ASN Wikibase Occurrence # 367868
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| Date: | Monday 9 October 1989 |
| Time: | 12:45 LT |
| Type: |  Boeing 757-251 |
| Owner/operator: | Northwest Airlines |
| Registration: | N512US |
| MSN: | 23201/83 |
| Year of manufacture: | 1986 |
| Total airframe hrs: | 11582 hours |
| Engine model: | P&W 2037 |
| Fatalities: | Fatalities: 0 / Occupants: 147 |
| Aircraft damage: | Minor |
| Category: | Serious incident |
| Location: | San Francisco, CA -
 United States of America
|
| Phase: | Unknown |
| Nature: | Passenger - Scheduled |
| Departure airport: | Detroit, MI (KDTW) |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
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.
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.
Accident investigation:
 |
|
Sources:
NTSB CHI90IA006
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 22-Mar-2024 19:44 | ASN Update Bot | Added |
Corrections or additions? ... Edit this accident description
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