What happened
On a scheduled passenger flight from Sudbury, Ontario, to North Bay, a Fairchild SA227-AC aircraft, registration C-FFZN, experienced a runway excursion during its landing roll on runway 08. The flight, operated by Bearskin, was carrying two crew members and 16 passengers under instrument flight rules.
Upon touchdown at the runway threshold, the aircraft's nose pitched down abruptly, and the plane began to veer toward the left side of the runway. Despite the co-pilot applying heavy right brake and reverse thrust on the right engine, the aircraft drifted off the left side of the pavement and into deep snow. The incident resulted in damage to the No. 1 engine and propeller, but there were no injuries to the 18 people on board.
The investigation
The investigation focused on the mechanical state of the landing gear and the environmental conditions at the time of the accident. Investigators noted that the weather at both Sudbury and North Bay involved freezing temperatures and blowing snow.
Examination of the left main landing gear revealed flat spots on both tires, indicating that the wheels had been skidding rather than rotating. Maintenance crews found that the left wheels would not rotate until heat was applied to the brake assembly. The investigation also looked into the brake system design, noting that the aircraft lacks a mechanism to prevent blowing snow from entering the brake disk area. While the crew reported attempting to use the right brake to correct the veer, investigators found no evidence of brake activation on the right side during the landing roll.
Findings
- The primary cause of the loss of directional control was a frozen left brake that prevented the left wheels from rotating during the landing roll.
- The freezing of the brake was likely caused by snow entering the brake assembly, melting on warm surfaces during departure, and subsequently refreezing during the flight or when the landing gear was extended into the cold slipstream.
- The aircraft was operating in freezing temperatures with active snow and blowing snow conditions.