HISTORY OF FLIGHTOn December 4, 2021, about 1840 Pacific standard time (PST), a Beech V35 N7933M, was substantially damaged when it was involved in an accident near Visalia, California. The pilot and three passengers were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. Recorded ADS-B data provided by the Federal Aviation Administration (FAA) showed that the airplane departed runway 30 at 1837:01 and climbed to 495 ft msl before entering a left turn. The data showed that at 1837:26, the airplane continued to climb in a left turn and reached an altitude of 620 ft msl before entering a descent. The data showed that the airplane continued descending in a left turn until ADS-B contact was lost at 1837:37, at an altitude of 395 ft, about 660 ft northwest of the accident site as seen in figure 1. The departing airport elevation was 295 ft msl. A witness located near the accident location reported that, while in her residence, she heard an airplane flying very low, followed by the sound of the airplane impacting terrain. While the airplane was flying overhead, the engine noise was constant and did not sound like it was malfunctioning. Concerned, she then notified first responders. Figure 1: View of airplane ADS-B track PERSONNEL INFORMATIONA review of the pilot’s logbook showed that he completed an instrument proficiency check on March 24, 2021. In the 12 months preceding the accident flight, he accumulated about 4 hours of simulated instrument flight, 0.4 hours of actual instrument flight and about 1 hour of night flight. METEOROLOGICAL INFORMATIONAt 1830, the Visalia Municipal Airport (VIS) automated weather observation station reported wind from 280° at 5 knots, visibility of 2 ½ miles, mist, broken ceiling at 300 ft above ground level (agl), temperature 8°Cand dew point temperature 8°C, altimeter 30.24 inches of mercury. An AIRMET SIERRA advisory for instrument flight rules conditions was issued at 1245 and was valid at the time of the accident. The advisory identified ceilings below 1,000 ft, visibility below 3 statute miles, mist, and fog. No air traffic control services were provided to the pilot during the accident flight. WRECKAGE AND IMPACT INFORMATIONThe airplane impacted a flat, open wheat field about 1 mile southwest of the departure end of runway 30. It came to rest on its left side, on a heading of about 265° magnetic, at an altitude of 290 ft mean sea level. The first identified point of contact with terrain was a ground scar/impression about 14 ft long, 22 inches wide, and 3 inches deep. The debris field extended about 345 ft to the main wreckage on a magnetic heading of 105°and was 200 ft wide. The propeller and propeller hub were located about 15 ft from the initial impact point. Flight control continuity was established from the cockpit to all primary flight controls. Numerous separations were noted within the flight control system consistent with signatures consistent with overload separation or due to recovery personnel during the recovery process. There were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. ADDITIONAL INFORMATIONThe FAA Civil Aeromedical Institute's publication, "Introduction to Aviation Physiology," defines spatial disorientation as a “loss of proper bearings; 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 IFR conditions, frequent transfer between visual flight rules and IFR conditions, and unperceived changes in aircraft attitude. The FAA’s Airplane Flying Handbook (FAA-H-8083-3B) describes some 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 can and will confuse the pilot. Because of inertia, the sensory areas of the inner ear cannot detect slight changes in airplane attitude, 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 INFORMATIONThe Tulare County Coroner's Office, Tulare, California, performed an autopsy of the pilot. The pilot's cause of death was blunt trauma. Toxicology testing performed at the FAA Forensic Sciences Laboratory detected ethanol in the pilot’s liver (0.402 grams per hectogram [gm/hg]), kidney (0.045 gm/hg), and muscle tissue (0.035 gm/hg); no ethanol was detected in the pilot’s muscle tissue by another laboratory. Isopropanol was detected in his liver tissue at 0.009 gm/hg. The non-impairing cholesterol lowering medication atorvastatin was detected in the pilot’s liver and muscle tissue.