On July 30, 2016, about 1147 central daylight time, a Rans S7 airplane, N6271X, impacted terrain shortly after takeoff from the Wittman Regional Airport (KOSH), Oshkosh, Wisconsin. The airplane sustained substantial damage to the wing struts and fuselage, and the sport pilot was not injured. The airplane was privately registered and operated under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight. Day visual meteorological conditions prevailed for the flight, and no flight plan was filed. The pilot stated that after camping for a few days at the Experimental Aircraft Association's AirVenture, he decided to head to Ames, Iowa. He finished packing and preflighted the outside of the airplane, but not the inside. After the preflight and engine start sequence, he ground maneuvered his airplane to indicate he was ready to depart, and a flight line marshal came to his airplane to escort him out of the parking area. The pilot stated that during taxi, the tailwheel of the airplane seemed to have some trouble tracking, giving the brakes "a real work out, and causing his airplane to run slower than the other aircraft." The pilot stated that while taxiing, he was also trying to get the airplane set-up for takeoff. The pilot was cleared for takeoff from runway 36, and he accelerated the engine to full throttle. He reported that during the takeoff roll, "the tail came up, the gear got soft," and he put back pressure on the stick. He reported that "something was very wrong" as the nose pitched up into a high attitude that was indicative of a stall. The pilot pushed forward on the stick, and the airplane began to drift left. He saw the people on the flight line, airplanes on the taxiway and made the decision to make an abrupt turn to the right to cause an aerodynamic stall. The airplane impacted the ground on the west side of the runway. The pilot reported feeling very rushed and anxious because of all the timing issues given the number of people trying to land and takeoff. He reported that it would have been helpful to complete an "in cabin" preflight checklist prior to takeoff. Examination of the airplane after the accident by the National Transportation Safety Board (NTSB) investigator-in-charge and a Federal Aviation Administration (FAA) inspector revealed flight control continuity was established to all controls. The elevator trim was found in the takeoff position. All items in the airplane were weighed, and the airplane weight and balance was calculated with a takeoff weight of 1,049 lbs; the maximum takeoff weight was 1,200 lbs. The airplane center of gravity was 77.8 inches; the airplane's center of gravity envelope was 74 to 81-inches. The baggage area weight was 60 lbs which was above the placarded "maximum baggage 50 LBS." The pilot reported and the examination revealed there were no preimpact mechanical malfunctions or failures with the airframe or engine that would have precluded normal operation. The pilot was color blind, and had been diagnosed with Crohn's disease, low back pain, insomnia as well as Parkinson's disease. His last FAA airman medical certificate was issued in 1972. According to his personal medical records, his medications at the time of the accident included baby aspirin, a combination of diphenhydramine and acetaminophen at night for sleep, mesalamine for the Crohn's disease, rasagiline mesylate, pramipexole, a combination of carbidopa and levodopa, and amantadine for his Parkinson's disease. Sudden periods of sleep may be caused by 4 of these medications. Finally, he was using a 1% solution of atropine orally to treat excessive drooling as needed. The musculoskeletal symptoms including tremor and rigidity of his Parkinson's were somewhat alleviated but not eliminated by his use of medications; in April 2016, his score on the motor portion of the Unified Parkinson's Disease Rating Scale was 18. In addition, his health care provider documented that his tremors became worse when he was nervous and that he was beginning to have some mild cognitive issues. No post-accident toxicology testing was performed. Two of the pilot's medications were medically disqualifying for an FAA airman medical certification because they depress the central nervous system. However, a sport pilot is not required to hold a FAA airman medical certificate and can use a U.S. driver's license to meet the medical requirements. When using a U.S. driver's license, the sport pilot must self-certify that they "do not know or have reason to know of any medical condition that would make that person unable to operate a light-sport aircraft in a safe manner." Therefore, the FAA is not involved with medical disqualification when a U.S. driver's license is used in lieu of an FAA airman medical certificate.