HISTORY OF FLIGHTOn May 28, 2019, about 0550 central daylight time, a Cessna R172K airplane, N2583V, was destroyed when it was involved in an accident near Mertzon, Texas. The pilot was fatally injured. The airplane was operated as Title 14 Code of Federal Regulations Part 91 personal flight. The flight originated at Gaines County Airport (GNC), Seminole, Texas, about 0453 with a destination of Sealy, Texas. The pilot’s family stated the pilot, who owned two irrigation businesses, was transporting a piece of irrigation pipe to a job site. They stated that the pilot had not previously flown the accident route of flight, and that he occasionally flew at night, but most of his flights were during daylight hours. The pilot attempted to complete the flight the night before the accident but reported to his family that he turned around because it was “too dark,” and the pilot told his wife that he would complete the flight early the next morning. His wife suggested that they drive and meet someone halfway, but the pilot stated that he would rather fly. The pilot left his house about 0400 on the morning of the accident. PERSONNEL INFORMATIONThe pilot's most recent Federal Aviation Administration (FAA) third class medical certificate was dated May 10, 2016. On the application for that certificate, he reported 780 total hours of flight experience. The medical certificate expired for all classes on May 31, 2018. A pilot logbook recovered from the wreckage contained flights from March 1993 until August 15, 2015, and the pilot’s recent flight experience could not be determined. His family stated that the pilot did not fly consistently, and that, not including the flight the night before the accident, it had “been a couple months” since he last flew the airplane. AIRCRAFT INFORMATIONThe airplane’s maintenance records were not located. The pilot’s family stated that they were not aware of any recent maintenance completed on the airplane. METEOROLOGICAL INFORMATIONThe moon was about 28° above the horizon and about 32% illuminated at the time of the accident. Sunrise for May 29th, the day after the accident, was 0641. AIRPORT INFORMATIONThe airplane’s maintenance records were not located. The pilot’s family stated that they were not aware of any recent maintenance completed on the airplane. WRECKAGE AND IMPACT INFORMATIONThe airplane came to rest on hilly, rocky terrain at an elevation of 2,330 ft above mean sea level on a magnetic heading of about 070º. The airplane impacted the ground in a near-vertical, nose-down attitude. The main wreckage included one propeller blade, the engine, wings, fuselage, and tail sections. The second propeller blade was located about 25 ft southeast of the main wreckage. The accident location and the surrounding area was located in a remote landscape with no ground lighting, such as streetlights or other cultural lighting. All structural components of the airframe were accounted for at the accident site. Flight control continuity was established from the rudder, elevator, and elevator trim to the forward cabin floor assembly. Aileron continuity was established from the wings to the aft door post, where the cables were cut by first responders; the aileron chains remained engaged on the control wheel. The flap actuator was in the retracted (flaps up) position. Internal engine continuity was observed through the bottom of the crankcase. No signs of failure of the crankshaft, camshaft, or connecting rods were noted. The magnetos and ignition harness were impact damaged and neither magneto produced spark when rotated; both magnetos were disassembled with no preimpact anomalies noted. Examination of the airframe and engine revealed no mechanical anomalies that would have precluded normal operation. Additional information is available in the public docket for this accident. ADDITIONAL INFORMATIONSpatial Disorientation The FAA Civil Aerospace Medical 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 angular acceleration, flight in IFR conditions, frequent transfer from VFR to IFR conditions, and unperceived changes in aircraft attitude. The document concluded, "anytime there is low or no visual cue coming from outside of the aircraft, you are a candidate for spatial disorientation." The FAA's Airplane Flying Handbook, FAA-H-8083-3B, describes hazards associated with flying when the ground or horizon is obscured. The handbook states in part the following: The vestibular sense (motion sensing by the inner ear) 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 South Plains Forensic Pathology, Lubbock, Texas, performed an autopsy of the pilot. The report stated that the probable cause of death was "visceral injuries with evisceration due to blunt impact trauma due to airplane crash" and the manner of death was “accident.” The FAA Forensic Sciences Laboratory conducted toxicological testing of specimens of the pilot. The pilot’s muscle and brain tissue were positive for ethanol at 0.032 grams per hectogram (gm/hg) and 0.010 gm/hg, respectively. No tested for drugs were detected in liver tissue. Tissue samples were reported as exhibiting putrefaction. Toxicology testing performed by the medical examiners’ office was positive for ethanol at 0.085 gm/hg in spleen tissue. 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.