NTSB Identification: FTW00LA168.
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Accident occurred Thursday, June 01, 2000 in GARWOOD, TX
Probable Cause Approval Date: 07/17/2001
Aircraft: Air Tractor AT-301, registration: N8886S
Injuries: 1 Fatal.
NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The commercial pilot had dispensed his 4th load of fertilizer for the day and was returning to the airstrip, when he reported a vibration, followed by a loss of engine power. During the forced landing, another pilot observed the airplane hit a ditch between two rice fields, and then nose over. The integrity of the fuel system was not compromised during the impact sequence. There was no evidence of fuel found at the accident site during an examination the day after the accident. Fuel stains were found on the bottom of the right wing. During an engine test run, the engine ran rough, backfiring, and cutting out momentarily throughout the normal power range. When the engine was run at power, on only the left magneto, the engine maintained 28 inches of manifold pressure at 2,000 RPM; however, it would still cut out from time to time. Removal and examination of the right magneto revealed that the internal brass gear splines were worn and brass particles were scattered within the magneto. Removal, bench testing, and examination of the carburetor revealed that the float movement was rough, the orifice of the float valve was too large, the float was set too low, and the accelerator pump did not work well. The carburetor had been removed, overhauled, reinstalled, and returned to service approximately 3 weeks prior to the accident. The seat belt and shoulder harness were found fastened, and the pilot was wearing his helmet. The curved overturn tube, located in the upper portion of the cockpit, was crushed inward. According to the manufacturer representative, a service bulletin was issued on March 23, 1991, for the installation of a cockpit overturn skid plate as an added safety feature. The skid plate had not been installed in the accident aircraft.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: the loss of engine power in cruise flight as a result of the failure of the right magneto. A contributing factor was the lack of suitable terrain for the forced landing. Full narrative available
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