Evaluation of a Stochastic Approach for Reliability Centered Maintenance Airframes

Abstract

A reliability centered maintenance analysis (RCMA) method for metallic airframes is described, demonstrated and evaluated. This method is useful for evaluating aircraft structural maintenance and supportability requirements and options in terms of risk. It can be used to estimate the average maintenance manhour per flight hour (MMH/FH) and life-cycle-costs. The RCMA method, based on a stochastic crack growth approach, can be implemented using deterministic crack growth analysis (DCGA) results, an estimate of the crack growth life dispersion (e.g., material and service usage), σ z, allowable risk rate, Ra, limit and conditional probability of a class A mishap, Pa. The sensitivity of RCMA inspection predictions (initial and reinspection intervals) to variations in analysis variables is investigated using a cutout in an aluminum-lithium cheek frame. Results are presented in useful formats for evaluating options in terms of risk. For comparable percentage variations in the baseline RCMA variables, the stress level, followed by σ z, affects the RCMA inspection predictions more than either Ra or Pa.