Air Force halves life of helicopter blades

The life of helicopter blades on the Air Force's Iroquois helicopters has been halved as a safety precaution after a blade on a machine in East Timor began to delaminate nearly two years ago.

The Air Force and the blade manufacturers cannot agree on the cause of the delamination - a separation between the blade and its metal fitting.

The Air Force said as a safety precaution it would halve the life of the blades from 2500 hours to 1200 hours.

The delamination began where the blade material joined the metal fitting at its inner end.

The Air Force has 14 two-bladed Iroquois helicopters.

Each blade is worth nearly $100,000.

The crack was found in July, 2001, during a pre-flight check of a helicopter based in Suai, East Timor, as part of the New Zealand contribution to the United Nations peacekeeping force.

Had the machine taken off and the blade failed, the helicopter would probably have been torn apart in the air, the Air Force said.

It stopped flying the 14 helicopters in its fleet, 10 in New Zealand and four in East Timor, until the blades could be checked and replaced if necessary.

It also began an extensive investigation of the cause of the damage.

The Air Force's director of logistics, Group Captain Peter Guy, said the blade had delaminated at the hub assembly on the inner end of the blade.

The Air Force believed the blade delaminated because the adhesive did not perform adequately.

That view was not shared by the manufacturers.

However, Group Captain Guy said the helicopters had been subjected to heavier loads recently than in the past 20 years although they had been flown within the guidelines established by the manufacturer.

"We are both satisfied the specifications of the blades are sound," he said.

"Our problem is that our blades are not lasting as long as we want them to last."

In East Timor the helicopters were flying under heavy loads in a hot and humid environment, in thin air and at high altitudes.

"Add it all together and we seem to have a combination that is causing our blades to degrade faster than the norm."

Group Captain Guy said a new inspection technique had been instigated that involved removing the blades and testing them for delamination.

The 35-year-old helicopters are becoming increasingly hard to maintain and are due to be replaced with new machines in the next few years.

- NZPA