Takeoff Attempts Overview
The pilot initiated two takeoff runs from the same runway. During both attempts, the airplane was observed to be nose-high, flying at low speed in ground effect. On the first attempt, the pilot reduced power and landed, aborting the takeoff. For the second attempt, the airplane became airborne approximately one-third of the way down the runway, maintaining a nose-high attitude and slow airspeed while remaining in ground effect. About two-thirds of the way down the runway, it had climbed to an altitude of 10 to 15 feet. At that point, the airplane developed a pitch oscillation. The airplane continued past the end of the runway and impacted the ground.
Pilot's Account
The pilot reported that the engine ran smoothly during both takeoff attempts. However, the engine speed reached only 2,400 RPM, whereas the specified takeoff RPM was 2,700. Despite the lower power output, the pilot proceeded with the second takeoff.
Conclusion
The source does not provide a probable cause for the accident.