Following a period of general training, a practice autorotational landing was made. A moderately firm touchdown occurred and a repeat of the exercise was requested by the instructor. Touchdown on this occasion was normal, however during the ground slide the right landing gear collapsed. The gear had collapsed from overload forces, but both pilots were adamant that the landings had not been abnormal. Ground marks at the scene confirmed this contention. It was possible that damage had occurred during previous operations, but had not been detected during subsequent pre-flight inspections. The investigation also discovered that the right gear upper struts contained delaminations caused by stress corrosion. The delaminations ran at right angles to the overload forces, and were not considered to have significantly degraded the ability of the struts to support normal loads.
