The present paper covers the development of a piezoelectric actuator for trailing edge flap control on a 34 ft diameter helicopter main rotor. The design of an actuator using biaxial stack columns, and its bench, shake, and spin testing are described. Actuator bench testing proves the basic actuator concept, but also points to required performance improvements. Actuator robustness is demonstrated in shake and spin tests simulating the full range of dynamic conditions inside the rotor blade. A series of actuator improvements are implemented, resulting in almost doubled performance. Projections using the latest stack technology show that the improved actuator will meet the performance requirements. The next steps in this program are development of the actuator and full scale rotor system for whirl tower testing and flight testing on the MD Explorer.

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Rotor actuation in the rotating system promises a quantum jump in overall rotor craft performance. Smart material actuator technology for operation `on the blade' is now becoming available and has the potential to overcome the size, weight, and complexity issues of hydraulic and electric on-rotor actuation. The present paper is based on the results of a feasibility study to investigate the use of smart materials for primary and active control on the AH-64 helicopter. Based on the results of the study, it is seen that imbedded actuator concepts, i.e. pitch, twist, and camber control, are not practical at this time. Servoflap control, using hinged control surfaces driven by discrete actuators emerges as the most suitable candidate for smart material actuation. Preliminary data show that rotor control using smart materials might be feasible if a combination of smart materials is used and the rotor design is driven towards low control loads and motions.

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