A tight turn at just a few hundred feet sent a Cessna into an unrecoverable stall during a 2024 power line patrol
A low-flying survey plane that crashed near Lloydminster, Alta., in 2024 stalled in a tight turn at just a few hundred feet above the ground, leaving the crew with almost no chance to recover, the Transportation Safety Board of Canada (TSB) has found.
In its investigation report A24C0095, the TSB says the Cessna U206F, operated by KBM Forestry Consultants Inc., was on the second leg of a multi-day aerial power line inspection on 8 September 2024 when the crash occurred. The aircraft had departed Kindersley, Sask., under visual flight rules for work southeast of Lloydminster Airport, with two crew members on board. “The crew shared the duties of pilot and observer; whoever flew in the morning operated the cameras in the afternoon,” the report notes.
Data from on-board cameras showed the aircraft flying along power lines, with the observer taking multiple still photographs of an intersection of lines. After completing one series of passes and photos, “the pilot then turned approximately 190° to the right to allow the observer to take 2 additional photos of the intersection of power lines.”
At about 5:53 p.m. local time, the pilot began another right turn, at roughly 200 to 300 feet above ground level, apparently to rejoin the original track along the line. “During the turn, the aircraft stalled and its bank angle to the right increased,” the TSB found. As the aircraft descended at “a rate of at least 3000 fpm,” it began rolling back toward wings-level, but “three seconds after the stall began, the aircraft impacted terrain.”
The pilot was fatally injured in the crash. The observer, who was seated in a rear-facing observer seat with a five-point harness, suffered serious injuries and died three days later. The aircraft was destroyed. There was no fire before or after impact, and the TSB found no evidence of system or component failure that contributed to the crash. Investigators also concluded that “weather was not considered to be a factor in this occurrence.”
The TSB examined the aircraft’s performance, configuration and stall characteristics, including the effects of its Robertson STOL kit. Investigators estimated the aircraft was flying at 86 to 92 mph calibrated airspeed during the final turn, with a bank angle “slightly higher than the previous turns.” Video evidence suggested the pilot pulled harder on the elevator in the last turn, increasing the load factor on the wings and raising the stall speed. The Board determined “the aircraft experienced a stall during the turn,” and that “the stall occurred at a height at which it would have been difficult to regain control of the aircraft before the collision with the terrain.”
The report underlines that low-altitude work leaves little margin for error when manoeuvring. The power line inspection profile called for heights between 200 and 300 feet above ground while following pre-mapped lines on a tablet, with frequent turns and potential backtracking to capture missed imagery. Those manoeuvres “generally consist of a turn of at least 180° to backtrack and reposition so as not to miss any part of the power line,” the TSB explains.
Both crew members held appropriate licences and ratings, and had received company training that included “low altitude training, stall awareness, safe turn management, and aerial work.” There was no indication their performance was degraded by medical or physiological factors. The aircraft’s stall warning system was designed to sound five to 10 mph above stall and showed no defects during the investigation.
In response to the accident, KBM Forestry Consultants introduced new minimum experience and equipment requirements for low-level survey flights. According to the report, the company now requires that “the pilot-in-command (PIC) must have a minimum of 750 hours of flight experience and a minimum of 50 hours on a similar aircraft type,” with limited room to reduce that threshold. It also mandates that “the PIC and observer must wear properly fitted and maintained flight helmets” and Nomex fire-retardant flight suits and has expanded low-level training to place added emphasis on “stall recovery,” “drift illusions” and “emergency procedures in the low altitude environment.”
The TSB closes the report with a stark reminder for pilots engaged in similar operations: “When required to conduct steep turns at low height, pilots need to be cautious given that there may be insufficient height to recover from an inadvertent stall.”
