Accident Overview
On August 25, 2016, at approximately 1250 central daylight time, a Piper PA-25-235 single-engine airplane, registration N4963Y, was substantially damaged during an off-airport forced landing near Bushton, Kansas. The pilot, operating under Title 14 Code of Federal Regulations Part 137 for agricultural application, sustained serious injuries. The aircraft was registered to a private individual and operated by Wayne's Ag Aviation of Ellsworth, Kansas. The local flight had departed Ellsworth Municipal Airport (9K7) about 1130.
Flight and Forced Landing
Visual meteorological conditions prevailed at the time, and no flight plan had been filed. The pilot was applying pesticide to a field when a partial loss of engine power occurred, and the engine did not respond to throttle inputs. The pilot flew straight ahead, and the airplane collided with tall milo crops, coming to rest inverted. Post-accident, there was a fuel and pesticide leak, but no post-impact fire. There were no witnesses to the accident.
Engine Examination
Federal Aviation Administration (FAA) inspectors examined the engine on August 30, 2016. They reported finding no evidence of pre-impact catastrophic mechanical malfunction. Mechanical continuity was established during hand rotation of the crankshaft. The spark plug electrodes were mechanically undamaged and exhibited coloration consistent with normal operation. Spark was obtained from the magnetos. All fuel lines were secure and in place. Fuel consistent with the appearance and odor of aviation fuel was noted. The gascolator and carburetor fuel screens were clean. The throttle and mixture controls were securely attached at their control arms on the carburetor, and continuity to the cockpit was established. The air cleaner was free of foreign objects. The engine had straight pipes and no muffler.
According to the FAA "Carburetor Icing Prevention" chart, under the prevailing conditions, serious icing was possible at glide power.