Low-flying chopper experienced 'uncommanded rotation' before crashing near Camrose : report

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The Bell 206B crashed on Jan. 23, 2022, during a wildlife survey flight carrying three government workers and the pilot. All occupants were taken to hospital. (Transportation Safety Board of Canada - image credit)
The Bell 206B crashed on Jan. 23, 2022, during a wildlife survey flight carrying three government workers and the pilot. All occupants were taken to hospital. (Transportation Safety Board of Canada - image credit)

A helicopter carrying three provincial government workers conducting a wildlife survey was flying at low altitudes when it crashed near Camrose, Alta., in January, according to a new report from the Transportation Safety Board of Canada.

The report found that an unintentional rotation to the right preceded the Jan. 23 crash of the Bell 206B helicopter in the woods in Flagstaff County, about 150 kilometres southeast of Edmonton. The three government workers and pilot were taken to hospital but no one was killed.

The report, released Wednesday, notes that the investigations purpose was to advance transportation safety. It does not assign fault nor does it provide recommendations.

According to the TSB report, the aircraft left the Camrose Aerodrome on Jan. 23 for a series of wildlife survey flights on behalf of the provincial government. It was the sixth consecutive day these had been conducted.

Survey flights were generally flown about 300 feet above ground level at a speed of around 90 knots. When observers spotted wildlife, the helicopter typically slowed, descended and manoeuvred at a low altitude and slow speed so animals could be counted and classified.

The flight completed one survey line at 9:20 a.m. that day and had proceeded north to the next.

The report says that around 9:45 a.m., several animals were spotted in the bush and the pilot performed "a descending, decelerating 360 degree left turn" to allow for observers to count and classify. The helicopter was 80 feet above the ground and moving at a speed of around nine knots.

"At this time, the helicopter entered an uncommanded rotation to the right," reads the report.

Impact injuries

The pilot attempted to regain directional control but the helicopter fell and hit the ground "with little-to-no forward speed," coming to reset in a scrub bush. It was upright and largely intact, the report said.

The report says landing skids were spread apart due to the impact and part of the rear landing skid was pushed into the fuselage, rupturing the field cell.

"All occupants were seriously injured by the impact forces and were contaminated with jet fuel."

A passenger called emergency services, which arrived around an hour after the collision and took all four occupants to hospital.

Loss of tail rotor effectiveness

The Bell 206B's main rotor blades, when seen from above, turn clockwise. The rotation creates a torque reaction in the opposite direction, resulting in the helicopter yawing to the right.

To counter this, the tail rotor produces lateral thrust. According to the report, a pilot applies pressure to the anti-torque pedals to increase or reduce that thrust as required.

When a yawing movement is not expected, it is called an unanticipated yaw or a loss of tail rotor effectiveness (LTE).

"Any single-rotor helicopter flying at low speeds can experience LTE," the report reads.

"This phenomenon is unrelated to equipment failure or defective maintenance; rather, it is the result of the tail rotor not providing sufficient thrust to maintain directional control."

Safety messages

The investigation determined the pilot, who had worked for Delta since April 2021, held the appropriate licence and that fatigue was likely not a factor, the report said.

At the time of the accident, winds were gusty and coming from the left as the turn was being completed.

Four relative wind azimuth regions are noted to be  conducive to an LTE with the two affecting the main and tail rotors being present during the crash.

In the concluding safety messages section, the report says certain helicopter operations like slow-speed wildlife surveys lend themselves to being more at risk of LTEs.

"Pilots are reminded that flying an aircraft at low altitude leaves little margin or error and decreases the time and altitude available to effectively manage any unanticipated aircraft state," it reads.

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