Turbulence blamed for crash

Press, 5 July 1985, Page 3

Turbulence blamed for crash

The fatal crash of a Mount Cook Group Cessna ski-plane on the Tasman Glacier in August last year was probably caused by turbulence which resulted in an irrecoverable rate of descent, according to the air accident report. Three passengers were killed, and the pilot and two other passengers were seriously injured in the crash, which occurred just before the pilot’s planned landing on the glacier to drop off skiers.

The air accident report said that weather conditions on the crash day were con-< ducive to occasional turbulence and downdraughts over the Tasman neve area, although ski-planes often worked in these conditions without mishap.

“The effects due to the rarely encountered combination of northerly winds associated with anticyclonic conditions may not have been expected or anticipated by the pilot,” the report said.

The accident occurred after the snow and the weather in the area had been adequately assessed. The pilot of the crashed aircraft, Mr Brendan Harris, had already made two low runs over the snowfield to assess landing conditions when the accident occurred. Mr Harris has no recollection of events on the day of the accident. The accident report said that when the aircraft had taken off from Mount Cook it was in excess of the maximum authorised take-

off weight for take-off from Mount Cook, but at the time of the accident its weight was “close' to the maximum authorised weight.” This change can be attributed to fuel burn in the intervening periods. The report also said that the excess take-off weight and its imbalance were a result of insufficient supervision of a Civil Aviation load sheet requirement dispensation. It also said that the altered centre of gravity, on its own, would not have significantly adversely affected the handling or stall characteristics of the aircraft. But the combination of centre of gravity, weight of the aircraft, and the external load of skis had “increased the susceptibility of the aircraft to a stall in turbulent flight conditions and added to the time taken to achieve a recovery in such an event.” A series of recommendations ■ were made to the Director of Civil Aviation after the accident and subsequent investigation. The first concerned the carriage of passengers during flights made to assess weather and or snow markings. The air accident inspectors recommended that no passengers be carried on

these flights. A spokesman for the Mount Cook Group, Mr Ted Beckett, said last evening that snow marking landings were now made without passengers on board. The second recommendation was that there be a review of the load sheet requirement dispensation for ski-plane flights, in particular the conditions specified in respect of baggage or freight, maximum permissible fuel load, the disposition of passengers, their baggage and equipment and the use of “standard passenger weights.” Mr Beckett said last evening that the airline’s present approved practice was to weigh passengers where medium to large passengers were involved. “Where the passengers are small the loadsheets incorporate the dispensation standard weights,” he said. The report also said that thought should be given to the provision of a suitable upper torso restraint for all occupants, with a shoulder restraint being required for the passenger in the front right seat. An upper torso restraint refers to a diagonal belt over one shoulder; a shoulder restraint is a belt over each shoulder and clip-

ping into the lap belt. “Where applicable new restraint harnesses have been fitted or are being fitted and these include full shoulder harnesses for front seat passengers,” Mr Beckett said. At the end of the report, Mr Ron Chippindale, * the chief inspector of air accidents, said that neither the Director of Civil Aviation nor the Mount Cook Group accepted that the company operations specifications required that the examination of snow conditions be made without fare-paying passengers on board. Mr Chippindale’s report referred to a “classic accident in which no particular cause could be singled out,” said Mr Nelson Tolerton, chief executive of the Mount Cook Group. “Like many accidents, it came about through a combination of factors. Our sympathy will always be with the relatives of those killed and injured,” he said. A second Mount Cook Group ski-plane crashed on an upper neve of the Tasman Glacier, less than seven weeks after the fatal accident. The six people aboard that aircraft escaped with only cuts and bruises.