NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The private pilot was part of a formation of four airplanes making a cross-country flight during day visual meteorological conditions over a broken-to-overcast cloud layer. During the flight, the accident airplane, which was positioned left of the lead airplane, began drifting to the left of and behind the formation, which resulted in the lead pilot losing sight of the airplane. The lead pilot twice asked the accident pilot if he was okay and received affirmative responses. However, the pilot in trail lost sight of the accident airplane as it dropped below and behind his airplane, and the pilot positioned to the right of the lead pilot observed the accident airplane descend in a wings level, slight nose-down attitude into clouds below and behind their position. Despite multiple attempts, no further radio communication was established with the accident pilot. A witness who was located near the accident site saw the airplane descend from the clouds in a near vertical attitude until she lost sight of it behind a nearby ridgeline.
Examination of the accident site indicated that the airplane impacted terrain in a near vertical attitude. Postaccident examination of the airplane revealed no evidence of any preexisting mechanical malfunction that would have precluded normal operation.
Toxicology testing revealed ethanol in the pilot's muscle tissue; however, no ethanol was found in brain tissue making it likely the ethanol was produced postmortem. The pilot had a history of coronary artery disease and was at an increased risk for a sudden cardiovascular event; however, there is insufficient evidence to determine if his heart disease contributed to this accident.