Individually Owned: 150,657
Corporate Owned: 137,281
Chicago Midway Airport
Aircraft Accident/Incident Report
Chicago, Illinois 60368
Wednesday, October 1, 2008 10:55 CST
NTSB Narrative Summary Released at Completion of Accident
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.
NTSB Probable Cause Narrative
The right nose landing gear axle's failure from intergranular and fatigue cracking due to an earlier bearing failure.
Event Information
| Type of Event | Incident |
| Event Date | 10/1/2008 |
| Event Day of the Week | Wednesday |
| Time of Event | 1055 |
| Event Time Zone | Central Standard Time |
| Event City | Chicago |
| Event State | ILLINOIS |
| Event Country | -- |
| Zipcode of the event site | 60368 |
| Event Date Year | 2008 |
| Event Date Month | 10 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | -- |
| Event Location Longitude | -- |
| Event Location Airport | Chicago Midway |
| Event Location Nearest Airport ID | MDW |
| Indicates whether the acc/inc occurred off or on an airport | On Airport |
| Distance from airport in statute miles | 0 |
| Degrees magnetic from airport | -- |
| Airport Elevation | 620 |
| Weather Briefing Completeness | -- |
| Investigator's weather source | -- |
| Time of the weather observation | |
| Direction of event from weather observation facility (degrees) | -- |
| Weather Observation Facility ID | -- |
| Elevation of weather observation facility | -- |
| Distance of event from weather observation facility (units?) | -- |
| Time Zone of the weather observation | -- |
| Lighting Conditions | -- |
| Lowest Ceiling Height | -- |
| Lowest Non-Ceiling Height | -- |
| Sky/Lowest/Cloud Conditions | -- |
| Sky Condition for Lowest Ceiling | -- |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | -- |
| Air Temperature at event time (in degrees celsius) | -- |
| Dew Point at event time (in degress fahrenheit) | -- |
| Wind Direction (degrees magnetic) | -- |
| Variable Wind Indicator | -- |
| Wind Speed (knots) | -- |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | -- |
| Wind Gust (knots) | -- |
| Altimeter Setting at event time (in. Hg) | -- |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | -- |
| Event Highest Injury | None |
| On Ground, Fatal Injuries | 0 |
| On Ground, Minor Injuries | 0 |
| On Ground, Serious Injuries | 0 |
| Injury Total Fatal | -- |
| Injury Total Minor | -- |
| Injury Total None | 133 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 26187 |
| NTSB Notification Source | Sowthwest Airlines |
| NTSB Notification Date | -- |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Mar 23 2010 4:49PM |
| User who most recently changed record | broda |
| Basic weather conditions | -- |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N551WN |
| NTSB Number | ENG08IA042 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 121: Air Carrier |
| Type of Flight Plan filed | IFR |
| Flight plan Was Activated? | Yes |
| Damage | Minor |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | BOEING |
| Aircraft Model | 737 |
| Aircraft Series Identifier | -76Q |
| Aircraft Serial Number | 30280 |
| Certified Max Gross Weight | 154000 |
| Aircraft Category | Airplane |
| Aircraft Registration Class | -- |
| Aircraft is a homebuilt? | -- |
| Flight Crew Seats | 4 |
| Cabin Crew Seats | 4 |
| Passenger Seats | 137 |
| Total number of seats on the aircraft | 145 |
| Number of Engines | 2 |
| Fixed gear or retractable gear | Retractable |
| Aircraft, Type of Last Inspection | Continuous Airworthiness |
| Date of Last Inspection | -- |
| Airframe hours since last inspection | 3 |
| Airframe Hours | 21206 |
| ELT Installed | No |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | Wells Fargo |
| Aircraft Owner Street Address | 299 S. Main Street |
| Aircraft Owner City | Salt Lake City |
| Aircraft Owner State | UT |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 84111 |
| Operator is an individual? | No |
| Operator Name | Southwest Airlines, Co. |
| Operator Same as Owner? | No |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | No |
| Operator Street Address | 2702 Love Field Drive |
| Operator City | Dallas |
| Operator State | TX |
| Operator Country | USA |
| Operator Zip code | 75235 |
| Operator Code | SWAA |
| Owner has at least one certificate | Yes - certificate holder |
| Other Operator of large aircraft? | No |
| Certified for Part 133 or 137 Operation | -- |
| Operator Certificate Number | -- |
| Indicates whether an air carrier operation was scheduled or not | Scheduled |
| Indicates Domestic or International Flight | Domestic |
| Operator carrying Pax/Cargo/Mail | Passenger Only |
| Type of Flying (Per_Bus / Primary) | -- |
| Second Pilot on Board | Yes |
| Departure Point Same as Event | No |
| Departure Airport Code | MCI |
| Departure City | Kansas City |
| Departure State | MO |
| Departure Country | USA |
| Departure Time | 943 |
| Departure Time Zone | CDT |
| Destination Same as Local Flt | crash at destination city |
| Destination Airport Code | MDW |
| Destination City | Chicago |
| Destination State | IL |
| Destination Country | USA |
| Specific Phase of Flight | -- |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Mar 23 2010 4:49PM |
| User who most recently changed record | broda |
| Since inspection or accident | Last Inspection |
| Event Location Runway Number and Location | 31C |
| Runway Length | 6522 |
| Runway Width | 150 |
| Sight Seeing flight | -- |
| Air Medical Flight | -- |
| Medical Flight | -- |