On November 18, 1993, at approximately 1045 hours Pacific standard time (PST), an Aero Commander S2R, N8818Q, registered to/operated by Air Trac, Inc., and being flown by Gerald R. Titus, a certificated commercial pilot, was destroyed during a collision with an irrigation sprinkler system and terrain. The pilot sustained minor injuries. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was to be conducted for the purposes of aerial application, was to have been operated in accordance with the requirements of 14CFR137 and departed from Carr Airport, near Pasco, Washington, at approximately 1030 hours. The pilot reported that following a pullup from a spray run and transition to straight and level flight, he "heard a sequence of noise(s), (the) aircraft controls became useless and (the) aircraft impacted the ground." On site examination revealed black rubber smears on the irrigation sprinkler support structure, and one of the main wheels was observed on the ground a short distance from the damaged sprinkler section and in line with the wreckage distribution track (refer to photograph 1).