NTSB Identification: ENG09IA014
Scheduled 14 CFR Part 121: Air Carrier operation of Southwest Airlines, Co.
Incident occurred Tuesday, September 08, 2009 in Los Angeles, CA
Probable Cause Approval Date: 01/07/2011
Aircraft: BOEING 737, registration: N670SW
Injuries: 142 Uninjured.

NTSB investigators traveled in support of this investigation and used data obtained from various sources to prepare this aircraft incident report.

During landing, the inboard axle of the right main landing gear separated from the airplane. The crew taxied the airplane off the runway and the passengers and crew deplaned with no injuries. Examination of the axle revealed an area of fatigue cracking emanating from the brake mounting bolt hole at the 12:00 position. The fatigue crack likely initiated in an area where there was scoring and fretting damage to the Sermetal coating. In-service examination of brake mounting bolt torque indicated that over time, the brake mounting bolts may loosen allowing the bolts to spin in the holes.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

The failure of the right main landing gear inboard axle due to fatigue cracking as a result of fretting damage in one of the brake mounting bolt holes.

Full narrative available

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