1、II1INATIONAL ADVISORY COMMITTEEFOR AERONAUTICSTECHNICALNOTENO. 1766WIND-TUNNEL INVESTIGATION OF EFFECTS OF TAIL LENGTH ONLONGITUDINAL AND LATERAL STABILITY CHARACTERISTICSOF A SINGLE -PROPELLER AIRPLANE MODELBy Harold S. JohnsonLangley Aeronautical LaboratoryLangley Field, Va.gjp=WashingtonDecember
2、1948, o0n-THE“., .“” -!“ iProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-“”- TECH LBRARY KAFB, NM “;11111111111“NATIONAL ADVISORY COMMIIXEE FOR AmoJ)JAIL._._._._D_o!+-?.?- -TECHNICAL NOTE NO. 1766WIND-TUNNEL INVESTIGATION OF EFFECTS OF TAIL LENGTH O
3、N TEELOITGITUIKNALAND LATERAL STABILITY CHARACTERISTICSOF A SINGLE-PROPELLERAIRPLANE MODELBy Harold S. JohnsonSUMMARYAn investigationhas been made of a powered model of a single-propeller low-wing airylane with three values of tail length and threehorizontal tails to determine the effects of tail le
4、ngth and tail volumeon the longitudinal and lateral stability.The destabilizing shift in neutral point caused by power increasedwith increasing tail length for either the condition of constanthorizontal-tail volume or constant horizontal-tail area. For a giventail length, the destabilizing shift .in
5、neutral point caused lqJpowerincreased with increasing tail area. Tne increase in directionalstability caued by yower bec degreesyaw, degreesaverage angle of downwash, degreesangle of sidewash, degrees angle of stabilizerwith respect to thrust line.,degreescontrol-surface deflection, degreeseffectiv
6、e tail-off aerodynaroic-centerlocation, percent wingmean aerodynamic chordneutral-point lo:ation, percent wing mean aerodynamic chord( )center-of-gravitylocation for neutral stability when Cm = O a variation in tail length of twice the meanaerodynamic chord was thus obtained. The cross-sectional sha
7、pe of thefuselage stations remained the same for the three tail lengths. Thethree tail lengths tested were 1.85G, 2.576, and 3.85c for the short,normal, and long tail lengths, respectively,measured from 1% to foottunnel. The tests of the isolated small and normal horiz6n that is, the shift in neutra
8、l point becememore destabilizing as the tail Iengti increased. In this case, thedestabilizing effect of tail length also results fra the increase in thepower-on value of de/da with increase in tail length (fig. 27(b)sThe variation of de/da is not quite so great with tail area constantas with tail vo
9、lume constant because, for the latter condition, the tailspan decreased with tail length so that, relatively, the part of thetail imersed in the slipstream increased as the tail length increased.Inspection of equation (1) indicates that the contribution of thetail-effectivenessterm varies directly w
10、th tail volume. Since, witha constant-area tail, the tail volums Increases with tail length, thedestabilizing shift in neutral point would be expected to increase withtail length even if the value of d.6/da did not vary. This effect maybe illustrated by a comyrison of the neutral-point shift, at a g
11、iventail length, for the condition of constant tail volume (fig.23) andconstant tail area (fig. 30)0 For the short tail length, the tail volumeis greater for tie constant-volume condition than for the constant-areacondition and, consequently, the neutral-point shift is greater for theCOnStt-VOl COnd
12、itiOn (at CL = 1.0, crsi cd?iationjIower = -5 percent M.A.C. for constant volume and -3 percent MoAoCO.for constant area). For the long tail length, the tail VOl issmaller for the constant-volume condition than for the constant-areacondition ahd the neutral-point shift is smeller for the fomner cond
13、itionthan for the latter (at CL = 1.0, cruising configuration,% = -12 percent M.A.C. for constant volume and -19 percent M.A.C.powerfor constant area).With flaps deflected, the effect of tail length on the neutrel-point shift is qualitativelysler to that obtained with flaps neutral.As in the case wi
14、th constemt tail volume, however, computation indicatesthat the contribution of the trti term is of considerablemagnitude andthat the relative influence of each component on the total shift variesin an unpredictablemanner with tail length.Effect of flap deflection.-With windmilling proyelJer, deflec
15、tingthe flaps generally caused a forward shift in neutral- oint locationwhich increased with lift coefficient and tail length ffig. 31). Asexpected, and de/da increased because of ila deflection.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.14 NAC
16、A TN NO. 1766,As shown in figures 27(a) and 27(c), the greatest increase in downwashoccurred for the model with the short tail length (6.90 with flapsretracted and 9.8 with flaps i%flected at CL = O.8), end the dcnw.mashdecreased with tail length (5.2 with flaps retracted and 5.3 with flapsdeflected
17、 for the model with the long tail length at CL = 0.8). Thedynamic-pressureratio decreasedbecause of flap deflection, the changebecoming smaller as the tail length was increased. The incrementof w was positive and increasedwith tail length end lift coeffi-dCLcient (Figs.27(a) and 27(c). Although the
18、adverse effects of propellerslipstream decreased with tail length, the moment amn of the horizontaltail apparently accoumts for the increasinglyunfavorable shift in npwith tail length, which increasemore them offsets the rearward shiftin no due to flap deflection (figs.21(a) snd22).With,power on, fl
19、ap deflection caused a small destabilizingshiftin np which decreased as the tail length and lift coefficient wereincreased; the shift due to flap deflectionbeceme stabilizingfor themodel with the long tail length above lift coefficients of about 0.85(fig 31(3). The largeforward shift in np with Incr
20、easing CL forthe model with the long tail length in the cruising configuration(fig 22(a) results in this tabilizing flap-deflection effect. Althoughthe dynemic-mcessureratio increasedbecause of flap deflection, thew,increment increasingwith Zt, the destabilizing decrease in C.J.1which was greatest f
21、or the model with the short tail length, is believedto have caused the forward shift in np (figs.27(b) and 27(d).DownWash increasedbecause of flap deflectionfor the model with theshort tail length but remained unchanged for the model with the normaltail length and decreased for the model with the 10
22、 tfil lengti. Thisdecrease c for the model with the long tail length justifies theneutral-point results. The veriation of downwash with angle of attackwas relatively unaffectedby flap deflection.Elevator-free stability.-Stick-free neutral points deteminedfrom the elevator-free stabilizer tests (figs
23、 E, 15, and 18) arepresented in figure 32. b the cruising configuration,both with wind-milling propeller and with power on, freeing the elevator reduced thestabili of the model for the three tail lengths tested, -theloss instability increasingwith tail leugth (about2.90percent MtA.C. for theshort t
24、ail length and .O percent M.A.C. to 7.5 percent M.A.C. for thelong tail length). The effects of power with free elevator were shtKLa.rto those for the model with elevator fixed. .The stick-freeneutral points for the landing configurationare notpresented because it was found that the tail was operati
25、ng at a large 4angle of attack where the slope of the tail lift curve is nonlinear dueto a stalled or partially stalled condition and hence the data is notgenerally applicable. It is believed that tail stall will not occur atfull-scale Reynolds numbers becaum the unstalled angle-of-attackrangewould
26、he extended.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN NO. 1766 159 Effect of Tail Area withNeutral points.- The effect the neutral point generally moved for-d for the model withthe that is, the neutral-point shift ismost stabilizingfor
27、the large tail end becomes less stabilizing asthe tail aea decreases. The trim term is again the detemrtning factor.The large tail gives the greatest value of de/da, Tower on, which factshould result in the greatest destabilizing shift of the neutral point.The value of d(%/y for the large tail is ve
28、ry low; consequently, thedCLunfavorable shift caused by the trim term is very much lower for thistail than for the other tails.In connection with the variation of de/da, power on, with tailarea for the short tail length, the reason for the much larger valuesfor the large tail thsn for the small tail
29、 is not cleer. Normally,the small tail, which has a luger percentage of area in the slipstream,wuultbe eqected to give the lager values of de/da. Such was thecase for the other tail lengths with flaps deflected and also for alltail lengths with flaps neutral.Effect of flal deflection.:For the three
30、tail lengths tested,increasing the tail area with windmilling propeller resulted in a forwardneutral-point shift caused by flap deflection, the shift increasingasthe tail length was increased and increasing with tail mea as the liftcoefficient was increased (fig. 37). With power on, the effect of ta
31、ilmea on the change in neutral-point location due to deflecting the flapsshowed no consistent variation with tail length. For the model with theshort tail length, the change in np due to flap deflectionbecame lessdestabilizingwith increasing tail erea and was slightly stabilizingfor the model with t
32、he large tail. With the normal tail length, tailarea had no noticeable effect on Aupflap with power on. For the modelwith the long tail length the veriation of %flap with increasingtail mea was destabilizingwith power on.LATERAL STKKCLITY CHARACTERISTICSEffect of Tail Length on Lateral-StabilityPeri
33、metersTail off.- The effect of tail length on the arsmeters cI% 2*J=d Wv of the model with the tail surfaces removed (tail off) is shownin figure 41. Except for the flap-tiflectedpower-on confiatimj theparameters were relatively unaffectedly the vsriation in tail length.The application of power for
34、both cruising snd landing configurationscaused d” ivivjsi “ “ “ “ “ . “ “Shorttiillength. . . . . . . . . . . . . . . . . .Nornmltailleb . . . . . . . . . . . . . . . . . .b8tSi110D5th, .,. . . . . . . . . . .2.423.375.040.2820.393O.*2.k23.375.040.423o.O.8&2.423.375.04o.*0.8171.2232.333.27k.950.0410
35、0s0.068Control-SurfaceIa.taI IElevatamb Rudderirea,behindhimgeltie,qft . . . . . . . . . . . . . o.* O.L3ale.nce8raa,sq ft . . . . . . . . . . . . . . 0.1% 0.102mOt-meEm-Bqt16rech0rd,ft . . . . . . . . . . . . . . . 0.I.S8 o.3ZQ:ontrO1deflectlOn,4eg . . . . . . . . . . . . . . . . 30up 30 rightSQdo
36、un 30left%raight-linecontourbehindhingeline%iormlhorizontaltail T- -.rProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a. , .TABLE IITEST CONDITIONSDynamic Air- Test Turbu- EffectiveModel pressure speed Reynolds lence Reynolds(lb/sqft) (mph) nmiber fa
37、ctor numberComplete, windm.illingpropeller and 16.37 80 1.00 x 106 1.6 1.600”X 106flays up, power onComplete, flaps down,power on 9.21 60 .750 1.6 1.200Isolated small hori-zontal tail 15.(30 76 .382 1.93 .740Isolated normalhorizontal tail 13.00 71 .415 1*93 . .800Isolated large hori-zontal tail 15.0
38、0 76 .548 1.93 1.060(semispan)*Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-26NACA !t!t-1NO. 1766.4(a) Short tail length. ,-.Figure l.- Drawings of the single-proyeller ailane model showi thethree tail lengths tested. No-1 horizontal tail. (Alldim
39、ensions are in inches.)Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN NO. 1766 27-,.702 -? v1.50+ * /j/=3Q27 *.25CV.255 - z=40#o .25ct(h)Normal tail length.Fie l.-Continued.Provided by IHSNot for ResaleNo reproduction or networking permitted
40、 without license from IHS-,-,-NAC!ATN NO. 1766,Y 9L/3I /“ I.50” “ Zp=sw.25C z=4a5/(c) Long tail length.Figure 1.- Concluded.8Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. NACA TN NO. 1766 29#Y/I/N / IaX*. Figure 2.- System of axes and control-sur
41、facehinge moments anddeflections. Positive values of forces, moments, and angles areindicatedby arrows. Positive values of tab hinge moments anddeflections are in the sane directions as the yositive valuesfor the control surfaces to which the tabs are attached.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
