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Pilot and media personality Graeme (Shirley) Strachan was fatally injured when he lost control of the helicopter he was flying after it was damaged in severe mountain wave turbulence and crashed on the north-east slope of Mount Archer, Queensland on 29 August 2001.

This was the main finding in the final accident report released today by the Australian Transport Safety Bureau.

"The extensive damage to the helicopter, severed tailboom and the location of parts on the ground, led transport safety investigators to conclude that the main rotor blade may have contacted the tailboom in flight," Air Safety Deputy Director, Alan Stray said.

"This type of damage was consistent with flying into mountain wave turbulence, and may have occurred from one of two events: blade flapping (divergence of the main rotor blade from its normal plane of rotation encountered during severe turbulence) or the pilot's instinctive reaction to pull up after a sudden nose-down pitch from a change in the helicopter control input (collective lever friction failure in turbulence causing the non-powered collective lever to drop).

"Weather conditions at the time were conducive to mountain waves on the north-east slope of Mount Archer near where the wreckage was found."

The pilot was on a training navigation flight and had not been briefed on the weather conditions by the flight training school before departure from Maroochydore. In addition, the pilot's flight planning notes did not take into account the forecast winds.

Encounters with mountain waves have led to catastrophic events in the past and pilots needed to be highly aware of their potentially deadly effects when interpreting weather forecasts and planning flight over mountainous terrain.

"In Australia mountain waves are experienced over and on the lee side of mountain ranges in the south-east of the continent and in westerly wind flows over the east coast in late winter and early spring. It is absolutely essential that aviators are aware of the wind and its potential effects on aircraft.

"We hope that out of this tragedy, a greater pilot awareness of mountain waves will save lives in the future," Mr Stray said.

The helicopter had no known maintenance deficiencies and was considered capable of normal flight prior to the accident.

ATSB report

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Last update 19 January 2017