Cause of Antarctic plane crash that killed 3 Canadians unknown

Investigators have concluded that the cause of a plane crash that killed three Canadians in Antarctica may never be known.

Cockpit voice recorder was not working when the Twin Otter owned by Kenn Borek Air crashed

The wreckage from a Canadian plane that crashed in Antarctica on Jan. 23, 2013 killing three Canadians on board. Investigators with the Transportation Safety Board have concluded the cause of the crash may never be known. (Drew Coleman/Antarctica NZ/Canadian Press)

Investigators have been unable to pin down the cause of a plane crash that killed three Canadians high on an Antarctic mountainside.

The men died in January 2013 when their Twin Otter, owned by Calgary-based Kenn Borek Air, crashed into a crevasse-filled and avalanche-prone slope on the side of one of the frozen continent's highest peaks.

The bodies of Bob Heath, 55, of Inuvik, N.W.T., Perry Andersen, 36, of Collingwood, Ont., and Mike Denton, 25, of Calgary remain on Mount Elizabeth, entombed in the wreckage of the plane in which they died.

A Transportation Safety Board report released Friday details as much as is known about the fatal flight, which departed from South Pole Station with a load of fuel for an Italian research team at Terra Nova Bay.

Everything seemed normal for the first two hours of the flight.

But sometime between 8 a.m. and 8:30 a.m., something went wrong.

Attempts to reconstruct the weather in the area at the time suggest a heavy layer of cloud hung around Mount Elizabeth. Flight records indicate Heath — who had eight seasons of flying experience in Antarctica — turned his plane to the left in a direct route to his destination.

But the plane didn't have enough altitude to clear the peak and crashed into it at about 4,000 metres above sea level.

Because the cockpit voice recorder was not working at the time, the board was unable to say definitively what caused the crash.

But it points out that although the plane had a sophisticated system for warning pilots about terrain hazards, the electronic database that system relies on isn't available for Antarctica. A GPS in the plane may have given the pilots some warning, but not enough for them to climb out of trouble.

"At 45 seconds prior to impact, it appears that (the plane) entered a climb, which may correlate with receipt of a 30-second terrain advisory," the report says.

Heavy cloud and high winds prevented searchers from finding the plane for two days. A rescue team reached the site a day after that, but concluded it was too dangerous to mount a recovery.

The tail of the plane continues to stick out from the snowy mountainside. A board spokesman said Friday a recovery operation is not planned.

The board says Kenn Borek Air made a number of changes after the accident, including improvements to navigation charts for the Antarctic.