Frequency Effects on Dynamic Stability Derivatives Obtained from Small-Amplitude Oscillatory Testing

Abstract

As a result of a continuing program of work to establish a basic understanding of the aerodynamic phenomena that ine uence agility, stability, and control of future combat aircraft cone gurations, it has become clear that the conventional stability or aerodynamic derivative model for the representation of aerodynamic loads in the aircraft equations of motion is no longer adequate. This paper discusses the limitations of the stability derivative model for modern combat aircraft maneuvers, in particular the problem of motion frequency effects in static and dynamic derivatives derived from small-amplitude oscillatory wind-tunnel tests, and presents an alternative modeling technique based on the concept of an aerodynamic transfer function. Nomenclature A = in-phase component of rolling moment response AR = amplitude ratio ai, bi, ci = constants in generalized transfer functions B = in-quadrature component of rolling moment response b = wingspan, m Cl = rolling moment coefe cient, L/qSb Clb,att = attached e ow component of steady-state derivative Clb,0