Accident Overview
The accident occurred during the landing rollout on a gravel runway. The airplane was equipped with tundra tires and a tailwheel configuration. As the pilot touched down, the brakes locked, causing the tires to skid on the gravel surface. The left wing subsequently struck the ground. The pilot reported that the brakes remained locked for approximately two hours after the accident, after which the wheels turned normally.
Aircraft Details
The airplane utilizes a separate master brake cylinder and brake pedal assembly for each main wheel. The master cylinders and brake pedals are located on the cockpit floor adjacent to the rudder pedals. The brake cylinders are serviced by adding hydraulic brake fluid through a small cap on top of each cylinder.
Maintenance Issues
The airplane had just undergone a 100-hour inspection performed by a contract maintenance facility. According to maintenance personnel from the operator, the locked brake condition resulted from two factors: overservicing of the brake cylinders (excess hydraulic fluid) and heating of the cylinder assembly. The heat source was a short section of tubing the pilot used to direct heater air at his feet during the flight.
Sequence of Events
During the flight, the pilot employed a short section of tubing to route heater air toward his feet. On landing, the brakes locked upon touchdown. The skidding tires and subsequent wing strike occurred on the gravel runway surface. The pilot noted the brakes remained locked for about two hours post-accident, after which they released and functioned normally.
Brake System Description
The airplane features independent brake circuits for each main wheel. Each master cylinder is paired with a brake pedal, and the system is serviced via caps on the cylinders. The combination of fluid overservicing and thermal expansion from the directed heater air is believed to have caused hydraulic lock-up.