Piloted simulator evaluation of low speed handling qualities of the Flying-V

Abstract

The Flying-V novel aircraft design aims at reducing fuel consumption by an innovative low-drag, fuselage-free geometry. However, possible issues related to certification requirements have been noted regarding longitudinal handling qualities at low speed, the pull-up manoeuver, and the flight path angle response. This study aims at investigating these issues by means of piloted simulations. With a mathematical model of the Flying-V based on the vortex lattice method, a preliminary off-line analysis of the handling qualities is conducted. A sensitivity analysis is considered over center of gravity position (forward, nominal, aft), approach speed (between 0.225 and 0.3 Mach), maximum deflection of the control surfaces (between 20 and 30 degrees), and flight control system (Direct Law or Pitch Rate Command). The piloted experiments, supported by the preliminary analytical assessment, show that the handling qualities provided by the current design of the Flying-V with Direct Law at 0.3 Mach are satisfactory with minor improvements related to aircraft responsiveness. For lower speeds (0.225 Mach), the handling qualities degrade due to a sluggish response, high compensation workload, insufficient control authority, insufficient sight angle, and tendency to pilot induced oscillations. Shifting the center of gravity away from the nose provides larger control authority at the expense of a minor reduction of responsiveness. Control augmentation proves very effective at improving the handling qualities. It is expected that the go-around certification standards will be satisfied, but approach speed will remain critical for controllability and safety.