A dramatic incident in which 13 people parachuted from a plane before it crashed into Lake Taupō has been blamed on an unnoticed engine fault.
Wreckage from the Skydive Taupō plane that crashed into Lake Taupō in January 2015 Photo: RNZ / Diego Opatowski
The way the plane was evacuated has also been faulted, with the pilot leaving the aircraft before all his passengers had exited.
The incident happened in January 2015, and has now been analysed by the Transport Accident Investigation Commission (TAIC).
Twelve parachutists and their pilot were on their fourth tandem mission of the day when the engine of their Pacific Aerospace 750XL aircraft suddenly failed.
The 13 occupants of the plane jumped out of it and landed safely.
The aircraft crashed into the lake and was destroyed.
In its report, TAIC said the pilot baled out of the plane before everyone else had got out safely.
One tandem pair was still on the plane and, as they got ready to leave, they saw the pilot hit the wing of the plane before bouncing off.
The report said the pilot did not intend to leave before the last of the parachutists, but could not see them because of their dark-coloured jump suits.
"However, by [leaving] he left the aeroplane uncontrolled, and it began to roll and dive shortly afterwards.
"If anyone still on board had had difficulty exiting the aeroplane, their survivability could have been jeopardised by the aeroplane's rapidly changing attitude.
"In this case the proximity to people and property also meant that the unoccupied aeroplane was a threat."
WATCH: RNZ footage from January 2015 showing the wreckage in the lake
The report went on: "By baling out through the cockpit door before everyone else had left the aeroplane, the pilot risked a collision or entanglement with the last tandem pair who exited from the rear door.
"He also risked colliding with the tail [of the] plane because he did not wait until he was clear of the aeroplane to deploy his parachute.
"Either mishap could have led to serious or fatal injuries. If he had exited through the cabin rear door he would have been sure that he was the last to leave and would not have put others at risk."
In its final comments, the commission said the pilot was competent and had the required ratings.
However, it was likely that the company that hired him did not train him adequately in emergency procedures.
This contributed to the pilot's hasty exit from the aeroplane, which had jeopardised others.
Crack in turbine blade was missed
The report also found the engine failure originated from a fatigue crack in a compressor turbine blade.
The turbine section of the engine had been inspected during scheduled maintenance, it said.
While the recommended procedure was to inspect both sides of the blades for any cracks, it was very likely that only one side was inspected.
In addition, the failed blade was an overhauled blade rather than a new one.
It and two others sampled from the set were under-size in some dimensions, compared with new blades, and this might have contributed to stress in the engine.
The commission said it was lucky the parachutists landed on hard ground, not in the lake, because the tandem riders had lifejackets but not the tandem masters, nor the pilot.
It wanted options investigated for the company, Skydive Taupō, to remedy this. The company has since done so.