NTSB Identification: MIA90IA148.
The docket is stored on NTSB microfiche number 42913.
Incident occurred Monday, July 02, 1990 in TYNDALL AFB, FL
Probable Cause Approval Date: 11/09/1992
Aircraft: MITSUBISHI MU-2B, registration: N722DM
Injuries: 2 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 PILOT NOTED A SEVERE VIBRATION IN FLIGHT FROM THE LEFT ENGINE. HE SHUT THE ENGINE DOWN AND LANDED. ONE PROPELLER BLADE WAS MISSING PART OF THE BLADE. THE FAILED ASSEMBLY WAS EXAMINED AND THE FAILED BLADE SHOWED EVIDENCE OF HIGH CYCLE, LOW STREES FATIGUE WITH A SURFACE ORIGIN. THE OTHER TWO BLADES WERE FOUND TO BE LESS THAN MINIMUM DIMENSIONS AND HAD IMPROPERLY POLISHED AND PROTECTED SURFACES.

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

A PROPELLER BLADE FATIGUE FAILURE DUE TO IMPROPER OVERHAUL BY OTHER MAINTENANCE PERSONNEL NOT PERFORMING OVERHAUL IN ACCORDANCE WITH FACTORY SERVICE BULLETINS.

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