NYC95IA043

During landing roll, the left main gear outer cylinder separated. Metallurgical examination revealed a pre-existing fatigue crack in the schrader valve hole. The hole, including the fatigue region, contained a layer of nickel applied during overhaul as a means of restoring the original tolerances of the part. The cracking initiated from a 0.009-inch-deep gouge or filing mark in the nickel layer. Because of the presence of this and similar nearby marks, the corner failed to comply with the overhaul requirement of a radius pf 0.6 to 0.9 inch at the fatigue initiation location. Also, a bevel found in the nickel layer at this corner, did not comply with the corner requirement. The cylinder had 82,131 hours of total time and 14,951 cycles, and was last overhauled and returned to service September 30, 1988. Also, gouges, and filing marks were determined to be the source of the crack.

On December 18, 1994, at 1429 eastern standard time, a Boeing 747-131, N53116, operated by Trans World Airlines, as Flight 11, had a partial collapse of the left wing landing gear during the landing roll at John F. Kennedy International Airport, Jamaica, New York. Visual meteorological conditions existed. There was no injuries to the occupants. The airplane received minor damage. The flight departed San Juan, Puerto Rico. Flight 11 was operated on an instrument flight plan under 14 CFR Part 121.

The NTSB Accident Report stated:

After a normal touchdown with the right main landing gear first due to a cross wind, and after reverse thrust was applied, the aircraft started listing to the left about 2 degrees, then as aircraft slowed, the aircraft listed up to 4 degrees.

A turn off the active runway 31R was made and the aircraft stopped...

Maintenance advised that the left wing landing gear upper trunnion had separated.

Examination by the FAA revealed the landing gear was fractured approximately 6 inches forward of the rear trunnion where it fastened to the rear wing spar.

According to TWA, the outer cylinder was last overhauled and returned service on September 30, 1988.

The flight data recorder contained information on the last 5 landings. The maximum G load observed was 1.2281 Gs. The maximum G load observed on the incident landing was 1.1156 Gs.

According to the NTSB Metallurgist's Factual Report, 95-68, the fracture originated in the Schrader valve hole with a pre-existing fatigue fracture. Additionally, the report stated:

...The paint in the Schrader valve hole and on the adjacent portions of the trunnion bore surface was stripped away so that the metal surface could be directly examined...The nickel plating along this corner contained a relatively flat bevel that was approximately 0.055 inch wide...The Boeing overhaul manual for the landing gear specifies a radius of 0.06 inch to 0.09 at this location.

The nickel layer also contained gouges or filing marks at the corner between the Schrader valve hole and the trunnion bore surface. The preexisting fracture area appeared to initiate with one of these gouges....