Vibration Reduction in Rotorcraft Using the Actively Controlled Trailing Edge Flap and Issues Related to Practical Implementation

This paper describes recent research concerning rotorcraft vibration reduction using the actively controlled trailing edge flap (ACF). An aeroelastic model has been developed for a helicopter rotor incorporating a trailing edge flaps using a new two dimensional unsteady aerodynamic model which includes compressibility and unsteady freestream effects. A flexible hingeless blade model is used which includes fully coupled flap-lag-torsional dynamics. Results are presented from vibration control studies performed using the ACF in three configurations: (a) servo flap, (b) plain flap, and (c) dual servo flap utilizing independent actuation. In addition, a ‘free-flap’ failure condition is investigated. Results from a stability analysis indicate that this condition can produce significant changes in blade damping. Last, results from control studies have been used to develop a conceptual design for a mesoscale actuator driven flap based on an actuator currently under development at UCLA.