Trigana Air Flight 267

Investigation

The Indonesian National Transportation Safety Committee (NTSC or KNKT) opened an investigation to the crash. In line with international regulations, as the aircraft was built in France, its Bureau d'Enquêtes et d'Analyses pour la Sécurité de l'Aviation Civile (BEA) participated, sending three investigators. Aircraft manufacturer ATR also assisted and sent four technical advisers.

The flight manifest released by Trigana was found to be wrong, being for another Trigana flight. As a result, the chairman of Sentani Airport was fired by the Transportation Ministry. Sixteen workers were also investigated by the police because of their involvement. Two of Trigana's staff remained in custody. Ignasius Jonan, Indonesian Minister of Transportation, criticized the airport staff saying the situation was a "big mess" and needed to be cleaned up.

The flight data recorder (FDR) had a history of maintenance problems going back more than a year, and was inoperative at the time of the accident. Instead, investigators rebuilt the predicted flight path of Flight 267 using Google Earth and data from the cockpit voice recorder (CVR) and its spectrum analysis. The analysis of the CVR revealed that at 14:55 local time, the flight crew of Flight 267 stated their intention to make a direct left base. Immediately after that, Flight 267 deviated from the standard approach path.

Flight 267 deviated to the right. The area on the right side of Flight 267 was surrounded by mountainous terrain. Some of the terrain was as high as 8000 ft. In addition, Papua's unpredictable weather would endanger the flight easily. Pilots had reported that fog sometimes "came out of nowhere", which could limit the pilot's visibility. Though good weather conditions were reported in the area, localized fog existed in the mountains. According to the NTSC, based on the CVR analysis, Flight 267 descended while in the clouds, while the mountains were covered in fog. As the aircraft was flying too low to pass through the mountain range, the NTSC concluded that it was plausible that the aircraft's proximity to terrain was not noticed by the flight crew.

The investigation team analyzed the crew's motivation to deviate from the standard approach and observed that, on the crew's previous flight from Sentani to Oksibil earlier the same day, they did exactly the same thing: joining directly on left base.

The NTSC noted that the EGPWS did not sound during the flight's final moments, even though Flight 267 was going to hit the mountain. Investigators discovered that the circuit breaker responsible for the activation of the EGPWS had intentionally been pulled by Flight 267's crew. Trigana Air's management stated that some pilots claimed the warnings sometimes sounded improperly, which led them to believe that the EGPWS had malfunctioned. Thus, the EGPWS was de-activated by pulling the circuit breaker. The management had identified that some pilots including the accident pilot were pulling the EGPWS's circuit breaker.

As per the final report, the investigation concluded that the EGPWS power supply circuit breaker was pulled during the accident flight and the two previous flights, explaining the absence of the altitude call out during the two previous approaches and warning prior to the impact. Further investigation revealed that Trigana Air's published approach chart which it provided the pilot had incorrect information. The approach chart stated that the minimum safe altitude was at 8,000 ft. Flight 267 impacted the mountain at 8300 ft. The NTSC concluded that the approach chart was wrong, ineffective and hard to understand. Aircraft maintenance was also badly performed by the airline.

The final report concluded that the accident resulted from a controlled flight into terrain caused by the crew's decision to deviate from its projected flight path. The absence of EGPWS warnings aggravated the condition.