NTSB Identification: WPR11FA158
Nonscheduled 14 CFR Part 135: Air Taxi & Commuter
Accident occurred Thursday, March 10, 2011 in Bakersfield, CA
Probable Cause Approval Date: 05/08/2014
Aircraft: CESSNA 208B, registration: N930FE
Injuries: 1 Uninjured.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The pilot of the cargo flight reported that, after landing at the destination airport, he taxied about 1.9 miles using the customary route toward the assigned cargo unloading area. The airplane turned right and then left without experiencing any anomalies. The pilot then applied full right rudder and brake pressure to negotiate the last 90-degree turn; however, the airplane did not turn as expected and subsequently impacted two trucks and a van. A witness reported that the airplane's taxi speed appeared normal throughout its approach and final turn.
The examination of the accident master brake cylinders and the cylinders from two other airplanes that had reportedly failed revealed several anomalies that could have caused or contributed to the airplane's failure to turn as expected. The examination revealed that the right pedal assembly may interfere with the adjacent floorboard when the brake pedal is compressed to or near the full-internal cylinder travel stop, which may cause an additional stop and limit the overall travel of the cylinder. The examination also revealed that numerous components or items may prevent the master brake cylinders from fully extending after the brakes are released and adequate travel (reduced pressure) when the brakes are subsequently actuated. Additionally, the examination revealed that the brake fluid may bypass the piston O-ring or Stat-O-Seal if parts are damaged or excessively worn. The cylinder manufacturer, in conjunction with the FAA, published Service Bulletin CAB-32-01, Revision 1, to address the noted mechanical anomalies.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The malfunction of a master brake cylinder, which resulted in a loss of braking action and subsequent loss of directional control and collision with three vehicles during taxi. Contributing to the accident was the inappropriate design and manufacture of the master brake cylinders. Full narrative available
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