A Framework for Flying Qualities Testing of Highly Automated VTOL Aircraft

The aviation industry and regulatory authorities encounter significant challenges in deploying highly automated aircraft. A primary concern is the impracticality of flight testing mission-relevant tasks across a wide range of operating conditions to ensure the safety of automation systems. This challenge is particularly pronounced for vertical takeoff and landing (VTOL) aircraft where assuring acceptable flying qualities is complicated by intricate flight control systems with over-actuated designs, complex aerodynamic effects such as interlacing propulsor wakes, and the operational demands of urban and adverse atmospheric conditions. To address these challenges, this paper outlines a framework for flying qualities testing put forth by the Automated Flying Qualities (AFQ) Committee which aims to establish best practices for flight testing and certifying VTOL aircraft. Key recommendations include: (i) the development of a unified and aircraft-agnostic framework for analyzing highly automated aircraft, grounded in linear systems theory, statistical and simulation-based evaluations, and targeted flight testing; (ii) the formulation of a unified definition of control loops applicable to highly automated flight control systems; and (iii) the introduction of a rating scheme for automated flying qualities, which builds upon the Cooper-Harper Rating system to evaluate an aircraft's performance, pilot workload, and machine compensation capabilities. This paper serves as a description of the challenges facing the testers, both in industry and regulatory authorities, on ensuring these aircraft are safe to operate. The proposed framework is designed to uncover latent flight control pathologies that could lead to catastrophic outcomes in scenarios where a qualified pilot is not actively engaged in the control loop. While these recommendations are particularly tailored for complex VTOL aircraft, they hold relevance for the broader category of highly automated aircraft.