An analysis of the stick fixed dynamic stability of a typical VTOL aircraft during transition flight out of ground effect

Abstract

An investigation of the dynamic stability of a typical fixed wing VTOL aircraft operating in the transition region of flight was conducted by means of analog simulation. The Ryan Aeronautical Company XV-5A Lift Fan Research Aircraft was used as a basis for the analysis. Wind tunnel tests on a simple 1:24 scale model of the aircraft provided static aerodynamic data throughout the angle-of-attack range -90° < c:>< w +90°. Non-dimensional stability derivative data was extended throughout the angle-of-attack range. Analog simulation at relative velocities of 100, 60, and 20 knots was conducted using dimensional parameters. Recordings of the simulation runs provided period, frequency, damping, and Dutch roll parameter information which was analyzed to determine areas of flight instability. The variations of these parameters with both angle-of-attack and velocity is discussed. The need for automatic stabilization is indicated.