HISTORY OF FLIGHTOn August 4, 2023, about 1010 mountain daylight time, an experimental amateur-built Glasair Glastar airplane, N617G was substantially damaged when it was involved in an accident near Idaho City, Idaho. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to a friend, who was also a pilot, he and the accident pilot departed Caldwell Executive Airport (EUL), Caldwell, Idaho, each in their own airplanes, and flew to Idaho City USFS Airport (U98), Idaho City, Idaho. The accident pilot’s airplane sounded normal upon arrival. The two pilots parked their airplanes and walked into town for breakfast. During breakfast, the accident pilot made no mention of any anomalies with the accident airplane. After returning to their airplanes, the accident pilot told the friend that he had to go to the bathroom and began walking to the woods. The friend told him that there were facilities nearby. The accident pilot then indicated that he would not make it. He returned about 10 minutes later and continued to prepare to depart. The pilots started their airplanes, and the friend recalled that the accident airplane started immediately. They both taxied across the asphalt parking area to the beginning of the gravel runway, with the accident airplane behind the friend’s airplane. The friend asked the accident pilot via radio if he was ready to go but received no response. The friend then departed and later tried to communicate with the accident pilot over commonly used radio frequencies but again received no response. He recalled the accident pilot “wasn’t chatty on the radio” and gave it no further consideration as he returned to EUL. ADS-B data showed the accident airplane departed EUL about 0750; this data ended about eight miles southwest of U98. Data from the electronic flight instrument system on board the accident airplane showed it arrived U98 about 0813 and began taxiing for departure about 1001. The last data point showed the airplane on the asphalt portion of the runway, before the gravel portion of the runway, about 1004. Engine data from the electronic flight information system showed increases in engine speed to about 1,500 rpm and ground speed to about 12 kts before the engine data also ended at 1004. A witness located about ½ mile from U98 reported that he was outside and heard an airplane depart the airport. About ten to fifteen minutes later, he heard another engine power up. The sound continued until “it just stopped.” He then heard a “slap” sound. He stated that it sounded like the pilot never took his hand off the throttle. He believed it to be an airplane engine, so he drove to the airport and was the first person to arrive. He saw the white tail of an airplane in the trees. He ran to the airplane and called 911. PERSONNEL INFORMATIONA family member reported that the pilot’s family had a history of heart disease and that the pilot was aware of his potential for a heart attack. The friend reported that the accident pilot had no difficulties flying the airplane as he had owned it for several years and maintained it to a very high standard. WRECKAGE AND IMPACT INFORMATIONExamination of the accident site revealed that the airplane came to rest upright in a line of trees about 100 ft left of the runway 22 centerline, on a heading of about 144°, at an elevation of about 3,890 ft mean sea level and about 913 ft from the beginning of the gravel runway. Five trees, identified as tree A, B, C, D, and E, exhibited evidence of recent contact. Small, low-hanging branches on trees A and B were broken off and deposited at the tree base. Tree C had a large gouge about 10 ft above its base. Trees D and E were located about 3 ft apart and each exhibited large impact marks and loss of bark about 8 ft above its base. Tree E had a deep chop mark, consistent with a cut from a sharp object. The gouges in trees C, D, and E were indicative of a left-wing-high, right-wing-low impact (figures 1 and 2). Figure 1. Location of the wreckage and the trees impacted by the airplane. Figure 2. Trees D and E. The fuselage came to rest at the base of trees D and E. The fuselage was fractured and separated from the right-side door area to the empennage. Tree D was located at the end of this fuselage separation. This damage was consistent with tree D entering and splitting the fuselage along the longitudinal seam of the two-part constructed fuselage. Postaccident examination of the airplane revealed no mechanical malfunctions or failures that would have precluded normal operation. The two fuel tanks contained a significant quantity of fuel. Flight control continuity was confirmed from the flight control surfaces to the mid-point of the cabin. The throttle was positioned in the full power position. The propeller handle was positioned in the high rpm position. The mixture lever was separated from the throttle quadrant and found in the debris. Examination of the runway revealed two long impressions in the gravel beginning about 100 ft past the end of the asphalt section. The marks were consistent with the left main landing gear and the tail wheel. The marks progressed down the runway, arced to the left, and proceeded directly to the wreckage. Both marks remained mostly in contact with the runway but occasionally disappeared. The tracks disappeared shortly before the accident site. There were no indications of skidding in the marks. The total length of the impressions was about 694 ft (figure 3). Figure 3. Estimated path of the airplane. The seat and seat adjustment rails were damaged. Identification of the preaccident seat position could not be determined. According to a family friend who owned an airplane almost exactly like the accident airplane, the seats adjust in travel about 6 inches; however, seat adjustments usually occur while the pilot is outside the airplane, and the accident pilot already had his seat adjusted to his liking. ADDITIONAL INFORMATIONThe FAA Airplane Flying Handbook (FAA-H-8083-3C) stated, in part, for a normal take off, “At the same time, the rudder pedals are used to keep the nose of the airplane pointed down the runway and parallel to the centerline. The effects of engine torque and P-factor at the initial speeds tend to pull the nose to the left.” MEDICAL AND PATHOLOGICAL INFORMATIONAn autopsy of the pilot was conducted by the Boise County Coroner’s Office, Idaho City, Idaho. The cause of death was multiple blunt force injuries. FAA postmortem toxicology testing detected cetirizine in cavity blood at 61 ng/mL and in urine at 195 ng/mL. Cetirizine is an over-the-counter antihistamine medication that is commonly used to treat allergy symptoms. Cetirizine typically carries a warning that users may experience drowsiness with use and should use caution when driving a motor vehicle or operating machinery. Data on sedation and psychomotor impairment from cetirizine are mixed, with some studies finding some sedating and impairing effects. The FAA states that pilots should wait 48 hours after using cetirizine before flying, to allow time for the drug to be cleared from circulation. The pilot’s last aviation medical examination was December 30, 2020. At that time, the aviation medical examiner deferred the medical certification decision to the FAA, based on the pilot reporting taking leflunomide, a prescription immunosuppressive medication commonly used to treat rheumatoid and psoriatic arthritis. After review, the FAA issued a Letter of Eligibility in February 2021 for a third-class medical certificate. The FAA issued a third-class medical certificate with the limitation that the pilot must wear corrective lenses. The pilot’s medical certificate had expired at the time of the accident.