Application of Automated Rotor Smoothing Using Continuous Vibration Measurements

Traditionally, rotor smoothing has been performed by acquiring vibration phase and amplitude at a few locations in the fixed-frame during dedicated maintenance test flights, in which the flight crew acquires the data at specified ground, hover and forward flight conditions. Although this process is effective, it is time consuming and expensive. A method to reduce or eliminate special maintenance test flights is highly desirable. In this paper, the use of vibration data acquired continuously throughout the flight for rotor smoothing is studied. Vibration data for one AH-64A Apache was acquired both continuously and manually. The vibration characteristics and recommended adjustments for each method are compared. The solution from the continuously collected vibration data was applied to the aircraft. The results demonstrate that this method may be effective at smoothing both main and tail rotors via small adjustments between maintenance flights on aircraft that do not have a regime-based rotor smoothing data acquisition capability.