REDUCTION OF HELICOPTER BVI NOISE, VIBRATION, AND POWER CONSUMPTION THROUGH INDIVIDUAL BLADE CONTROL

A full-scale wind tunnel test was conducted to evaluate the potential of helicopter individual blade control (IBC) to improve rotor performance, to reduce blade vortex interaction (BVI) noise, and to alleviate helicopter vibrations. The pitch links of the rotor were replaced by servo-actuators to enable the pitch of each blade to be controlled independently of the other blades. The IBC servo-actuators and control system were designed and manufactured by ZF Luftfahrttechnik, GmbH. This wind tunnel test of a full-scale IBC system was the second of two conducted in the 40- by 80-Foot Wind Tunnel at the NASA Ames Research Center using a BO 105 helicopter rotor. The acquired data set includes data on rotor performance, the static and dynamic hub forces and moments, rotor loads, control system loads, inboard and outboard blade pitch motion, and BVI noise. The data indicated that very significant (85 percent) simultaneous reductions in both BVI noise and hub vibrations could be obtained using multi-harmonic IBC input. The data also showed that performance improvements of up to 7 percent could be obtained using 2/rev input at high-speed forward flight conditions. The IBC test program was an international collaborative effort between NASA, the U.S. Army AFDD, ZF Luftfahrttechnik, Eurocopter Deutschland, and the DLR Institute of Flight Mechanics and was conducted under the auspices of the U.S./German Memorandum of Understanding on Helicopter Aeromechanics.