What happened
The aircraft experienced a collision with a snowbank while attempting to land. The incident occurred during the landing phase of flight, resulting in significant damage to the airframe and landing gear assembly.
The investigation
A thorough mechanical examination was conducted by a qualified Airframe and Powerplant (A&P) mechanic to determine the root cause of the failure. The inspection focused on the braking system components, specifically the master cylinder assembly.
The investigation revealed a critical manufacturing or maintenance defect within the master cylinder. Specifically, the lock-o-seal component possessed improper clearance dimensions. This deviation from specifications was not immediately apparent during standard visual inspections but had significant functional consequences.
Findings
The improper clearance of the lock-o-seal restricted the return flow of brake fluid back to the reservoir after braking pressure was released. Under normal operation, brake fluid must return freely to accommodate pedal release and prevent drag. In this case, the restriction caused the brake on the left main landing gear to remain engaged or locked.
The continuous application of braking force on only one side of the aircraft created an asymmetric thrust condition during the rollout. This imbalance resulted in a loss of steering control, making it impossible for the pilot to maintain the runway centerline. The uncontrolled turn led directly to the collision with the adjacent snowbank.
The primary causal factor was identified as the mechanical failure of the brake system due to the defective seal clearance, which prevented proper hydraulic function and led to the locked wheel condition.