What happened
On 13 October 2011, an Airlines PNG Bombardier DHC-8-103, registration P2-MCJ, was conducting a flight from Nadzab toward Madang in Papua New Guinea. During the descent, the aircraft experienced a sudden and severe mechanical event involving both engines. Specifically, the aircraft suffered a double propeller overspeed, which significantly disrupted the flight path and aerodynamic stability.
Following the onset of the overspeed, the aircraft entered a high rate of descent and high airspeed. The flight crew engaged in a long radio exchange while attempting to manage the emergency. Despite the crew's efforts, the aircraft could not be maintained in a stable flight profile, eventually impacting the ground approximately 35 km south-south- $ ext{east}$ of Madang. There were 0 fatalities reported in this occurrence.
The investigation
The investigation focused on the mechanical integrity of the engine and propeller systems. Investigators examined the power lever quadrant, the propeller control units, and the engine components. A critical area of study involved the flight idle gate and the triggers that prevent the power levers from moving into the beta range during flight. The investigation also reviewed the flight data recorder (FDR) and cockpit voice recorder (CVR) to reconstruct the sequence of the overspeed and the crew's subsequent response to the emergency.
Findings
- The primary cause of the accident was a mechanical failure involving the power levers moving below the flight idle gate during flight, which allowed the propellers to enter the beta range unexpectedly.
- The aircraft experienced a loss of propeller speed control, leading to the overspeed condition.
- The flight crew's response was impacted by high levels of stress, resulting in a failure to utilize the appropriate emergency procedures from the Quick Reference Handbook (QRH).
- The crew engaged in an extended radio communication period during the emergency, which contributed to the high rate of descent and the inability to stabilize the aircraft before impact.