Serious incident Douglas DC-9-32 N986US, Thursday 5 May 1994

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Date:	Thursday 5 May 1994
Time:	09:55 LT
Type:	Douglas DC-9-32
Owner/operator:	Northwest Airlines
Registration:	N986US
MSN:	47480/607
Year of manufacture:	1970
Total airframe hrs:	54685 hours
Engine model:	P&W JT8D-15
Fatalities:	Fatalities: 0 / Occupants: 69
Other fatalities:	0
Aircraft damage:	Minor
Category:	Serious incident
Location:	Memphis, TN - United States of America
Phase:	Take off
Nature:	Unknown
Departure airport:
Destination airport:	Phoenix, AZ (KPHX)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
DURING TAKEOFF, AN UNCONTAINED FAILURE OF THE LEFT ENGINE OCCURRED. AN EXAMINATION REVEALED A FATIGUE FRACTURE THROUGH A REAR FLANGE BOLT HOLE OF THE COMBUSTION CHAMBER OUTER CASE, AT THE THREE O'CLOCK POSITION OF THE ENGINE. THE ENGINE HAD BEEN INSPECTED IN ACCORDANCE WITH AN APPLICABLE AIRWORTHINESS DIRECTIVE; HOWEVER, THE FRACTURE OCCURRED 2,060 CYCLES PRIOR TO THE NEXT SCHEDULED INSPECTION. ADDITIONAL INSPECTION REQUIREMENTS RESULTED FROM THE EXAMINATIONS OF THE ENGINE AND THE FRACTURE.

Probable Cause: THE FATIGUE FRACTURE OF THE COMBUSTION CHAMBER OUTER CASE. A FACTOR WAS THE MANUFACTURER'S INADEQUATE INSPECTION CRITERIA.

Accident investigation: