Winnipeg, Manitoba, 14 April 2021 — In its investigation report (A20C0016) released today, the Transportation Safety Board of Canada (TSB) found that an interruption while conducting checklist procedures and an incomplete checklist led to the February 2020 runway excursion involving an aircraft operated by Perimeter Aviation Ltd. at the Dryden Regional Airport, Ontario. One passenger sustained serious injuries.
Occurrence aircraft after coming to a stop (Source: Ontario Provincial Police)
On 24 February 2020, the Fairchild SA227-DC Metro 23 aircraft operated by Perimeter Aviation as Bearskin Airlines flight 344 was conducting a flight from Dryden Regional Airport, Ontario, to Sioux Lookout Airport, Ontario, with two crew members and six passengers on board. At 1610 local time, as the aircraft commenced its take-off roll, directional control was lost which caused the aircraft to exit the right side of the runway and come to rest approximately 18 m off the side in about 46 cm of snow. The aircraft was substantially damaged. The flight crew and passengers egressed through the main cabin door.
The investigation found that while the crew was carrying out the “Before Taxi” checklist, the task of disengaging the propeller start locks was initiated; however, it was interrupted and not completed. After the captain told the first officer to stand by, the crew’s focus shifted to other tasks. It is likely that this slip of attention resulted in the engine power levers not being pulled over the flight idle gate to release the start locks. The “Before Taxi” checklist did not contain a task to ensure that the start locks had been released and, as a result, the crew began taxiing unaware that the right propeller start locks were still engaged. It was determined that, during the takeoff roll, the power was advanced through 20%, but the “positive torque” call required by standard operating procedures was not made, and the engine torque differential was not noticed by the crew. As a result, power lever advancement continued although the right engine thrust remained near zero. The engaged start locks prevented the right propeller from producing the required thrust, which resulted in a significant thrust differential. With less thrust being generated by the right engine, the aircraft experienced a loss of directional control and exited the runway. The injuries to the passenger resulted from propeller blade fragments penetrating the cabin wall during impact with a frozen snowbank.
Following the occurrence, Perimeter Aviation changed its procedures and checklists to better ensure that the propeller start locks are disengaged before taxiing and to raise awareness and understanding of the Metro aircraft’s propeller start lock system. The company also enhanced training for less experienced flight crew members.
See the investigation page for more information.