What happened
On 16 August 2015, an ATR 42-300, registration PK-YRN, was performing a scheduled passenger service from Sentani to Oksibil. The flight, operated by PT Trigana Air Service, departed at 0522 UTC with a total of 54 fatalities recorded among the occupants. During the flight, the second in command served as the pilot flying while the pilot in command monitored the controls.
As the aircraft approached its destination, the crew established contact with the Oksibil Aerodrome Flight Information Services (AFIS) at 0sch55 UTC, reporting their descent near Abmisibil and their intention to fly a left base leg for runway 11. At the time, the weather at the destination featured broken cloud cover with a base of 8,000 feet and visibility between 4 and 5 km, with clouds obscuring the final approach path.
By 0600 UTC, the AFIS officer noted that the aircraft had not reported for its final approach as expected. Subsequent attempts by the AFIS officer to contact the crew were unsuccessful, leading to the notification of the operator in Sentani regarding the loss of communication. The wreckage was later located on a ridge of Tanggo Mountain at an elevation of approximately 8,300 feet, roughly 10 nautical miles from the Oksibil Aerodrome.
Findings
Investigation of the wreckage revealed that the aircraft was destroyed by the force of the impact and a subsequent fire. While the Flight Data Recorder could not be read, the Cockpit Voice Recorder was successfully recovered. Analysis of the audio revealed that no crew briefings or checklist verifications were recorded prior to the crash, and no terrain warnings were heard. Crucially, the investigation determined that the EGPWS was probably not functioning, as no altitude callouts were recorded during the accident flight or the two preceding flights.