A helicopter fuel system ''B-nut'' loose by a quarter of a turn has cost Wanaka company Heli Support New Zealand $597,000 plus interest.
The company was sued by helicopter operators D.J. and N.A. Shanks at the High Court in Invercargill, claiming the cost of repairs to their helicopter from a crash in Fiordland in 2013.
Judge Susan Thomas has ordered the company to pay Shanks $US390,643.91 ($NZ597,000) plus interest and costs.
In a judgement after a five-day hearing in Invercargill in May, Judge Thomas said she was satisfied the ''B-nut'' was not properly torqued and therefore Heli Support had ''breached its duty of care''.
Judge Thomas said that on May 27, 2013, Sean Mullally and Sarah de Reeper were flying a Hughes MD369 (now MD500) series helicopter, from the Heli Support workshop to Mirror Lakes in the Eglinton Valley.
''They flew through a light snow shower lasting about a minute.
''During the descent, when the helicopter was approximately 150 feet above the ground, the engine flamed out and stopped.
''Mr Mullally managed to control the helicopter so that it touched down to land, although it slid along the ground for 10-15m.
''Although Mr Mullally was able to bring the helicopter to a stop, the main rotor blades severed the tail boom.''
Judge Thomas said the question to be addressed was why the engine stopped.
Evidence centred on the ''B-nut'' in the fuel system which was one-quarter turn loose when inspected after the accident.
A test by investigators showed that with the B-nut loosened one quarter turn ''there was an immediate substantial leakage of fuel''.
Heli Support did not accept the B-nut was loose when the Helicopter left Wanaka or that it caused the engine failure, arguing it was ''more likely than not that the accident was caused by snow ingestion''.
Aaron Shaw, then chief engineer at Oceania Aviation, gave evidence he inspected the damaged helicopter and ''one of the first things he noticed was that the fuel line to the filter head was loose''.
Aviation and engineering loss adjuster Peter Webb gave evidence of more than one blue ''torque stripe'' - intended to show any misalignment - on the B-nut, ''one-quarter turn, loose''.
Jason Buick, a Heli Support licensed aircraft maintenance engineer with 30 years' experience, who worked on the helicopter prior to the crash, ''was certain the B-nut was not loose when the helicopter was returned to service on 27 May 2013.''
Retired aircraft engineer Christiaan Minnee gave evidence for Heli Support that ''the number of inspections of the engine bay and fuel system which Mr Buick said he carried out made it highly improbable that he would have missed a loose B-nut.''
Judge Thomas did not find the theory of snow being the cause a ''reasonable possibility''.
