What happened
On March 27, 2019, an Airbus AS350B3 helicopter, registration N818MC, was performing plastic sphere dispenser applications to support a controlled fire operation in the Sam Houston National Forest near Montgomery, Texas. While the crew was returning to the staging area, the engine suffered a total loss of power.
The pilot attempted an autorotation, but the aircraft descended into trees and impacted the terrain, coming to rest on its right side. The accident resulted in 1 fatal injury and 2 serious injuries. The pilot and one crew member were able to exit the aircraft, but a second crew member was partially ejected and sustained fatal injuries.
The investigation
Investigators found that the fuel line connecting the firewall to the hydro-mechanical unit (HMU) was loose and lacked the required safety wire. This fuel line had been disconnected approximately 25 flight hours earlier, on February 14, 2019, to facilitate a weight and balance check. Although the mechanic who reconnected the line reported confidence that it had been torqued and secured, the line was not properly secured.
Additionally, the pilot had previously reported that a fuel pressure light had flickered during a flight a few days prior to the accident, though the light did not reappear after the pilot cycled the fuel boost pump.
Data downloaded from the digital engine control unit (DECU) recorded a final fault of a "P3 drift or engine flame out."