Franklin, NC, USA
N555GK
PIPER PA-31-350
The pilot reported that, during the preflight inspection, he checked both the left and right brake reservoirs for proper servicing, and he found that they were ready for flight. During the landing roll, the pilot applied the left and right brake pedals; however, the left brake did not respond, and the airplane departed the right side of the runway. Postaccident examination of the airplane revealed that there was a hydraulic fluid leak in the left main landing gear brake line. Further examination revealed that the brake line failed due to a fatigue crack that had propagated through the cross-section of the brake line, which resulted in the hydraulic fluid leak. The fatigue cracking was likely due to the detachment of the swaged compression sleeve and nut from the brake line due to exfoliation corrosion. The exfoliation corrosion likely resulted from or was exacerbated by consistent introduction of water and contact between two the different metals in the aluminum sleeve and the stainless steel brake line. A review of the airplane's maintenance records revealed that the airplane's last annual inspection occurred about 3 months before the accident. According to the mechanic who performed the inspection, he performed a visual inspection of the brake system for looseness, leakage, and corrosion and physically checked the tightness of the "B" nut at the brake caliper in accordance with the 100-hour phase checklist; however, he did not note any problems with the left brake line.
HISTORY OF FLIGHTOn October 17, 2013 about 1230 eastern daylight time, a Piper PA-31-350, N555GK, operated by a private individual, was substantially damaged while landing at Macon County Airport (1A5) Franklin, North Carolina. The airline transport pilot and seven passengers were not injured. The flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Instrument meteorological conditions prevailed and an instrument flight plan was filed for the flight that departed Flagler County Airport (XFL) Palm Coast, Florida at 1100. The pilot stated that during the pre-flight inspection of the airplane, both the left and right brake reservoirs were checked for proper servicing and were found to be ready for flight. While landing at 1A5, the pilot selected the gear to the "DOWN" position and pumped the brakes to confirm they were functioning normally before landing. As the airplane touched down, he applied the brakes, but the "left brake went to the floor." The pilot utilized left rudder and minimal usage of the right brake to stay on runway centerline. At 20 knots, the right brake "locked up", the airplane departed the right side of the runway, and collided with a ditch. The hobbs meter showed 7,754 hours at the time of the accident. The Federal Aviation Administration did not conduct an on-scene examination of the airplane. Photographs taken by the 1A5 airport manager revealed substantial damage to the left winglet and to the left wing spar. The airport manager reported a pool of red fluid on the ground beneath the left main landing gear that was consistent with aviation brake fluid, and that the left wheel brake reservoir was empty. There was also red fluid seeping from the "B" nut fitting that tightens the hydraulic brake line to the brake caliper. A 10 year historical review of the FAA Service Difficulty Report database and Piper service bulletins did not reveal any brake line failures or modifications. A section of the left brake line with the "B" nut and ferrule fitting attached was removed and sent to the National Transportation Safety Board Materials Laboratory for further examination. PERSONNEL INFORMATIONFAA information indicated that the pilot held an airline transport certificate with ratings for multi-engine land, single engine sea. The pilot also held a flight instructor certificate with ratings for airplane multi-engine, instrument airplane, and instrument helicopter. The pilot reported a total flight experience of 30,000 hours, including 3,000 hours in the accident airplane make and model. His most recent flight review was completed June 26, 2013, and his most recent FAA second-class medical certificate was issued on September 18, 2013. AIRCRAFT INFORMATIONThe twin-engine, retractable-gear, low wing, all metal multi-engine powered airplane, serial number 31-7405456, was manufactured in 1974. It was powered by two Lycoming LTI0-540, 350-horsepower engines. A review of the aircraft maintenance records revealed the airplane's most recent annual inspection was completed on July 9, 2013, at an aircraft total time of 7552.2 hours, which was 22 hours prior to the accident. According to an airframe logbook entry dated July 9, 2013, "placed aircraft on jacks and performed landing gear functional and emergency operational checks. Lubricated landing gear system." METEOROLOGICAL INFORMATIONThe 1235 automated weather observation at 1A5 included winds calm, scattered clouds 800 feet, broken clouds 1700 feet, overcast clouds 3800 feet, visibility 7 statute miles, temperature 17 degrees C, dew point 16 degrees C, and an altimeter setting of 29.98 inches of mercury. AIRPORT INFORMATIONThe twin-engine, retractable-gear, low wing, all metal multi-engine powered airplane, serial number 31-7405456, was manufactured in 1974. It was powered by two Lycoming LTI0-540, 350-horsepower engines. A review of the aircraft maintenance records revealed the airplane's most recent annual inspection was completed on July 9, 2013, at an aircraft total time of 7552.2 hours, which was 22 hours prior to the accident. According to an airframe logbook entry dated July 9, 2013, "placed aircraft on jacks and performed landing gear functional and emergency operational checks. Lubricated landing gear system." ADDITIONAL INFORMATIONBrake System The airplane was equipped with a hydraulic fluid braking system that included two independent wheel brakes actuated by two separate brake master cylinders, one each for the left and right brake. A hydraulic fluid reservoir, separate from the main hydraulic system, supplied fluid to each cylinder. From the cylinders, hydraulic fluid was routed through hoses and lines to a parking brake valve, located in the forward cabin, through the cabin and wings and to the left and right main landing gear brake assemblies. The brake lines were composed of type 304 stainless steel and attached to a brake caliper via an aluminum swaged sleeve that was compressed behind a nut. Depression of the brake pedal actuated a piston rod in the master cylinder, which applied hydraulic pressure to the brake caliper pistons. Release of the pedal permitted the piston rod to be back-driven by a spring, which in turn released brake pressure at the wheel. Inspection and Maintenance Information According to the airplane's mechanic, he followed the PA-31-350 100 hour phase inspection checklist during the airplane's last annual inspection. He performed a visual inspection for leakage and corrosion and physically checked the tightness of the "B" nut at the brake caliper. The airplane owner reported that the landing gear was cleaned about twice a month with a degreaser. The landing gear was then rinsed with soap and water after each chemical application. Review of the make and model airplane preflight inspection section of the pilot's operating handbook stated, "Left Wing – (12) Landing gear – condition, strut inflation, micro switches, tires, brakes, gear door." Materials Laboratory The left brake line and "B" nut were sent to the NTSB Materials Laboratory for examination. Metallurgical examination revealed fatigue striations at the end of the brake line consistent with fatigue cracking. The swaged sleeve exhibited intergranular cracking consistent with exfoliation corrosion. Chemical examination of the brake line tube revealed that it was consistent with manufacturer's specifications. The composition of the aluminum 2024 swaged sleeve was also consistent with manufacturer's specification.
The failure of the left main landing gear brake line during landing due to the loss of hydraulic fluid. Contributing to the accident was a fatigue crack through the brake line that had formed due to contact with a swaged sleeve as a result of exfoliation corrosion.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
