Boeing 737 N551WN

Summary

On 1 October 2008 at about 16:55 local time, a Boeing 737 registered N551WN, operated by Southwest Airlines, Co., was involved in an incident near Chicago, Illinois, United States. 133 people were on board and nobody was injured. The aircraft was slightly damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

1 October 2008 at 16:55

Classification

Incident

Location

Chicago, Illinois, United States

Nearest airport

Chicago Midway (MDW)

Coordinates

41.8892, -87.6202

Aircraft

Boeing 737

Registration

N551WN

Category

Airplane

Engines

2

Operator

Southwest Airlines, Co.

Operating rule

Part 121: Air Carrier

Phase of flight

Not recorded

Route

Kansas City → Chicago

Aircraft damage

Minor

NTSB number

ENG08IA042

Nobody was injured.

The right nose landing gear axle's failure from intergranular and fatigue cracking due to an earlier bearing failure.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.