Tuesday, August 9, 2011
There are times when the risk of not stopping should stop you from going
The pilot told an NTSB investigator that during the taxi, he applied a little extra power and right brake to maintain a straight taxi. By the time the fire department arrived, the right wing had collapsed.
The pilot reported that two weeks before the accident, he complained about the pulling to the left, and maintenance personnel found that the left-brake cylinder and assembly had been leaking fluid. They repaired the brake assembly, and returned the airplane to service.
A squawk-sheet entry from three days prior to the accident noted that the airplane pulled hard left, and was "not normal."
The Pilot's Operating Handbook advised pilots that excessive braking could result in overheated or damaged brakes, which could result in brake-system malfunction or failure.
The NTSB determined that the probable cause of this accident was the pilot's excessive braking during taxi that resulted in the right brake overheating and a fire. A factor in the accident was the pilot's continued operation with known deficiencies.
A tricycle-gear Piper PA-22-135 overran runway 28 at the Emmett Municipal Airport, Emmett, Idaho. Neither the pilot nor passenger was injured. The flight originated from Emmett approximately 45 minutes earlier. The pilot reported that he conducted the engine run-up while holding the hand brake. He then departed, remained in the pattern and executed two touch-and-goes to runway 28. He didn't use brakes during these landings. The pilot left the pattern and later returned.
The airplane touched down at approximately 50 miles per hour, and as the speed bled off, the pilot applied the hand brake. He stated that, "...I immediately realized there were no brakes. At that point I pumped the hand brake several times in hopes of building up some pressure. This did not work...," and, "...I continued to hold the brake handle all the way back in the stopping position. I did not feel any resistance..." The passenger reported that he "...observed the pilot apply and recycle the brakes at least twice without noticeable braking or effect..."
The pilot maintained the aircraft on the centerline, and rolled out straight ahead, exiting the upwind end of the runway at about 10 miles per hour. The aircraft then rolled down a gravel embankment and into a ditch. Runway 28 was 3,250 feet long by 50 feet wide. "
A local mechanic/pilot who had owned a Piper PA-22 for 40 years at the Emmett Airport was interviewed, and reported that the PA-22's brake system is highly sensitive to temperature changes. He said that when the system is fully serviced under cool conditions, and then allowed to increase in temperature, the system will lock up. A small amount of fluid has to be bled in order to release the brakes. Conversely, when the system is taken from a warm temperature to a cold temperature, the fluid contracts and the brakes become loose requiring the addition of brake fluid. The mechanic/pilot indicated that pilots new to the aircraft often aren't familiar with this behavior. The accident pilot reported a total of 118 hours of flight experience with 15.7 hours in the PA-22.
The NTSB determined that the probable cause of this accident was brake failure as a result of inadequate hydraulic fluid. Contributing factors were the pilot's overall lack of experience in the aircraft make/model, the cold, soaked brake system due to the low temperatures, and the embankment and ditch.
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