REG NACA-TN-3848-1956 A study of several factors affecting the stability contributed by a horizontal tail at various vertical positions on a sweptback-wing airplane model.pdf

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1、1FOR AERONAUTICS .TECHNICAL NOTE 3848A STUDY OF SEVERAL FACTORS AFFECTING THESTABILITY CONTRIBUTED BY A HORIZONTALTAIL AT VARIOUS VERTICAL POSITIONS ONA SWEPTBACK-WING AIRPIJUXE MODELBy Gerald V. Foster and Roland F. GrinerLangley Aeronautical LaboratoryLangley Field, Va.WaAhgtonNovember 1956j, ;M -

2、 J-= .“Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.TECHLIBRARYKAFB,NM-K.NATIONAL ADVISORY COMMDTEE FOR AERONAUTICS IllllllllllllllllllllllllillA STUDY OFSTABILITY00 Lb73b -TECHNICAL NOTE 3848SEVERKL FACTORS AFFECTING THECONTRIBUTEDBY A HORIZONTA

3、LTAIL AT VARIOUS VERTICAL POSITIONS ONA SWEFTBACK-WING AIWLANE MODEL1By Gersld V. Foster snd Roland F. GrinerA study was made in the Iangley lfoot pressure tunnel todetermine the effects of fuselage sfterbodyshape, split flaps, endvariations in the span of the lea-dge flaps on the stabilicontributed

4、by the horiza moreover,the tail, in some cases, actueJly caused the pitching-momentvariationof the win?uselage combinations,which were stable through maxhmmlift, to become unstable in the high-lift range. W a few instances(references2 and5) it has been shown that, when the vertical heightof the hori

5、zontal tail was increased from a moderate height toapproximately 0.5 of the wing semispan above the extended winhordplane, the stabili of the complete model was improved.W those cases where a decrease in the stability contributed bythe horizontal tail occurred for tail positians above the extendedwi

6、ng+hord plane, the decrease has been attributed to the effects ofunfavorable wake-induced downwash resulting from sepmted flow onthe portion of the wing ahead of the tail. It has also been consideredthat the fuselage afterbody shape q produce an adverse effect on theeffectiveness of the horizontal t

7、all.IQ order to furnish additional information on the contributionof the tail to longitudinal stabili” (/) ctdbtaverage e, obtafned from fozmmlaProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 3848 5k Subscripts:w*t horizontal taile effectivei

8、s isolated tailMODEG AND KPPARKKEThe model was a midwing airplane configuration having theleading edge of the wing and tail swept back 42. The wing had anaspect ratio of 4, taper ratio of 0.625, mid NACA 641-3X airfoilsections normal to the 0.273 chord line. The high-lift and stallbcontrol devices e

9、mployed were split flaps of O.= spsm and twosspenwise leaxdge flaps, extending tnboard 057snd 0.42from 0.97+. The horizontal tail had a plan form sindler to the wing. snd NACA 0012-64 secticms pszal.lelto the pl.eneof symnetry. Themounting sxmngement of the tail allowed the tail to be located atseve

10、ral vertical.positions as measured fhom the extended wing+hordplsne. The shape of the fuselage efterbody was modified by theaddition of a cylindrical cone of smsller contraction ratio than usedin the investigation reported in references 2, 3, -d 4. The generalgeomet of the model is presented in figu

11、re 1.The six-tube surveg rake of the Lengley lfoot pressure tunnel,described in reference 6, was employed to measure local dynamicpressure, sidewash, end downwash sngles.ITsTsThe tests were conducted in the Lsnglw 19-foot pressure tunnelat a dynsmic pressure of approximately 75 pounds per squere foo

12、t withthe tunnel atmosphere compressed to about 33 pounds per square inch,.absolute. For these conditions, the Reynolds nuniberwas 6.8 X 106end the Mach nuniberwas 0.14.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6 NACA TN 3+8Measurements of lift

13、 and pitching moment were made through arange of angle of attack from “ to approximately 20. The air+flowcharacteristics in the region of the horizontal tail were obtained(with the tail removed) at angles of attack of 3.6, 8.5, 13.6,16.8, -19.5. A plane of survey, 1.93% behti the 0.256W, wasselected

14、 as a suitableplane from consideration of the fore and aftmovement through the sngle-of+ttack range of the 0.25Et of the tailin various positions. The maximum deviation of the 0.25Et from thesurvey plane occurred at the high sagles of attack (see fig. 2) andamounted to about 4 percent of the tail le

15、ngth forward and 12 percentof the tail length rearwsrd.KESUIXS ANDThe force and moment data haveDISCUSSIONbeen corrected for model-supporttare aud interferenceeffects. Jet+oun correctionshave beenapplied to the values of angle of attack and tching+mmentcoefficient. A correction for air-streammisalin

16、ement has also beenapplied to the values of angle of attack. The air-stream mrvey datahave been correctedfor jet+ounm effects by an angle change to thedownwash and a dow?m?zmddisplacement of the flow.The lift and pitching-momentdata are presented in nondimensionalcoefficientform (for only one of the

17、 two tail incidence tested) asvexations with angle of attack. The effective downwash angles weredetermined from the tail-on and tail-off pitching-momentdata. Theeffective values of dynamic-pressuxeratio were based on a value of Cmit(O.0158) which was determined from the isolated tail lift-curve slop

18、e(reference2) and the geometry of the model. It should be pointed outthat this method of determining dynamic-pressureratio takes no accountof changes in tail efficiencydue to the presence of the fuselage.The cotiined effect of e amd /q on the stabilizingmomentcontributed by the tail can be shown by

19、consideringthe stabilityparameter T, which is defined as follows:.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 3848 7.where()=%1-+%r .which is equiva2.mt toT1=amzch as the values of t were smell andconstant for W confiations, the variation

20、s ofof attack axe considered independent of stabilizerapproximatelyT with anglesetttig.Wen the sign of T is negative, it indicates ttit the tailis contributing stability.Iffect of Fuselage Afterbody ShapeThe effectcharacteristicsof theof thehorizontal tail on lift end pitchntbwinefuselage ccmibtim u

21、tth 0=575reas tith the short-spsnflaps, the tail was highly stabilizing(T = These effects sre inticated by the pitching-momentvsrlationobtaine fo the complete configurations(figs. 3 and 5(a).Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 384

22、8 9Effect of Split FlapswThe effect of the split flaps in conjunction with 0.42-span* leadindge fkps on the tail stability yarameter (fig. 6) appesrsmost pronounced for the tail positions close to the wing-chord plsneextended. The split flaps appear to produce a flow, at moderatesngles of attack, th

23、at causes a decrease in the stability contributedby the tail located 0.162bw/2 above the extended wyohord plsne,while at high augles of attack the initial degree of stability isregained. The results without split flaps indicate that the taillocated 0.162bw/2 above the extended whor plsne contributes

24、stability through the angle-of+xttack range with only a gradueldecrease at the moderate end high angles of attack. For the casewhere the tail is located -o.061bJ2 belgw the extended winhordplane, the results without split flaps indicate that the tailcontributed a constant emount of stabili through t

25、he englf-ttackrange; the addition of split flaps caused ticreases h stabilitycontributed by the tail for sngles of attack beyond 12.Air.qlow Characteristics at the Taila71E order to provide further insight as to the stabilizing effect. bcontributed by the tail with the wing equipped with 0.575#-13pa

26、nleadindge flaps end split flaps, results of aiflow surveyin the vicinity of the tail are presented in figure 7 ascontours of dynemlc-pressureratio, downwash sngle, and sidewashaugle. A cross plot of downwash angle at several tail spsxrwlsestations with engle of attack is presented in figure 8 for v

27、arioustail arrangements. Average values of e aud / have beendetermined for 0.417 and o.162bJ2 tail heights where survey data werecomplete. Determination of these wlues was based on the assumptionthat the measured values of e ad qt/q were the actusl localconditions effecting the tail. It mEW be seen

28、in table I that theaverage values of e end /q are in fair agreement tith theeffective values for the corresponding tail positions.It my be seen fran contours of however, the stabilizingvariation of downwash angle with sngle of attack at the root appearsto be highly influential on the eve-l effect of

29、 the tail. (Seefig. 4.)At high angles of attack, the decrease in stability contributedby the tail in the high position is shown to result frcm anundesirable variatLon of downwash with angle of attack on the outerpti of the tail. This adverse downwash is the result of thecombined effects of the spauw

30、ise distribution of load and wake-Induced downwash.It is of interest to note that the adverse effect whfch occurswith the tail Just above the fuselage might possibly be eliminated byincorporatingnegative dihedral in the tail. The variatim ofdownwash with angle of attack at several spanwise stations

31、of a tailwith approximately 40 dihedral and en equivalent projected span(fig. 8) indicates highly stahillzingvalues of at high snglesa%of attack. A tail with dihedral is affected not only by the downwashcomponent of the flow but also by the sidewash component. Cansideation of the sidewash indicated

32、that the effect was negligible up toaproximately 14 angle of attack, beyond which the positive sidewashin the region of the tip would cause an increase in the angle ofattack of the tail. Iu order to show more clearly the effects ofnegative tail dihedral on the pitch characteristics,the pitchingmomen

33、ts have been calculated from the survey data for the taillocated o.162bJ2 above the extendeddihedral. (See fig. 9.) Comparisoncurves for the tail without dihedralwing-chord plaue with and withoutof the calculated and experimental(figs. 3 and 9) indicates thatProvided by IHSNot for ResaleNo reproduct

34、ion or networking permitted without license from IHS-,-,-NACATN 3848 XLthe accuracy of the calculated curves is sufficient to show theGstability trends. The results of calculations indicate that negativedihedrel eliminates the instability at high angles of attack which was noted for the tail without

35、 dihedral.A comparison of air-flow-survey results presented herein and inreference 6 indicates that the major effects of the fuselage occurredinboerd of station 0.20bv/2. These effects appeered as an upwardshift of the wake center snd an alteration of the downwash pattern.fi general, however, they a

36、ppeer to have only small effects on theinfluence of the tail.It should be pointed out that the tail, at a given position,contributes essentially the EIamevariation in stability for theunflapped=wing ccmfigurations as for the flapped+ing configurations;however, the reason for the decrease in stabilit

37、y contributed by thetail to the unflapped+dng configurations at high angles of atback Issomewhat different than the reason previously discussed for theflappedng configurations. The unflapped wing stalls at the tipend causes em increase in loading on the inboerd sections of the wingand a resultant in

38、crease in downwash.COTKXUDING REMKEKSThe results of a study of several factors affecting thestability contributedby a horizontal tail.to a model airplane with42 sweptbackwing equipped with leading-and trailing-edge flapssre as follows:1. An analysis of the air-flow surveys in the victiity of thehori

39、zontal tail indicates that, at high engles of attack, thevariation of downwash with angle of attack over the outer sectionsof the tail span is such that the tail contribution to the pitchingmoment is stabilizing for the positim below the extended wing-chordplane and destabiliztig for the positions a

40、bove the etiended wing-chordplsne. Tae air-flow surveys indicate that 20 negative dihedral wouldeliminate the destabilizing influence of the tail located at 0.162 wingsemispsn above the extended wing-chord plane by placing the tail in aregion of favorable downwash throughout the angle-of-attack rang

41、e.2. The addition of split flaps decreased the stability contributedby the tail located just above the extended whg-chord plane at moderateangles of attack but increased the stability contributed by the tail ata position just below the extended wi-chord plene for emgles of attackbeyond 12.Provided b

42、y IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-12 NACA3. Reducing the sya of the 0.775-span leaddge flapsto 0.425 improved the stabillty contributedby the tail locatedTN 38480.16semisp taer ratio, 0.625. KU dimensions ere ininches.Provided by IHSNot for Resal

43、eNo reproduction or networking permitted without license from IHS-,-,-TallA 0.575b/2 le-ee flaps d o5bw/2 sPlitflaps; modified afterbody;R= 6.8 x 106; M = 0.14.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-_I.eO401.00,-.-Lo048 /2 /6 200+, d?g-. . _

44、 _ _ _ =. - - /048 12 16 20o+, degTallheiEM($J- 0.102wFigure k.- EPfect of fuselage efterbody dupe on co, (/q.)e, I I I Iv=-%. d=0 4 8 f.? 16 20Cw, degrailMght (d -0.0610.57/2 lead+4ge flaps and eplit 1.apa., .T for severel tall heights;. ,Provided by IHSNot for ResaleNo reproduction or networking p

45、ermitted without license from IHS-,-,-NACA TN 3848/.4L2/.0.8.6CL.4.20-.2.12.08.040-.04Cm -.08:f 2-./6-.20:2419i-4 0 4 8 12 16 20 240.42/2 leading-edge flaps; modified afterbo; , .R= 6.8x106; M=o.14.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-20 N

46、12/.0.8.6,4Ap.20:2-.4 “ I./2.08.047/2:/6,!I . , ,J 5r8 -4 0 4 8 12 f6 20 24U?w,deg“ACATN 3848(b) Split flaps off.Figure 5.- Concluded.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-, rf6-404 8 12 16 20Cw, deg(dTauhelght ,o.m.J- _- - _ e-. .- /048 12

47、 16 20Cw, degHW haM z 0.162- - . _- ._ 3= - - Wltbmt 8PMi146. - mtinpuO 4 8 12 (6 20O+, d8gfor severel tail.M.ghta; 0.42/2 leadLu modfiied titerbody._Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-60 I E.2a +7 - 3.04 50 J3.5III 4D/40 I/ / )4.5 /30/5

48、.0x35.- d20 / ,5.5/00-10-2040 30 20 10 0IL Wte “C6nter20 10 0p, percent semieponOynom R = 6.8 X 106; M = 0.14. . . .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-, * . ?I I I zR Woke smter *Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,