Eurocopter AS355 N448JM accident near Palm Beach, Florida

Probable cause

The pilot’s inadequate preflight inspection, which resulted in the unlatched engine cowling opening and being struck by a main rotor blade during flight. Contributing to the accident was the mechanic’s failure to properly secure the cowling following maintenance.

NTSB analysis

The pilot picked up the helicopter from a repair facility and while flying home heard a “boom,” felt a vibration in the tail, and performed a precautionary landing to a beach. Postaccident examination of the helicopter revealed that the engine cowling had become unlatched and was subsequently struck by a main rotor blade. The detached cowling then struck the horizontal stabilizer and tail rotor, which resulted in substantial damage. The pilot reported that he did not confirm that the engine cowling latch was properly secured during his preflight inspection. He reported that there were no mechanical malfunctions or failures of the helicopter before the cowling opened and detached.

Text from the NTSB. Open the NTSB docket for ERA22LA231 for the full record.