The Dynamics of Aircraft Degradation and Mechanical Failure

This paper looks at the predictability of system failures of aging aircraft. It presents a stochastic, dynamic model for the trajectory of the operating condition with use. With failure defined as the operating condition below a critical level, the dynamics of the number of failures with accumulated use is developed. The important factors in the prediction of mechanical failures are the number of previous repairs and the time since last repair. Those factors are related to repair procedures, with the time of repair and the extent of repair (fraction of good-as-new) being variables under the control of the operator. The methodology is then applied to data on non-accident mechanical failures affecting safety that result in unscheduled landings. ,