What happened
Following a landing, the pilot began taxiing down runway 17. During this phase of ground movement, the pilot reported that the braking system failed completely. As the aircraft continued to move without deceleration, the pilot recognized that the brakes were no longer holding pressure. To prevent the aircraft from entering a nearby highway, the pilot made an emergency decision to turn left off the side of the runway. During this maneuver, the nose gear struck a four-foot-deep ditch, causing the aircraft to pitch forward and nosed over.
The investigation
Post-accident examination of the braking system revealed significant mechanical defects. When pressure was applied, the brakes felt soft and spongy rather than firm. Inspectors observed hydraulic fluid leaking from the vent hole located on the master cylinder. Further disassembly confirmed that the internal diaphragm within the cylinder had split, which allowed fluid to escape and resulted in a total loss of braking action.
Findings
The primary factor leading to the accident was the failure of the brake system due to a split diaphragm in the master cylinder. This mechanical defect caused hydraulic fluid leakage and rendered the brakes ineffective during taxi operations.