Kaman Aerospace Corp K 1200 N675TH accident near Julian, California

Probable cause

The pilot’s failure to conduct a thru-flight walkaround inspection, which resulted in the engine cowling remaining open and subsequently separating from the helicopter and striking the main rotor blades and vertical stabilizer during departure.

NTSB analysis

The pilot of the helicopter reported that he had landed and was going to reposition to another company landing zone after dropping off his crew chief. The pilot opened the engine cowling to allow the engine to cool before restart. However, the pilot did not perform a thru-flight walkaround inspection and climbed into the cockpit and took off. About 60 seconds after departure, he felt a large thump throughout the airframe and then landed as soon as practicable. Upon shutdown and inspection, he noticed that the engine cowling had departed the helicopter and struck the right two main rotor blades and the vertical stabilizer, which resulted in substantial damage.

The pilot reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation.

In the recommendations section of the National Transportation Safety Board Pilot Aircraft Accident Report, the pilot specified that the company has issued a policy that prohibits opening the engine cowling for the sole purpose of allowing the engine to cool. Additionally, the policy directed a pretakeoff helicopter inspection to be completed by a qualified technician.

Text from the NTSB. Open the NTSB docket for GAA17CA146 for the full record.