Application Of Fatigue Crack Propagation And Strain Survey Testing To The CH-46 Aft Rotor Drive Shaft

A fatigue cracking problem in the aft rotor drive shaft of the CH-46 helicopter is described. The cracking occurred in a pinned joint between two sections of the shaft, at service times below the retirement life indicated by the original fatigue test and life calculations. Crack propagation and strain survey tests are discussed together with their use in defining periodic inspection intervals and joint improvements. In addition, a new stress analysis technique for joints of this type is introduced.