What happened
On 13 April 2016, a Pilatus Britten Norman Turbine Islander (registration P2-SBC) was operating a charter flight for Sunbird Aviation Ltd. The aircraft departed from Tekin in the West Sepik Province, intended for Kiunga in the Western Province, carrying cargo and 12 occupants, including the pilot and 11 passengers. While the pilot's original flight plan involved traveling between Kiunga and Oksapmin, the crew diverted to Tekin without notifying Air Traffic Services.
As the aircraft approached the Kiunga circuit, the pilot cancelled SARWATCH monitoring with Air Traffic Services but did not declare any emergency or safety concerns. Witnesses observed the aircraft performing a sudden, extreme pitch-up maneuver during its final approach, nearly reaching a vertical position. Following this, the right wing dropped and the plane rolled inverted before falling rapidly to the earth. The aircraft struck the terrain approximately 1,200 metres west of the runway 07 threshold with a vertical impact and minimal forward momentum. The crash resulted in 12 fatalities and the total destruction of the aircraft.
Findings
The investigation determined that the primary cause was an improperly balanced load, as the aircraft's center of gravity was positioned significantly behind the allowable aft limit. When the landing flaps were deployed, the resulting pitch-up tendency could not be corrected by the elevator or trim. This maneuver likely led to a tail plane stall and subsequent wing stalls, making recovery impossible at such a low altitude.
Several contributing factors were identified:
- The operator failed to adjust weight limits in the baggage compartment following a recent reweighing of the aircraft, which altered the center of gravity calculations.
- There was no evidence that the pilot had calculated the center of gravity for the flight, despite signing manifests on previous missions claiming compliance with limits.
- High Frequency radio communications were heavily obscured by static and interference, hindering clear contact between the crew and Air Traffic Services.