Incident Overview
The pilot reported a complete wheel brake failure during taxi for takeoff. As the aircraft neared the end of an inclined taxiway, the pilot applied brakes with little response. Unable to stop, the airplane continued off the end of the taxiway onto rough uneven terrain and eventually came to rest nose-down in a drainage ditch.
Previous Indications
On the previous landing, the pilot noted that the airplane "shuttered violently" when wheel brakes were applied during the landing roll. After parking, the pilot observed brake fluid "dripping" from the area of the wheel brakes. The pilot contacted the operator of the airplane about the problem. The operator instructed the pilot to ferry the aircraft to Orcas Island for maintenance. In a written report dated November 20, 2003, the operator stated that the pilot advised that only a small amount of brake fluid had leaked.
Examination Findings
Post-accident examination by an NTSB investigator revealed that the brake pads were worn beyond limits, which allowed the caliper seals (O-rings) to unseat, resulting in a loss of brake fluid.