What happened
On 9 September 2024, an ATR 42-500, registration PK-YSP, operated by Trigana Air Service, was performing a scheduled passenger flight from Serui to Sentani, Indonesia. The aircraft was carrying 44 passengers and 4 crew members.
During the takeoff roll on Runway 28, the aircraft reached a speed of approximately 100 knots when the flight crew identified an abnormal condition involving the engines. In response, the Pilot in Command initiated an aborted takeoff by retarding the power levers and engaging reverse thrust. During this maneuver, the aircraft veered to the outbound left side of the runway, eventually coming to a halt approximately 1,200 meters from the runway threshold.
Following the stop, the flight attendants initiated an evacuation of the aircraft. While no fire or fuel leaks were observed, the impact caused substantial damage to the aircraft, including broken landing gear, damaged propeller blades on the left engine, and structural damage to the fuselage and instrument panel. The incident resulted in serious injuries to both pilots and minor injuries to 19 other occupants.
The investigation
The KNKT investigation focused on the engine performance and the crew's monitoring of flight parameters. Technical analysis of the engine records revealed that after the initial power advancement, the right engine torque climbed to 116 percent while the left engine torque stayed at 90 percent. Simultaneously, the propeller speed (NP) of the right engine dropped to 72 percent, whereas the left engine remained at 100 percent.
Investigators also examined the takeoff procedure and the crew's response to the engine imbalance. The investigation involved international agencies, including the BEA (France), TSB (Canada), and NTSB (USA), due to the origin of the aircraft and its components.
Findings
- The right engine experienced a significant divergence in torque and propeller speed compared to the left engine.
- The pilots did not detect the engine parameter imbalance until the aircraft had reached a speed of 100 knots.
- The aircraft sustained substantial damage, including a bent left wing tip and a displaced instrument panel.
- The flight crew and passengers were evacuated successfully, aided by local airport rescue personnel.