Executive summary
On Friday 23 March 2001, at 0705, Hughes 369D helicopter ZK-HMN experienced an engine flameout as the pilot applied collective control normally to arrest the helicopter’s descent. The pilot landed the helicopter in trees on a mountain slope at about 3000 feet, some 12 km northwest of Milford Sound. The pilot and the crew member on board the helicopter were uninjured.
Investigation showed a defective engine fuel control unit was responsible for the flameout. The fuel control unit had been repaired by an Australian component overhaul facility and released to service. After the fitment of the fuel control unit, the maintenance providers did not trace repeated engine overspeeding problems to the fuel control unit.
Because of the involvement of an Australian component overhaul facility, the Australian Transport Safety Bureau was invited to join the investigation. Because of initial concerns of a quality assurance problem with the facility, the Australian Transport Safety Bureau initiated a systemic investigation into its performance. The Bureau will report on the investigation results separately.
A survey of the main New Zealand maintenance organisations, and Civil Aviation Authority records, did not reveal other similar incidents involving fuel control units and power turbine governors.
Other safety issues identified were trouble-shooting procedures by maintenance providers, and the monitoring of service bulletins.
Related Recommendations
Establish a system to ensure proper monitoring and control of service bulletins.
Review Flightline's Rolls-Royce Allison 250-C20B engine trouble-shooting procedures, and ensure comprehensive fault diagnosis is carried out when a repeated component change does not rectify a known problem.