The Flight
On October 19, 2012, at approximately 1300 eastern daylight time, a Grumman-Schweizer G-164B (registration N6670K) was operating as an aerial application flight under 14 CFR Part 137. The flight departed from the pilot's private airstrip for local operations. Visual meteorological conditions prevailed, and no flight plan was filed.
The Accident
According to the pilot, he had completed one application pass over a cotton field, pitched up, and was planning a 180-degree turn for a second pass when the engine lost all power. He attempted to maximize the airplane's energy to reach a peanut field for a forced landing but ultimately determined that the only available option was a cornfield. During the landing rollout in the cornfield, the airplane nosed over. The defoliant saturated the cockpit. The pilot reported that the power loss felt similar to losing a cylinder.
Post-Accident Inspection
A Federal Aviation Administration inspector examined the accident site. The airplane had nosed over after landing in a cornfield with sandy terrain. Ground tracks from the initial touchdown point to the wreckage measured 425 feet in length. The airplane sustained substantial damage to the fuselage and tail. The pilot sustained minor injuries.
Engine Examination
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 could not be rotated. The No. 8 cylinder linkpin strap and approximately 2 inches of the rod beam were present. The No. 1 cylinder linkrod was not connected to the K-Pin through the No. 8 cylinder mounting flange hole. The front half of the K-Pin was absent from the master rod assembly; the rear half and its safety were in place. The front half was found inside the power case after removal of the top case half, but all surfaces exhibited extensive damage. The K-Pin was fractured through the center of the mid-journal oil-holes. The cylinder assemblies extended into the power case area and were flared out. Cylinders 1, 8, and 9 were removed using various methods. The piston associated with the No. 1 cylinder was found approximately two-thirds of the way up the bore, with the piston surfaces facing the crankshaft showing minimal damage compared to other pistons. The remaining portion of the No. 1 cylinder K-Pin was removed, and the hole size was checked; the front flange measured 0.001 inches out-of-round. A review of the pin size and the illustrated parts manual indicated the pin was original. There was no evidence of oil starvation on any engine components.
Maintenance Records
Maintenance records showed the engine was overhauled on May 29, 2012, and had accumulated 307 operating hours since overhaul. Total engine time in service was 11,466.8 hours.