NYC95IA106

The DC-8-71 landed, and then on rollout, it settled to the right, allowing the #3 and #4 engine cowlings to settle onto the runway. An investigation revealed the right main landing gear cylinder had failed circumferentially, just above the retract cylinder attach point. The landing gear then rotated and collapsed rearward. Metallurgical examination of the landing gear cylinder revealed preexisting cracks on the inside surface. The cause of the cracking was not verified.

On May 13, 1995, at 0029 eastern daylight time, a Douglas DC-8-71, N707UP, operated by United Parcel Service as flight 559, received minor damage while landing at Standiford Field, Louisville, Kentucky. The three airline tansport pilots were not injured. Visual meteorological conditions prevailed, and the flight, which had departed from Minneapolis, Minnesota, at 2304, was operated on an instrument flight rules (IFR) flight plan, under 14 CFR Part 121.

In the NTSB Report, the flight crew stated:

...All normal checklists were completed with the landing gear confirmed "down - 3 green". A stabilized approach was flown to touchdown on speed and a normal landing was made.

Shortly after the spoilers deployed, the aircraft began shuddering and settled to the right. Full opposite aileron could not bring the wing back to level. Engine fire warnings sounded for engines #3 and #4 as we continued down the runway. Fire handles were pulled and the fire warning lights extinguished. Aircraft came to a full stop and the tower was advised of our emergency situation.

Accomplished shutdown. Did not fire bottles. Smoke started filling the cockpit. We then made an emergency evacuation using the escape slide....

Examination of the airplane disclosed that the outer cylinder of the right main landing gear had failed circumferentially, approximately 3 inches above the landing gear retract cylinder attach point. The landing gear wheels swiveled and one tire was blown. When the landing gear collapsed, the number 3 and 4 engines cowlings contacted the runway.

The failed portions of the landing gear were forwarded to the NTSB Laboratory for examination. According to the report by the Safety Board Metallurgist:

...Initial visual examination of the as-received fracture faces uncovered chevron and river markings emanating from the forward area of the cylinder where the side brace lugs joined the main body of the cylinder...The deepest crack penetrated about 0.2 inches into the wall of the cylinder. When combined, the area showing crack arrest positions covered about 3 inches of the cylinder's ID circumference. The remaining fracture outside of the crack positions appeared typical of overstress separation....

The small discolored zones...appeared to be the initiation locations for the larger semielliptical areas. All the small discolored zones were less than 0.014 inches deep. It was also noted that many of the larger semielliptical areas were actually made up of several independently initiating and propagating crack fronts that joined together to form a larger front....

Longitudinal metallographic specimens...revealed microstructures typical of quenched and tempered martensite with no indication of grinding burns or other abnormal features....