What happened
A Bell 206B helicopter, operated by Helico Air Services Ltd., was engaged in a maintenance flight to address a vertical vibration issue when it entered a nose-down, spiraling descent near Trenton Airport. The aircraft, which was carrying a pilot and an aircraft maintenance engineer (AME), was observed at a low altitude by witnesses before impacting the ground in a wooded area east of the airport. The impact, which occurred in a steep, left-bank attitude, destroyed the aircraft and resulted in two fatalities.
At the time of the accident, the helicopter was configured with fixed floats and was undergoing a procedure known as blade strobing. The investigation noted that the aircraft's weight and center of gravity were within legal limits, and the engine was found to be operating at the time of impact.
The investigation
Investigators examined the wreckage and the aircraft's technical records, which showed the helicopter had been maintained according to all regulations. The engine, transmission, and mast were analyzed; while the mast fractured during the impact, no pre-impact mechanical or structural failures were identified. The engine was found to be functional, though instruments recorded low rotor RPM at the moment of impact.
Regarding the cockpit configuration, the investigation found that the cyclic and collective control sticks had been removed from the left seat for the maintenance task, but the protective covers for the stub shafts had not been installed. Additionally, the dual anti-torque pedals remained in place. The investigation also looked into the pilot's flight history and the AME's maintenance procedures, finding both individuals to be qualified and competent for the flight.
Findings
- The helicopter experienced an uncontrolled descent from a low altitude.
- There was no evidence of any mechanical or structural failure occurring prior to the impact.
- The loss of control was likely the result of unintentional flight control input.
- The presence of the anti-torque pedals and the exposed control stub shafts created a possibility for interference by maintenance equipment or cords.
- A fracture to the pilot's right leg suggested a heavy application of the right anti-torque pedal, which may have been an attempt to recover from a sudden yaw.
- The aircraft's configuration with fixed floats can exacerbate uncontrolled deviations during abrupt maneuvers.