The airplane was destroyed when it impacted a gravel quarry shortly after a departure at about 1017 Eastern time. The Commercial pilot was fatally injured. Visual conditions prevailed for the local glider towing flight. According to a student glider pilot who was being towed by the accident airplane, it was his third tow of the day. He stated they departed from Runway 17 and performed a 45-degree left turn simultaneously. About 30 feet above the ground, the student pilot noticed that the tow rope had some slack in it. After applying a correction, the student pilot noticed that the tow plane did not appear to be climbing well, and the tow rope went slack again at 150-200 feet above the ground. The glider pilot then decided to release from the tow plane. During the turn, he observed the airplane drop the left wing slightly, and then begin a turn to the right. The airplane then impacted a quarry, and a post-crash fire ensued. The student pilot added that during a previous flight with the tow pilot, the airplane began to descend when the pilot failed to realize that the throttle was retarded during a climb.