Development Efforts and Requirements for Implementation of Navy Structural Usage Monitoring

The objective of this paper is to outline key aspects of a structural usage monitoring system that should be addressed to ensure successful system implementation. These guidelines are developed through experience with fielding systems on fixed-wing, rotary-wing, and tiltrotor aircraft within the U.S. Navy. Structural usage monitoring is performed by using regime recognition algorithms in combination with a fatigue methodology tailored specifically for incorporation of regime-based usage information. The parameters necessary to perform the regime recognition function as well as the data rates required are addressed in this paper. In addition, a discussion of the benefits of using aircraft raw data collection with ground based regime recognition versus using on-board regime recognition algorithms is provided. The ultimate goal of structural usage monitoring is to provide individual aircraft monitoring capabilities. As the Navy evolves toward that goal there are also several near-term benefits to be gleaned from a monitor system. A fleet wide update of dynamic component retirement times is one near-term benefit discussed in this paper. Approximately 6000 flight hours of AH-1W fleet data is used to determine the minimum amount of data necessary to obtain a representative fleet usage spectrum which would be used to update retirement times. Also, the benefits of performing structural monitoring concurrently in the design and fleet introduction phase of a tiltrotor aircraft is highlighted in this paper.