<title>Design and testing of a helicopter trailing edge flap with piezoelectric stack actuators</title>

Abstract

This paper presents the results of research in using piezoelectric stacks to power a trailing edge flap for use as an individual blade control device to suppress vibrations in helicopter rotor blades. A flap actuator was designed and constructed using two piezoelectric stacks arranged in series. Mechanical amplification was provided through a hinged L-arm. An analytical model was formulated to calculate the predicted flap deflection using quasi-steady aerodynamics. The model showed that the high force piezoelectric stacks were capable of maintaining flap deflection over a wide range of freestream velocities. An experimental model consisting of an 8 inch chord NACA 0012 airfoil was constructed incorporating a single 4-inch span, 1.6 inch chord trailing edge flap. The flap performance of the model was tested in no load conditions and in the wind tunnel under freestream velocities of up to 118 ft/sec. The flap deflections were lower for higher velocities and below analytical predictions.