An Investigation of Flight Loads, Counting Methods, and Effects on Estimated Fatigue Life

This paper considers the determination of stresses at one or more critical points in aircraft wing structure. Load-time histories obtained from counter accelerometers are used to set up applied loads sequences for components or for full-scale fatigue tests; the derived stress-time histories may be used in estimating the fatigue life of the wing structure.

Accelerometer design is discussed, and three counting methods used (peak count, variable reset, and level crossing) are compared. Damage calculations are presented, and it is shown that the Miner-Palmgren finite-step integration method of estimating cumulative damage provides less accurate results than the Royal Aeronautical Society stress-endurance data method.