1、4 , . I NATIONAL ADVISORY COMMITiEE :-.- _ -2 -. FOR AERONAUTICs . . - L TECHNICAL NOTE No. 1668 NVESTIGATION OF EFFECTS OF GEOMETRX DIHEDML ON LOW-SPEEJ: - STATIC STABILITY AND YAWING CHARACTEXSTICS OF AN UNTAPEREC 45O SWEPTBACK-TG MODEL OF ASPECT RATIO 2.61 IA. ,. +- r;, :;t- By M: J. Queijo and B
2、yron M. Jqquet Langley Aeronautical Laboratory * Langley Field, Va. Washington September 1948 , Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS XNIXAL NOTE NO. 1668 IPNESTIGATION OF EFFECTS OF GEOMETRIC DIH
3、EDRAL ON LOW-SREkD STATIC STABILITYANDYAWINGCHARACTKRISTICS OFANUNTAPERED 45O SWEPTBACK-WING MODEL OF ASPECT RATIO 2.61 By M. J. Queijo and Byron M. Jaquet SUMMARY An investigation was conducted to determine the effects of gecmetric dihedral on the.low-speed static stability and yawing characteristi
4、cs of an untapered 45O sweptback-wing model of aspect ratio 2.61. The results of the tests indicated that an increaee in positive dihedral resulted in an increase in the rolling mo;llsnt due to sideslip end aleo caused the maximum value of rolling moment due to sideslip to occur at increas- ingly hi
5、gher lift coefficients. Increasing positive or negative dihedral caused a decrease in the lift-curve slope and en increase in the variation of lateral force with sideslip. Dihedral had no appreciable effect on the yawing moment due to sideslip. w The rolling moment due to yawing became more positive
6、 with increas- * ingly poaitive dihedral end became less positive with increasingly negative dihedral. The rate of change of rolling moment due to yawing with dihedral angle was nearly independent of lift coefficient. The yawing moment due to yawing was nearly independent of lift coefficient for low
7、 end moderate lift coefficients and showed no definite trends at higher lift coefficients. The lateral force due to yawing became more positive with an increase in positive or negative dihedral and showed little variation with lift coefficient through the low end moderate range of lift coefficiente.
8、 At higher lift coefficients, the lateral force due to yawing became more positive. INTRODUCTION Estimation of the dynamic flight characteristics of airplanes requires ahowledge of the component forces and moments resulting from the orientation of the airplane with respect to the air stream and from
9、 the angular velocity of the airplane about each of its three axea. The forces and moment6 resulting from.the orientation of the airplane usually are expressed ae the static stability derivatives, which are readily determined in conventional wind-tunnel teste. The forces and memento related to the a
10、ngular motions (rotary derivatives) generally have been estimated from theory because of the lack of a convenient experimental technique. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-m. NAcA TN No. 1668 The recent application of the rolling-flow e
11、nd curved-flow prinoi- pie of the Langley stability tunnel has made possible the determination of both the rotary and 5tatFcstability derivative5 with about the same ease = Unpublished data have indicated that although the rotary stability derivative5 of unswept wings ofmoderate or high aspect.ratIo
12、 can be predicted quite accurately from the available theory, the use of sweep - and,perhaps, low aspect ratio - introduces effects which are not readily amenable to theoretical treatment-. For this reason, a systematic research program has been established for the purpose of determining the effect5
13、 of various geometric variable5 on both rotary and static stability characteristics. The present investigation is concerned with the determination of the effect5 of geometric dihedral on the static stabiJ.ity and yawing characteristics of an untapered 45 swept wing of aspect ratLo 2.61. SYMBOIa All
14、forces end moment5 are given with respect to.the stability exe5 with the origin at the quarter-chord point of the mean aerodynamic chord of the wing. The positive direction ofthe forces, moments, angular displacements, and velocities are ahown in figure 1. The symbols and coefficient5 used herein ar
15、e defined as followa: CL CL CY cx c2 cn Cm L Y X L N M lift coefficient (L/qS) lift coefficient based on lift of one panel of rate of change of C2* withdihedralangle SC 2Jar rate of change of C2r with dihedral angle Subscripts: - 1 induced L left-wing pi whereas, increasing the dihedral negatively c
16、auses the maximum value of C+ to occur at increasingly lower lift coefficients. This trend is exactly the opposite to that reported in reference 3* The disagreement is believed to be caused by the differences in taper ratio and in camber of the two models. The model of reference 3 had a taper ratio
17、0.5 and a Rhode St. Genese 33 airfoil section. The rolling-mcment data of figure 7 were cross-plotted in figure 10 to give curves of Czlk as a function of ddhedral angle for several lift coefficients. The curves of figure 10 indicate that the slope of the curve of C2 q fins% dihedral angle 3nerztUy
18、is conetant in the -loo to 10 dihedral-angle range and decreases slightly in the -loo to -20 range l The same trend was indicated in reference 3. The slopes of the Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 - IXACA TN NO. 1668 curves of CZJ, o
19、f figure 10 were measured in the -100 to loo dihedral- angle range snd were plotted against lift coefficient in figure Il. The plot indicates that ac2r i a nearly independent of lift coefficient up to a lift coefficient of about 0.5 and has a value-of about O.OOOll. At higher lift coefficients ?X/ar
20、 increases to 0.00017. The curve of aCr of reference 3 is included in figure ll for c-eon with the results of the present investigaticm. It is seen that the curves of the two investigations are quite different both in magnitude and in mode of variation with lift coefficient. In an attem to explain t
21、hese differences, sn equation based on the methods of refer- ence 4 and extended to include dihedral angle effects was derived. (See appendix.) The equation is ac2* A + 4) cost ar A+4cosh ( ) however, whether negative dihedral is detrimental or beneficial to dynsmic stability depends an the effect o
22、f dihedral angle 011 all the derivatives which affect dynamic stability. Figure 8 also indicates that C2r generally increases with lift coefficient over the low-lift-coefficient range. The rollinginoment data of figure 8 were plotted in figure 10 as curves of Ctr against dihedral for several lift co
23、efficients. The derivative Czr varies approximately linearly with dihedral for a given lift coefficient. The slopes of the curves of figure 10 were measured and plotted in figure l2. as a curve of resulting from aideslip, can be ahown to be b = B sin P, where therefore, from lifting-line theory CL =
24、 therefore, the rate of change of lift on any eection with angle of attack is given approximately by The rolling moment for rectangular wings da Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN No. 1668 or 15 By mans of equations (A8), (Ag), a
25、nd (AlO) and if I is assumed to be small, it can be shown that If F is zero (as in the tests reported herein) and 237 is substituted for ao, then 2, 1 ml sin A -=- r 12 A + 4 COB A (=I . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-16 REJ?ERENCES
26、NACA TN No. 1668 1. Silverstein, Abe, and White, James A.: Wind-Tunnel Interference with Partic- Reference to Off-Center Poeitio of the Wing and to the Dowmash at the Tail. NACA Rep. No. 547, 1935. . 2. Purser, Paul E., and Campbell, John P.: Experimental Verification of a Simplified Vee-Tail Theory
27、 and Analysis of Available Data on Complete Models with Vee !of Geometric Dihedral on the Aerodynamic Characteristics of a 400 Swept-Back Wing of Aspect Ratio 3. NACA TN No. 1169, 1946. 4. Toll, Thomas A., and Queijo, M. J.: Approximate Relations and Charts for Low-Speed Stability Derivatives of Swe
28、pt Wings. NACA TN . No. 1581, 1948. 5. Sternfield, Leonard: Some Considerations of the Lateral Stability of Hi I? = 10. G Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. Provided by IHSNot for ResaleNo reproduction or networking permitted without l
29、icense from IHS-,-,-NACA TN No. 1668 LO .8 .2 0 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. -32 -24 96 -0 0 6 16 .Z+ it? -32 2+ f6 -0 0 a f6 H 32
30、Angie dyaw, p, deg Angle of yaw, f, dug wt=-1a0 * (dl I- -mO fgwc I- ccncluukd. . , c3 .- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-0 0 Q 0 0 0 0 0 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-
31、,-I 0 0 u 0 0 0 0 0 . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-26 NRCA lyv .004 0 .Lw 47 VO .a% .O# . I i ii 0 -10 -20 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-HACA TN No. 1668 27 . 0 72
32、 . . . r . fiqure 8.- Effect of dIhedra/ -&q/e on fhe vurm?on of C& , Cj+ , and CU, wB7 lift coefficient for CT 45O s wep fback wnq of uspecf rat/o 2.6/. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.OU# Cl 1002 0 00 : *: A :5 v .7 a.9 Provided by
33、 IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-* Jest &to - Equutk (3) -cl- 7iif Gwu - -Reference 2 3 fir Meoii culgkzi beken k3” und -kl” - - -fqution (21 I ! 1 I-! !-Lti - - I 0 .6 .8 10 . . I I hI I I I Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
