NTSB Identification: FTW92IA055.
The docket is stored on NTSB microfiche number 46525.
Scheduled 14 CFR operation of DELTA AIR LINES, INC.
Incident occurred Tuesday, January 07, 1992 in DFW AIRPORT, TX
Probable Cause Approval Date: 06/30/1993
Aircraft: BOEING 737-232, registration: N322DL
Injuries: 49 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

THE RIGHT ENGINE SEPARATED FROM THE WING AS THE AIRPLANE WAS CLIMBING THROUGH 200 FEET AFTER TAKEOFF. FOLLOWING THE ENGINE SEPARATION, THE CREW CONTINUED THE CLIMB AND WERE VECTORED FOR AN UNEVENTFUL LANDING WITHOUT FURTHER INCIDENT. ENGINE SEPARATION WAS THE RESULT OF THE FAILURE OF THE AFT CONE BOLT AND THE ENGINE SECONDARY SUPPORT ASSEMBLY. THE AFT CONE BOLT FAILED AS RESULT OF A PREEXISTING FATIGUE CRACK, WHILE THE ENGINE SECONDARY SUPPORT ASSEMBLY FAILED AS RESULT OF THE DYNAMIC LOADS THAT EXCEEDED THE DESIGNED CAPACITY OF THE MOUNTING BOLTS. THE TWO FORWARD CONE BOLTS FAILED IN OVERLOAD AS THE ENGINE SWUNG FORWARD DURING THE SEPARATION SEQUENCE. METALLURGICAL TESTING REVEALED THAT THE FATIGUE OF THE AFT CONE BOLT WAS A RESULT OF LUBRICANT INADVERTENTLY INTRODUCED INTO THE CONICAL SURFACE OF THE CONE BOLT.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

THE FAILURE OF THE AFT CONE BOLT AS RESULT OF PREEXISTING FATIGUE CRACKING DUE TO IMPROPER MAINTENANCE, AND THE FAILURE OF THE SECONDARY SUPPORT STRUCTURE AS A RESULT OF LOADS THAT EXCEEDED THE CAPACITY OF THE ATTACHING HARDWARE AND THE CRUSHABLE HONEYCOMB CORE.

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