On June 22, 1997, at 0930 eastern daylight time, a Cessna 172, N4491R, operated by a certified flight instructor (CFI) collided with the runway while landing at the Grosse Ile Municipal Airport, Grosse Ile, Michigan. Neither the CFI or student pilot were injured. The airplane was substantially damaged. Visual meteorological conditions prevailed and no flight plan was filed. The training flight was being conducted under 14 CFR Part 91. The local flight originated at 0830 edt. In a statement, the pilot said he was demonstrating slow flight to the student while flying in ground effect over the runway. He indicated that the flaps were fully extended (40 degrees) and the power was just enough to sustain flying airspeed. At an altitude of approximately 5 feet above ground level (AGL), the left wing dipped. The left wing tip and main gear contacted the runway at which time the airplane sustained substantial damage. According to the pilot, his intent was to show the student that the airplane would still be controllable while flying at a slow airspeed in ground effect. The pilot added that during the maneuver he let the airplane get away from him.