On June 21, 2022, about 1355 eastern daylight time, an experimental amateur-built Lightning airplane, N51TM, was involved in an accident near Canandaigua, New York. The private pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations part 91 personal flight. According to recorded audio from the Canandaigua Airport (IUA) common traffic advisory frequency, about 1347, the pilot advised he was taxiing to runway 31. About 7 minutes later, he made a mostly unintelligible comment that included a reference to runway 31, consistent with announcing his takeoff. A witness who was located about 350 ft northeast of the accident site reported seeing the airplane to the west of his position flying about 20 ft above a wheat field. The airplane disappeared over a hill. He went to the top of the hill, saw that the airplane had crashed in the field, and contacted law enforcement. The pilot reported that he extricated himself from the cockpit and was airlifted to a hospital after sustaining serious injuries during the accident. The pilot’s wife reported that her husband’s only recollections of the accident were that he thought the field was flat but encountered a bump during the landing roll and that he turned off the fuel selector valve after the accident. He passed away more than 30 days after the accident. The accident site was located about 3,170 ft north-northwest from the departure end of runway 31. Examination of the accident site by a Federal Aviation Administration (FAA) airworthiness inspector revealed the airplane came to rest upright with the nose landing gear collapsed; the airplane sustained minor damage. An engine monitor and portable GPS receiver were retained by NTSB for further examination; however, neither device contained any data associated with the accident flight. The airplane was recovered and secured in the pilot’s hangar for further examination. Postaccident examination of the airplane by an FAA airworthiness inspector revealed adequate fuel in both wing fuel tanks; no contaminants were noted. An odor of fuel in the cockpit was associated with the left fuel supply line that separated from the fuel selector due to impact damage. During activation of the auxiliary fuel pump, a fuel smell was noted, but visual examination of the engine compartment could not identify the source. During a subsequent attempt to start the engine following activation of the auxiliary fuel pump, the flexible fuel hose from the gascolator to the engine-driven fuel pump separated from the outlet fitting of the gascolator. Inspection of the hose and clamp revealed the screw used to tighten the hose clamp was tight to turn, but the hose was not tight on the barbed fitting. The hose was tightly secured to the fitting by the inspector. The engine was started with the fuel selector positioned to the right fuel tank and operated normally when the throttle was advanced to partial power. At idle, the engine operated rough and lost power; this was attributed to the choke being partially on. Full power or prolonged engine operation was not possible due to the impact-damaged propeller blades. According to maintenance records, the airplane’s last condition inspection was performed about 8 months and 14 operating hours before the accident. During the inspection, the pilot, who was the builder of the airplane, reportedly replaced a fuel line associated with the auxiliary fuel pump in the cockpit. A representative of the airplane designer reported that a loose fuel hose at the outlet of the gascolator could introduce air into the fuel supply being delivered to the engine-driven fuel pump; this condition could result in reduced fuel flow and reduced engine power. No determination could be made based on the available evidence as to the reason for the off-airport landing executed by the pilot.