THE DETERMINATION OF AIRCRAFT STABILITY COEFFICIENTS FROM FLIGHT-TEST DATA PART II LONGITUDINAL INVESTIGATIONS

摘要

The longitudinal stability coefficients in the Z-force and pitching-moment equations were extracted from digitally-simulated aircraft responses by the integral method of Shinbrot, the derivative method, and a new statistical method. The effects on the longitudinal extraction accuracy of response data accuracy, the time increment between data points, the length of the response data, and the variations of parameters in the methods were investigated. The feasibility of the separation of the damping derivatives Cmq and Cm by the use of responses in which the longitudinal and lateral modes had been strongly-coupled and by the use of auxiliary rockets was evaluated. A brief investigation of the effect of atmospheric turbulence on the longitudinal extraction accuracy was performed.nIt was found that all three extraction methods produced roughly the same extraction accuracy though the new statistical method extracted the nonlinear aerodynamic functions in the region of pitch-up better than the derivative and integral methods.