A loss of visual reference led to a controlled flight into terrain that damaged the skis of a Summit Helicopters Bell 407 in British Columbia, the Transportation Safety Board of Canada (TSB) has found.
The incident occurred during a visual flight rules (VFR) flight on Jan. 4, 2023, at Treston Lake, about 860 miles (1,385 kilometers) north of Vancouver, the TSB said.
With a pilot and four passengers on board, the aircraft departed from Northwest Regional Airport in Terrace, British Columbia (Terrace Airport) toward the Northern Escape Mountain Lodge.
The pilot was informed that low-level fog moved into the area surrounding the lodge and decided to descend and follow the Kitsumkalum River towards Treston Lake, “a route he had successfully taken on previous flights when visibility was poor,” the TSB said.
As the helicopter flew over the snow-covered lake, the pilot momentarily lost outside visual reference and the landing skids hit the frozen surface of the lake.
The landing skids were “significantly damaged” during the impact, but the pilot recovered and climbed above the fog layer, the TSB found.
The flight was completed without further incident. There were no injuries.
Although localized fog conditions were forecast on the planned route, the short duration of the flight (about 15 minutes), the pilot’s expectation of suitable weather conditions, and a risk level assessed as “low,” among other factors, led the pilot to depart on a VFR flight.
Visibility continued to deteriorate after the pilot descended and followed the river, a TSB investigation found.
“Once the helicopter was over the snow-covered lake, the pilot found himself in conditions of flat light, whiteout, and fog that reduced his ability to effectively assess his speed, attitude, and altitude,” said the TSB.
“This ultimately contributed to the pilot’s loss of visual references and spatial disorientation, which led to the collision with the frozen surface of the lake.”
After the incident, Summit Helicopters expanded the ground briefing portion of low-visibility operations in its annual training and added this incident to its annual crew resource management training with an emphasis on pilot decision-making, workload management, and situational awareness, the TSB found.
“Additionally, the company discovered that it was possible to skip the flight risk assessment step when filing a flight itinerary for VFR operations,” the TSB said.
“This issue has been rectified and it is no longer possible for pilots to file a flight itinerary for VFR flights without first filling out a flight risk assessment.”
The TSB is an independent agency focused on advancing transportation safety. Its role is not to assign fault or determine criminal or civil liability.
