Probable cause
The right nose landing gear axle's failure from intergranular and fatigue cracking due to an earlier bearing failure.
NTSB analysis
The airplane experienced separation of the right nose landing gear (NLG)wheel assembly as it exited runway after landing. Metallurgical examination revealed that the NLG axle fractured in a transverse plane, and that the failure of the axle was due to intergranular cracking that acted as stress concentrators from which fatigue cracks emanated. The fracture of the right side inboard journal on the NLG inner cylinder assembly was most likely due to the failure of a prior tapered roller bearing. Eventually the size of the fatigue crack and the forces generated during landing were sufficient to drive the crack in overstress, leading to fracture of the inboard journal. The change in ownership of the plane and the monthly swapping of bearings and wheels make it difficult to determine when the bearing failure occurred or why.
Text from the NTSB. Open the NTSB docket for ENG08IA042 for the full record.
Event
- Date
- Oct 1, 2008
- Type
- Incident
- Place
- Chicago, Illinois
- Nearest airport
- Chicago Midway (MDW)
- Highest injury
- None
Boeing 737
- N-number
- N551WN
- Category
- Airplane
- Damage
- Minor
- Operating rule
- Part 121 (airline)
Other records under this N-number
From the NTSB aviation accident database: N-registered aircraft, events since 2008, data through Oct 28, 2026. The file is published monthly, so the latest weeks are incomplete and recent records can change. The official source is the NTSB aviation investigation search. CheckAero is independent and not affiliated with the NTSB.