What happened
On 13 September 2016, a Boeing 737-300F, registration PK-YSY, was performing a scheduled cargo flight from Sentani Airport to Wamena Airport in Papua, Indonesia. The aircraft was carrying approximately 14,913 kg of cargo with a crew of two pilots and one flight operation officer.
During the descent, the crew observed weather conditions that initially met visual meteorological criteria. To maintain separation from a preceding aircraft, the crew entered an orbit at a point 8 nautical miles from runway 1 and was third in the landing sequence. As the aircraft descended, visibility deteriorated. At approximately 1,000 feet above airport elevation, the pilot monitoring noted that the runway was no longer visible and advised a go-around. However, the pilot flying continued the approach.
At roughly 500 feet above the airport, the runway became visible, prompting the pilot to increase the rate of descent. This triggered an "SINK RATE" warning from the Enhanced Ground Proximity Warning System (EGPWS). The aircraft touched down approximately 125 meters from the start of runway 15 with a high vertical acceleration of 3.25 g. During the landing roll, the left main landing gear collapsed, causing the aircraft to slide and sustain damage to the nose wheel, lower fuselage, and left engine.
The investigation
The KNKT examined the wreckage, flight data recorder (FDR) parameters, and cockpit voice recorder (CVR) to reconstruct the approach. The investigation analyzed the descent rate, which was found to be 2,300 feet per minute at touchdown—exceeding the limits specified in CASR Part 25.473. Investigators also reviewed the aircraft's maintenance history and the crew's decision-making process regarding the deteriorating weather and the lack of landing clearance.
Findings
- The primary cause of the accident was the pilot's decision to continue the landing despite several indicators that a go-around was necessary, including the loss of visual contact with the runway, the EGPWS sink rate warning, and the failure to achieve a stabilized approach.
- The crew's confidence was bolstered by the fact that the preceding aircraft had landed safely under similar conditions.
- The descent rate at touchdown was significantly higher than regulatory requirements for a stabilized approach.
- The left main landing gear strut failed during the landing roll, leading to the subsequent damage to the aircraft structure and engine.