NTSB Identification: FTW89DPJ08.
The docket is stored on NTSB microfiche number 39309.
Accident occurred Friday, July 07, 1989 in GUYMON, OK
Probable Cause Approval Date: 09/05/1991
Aircraft: GRUMMAN G-164, registration: N788Y
Injuries: 1 Serious.

DURING PULLUP FOR A TURNAROUND MANEUVER, THE ENG FELL FROM THE AG AIRPLANE. CONTROL WAS LOST & THE AIRPLANE HIT FLAT IN A FIELD. A POST-ACDNT INVESTIGATION REVEALED THE UPPER RIGHT ENG MOUNT (FIREWALL ATTACH BOLT) HAD FAILED FROM FATIGUE. THE LOWER RIGHT BOLT HAD ALSO FAILED PRIOR TO ENG SEPARATION, BUT ITS FACTURE SURFACE WAS TOO BADLY DAMAGED TO VERIFY THE REASON OF FAILURE. THE UPPER LEFT & LOWER LEFT ATTACH BOLTS WERE FOUND NECKED DOWN AT THEIR RESPECTIVE FRACTURES FROM OVERLOAD FAILURE.

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

FAILURE OF THE UPPER RIGHT ENGINE MOUNT (FIREWALL ATTACH BOLT) DUE TO FATIGUE, AND FAILURE OF THE LOWER RIGHT MOUNTING BOLT FOR AN UNKNOWN REASON, WHICH ALLOWED OVERLOAD FAILURE OF THE TWO REMAINING MOUNTING BOLTS AND SEPARATION OF THE ENGINE.

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