ESTIMATING LCF DAMAGE RATE IN FIELDED T700 ENGINES

Current practice on the Army’s T700-GE-701C engine, used in the Blackhawk and Apache fleets, is to use a mission spectrum, defined in the engine specification, to determine the load profile for each critical component. Fatigue damage rate for critical components is calculated using this profile. The specification missions, developed over 20 years ago, may not be representative of how the Army currently uses the engine. This study used engine usage data to compare actual engine usage to the engine specification mission spectrum. Data is available from the existing Engine History Recorder (EHR), installed on all T700 engine models, along with in-flight engine parameter data from the Army’s AH-64D Lead the Fleet (LTF) aircraft. The EHR data was analyzed to determine statistics on the Low Cycle Fatigue (LCF) content of AH-64D, UH-60L and MH-60K missions. LCF counts between the specification mission and actual usage were compared. Also, the estimated fatigue damage per hour for a representative component was calculated using the specification mission and compared to the damage being incurred on the LTF aircraft. Results indicate that mission profiles used to estimate fatigue damage on critical components are not representative of current usage.