Investigation Summary
The flight was the sixth sector of the day for the crew. While the designated route from Masamba to Makassar followed the shoreline to avoid significant terrain, the Captain (Pilot Flying) decided to fly a direct path to Barru, a route one of the crew members had successfully taken previously. This shortcut led the aircraft directly toward terrain with peaks reaching up to 11,000 feet, while the aircraft was cruising at only 8,000 feet. Satellite imagery and local witness reports confirmed cloud formations in the area, which likely transitioned the flight into Instrument Meteorological Conditions (IMC) for which the crew was not prepared. The Cockpit Voice Recorder (CVR) revealed that the crew did not discuss the environmental risks or the presence of mountains ahead. Furthermore, the EGPWS, which should have provided terrain alerts, remained silent. Investigators found that while a briefing on the EGPWS had been conducted, there was no formal training, and the system's operational test was missing from the pilot's checklist. The wreckage was not located for four days because the Emergency Locator Transmitter (ELT) antenna had detached during the initial impact with trees.
Final Conclusions
The National Transportation Safety Committee (NTSC) concluded that the accident was caused by the crew's deviation from the company's visual route without considering the risks of flying below the height of the surrounding terrain in cloudy conditions. A significant contributing factor was the absence of EGPWS warnings, which prevented the crew from taking necessary avoidance actions. The final report was published on 4 January 2017.
Video Analysis
No video analysis linked for this case file yet.
Crew Experience
Captain
Flying experience recorded as 2,911 hours and 58 minutes.
First Officer
Flying experience recorded as 4,035 hours and 36 minutes.
Systems & Failure Modes
EGPWS / TAWS
The Enhanced Ground Proximity Warning System failed to provide aural alerts. Investigators found no record of functional tests after its installation and noted the system was not included in the pilot's checklist.
ELT
The Emergency Locator Transmitter failed to transmit a signal because its antenna was sheared off during the initial impact with trees.
Interesting Facts
- 01The aircraft was flying at 8,000 feet in an area where terrain reached heights of 9,600 to 11,000 feet.
- 02Tree cuts at the crash site indicated the aircraft was in straight and level flight at the moment of impact.
- 03The ELT antenna detached during impact, preventing search and rescue from receiving a crash signal.
- 04The wreckage was located after search teams narrowed the area using a signal from the flight engineer's cellphone; reports indicated the device was found in Airplane Mode.
- 05The investigation could not determine why the EGPWS failed to provide aural warnings prior to impact.
Safety Actions & Advisories
TAWS Training and Checklists
The NTSC recommended that Aviastar ensure all DHC-6 pilots receive formal training on TAWS/EGPWS and that operational tests for these systems be integrated into standard pilot checklists.