What happened
At approximately 1925 Pacific daylight time, an Enstrom 280C helicopter, registration C-FKEO, departed Duncan Airport, British Columbia, for a local visual flight rules mission. The aircraft was carrying a pilot and one passenger. Roughly ten minutes into the flight, while the aircraft was approaching the airport from the south over a forested area, the pilot experienced loud popping and banging noises accompanied by erratic flight behavior.
As the aircraft flew at a low altitude, a trail of grey-激black smoke became visible. During the final 300 feet of the flight, the tail rotor assembly detached from the airframe. The helicopter pitched steeply before descending rapidly into a field 0.8 nautical mile south of the airport. The impact triggered an intense post-crash fire that destroyed the aircraft. Both occupants sustained fatal injuries.
The investigation
The investigation focused on the mechanical failure of the engine-driven fuel pump. Technical analysis revealed that a failure in the pump diaphragm allowed fuel to leak both externally into the engine cowl and internally into the intake manifold. This leak likely caused an over-rich fuel mixture and a loss of engine power. The presence of abundant ignition sources in the engine cowl may have also caused an in-flight fire that damaged the magnetos.
Investigators determined that the loss of engine power led to a decay in main rotor RPM. This decay allowed the main rotor blades to strike the tail cone, severing the tail rotor assembly. The loss of the tail rotor caused a significant forward shift in the center of gravity, making the aircraft uncontrollable at such a low altitude.
Furthermore, the investigation found that the aircraft had not been maintained according to Canadian regulations. Specifically, required torque checks on the relief valve retaining screws—mandated by Airworthiness Directives (ADs)—had not been performed. The maintenance records were also found to be inaccurate and did not reflect the true service history of the aircraft.
Findings
- The primary cause of the accident was the failure to perform required maintenance actions to correct known defects in the engine-driven fuel pump.
- The failure of the fuel pump diaphragm led to engine power loss and an in-flight fire.
- A significant decay in main rotor RPM caused the rotor blades to strike the tail cone, resulting in the loss of the tail rotor assembly.
- The combination of engine malfunction, loss of tail rotor, and low altitude prevented the pilot from recovering the aircraft.
- A lack of oversight by Transport Canada regarding the maintenance provider resulted in a missed opportunity to identify non-compliance with regulations.
Safety action
- Transport Canada updated its electronic Airworthiness Directive list to include AD 91-08-07 for applicable Enstrom 280C and Lycoming engine models.
- An audit of the maintenance facility involved was conducted in November 2005, leading to necessary amendments in maintenance procedures and manuals.