On July 20, 1995, at 1020 Pacific daylight time, a Margeson Vans RV-3 experimental homebuilt airplane, N18DT, collided with a cotton field following an in-flight loss of control near Corcoran, California. Ground witnesses reported observing the aircraft about 150 feet above the ground start a climb, turn rapidly to the left, and "cork-screw to the ground." The aircraft was owned and operated by the pilot. Visual meteorological conditions prevailed at the time and no flight plan was filed for the operation. The aircraft was destroyed in the ground collision sequence. The certificated private pilot, the sole occupant, sustained serious injuries. The flight originated at Bakersfield, California, on the morning of the accident about 0950 as the return portion of a cross-country round robin flight from Fresno to Bakersfield. The pilot's son was interviewed by Federal Aviation Administration (FAA) inspectors from the Fresno, California, Flight Standards District Office. The son said his father regained consciousness in the hospital and indicated that he had experienced a loss of engine power while cruising about 4,000 feet above the ground. He was attempting to make a forced landing in the area of the accident site when the accident occurred. A ground witness was driving on a highway and observed the aircraft gliding down towards a field. The witness said the aircraft started a climb from about 150 feet agl, then turned rapidly to the left and "cork-screwed to the ground." Responding Kings County Fire Department units found the pilot unconscious and trapped in the aircraft wreckage when they arrived. The front fuselage mounted fuel tank was noted to be ruptured. During attempts to extricate the pilot from the wreckage a fire erupted in the engine compartment. The fire department units extinguished the fire with a water spray. After recovery of the aircraft from the cotton field, the airframe and engine were examined by an FAA airworthiness inspector. In his report, he stated that he found no discrepancy in either the wreckage or the maintenance records. The Lycoming O-320 engine was removed from the airframe and sent to an FAA certified engine overhaul shop in Visalia, California, for evaluation. In their verbal and written reports, the overhaul shop reported that compression was noted in all cylinders, with accessory gear and valve train continuity established. Both magnetos were broken from their respective mount pads; however, tested satisfactorily. About a teaspoon of fuel was drained from the pressure carburetor, with a few drops of water noted in the fuel. The engine driven fuel pump was actuated and the residue pumped out; the contents were reported to be about 50 percent dirty water. No other engine system abnormality was found by the overhaul shop. The aircraft was last fueled just prior to departure from the Bakersfield Municipal Airport. Fueling records from the Fixed Base Operator (FBO) where the fuel was purchased disclosed that the pilot added 13.0 gallons of 100 LL aviation gasoline into the single fuselage mounted aircraft fuel tank. The assigned FAA inspector traveled to Bakersfield and examined the FBO's fueling facility and associated records. According to the inspector's report, the FBO purchases the fuel from a major refinery and it is dispensed through stationary pumps from an underground storage tank. The tank is checked weekly for water contamination and go/no-go filters are installed at the pumps. All system filters were clean. No problems have been reported from any aircraft fueled before or after the accident aircraft.