Sanford, FL, USA
N548C
PIPER PA-46-350P
During landing, as the nose landing gear wheel made contact with the runway, the airplane veered suddenly to the left and exited the runway, incurring substantial damage, before coming to a stop in the adjacent grass area. Examination of the airplane’s nose gear assembly revealed the separation of the nose gear actuator attachment weld tube area (foot) of the motor mount. The metallurgical examination of fractured surface revealed fatigue crack emanating from multiple origins at the exterior of the joint where the attachment foot was welded to the support tube. The motor mount was a new design from the manufacturer which was to eliminate the concerns of fatigue separation of the weld in the foot area which was a problem with the old design motor mounts. The airplane had an annual inspection 36 flight hours prior to the accident. The new design motor mount does not have any specific inspection guidance during scheduled maintenance for identifying fatigue cracking in the actuator attach points. The old design motor mounts had detailed inspection instructions to detect fatigue cracking in the welds of the foot areas.
On August 16, 2009, at 1130 eastern daylight time, a Piper, PA-46-350P, N548C, had the nose landing gear collapse during landing at the Orlando-Sanford International Airport, Orlando, Florida. The pilot and passenger were not injured, and the airplane incurred substantial damage. Visual meteorological conditions prevailed and no flight plan was filed. The airplane was operated by a private individual, under the provisions of Title 14 Code of Federal Regulations Part 91, as a personal flight. The pilot stated to the responding Federal Aviation Administration (FAA) inspector that he performed a visual approach to runway 9 left; the wind was from the 140 degrees and at 10 knots (kts). He was cleared to land by the airport traffic controller and confirmed the three green lights for down and locked on the landing gear position. The main wheels touched down at an estimated speed of 85 kts with full flaps extended. As the nose wheel touched the runway, immediately and without warning the nose of the airplane veered left. The airplane swerved left, off the runway, skidding onto the grass. The propeller struck the ground before the airplane came to a stop. The pilot shut down the engine and secured the airplane before he and his passenger disembarked the airplane. A post recovery examination of the airplane revealed the right side welded section, on the engine mount, where the nose gear actuator attaches, had separated. The component was removed and retained by the National Transportation Safety Board (NTSB) for further analysis. NTSB materials laboratory examination of the fractured surface revealed a fatigue crack emanating from multiple origins at the exterior of the joint where the attachment foot was welded to the support tube. At the time of the accident, the airplane was 8 years old and had accumulated 711 flight hours with 878 cycles since new. The accident airplane was a Piper PA-46-350P, Malibu Mirage, serial number 4636322, manufactured in 2001, and issued a Standard Airworthiness Certificate in the Normal Category. The airplane was powered by a Textron Lycoming TIO-540-AE2A, 350 horse powered engine. The airplane was under the Piper Aircraft Inc., Piper Malibu Maintenance Program. The airplane’s last annual inspection was performed on February 16, 2009, at 675 total hours. The last unscheduled maintenance performed was on July 27, 2009, at 697 total hours. The Piper Aircraft Inc., Maintenance Inspection, for the PA-46 350P, 100 Hour interval Inspection, item 40, instructs to “inspect engine mount for cracks, corrosion and loose mounting bolts (See 100 hour Engine Mount Inspection, 71-20-00)”, which calls out for Item 1, Engine Mount, A. Inspection, (1) 100 Hour “In Serial Numbers 4636001 through 4636319 with the original factory-installed engine mount, each 100 hours time-in-service.” The 100 hour inspection is inclusive of the annual inspection. The steps instruct to remove the paint from the weld areas for the actuator nose landing gear attachment section (foot) and to conduct a visual, and to use a” liquid penetrant inspection”, inspection for cracks. The motor mount crack inspection was not applicable to the accident airplane by serial number (4636322). The airplane was manufactured with a newly designed motor mount. The airplane’s manufacturer has issued a series of service bulletins (SB) addressing the inspection guidance on the motor mount cracking concerns with the older design motor mount, which are repetitive until a new design motor mount is installed. The manufacturer has developed the new motor mount to eliminate the cracking concerns of the older design motor mounts. The new design motor mount does not have any special inspection guide lines or SB for specific inspection instruction for the area of known cracking. The NTSB has investigated two accidents involving failure of the nose gear actuator attach foot and one case in which maintenance discovered failure of the attach foot on newly designed Piper PA-46-350P motor mounts. The investigations found fatigue cracks of the weld joints at the nose gear actuator attachment foot support tube locations.
The fatigue cracking at the point the nose landing gear actuator attaches to the mount resulting in separation of the actuator and partial collapse of the nose landing gear. Contributing to the accident was the lack of specific inspection guidance for scheduled maintenance to find and/or identify fatigue cracking in the welded actuator attach points of the newly designed mounts.
Source: NTSB Aviation Accident Database
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