The Transportation Safety Board of Canada (TSB) released its investigative report into the September 2022 small plane crash near Donalta, Alta., that cost the life of the 39-year-old pilot.
The TSB report rules out weather, mechanical failure, technical malfunctions or medical issues as reasons the plane — that was applying herbicide on a field on Sept. 12 — would have trouble operating properly that day.
The investigation found that after leaving Bawlf (Blackwells) Aerodrome at 8:50 a.m., the pilot of the Arty’s Air Service Ltd. Air Tractor AT-502B aircraft headed south to a field that was to be sprayed.
“The pilot sprayed the field in a consistent north–south pattern until the entire field had been sprayed,” TSB wrote.
“He then did two full east–west passes to cover off the ends of the field. All of the turns conducted during the application of chemical mixture were left turns and were consistent with altitude gains of ±300 feet above ground level.
“On the third-to-last turn in the middle of the field, the pilot conducted a right course reversal with a tight radius and a steep climb, resulting in an altitude increase of more than 500 feet above ground level,” the TSB report found.
Someone watching from their parked vehicle saw the plane start to climb upwards, TSB said.
“The climb was then observed getting steeper than the previous climbs until the aircraft appeared to stop, the nose dropped, and the aircraft began to roll to the right.”
The plane crashed on Range Road 190, just south of the intersection with Township Road 420A, “vertical, nose-down.”
The aircraft was destroyed on impact, TSB said, adding “the crash was not survivable.”
According to the TSB findings, the pilot was in his third season flying with Arty’s Air Service. He had completed all his necessary training and competency checks. His airline transport pilot licence and Category 1 medical certificate were valid. The pilot had logged a total of 6,190 flight hours, at least 600 of which were in the Air Tractor AT-502B.
“A review of the pilot’s activities in the days leading up to the accident indicated that he was well rested and that the operational pace was slowing down at the end of the aerial application season,” TSB said.
The TSB investigation also noted this: “The company’s flight operations manual provides no guidance on bank angles and climb rates during course reversals other than to say that they must be done in accordance with the Canadian Aviation Regulations and the National Aerial Pesticide Application Manual.
“Over the two flight days before the accident day, the aircraft’s AG NAV unit recorded the occurrence pilot performing multiple course reversals at low altitude with steep climbs and turns, which if coordinated, would have required bank angles in excess of 45 degrees.”
The report includes a section explaining aerodynamic stalls.
“An aerodynamic stall occurs when the wing’s angle of attack exceeds the critical angle at which the smooth airflow begins to separate from the wing. When a wing stalls, the airflow breaks away from the upper surface, and the amount of lift generated is reduced to below that needed to support the aircraft.
“Accelerated stalls, which occur at higher airspeed due to the increased load factor on the wing, are usually more severe than unaccelerated stalls and are often unexpected.”
The TSB report ends with a safety message to pilots.
“Performing course reversals with steep climbs and bank angles greater than 45 degrees increases the likelihood of an aerodynamic stall, which could lead to a spin.
“Encountering a stall or spin at low altitudes can result in a collision with terrain when there is insufficient altitude available to recover the aircraft.”
Comments