Design, Implementation, And Flight Testing Of A Stability Augmentation System For Coaxial Ultralight Rotorcraft

Abstract

This paper describes the first ever flight demonstration of a stability augmentation system using electromechanical inline actuators in a rotorcraft with a reversible control train, i.e. without a hydraulic system. A coaxial ultralight helicopter equipped with the stability augmentation system is used as a flight demonstrator. The paper covers the design and architecture of the system, technical challenges, the algorithms including the control laws, safety features, flight testing, and flight test results. The flight test campaign includes scaled down benchmark maneuvers from literature. The flight demonstration proves that the proposed SAS can be integrated safely into small rotorcraft despite the space and weight limits and the actuation force requirements. Measurement data and pilot feedback indicate that the stabilization is effective and workload is reduced. To emphasize the scientific contribution of the flight demonstration, the paper includes a brief discussion of the dynamics of reversible control trains and the associated challenges and open questions.