Accident Board Findings

The National Transportation Safety Board (NTSB) determined that the probable cause of this accident was the disintegration of the No. 3 engine fan assembly as a result of interaction between the fan blade tips and the fan case. The fan-tip rub condition was caused by the acceleration of the engine to an abnormally high fan speed, which initiated a multiwave vibration resonance within the fan section of the engine.

The precise reason or reasons for the acceleration and the onset of the destructive vibration could not be conclusively determined.

The NTSB identified 14 findings for this accident that can be found in the National Airlines Albuquerque NTSB Accident Report, NTSB-AAR-75-2. Note if you click on this link, you will have to click the Back button in your browser to return to the lesson.

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