Boeing 747-251B incident near Chicag0, Illinois, November 2, 1994
On November 2, 1994 at about 3:20 pm local time, a Boeing 747-251B, registered N631US, suffered minor damage in an incident near Chicag0, Illinois (Chicago O'Hare Intl airport). It was a positioning flight under general aviation rules (Part 91). No one was hurt; 3 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
inattentive maintenance service of the airplane by the mechanic who failed to disengage the constant speed drive (CSD) after the engine runup had been completed. A factor in this incident was the lead mechanic not performing maintenance record keeping after being informed that the CSD had been recoupled.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- November 2, 1994 · about 3:20 pm local time
- Place
- Chicag0, Illinois · Chicago O'Hare Intl
- Type
- Incident
- Injuries
- No one was hurt; 3 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Boeing 747-251B · all 747-251Bs on the register
- Registration
- N631US · no longer on the register · serial 23111
- Damage
- Minor damage
- Flight
- Positioning flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
THE FLT CREW DISCONNECTED THE NUMBER ONE ENG CONSTANT SPEED DRIVE (CSD) DURING A FLT ON THE DAY PRIOR TO THIS INCIDENT WHEN ITS OIL PRESSURE LIGHT ILLUMINATED. DUE TO OTHER, UNRELATED MAINTENANCE, THE AIRPLANE'S NEXT REVENUE FLT WAS CANCELLED. SECOND SHIFT MECHANICS WERE ASSIGNED MAINTENANCE ON THE AIRPLANE. THE MECHANICS DECIDED TO TROUBLESHOOT THE UNIT. THE CSD WAS MECHANICALLY RECOUPLED AND THE ENG WAS STARTED. AFTER THE ENG START, THE START VALVE LIGHT FAILED TO GO OUT AND THE ENGINE WAS SHUT DOWN. A MECHANIC REMOVED THE MAIN CSD WIRING HARNESS CANNON PLUG TO HELP WITH THE TROUBLE SHOOTING PROCESS. THE START VALVE WAS REPLACED AND THE ENG WAS RUNUP. THE CSD CANNON PLUG WAS NOT CONNECTED AT THE CONCLUSION OF THE ENG RUNUP. AFTER SHUTDOWN THE START VALVE CHANGE WAS ENTERED INTO THE AIRPLANE MAINTENANCE RECORDS. THE MECHANIC WHO RECOUPLED THE CSD INFORMED THE LEAD MECHANIC OF HIS ACTION BEFORE HE LEFT FOR THE DAY. ACCORDING TO THE COMPANY, THE THIRD SHIFT MECHANICS DID NOT HAVE ENOUGH TIME TO CHANGE THE CSD. THE NUMBER ONE ENG WAS '...CLOSED UP [AND] THE AIRCRAFT WAS DISPATCHED.' DURING TAXI FROM LANDING THE CSD CAUGHT FIRE.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: airline transport pilot
- Ratings: multi-engine land; instrument: airplane
- Flight time: 15,000 hours in all
- Medical certificate: Unknown
- Seat: left
The aircraft
- Airframe total time: 40,562 hours
- Last inspection: continuous airworthiness programme, November 2, 1994; 1 hours since
- Maximum gross weight: 820,000 lb
- Seats: 350
- Landing gear: retractable
- Engine: P&W JT9D-7R4 (turbojet); 0 hours total
- Fire on the ground
- Operator: Northwest Airlines, INC.
The flight
- Departed from: DTW Detroit MI at 2:02 pm
- Destination: ORD Chicago IL
- Flight plan: not recorded
- Runway 0
- A second pilot was aboard
Weather at the time
- Light: not reported
- Sky: not recorded; not recorded
- Temperature: 0°F (-18°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 3 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.