Accident Details
On June 12, 2014, at approximately 1200 central daylight time, an Air Tractor AT 301, registration N8593S, experienced a loss of engine power while conducting an aerial application flight near Pearsall, Texas. The pilot, the sole occupant, executed a forced landing in a field. The pilot was not injured, but the airplane sustained substantial damage. Visual meteorological conditions prevailed at the time, and no flight plan had been filed. The flight had originated from Pearsall about 1140.
Pilot Report
According to the pilot, after spraying a corn field, he returned to the airport and noticed the cylinder head temperature was high. Upon landing, he checked the engine cylinders for discrepancies but found none, so he decided to continue spraying. He took off and returned to the corn field. As he pulled up from a spray run, the engine began to vibrate and lose power, necessitating the forced landing in a nearby field. Inspection of the airplane revealed substantial damage to both wings during the landing.
Engine Examination
The operator reported that the engine had accumulated approximately 11 hours since undergoing extensive maintenance, which included replacement of a crankshaft. The engine was shipped to Tulsa Engines in Tulsa, Oklahoma, where on September 3, it was partially disassembled and examined under the oversight of a Federal Aviation Administration inspector. The inspector's report noted a large amount of metal in the oil drain. The number 2 cylinder front spark plug was found to be loose. After removing all spark plugs, an attempt to rotate the engine was unsuccessful as it was seized. Cylinders 4, 5, 6, and 7 contained oil, with cylinder 4 having more oil than the others. Upon removal of the number 1 cylinder, the piston rod was found broken at the link pin. No other rods were broken. The link pin exhibited scoring and there was evidence of oil starvation of the rod bearing.