What happened
During a recent flight, the aircraft experienced an unexpected loss of the number one engine core cowling shortly after liftoff. The separation occurred while the aircraft was in the initial climb phase, presenting a potential hazard to the airframe and surrounding area.
The investigation
A metallurgical examination was conducted on the separated cowling component to determine the root cause of the failure. The analysis indicated that the inboard forward cowling hinge support structure had failed due to fatigue. This structural failure allowed the cowling to open and subsequently separate from the engine assembly. Notably, the hinge mechanism itself remained attached to the aircraft after the cowling detached.
Findings
The investigation identified a critical maintenance requirement related to the component manufacturer's specifications. The cowling is part of an engine hush kit, and the manufacturer mandates that the hinge support structure be inspected for cracks every 300 flight hours. Failure to adhere to this inspection interval likely contributed to the undetected fatigue crack growth leading to the structural failure.