Investigation Summary
The flight was a short regional hop in the rugged Papua province. As the aircraft approached Oksibil, the crew opted for a direct left base leg for Runway 11 instead of following the published approach path. This shortcut took them over high terrain in an area where localized fog often obscured peaks. The investigation was hampered by a non-functional Flight Data Recorder (FDR) that had been inoperative for over a year, forcing investigators to rely on Cockpit Voice Recorder (CVR) data and spectrum analysis to reconstruct the flight path. The CVR analysis confirmed the crew's intention to deviate and the total absence of EGPWS alerts. Investigators found that Trigana pilots frequently pulled the EGPWS circuit breaker because the system's database lacked high-resolution terrain data for the region, leading to frequent 'nuisance' warnings that the pilots found distracting. Following the crash, a major administrative scandal emerged when it was discovered that the passenger manifest released by the airline was actually for a different flight, leading to the firing of the Sentani Airport chairman.
Final Conclusions
The NTSC concluded the primary cause was the crew's deviation from visual flight rules (VFR) guidance without maintaining adequate visual reference to the terrain. This was exacerbated by the absence of EGPWS warnings, which would have provided a final opportunity to avoid the mountain. The airline's safety culture was heavily criticized for allowing pilots to disable critical safety systems and for using approach charts with incorrect minimum safe altitude information.
Photographic Evidence (1)
Video Analysis
Trigana Air Service Flight 267: ATR 42 Crash in Papua — Analysis of the 2015 crash into Mount Tangok caused by a shortcut through mountainous terrain and the intentional disabling of the aircraft's EGPWS system.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Captain Hasanuddin
First Officer
First Officer Aryadin Falani
Systems & Failure Modes
EGPWS
Enhanced Ground Proximity Warning System; the circuit breaker was likely pulled by the crew to silence nuisance alarms.
FDR
Flight Data Recorder; the unit was inoperative at the time of the crash due to long-standing maintenance neglect.
AFIS
Aerodrome Flight Information Service; the non-radar advisory service used at Oksibil Airport.
Interesting Facts
- 01The aircraft was carrying 6.5 billion rupiah (approx. $470,000 USD) in cash intended for social assistance programs.
- 02The Flight Data Recorder (FDR) was found to be inoperative and had a history of maintenance issues for over a year.
- 03The crash site was located at an elevation of approximately 8,300 feet on Tanggo Mountain.
- 04The approach charts provided to the pilots contained incorrect minimum safe altitude data.
- 05The airline had a history of 14 accidents between 1992 and 2016, including 11 hull losses.
- 06The aircraft was manufactured in 1988 and had been operated by Trigana Air since 2005.
Safety Actions & Advisories
EGPWS Database Updates
Recommendations were made to ensure terrain databases for regional aircraft include high-resolution data for the Papua region to prevent nuisance alarms.
Maintenance Oversight
The Indonesian Ministry of Transportation increased oversight of Trigana Air's maintenance practices following the discovery of the long-term inoperative FDR.
Known Controversies & Unanswered Questions
Manifest Discrepancy and Administrative Fallout
Reference ↗Following the accident, it was discovered that the passenger manifest released by Trigana Air was incorrect, belonging to a different flight. This revelation led the Indonesian Minister of Transportation to describe the situation as a 'big mess,' resulting in the firing of the chairman of Sentani Airport and police investigations into sixteen airport workers.