On January 27, 1998, at 1350 central standard time, a Sutton Tierra II experimental airplane, N131WH, was substantially damaged following a loss of control while maneuvering near Woodson, Arkansas. The private pilot, sole occupant of the airplane, was seriously injured. The airplane was owned and operated by the pilot under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the local flight for which a flight plan was not filed. The personal flight originated from the Pumpkin Patch Airport, near Woodson, Arkansas, approximately 10 minutes prior to the accident. The pilot told individuals responding to the accident site, that the airplane "entered a steep right turn from which he was unable to pull the airplane out, so he elected to shut the engine off in order to attempt to get out of it." The pilot's wife was the first person to respond to the accident site. She was told by her husband that prior to his loss of control, "he thought he heard the left wing strut snap." During an earlier flight, the pilot performed a short flight to check the accuracy of the airspeed indicator after he had removed a 6-inch portion of the pitot tube to attempt to correct existing airspeed inaccuracies. During that flight the pilot contacted his wife on the radio and reported that the inaccuracies had been resolved. The pilot's wife reported to the FAA inspector that the pilot elected to execute another short flight to further verify the accuracy of the airspeed indicator. The pilot's wife further reported that she observed the airplane over the airport at approximately 150 feet above the ground, suddenly roll into a 50 degree bank to the right as she continued to observe the airplane enter a right spiraling turn until impact with the ground. Examination of the wreckage by the FAA inspector did not revealed any pre-existing anomalies or discontinuities that would have prevented normal operation of the homebuilt airplane. The FAA inspector stated that physical evidence at the accident site indicated that the airplane impacted the muddy field in a left turn in a nose down attitude. The manufacturer of the kit-built airplane reported to have traveled to the pilot's residence to examine the wreckage. The manufacturer stated that he was denied access to the wreckage. Repeated attempts to obtain a completed NTSB Form 6120.1/2 from the pilot were unsuccessful.