On March 28, 2002, approximately 0935 central standard time, a Grumman-Schweizwer G-164B agricultural airplane, N8498K, sustained substantial damage when it impacted terrain while maneuvering near Ferriday, Louisiana. The commercial pilot, sole occupant of the airplane, was not injured. The airplane was being operated by W&E Air Service, Ferriday, Louisiana, under 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed for the local aerial application flight, and a flight plan was not filed. The flight originated from the W&E Air Service private airstrip at 0920. In a telephone interview with the NTSB investigator-in-charge, the pilot reported that this was his third load of the day. While turning back to the field after completing a spray run, the engine started "popping." After several more "pops," the engine "went dead." The pilot landed straight ahead in the open cotton field he was spraying, impacting soft terrain. After impact, the left landing gear separated, and the airplane continued for approximately 20 yards before flipping over, coming to rest inverted. An A&P mechanic, who examined the aircraft, reported that the #3 cylinder exhaust rocker arm had failed. The front and rear spars of the right upper wing panel, and the front spar of the left lower wing panel sustained structural damage. All four wing panels sustained leading edge and skin damage. The vertical stabilizer, rudder, and right elevator were destroyed.