Accident Narrative
On March 27, 2019, at approximately 1410 central daylight time, an Airbus AS350B3 helicopter (registration N818MC) was substantially damaged in a crash near Montgomery, Texas. The helicopter was operated as a public flight by the United States Forest Service (USFS) crew, who were conducting plastic sphere dispenser (PSD) applications in support of a controlled fire operation in Sam Houston National Forest. After completing the application, the helicopter began flying back to the staging area when the engine experienced a total loss of power. The helicopter descended into trees and impacted terrain, coming to rest on its right side. The pilot and one crew member were able to exit the helicopter; the second crew member was partially ejected and sustained fatal injuries. The pilot suffered serious injuries, and the other crew member had minor injuries.
Wreckage and Impact
The accident site was located in a wooded area of Sam Houston National Forest at an elevation of 328 feet mean sea level, with the helicopter resting on a magnetic heading of 108°. All major components were present at the scene. Trees surrounding the site were about 70 feet tall and showed damage consistent with a descent vector of about 40–50°. No post-impact fire occurred.
Maintenance History
The fuel line between the firewall and the hydro-mechanical unit (HMU) was found loose, and the required safety wire was not installed. All other connections were secure. Examination of the airframe and engine revealed no additional discrepancies.
According to interviews with Mountain Air’s Director of Maintenance, on February 14, 2019, the USFS requested a weight and balance validation for the helicopter. The helicopter was defueled, requiring disconnection of the main fuel line. After verification, the main fuel line was reconnected. The director asked another mechanic to verify the reconnection, which was reportedly accomplished. The mechanic stated he was confident that he had torqued and secured the line. No other maintenance involving the fuel line occurred after that date. On February 23, 2019, the engine would not light, leading to replacement of the igniters and/or igniter box. The helicopter accumulated about 24.9 flight hours after the February 14 maintenance.
On March 25, 2019, the pilot reported to management that the fuel pressure light had flickered during a flight "a few days before." The pilot activated the fuel boost pump and then turned it off; the light did not reappear. The pilot was instructed to monitor the situation.
Engine Data
The digital engine control unit (DECU) was removed and downloaded under FAA supervision. The last recorded fault was "P3 drift or engine flame out."
Subsequent Fleet Inspection
Following the accident, Mountain Air inspected their other helicopters and found that all fuel lines were properly secured.