Boeing 747-251B N631US

Summary

On 2 November 1994 at about 15:20 local time, a Boeing 747-251B registered N631US, operated by Northwest Airlines, Inc., was involved in an incident near CHICAG0, Illinois, United States. 3 people were on board and nobody was injured. The aircraft was slightly damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

2 November 1994 at 15:20

Classification

Incident

Location

CHICAG0, Illinois, United States

Nearest airport

Chicago O'hare Intl (ORD)

Coordinates

Not recorded

Aircraft

Boeing 747-251B

Registration

N631US

Category

Airplane

Engines

4

Operator

Northwest Airlines, Inc.

Operating rule

Part 91: General Aviation

Purpose of flight

Positioning

Phase of flight

Not recorded

Route

Detroit → Chicago

Aircraft damage

Minor

Weather

VMC

Light

Not Reported

NTSB number

CHI95IA028

Nobody was injured.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.