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Summary

Summary

The crew were operating a de Havilland Canada DHC-6 Twin Otter aircraft in Exercise Highland Pursuit 2/97. The purpose of the exercise, which was conducted by No. 173 Surveillance Squadron, 1st Aviation Regiment, Australian Army, was to provide tropical mountainous flying training in Papua New Guinea. There were three trainees and one training pilot on board the aircraft.

On Sunday, 9 November 1997, the third day of flying operations in Papua New Guinea, the crew were conducting a flight from Madang and return via a number of airstrips in the central highlands. When haze and cloud prevented them flying the flight-planned direct track between the Koinambe and Simbai airstrips, they decided to fly north-west via the Jimi River valley and one of its tributaries. Two of the trainees were occupying the cockpit seats, one as flying pilot and the other as navigating pilot using a 1:1,000,000-scale chart. When the crew turned the aircraft to follow a tributary off the Jimi River, the training pilot was in the aircraft cabin.

A few minutes later, their discussion regarding the progress of the flight attracted the attention of the training pilot. By this time, however, the position of the aircraft in the valley, and its available performance, were such that an escape from the valley was not possible. The aircraft collided with trees before impacting steeply sloping ground.

It was subsequently established that when the crew turned from the Jimi River, they entered the wrong valley. Calculations based on the manufacturer's performance data showed that the aircraft did not have sufficient performance to outclimb the increase in terrain elevation from the Jimi River valley to cross the Bismarck Ranges via this valley. There was a low level of experience and corporate knowledge within the Army regarding the operations of fixed-wing aircraft such as the Twin Otter in tropical mountainous areas.

Against this background, deficiencies were identified in the planning and preparation for the exercise, including risk assessment and the selection and briefing of the training pilot.

 
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