The National Transportation Safety Board determines that the probable cause of this accident was the failure of Turk Hava Yollari maintenance and inspection personnel to perform a proper inspection of a 7th stage high compressor disk, thus allowing the detectable crack to grow to a length at which the disk ruptured, under normal operating conditions, propelling engine fragments into the fuselage; the fragments severed the right engine main fuel line, which resulted in a fire that rapidly engulfed the cabin area. The lack of an adequate record keeping system and the failure to use "process sheets" to document the step-by-step overhaul/inspection procedures contributed to the failure to detect the crack and, thus, to the accident.
The safety issues in this report include the clarity of operations specifications for repair stations, record keeping requirements for foreign repair stations, regulatory guidance concerning maintenance documentation, intent of "serviceable tags," independently powered public address systems on all transport-category airplanes, flight attendant training programs and manuals, enforcement of occupant restraint requirements, and cabin material/fire safety standards.