Usage Based Fatigue Damage Calculation for AH-64 Apache Dynamic Components

As part of the Condition Based Maintenance implementation for the rotorcraft fleet, the U.S. Army has laid out a multiphased approach for the development, validation and demonstration of the usage-based fatigue damage calculation for critical life limited components on the rotorcraft. Phase-I effort involves development and validation of a new approach for usage-based fatigue damage calculation, Phase-II involves controlled implementation of that approach in field units and integration to the Standard Army Maintenance Information System (STAMIS) and Phase-III involves implementation in field operation that would lead to the development of a composite aircraft usage spectrum. This approach where the actual regimes flown by the aircraft are used, instead of the design usage spectrum, to calculate the damage accrued is called Structural Usage Monitoring System (SUMS). SUMS would lead to enhanced safety, reduced maintenance burden, increased operational availability, and reduced Operation and Support costs. Boeing Rotorcraft is under contract to the U.S. Army Apache Attack Helicopter (AAH) Project Manager’s Office (PMO) to develop, validate and implement a usage-based fatigue damage calculation for selected life-limited dynamic components on the AH-64 Apache. This paper documents the development and validation results for the Phase-I effort.