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HISTORY OF FLIGHT
On July 27, 2009, about 1130 eastern daylight time, a Piper PA-34-200T, N1494X, operated by Air Transport Incorporated, was substantially damaged during landing at South Jersey Regional Airport (VAY), Mount Holly, New Jersey. The commercial pilot and his sole passenger were not injured. Visual meteorological conditions prevailed for the flight, which departed Princeton Airport (39N), Princeton, New Jersey, at approximately 1100. No flight plan was filed for the positioning flight conducted under 14 Code of Federal Regulations Part 91.
According to the pilot, he experienced a problem with the landing gear during several flights which occurred prior to the accident flight. He reported the GEAR UNSAFE light would remain illuminated through an entire cycle of lowering and retracting the landing gear. Additionally, during the flight preceding the accident flight, the GEAR UNSAFE light would not extinguish at all until the landing gear was fully extended.
The pilot advised the director of operations (DO) about the landing gear malfunction and the DO instructed him to notify the director of maintenance (DOM), and have him troubleshoot the landing gear problem. After that was done, the pilot was to fly the airplane to VAY for maintenance to be performed on the right engine.
On the day of the accident, the pilot queried the DOM on the status of the gear discrepancy, and the DOM informed him that he had not looked at it yet, but would do so immediately. The pilot then proceeded to preflight the airplane as the DOM inspected the landing gear. The DOM informed the pilot that he found a dirty switch and cleaned it. He further asked the pilot to advise him whether or not this solved the problem.
The pilot then departed for VAY, and when the landing gear was retracted, once again the gear unsafe light remained illuminated. When the pilot arrived at VAY, he entered the downwind leg of the traffic pattern for runway 26, and proceeded to complete the appropriate checklists. This time when he extended the landing gear, the left main landing gear light would not illuminate. The pilot then retracted and extended the landing gear and the light still did not illuminate. He extended the downwind leg of the traffic pattern, and began to troubleshoot the problem. The pilot retracted and lowered the landing gear several times until finally, after a short" and unusual delay, the left main landing gear light illuminated. The pilot then presumed that the landing gear was down and locked and he reported that he landed uneventfully at VAY.
Although the pilot was able to taxi the airplane to the ramp, a post-flight inspection revealed substantial damage to the wing spar.
According to FAA and pilot records, the pilot held a commercial pilot certificate with ratings for airplane single-engine land, airplane multi-engine land, and instrument airplane. His most recent FAA first-class medical certificate was issued on November 4, 2008. He reported 9,100 total hours of flight experience, and 3,650 hours in the accident airplane make and model.
According to Federal Aviation Administration (FAA) and maintenance records, the airplane was manufactured in 1975.
The airplane's most recent 50 hour service was completed on November 18, 2008. All of the tires were serviced to the correct inflation pressure and the "tire servicing" was found to be "acceptable. At the time of the 50 hour service, the airplane had accumulated 4,172.56 total hours of operation.
Unscheduled maintenance was then performed at 4179.46 hours (6.9 hours after the 50 hour service was accomplished). Both main tires and tubes were replaced and the wheel bearings were cleaned, inspected, and repacked.
A 100-hour inspection was then completed on February 8, 2009. The tires were serviced to the required pressures, the brake and wheel assemblies were inspected and found to be serviceable, and a retraction test of the landing gear was performed in both the normal and emergency modes and the landing gear system performed satisfactorily.
The airplane's most recent 100-hour inspection was completed approximately three months later on May 26, 2009. At the time of the inspection, the airplane had accumulated 4310.0 total hours of operation. The logbook did not list what maintenance actions had been accomplished during the inspection and only stated that an inspection had been performed in accordance with the PA-34-200T, 100 hour/annual inspection program check sheet.
A review of the airplane's Daily Flight Log revealed that no discrepancies or corrective actions had been entered in the log after July 23, 2009.
A weather observation taken at VAY about 24 minutes after the accident recorded, calm winds, visibility 10 miles, few clouds at 2,200 feet, scattered clouds at 4,500 feet, temperature 26 degrees Celsius, dew point 21 degrees Celsius, and an altimeter setting of 29.98 inches of mercury.
According to the Airport Facility Directory, VAY had one runway oriented in a 8/26 configuration. Runway 26 was asphalt, and in good condition. The total length of the runway was 3,911 feet, and its width was 50 feet.
An obstruction existed on the approach end of runway 26 in the form of a tree which was 45 feet in height. It was located 909 feet from the approach end of the runway pavement, and 99 feet left of the centerline. A 15:1 slope was required to clear the tree.
A precision approach path indicator which displayed a 3 degree glide path was also installed on the right side of the runway.
WRECKAGE AND IMPACT INFORMATION
During a post-flight inspection of the airplane by contract maintenance personnel at VAY, it was discovered that the left wing was at a higher angle than normal, the oleo strut was extended farther than the right strut, and the left main landing gear had shifted in its mounts. Further examination revealed that the forward main landing gear support fitting for the left main landing gear truss had failed and that the landing gear had shifted approximately 6 inches from its normal mounting position. It was also discovered, that the lower trailing edge of the main spar that passed through the left main landing gear well, was missing approximately a dime sized piece of metal, the main spar web was deeply gouged, the false spar that was located aft of the left main landing gear had a buckled lower cap, and there was a skin buckle immediately aft of the left main landing gear well.
TESTS AND RESEARCH
Main Landing Gear Support Fittings
The main landing gear support fittings attached to the front and rear wing spars, facing one another. Each support fitting had a spherical bearing, and the main landing gear was raised or lowered by rotating it about the axis between the spherical bearings in the forward and aft main landing gear support fittings.
Examination by the NTSB confirmed that the left forward support fitting had fractured. All of the fracture surfaces on the pieces from the left forward fitting were irregular, with a somewhat granular, faceted appearance, consistent with overstress separations in the castings. Several of the pieces also contained secondary, part-through cracks, consistent with high stresses and some of the fracture surfaces showed evidence of smearing from post fracture contact. No evidence of fatigue cracking or corrosion was found on the fragments from the fractured fitting.
In 1975, Piper Aircraft had superseded their 67041-0, -1, -2 and -3 landing gear support fittings with the 67041-4 landing gear support fitting, which is symmetric and can be used on either the left or the right sides of the airplane. There was no requirement to replace the earlier parts with the redesigned fitting.
Further examination of the fractured fitting indicated that it might have been original to the airplane and in service since 1975, as the fragments from the fractured fitting were slightly thinner than the other fittings. The material appeared to be more consistent with an A356 aluminum/silicon casting alloy than with the Almag 35 aluminum/magnesium alloy called for in the drawings for the current parts. Additionally, review of the manufacturer's drawings revealed that the fractured fitting predated the drawings.
Service Bulletin 956
On March 3, 1992, Piper Aircraft released Service Bulletin 956 which required support fittings on PA-34-200 airplanes to be replaced with fittings having larger diameter (0.312 inch as opposed to 0.250 inch) attachment holes. The Service Bulletin implied that PA-34-200T airplanes (as involved in this accident) already had 0.312-inch diameter attachment holes. Examination of all of the fittings from the accident airplane revealed that the mounting holes were consistent with the larger (0.312 inch) diameter. The only action in Service Bulletin 956 directed specifically at PA-34-200T airplanes was to clean and inspect the fittings using a dye-penetrant method, with any cracked fittings to be replaced.