Aerospatiale AS350 N818MC accident near Montgomery, Texas

Probable cause

Maintenance personnel's failure to properly re-install and secure a fuel line, which resulted in a total loss of engine power.

NTSB analysis

While conducting controlled fire operations, the helicopter was maneuvering over trees, when the engine lost power. The pilot performed an autorotation and the helicopter impacted trees and then terrain, and came to rest on its side. The fuselage and empennage sustained substantial damage. One crewmember was fatally injured.

Examination revealed that a fuel line between the engine firewall and hydro-mechanical unit (HMU) was loose and not secured with safety wire as required. About 25 flight hours before the accident, that fuel line was disconnected to defuel of the helicopter in order to perform a weight and balance check. No other maintenance was performed in that area. The mechanic who returned the helicopter to service stated that he was confident that he torqued and secured the line. No other anomalies were detected with the helicopter which would have precluded normal flight.

The circumstances of the accident are consistent with a loss of engine power due to the loose fuel line.

Text from the NTSB. Open the NTSB docket for CEN19FA109 for the full record.