The Service Life of Aircraft Structures: An Examination from a Statistical Viewpoint of the Fundamentals upon which Aircraft Stressing is Based

The ultimate aim of the stress calculation of aircraft structures is to reduce the frequency of defects in service to an acceptably low level. If this is to be done without undue structure weight the design loads, the factors of safety and the allowable stresses must be chosen with great care. In principle, there must be some relation between the probability of failure and the design strength. On a new design this function is always unknown and the designer must rely on experience of previous aircraft to guide his judgment. However, the required service life and the expected conditions of service, including temperature effects, vibration, etc., must be foreseen and taken into consideration.