WPR11LA233

The pilot reported that, when the airplane was at 13,500 feet mean sea level and flying over snow-covered mountainous terrain, he changed course and initiated a descent to avoid moisture-laden clouds. During the descent into a valley, the pilot noticed "slightly rising terrain," so he initiated a climb. The pilot reported that it appeared he had a visual illusion because he thought the airplane was at a higher altitude than the approaching terrain. The airplane subsequently impacted the snow-covered mountain and sustained substantial damage to the fuselage. The passenger stated that he and the pilot had become disoriented. It is likely that the snow-covered terrain and the overcast sky created a flat light condition, which inhibited the visual cues necessary for the pilot to orient himself to the terrain. The pilot reported no preimpact mechanical failures or malfunctions with the airplane that would have precluded normal operation.

On May 21, 2011, about 1450 mountain daylight time, an experimental amateur built Palmer RV6A airplane, N52VC, impacted mountainous terrain in the Teton National Forest near Cody, Wyoming. The pilot/owner operated the airplane under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. The pilot and one passenger received serious injuries. The airplane sustained substantial damage to the fuselage. Visual meteorological conditions prevailed for the flight that departed from Marsing, Idaho, at 1138, and no flight plan had been filed. According to the Federal Aviation Administration (FAA) coordinator, the pilot had Visual Flight Rules (VFR) flight following services with Salt Lake City Center (SLCC) about an hour prior to the accident, when SLCC terminated flight following services due to no radar coverage in the mountains. SLCC personnel had to relay the flight following termination through another pilot. The accident pilot responded affirmatively to the flight following termination, via relay with the other pilot. Before the accident, SLCC relayed to the pilot that there were several pilot reports (PIREPS) for icing between 11,000 feet and 16,500 feet mean sea level (MSL). In the pilot's written statement, he reported that the airplane was at 13,500 feet to clear high terrain in a mountainous area. The pilot changed course and descended from 13,500 feet to avoid clouds that appeared to be "moisture laden." During the descent into a valley, the pilot noticed "slightly rising terrain" and initiated a climb. The pilot stated that it appeared he had a visual illusion, and thought they were at a higher altitude than the upcoming terrain. The airplane subsequently impacted a mound of snow. According to the passenger, they had been flying in a mountainous area, and had become disoriented from the white out conditions. The pilot reported not preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation. The Park County Search and Rescue coordinator stated that, the airplane came to rest upright in 4 feet of snow at an elevation of 10,800 feet. The pilot was able to relay a mayday call through a pilot to Salt Lake City Center.