THE USE OF A LOAD SPECTRUM IN PREDICTING AIRFRAME FATIGUE DAMAGE

The use of a load spectrum in airframe fatigue life predictions is con sidered. In-service fatigue lives are predicted using a probabilistic approach that takes into account the main aspects of deterministic met hods. Expressions are derived for damage under fixed flight-hours toge ther with data scatter. The influence of material fatigue properties o n scatter are shown. An algorithm for obtaining simple formulae for ac counting for equivalent airframe fatigue conditions are demonstrated. An example is given for deriving a safe fatigue life distribution func tion.