On October 26, 1997, approximately 1550 Pacific standard time, a Beckham RV-4 experimental aircraft, N160HB, being flown by a private pilot, was destroyed during an inflight collision with terrain following a loss of control while in cruise near Scio, Oregon. The pilot was fatally injured. There was no fire. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was personal, was to have been operated under 14CFR91, and originated from the pilot's private airstrip several miles northeast of the accident site approximately 1530. According to a pilot eyewitness flying a Cessna 170 near the accident site, he "noticed an RV aircraft coming up on my left side. I wagged my wings and he wagged his wings back. He then proceeded to pass me on my left, when he was approximately at my 11 o'clock (position), he executed a roll to the left. At the inverted stage of the roll the aircraft dove straight into the ground." The witness reported that he was headed southwest at the time and estimated the height of the accident aircraft at the beginning of the dive as approximately 750 feet above ground. He also reported that he observed nothing depart the accident aircraft during the roll and descent. The responding Linn County Sheriff's deputy reported that upon arrival at the crash site he noted that the wreckage debris field was confined to an area less than 50 yards in diameter and that the airframe had "telescoped" vertically into the ground. An FAA inspector examined the wreckage and reported that a control system check revealed no evidence of mechanical disconnect or malfunction (refer to photographs 1 through 4). The 64 year-old pilot's last Class III medical had been issued on August 2, 1993, and the exam revealed no medical problems. However, a deputy from the Linn County Sheriff's Office, who interviewed the pilot's wife, reported that she had told him that "her husband has been have(ing) real bad migraine headaches that would leave him incapacitated." She also told the deputy that "he would blackout, and get tunnel vision" and that "sometimes they (the migraines) would get so bad, he could not talk." Refer to Linn County Sheriff's Office Incident Report #97-16438. Toxicological evaluation of samples taken from the pilot revealed only contaminants characteristic of post-mortem alcohol production (refer to attached report).