A framework to enable rotorcraft maintenance free operating periods

Abstract

The British Ultra-Reliable Aircraft Pilot Program of the late 1990s introduced the sustainment concept of a Maintenance Free Operating Period (MFOP) where aircraft become fault tolerant, highly reliable systems that minimizes disruptive failures and maintenance for an extended period of operations. After the MFOP, a single Maintenance Recovery Period (MRP) consolidates repair of accrued faults and inspections to restore an aircraft’s reliability for the next MFOP cycle. The U.S. Department of Defense recently adopted MFOP as a maintenance strategy for the next generation of rotorcraft named Future Vertical Lift. The U.S. military desires the assurance of uninterrupted flight operations that an MFOP strategy provides to enable an expeditionary force. This work develops a framework to balance downtime, dependability, and maintainability of an MFOP rotorcraft. It begins with the hypothesis that metrics using the mean are insufficient in a MFOP strategy and that metrics that include the time history of failure are as important as the rate of failure. It will utilize a Discrete Event Simulation to model the MFOP, MRP, and the success rate as operational metrics. The work will identify which subsystem(s) limit the MFOP of an aircraft and which components drive MRP higher. It will explore a framework to build policies for availability and success rate where preventive component renewals occur at discrete multiples of the MFOP. Finally, it will test the hypothesis that an operator has some control over the MFOP to meet changing operational demands by adapting the MRP through an aggressive lifing policy.