Opposition is mounting against official findings into the cause of a fatal Fox Glacier plane crash two years ago, the inquest into the deaths of nine people has heard.

At yesterday's hearing on the 2010 crash, a safety investigator dismissed the official Transport Accident Investigation Commission findings.

Alan Daley was the Civil Aviation Authority's lead investigator into the Skydive New Zealand crash that killed four tandem skydive masters, four overseas tourists and the Queenstown pilot at the South Westland township's airstrip on September 4, 2010.

He was summonsed to appear at the inquest as an expert witness, rather than on behalf of the authority.

The commission was the main investigator and its report, released in May, blamed the crash on the plane carrying too much weight and being unbalanced.

Modifications to convert aircraft from a topdressing aircraft to a skydiving plane, which pushed its centre of gravity back, caused the nose to tilt up on takeoff, which made it difficult for the pilot to control.

The owners and pilot failed to do required weight and balance calculations, the report said.

Aviation expert Barry Payne told the Coroners Court in Greymouth this week that he did an independent crash report for the coroner and he also blamed weight and balance as key factors.

But Daley said the plane was capable of carrying much heavier weights without a loss of control.

"I believe weight is not a causal factor in this accident," he said.

The inquest earlier heard that the weights of the nine people on the doomed plane were not used in crash investigations.

Daley noted the weights of the dive masters and pilot would be known from aviation medical tests and it would be possible to get some idea of the passengers' weights to allow greater accuracy in determining that as a crash cause.

Claims that balance was a key cause of the crash were "unconvincing", based on information available, he said.

The aircraft had completed 74 tandem flights with eight skydivers without anything untoward occurring.

There had been thousands of similarly loaded flights in the same type of aircraft with no loss of control, he said.

Flight design expert Don McGill, of Aviation Design Solutions, told the inquest he was involved with controlled flight tests over two days last week, which explored possible crash theories.

The flight manual had sufficient information for weight and balance calculations, which he used for the flight tests, he said.

Several other experts have disputed weight and balance problems as causing the crash.

An air accident investigator, Mark Houston, an experienced test pilot, said weight and balance were unlikely to have caused the crash.

He said it was possible to control the aircraft when overweight and with an aft centre of gravity.

He conceded that if skydivers had slid back when the plane took off too steeply, the centre of gravity would go back.

Instead, Houston raised other possible crash causes, including equipment failure.

The inquest started in Greymouth on Monday. It is expected to end today with findings released in a few months.

- © Fairfax NZ News