The skydiving plane which crashed killing nine people in Fox Glacier in September may have been off-balance and overweight when it took off, the Transport Accident Investigation Commission says.
The TAIC released an interim report yesterday on the September 4 crash which devastated residents of the Fox Glacier community. The crash was the worst air disaster in New Zealand during the past 17 years.
The interim report identifies several lines of inquiry which warrant further investigation and will be contained in a full report, estimated to be up to two years away.
Witnesses say the plane's pilot, former Queenstown resident Chaminda Senadhira, tried to manoeuvre out of a dive before the left wing dropped and the plane hit the ground.
Investigators behind the interim report estimate the plane was off-balance and overweight when it crashed.
The report said the plane was nearly vertical when it hit the ground. A fine mist or vapour shrouded the plane on impact, before the aircraft caught fire.
The intense heat and flames stopped rescuers from reaching the plane to help those inside.
Mr Senadhira and the plane's eight skydiving passengers - four of whom were Fox Glacier residents - died when the Fletcher fixed-wing plane crashed at the end of the runway at Fox Glacier Airport at 1.15pm.
TAIC investigators are continuing with several lines of inquiry. These include a possible malfunction or problem with the plane, a lack of passenger restraints, and an examination of the loading and weight limits of the aircraft.
The fitting of the Walter engine to the FU24 type aircraft, the conversion of the plane from crop-dusting to skydiving, and any gaps or deficiencies in skydiving regulations will also be investigated.
The commission estimated the plane to have been 5kg above the maximum certified weight of 2203kg, while its centre of gravity was about three-quarters of a metre rear of where it should have been.
"The flight manual did not have clear information for centre of gravity for loading parachutists through the cabin," the report said.
A recommendation was issued by the TAIC a week after the crash and the Civil Aviation Authority (CAA) subsequently ordered skydive operators to limit the number of people in the main cabin to six.
More than six passengers in a skydiving FU24 plane can disrupt the centre of gravity and lead to control difficulties. Passengers should also be restrained in the front of the cabin, the commission said.
Flight manuals should include more accurate determinations of the centre of gravity for aircraft, the TAIC recommended.
None of the parachutists on board the September 4 flight from Fox Glacier was restrained, the report said. The role of restraints was previously examined by the TAIC and recommendations made, which, in 2003, led the CAA to advise restraints were not required for smaller aircraft carrying fewer than 10 parachutists.
