On May 22, 2001, approximately 1700 Pacific daylight time, a Piper PA-22-150, N7815D, registered to and operated by the private pilot as a 14 CFR Part 91 personal flight, collided with trees during the takeoff climb from a private airstrip seven miles southwest of Sunriver, Oregon. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft was substantially damaged and the private pilot and his passenger received minor injuries. In a written statement, the pilot reported that the takeoff was on runway 4, a 3,600 foot long private dirt airstrip at an elevation of 4,300 feet mean sea level. The aircraft lifted off in about 1,900 feet, and at this time the pilot extended full flaps and the aircraft achieved an ascent rate of about 500 feet per minute. About 3,100 feet down the airstrip, the aircraft attained an altitude to clear the surrounding trees, but then shortly thereafter, decreased altitude by 20 to 30 feet and the airspeed dropped about 15 to 20 miles per hour. There was not sufficient runway left to land the aircraft so the pilot continued the takeoff climb. The tree line was lower to the south and the pilot turned the aircraft slightly in an attempt to avoid colliding with trees. The tail of the aircraft collided with a tree and the aircraft turned to the right and subsequently collided with the ground. The pilot reported that there were no mechanical failures or malfunctions with the aircraft at the time of the accident.