Durability of aircraft structures

Abstract

In this chapter durability is defined as a quantitative measure of an airframe’s resistance to fatigue cracking under specified service conditions. Structural durability is normally concerned with relatively small subcritical crack sizes which affect functional impairment (i.e., fuel leakage, ligament breakage, loss of cabin pressure, etc.), structural maintenance requirements and life-cycle costs. Although these small cracks may not pose an immediate safety problem, it may become uneconomical to repair structural details containing these cracks if these cracks exceed a limiting crack size. Hence, it is very important that aircraft be designed to be durable in order to maximize operational readiness and minimize maintenance and repair costs. Such a set of durability design requirements was developed by the Aeronautical Systems Division of the United States Air Force (1975).