Flight Information
On 13 September 2016, a Boeing 737-300 freighter, registered PK-YSY, operated by PT. Trigana Air Service, was conducting scheduled cargo flight IL 7321 from Sentani Airport, Jayapura, to Wamena Airport, Papua, Indonesia. The aircraft carried 14,913 kg of cargo. The crew consisted of two pilots and a Flight Operation Officer (FOO) acting as loadmaster. The Pilot in Command (PIC) served as Pilot Flying (PF), and the Second in Command (SIC) served as Pilot Monitoring (PM). No system abnormalities were reported or recorded during the flight.
Preparations and Weather
At approximately 2130 UTC, during flight preparation, the pilot received weather information indicating low clouds over Mount Pikei on the right base of runway 15 at Wamena, with cloud base increasing from 200 to 1,000 feet and visibility 3 km. The aircraft departed Sentani at 2145 UTC and cruised at 18,000 feet.
Approach and Landing
After passing point MALIO, the aircraft began its descent. The pilots observed that the weather met Visual Meteorological Conditions (VMC) and identified another Trigana flight ahead. While passing 13,500 feet over PASS VALLEY, Wamena Tower instructed the crew to report over JIWIKA. Upon reaching JIWIKA, the tower informed the flight was third in sequence and directed an orbit over point X, located 8 nautical miles from runway 15. The crew performed two orbits to ensure separation from the preceding aircraft.
At about 7,000 feet (2,000 feet above airport elevation), the pilot could not identify the visual checkpoint of Mount Pikei and attempted to locate a church checkpoint for the right base of runway 15. The pilot believed the aircraft was to the right of the runway centerline. At 6,200 feet (1,000 feet above), the PF reduced the rate of descent and continued the approach. The PM reported that the runway was not in sight and advised a go-around, but the PF expressed confidence in landing safely because the aircraft ahead had landed.
At approximately 5,600 feet (500 feet above) and 2 nautical miles from the runway threshold, the PF sighted the runway and increased the rate of descent. The Enhanced Ground Proximity Warning System (EGPWS) issued a "SINK RATE" aural alert, prompting the PF to reduce the descent rate. The aircraft crossed the threshold, and the pilot felt the aircraft sink. Touchdown occurred about 125 meters from the beginning of runway 15 at 2230 UTC, with the Flight Data Recorder recording a vertical acceleration of 3.25 g.
Post-Impact
Both main landing gear collapsed; the left main landing gear detached and was found on the runway. The engine and lower fuselage contacted the runway surface. The aircraft veered right and stopped approximately 1,890 meters from the beginning of runway 15. The aircraft sustained substantial damage, but no injuries were reported. The two pilots and the loadmaster evacuated via the forward left main cargo door using a rope.
Probable Cause
The official probable cause states: "Refer to the previous aircraft that was landed safely, the pilot confidence that a safe landing could be made and disregarding several conditions required for go around."