What happened
On 25 February 2020, a Boeing B737-300 cargo aircraft, registration PK-YSG, was performing a scheduled flight from Sentani International Airport to Wamena, Papua. During the takeoff roll, the flight crew experienced intense vibrations starting at approximately 80 knots, which intensified as the aircraft accelerated.
Upon reaching 110 knots, the pilot in command initiated a rejected takeoff. During the deceleration, the aircraft became difficult to steer and braking performance was insufficient. CCTV footage captured the aircraft skidding longitudinally before veering sharply to the right. The aircraft eventually exited the runway, traveling along the right shoulder and performing a 360-degree turn before coming to a halt approximately 1,600 meters from the start of runway 30. There were no fatalities and no injuries were reported among the two pilots and two passengers on board.
The investigation
The investigation focused on the structural integrity of the landing gear and the damage sustained during the excursion. Investigators identified significant damage to the aircraft's lower fuselage, including broken antennas and scratch marks. The left engine inlet cowl was damaged by a piece of concrete found inside the engine, which also caused damage to several fan blades. Additionally, the right engine inlet cowl showed signs of impact.
Technical examination of the main landing gear revealed that the upper and lower torsion links on both sides had failed. Specifically, the left lower torsion link had fractured, while the right lower torsion and upper torsion links were broken or bent. Furthermore, the shimmy damper assemblies on both the left and right main landing gear were found to be broken, with the manifold separating from the piston housing.
Findings
- The primary cause of the loss of directional control was the failure of the main landing gear torsion links and shimmy damper assemblies.
- Severe vibrations during the takeoff roll were a precursor to the mechanical failure.
- The aircraft's inability to maintain its path during the rejected takeoff led to the runway excursion.
- Runway height variations at the aerodrome may have contributed to increased vertical acceleration and fatigue on the landing gear components.