JAMAICA, NY, USA
N244AA
McDonnell Douglas MD-80
The flight was inbound to land, when the flight crew observed an unsafe nose gear indication. The crew was unable to confirm that the gear was down, and diverted to Runway 31R at JFK. The airplane landed on the runway, with the nose gear retracted, and an emergency evacuation was performed. Examination of the wreckage revealed the nose landing gear upper lock link was fractured into two pieces. The linkage jammed against the shock strut structure, preventing extension of the strut. According to the airplane manufacturer, the nose landing gear upper lock link failed due to fatigue. It was made from aluminum plating. Originally, all the links were made from forged aluminum. Then, the company used plated aluminum because it weighed less. Although both types of lock links were of the same strength, the aluminum plating fatigued sooner than the forged links. After the accident, the company replaced all aluminum plated upper lock links with forged ones.
On October 28, 1996, about 2231 Eastern Standard Time, American Airlines flight 346, a McDonnell Douglas MD-80, N244AA, sustained minor damage while landing with the nose gear retracted at John F. Kennedy International Airport (JFK), Jamaica, New York. Visual meteorological conditions prevailed for the flight that departed Chicago O'Hare International Airport, Chicago, Illinois; destined for LaGuardia Airport (LGA), Flushing, New York. There were 93 occupants on board; 1 passenger received serious injuries, and 2 passengers received minor injuries. An instrument flight rules flight plan was filed for the air carrier flight conducted under 14 CFR Part 121. The flight was inbound to Runway 31 at LGA when the flight crew observed an unsafe nose gear indication. A low approach was made at LGA for ground personnel to visually determine the nose gear position. They could not confirm the nose gear was down and locked. The flight crew decided to divert to JFK, where a landing was made on Runway 31R, and a subsequent emergency evacuation was performed. Examination of the wreckage revealed that the nose landing gear upper lock link (P/N 3914464-503) was fractured into two pieces. The linkage jammed against the shock strut structure, preventing extension of the strut. According to an analysis by McDonnell Douglas, the upper lock link failed because it was made from a substitute material (aluminum plate) in place of aluminum forging. The aluminum plate had a lower allowable fatigue in comparison to aluminum forging. A representative from McDonnell Douglas stated that the original aluminum forging was replaced by aluminum plating because of lighter weight. After the accident, the company replaced all aluminum plated links with aluminum forging. American Airlines conducted a fleet wide inspection, and found one other cracked lock link.
Failure of the nose landing gear upper lock link.
Source: NTSB Aviation Accident Database
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