Effect of downwash on the estimated elevator deflection required for trim of the XS-1 airplane at supersonic speeds /

This report contains the results of an investigation to determine from linearized theory, which has recently become available, the downwash at supersonic speeds at the tail of the XS-1 airplane and the effect of the downwash on the elevator deflection required for trim. The results are presented in the form of curves showing the variation of downwash angle with angle of attack and elevator deflection required for trim plotted against Mach number. The calculations indicate that increasing up-elevator deflection is required with increasing Mach number (unstable variation) in level flight between Mach numbers of 1.1 and 1.6. A slight reduction in up-elevator deflection occurs between Mach numbers of 1.6 and 2.0. The stabilizer angle has a similar variation, that is, unstable up to a Mach number of about 1.6 and then becoming slightly stable up to a Mach number of 2.0. The reduction of downwash with increasing Mach number is not the main cause of the increase in up-elevator deflection. The main reasons for this trend are that the pitching-moment coefficients due to the wing camber, the wing lift, and the lift of the stabilizer are all in a nose-down direction, and as the Mach number increases, these pitching-moment coefficients apparently decrease less rapidly than the elevator effectiveness."November 1, 1948."Includes bibliographical references (p. 6).This report contains the results of an investigation to determine from linearized theory, which has recently become available, the downwash at supersonic speeds at the tail of the XS-1 airplane and the effect of the downwash on the elevator deflection required for trim. The results are presented in the form of curves showing the variation of downwash angle with angle of attack and elevator deflection required for trim plotted against Mach number. The calculations indicate that increasing up-elevator deflection is required with increasing Mach number (unstable variation) in level flight between Mach numbers of 1.1 and 1.6. A slight reduction in up-elevator deflection occurs between Mach numbers of 1.6 and 2.0. The stabilizer angle has a similar variation, that is, unstable up to a Mach number of about 1.6 and then becoming slightly stable up to a Mach number of 2.0. The reduction of downwash with increasing Mach number is not the main cause of the increase in up-elevator deflection. The main reasons for this trend are that the pitching-moment coefficients due to the wing camber, the wing lift, and the lift of the stabilizer are all in a nose-down direction, and as the Mach number increases, these pitching-moment coefficients apparently decrease less rapidly than the elevator effectiveness.Mode of access: Internet