Establishing Rotorcraft Component Fatigue Lives using SUMS Data and a Partial Usage Spectrum Approach for the MH-47G Chinook

Lives of fatigue critical components for Army aircraft are typically established based on component strength from ground test, loads for each regime from flight test, and aircraft usage in each regime from engineering and aircrew judgement. This paper documents the first time that an Army platform has had component fatigue lives defined with usage monitored by the Structural Usage Monitoring System (SUMS). SUMS uses aircraft parameters to identify the regime at any given time. The time in recognized regimes is summed up to generate a spectrum of time spent in each regime. The Partial Regime Recognition Spectrum used here identified specific regimes that had a significant effect on part life and concentrated on identifying only those regimes. Time in other 'unrecognized' regimes was prorated based on the legacy spectrum. The SUMS system is validated using scripted flights, as well as by cross checking against a spectrum generated via pilot interviews. Six components were addressed with life changes of -1.5%, +24%, +33%, +44%, +45% and +124%, with an annual return of $1M as well as reduced maintenance burden and increased readiness.