History of Flight
On October 17, 2013, about 1230 eastern daylight time, a Piper PA-31-350, registration N555GK, operated by a private individual, was substantially damaged while landing at Macon County Airport (1A5) in Franklin, North Carolina. The airline transport pilot and seven passengers were not injured. The flight was conducted under 14 Code of Federal Regulations Part 91, with instrument meteorological conditions prevailing and an instrument flight plan filed. The flight departed Flagler County Airport (XFL) in Palm Coast, Florida, at 1100.
During the pre-flight inspection, the pilot checked both brake reservoirs and found them serviced and ready for flight. While landing, the pilot selected the landing gear down and pumped the brakes to confirm normal function. On touchdown, he applied brakes, but the left brake pedal went to the floor. The pilot used left rudder and minimal right brake to stay on the runway centerline. At 20 knots, the right brake locked up, causing the airplane to depart the right side of the runway and collide with a ditch.
The hobbs meter indicated 7,754 hours at the time of the accident.
The Federal Aviation Administration did not conduct an on-scene examination. Photographs taken by the airport manager revealed substantial damage to the left winglet and left wing spar. A pool of red fluid, consistent with aviation brake fluid, was found beneath the left main landing gear, and the left wheel brake reservoir was empty. Red fluid was also seeping from the "B" nut fitting that tightens the hydraulic brake line to the brake caliper.
A 10-year review of the FAA Service Difficulty Report database and Piper service bulletins revealed no prior brake line failures or modifications. A section of the left brake line with the "B" nut and ferrule fitting was sent to the NTSB Materials Laboratory for examination.
Personnel Information
The pilot held an airline transport certificate with ratings for multi-engine land and single-engine sea, and a flight instructor certificate with ratings for airplane multi-engine, instrument airplane, and instrument helicopter. He reported 30,000 total flight hours, including 3,000 hours in the accident airplane make and model. His most recent flight review was on June 26, 2013, and his most recent FAA second-class medical certificate was issued on September 18, 2013.
Aircraft Information
The twin-engine, retractable-gear, low-wing, all-metal airplane, serial number 31-7405456, was manufactured in 1974. It was powered by two Lycoming LTI0-540, 350-horsepower engines. The most recent annual inspection was completed on July 9, 2013, at an aircraft total time of 7,552.2 hours, which was 22 hours prior to the accident. An airframe logbook entry from that date noted: "placed aircraft on jacks and performed landing gear functional and emergency operational checks. Lubricated landing gear system."
Meteorological Information
At 1235, the automated weather observation at 1A5 reported winds calm, scattered clouds at 800 feet, broken clouds at 1,700 feet, overcast clouds at 3,800 feet, visibility 7 statute miles, temperature 17°C, dew point 16°C, and an altimeter setting of 29.98 inches of mercury.
Additional Information
The airplane had a hydraulic fluid braking system with two independent wheel brakes, each actuated by separate master cylinders. A fluid reservoir supplied each cylinder. Hydraulic fluid was routed through hoses and lines to a parking brake valve, then through the cabin and wings to the brake assemblies. The brake lines were type 304 stainless steel, attached to the caliper via an aluminum swaged sleeve compressed behind a nut. Pedal depression actuated a piston rod in the master cylinder, applying pressure to the brake caliper pistons; release allowed a spring to back-drive the rod.
According to the airplane's mechanic, the last annual inspection followed the PA-31-350 100-hour phase checklist, including visual inspection for leakage and corrosion and checking the tightness of the "B" nut at the brake caliper. The owner reported cleaning the landing gear about twice per month with degreaser, followed by soap and water rinse.
The pilot's operating handbook preflight inspection section for the left wing included checking landing gear condition, strut inflation, micro switches, tires, brakes, and gear door.
Metallurgical examination of the left brake line and "B" nut at the NTSB Materials Laboratory revealed fatigue striations at the end of the brake line consistent with fatigue cracking. The swaged sleeve showed intergranular cracking consistent with exfoliation corrosion. Chemical examination confirmed the brake line tube and aluminum 2024 swaged sleeve compositions were consistent with manufacturer specifications.