- Date
- December 24, 1999, 13:49 local (20:49 UTC)
- Place
- Salt Lake City, UT
- Injuries
- 135 uninjured
- Damage
- Minor damage
- Phase of flight
- Takeoff
- Aircraft
- N305WABoeing 737-347
- Weather
- Visual (VMC) · Day
- Status
- Completed · report November 30, 2000
- Report
- Approved by Office Director
- FAA report
- 19991224036029I
- Case key
- 48391
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the incident.
On this page
Probable cause
The NTSB’s determination of the probable cause, and any contributing factors.
Improper assembly of the wheel during build up in the operator's maintenance facilities.
Analysis
During takeoff roll on a scheduled domestic passenger flight, the right main landing gear inboard wheel separated from the aircraft. The aircraft returned to the point of departure and landed without further incident. Examination of the landing gear revealed that the wrong wheel bearing had been installed when the wheel assembly was 'built up' at the operator's facility.
Factual narrative
On December 24, 1999, at 1349 mountain standard time, a Boeing 737-347, N305WA, operated by Delta Airlines as flight 1079 from Salt Lake City, Utah, to Detroit, Michigan, sustained minor damage when the landing gear right main inboard wheel assembly separated from the airplane during takeoff from Salt Lake City. There were no injuries to the 6 crew members and 127 passengers and the aircraft returned and landed at Salt Lake City, without incident, at 1630. The flight was operating under Title 14 CFR Part 121 as a scheduled domestic passenger flight and visual meteorological conditions prevailed. An IFR flight plan was filed.
When the wheel separated from the aircraft it struck and damaged runway lighting. (See attached photographs.)
Examination of the aircraft, following the event, revealed that a Boeing 757 main wheel bearing had been installed when the wheel was built up by Delta maintenance in Atlanta, Georgia.
The difference between the two wheel bearings is the inner diameter of the bore. The correct bearing (part number 596) has a diameter of 3.375 inches and the incorrect bearing (part number 594) has a diameter of 3.750 inches.
Boeing Commercial Airplane Group records search provided information that five cases of incorrect bearing installation have been reported to Boeing: Two cases in 1990, one in 1997, and two in 1999.
Sequence of events
NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.
Aircraft
- Registration
- N305WA
- Reported as
- Boeing 737-347
- Category
- Airplane
- Serial number
- 23346
- Airframe hours
- 36,898
- Engine
- GE CFM56-3, 20,000 lbs thrust, turbo fan
- Damage
- Minor damage
- Flight
- Part 121
- Operator
- Delta Airlines
- Registered owner
- State Street Bank And Trust
- Airworthiness certificate
- Standard, Transport
- Last inspection
- Continuous airworthiness · November 11, 1999
- Departed
- SLC
- Destination
- DTW · Detroit, MI
- Flight plan
- IFR
- Airport
- SLC · Salt Lake City Int'L, runway 34R, 12,004 × 150 ft, concrete
Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.
Flight crew
As NTSB recorded them. NTSB leaves out names.
- Role
- Pilot
- Age
- 41
- Certificate
- Airline transport
- Airplane ratings
- Multi-engine land
- Instrument ratings
- Airplane
- Medical
- Class 1, Valid Medical--no waivers/lim.
- Seat
- Left
- Flight hours
- 11,500 total · 1,850 in this make and model · 46 in the last 90 days
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- 290° at 6 knots
- Visibility
- 6 statute miles
- Lowest ceiling
- None
- Temperature
- 36 °F, dew point 27 °F
- Altimeter
- 30.00 inHg
- Observed at
- SLC, 1 nm away
Docket · 6
The files NTSB released with the investigation on March 20, 2000, on NTSB’s docket system: statements, records, photos and specialists’ reports. 3.3 MB in all.
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.