A missile detached from a Navy fighter jet during a routine landing on an aircraft carrier deck because of a faulty missile launcher detent spring. Visual inspection of Inconel 718 detent spring assembly revealed that four of the nine spring leafs comprising the assembly were plastically deformed while two of the deformed leafs did not meet minimal hardness or tensile requirements. Liquid penetrant testing revealed no cracks or other surface discontinuities on the leaf springs. Material sectioned from the soft spring leafs was heat-treated according to specifications in the laboratory. The resultant increase in mechanical properties of the re-heat-treated material indicated that the original heat treatment was not performed correctly. The failure was attributed to improper heat treatment. Recommendations focused on more stringent quality control of the heat-treat operations.

Failure occurred in a type 304 stainless steel leaf spring attached to the undercarriage assembly of an airport shuttle train. Failure analysis showed that the fracture was caused by low-cycle, reversed bending fatigue. The stresses leading to failure were imposed by poor alignment. It was recommended that improved assembly procedures be used and that, if another failure occurred, a steel of higher fatigue strength be used.