Tuesday, August 9, 2011
There are times when the risk of not stopping should stop you from going
A Cessna 172S overran a taxiway at the Anacortes Airport, Anacortes, Wash., and was substantially damaged. The pilot and passenger were uninjured. The destination had been East Sound, Wash.
The pilot told an NTSB investigator that he experienced complete brake failure while taxiing for takeoff. The pilot said that he applied brakes as the airplane neared the end of the inclined taxiway, but it continued off the end of the taxiway. It eventually came to rest, nose down, in a drainage ditch.
The pilot reported that on the previous landing, the airplane "shuttered violently" when he applied brakes during the landing roll. He stated that after parking the airplane, he noticed brake fluid "dripping" from the area of the wheel brakes. He said he contacted the operator of the airplane who instructed the pilot to "...ferry the aircraft back for maintenance." The operator told the NTSB the pilot advised him that only a small amount of brake fluid had leaked from the system.
Examination of the brake components by an investigator revealed that the pads were worn beyond limits, which allowed the caliper seals (O-ring) to unseat, resulting in a loss of brake fluid.
The NTSB determined that the probable cause of this accident was the pilot attempting to taxi the airplane with a known system deficiency. Factors include worn brakes and a drainage ditch.
A Piper PA-32-300 went off the right side of runway 36, and struck a part of the VASI light system while landing at Canton-Plymouth Airport, Plymouth, Mich. The aircraft was arriving from Sparta, Mich. The pilot and passenger weren't injured.
The pilot reported that he applied braking, but the right brake wasn't working. The pilot attempted to slow the airplane by using left braking and right rudder. The pilot reported that the aircraft then veered to the right and went off the runway. The left wing hit the VASI lights, and the airplane caught fire. The pilot and his passenger got out, and the fire was put out by the pilot and airport staff.
The pilot reported that he had maintenance performed on the brakes twice in the few weeks before the accident flight. The mechanic bled the lines and added fluid. After the accident, a seal in the brake master cylinder was found to be defective, and this allowed the fluid level to be low, and air to enter the brake lines.
The NTSB determined that the probable cause of this accident was the pilot not maintaining directional control during landing, and the inoperative right main landing gear brake. Contributing factors were the failed brake master cylinder seal, resulting in a hydraulic leak, the inadequate preflight by the pilot, the fuel fire, and the pilot intentionally operating the airplane with a known brake-system problem.
Peter Katz is editor and publisher of NTSB Reporter, an independent monthly update on aircraft accident investigations and other news concerning the National Transportation Safety Board. To subscribe, write to: NTSB Reporter, Subscription Dept., P.O. Box 831, White Plains, NY 10602-0831.
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