Identification of Aeroelastic Quasi-Steady Effects Through Flex Factor

Abstract

Rigid body modeling for estimation of aerodynamic derivatives from the flight responses of a flexible aircraft does not yield the true stability and control parameters of the aircraft, as the estimated derivatives absorb the aeroelastic effects present in the data. The analytical expressions for computing the rigid body derivatives from the flight-estimated values require knowledge of aircraft modal mass and generalized elastic deflections which is not always available. This paper considers a simplified approach based on quasi-steady representation of aeroelastic effects to identify the rigid body parameters from the flexible aircraft responses. Results show that, by combining data at several flight conditions, system identification method can be applied to separate the rigid body derivatives and the dynamic pressure dependent quasi-steady effects caused by structural deformation.