What happened
On a scheduled service from Wellington Airport to Rotorua, the aircraft departed at 11:17 local time. After exiting the Wellington Control Zone, the flight provided position updates near Foxton and east of Ohakea. However, communication with the aircraft ceased without any distress signals being broadcast.
At 11:55 local time, the aircraft was observed over the northeast slopes of Mount Ruapehu. Shortly after this sighting, the starboard wing and engine separated from the main fuselage. Following this structural failure, an explosion occurred and the remaining airframe caught fire before impacting the mountainside. The crash took place at 7,300 feet amsl, approximately 1,276 yards from Te Heu Heu Peak. There were six fatalities in total, consisting of the pilot and five passengers.
Findings
The investigation determined that the primary cause was the separation of the starboard wing during flight. It was discovered that the structural integrity of the wing had been compromised by fatigue cracking and fractures in the spar cap resulting from a previous event, which was unknown to the crew.
Further analysis indicated that the pilot's decision to operate near the mountain summit contributed to the accident. The aircraft likely encountered severe turbulence or performed a maneuver that caused the starboard propeller to impact the terrain. The subsequent vibrational loads and intense turbulence placed stresses on the already weakened wing structure that it could not endure.