Plane manufacturer warns against modifications

The scene of the fatal accident at the Fox Glacier airfield in South Westland. Photo / Sarah Ivey

The manufacturer of a plane which crashed in the town of Fox Glacier on the West Coast last September, killing nine people, is warning against putting more powerful engines into the planes.

The Transport Accident Investigation Commission (TAIC) in November released an interim report into the crash, which claimed the lives of five New Zealanders and four tourists, which happened when the Fletcher fixed wing plane crashed at the end of the runway at Fox Glacier Airport after taking off for a sky-diving flight.

The September 4 crash was the worst air disaster in New Zealand in 17 years.

TAIC investigators estimated that the plane was off-balance and overweight when it crashed but Hamilton-based Pacific Aerospace Ltd (PAL) told the Nelson Mail it believed rule changes in the late '90s allowing the planes to be repowered, meaning they could fly with nearly 40 per cent more than their designed maximum takeoff weight, could be responsible.

Crashes in modified Fletcher aircraft had claimed 16 lives in New Zealand and overseas since the rule change and the company had tried since 2007 to persuade the Civil Aviation Authority (CAA) to ground Fletchers modified with turbine-powered engines -- a move tantamount to "putting a V8 in a Mini Minor", PAL director Pat McLaughlan said.

But the CAA refuted that modifications were behind the crashes and told the newspaper it had extensively assessed the Fletcher FU-24 aircraft in light of the claims.

"(The CAA) has been working with all members of the aviation community on an ongoing basis to improve the safety of the FU-24 aircraft," CAA spokesman Bill Sommer said in a statement.

"A massive amount of work has been done in this area", much of which focussed on problems with the plane's tail fin stability, he said.

Skydive NZ had been operating the doomed Fox Glacier flight and PAL said while it could have been prevented, it did not blame the operator.

"It's never one instance - it's a whole series of things. No one broke the law - it's the system that allowed it to happen," PAL chief executive Damian Camp told the newspaper.

TAIC's interim report identifies further lines of inquiry which to be looked at by the full report -- which could be up to two years away.

These are:

* A possible malfunction or problem with the plane;

* the fitting of the Walter engine to the FU24 type aircraft;

* the conversion of the plane for parachuting operations (the plane used to be a cropduster);

* aircraft loading and weight limits;

* lack of passenger restraints; and

* gaps or deficiencies in the regulations which cover parachuting operations.

The commission expanded on a few of these points in the interim report.

The plane was estimated to have been five kilograms above the maximum certified weight of 2203kg.

Its centre of gravity was estimated as 75cm 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.

Following urgent recommendations from TAIC in the week after the crash, the CAA ordered skydive operators to limit the number of people in the main cabin to six.

TAIC found more than six passengers could disrupt the centre of gravity, which could lead to control difficulties. It also advised that passengers should be restrained in the front of the cabin.

TAIC also recommended that the flight manual include more accurate determinations of the centre of gravity.

None of the parachutists on board was restrained.

The role of restraints was previously been looked at by TAIC and recommendations made to the CAA calling for a study on the issue. The CAA in 2003 decided against requiring restraints for smaller aircraft carrying fewer than 10 parachutists.

- NZPA