Final Report of Transportation Safety Board of Canada - TSB / REPORT A20C0016.
TSB's Final report on the Runway excursion of a SA227-DC Metro 23 (Regd.C-GJVB) on 24th February 2020 indicates the interruption in the Crew check list procedure, before taxi.
• On 24 February 2020, the Fairchild SA227-DC Metro 23 aircraft (registration C-GJVB, serial number DC-902B), operated by Perimeter Aviation LP as Bearskin Airlines flight 344, was conducting a visual flight rules flight from Dryden Regional Airport, Ontario, to Sioux Lookout Airport, Ontario, with 2 crew members and 6 passengers on board.
• At 1610 Central Standard Time, as the aircraft commenced its take-off roll on Runway 12, directional control was lost. The aircraft ran off the right side of the runway approximately 150 m from the runway threshold lights and struck a frozen snowbank.
• It came to a rest in an upright position approximately 18 m off the side of the runway and in about 46 cm of snow. One passenger sustained serious injuries. The aircraft was substantially damaged. The flight crew and passengers egressed through the main cabin door.
► On 24th February 2020, the Perimeter Aviation LP (Perimeter Aviation) Fairchild SA227-DC Metro 23 (registration C-GJVB, serial number DC-902B) was conducting Bearskin Airlines flight 344 (BLS344) between Dryden Regional Airport (CYHD), Ontario, and Sioux Lookout Airport (CYXL), Ontario, with 2 crew members and 6 passengers on board.
► This was the 6th flight of the day for the flight crew. The first officer (FO), who sat in the right seat, was to be the pilot flying (PF), and the captain, who sat in the left seat, was to be the pilot taxiing and the pilot monitoring (PM) for the flight.
► Before the engine start at CYHD, the FO provided a safety briefing to the passengers. The crew then completed the “Engine Start” checklist, followed by the “After Start” checklist and the “Before Taxi” checklist.
► While conducting the “Before Taxi” checklist, the FO initiated the “Start Locks” task, which has 3 subtasks required to be completed by both the captain and the FO.
► The captain instructed the FO to stand by , after which the FO then verbalized the correct “Start Locks” subtask response. There was no response from the captain.
► Approximately 7 seconds later, the captain began assessing runway conditions and then engaged for a period of time with Sioux Lookout Radio about flight plan and departure details.
► The captain then called for the “Before Takeoff” checklist, which was completed, and began to taxi the aircraft to Runway 12 for takeoff. Directional control of the aircraft during taxi was accomplished using the nose wheel steering and no differential thrust for turns was required.
► After completing the “Line Up” checklist, the captain transferred aircraft control to the FO. At approximately 1610,1 take-off power was applied and, while the aircraft was accelerating during the take-off roll, directional control was lost.
► The aircraft ran off the right side of the runway approximately 150 m from the runway threshold lights. The aircraft struck a frozen snowbank and came to a rest in an upright position, about 18 m off the side of the runway and in about 46 cm of snow (Figure 1). The crew then shut down the engines following the “Stopping Engines” checklist.
1. While the crew was carrying out the "Before Taxi" checklist , the "Start Locks" task was initiated ; however, it was interrupted and not completed.
2. 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 power levers not being pulled over the flight idle gate to release the start locks.
3. The "Before Taxi" checklist did not contain a task to ensure that the start locks were removed and, as a result, the crew began taxiing unaware that the propellers were still on the locks.
4. After the engine was started or while the occurrence aircraft commenced taxiing for departure, it is likely that slight or rapid transient movements of the engine power levers, which were needed to taxi the aircraft, resulted in the release of the left propeller start locks while the right propeller start locks remained engaged.
5. As the power was advanced through 20%, 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 torque/thrust remained near zero.
6. The engaged start locks on the right propeller prevented forward thrust, which resulted in a significant thrust differential. This differential thrust during the take-off roll resulted in a loss of directional control of the aircraft and, ultimately, a lateral runway excursion.
7. Following the runway excursion, the propellers, which were operating at a high rpm, shattered and splintered when they struck a frozen snowbank.
8. High-energy release of the nickel-cobalt erosion strips and splintered wood core debris from the propeller blades penetrated the reinforcement panel, fuselage skin and cabin wall, and resulted in serious injuries to a passenger sitting next to the penetrated cabin wall.
Report and Picture Source : Transportation Safety Board of Canada .
