The flight instructor reported that he and the private pilot receiving instruction had just completed their seventh landing of the morning. The private pilot reduced the throttle on downwind and the landing gear warning horn sounded so he increased the throttle and continued in the traffic pattern. The flight instructor prompted him to extend the flaps and the student stated that he would extend the landing gear. They “confirmed 3 green,” which would indicate that the landing gear was down and locked. During the landing flare, “no gear warning horn was alarming,” but as they got closer to the ground the instructor observed sparks out of the left window. The airplane slid on the runway, came to rest upright, and sustained substantial damage to the lower fuselage longerons. The Federal Aviation Administration (FAA) inspector completed an extensive examination and functional testing of the landing gear system. With the airplane on jacks, he cycled the landing gear at least six times and determined the landing gear, warning annunciations and aural alerts operated per the procedures in the airplane’s maintenance manual and there were no anomalies found.