HISTORY OF FLIGHTOn June 30, 2021, about 0450 central daylight time, an Earthstar Aircraft Gull 2000 experimental light-sport airplane, N1712L, was substantially damaged when it was involved in an accident near Curtiss, Wisconsin. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. An individual who was interested in purchasing the airplane stated that the pilot offered to fly the airplane from Curtiss, Wisconsin, to New Richmond Regional Airport (RNH), New Richmond, Wisconsin, where he could examine it. The potential buyer suggested to meet at RNH about 1200, but the pilot subsequently asked to meet at 0600. The potential buyer agreed to meet at 0600 believing that the pilot had to return for work after their meeting. The potential buyer stated that on the morning of the accident, about 0600, there was low ground fog at RNH. When the airplane did not arrive at RNH, about 0615, he began to call and send text messages to the pilot but never received any replies. Around 1100, he called the Clark County Sheriff’s Office to report that the pilot did not arrive at RNH. According to the Clark County Sheriff’s Office, the last cellular activity recorded for the pilot’s mobile phone occurred about 0447. A witness who lived near the private airstrip saw the airplane on the ground at the airstrip a few minutes before 0500. The witness stated that it was foggy and that she could only see the airplane’s lights but heard the airplane’s engine operating as the airplane took off to the west. Another witness who lived near the private airstrip reported that he was awoken by the sound of the airplane departing the airstrip about 0450 or 0455. A review of air traffic control radar sensor data and ADS-B data revealed no track data for the flight. According to the Clark County Sheriff’s Office, the wreckage was located by the property owner about 1706. PERSONNEL INFORMATIONThe pilot was not instrument rated. According to his flight logbook, the pilot logged 3 hours of simulated instrument flight before his checkride for his private pilot certificate on March 14, 2020. He logged an additional 0.2 hours of simulated instrument time during his checkride. AIRCRAFT INFORMATIONThe airplane was not equipped for flight in instrument meteorological conditions (IMC). METEOROLOGICAL INFORMATIONMultiple Clark County Sheriff’s Office deputies reported that weather near the accident location in the early morning included dense fog with limited surface visibility. The visibility on the roadways near the accident location was 20 to 100 ft and required the use of windshield wipers while driving. Additionally, a semi-trailer truck had inadvertently departed the side of Wisconsin State Highway 29 because the driver reportedly could not see the road while driving in the dense fog. At 0250, the National Weather Service (NWS) Weather Forecast Office in La Crosse, Wisconsin, issued an Area Forecast Discussion that stated, in part: Weak boundary layer flow and residual low-level moisture will result in areas of early morning fog, especially in low-lying areas/valleys, but should quickly erode after sunrise. The fog may be locally dense, and will continue to monitor over the next few hours. At 0400, the NWS Weather Forecast Office in La Crosse, Wisconsin, issued a Dense Fog Advisory for an area that included the accident location which called for locally dense fog that reduced visibilities to 0.5 statute mile (sm) or less and stated, in part: Light winds, mostly clear skies and wet grounds from the recent rains have resulted in areas of fog early this morning, mostly in low lying areas and near bodies of water. The fog will be locally dense, reducing visibilities to 1/2 mile or less. Early morning travelers should be prepared for rapidly reduced Visibilities at times. Visibilities could go from good to poor within a few hundred feet. Much of the fog will lift and dissipate by 8 to 9 am. Exercise caution. At 0345, an Airman’s Meteorological Information (AIRMET) SIERRA advisory for IFR conditions was issued for an area that included the accident location and included ceilings below 1,000 ft above ground level (agl), visibilities less than 3 sm, precipitation, and fog. At 0400, the Graphical Forecasts for Aviation (GFA) depicted few and scattered clouds with variable surface visibilities between 0 sm and 5 sm at or near the accident location. At 0435, the weather at Taylor County Airport (MDZ), Medford, Wisconsin, about 10 sm northeast of the accident location, included a calm surface wind, 0.5 sm surface visibility with fog, and 500 ft vertical visibility. At 0455, the weather at MDZ improved to 5 sm visibility with mist and clear skies. On the day of the accident, civil twilight began at 0442 and the official sunrise was at 0519. AIRPORT INFORMATIONThe airplane was not equipped for flight in instrument meteorological conditions (IMC). WRECKAGE AND IMPACT INFORMATIONThe main wreckage was in a wooded area at the edge of a cornfield about 0.33 nautical miles (nm) southwest of the west end of the grass airstrip that the pilot used for takeoff, as depicted in figure 1. The airplane sustained substantial damage to both wings, the empennage, and the fuselage. Based on damage to trees at the accident site, the airplane was traveling to the south when it descended into the trees in an approximately 30° nose-down flight path angle. The airframe parachute rocket deployed due to impact forces; the activation handle was stowed with the safety pin removed. All structural components and flight control surfaces were located at the accident site. A postaccident examination revealed no evidence of a preexisting mechanical malfunction or failure that would have prevented normal operation of the airplane. All structural damage to the airplane was consistent with tree and ground impact. Figure 1 – Aerial view of the accident site location and departure airstrip ADDITIONAL INFORMATIONThe FAA Civil Aeromedical Institute's publication, Introduction to Aviation Physiology, defines spatial disorientation as a loss of proper bearings or a state of mental confusion as to position, location, or movement relative to the position of the earth. Factors contributing to spatial disorientation include changes in acceleration, flight in IMC, frequent transfer between visual meteorological conditions (VMC) and IMC, and unperceived changes in aircraft attitude. The FAA's Airplane Flying Handbook (FAA-H-8083-3A) described hazards associated with flying when the ground or horizon are obscured. The handbook states, in part, the following: The vestibular sense (motion sensing by the inner ear) in particular tends to confuse the pilot. Because of inertia, the sensory areas of the inner ear cannot detect slight changes in the attitude of the airplane, nor can they accurately sense attitude changes that occur at a uniform rate over a period of time. On the other hand, false sensations are often generated; leading the pilot to believe the attitude of the airplane has changed when in fact, it has not. These false sensations result in the pilot experiencing spatial disorientation. MEDICAL AND PATHOLOGICAL INFORMATIONAccording to the autopsy authorized by Clark County Coroner’s Office, Neillsville, Wisconsin, and completed by the Ramsey County Medical Examiner Office, St. Paul, Minnesota, the pilot experienced traumatic head and neck injuries. No significant natural disease was identified by the medical examiner. Toxicology testing performed for the Medical Examiner’s office was negative for ethanol and drugs of abuse in the pilot’s blood. Toxicological testing, completed by the Federal Aviation Administration Forensic Sciences Laboratory, detected ethanol in the pilot’s brain and lung tissue at 0.012 grams per hectogram (gm/hg) and 0.042 gm/hg, respectively. Ethanol was detected in his urine at 0.010 grams per deciliter (gm/dL). N-propanol was also detected in his lung tissue. Tissue samples exhibited putrefaction. No other tested for medications or drugs of abuse were detected in urine. Ethanol is a social drug commonly consumed by drinking beer, wine, or liquor. It acts as a central nervous system depressant; it impairs judgment, psychomotor functioning, and vigilance. Ethanol is water soluble, and after absorption it quickly and uniformly distributes throughout the body’s tissues and fluids. The distribution pattern parallels water content and blood supply of the tissue. Ethanol can be produced after death by microbial activity; sometimes in conjunction with other alcohols, such as propanol. Extensive trauma increases the spread of bacteria and raises the risk of ethanol production after death.