Incident Overview
A flight experienced a loss of the number one engine core cowling shortly after liftoff. The cowling separated from the engine during the initial climb phase. The hinge remained in place on the aircraft after the cowling detached, indicating that the failure occurred at the hinge support structure rather than the hinge itself.
Examination Findings
Metallurgical examination of the separated cowling was conducted to determine the cause of the failure. The analysis focused on the inboard forward cowling hinge support structure, which is a component of an engine hush kit. The examination indicated that this support structure had failed due to fatigue. The fatigue failure allowed the cowling to open and subsequently separate from the engine.
Inspection Requirements
The manufacturer of the cowling, which is part of an engine hush kit, requires that the hinge support structure be inspected for cracks at intervals of each 300 flight hours. This inspection requirement is intended to detect potential fatigue cracking before it leads to structural failure.