On July 10, 2012, about 0700 mountain daylight time, a Cessna A188B, N4831R, was substantially damaged when it struck a power line and subsequently impacted terrain near Cheyenne, Wyoming. The commercial pilot, the sole occupant, was seriously injured. The airplane was being operated by Circle S Aviation LLC under the provisions of 14 Code of Federal Regulations Part 137. A flight plan had not been filed for the local aerial application flight, which had originated from Pine Bluffs, Wyoming, about 50 minutes before the accident. Visual meteorological conditions prevailed at the time of the accident. According to the operator, this was the pilot's first season for conducting aerial applications. He was applying a mosquito eradication substance to a river bottom. He was flying eastbound, and the sun was at an altitude of 25.9 degrees and an azimuth of 83.4 degrees east of north. A north-south oriented power line crossed the airplane's flight path. The airplane's right wing struck one of the power line's support poles and its left main landing gear became entangled with two aluminum transmission wires. The airplane impacted the ground, nosed over and came to rest inverted. A postimpact fire consumed the airplane's fuselage and right wing.