Noise Reduction by Blade Root Actuation - Analysis of Flight and Wind Tunnel Tests

As a step towards the application of rotor active control technology in production helicopters, open-loop IBC flight tests with higher harmonic blade root inputs were performed on a BO105 test helicopter equipped with an advanced IBC system having significantly increased control authority. The test setup featured a highly complex data acquisition system for simultaneous measurements of noise emission, vibrations, rotor operational parameters and rotor blade pressures. After a short summary of former HHC and IBC wind tunnel tests, the results of the first flight test data analysis are presented and compared to the wind tunnel observations. The BVI noise test results from all relevant sensors both on the helicopter and on ground will be shown and discussed, including an evaluation of the accompanied effects of the higher harmonic blade pitch inputs on vibrational levels