Fort Pierce, FL, USA
N501DR
Cessna 501
During the landing roll, the pilot was unable to maintain directional control and the airplane swerved side-to side before going off the right side of the runway. The pilot said overhauled brake assemblies had been installed before the accident. He complained that the brakes felt "spongy" and the pedals went "almost to the floor, requiring two or three additional pumps for a hard pedal." He was told that this was "normal" since the airplane was not equipped with power brakes or anti-skid. The brakes were removed and sent to the overhaul facility. They found that both brake assemblies each had one return mechanism binding. The return mechanism had a self adjusting friction bushing meant to slip along the return pin at a predetermined spring pressure. As pressure was applied to the brake, the pressure plate extended toward the number one rotor, pulling the return pins through the swage and tube assemblies and compressing the return springs. Although the swage should move through the tube, one swage on each brake was not moving freely. The brake travel went further than normal because "normal travel" was never set.
On February 11, 2006, approximately 2115 eastern standard time, a Cessna 501, N501DR, registered to Eagle Aviation LLC, and piloted by a private pilot, was substantially damaged when directional control was lost during landing at St. Lucie County International Airport, Fort Pierce, Florida. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 CFR Part 91, and an Instrument flight rules (IFR) flight plan had been filed and activated. The pilot and passenger on board the airplane were not injured. The cross-country flight was originated from Columbia Metropolitan Airport, Columbia, South Carolina, approximately 1930 and was en route to Fort Pierce. According to the pilot's accident report, the flight proceeded to Fort Pierce without incident, and he executed an instrument landing system (ILS) approach to runway 09. He said he flew the approach at an airspeed of Vref plus 15 to 20 knots with full flaps extended, then slowed to approximately 95 knots. The airplane touched down within 300 to 500 feet of the runway threshold. During the landing roll, he could not maintain directional control of the airplane which was going side to side. He attempted to correct the side-to-side motion with rudder control input. The airplane departed the right side of the runway and came to rest on grass approximately 500 feet from the south edge of the runway. According to an FAA inspector who went to the scene, rubber residue found on the runway was indicative that the airplane was yawing to the right. The tire marks were associated with the nose and right main landing gear tires. The right main tire had a flat spot, and the nose gear fork was fractured. The pilot submitted an addendum statement in which he said four months before the accident, an Oklahoma City, Oklahoma, maintenance facility installed overhauled brake assemblies on the left and right main landing gears, and bled the brakes. After the work was completed, the pilot told them that the brake pedals felt "spongy" and went "almost to the floor, requiring two or three additional pumps for a hard pedal." Maintenance personnel bled the brakes a second time, but there was no change. They told the pilot that this was "normal" since the airplane was not equipped with power brakes or anti-skid. Maintenance personnel in Wilmington, Delaware, the pilot's home base, and Fort Pierce, Florida, after repairs were made, also bled the brakes and reiterated that the sponginess was "normal." After the accident and after repairs had been made to the airplane, the pilot assisted a Wilmington A&P mechanic in bleeding the brakes. Again, there was no change in pedal "feel." Examination of the brake assemblies, however, revealed the amount of pedal travel appeared to be greater than normal. The brakes were removed and sent to the overhaul company. In the maintenance logbook, they wrote: "Both brake assemblies had one return mechanism binding. The return mechanism has a self adjusting friction bushing. This bushing is meant to slip along the return pin as a predetermined spring pressure. As pressure is applied to the brake, the pressure plate is extended toward the number one rotor pulling the return pins through the swage and tube assemblies and compressing the return springs. The swage should move through the tube throughout the life of the brake. However, one swage on each brake was not freely moving along the pin and tube. Therefore the brake travel was further than it should have been due to the normal travel never having been set. We have completely resealed these housings and replaced all of the return mechanisms with fully functioning ones. We have repeatedly tested the units and applied operating pressure to the housing to ensure that normal brake travel has been achieved and set, and that the friction (or swage and tube) assemblies are free of binding and functioning properly."
mechanical binding of the normal brake system, rendering directional control impossible. Contributing factors were the improper overhaul, inadequate quality control procedures by the overhaul facility, and the rough terrain.
Source: NTSB Aviation Accident Database
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