- Date
- October 9, 1989, 11:45 local (18:45 UTC)
- Place
- San Francisco, CA
- Injuries
- 147 uninjured
- Damage
- Minor damage
- Phase of flight
- Enroute
- Aircraft
- N512USBoeing 757-251
- Weather
- Visual (VMC) · Day
- Status
- Completed · report August 26, 1992
- Report
- Approved by Office Director
- Case key
- 14560
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 extreme wear and eventual failure of a torque tube in the inboard trailing edge flap system. Inspection and lubrication intervals were a factor, as was the physical location of the torque tube with reference to external factors.
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.
Analysis
The flight crew reported that they received a 'flap disagree' message during the descent and approach to their destination airport. When checklist procedures were not successful in correcting the situation, an uneventful 'abnormal flap' landing was performed. Post-incident inspection revealed a failed inboard trailing edge flap drive torque tube coupling. Further investigation revealed one similar failure, and examination of the operating 757 fleet revealed numerous occurrences of excessive wear on the aft coupling of the torque tube assembly. Lab analysis of the wear, and a metallurgical examination resulted in the manufacturer reducing the recommended maintenance interval and recommending more frequent visual inspections of the component.
Aircraft
- Registration
- N512US
- Reported as
- Boeing 757-251
- Category
- Airplane
- Serial number
- 23201
- Airframe hours
- 11,582
- Engine
- P&W 2037, 38,200 lbs thrust, turbo fan
- Damage
- Minor damage
- Flight
- Part 121
- Operator
- Northwest Airlines
- Registered owner
- First Nat'L Bank Of Boston Tst
- Airworthiness certificate
- Standard, Transport
- Departed
- DTW · Detroit, MI
- Flight plan
- IFR
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
- 49
- Certificates
- Airline transport, Commercial
- Airplane ratings
- Multi-engine land, Single-engine sea, Single-engine land
- Instrument ratings
- Airplane
- Medical
- Class 1, Valid Medical--w/ waivers/lim
- Seat
- Left
- Flight hours
- 11,700 total · 150 in the last 90 days · 50 in the last 30 days
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- 290° at 6 knots
- Visibility
- 15 statute miles
- Lowest ceiling
- None
- Temperature
- 70 °F