On August 11, 2019, about 1128 Pacific daylight time, an experimental Lancair IV, N350CL, was destroyed when it was involved in an accident near Kooskia, Idaho. The private pilot and passenger were fatally injured. The airplane was operated by the pilot as a 14 Code of Federal Regulations Part 91 personal flight.
Flight track data showed the airplane departing Polson Airport (8S1), Polson, Montana, about 0950 and flying to the southwest between 10,500 and 10,800 ft mean sea level (msl). At 1019, about 26 miles from the accident site, the airplane turned southbound for about 4 minutes, and about 16 miles from the accident site, the airplane turned right to the southwest. At 1027, the airplane entered a climb, reaching a peak altitude of 13,500 ft msl, and the groundspeed decreased to 79 knots. The airplane subsequently entered a left descending turn to the area of the accident site. The pilot was not in communication with air traffic control during the flight.
A local resident was driving near the accident site about the time of the accident and described the weather as "nasty," with heavy rain and lightning. As he was driving, he remembered seeing a flash of light and an explosion from the accident site location and thought that it was a lightning strike. He called local authorities and hours later found out that it was the airplane impacting terrain. He reported that he did not see the airplane. Another witness was fishing nearby and described the weather consisting of heavy rain and a lot of lightning about the time of the accident. The witness remembered hearing an airplane's engine revving up and down, as if it were straining. He did not hear or see the impact.
According to Federal Aviation Administration airman records, the accident pilot held a private pilot certificate with ratings for airplane single-engine land and sea, instrument airplane, and glider. The pilot reported 4,620 hours of flight experience and 35 hours in the previous 6 months as of his last medical exam, dated February 15, 2016. The most recent pilot log recorded an accumulated flight time of 18.9 hours in the 10 months before the accident. The pilot recorded 28 instrument approaches during this time frame; however, no simulated or actual instrument time was recorded.
Review of weather radar imagery revealed an area of light to heavy precipitation moving northeast over the accident area around the time of the accident. One-half inch hail was detected about 15 minutes before the accident time. Heavy values of precipitation were detected well above 30,000 ft msl during this period. (see figure 1.) Rawinsonde observation revealed a potential for icing above 14,000 ft. Maximum vertical velocity for this atmosphere was calculated at about 6,300 ft per minute and downdraft convective available potential energy (CAPE) was measured at 317 Joules per kilogram.
An AIRMET advisory for mountain obscuration was active for the accident location at the accident time below 17,000 ft, and a Convective SIGMET was also valid for the accident area at the time of the accident.
Figure 1. Airplane's flight track with radar overlay According to Leidos Flight Service (LFS), neither LFS nor any third-party vendors using the LFS system had any contact with the accident pilot regarding the accident flight.
The accident site was located on an eastern facing slope, about 1/2-mile uphill from the Clearwater River and 3 miles east from the town of Kooskia, Idaho. The debris field was about 180 ft long and about 100 ft wide and oriented on a heading of about 94° magnetic. All major structural components and flight controls were located at the accident site. Flight control continuity could not be established due to the extensive impact and thermal damage of the wreckage. A detailed examination of the engine revealed no evidence of preexisting malfunctions or failures that would have precluded normal operation.