N801DT

HISTORY OF FLIGHTOn May 8, 2022, about 1419 mountain daylight time, an experimental amateur-built Comp Air 8 SS52 airplane, N801DT, was substantially damaged when it was involved in an accident near Grasmere, Idaho. The pilot and passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The Federal Aviation Administration (FAA) issued an Alert Notification for the missing airplane after the pilot made a distress call and reported critical fuel. A search ensued and the airplane wreckage was located by a search and rescue helicopter shortly afterwards about 7 miles southwest of Grasmere Airport (U91), Grasmere, Idaho.

ADS-B data indicated that the airplane departed Boulder City Municipal Airport, (BLU), Boulder City, Nevada, on a cross-country flight. The airplane was at a cruise altitude between 11,000 ft and 13,000 ft msl on a north to northeast heading consistent with its planned destination for most of the flight.

About 1339 the airplane began a descent, and then about 1357 turned towards the east. Shortly thereafter, the pilot declared minimum fuel with ATC. About 1401, the pilot declared critical fuel due to a fuel leak. About 1406, ATC attempted to contact the flight by relaying through another pilot. The relaying pilot made contact with the accident flight and the accident pilot stated that they would not be able to make Owyhee Airport (10U), Owyhee, Nevada, but would attempt to make U91. About 1410, the last data return indicated that the airplane’s altitude was about 6,200 ft msl, heading was 110°, and the ground speed was 121 knots. Subsequently, the airplane impacted terrain. PERSONNEL INFORMATIONThe commercial pilot held ratings for airplane single-engine land, multi-engine land, instrument airplane, and flight instructor.

The pilot was issued a FAA third-class airman medical certificate on August 14, 2020, with the following limitations: must wear corrective lenses. He had reported Type I diabetes mellitus. He also reported using insulin lispro, often marketed as Humalog, and insulin largine, often marketed as Lantus. Both types of insulin are used to treat diabetes. The first authorization for Special Issuance for type I diabetes was June 6, 1998, with multiple subsequent renewals. The most recent authorization was dated July 12, 2021.

The pilot reported on his most recent application that he had accumulated 1,350 total hours of flight experience with 50 hours in the 6 months before the examination. AIRCRAFT INFORMATIONAccording to the previous owner, the airplane’s fuel system consisted of wet wings that held 230 gallons. In addition, there was a fuel header tank located by the pilot’s feet. There was a fuel lever for each side that was selected ON or OFF. For normal operation, he would turn on both side fuel levers. He would check for fuel imbalances and then turn on the fuel lever for the high side and turn off the fuel lever for the low side, if required. He had no major fuel imbalances in his 14 years of flying the airplane. During refueling he would leave about 1 inch from the top. The highest altitude he flew the airplane was about 11,500 ft –12,500 ft msl. At that altitude, the airplane’s flight duration was about 4.0 to 4.5 hours and a range of about 800 miles. The accident flight’s duration was less than 3 hours.

A previous acquaintance of the pilot, who was a flight instructor, flew in the airplane with the accident pilot on the two flights before the accident. He stated that they both believed that the left wing felt heavy and thought it was because of a fuel imbalance. The flight instructor further stated at times he used two hands to keep the wings level and the airplane felt heavy, especially when in bank. During the postaccident examination, the left tank fuel valve was positioned ON and the right tank valve was positioned OFF, consistent with the pilot balancing the fuel by feeding from the left-wing fuel tank.

During the last airplane refueling, the refueler stated that the pilot requested that the main tanks be filled to about 2 inches from the top. The tanks were observed to be about 10 inches in height during the examination, which could make for about a 20% reduction in the amount of fuel that could be serviced into the tanks. The previous owner stated that he would leave about 1 inch from the top when refueling, to allow for expansion of the fuel.

Furthermore, the previous owner stated that the airplane was instrument certified but had no anti-ice equipment other than the pitot heat. METEOROLOGICAL INFORMATIONThe Surface Analysis Chart depicted a low-pressure system over central Idaho, north of the accident site, with a trough of low pressure extending east and west from the low. A cold front extended across central Nevada. The accident site was located on the cold air side, or north of the cold front and south of the low-pressure system in central Idaho.

The station models near the accident site depicted a counterclockwise circulation related to the low-pressure system, with northwesterly to southwesterly winds of 4 to 10 knots, light snow showers, overcast cloud cover, temperatures from 35° to 36° F, and the dew point temperatures from 33°to 35°F.

The NWS Storm Prediction Center’s Convective Outlook Chart that was valid for the period and included the accident site revealed a general risk of thunderstorm activity over Idaho during the period.

The NWS 12-hour Low-Level Significant Weather Prognostic Chart depicted general marginal visual flight rules (MVFR) conditions expected to prevail over northern Nevada, Idaho, and Oregon during the period, with the freezing level between 4,000 and 8,000 ft. No significant turbulence below 24,000 ft was expected over Idaho for the period.

NOAA numerical model sounding indicated the density altitude of about 5,452 ft msl and indicated winds were west to northwest about 3 knots. The freezing level was depicted at 711 ft above ground level or about 6,000 ft msl. The atmosphere was characterized as conditionally unstable and supported broken to overcast cumulus clouds capable of producing light rain from about 3,000 ft msl to 20,000 ft msl. The analysis program expected light-to-moderate icing conditions in the clouds, with clear to mixed type icing below 12,000 ft msl. A review of radar imagery from Boise, Idaho, revealed that the airplane flew through several areas of light-to-moderate intensity echoes as it proceeded northward and then turned eastward. At 1417, the airplane’s fight track was through an area of moderate-to-heavy intensity echoes, with the accident site on the southeast edge of the echo.

Figure 1: Base reflectively image for 1417 MDT with flight track.

The wind profile indicated little support for any turbulence below 16,000 ft over the area outside of cumulus clouds.

The 3-hour Graphic Forecast for Aviation, valid from 1200 to 1500 mountain daylight time (MDT), depicted a small area of instrument flight rules and MVFR conditions over the accident site, with surface precipitation in the form of rain, with rain/snow east and west of the accident site. Broken to overcast clouds were expected with bases from 5,000 to 7,000 ft msl and tops to 22,000 ft.

A search of PIREPs revealed that there were no reports in the immediate vicinity of the accident site. One PIREP near Twin Falls, Idaho, reported patchy clouds. Several PIREPs were reported near Boise, Idaho. 2 PIREPs reported moderate turbulence, one at 6,000 ft and one at 10,000 ft. Additionally, one PIREP reported light clear icing at 10,000 ft. Finally, a PIREP from a pilot out of Fresno, California, and about 85 miles southwest of the accident site reported moderate to severe turbulence at 8,000 ft.

There were no active SIGMETs, Convective SIGMETS, or CWA over the accident site at the time of the accident. There was a current AIRMET for mountain obscuration conditions over Idaho, which warned of mountains obscured in clouds, precipitation, and mist.

A search of the FAA contract Automated Flight Service Station provider Leidos indicated that they and no 3rd party vendors using the Lockheed Flight Service (LFS) system had any contact with the pilot of N801DT on May 8, 2022. A separate search of ForeFlight indicated that the accident pilot had an account that included N801DT; however, no flight plans were filed for the accident flight and no weather imagery, or charts were viewed using the ForeFlight app. The pilot of N801DT created a route string from BVU to ONO with a cruising altitude of 7,500 ft, and he did review airport pages for BVI at 1154 MDT, which includes METAR, TAFs, and NOTAMs. There were no indications the pilot reviewed the GFA enroute forecast or in-flight weather advisories before or inflight. AIRPORT INFORMATIONAccording to the previous owner, the airplane’s fuel system consisted of wet wings that held 230 gallons. In addition, there was a fuel header tank located by the pilot’s feet. There was a fuel lever for each side that was selected ON or OFF. For normal operation, he would turn on both side fuel levers. He would check for fuel imbalances and then turn on the fuel lever for the high side and turn off the fuel lever for the low side, if required. He had no major fuel imbalances in his 14 years of flying the airplane. During refueling he would leave about 1 inch from the top. The highest altitude he flew the airplane was about 11,500 ft –12,500 ft msl. At that altitude, the airplane’s flight duration was about 4.0 to 4.5 hours and a range of about 800 miles. The accident flight’s duration was less than 3 hours.

A previous acquaintance of the pilot, who was a flight instructor, flew in the airplane with the accident pilot on the two flights before the accident. He stated that they both believed that the left wing felt heavy and thought it was because of a fuel imbalance. The flight instructor further stated at times he used two hands to keep the wings level and the airplane fe...