Accident Overview
On July 17, 2012, at approximately 2000 central daylight time, a Grumman G-164A airplane (registration N4638) was substantially damaged during a forced landing to a corn field following a loss of engine power near Fergus Falls, Minnesota. The commercial pilot, the sole occupant, was not injured. The aircraft was registered to and operated by West Central AG-AIR Incorporated of Fergus Falls, Minnesota. Visual meteorological conditions prevailed for the agricultural flight conducted under 14 Code of Federal Regulations Part 137.
Flight and Incident
The flight originated from Wheaton Municipal Airport (ETH) in Wheaton, Minnesota, at approximately 1945. The pilot reported that during his fifth spraying pass, he observed a puff of white smoke emanating from the engine. He shut off the chemical sprayer and oriented the aircraft toward a road. Midway through the turn, the pilot noticed additional smoke followed by a complete loss of engine power. He jettisoned the chemical load and executed a forced landing in a corn field. After touchdown, the airplane nosed over, resulting in substantial damage to the upper wings, rudder, and vertical stabilizer.
Post-Accident Examination
A Federal Aviation Administration (FAA) Airworthiness inspector examined the Pratt & Whitney R1340 radial engine and found that the No. 2 cylinder head was cracked.
Maintenance Records
Review of the maintenance logbooks revealed that FAA Airworthiness Directive (AD) 99-11-02, which mandates a 100-hour visual inspection of cylinder heads for cracking, was complied with at the last annual inspection. No entries indicated that cracks were observed during that inspection. Further review showed that the AD had not been complied with for 253 hours prior to the annual inspection.