On September 29, 2004, about 1030 central daylight time, a Piper PA-12, N7977H, piloted by a flight instructor and dual student, was substantially damaged during an in-flight collision with terrain after takeoff from runway 12 (4,100 feet by 75 feet, asphalt) at Perham Municipal Airport (16D), Perham, Minnesota. The instructional flight was being conducted under 14 CFR Part 91 without a flight plan. Visual meteorological conditions prevailed. The dual student sustained minor injuries and the flight instructor was not injured. The local flight was originating at the time of the accident. The flight instructor reported in his written statement that the accident flight was to be the dual student's second training session in preparation for a seaplane rating. He noted that the preflight inspection prior to the accident flight was normal. The flight instructor stated that the airplane lifted off about 62 miles per hour (mph) and "assumed [a] nose up attitude." He noted that rotation was about 7 mph faster than normal. He stated: The airplane "did not want to climb out of ground effect, upon pulling back further on the elevator something was preventing the full travel of the stick." He reported that about 1,000 feet down the runway the dual student applied too much left rudder causing a skidding turn to the left. He noted that the airplane's heading was approximately 30 degrees from the runway heading at this point. He was reportedly unable to obtain more elevator travel and correct the skid prior to impact with the ground. In post-accident conversations, the flight instructor stated it was his belief that elevator travel was limited at the time of the accident due to something being stuck in the control system. In addition, he noted that the aircraft was nose heavy subsequent to the installation of amphibious floats about four months prior to the accident. He stated that on previous flights he compensated for the increased nose heaviness by maintaining additional airspeed into the landing flare. The dual student was flying the aircraft. In his written statement he noted that the takeoff was initiated with a right crosswind. He stated that takeoff rotation was normal at 62 mph. He reported that the airplane subsequently "weathervaned" into the wind and he "induced cross controls" in order to track the runway centerline. The dual student stated that about 50 feet above ground level (agl) the aircraft began to sink and drifted toward the left infield, where it impacted the ground "in a somewhat wings level" attitude. The airplane came to rest inverted. In post-accident interviews with Federal Aviation Administration (FAA) inspectors, the dual student reported that he had used right rudder inputs to compensate for the right crosswind condition. FAA inspectors conducted a post-accident inspection of the accident site and the accident aircraft. They noted that ruts in the grass leading to the wreckage site departed the runway pavement about 850 feet from the takeoff end and were angled approximately 45 degrees relative to the centerline. Elevator control continuity was confirmed during the aircraft inspection. No blockage or restriction of the elevator was observed. Maintenance records indicated that the airplane was disassembled and rebuilt in June 2002. At that time, records show that the aircraft elevator control system was modified to incorporate certain PA-18 provisions in accordance with Supplemental Type Certificate (STC) SA564AL. The STC was applicable only to landplanes because a conformity inspection was never performed on a float-equipped airplane. According to maintenance records, installation of amphibious floats was completed on May 28, 2004, by the manufacturer of the floats. This modification was completed according to STC SA00901CH. The float manufacturer noted that, according to the STC, compatibility with previous modifications was the responsibility of the installer. The logbook entry noted a tachometer time of 129.1 hours at the time of installation. The tachometer reportedly indicated 188 hours at the accident site. The flight instructor recalled winds at the time of the accident as being variable from the south at 10 knots, gusting to 15 knots. Winds recorded by the Detroit Lakes Airport (DTL) Automated Weather Observing System, located 18 miles northwest of 16D, at 1035, were from 180 degrees at 10 knots.