On April 9, 1996, at 1330 mountain daylight time, a Weatherly 620, N46139, ground looped into a ditch during an emergency landing near Akron, Colorado. The commercial pilot was not injured and the aircraft sustained substantial damage. The flight was a local aerial application flight operating under Title 14 CFR Part 137 and no flight plan was filed. Visual meteorological conditions prevailed. The flight departed Akron at 1245. According to the pilot, while conducting a swath run, the engine started to run rough followed by a catastrophic failure of the number two cylinder, part of which penetrated the windscreen. The pilot said he attempted an emergency landing on a road next to the field he was spraying. During the landing roll, the aircraft ground looped into a ditch when a wing tip caught on a fence. Visibility from the cockpit was limited due to damage to the windscreen and oil which covered the surface. Inspection of the aircraft by an FAA inspector revealed that the number 2 cylinder separated at the mounting bolts and all bolts were pulled out. No evidence was found to indicate the reason for the cylinder failure. The logs indicated that the engine had been through overhaul 885 hours prior to the accident flight.