Piloted Assessment of the Lateral-Directional Handling Qualities of the Flying-V

Abstract

Flying wings are known for their limited lateral-directional stability and handling qualities. This study aims at assessing the lateral-directional handling qualities of a conceptual flying wing aircraft currently in development at TU Delft, the Flying-V. It focuses on two aspects: First assess the lateral-directional handling qualities of the bare-airframe Flying-V, and the compliance to quantitative requirements. Second, improve these handling qualities through a prototype flight control system, and assess its effect on the handling qualities and the requirement compliance. These assessments were performed both analytically and with a pilot-in-the-loop experiment, in order to experimentally validate analytical findings and obtain new pilot-subjective insights. The analytical and experimental assessment both show the lateral-directional handling qualities of the Flying-V to be insufficient for requirement compliance, due to a lack of pitch, roll and yaw control authority in low-speed flight conditions and an insufficiently stable Dutch Roll eigenmode. The prototype flight control system, consisting of an adapted control allocation and a stability augmentation system, showed both analytically as experimentally to improve the control authority, stability, and handling qualities of the Flying-V. While the effect on the lateral-directional stability was sufficient for stability requirement compliance, the control authority was not sufficiently increased for manoeuvrability requirement compliance. Thus, a challenge remains to improve the handling qualities of the Flying-V. An approximation of the control authority required for full requirement compliance in the flight conditions tested showed a control authority increase of over a factor four to be required for future control surface design.