Remaining Useful Life Estimation (RULE) Methodology

Sponsored by: Naval Air Warfare Center, Patuxent River
Team Member: University of Maryland, College Park

AITHER has worked with the Army Aviation and Missile Command (AMCOM) to develop a novel statistical approach to estimating the remaining useful life of helicopter components based on known usage monitoring data. The basic premise of RULE is to determine conservative predictions for the component loads and fatigue life values from Monte Carlo simulations based on a desired component reliability. Then, as the aircraft usage is monitored, the component life can be calculated with a known reliability based on the extreme predictions generated by the Monte Carlo simulation. The RULE methodology, which was previously tested on small-scale analytical problems, is ideally suited to be integrated into both rotorcraft and fixed-wing aircraft.

During this program, the RULE algorithm underwent further analytical testing on more realistic scenarios and experimental validation. The expanded analytical testing included realistic statistical distributions, increased reliability thresholds, and larger, flight-data generated helicopter usage models. In all cases, the RULE algorithm was successfully able to predict the remaining useful life for the flight critical component with a built-in confidence of the prediction.

Experimental validation and failure testing of fatigue-limited components that also require a known (or assumed) usage profile are extremely difficult. For this effort, AITHER used a high-cycle fatigue testing machine and standard bending test specimens to simulate the fatigue limited components. Although the testing was of a limited scope, which prevented the research team from fully validating the methodology to the high confidences required in rotorcraft components, the experimental results did indicate the capability of the RULE methodology to predict the remaining life of the component with a known confidence.