A helicopter carrying three provincial government employees conducting a wildlife survey was flying at low altitude 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 unintended right turn preceded the Jan. 23 crash of a Bell 206B helicopter in the woods in Flagstaff County, about 150 kilometers southeast of Edmonton. The three civil servants and the pilot were taken to hospital, but no one died.
The report, released Wednesday, noted that the purpose of the investigation was to improve transportation safety. It does not attribute error or make recommendations.
According to the TSB report, the aircraft left Camrose Airport on Jan. 23 for a series of wildlife survey flights on behalf of the provincial government. This was the sixth day in a row that they had been held.
Research flights are usually conducted at about 300 feet above ground level at a speed of about 90 knots. When observers spot wildlife, the helicopter usually slows down, descends and maneuvers at low altitude and slow speed so that the animals can be counted and classified.
The flight completed one survey line at 9:20 a.m. that day and continued north to the next.
The report said that around 9:45 a.m., several animals were spotted in the bushes and the pilot performed a “360-degree descending left turn with delay” to allow observers to count and classify. The helicopter was 80 feet above the ground and traveling at about nine knots.
“At this point, the helicopter entered an uncommanded right turn,” the report said.
Impact injuries
The pilot attempted to regain directional control, but the helicopter fell and hit the ground “with little or no forward speed”, coming to rest in bushes. It was upright and mostly intact, the report said.
The report said the landing skids moved apart due to the impact and part of the rear landing skid was pushed into the fuselage, rupturing the field cage.
“All occupants were seriously injured by the force of the impact and were contaminated with jet fuel.”
A passenger called 911, which arrived about an hour after the collision and took the four passengers to hospital.
Loss of tail rotor efficiency
The Bell 206B main rotor blades, when viewed from above, rotate clockwise. The rotation creates a torque reaction in the opposite direction, causing the helicopter to yaw to the right.
To counteract this, the tail rotor produces side thrust. According to the report, the pilot applies pressure to the anti-torque pedals to increase or decrease thrust as needed.
When a spin is not expected, it is called an unexpected spin or loss of tail rotor efficiency (LTE).
“Any single-rotor helicopter flying at low speeds can experience LTE,” the report said.
“This phenomenon is not related to equipment failure or faulty maintenance; rather, it is the result of the tail rotor not providing sufficient thrust to maintain directional control.’
Safety messages
The investigation determined that the pilot, who had worked for Delta since April 2021, held the appropriate license and that fatigue was likely not a factor, the report said.
At the time of the incident, the wind was strong and coming from the left as the turn was completed.
Four regions of relative wind azimuth were noted as favorable for LTE, two affecting the main and tail rotors present at the time of the crash.
In the concluding section on safety messages, the report says that some helicopter operations, such as slow-speed wildlife surveys, are at greater risk than LTE.
“Pilots are reminded that flying an aircraft at low altitude leaves little margin or error and reduces the time and altitude available to effectively manage any aircraft contingency,” it said.
Add Comment