TWENTYFIFTH EUROPEAN ROTORCRAFT FORUM Paper n G18 STABILIZATION OF A BLADE WITH A SEVERED PITCH LINK USING A TRAILING EDGE FLAP BY

This paper addresses the feasibility of using trailing edge flaps to reconfigure a helicopter rotor blade following a failure of the pitch link, which makes the blade freefloating in pitch and otherwise uncontrollable. A coupled rotor-fuselage model is developed which allowed for rotor anisotropy. A new, optimization-based, trim procedure is developed to determine the dynamics of the failed blade, and the flap inputs required for reconfiguration The trailing edge flap appears capable of correcting the otherwise catastrophic consequences of a pitch link failure. The residual 1/ and 2/rev components of the hub loads appear to be reasonably small. The flap acts by generating a rigid-body pitching motion of the free-floating blade that matches the angles that otherwise would have been generated by the swashplate. The steady-state flapping motion of the reconfigured blade is very nearly identical to those of the undamaged blades. Therefore, if a helicopter rotor is equipped with trailing edge flaps for other purposes such as vibration or noise reduction, these flaps could be used as emergency control surfaces.