What happened
On the morning of 20 September 2014, a de Havill and Canada DHC-6-300 Twin Otter, registered P2-KSF, was performing a charter flight from Woitape to Jacksons Airport in Port Moresby. While the weather at the departure point was clear, the arrival area was experiencing rain and low cloud cover.
After receiving clearance for a visual approach, the flight crew began a descent. As the aircraft approached the airport, the pilot in command noted that the aircraft was encountering cloud cover and expressed a desire to utilize the Instrument Landing System (ILS). However, the crew did not request a formal ILS approach from air traffic control. During the descent, the aircraft's position was incorrectly assessed, and the crew continued descending through instrument meteorological conditions without verifying their exact location. The aircraft subsequently struck the terrain near the summit of Mt Lawes. The impact was severe, crushing the cockpit and destroying the aircraft. The accident resulted in four fatalities (the two pilots and two passengers) and several injuries, including three serious and two minor injuries among the survivors.
The investigation
The investigation examined the flight path, aircraft systems, and crew performance. Investigators analyzed cockpit voice and video data, which revealed that the crew had lost situational awareness during the descent. The investigation also reviewed the status of the Enhanced Ground Proximity Warning System (EGPWS). It was determined that the crew had left the EGPWS Terrain Inhibitor active, a setting that had been engaged during the previous landing at Woitape. This prevented the system from providing critical terrain alerts during the final moments of the flight.
Findings
- The pilot in command lacked the required instrument currency to legally perform an ILS approach, which likely influenced the decision not to request one.
- The flight crew continued their descent into cloud cover without confirming their geographical position.
- The crew's incorrect assessment of their position led to the controlled flight into terrain.
- The EGPWS was unable to provide terrain caution or warning alerts because the Terrain Inhibit function had not been deactivated following the previous flight leg.