On April 15, 1995, at 1600 central daylight time, a Piper J-3 Cub, N6673H, registered to Belvidere Aviation Inc., of Popular Grove, Illinois, was substantially damaged while taxiing after landing at Belvidere Ltd Airport, Popular Grove, Illinois. Neither the certified flight instructor nor the commercial certificated student pilot reported injuries. The local 14 CFR Part 91 instructional flight operated in visual meteorological conditions without flight plan. The instructor stated that after the student pilot made a three point landing on runway 9, she began to turn the airplane to back taxi to the end of the runway to takeoff again by advancing the throttle and applying the left brake. As the airplane turned perpendicular to the runway, the instructor stated that the student had some difficultly "...getting the brake so I depressed it for her until she got it. I then released it." The throttle was still forward, and the airplane's tail began to lift off of the ground. The instructor pulled the throttle to the idle position, but he stated, "it appeared the wind got under the tail and continued to raise it." The propeller struck the ground and the airplane became inverted.