Air crash commemorated

'Metal fatigue is inevitable, metal fatigue is lethal, metal fatigue is manageable.”

This was the opening statement made by former Civil Aviation Authority of Australia principal engineer fatigue evaluation Steve Swift in a lecture given this week at Classic Flyers.

Rev Dr Richard Waugh blesses the memorial to those who died in the crash on Mount Ruapehu, watched by Captain Alistair McLeod (left) and John Roake. Photo: April Stark.

The audience of more than 60 people was mainly family and friends of the pilot and passengers of the Bay of Plenty Airways Aero Commander ZK-BWA to crash on Mount Ruapehu in 1961.

The November 26 commemoration at Classic Flyers was the first opportunity they had had to hear first hand from the men who investigated the cause of the crash.

Steve's lecture showed the effects of fatigue and that while it cannot be prevented it can be managed.

Small cracks in aircraft can now be found and repaired before they can cause crashes.

The crash was the first of 24 Aero Commander crashes now attributed to metal fatigue causing wing spar fractures, worldwide.

Steve passed around a piece of metal showing fatigue from another Aero Commander around the audience saying: 'This was found because of the lessons learned from investigations into the tragic crash of ZK-BWA.”

Investigation of remnants of the Aero Commander was carried out by the other lecturer on the day, Canterbury University Department of Engineering Emeritus Professor Les Erasmus.

Les displayed slides produced using electron fractography which determines the origins of cracking to show the microscopic cracks in part of the spar cap of the Aero Commander wing.

He explained how the cyclic loads placed on the metal parts of the wing caused by take offs, landings and turbulence in flight, causes the metal fatigue.

The cracking cannot be seen with the unaided eye.

Aircraft components subject to the cyclic loading are now replaced at the end of a predetermined number of flying hours because of work done by engineers specialising in fatigue evaluation.

Les' investigation over 15 years determined the cause of the crash was metal fatigue rather than pilot error as was first thought.

Les has no doubt the fatigue in the main spar caused the fracture of the spar and the subsequent separation of the starboard wing from the aircraft, while it was in flight over Mount Ruapehu.

About 200 people attended the service commemorating the crash and the history of the airline, which was a pioneer in commuter air travel in the Bay of Plenty.

Families of those who died in the crash travelled from as far away as Britain, Australia and the South Island to attend the service.

It was the first time the families had met each other and the first time they could share the stories of their loved ones with each other.

The service was organised by Rev Dr Richard Waugh, an aviation historian who has organised memorials around New Zealand for nine airliner accidents in civil aviation in New Zealand from 1938 to 1963.

The memorial was unveiled by Captain Alistair McLeod, the former chief pilot and operations manager of Bay of Plenty Airways and Mr John Roake, a friend of the airline founder Alf Bartlett.

Two cabinets depicting the crash and the airline, which include the memorial plaque, are now on permanent display at Classic Flyers.

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