What happened
On a winter afternoon at Dryden Airport, a Bearskin Air Service Fairchild Metro SA227-AC, registered C-FYAG, was completing a scheduled flight from Kenora, Ontario. The aircraft, carrying two pilots and ten passengers, touched down on Runway 11 at 1457 CST. While the landing configuration and speed were correct, the aircraft immediately began to yaw to the left upon touchdown.
As the aircraft entered the landing roll, the pilot flying attempted to correct the deviation using right rudder and reverse thrust on the right engine. However, the left main landing gear wheels failed to rotate. The aircraft drifted off the left side of the runway, traveling approximately 15 and a half feet into deep snow. The excursion ended about 2900 feet from the runway threshold. While the aircraft sustained two blown tires on the left main gear, there were no injuries to the crew or passengers.
The investigation
Investigators examined the aircraft's braking system and the environmental conditions leading up to the event. It was determined that during earlier ground operations in Kenora, snow had likely entered the brake assemblies. Because the brakes had been heated during taxi and then exposed to freezing temperatures, the moisture had frozen, effectively locking the left main gear wheels.
Technical analysis of the cockpit controls revealed that the first officer's foot position on the rudder pedals played a critical role in the loss of control. With his heels on the floor, the pilot was unable to shift his feet upward to apply the necessary differential braking without simultaneously releasing the rudder pressure required to counteract the yaw. Furthermore, the nosewheel steering was not engaged because the crew was preoccupied with the immediate directional deviation.
Findings
- The primary cause of the excursion was the frozen brake assemblies on the left main landing gear, which prevented the wheels from rotating.
- The first officer's foot position and the pressure applied to the rudder pedals prevented the effective use of differential braking and nosewheel steering to maintain directional control.
- Environmental conditions at the departure airport allowed snow to penetrate the brake assemblies, which subsequently froze during flight.
- The continued operation of the runway at Dryden while the disabled aircraft and various vehicles were within the runway strip increased the risk to other aircraft movements.
- There was a lack of standardized industry guidance or manufacturer-provided emergency procedures regarding the management of frozen brakes.