On October 10, 1998, at 1711 eastern daylight time, an experimental homebuilt RV-4 airplane, N741WB, collided with the ground near Apopka, Florida, while performing an aerobatics maneuver. The personal flight was operated by the pilot under the provisions of Title 14 CFR Part 91, with no flight plan filed. Visual meteorological conditions prevailed at the time of the accident. Examination of the airplane at the accident site revealed substantial airframe damage. The private pilot and passenger were fatally injured. The flight departed Bob White Field, in Zellwood, Florida, at 1515. Witnesses located in the immediate vicinity of the accident site observed the airplane as it entered a loop at a low altitude. As the airplane entered the bottom of the maneuver, the airplane became erratic, partially spun, and collided with the ground in a nose down attitude. According to witnesses, the engine continued to operate throughout the maneuver. Strong fuel fumes existed at the accident site following the impact. Examination of the accident site by a Federal Aviation Administration (FAA) inspector revealed the airplane fuselage, wing assembly, and empennage were attached to the airframe. Debris from the airplane was distributed evenly around the impact zone in a 360-degree pattern. The airplane was found in a flat attitude with the wing assembly leading edges bent upwards approximately 30 degrees. The fuselage was fractured on the left side aft of the main wing, all control cables were intact, the fuel selector was found in the on position, and the fuel tanks appeared to be ruptured from impact. Examination of the airframe and engine assembly failed to disclose a mechanical problem. The toxicological examinations performed on the pilot were negative for carbon monoxide, cyanide, ethanol, or drugs.