HIGHER HARMONIC CONTROL: FLIGHT TESTS OF AN EXPERIMENTAL SYSTEM ON SA 349 RESEARCH GAZELLE

A research program sponsored by the French Government Agencies has been conducted by AEROSPATIALE Helicopters Division; this program was designed for flight tests on SA 349 Gazelle of an experimental system for active control of vibrations through higher harmonic control. The various steps prior to flight experiments are presented: an experimental system have been determined and manufactured, three control algorithms have been developped and tested in simulation; tests on rotor stand allowed checking for correct operation of the system and validating the algorithm logic. Finally the flight test campaign conducted in 1985 led to: validating the concept of reduction of vibrations with a self-adaptive system, throughout the SA 349 flight envelope; demonstrating very large vibrations gains in closed-loop (80 % reduction as an average in cabin, at 250 km/h); quantifying the effects of higher harmonic control on rotor and control system.