1、I I , , -. . I RESEARCH MEMORANDUM -NIND-TUNNEL UWESTIGATION AT LOW SPEEDS OF THE PITCHING DERIVATIVES OF UNTAPERED SWEPT -mGS Robert MacLachlan and Lewis R. Fisher Langley Aeronautical Laboratory Langley Field, Va. .- r e NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS WASHINGTON September 29 , 1948 Pr
2、ovided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NATTONAL ADVISORY CO“lTTE3 FOR AEXlNAUTICS By Robert MacLEtchlan asd Lewis R. Fisher A wind-tunnel investigation was conduct aepect ratio and angle of sweep on the longitudinal rotary stability characteri
3、stics of a series of ten untapered wings. me had sweep angles of oO, 45O, and 60 for each of three aspect ratios (1.34, 2.61, and 5.16) and a sweep angle of -45O for aspect ratio 2.61. The iIWeStition showed the effects of aspect ratio and sweep to be greatly interdependent. In every case the effect
4、 of varying angle of sweep increased aa the aspect ratio Increased. The damping-in-pitch parameter generally becams more negative with Increasing aspect ratio or esgle of sweep, except at the lowest sweep angles. With increasing angle of sweep, the positive value of the lift due to pitching decrease
5、d slightly at the high aspect ratio. The effect of increaslng aspect ratio on the lift due to pitching was either negligible or d. The maximum Aamping-in-pitch value at zero lift ma obtained for y, degreea angle of sweep, positive for sweepback, degreea slope of section lift curve, per degree (calcu
6、lations basad on a. = 5.67 in this paper) pitching angular valocity, radians per aecmd pitching-valocity parameter, ralibb effect on (fig. 8); at the higher aspct ratios, however, fncreaelng the sweep of a wing resulted in an increase in the ming in pitch - a result similar to that attained by incre
7、aeing the tail len of an airplane. For the 60 sweptback wing with aspect ratio of 5.16, the value of % at zero lift, which was the maxhmm value obtained, amounted to about half the due that would be axpected for a cmventiod ai“ (reference 1). . It may be noted that, according to the theory of refere
8、nce 7, if x/c is a constant (an assumption on which the theoretfcal values contained herein were baaed) the effect of sweep on % is the same regardless of the direction of sweep. The pitching-mmnt results for the sweptforwclrd wing, homver, were different from those for the ewaptback wing. (See fig.
9、 4.) w$r most of the lift range, the slope for the sweptback wing was positive xhile the C“cL for the eweptforward WFng was negative. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 NACA RM No. L&lg The valm of x/c then must have been negative for
10、the sweptback wing and positive for the Bweptforward wing. This difference in X/C, aa can be seen fram its application in the equation, may account for at least a part of the difference in the experinmental values of C, for the P . meptback and sweptforward xings having the same geometric properties
11、 4 Lift Due to Pitching Velocity me sampls variationa of cL with qc/m, presented in ffgure 5, are of low magnitude and appear to be somewhat erratic. It would be expected then that gt comgrtrison between the experimntal values of lift due to pitching CL shown in figure 10 and values calculated by u
12、se of the following equation (reference 7) Q woad not be very concluaive. Such a comgarison (f igs. 11 and 12) shows, however, that at zero lift, the experimental and calculated values of are in qualitative agreement, and that because of the low magnitude of the values, the theory probably is suffic
13、iently reliable for calculations. cL P The variation of CL with increase of aspect ratio was negligible 9 on the basis of the present investigation. (See fig. U.) The effect of sweep upon was negligible at the low aspect ratio but became larger at the higher aspect ratios at which. a slight decrease
14、 in with hcrease in sweep was noted. (see fig. 12.) cLP cLa The results of low-speed teat8 made in pitching flow in the Langley stability tunnel to determine the effect of independently varying angle of aweep and aspect ratio upon longitudinal rotary derivatives of untapered wings indicate the follo
15、wing conclusions: 1. In general, the trends of the effects of varying aspect ratio and sweep as given by available theory were substantiated in the present investigation. Both experfmsntd and theoretical r03ults indicate that the effects of aspect ratio and sweep on the pitching derivativas are Prov
16、ided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-RACA RM No. -19 9 greatly interdependent. Theoretical valuee of the damping in pitch, although samswhat hLgher in magnitude, were nearly proportional to the experimental values. 2. With the moment reference
17、 polnt at or near the wing asrodynamfc center, the dmplng-in-pitch parameter wa8 practically unaffected by an increase in aspect ratio for unswept wings. As the sweep angle increased, however, 871 increase in aspect ratio caused an increase in the damping in pitch. With canstant aspect ratio, increa
18、sing the angle of sweep generally increased the danrging in pitch. The maximum damping-in-pitch value obtained at zero lift amounted to aboxt half the value that would be expected for a conventianal airplane. 3. The effect on the lift due to pitching of changing aspect ratio or sweep was either negl
19、igible or small. W lift due to pitching decremed slightly with an increase Fn aweep, but the change was noticeable anly at the higher aspect ratios. Langley Aeronautical Laboratory National Advisory Cod ttee for Aeronautics Langley Field, Va. Provided by IHSNot for ResaleNo reproduction or networkin
20、g permitted without license from IHS-,-,-10 NACA RM No. L8Glg 1. Cotter, William E., Jr.: S- and Analysis of Data on Damping in Yaw and Pitch for a Number of Airplane Models. RACA TN No. 1080, 1946. 3. Bird, John D., Jaquet, Byron M., and Cowan, John W.: Effect of Fuse- lage and Tail Surfaces on Low
21、Speed Yam Chaxacterlstics of a Swept-Wing Model a8 Determined in Curved-Flow Test Section of Langley Stability -1. NACA RM No. L&l3 , 1948- 4. Jones, Robert T.: EPfeot8 of Sweepback on Boundary Layer and Separation. NACA TN No. 1402, 1947. 5. Silverstein, Abe, and White, J-s A.: Wind-Tunnel Interfe
22、rence with Particular Reference to Off-Center Positions of the Wing and to the Downwash at the Tail. NACA Rep. No. 547, 1935. 6. Goodman, Alex, and Brewer, Jack D.: Inveetigation a+, Low meed8 of the Effect of Aspect Ratio and Sweep on Static and Yawing Stability Derivative8 of Untapered Wing8. IiAC
23、A TN No. 1669, 1948. 7. Toll, Thorns A., and Queijo, M. J.: Approximate Relations and Charts for hw-Speed Stability Derivatives of Swept Wings. MCA TN No. 1581, 1948. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-5a 1 4 7 2 5 8 3 6 9 -45 0 0 0 45 4
24、5 45 60 &J GO Aspect ratio 2.61 1-34 2.61 5.16 1.34 2.61 5.16 1.34 2.61. 5.16 1,100,000 1,560,000 1,100,000 770,000 1,560,000 1,080,000 760,000 Fltchlng-velocity parameter, - PC .2v Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA RM No. L8Glg Fi
25、gure 1. - Stability-axes system. Positive values of forces, moments, and angles are indicated. 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-,-,-Provided
26、by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 -!, 1 7 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-,
27、0 0 0 0 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 -4 r, -6 -8 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-0 -2 cm 0 C “a -2 -4 0 cm -2 9 -4 -6 Provided by IHSNot for ResaleNo reproducti
28、on or networking permitted without license from IHS-,-,-. k F k 0 8, F Iu 0 . . . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA RM No. I8Glg Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. “ . . . .“ 4 0 4 0 -4 -60 -40 -20 0 20 40 60 Angle d sweep,A, dq Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
