Mixed Flight Control Layout for Ultralight General Aviation Aircraft

Kurzfassung

Ultralight aircraft in the 120 kg class (UL-LL in Germany) are characterized by simplicity through strict weight limitation and low administrative effort. Two key factors are appealing but likewise impose safety concerns: UL-LL aircraft neither require an airworthiness certificate nor undergo annual inspections, and pilots are not obliged to pass pilot medical examinations. With the aim to address the accompanying safety issues, a holistic approach is pursued within the MOREALIS project, including pilot and aircraft health monitoring, decision making and automatic emergency landing. On the aircraft side, a backup electric flight control system augments mechanical pilot flight controls in case of aircraft degradation or pilot incapacitation. This means that both decoupled flight control systems access separate control surfaces, and control authority has to be shared between the two systems. This paper presents the design of the mixed flight control layout and analyses the remaining flight and handling qualities for each control system with regard to critical flight maneuvers and failure cases. The results show that especially the pitch authority is critical, and pilot handling qualities for both longitudinal and lateral motion are not satisfactory. These issues can be addressed either with a redesign of control surfaces, or a pilot augmentation approach, where the automated surfaces copy pilot surface commands. Despite the decreased performance, the electric flight controls allow to safely land the aircraft in case of pilot medical emergencies, thereby fulfilling the main requirement.