On November 20, 2002, at 1400 central daylight time, an Air Tractor AT-502 agricultural airplane, N502RS, registered to and operated by Keller Flying Service Inc., of Weiner, Arkansas, was substantially damaged during a forced landing after a loss of engine power during initial climb after takeoff from Keller Airfield, near Weiner, Arkansas. The commercial pilot sustained serious injuries and his passenger sustained minor injuries. Visual meteorological conditions prevailed and a flight plan was not filed for the Title 14 Code of Federal Regulations Part 91 personal flight. The local flight was originating at the time of the accident. According to information provided in the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) and in a telephone interview with the NTSB investigator-in-charge, the pilot reported that the engine "developed a compressor stall" just after takeoff while climbing through 120 feet AGL. After the loss of power, the pilot "nosed the aircraft down" to gain airspeed, then attempted to level the airplane by "dumping the flaps". Subsequently, the airplane's landing gear contacted the "soft" ground and "dug in." The airplane then nosed over resulting in structural damage to the fuselage. The reason for the compressor stall and loss of power could not be determined.