History of Flight
On May 8, 2022, about 1419 mountain daylight time, an experimental amateur-built Comp Air 8 SS52 airplane, N801DT, was substantially damaged when it impacted terrain near Grasmere, Idaho. The pilot and passenger were fatally injured. The flight was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
The Federal Aviation Administration (FAA) issued an Alert Notification after the pilot made a distress call and reported critical fuel. The wreckage was located by a search and rescue helicopter about 7 miles southwest of Grasmere Airport (U91).
ADS-B data indicated the airplane departed Boulder City Municipal Airport (BLU), Nevada, on a cross-country flight. It cruised between 11,000 and 13,000 ft msl on a north-northeast heading. About 1339, it began a descent and turned east at 1357. The pilot declared minimum fuel to ATC, then at 1401 declared critical fuel due to a fuel leak. At 1406, ATC relayed through another pilot; the accident pilot stated they could not reach Owyhee Airport (10U) but would attempt to reach U91. The last data return at 1410 showed altitude 6,200 ft, heading 110°, ground speed 121 knots. The airplane subsequently impacted terrain.
Pilot Information
The commercial pilot held ratings for airplane single-engine land, multi-engine land, instrument airplane, and flight instructor. He held a third-class medical certificate issued August 14, 2020, with limitations: must wear corrective lenses. He reported Type I diabetes mellitus and used insulin lispro and insulin glargine. Special Issuance for Type I diabetes was first authorized June 6, 1998, with the most recent renewal July 12, 2021. He reported 1,350 total flight hours, with 50 hours in the 6 months before the exam.
Aircraft Information
According to the previous owner, the airplane’s fuel system consisted of wet wings holding 230 gallons and a fuel header tank by the pilot’s feet. Each wing had a fuel lever (ON/OFF). Normal operation used both levers on; imbalances were corrected by selecting only the high side. The previous owner reported no major imbalances in 14 years. He left about 1 inch from the top when refueling. The airplane’s flight duration at altitude (11,500–12,500 ft) was about 4.0–4.5 hours with an 800-mile range. The accident flight duration was less than 3 hours.
A flight instructor who flew with the pilot on the two prior flights stated both believed the left wing felt heavy, likely due to a fuel imbalance. He sometimes used two hands to keep wings level, especially in bank. Postaccident examination found the left fuel valve ON and right valve OFF, consistent with feeding from the left tank. The refueler stated the pilot requested the main tanks be filled to about 2 inches from the top. The tanks were about 10 inches tall, suggesting about a 20% fuel capacity reduction. The previous owner left 1 inch for expansion. The airplane was instrument certified but had no anti-ice equipment except pitot heat.
Meteorological Information
Surface analysis showed a low-pressure system over central Idaho, north of the accident site, with a trough extending east-west and a cold front across central Nevada. The accident site was on the cold air side, north of the front and south of the low. Station models near the site indicated northwesterly to southwesterly winds of 4–10 knots, light snow showers, overcast clouds, temperatures 35–36°F, dew points 33–35°F.
The NWS Storm Prediction Center Convective Outlook showed a general risk of thunderstorms over Idaho. The Low-Level Significant Weather Prognostic Chart indicated marginal VFR conditions with freezing levels between 4,000 and 8,000 ft. No significant turbulence below 24,000 ft was expected. A NOAA sounding showed density altitude about 5,452 ft, winds west-northwest at 3 knots, freezing level at about 6,000 ft. The atmosphere was conditionally unstable, supporting broken to overcast cumulus clouds with light rain from 3,000–20,000 ft. Light-to-moderate icing was expected in clouds below 12,000 ft. Radar from Boise, Idaho, showed the airplane flew through several areas of light-to-moderate echoes, and at 1417 through moderate-to-heavy echoes, with the accident site on the southeast edge.
A 3-hour Graphic Forecast for Aviation valid 1200–1500 MDT depicted IFR and MVFR conditions over the accident site with rain and rain/snow. Broken to overcast clouds were expected with bases 5,000–7,000 ft and tops to 22,000 ft. No PIREPs were from the immediate vicinity. Near Twin Falls, patchy clouds were reported. Near Boise, moderate turbulence was reported at 6,000 and 10,000 ft, light clear icing at 10,000 ft. A PIREP 85 miles southwest reported moderate to severe turbulence at 8,000 ft. No active SIGMETs, Convective SIGMETs, or CWAs were over the site. An AIRMET warned of mountain obscuration in clouds, precipitation, and mist.
A search of Leidos and Lockheed Flight Service showed no contact with the pilot on May 8. ForeFlight records showed the pilot had an account including N801DT but no flight plans, weather imagery, or charts were viewed. The pilot created a route string from BVU to ONO with cruising altitude 7,500 ft and reviewed airport pages for BVI at 1154 MDT (including METARs, TAFs, NOTAMs). There was no indication he reviewed the GFA enroute forecast or in-flight weather advisories.
Wreckage and Impact
The airplane impacted hilly desert terrain on a heading of about 034° at elevation about 5,780 ft, in a left bank attitude. All major components were found at the site. No post-impact fire occurred. The first point of impact was a ground disturbance with the left position light buried. About 20 ft further, ground markings led to a large disturbed area, then a 150-ft debris trail to the main wreckage. Both wings and horizontal stabilizers separated. The front fuselage and instrument panel sustained substantial impact damage. The vertical stabilizer and rudder were relatively intact. The engine was bent 90° to the right.
A strong fuel smell and fuel staining were present. The left main fuel tank was compromised; no perforations consistent with a leak were found in left wing remnants. The right main fuel tank (internally examined) and header tank showed no anomalies. Fuel caps had no issues; locking tabs and seals were good, vents were unobstructed. All fuel lines were examined; no leaks were observed. The left fuel selector was ON, right was OFF. Impact damage near the right selector was noted. The left wing fuel screen was partially deteriorated; right wing screen intact with some debris. Fuel continuity was confirmed by blowing air through lines to the engine; the engine fuel line had no observable fuel. Flight control continuity was confirmed; flaps were retracted. No evidence of preimpact mechanical failures or malfunctions was found.
Medical and Pathological Information
The Owyhee County Coroner conducted an autopsy; cause of death was severe blunt force trauma. Toxicology testing by the FAA detected atorvastatin, salicylic acid, and diphenhydramine. Glucose in urine was 29 mg/dL. Atorvastatin (Lipitor) treats high cholesterol and is acceptable for FAA certification. Salicylic acid (a metabolite of aspirin) is used for minor pain and as an antiplatelet; use is acceptable if the underlying condition is acceptable. Diphenhydramine (Benadryl) is a non-prescription antihistamine that can cause sedation; it should not be used within 60 hours of flying, and regular use is unacceptable. Depending on administration timing, diphenhydramine could have posed a hazard to flight safety.