LAX94LA133

The airplane sustained a total loss of engine power shortly after departing a privately owned airstrip. The pilot executed an emergency landing on a plowed field. The airplane nosed over during the landing roll. The engine examination revealed that the no. 1 cylinder failed in fatigue originating at its spark plug holes. The cylinder head combustion signatures showed that the engine has been exposed to this operating condition for some time. The detonation resulted from too lean of a mixture.

On February 23, 1994, at 1510 hours Pacific standard time, a Schweizer G-164B, N36265, sustained a total loss of power shortly after departing a privately owned airstrip about 3 miles southwest of Clarksburg, California. The airplane nosed over in the plowed field during emergency landing. The pilot was en route to a farm area to begin a local visual flight rules aerial application flight under Title 14 CFR Part 137. The airplane, operated by Growers Air Service, Woodland, California, sustained substantial damage. The certificated commercial pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed. The flight originated at the Heringer Ranch Airstrip, Clarksburg, California, at 1508 hours.

National Transportation Safety Board investigators examined the engine at Aero Engines, Los Angeles, California, on March 31, 1994.

The engine did not display major ground impact damage. Safety Board investigators found about a 2-inch by 3-inch hole on the side of the No. 5 cylinder skirt. The upper area of the cylinder skirt was torn in an upward direction.

The No. 1 cylinder head was found split in half. The fracture surfaces displayed a 45-degree angle plane consistent with an overload fracture. The fracture surface also displayed two, 1/4-inch diameter combustion signatures. The examination revealed evidence of detonation in the cylinder head over a period of time.

The No. 1 cylinder head contained a 1/4-inch mark around its circumference. This mark corresponded with the piston's outer circumference.

The Nos. 1 and 5 cylinder rods separated near their respective piston pins; the remaining connecting rods separated from their respective retaining bushings. All of the connecting rods displayed massive internal rotational impact damage. The remaining No. 5 connecting rod was found at the No. 7 cylinder position.

The fracture surfaces of the Nos. 1 and 5 connecting rods sustained massive impact smudging. This smudging prevented any metallurgical analysis from being conducted to detect the origin(s) of their failure.