On October 3, 1998, approximately 1815 eastern daylight time, a Navion A, N4285K, being flown by a private pilot, was substantially damaged when it collided with trees during a forced landing following a total loss of power near the Jaffrey Airport (AFN), Jaffrey, New Hampshire. The pilot was not injured. Visual meteorological conditions prevailed, and a flight plan had not been filed. The personal flight was to have been conducted under 14 CFR Part 91, and originated at Mansfield airport (1B9), Mansfield, Massachusetts, about 1540. The pilot reported that he departed Mansfield after conducting a preflight of the aircraft and that "I checked the fuel in the main tanks seeing that I had 40 gallons in the two main tanks. I did not check the auxiliary tank." After departing Mansfield, he flew to Jaffrey (straight line distance 69 statute miles [refer to CHART I]) and then landed. He reported that after his arrival and subsequent departure from Jaffrey he "flew around the area and the lakes region of New Hampshire for approximately two hours" and further stated that "after landing I did not shut the plane down" and "I did not check the tanks visually." Additionally, the pilot reported that that there was no mechanical malfunction with the airplane (refer to attached NTSB form 6120.1/2). The pilot reported in a telephonic interview with the investigator-in-charge that he departed Mansfield approximately 1500 and did not refuel at Jaffrey, because when he completed his preflight inspection at Mansfield, he thought the auxiliary tank was full, and based on a fuel consumption of about 16 gallons per hour, he should have had adequate fuel to return to Mansfield. The total fuel capacity of the auxiliary tank was 20 gallons, and the combined total fuel capacity for the main tanks was 40 gallons. He further reported that when the engine lost power shortly after he leveled off at 3,000 feet MSL, he completed the emergency checklist which included switching to the auxiliary tank (the fuel selector had been positioned to the main tanks for departure). He realized that he did not have enough altitude to make the runway, so he elected to land in a field. As he got closer to the field, he noticed that it was unsuitable, so he decided to land the airplane in the tree tops. He reported that the gear and flaps were retracted as the aircraft mushed into the trees, and the airplane came to rest in a nose down attitude, with the tail up in the trees. Post-crash examination of the aircraft by an inspector from the Federal Aviation Administration's Portland, Maine, Flight Standards District Office revealed no fuel in the aircraft's fuel tanks, and no evidence of fuel leakage. The pilot concluded in his submitted NTSB Form 6120.1/2 (attached) that "Due to the power setting I chose to run the aircraft at, the length of the flight, and my negligence to visually check and only operate the aircraft based on the fuel gauge readings, I believe that it was my mistake in exhausting the fuel."