Fort Wayne, IN, USA
N4185L
Piper PA-46-500TP
The private pilot reported that during landing at the conclusion of a personal flight, the airplane turned abruptly to the left and went off the side of the runway. The landing gear encountered muddy terrain, and the nose landing gear collapsed. Inspection of the nose gear support structure by an NTSB materials engineer disclosed that the right nose gear attachment foot had fractured at the right engine support mount due to fatigue failure. The airframe manufacturer had an applicable service bulletin that recommended increased inspection of the failed area because of a history of cracking. The service bulletin had reportedly been complied with about 18 service hours prior to the nose gear failure, but portions of the failed component had not been completely stripped of paint as recommended to check for cracking. The existing service bulletin was superseded with another service bulletin that reduced the inspection intervals. The manufacturer has also developed a replacement part that, when installed, will end the repetitive inspection requirement of the failed component. Additionally, the old-style component is no longer available as a replacement part.
HISTORY OF FLIGHT On November 18, 2006, about 1100 eastern standard time, a Piper PA-46-500TP N4185L, piloted by a private pilot, sustained minor damage when the nose gear collapsed during landing on runway 5 (3,110 feet by 100 feet, asphalt) at the Smith Field Airport (SMD), near Fort Wayne, Indiana. The personal flight was operating under 14 CFR Part 91. Visual meteorological conditions prevailed at the time of the accident. An instrument flight plan was on file and was activated. The pilot reported no injuries. The flight originated from the Monroe County Airport (BMG), near Bloomington, Indiana, about 1000 and was destined for SMD. The pilot stated: At approximately [1000] on Saturday, November 18, 2006, I took off from Bloomington, Indiana Airport (BGM). Upon take-off, I put the gear lever in the up position. The landing gear circuit breaker popped. I put the gear lever back in the down position and reset the landing gear circuit breaker. Once this was set, I positioned the landing gear handle in the up position. The landing gear seemed to retract with no problem. At approximately [1100], I landed at the Smithfield Fort Wayne Airport (SMD). It was a normal visual landing. Due to the problems with retracting the gear after take-off, I paid particularly close attention to the gear being extended in preparation for landing. I got three green lights, and did not notice anything unusual regarding the extension of the gear. The two rear wheels touched first, and then the nose gear touched down. Upon the nose wheel gear touching down, the aircraft took an immediate left. Whereupon I applied full right rudder. The aircraft did not respond. It left the runway into the sod on the left side of the runway which was muddy due to recent rain. At that point, the front nose gear collapsed and the prop struck the ground. The aircraft then came to a complete stop. I shut down all the systems, pulled the fuel control knob to the off position, and evacuated the aircraft. PERSONNEL INFORMATION The pilot held a commercial pilot certificate with single-engine land and instrument airplane ratings. The pilot certificate indicated he held private pilot privileges with a rotorcraft helicopter rating and sport pilot privileges with a powered parachute land rating. The pilot held a second-class medical certificate, with a limitation for corrective lenses. The pilot reported that he had accumulated a total of 4,672 flight hours of which 1,128.5 hours were accumulated in the same make and model as the accident airplane. In the 90 days preceding the accident, the pilot had accumulated 40 hours in the same make and model as the accident. The pilot's most recent flight review was accomplished on November 15, 2006, in the accident airplane. AIRCRAFT INFORMATION N4185L, a 2000 model year, PA-46-500TP, serial number 4697025, was an all-metal airplane with semimonocoque fuselage and empennage construction. A 500-horsepower Pratt and Whitney Canada PT6A-42A turbopropeller engine, serial number PCE-RM0028, powered the airplane. The pilot reported that the last annual inspection was conducted on November 14, 2006. A logbook endorsement showed that the airplane Hobbs meter and total time was 1,110.5 hours and that the engine mount inspection indicated in Service Bulletin (SB) 1154A was complied with. The pilot reported the airplane's total time at the time of the accident was 1,128.5 hours. The airplane's flight manual description of the landing gear, in part, stated: The aircraft is equipped with hydraulically operated, fully retractable, tricycle landing gear. Locking-type actuators are used for main and nose gears. The actuator assembly provides mechanical gear-down locking at the fully extended position and is hydraulically unlocked. The actuator also acts as the gear brace in the extended position. SB 1154A, in part, stated: 1. Remove the nose gear hydraulic actuator and the nose gear assembly from the engine mount per the Aircraft Maintenance Manual, Chapter 32-20-00. Clean the engine mount actuator attach feet area including tube welds ... . Clean the inboard sides of the mount within 2 inches of the nose gear attach points ... . 2. Strip the area to be inspected using a commercially available chemical paint stripper, such as Cee-Bee E-2012 or E-2060 paint stripper or an equivalent, taking care only to remove paint and primer from the inspection area or remove the Dinitrol AV8, if the paint was previously removed and covered with Dinitrol AV8. 3. Visually inspect the engine mount welds and the tubes ... for cracks. 4. Perform a 'liquid penetrant inspection' of the engine mount in specified areas for cracks per AC 43.13-1B, Change 1, Chapter 5, Section 5. 5. Inspect the entire length of each weld on the attach feet. A mirror will be required to inspect the upper surface of the attach feet and associated tubes. If a crack appears, the engine mount must be replaced before further flight ... . 6. If no cracks are found, clean the feet and apply Dinitrol AV8, Piper P/N [part number] 89500-800, to the area where paint was removed. If cracks are found, refer to PART II of this service bulletin. ... 8. Make an appropriate logbook entry of compliance with this Service Bulletin for each repetitive inspection. METEOROLOGICAL INFORMATION At 1054, the reported weather at the Fort Wayne International Airport, near Fort Wayne, Indiana, was: Wind 350 degrees at 3 knots: visibility 6 statute miles; sky condition overcast 3,000 feet. WRECKAGE AND IMPACT INFORMATION The airplane was recovered to a hangar at a fixed base operator (FBO) at SMD. Pictures revealed that the right nose landing gear actuator attachment foot had separated from the engine mount. Pictures showed that the tubes and welds that were attached to the actuator attach feet were stripped of paint. The tubes within two inches of the nose gear attach points were painted. The airplane's Hobbs meter indicated 1,131.0 hours at the FBO. The airplane's engine mount was shipped to the manufacturer and was reviewed with four similar engine mounts from other airplane accidents and incidents under the supervision of a National Transportation Safety Board (NTSB) structural engineer. The NTSB report numbers for the other accidents and incidents were DEN07LA030, MIA07LA038, SEA07IA058, and LAX05LA116. TESTS AND RESEARCH On March 21, 2007, the NTSB structural engineer examined the engine mounts at the Piper Aircraft Inc. facilities in Vero Beach, Florida. Three mounts were bent near the nose gear actuator attach feet, and no cracks were noted. Two mounts, including this incident's mount, displayed separations at the nose gear actuator attach feet. This incident's mount was sent to the NTSB Materials Laboratory for further examination. A NTSB materials research engineer examined the mount and produced Materials Laboratory Factual Report number 07-113. The report, in part, stated: The engine mount is generally of a welded tubular construction. The aft end of the nose landing gear actuator is bolted between two attachment feet (left and right) at the aft end of the engine mount structure. The right attachment foot was fractured, and the two tubes supporting the left attachment foot were bent, with the left attachment foot rotated aft and up by an angle of approximately 45 degrees. The nose gear actuator attachment bolt was bent at an angle of between 5 and 10 degrees. ... The upper aft part of the right nose gear actuator attachment foot fractured away from the rest of the engine mount. ... The fracture at the forward edge of the foot showed relatively smooth features on flat planes with curved crack arrest markings consistent with fatigue cracking. The fatigue cracking initiated on multiple planes within the weld between the forward support tube and the right attachment foot. The fatigue cracking was evident over an arc of approximately 75 degrees; at its deepest penetration, the fatigue crack had propagated through approximately 80 percent of the estimated 0.07-inch wall thickness of the foot. Along the bottom of the attachment foot, the fracture passed through the wall of the attachment foot (generally along a weld within the attachment foot itself) and through the wall of the bottom support tube. No cracks were observed in the joint where the left attachment foot was joined to the support tubes. ADDITIONAL INFORMATION On March 28, 2007, Piper issued SB 1154B, Engine Mount Inspection. According to the SB details, SB 1154B superseded SB 1154A and SB 1154. SB 1154B shortened the repetitive inspection requirement for the engine mount from 100 hours to 50 hours. The SB stated that Piper has developed corrective action to eliminate the on-going inspection of the mount. A new mount with improved service life has been developed, P/N 102460-036. The original mount will no longer be available as a service part replacement. If the original mount P/N 102460-002 is replaced with the new mount, the repetitive inspection will no longer be applicable. The new engine mount, P/N 102460-036, incorporated a one-piece design at the actuator attach point, eliminating the original two-piece actuator attachment feet design.
The fatigue failure/separation of the engine mount's nose gear actuator attachment foot, and the manufacturer's inadequate engine mount/nose gear actuator attachment design.
Source: NTSB Aviation Accident Database
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