Gust rejection using active trailing edge flaps

Future rotorcraft are likely to incorporate on-blade actuation for vibration, noise, or performance improvements, in addition to traditional swashplates. This paper investigates the feasibility of using trailing edge flap (TEF) actuation to augment the vehicle flight control system. In order to diminish the effects of atmospheric turbulence and ship airwakes, which contribute to pilot workload, a previously developed methodology is used to design compensators that use TEF actuation to enhance the aircraft control system gust rejection properties. This paper expands the methodology to include practical design constraints on stability margin, actuation requirements, and compensator complexity. The methodology is demonstrated using simulation models of the UH-60 and CH-47 helicopters. Stability, disturbance rejection, and handling qualities metrics are presented. The compensators reduce uncommanded vehicle angular motion with an acceptable effect on stability margins. Trailing edge flap compensators were found to perform as well as swashplate-based compensators, while requiring only four to five degrees of TEF actuator stroke to mitigate moderate turbulence, indicating that TEFs have authority to impact vehicle gust response. It was found that adding blade flapping feedback to the CH-47 compensator design improves the disturbance rejection properties further.