What happened
Following departure from an offshore rig, the pilot failed to perform the required 15-minute radio check. This failure to communicate prompted the initiation of both air and radio searches. Approximately two hours after the missed check, debris was located floating roughly three miles from the point of departure.
The investigation
An examination of the recovered debris indicated that the aircraft had suffered an inflight separation of the vertical fin, which subsequently caused mast bumping.
Metallurgical analysis of the vertical fin attachment fittings determined that the components had separated due to fatigue induced by corrosion and corrosion pitting. The investigation further revealed that during a previous refurbishment of the airframe, the operator had attempted to treat the corrosion, but the effort was unsuccessful. The fatigue fractures identified during the examination appeared to be old, with one fracture containing traces of paint.