RMCI had the opportunity to assist the U.S. Army by improving the rotor smoothing process for the CH-47D Chinook. Rotor smoothing is a routine maintenance task that involves a calculated system oof adjustments to an aircraft’s pitch links, blade weights, and trim tabs. These adjustments are designed to reduce vibrations at the fundamental (once-per-revolution) rotor frequency. A reduction in rotor vibration adds a significant amount of “smoothness” to the aircraft while in flight. In addition, a properly smoothed aircraft will also increase the longevity of the aircraft. The procedure for rotor smoothing is typically performed in multiple flight modes including flat pitch ground running at 100% (FPG100), hover, and several pre-defined, steady, level flight air-speeds. The slightest adjustment can change both the dynamic balance as well as the aerodynamic response of each individual blade.

The Aeromechanics Division of the Army’s Aviations Engineering Directorate (AED) is the organization that oversees rotor smoothing of Army rotorcraft. Since the fleet-wide fielding of the Aviation Vibration Analyzer (AVA) in the early 1990s, AED has noted more difficulty in rotor smoothing the Chinook than either the Blackhawk or the Apache. This complication was suspected to be caused by inaccurate sensitivity coefficients associated with the CH-47D adjustments. Through a joint effort with Aeromechanics, RMCI was able to develop and test an improved set of rotor smoothing coefficients for the CH-47D. In doing so, RMCI was able to help reduce the Army’s costs associated with Rotor Track and Balance (RT&B) by reducing man-hours, fuel costs, and wear-and-tear of time-based components. Furthermore, in shortening the time required to perform effective RT&B, RMCI has helped the Army to increase its aircraft availability fleet-wide.