The pilot reported he departed from the airport to practice a short takeoff and landing (commonly known as “STOL”) race circuit in preparation for a race that was going to occur at the airport. As the pilot was on approach for landing, he noticed the wind speed had increased while he was turning base to final at 60 ft agl. The pilot had a 16-mph buffer above the airplane’s aerodynamic stall speed, with two notches of flaps applied, and a 15° bank turn. The airplane was then “hit by a gust” that elevated the right wing to about 30° of bank. The pilot attempted to correct the high bank angle with no success. He reported “all of my lift disappeared,” and the airplane became uncontrollable at about 55 ft agl. The pilot concluded that a “large tail wind shear” aerodynamically stalled the airplane, and he was unable to recover at the low altitude with the various obstacles and structures present on the STOL race circuit course. The airplane “pancaked” and came to rest upright in a field, next to a fence line. The airplane sustained substantial damage to the fuselage and both wings. The pilot reported there were no preimpact mechanical malfunctions or failures with the airframe and engine that would have precluded normal operation. A review of meteorological data showed that gusting wind conditions and low-level wind shear were likely present in the area at the time of the accident.