NTSB Identification: NYC00LA144.
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Accident occurred Thursday, May 25, 2000 in TOMS RIVER, NJ
Probable Cause Approval Date: 05/18/2001
Aircraft: Grumman G-164-A, registration: N910X
Injuries: 1 Uninjured.

NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

After the third aerial application pass, the airplane's engine developed a severe vibration, then seized. The pilot dropped the chemical load, turned the airplane into the wind, and made a forced landing into a cranberry bog. Afterwards, the pilot reported that had he had felt no binding when he pulled the propeller through, to check for hydraulic lock during the preflight. He also stated that the airplane hadn't seemed to be developing full power for about a week prior to the accident. During the post-accident engine teardown, an upper (number 9) cylinder was removed, and a broken connecting rod was found. Metallurgical examination of the connecting rod fragments revealed well-defined crack arrest positions, indicative of fatigue, on the smaller fragment. The fracture features within the fatigue region were relatively uneven, and in several locations, the fatigue crack appeared to have extended in overstress. There were no visible metallurgical defects in the initiation area. The larger fragment contained features typical of an overstress. According Advisory Circular 65-12A, a partial hydraulic lock could cause a 'slightly bent connecting rod,' which could go unnoticed, but would be 'sure to fail later.' Upper cylinders on high wing aircraft have been known to be susceptible to hydraulic lock due to a leaking fuel primer.

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

The failure of the number 9 cylinder connecting rod, due to a primer leak initiation of a partial hydraulic lock. A factor in the accident was the unsuitable terrain, to which the forced landing had to be made.

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