A Parametric Study of On-Blade Control Device Performance for Helicopter Vibration and Noise Reduction

The effects of rotor blade stiffness on the vibration and noise reduction performance of a 20%c plain trailing edge flap and a 1.5%c sliding microflap are studied under heavy BVI conditions in descending fight at μ = 0.15. The adaptive Higher Harmonic Control (HHC) algorithm is used on a hingeless rotor configuration resembling the MBB BO-105. The performance of the on-blade control devices is studied for a range of blade torsional frequencies. The effect of varying spanwise location of on-blade control devices and the chordwise placement of the microflap are studied. A torsional frequency of 3.17/rev is optimal for most configurations. Nevertheless, vibration reduction of 90% is achieved at the highest torsional frequency of 8/rev using a dual plain flap configuration. Noise reduction performance is more sensitive to changes in the torsional frequency. The on-blade control devices are less effective at torsional frequencies above the optimal value.