PLAINS, GA, USA
N2362D
AIR TRACTOR AT-301
During the first spray run of an aerial application flight, the engine lost power. Subsequently, the aircraft nosed over during a forced landing and was damaged. An examination of the engine revealed that the number four cylinder rocker arm housing had fractured. The fracture surface had a rough, granular, and irregular appearance, typical of overload failure. There was evidence that when the rocker arm housing became separated from the cylinder, the rocker arm pin failed, allowing the rocker arm to separate from the cylinder and resulting in a loss of continuity to the exhaust valve. The exhaust valve then remained closed, and the engine lost power.
On September 16, 1995, about 1130 eastern daylight time, an Air Tractor AT-301, N2362D, nosed over during a forced landing near Plains, Georgia. The airplane was operated by Gosa's Aerial Ag under the provisions of 14 CFR Part 137, and visual flight rules. Visual meteorological conditions prevailed. A flight plan was not filed for the aerial application flight. The commercial pilot had minor injuries, and the airplane was substantially damaged. Origination of the flight was a local private field, about 15 minutes prior to the accident. According to the pilot, he was conducting the first spray run when the engine lost power. The pilot maneuvered the airplane to execute a forced landing into an empty pasture. The airplane landed hard, then nosed over during the landing roll, and was substantially damaged. The engine, a P & W R1340, had been overhauled about 25.6 flight hours prior to the accident. The functional engine exam revealed that the number four cylinder rocker arm housing had fractured. In the detailed photos provided by United States Aviation Underwriters, Inc. the fracture surface had a rough, granular, and irregular appearance. The engine's total hours and number of overhauls could not be determined from the aircraft records that were provided. The operator's report of the accident did list the total hours.
Failure of the number four cylinder rocker arm housing and pin, which resulted in a closed exhaust valve and loss of engine power.
Source: NTSB Aviation Accident Database
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