Aviastar Flight 7503

Investigation

As investigators arrived at the crash site, they suspected that the plane bounced twice before it exploded and burned. According to reports, the plane hit a tree on the other side of the mountain, as there were broken tree branches found in the area. The plane caught fire and slammed into the top of the mountain, killing all on board. Investigators also created the chronology of the discovery of the wreckage and explained how the plane crashed with drone footage.

A preliminary investigation report was published 21 January 2016. At 06:37 UTC, the pilots agreed to fly direct to Barru as one had this experience. A few seconds later, the second-in-command suggested to delay the direct flight for a while. There was partial cloud formation. At 06:51 UTC, the pilot-in-command said that he wanted to climb then the CVR recorded the sounds of impact and stopped recording. The aircraft impacted trees and crashed at 7,734 ft.

Investigators retrieved the designated flight route and compared it with the route that the crew of Flight 7503 took. It was revealed that the pilot had deviated from its original route. The predicted route was from point Bua to Siwa and then to Barru, however, after the crew reached point Bua, they decided to fly direct to Barru. The route that the crew took is mountainous with several mountains ahead (terrain heights of between 9,600 and 11,000 feet) while the designated route was near the shoreline with no significant height. The weather data on the crash site also revealed that there were clouds on the "shortcut" route, which would limit their visibility. With mountainous terrain and limited visibility, this would endanger the flight.

Investigators then focused on why the pilots decided to fly the plane direct to point Barru instead to point Siwa. Investigators considered the Situational Awareness and the process of the decision making to fly direct to Barru. It was revealed that one of the crew had done the same thing before, and during the previous flight no incident occurred. This might have caused one of the crew to trust the one that had done it before in the past to cut the route and make a direct flight to Barru. During its flight to point Barru, neither the pilot nor the co-pilot discussed the environmental condition ahead. The absence of discussion in regard to the conditions ahead meant that the pilots had not properly considered the operational implications of flying the direct route, leading to a loss of situational awareness.

The final report was finally published by the NTSC on 4 January 2017, with their findings as follow:

The aircraft had a valid Certificate of Airworthiness prior to the accident and was operated within the weight and balance envelope.

Both pilots had valid licenses and medical certificates.

The accident flight from Masamba (WAFM) to Makassar (WAAA) was the 6th sector for the aircraft and the crew that day. The Captain acted as Pilot Flying and the First Officer acted as Pilot Monitoring.

The satellite image published by BMKG at 07:00 UTC showed that there were cloud formations at the accident area. The local villagers stated that the weather on the accident area was cloudy at the time of the accident.

The aircraft departed Masamba at 06:25 UTC (14:25 LT), conducted under VFR with cruising altitude of 8,000 feet and estimated time of arrival at Makassar of 07.39.

After reaching cruising altitude, at about 22 Nm from Masamba, the flight deviated from the visual route and flew direct to BARRU on a heading of 200° toward the area with high terrain and cloud formation based on the BMKG satellite image

The pilots decision-making process did not show any evidence that they were concerned about the environment conditions ahead which had more risks and required correct flight judgment.

The CVR did not record EGPWS aural caution and warning prior to the impact. The investigation could not determine the reason for the absence of the EGPWS.

The CVR data and cut on the trees indicated that the aircraft was on a straight and level flight and there was no indication of avoidance action by climbing or turning.

The SAR Agency did not receive any crash signal from the aircraft ELT most likely due to the ELT antenna detaching during the impact.

Regarding the operation of the EGPWS for the flight crew, a special briefing was performed however there was no special training.

The operational test of the TAWS system was not included in the pilot checklist.

The investigation could not determine the installation and the last revision of the TAWS terrain database.

The investigation could not find the functional test result document after the installation of the TAWS.

Some of the DHC-6 pilots had not been briefed for the operation of the TAWS and EGPWS.

Contributing factor(s):

Deviation from the company visual route without properly considering the elevated risks of cruising altitude lower than the highest terrain and instrument meteorological condition in addition with the absence of the EGPWS warning resulted in the omission of avoidance actions.