplane was tested with two different horizontaltail configurations in an attempt to provide an arrangement that wouldresult in a negligible change in the elevator deflection required fortrim with change in power setting
18、.The two tail configurationstested were both modifications of thew-original tail and sxe shown in the photographs of figure 8; a comparisonof the three tails is shown in figure 9. It willreadily be observedthat the modifications were attempts to move the elevator out of the.region of influence of th
19、e slipstream; the elevator smeas in the twocases differed considerably.Results of flight tests with modified tail 1 are given in figure 10.The first plot (fig. 10(a) shows true indicated airspeed versus elevatordeflection for power-on and power-off conditions. At a true indicatedairspeed of about 49
20、 mph a partial stall was encountered in the power-off condition. Flight observations of tufts p,lacedon the wing surfaceshowed that separationwas occurring over the rear portion of the wingnear the fuselage. Ey modifying the elevator control linkage to increasethe upward deflection available, data w
21、ere obtained in the power-offcondition through a portion of this range. The wing sngle-of-attackvariation with elevator deflection is shown in figure 10(b)j it isreadily seen that rather high angles of attack were attained in thepower-off condition. Finally, the third plol;(fig. 1O(C) shows liftcoef
22、ficient versus angle of attack; the region where partial loss oflift occurs in power-off flight is very clesr.A few tests were also made with rather lsrge fillets installed atthe wing-fuselage juncture (see fig. 8). The standardErcoupe shsrpleading edges adjacent to the fuselage were eliminated for
23、these tests.The fillets were installed in an attempt to eliminate the burbled flowin order that data might be procured in the lowest speed region attain-. able. The only noticeable effect of the fillets was to increase themaximum lift coefficient and the angle of attack for maximum lift in thepower-
24、off condition.4,The results of tests performed with modified tail 2 sre given infigure 11. As with tail 1, tests were conductedwith the large filletsProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-10 NACATN 3676installed. Again it was found that a sl
25、ightly higher lift coefficientin the power-off conditionwas attained.It will be noted from the plots of figyre 11 that, although theminimum speed with power on was the same as that for tail 1 and althoughthe minimum speed with power off was about 2.5 mph lower that that fortail 1, the maximum attain
26、able angle of attack was less and the regionof partial stall (power off) was not attained. This is explainedby thefact that the stabilizerwas large comparedwith the elevators, and evena 30 elevator deflection did not stall the airplane.In tests with tail 2, the center of gravity was shifted re dto t
27、he resmnost practical location, or until the weight of the pilotstanding on the wing root trailing edge was sufficientto tend to liftthe nose wheel from the undj the precise location of the center ofgravity was 25 percent mean aerodynamic chord, or 1 percent beyond therearmost position approved for
28、this airplane by the Civil AeronauticsAdministration. Even in this condition for which the center of gravitywas more rearward than can be obtained by any normal manner of loadingthe airplane, smooth flight with ample lateral controlwas obtained atminimum speed with the elevator control full back, bo
29、th with power offsmd with power full on.Other flight trials of this configurationwere made with the centerof gravity as far forward as 18 percent mean aerodynamic chord, and nosubstantialloss in the minimmn-speed performance was found.Because of the difference in elevator area for the two tail con-f
30、igurations it is difficult to compare the resuJts directly. However,the principal purpose here is to study the conditionswhereby a minimumdifference in trim, with power on and power off, is attained. Consideringtail 1, at e = -15 the difference (with power on and power off) intrue indicated airspeed
31、 is about 2.2 mph, correspondingto an averageangle of attack (with power on and power off) of 15.7. At the saneaverage angle of attack for tail 2, the change in true indicated airspeedis only 1.5 mph.At e = -19 for tail 1 the difference in true indicated airspeedis about 6.5 mph for an average angle
32、 of attack of 18.50j for tail 2 atthis average angle of attack the difference in true indicated airspeedremained about 1.5 mph. The wide discrepancybetween results for thetwo tails in the latter case was due, of course, to the fact that fortail 1 the wing was psrtly stalled.It might be concluded on
33、the basis of the data presented that tail 2 a71offers substantialadvantages over tail 1 as regards longitudinal trimchsmacteristics. First of all, it is clear that, although the elevator bdeflections for tail 2 sre much greater than those for tail 1, the airplaneProvided by IHSNot for ResaleNo repro
34、duction or networking permitted without license from IHS-,-,-NACATN 3676 was not brought into apartialof these relatively wide chordustall because of the loss in effectivenessshort-span elevators at large deflections. Therefore, even with the most rearward-center-of-gravity_p the malytical methods o
35、f the final reportin this series (ref. 3) are useful in this regard.It is higjil.yimportant to state that adequate lateral control wasavailable for the Ercoupe airplane in all conditions tested and withboth tail configurations. Even in the case of partially stalled power-off flight with tail 1, late
36、ral control was adequate, for the burbledflow was cofiined to the central portion of the wing.CONCLING REMARKSFlight tests were made with several typical light airplanes toinvestigatepossibilities for obtaining reliable lateral control at lowflight speeds. It is noteworthy that for each condition (a
37、mount of power,flap setting, and center-of-gravitylocation) of each airplane tested,satisfactory lateral control was obtained up to a critical sngle ofProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3.2 NACA TN 3676attack that was in each case wtthin
38、 2 of the angle of attack at whichthe airplane stalled. This value, less than 2, csm probably be con-sidered applicable to most airplanes in the light-airplane category.In many cases a maximum elevator deflectionproviding an angle ofattack in steady flight that is 2 below that for the stall will sls
39、obe insufficientto enable the airplane to be spun.,but in some cases asmaller maximum elevator deflectionwould be required to eliminatethepossibility of spinning.The elevator deflectionrequired for maintaining the critical angleof attack for satisfactorylateral control varies so greatly with . ;Mean
40、 aerodynamic chord, ftAspect ratio . . . . . . .Flap . . . . . . . . . . .Aileron type, sq ft . . . .Aileron area (each), deg .Aileron deflection . . . .Stabilizer area, sq ft . .Elevator area, sq ft . . .Elevator deflection, deg .a71a15a15a15a15a15Elevator trim-tab deflection,Finarea, sift. . .Rudd
41、er area, sq ft . . . . .Rudder deflection, deg . . .Type of cocit control . . .*.*. .a71 a15 Tapered,Sq fta71a15a15a15a15a15a15a15a71a71a71 a15a15 a15a15 a15a15 a15a15 a15a15 a15a15 a15a15 a15a15a11a15 a15deg .a71 . .a71 . .99. . .a71a71a71a15a71a15a15a71a15a15a15a71a15a71a15.a71a71a15a71a15a15a15a1
42、5a71a15a71a15a15a15a15a15a15a15a15a15a15a15a15a15a15a15.a71a15a15a71a15a15a15. . . . . . .*, . Fixed. . Six-cylinder, inverted*.*. a71 , 175. .*. . . . . . 2,450a71 . . . . . . . . . . . 86. . . . . . a71 *,* . 2* . .* 11*2. . . . . . . . . . a71 14. .Upy.a71a71a15a71a15m.: “4.$. . 6.3. Nonecontrol.
43、 a71 9.310 down.9.a71.a71a15a15.a71a71.a71a71a15a71a15a15a15a71a15.a71a15a15a15a15a1510.210.223.9. 9.2a71 797. 5.2. 1.7. 4.7. 2.9. 2.9Wheel.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TABLEV.-CRTTICALANGIESOFATTACKFORSATISFACTORY CONTROLAMDCORBJ?
44、SPONDINGAIRSPEEDSI I IPcoConfigukion I Anglesof attack,degI True indicated airspeeds,mphCenterofgravi+y,Flaps# M.A.C.Power acr as - A% am IAt stall. SpeeddifferenceGrosswt.,lbAirplane!lkylorcraft,zerowashout(ref.1)bterstateS-Mon 15.7 17.0 1.3 41.4 40.2 1.2off 15.8 17.0 1.2 42.o 41.2 .81,050 None; No
45、nel,of?a On 15.0 16.0 1.0 37.0 36,0 1.0off 13.0 14.0 1.0 41.5 40.5 1.021 None21 Noneon 15*O 16.0 1.0 36.014.0 15.0 1.035.0 1.0off39.5 39.0 a715NonezNonel?atrchildPT-19 on 16.8 16.8 0 4.8 48.o X.8off 16.1 16.8 .7 56.8 55.3 1.52,250 -l=25 UP25 up2525on 17.4 18.0 .6 43.5 I 42.0off 13.7 14.4 .7 50.5 49.
46、0 ;:;3030 :2,470 on 16.I. 18.0 1.9 52.0 51.0 1.0off 15.3 16.I. .8 59.2 58.7 .5On 16*8 i8.o 1.2 46.5 45.0 L 5off 13.0 14.4 1.4 51.6 51.0 .614.5 1.6.o 1.5 44.8 42.6%:2.2a17.5 17.5 %) a50t40 55 50 %A: None +1.9 -2.7 4.6 -9.5InterstateS-1A 1,080 21 None -9.6 -23.0 13.4 -11.2 -25.0 -23.029 None -5=5 -13.
47、4 7.9 -7.0 -15.0 -10.0FairchildPT-19 2,250 25 up -15.2 -19a713 4.1 -19.3 -23.6 . -23.625 Down -11.4 -15.2 3.8 -12.7 -16.5 -23.630 Up -5.6 -10.2 4.6 -6.7 -11.4 -12.730 Down -3*5 -3*5 o -4.6 .4.6 -12.7Ag-1 2,.700 25 Up -1.0 b-10.5 9=5 -2.5 %.6.5 -6.525 Down +3.5 -1.0 4.5 -1.0 -2.0 C-13aElevatordeflect
48、ions:(-)up, (+)down.bSee footrmtefor tableV.cObtainedby slightextrapolationbecauseactualthree-pointlandingswere not quiteachieved.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-20.uP 3545W *. . . . . . . .-1-Y$P-Figure 1.- Three-view drawing of Interstate S-1A airplane.“.Figure 2.- View of InterstateL-056S-1A airplafie.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 3676 21.,:,9?.Qwf” “”“”1Ir-“”27%?8Figure 3.- Three-view dr
