NTSB Identification: LAX90DVA04.
The docket is stored on NTSB microfiche number 41121.
Accident occurred Friday, June 08, 1990 in BUTTONWILLOW, CA
Probable Cause Approval Date: 09/04/1992
Aircraft: Grumman-Schweizer G-164B, registration: N6725K
Injuries: 1 Serious,1 Minor.

THE PILOT WAS COMPLETEING AN AERIAL APPLICATION SWATH RUN, WHEN HE HEARD A LOUD BACKFIRE EMANATE FROM THE ENGINE DURING THE PULL-UP. THE ENGINE THEN QUIT RUNNING ALTOGETHER. THE PILOT ATTEMPTED TO MAKE A LANDING ON A DIRT ROAD, BUT LANDED SHORT IN A TOMATO FIELD, AND THE AIRCRAFT NOSED OVER ONTO ITS BACK. EXAMINATION OF THE ENGINE REVEALED THAT THE NUMBER 7 CYLINDER HEAD HAD A CRACK, WHICH EXTENDED FROM THE FORWARD SPARK PLUG BOSS AROUND THE CYLINDER HEAD TO THE REAR SPARK PLUG BOSS. DETAILED EXAMINATION OF THE CRACK SHOWED THAT THE FRACTURE FACE WAS CONTAMINATED BY CARBON DEPOSITS AND LIGHT CORROSION IN THE COARSE AREA OF THE CRACK, INDICATING THAT THE CRACK WAS PRESENT FOR A LENGTHY PERIOD OF TIME PRIOR TO THE ACCIDENT. THE CYLINDER WAS REPORTED TO HAVE ONLY 181 HOURS SINCE OVERHAUL.

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

FAILURE OF THE #7 CYLINDER DUE TO A PRE-EXISTING CRACK. THE TERRAIN CONDITION WAS A RELATED FACTOR.

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