Delwin R. Croom, Jarrett K. Huffman
An investigation was made in the Langley high-speed 7-by-10-foot tunnel to determine the effectiveness of a given deflector arrangement as a gust alleviator on a 0.09-scale model of the Bell X-5 airplane with various wing sweep angles from 20 degrees to 60 degrees at Mach numbers from 0.40 to 0.90 over a maximum angle-of-attack range from approximately -5 degrees to 21 degrees. Deflectors were effectve as gust alleviators (reduction of the lift-curve slope measured through 0 degree angle of attack) at all wing sweep angles; however, the magnitude of lift-curve-slope reduction varied with Mach number and wing sweep angle. For this particular deflector installation (projection of 15 percent average chord and span of 0.25 wing semispan located along the 35-percent-chord line of the unswept wing), the configuration with 50 degree swept wings had the maximum reduction in lift-curve slope and the minimum variation with Mach number (from approximately 29 percent at a Mach number of 0.40 to approximately 21 percent at a Mach number of 0.90). The deflectors caused an increase in drag at all Mach numbers and wing sweep angles of this investigation and, consequently, would be effective as aerodynamic brakes. At the lower angles of attack (linear portion of the lift curve), the longitudinal stability of the wing configurations for angles of sweep from 20 degrees to 50 degrees was increased by the addition of the deflectors. At higher angles of attack as the Mach number was increased, pitch-up was evident for both the basic model and the model with deflectors. The severity of the pitch-up and the angle of attack when the pitch-up occurs are closely associated with the nonlinearity of the lift curve. Over the angle-of-attack range of the present investigation the deflectors caused no marked effect on the longitudinal stability of the 60 degree swept-wing model. It appears that, generally, if the basic model had no pitch-up problem, the deflectors did not cause pitch-up; however, if the basic model had pitch-up, the deflectors tended to increase pitch-up.
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