What happened
The pilot reported that the initial touchdown and the first 300 feet of the rollout proceeded normally. However, upon applying the brakes, the left brake failed, causing the aircraft to swerve to the right and depart the side of the runway.
Because there were people and equipment located near the runway and directly in the aircraft's path, the pilot used nose wheel steering and right throttle control to attempt to redirect the plane. The aircraft traveled approximately 80 feet over freshly graded terrain before entering an open field characterized by tall grass. During the excursion, the aircraft struck a ditch and then collided with an abandoned truck before finally coming to a stop.
The investigation
An inspection of the brake system was conducted shortly after the accident. Investigators found that the left brake pedal could reach full travel without providing any apparent braking action. When the pilot applied a pumping action to the pedal, there was a gradual rise in pressure and the return of braking functionality.
While further examination of the system did not identify any mechanical failures or malfunctions, the brake lines were subsequently bled. During this process, a considerable amount of air bubbles were observed within the lines.