# NTSB FTW95IA348: Boeing 737-3H4, N309SW, Lubbock, TX, August 18, 1995 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: August 18, 1995, 11:55 local (16:55 UTC) - Place: Lubbock, TX - Location: 33.6637° N, 101.8206° W: Placed by OpenAirDocs at LUBBOCK PRESTON SMITH INTL (LBB), within about a mile (OpenAirDocs) - Nearby events: https://openairdocs.org/map.md?lat=33.6637&lon=-101.8206&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 114 uninjured - Status: Completed, report March 21, 1996 - Report: Approved by Office Director - NTSB case key (mKey): 19273 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW95IA348 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/19273/pdf - Page: https://openairdocs.org/ntsb/FTW95IA348 ## Probable cause installation of an incorrect bearing in the number three main wheel by the wheel assembly supplier, which led to subsequent failure of the wheel bearing and separation of the wheel during takeoff. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, takeoff - roll/run - landing gear,wheel - incorrect (cause) - maintenance,rebuild/remanufacture - improper, other maintenance personnel (cause) - landing gear,wheel - failure (cause) - landing gear,wheel - separation ## Analysis During takeoff at Lubbock, Texas, the number three wheel assembly separated from the axle. The aircrew continued the flight and landed uneventfully at Albuquerque, New Mexico. Company maintenance records indicated the wheel assembly was last replaced on August 16, 1995. Examination of the aircraft revealed that the axle nut was intact on the axle along with the tang washer. The axle nut locking ring was also in place. The outer bearing was found deteriorated with only its inner race remaining, and the inner bearing remained intact on the axle. Examination of the components revealed that, an incorrect inner bearing had been installed inadvertently by the wheel assembly supplier on the number three wheel assembly. A Timkin part number 594 bearing was installed in lieu of the correct Timkin part number 596 bearing. ## Factual narrative On August 18, 1995, at 1155 central daylight time, a Boeing 737- 3H4, N309SW, sustained minor damage as the number three main wheel separated from the axle on gear retraction during takeoff from Lubbock International Airport (LBB), Lubbock, Texas. The crew of five and 109 passengers were not injured. Visual meteorological conditions prevailed for the Southwest Airlines Flight 866, scheduled Title 14 CFR Part 121 flight to Albuquerque, New Mexico. Personnel in the Lubbock Air Traffic Control (ATC) Tower observed the number three right main wheel depart the aircraft. During the aircraft's climb, the tower informed the crew of the event. The crew reported to ATC that they would continue the flight to the destination. Upon arrival at Albuquerque (ABQ), New Mexico, the crew landed the aircraft and taxied to the ramp without further incident. Examination of the aircraft at Albuquerque by company maintenance personnel and a Federal Aviation Administration (FAA) inspector revealed the axle nut was intact on the axle along with the tang washer. The axle nut locking ring was also in place. The outer bearing was found deteriorated with only its inner race remaining. The inner bearing was still intact on the axle. Company maintenance records indicated the wheel assembly was last replaced on August 16, 1995. Examination of the wheel components by company maintenance personnel, a FAA inspector, and the investigator-in-charge, revealed that an incorrect inner bearing had been installed on the number three wheel assembly. A Timkin part number 594 bearing was installed in lieu of the correct Timkin part number 596 bearing. The supplier of the wheel assembly, reported to Southwest Airlines, that in their opinion the 594 bearing was inadvertently packed with Mobil 28 grease (red) instead of Aeroshell 5 grease (yellow), and placed into customer stock without an identification tag. Since the 594 and 596 bearings are very similar in appearance once packed with grease, the 594 bearing was misidentified by a small parts area mechanic as a 596 bearing. The bearing was also retrieved from customer stock without the assistance of a certified material control inspector. While bearing part numbers are listed on the process card that travels with the wheel halves, they were not listed on the portion of the card that travels with the small parts. In three instances, the small parts mechanic, the finished mechanic, and final inspector did not verify the number on the bearing. (See enclosed letter.) ## Aircraft - Registration: [N309SW](https://openairdocs.org/deregistered/N309SW-2017-05-22), registration cancelled 2017-05-22, S/N 22948, built 1985 (OpenAirDocs) - Reported make and model: BOEING 737-3H4 - Registry model: [Boeing 737-3H4](https://openairdocs.org/model/boeing-737-3h4) (registry code 138447K) (OpenAirDocs) - Registry engine: [CFM International CFM56 series](https://openairdocs.org/engine/cfm-international-cfm56-series) (registry code 13802, turbo-fan) (OpenAirDocs) - Category: Airplane - Serial number: 22948 - Engines: GE CFM-56 20000 lbs thrust turbo fan - Damage: Minor damage - Flight: Part 121 - Registered owner: Southwest Airlines - Airworthiness certificate: Standard, Transport - Departed: LBB - Destination: ABQ, ALBUQUERQUE, NM - Flight plan: IFR - Airport: LBB, Lubbock International, runway 26, 8,001 × 150 ft, concrete ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 48; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: helicopter, airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 20,000 total, 15,000 in this make and model ## Weather - Conditions: Visual (VMC), Day - Visibility: 10 statute miles From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.