NTSB Factual Report

On October 19, 2012, about 1300 eastern daylight time, a Grumman-Schweizer G-164B, N6670K, was substantially damaged after it nosed over during an off airport landing in a corn field near Edison, Georgia. The commercial pilot sustained minor injuries. The airplane sustained substantial damage to the fuselage and tail. The airplane was operated under the provisions of Title 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed and no flight plan was filed for the local aerial application flight. The flight originated from the pilot's private airstrip.

According to the pilot, he made one application pass across a cotton field, pitched up, and planned on turning 180 degrees to begin a second application pass. The engine lost total power and he attempted to maximize the airplane’s energy in order to complete a forced landing in a nearby peanut field. Subsequently, the pilot realized that the only option was to land in the nearby cornfield. During the landing roll out the airplane nosed over and the defoliant saturated the cockpit. He further reported that the power loss was similar to losing one of the cylinders.

According to the airplane maintenance records, the engine was overhauled on May 29, 2012, and was operated for 307 total hours since the overhaul. The engine's total time in service was 11,466.8 hours.

Initial examination of the accident site by a Federal Aviation Administration inspector revealed that the airplane nosed over after landing in a cornfield and the terrain was sandy in nature. He further reported that ground tracks were visible from the initial touchdown point to the wreckage and measured 425 feet in length.

The engine was examined at a facility in Oklahoma. Initial examination revealed that Cylinder No. 7 was loose from the power case studs. The governor drive gear was unable to be rotated. The No. 8 cylinder linkpin strap and approximately 2 inches of the rod beam were present. The No. 1 cylinder linkrod was observed not connected to the K-Pin through the No. 8 cylinder mounting flange hole. The front approximate one-half of the K-Pin was absent from the masterod assembly, the rear half of the K-Pin and its safety were found in place and the front half of the K-Pin was found inside the power case after the top case half was removed; however, all surfaces exhibited extensive damage. The K-Pin was fractured through the center of the mid-journal oil-holes. Examination further revealed that the cylinder assemblies extended into the power case area and had been flared out. Cylinder Nos. 1, 8, and 9 were removed using various methods. The piston associated with the No. 1 cylinder was found approximately two-thirds of the length of the stroke up the bore of the cylinder and the No 1 piston surfaces facing the crankshaft had minimal damage when compared to all other pistons. The remaining portion of the No. 1 cylinder K-Pin was removed and the hole size was checked. The front flange was measured at 0.001 inches out-of-round. In a review of the pin size and the illustrated parts manual the pin did not exhibit any indication that it was anything other than the original pin. There was no evidence throughout the engine of oil starvation on any of the components.

NTSB Probable Cause

The total loss of engine power due to the fatigue failure of the k-pin associated with the No. 1 cylinder.