CHI00LA296

The Boeing 727-224 number 3 wheel assembly failed during taxi for takeoff and pieces of the wheel assembly impacted the airframe causing damage. Examination of the wheel assembly revealed a fatigue failure that emanated from a point at the inside diameter of one of the brake lugs. A circumferential scratch was found adjacent to the fatigue origin. The wheel half had been inspected by an approved repair station and shipped to the airline on July 21, 2000. The wheel was installed on the accident aircraft and had accumulated 356.2 hours time in service at the time of the accident. A review of repair station records revealed that the repair station had been rejecting about 4 wheel halves per month. Prior to the accident, the repair station was finding cracks on other wheel halves in the area where the wheel failure occurred. The repair station had been in contact with the wheel manufacturer concerning this matter and had sent representative wheel halves to the manufacturer for evaluation. In a conversation with a representative of the Federal Aviation Administration, the wheel manufacturer stated that one of the returned wheel halves had been examined and that a manufacturing defect had created a stress concentrator, which resulted in a fatigue failure of the wheel half. The wheel manufacturer issued a Service Bulletin to rework the lugs and to provide guidance in inspecting the affected areas of the wheel assembly.

On September 10, 2000, at 0938 central daylight time, a Boeing 727-224, N296SC, operated by Sun Country Airlines as flight 791, sustained substantial damage when the number 3 wheel and tire assembly failed during taxi at the Minneapolis International Airport, Minneapolis, Minnesota. Pieces of the wheel assembly subsequently impacted the airframe causing the damage. The 14 CFR Part 121 flight was operating in visual meteorological conditions at the time of the accident. No injuries were reported to the 7 crew members or 94 passengers on board. The flight was taxiing to the runway for a departure to the San Francisco International Airport, San Francisco, California.

The wheel components were sent to the NTSB Materials Laboratory in Washington, D.C. for further examination. The examination report indicates that most of the fracture surfaces exhibited signatures consistent with overstress fracture. However, a portion of the fracture surface exhibited signatures consistent with fatigue. The fatigue origin was found to emanate from a point at the inside diameter of one of the brake lugs. A circumferential scratch was found adjacent to the fatigue origin.

The wheel half had been inspected by an approved repair station and shipped to the airline on July 21, 2000. The wheel had accumulated 356.2 hours time in service at the time of the accident. A review of repair station records revealed that the repair station had been rejecting about 4 wheel halves per month. Prior to the accident, the repair station was finding cracks on other wheel halves in the area where the wheel failure occurred. The repair station had been in contact with the wheel manufacturer concerning this matter and had sent representative wheel halves to the manufacturer for evaluation. In a conversation with a representative of the Federal Aviation Administration, the wheel manufacturer stated that one of the returned wheel halves had been examined and that a manufacturing defect had created a stress concentrator, which resulted in a fatigue failure of the wheel half.

On May 04, 2001, the wheel manufacturer issued a Service Bulletin, number 2604561-32-001, to rework the lugs and to provide guidance in inspecting the affected areas of the wheel assembly.