Longitudinal frequency-response and stability characteristics of the Douglas D-558-II airplane as determined from transient response to a Mach number of 0.96

The longitudinal frequency-response characteristics and t h e stab i l i t y derivatives o f the Douglas D-38-11 airplane were computed from transient-flight data.over a Mach number rasge of 0.60 t o 0.96 and at a l t i t u d e ranges of 21,000 t o 25,000 feet, 28,000 t o 33,000 feet, and a t 37,500 and 43,000 feet.The results are presente3 as amplitude r a t i o and phase angle p l o t t e d against frequency, and a5 s t a b i l i t y derivatives p l o t t e d against Mach number.The response amplitrrde of the system varied l i t t l e w i t h Mach number f o r t h e Mach number range of these tests; however, the resonant frequency increased with Mach number, The airplane transfer-function coefficients showed some v a r i a t i o n with Mach number and some a l t i t u d e e f f e c t s .The longitudinal-stability derivatives agreed favorably w i t h windtunnel results.The elevator control effectiveness varied l i t t l e with Mach number a t the lower Mach numbers but a loss in effectiveness was indicated at the higher t e s t Mach numbers.The s t a t i c s t a b f l i t y of the airplane increased with Mach number for t h e Mach number range tested.The rate of change of drplane normal-force coefficient with angle of attack increased with Mach number t o a Mach number of 0.83.The damping derivative increased with Mach number t o a Mach number of about 0.83 and a decrease was indicated t o t h e h i g h e r test Mach numbers. L .NACA RM L52E02c h a r a c t e r i s t i c s of research airplanes through the transonic speed range.I