Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
San Francisco, California 94111
Monday, October 9, 1989 11:45 PDT
NTSB Narrative Summary Released at Completion of Accident
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.
NTSB Probable Cause Narrative
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.
Event Information
| Type of Event | Incident |
| Event Date | 10/9/1989 |
| Event Day of the Week | Monday |
| Time of Event | 1145 |
| Event Time Zone | Pacific Daylight Time |
| Event City | SAN FRANCISCO |
| Event State | CALIFORNIA |
| Event Country | -- |
| Zipcode of the event site | 94111 |
| Event Date Year | 1989 |
| Event Date Month | 10 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | |
| Event Location Longitude | |
| Event Location Airport | |
| Event Location Nearest Airport ID | |
| Indicates whether the acc/inc occurred off or on an airport | Off Airport/Airstrip |
| Distance from airport in statute miles | 0 |
| Degrees magnetic from airport | 0 |
| Airport Elevation | 0 |
| Weather Briefing Completeness | Not pertinent |
| Investigator's weather source | Pilot |
| Time of the weather observation | 0 |
| Direction of event from weather observation facility (degrees) | 0 |
| Weather Observation Facility ID | |
| Elevation of weather observation facility | 0 |
| Distance of event from weather observation facility (units?) | 0 |
| Time Zone of the weather observation | |
| Lighting Conditions | Day |
| Lowest Ceiling Height | 0 |
| Lowest Non-Ceiling Height | 0 |
| Sky/Lowest/Cloud Conditions | Clear |
| Sky Condition for Lowest Ceiling | None |
| Visibility Runway Visual Range (Feet) | 0 |
| Visibility Runway Visual Value (Statute Miles) | 0 |
| Visibility (Statute Miles) | 15 |
| Air Temperature at event time (in degrees celsius) | 21 |
| Dew Point at event time (in degress fahrenheit) | -- |
| Wind Direction (degrees magnetic) | 290 |
| Variable Wind Indicator | Unknown |
| Wind Speed (knots) | 6 |
| Wind Velocity Indicator | Unknown |
| Wind Gust Indicator | Not Gusting |
| Wind Gust (knots) | 0 |
| Altimeter Setting at event time (in. Hg) | -- |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | Unknown |
| 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 | 147 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 5059 |
| NTSB Notification Source | -- |
| NTSB Notification Date | Oct 10 1989 12:00AM |
| NTSB Notification Time | 1030 |
| Fiche Number and/or location -used to find docket information | 41595 |
| Date of most recent change to record | Dec 13 2000 1:07PM |
| User who most recently changed record | dbo |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N512US |
| NTSB Number | CHI90IA006 |
| Missing Aircraft Indicator | N |
| Federal Aviation Reg. Part | Part 121: Air Carrier |
| Type of Flight Plan filed | IFR |
| Flight plan Was Activated? | -- |
| Damage | Minor |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | BOEING |
| Aircraft Model | 757-251 |
| Aircraft Series Identifier | 757-251 |
| Aircraft Serial Number | 23201 |
| Certified Max Gross Weight | 240000 |
| Aircraft Category | Airplane |
| Aircraft Registration Class | U.S. Registered/U.S. Soil |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | -- |
| Cabin Crew Seats | -- |
| Passenger Seats | -- |
| Total number of seats on the aircraft | 178 |
| 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 | -- |
| Airframe Hours | 11582 |
| ELT Installed | Unknown |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | FIRST NAT'L BANK OF BOSTON TST |
| Aircraft Owner Street Address | 100 FEDERAL ST. |
| Aircraft Owner City | BOSTON |
| Aircraft Owner State | MA |
| Aircraft Owner Country | |
| Aircraft Owner Zipcode | 02110 |
| Operator is an individual? | -- |
| Operator Name | NORTHWEST AIRLINES |
| Operator Same as Owner? | No |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | No |
| Operator Street Address | MSP/ST. PAUL INT'L AIRPORT |
| Operator City | ST. PAUL |
| Operator State | MN |
| Operator Country | |
| Operator Zip code | 55111 |
| Operator Code | |
| Owner has at least one certificate | Yes - certificate holder |
| Other Operator of large aircraft? | No |
| Certified for Part 133 or 137 Operation | Unknown |
| 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/Cargo |
| Type of Flying (Per_Bus / Primary) | Unknown |
| Second Pilot on Board | Yes |
| Departure Point Same as Event | No |
| Departure Airport Code | DTW |
| Departure City | DETROIT |
| Departure State | MI |
| Departure Country | |
| Departure Time | 936 |
| Departure Time Zone | EDT |
| Destination Same as Local Flt | crash at destination city |
| Destination Airport Code | |
| Destination City | |
| Destination State | |
| Destination Country | |
| Specific Phase of Flight | Approach |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Jan 2 2001 10:30AM |
| User who most recently changed record | dbo |
| Since inspection or accident | -- |
| Event Location Runway Number and Location | 0 |
| Runway Length | 0 |
| Runway Width | 0 |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |