Fatigue Life Analysis of Helicopter Components Based on Usage Monitoring

U.S. Army Aviation Technical Test Center (A TTC) test pilots execute the U.S. Army Lead the Fleet (LTF) program and rapidly accumulate usage of individual U.S. Army helicopters to identify safety, reliability, availability, and maintainability (RAM) issues before they occur in the field. LTF consists of one helicopter of each of the following mission design series: UH-60A and UH-60L Black Hawk, CH-47D and CH-47F Chinook, AH-64A Apache, and AH-64D Longbow Apache. Flight-recorded usage data is analyzed to identify the exposure of each fatigue life-limited dynamic component to damaging flight regimes and determine the associated fatigue damage accumulation. The basic parameters used to identify the flight regimes include gross weight, store configuration, airspeed, altitude, roll angle, vertical acceleration, and ground-air-ground cycles. This paper reports the approach implemented to identify helicopter flight regimes and presents findings that relate helicopter usage with component fatigue damage.