HISTORY OF FLIGHTOn April 27, 2018, at 1416 eastern daylight time, an experimental amateur-built Wolfe Kitfox V, N818TW, impacted terrain about 4 miles south of Kalkaska City Airport, Kalkaska, Michigan. The airplane was destroyed by impact forces. The private pilot and passenger were fatally injured. The airplane was registered to and operated by the pilot under Title 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The flight was destined for Mackinac Island Airport, Mackinac Island, Michigan. According to a Federal Aviation Administration (FAA) inspector, witnesses reported seeing the airplane in a counterclockwise upright spin beginning about 1,000 ft above ground level. The airplane then impacted the ground in a flat attitude. Ground scarring indicated counterclockwise rotation of the airplane. According to the Kalkaska Sheriff's Office Incident Report, fuel was leaking from both airplane wings. The report included accounts from witnesses who stated that the airplane "was not under power" and was "spinning belly down." PERSONNEL INFORMATIONThe private pilot held a private pilot certificate as well as repairman experimental aircraft builder and repairman light sport aircraft (inspection) certificates. The pilot held a third-class medical certificate dated August 24, 2016, with the restriction that the pilot must wear corrective lenses. At that time, he reported 659 hours of total flight experience, of which 23 hours were in the previous 6 months. A pilot logbook entry stated the pilot's private pilot certificate was issued on October 8, 1995. AIRCRAFT INFORMATIONThe pilot purchased the airplane kit in 1999 and subsequently built the airplane. An airworthiness certificate for the airplane was issued in 2007, and it was registered to the pilot. The airplane was equipped with a Continental Motors IOF-240-B engine. A two-bladed wooden propeller was attached to the engine. The airplane was not equipped with a stall warning system and was not required to be so equipped due to its classification as an experimental amateur-built airplane. AIRPORT INFORMATIONThe pilot purchased the airplane kit in 1999 and subsequently built the airplane. An airworthiness certificate for the airplane was issued in 2007, and it was registered to the pilot. The airplane was equipped with a Continental Motors IOF-240-B engine. A two-bladed wooden propeller was attached to the engine. The airplane was not equipped with a stall warning system and was not required to be so equipped due to its classification as an experimental amateur-built airplane. WRECKAGE AND IMPACT INFORMATIONPostaccident examination of the airplane confirmed flight control continuity from the control surfaces to the cockpit controls. A fuel sample taken from the left fuel tank did not exhibit contamination and was consistent with 100 low-lead fuel. The airplane fuel tanks had usable fuel. The magnetos and the fuel selector valve were in the ON position. The engine was partially attached to the airframe. One propeller blade had broken off near the tip, and the other propeller blade had broken off near the blade root. The remaining propeller was attached to the crankshaft hub. Postaccident examination of the engine revealed that the spark plugs exhibited features of normal operation. Borescope examination of the engine cylinders revealed no anomalies. The engine was rotated through by hand, and engine drive and valve train continuity was confirmed. During the engine rotation, air was expelled and drawn in through the spark plug holes. The fuel metering unit exhibited no anomalies that would have precluded operation. A compact flash memory card was removed from the instrument panel flight display; however, no data were recovered. MEDICAL AND PATHOLOGICAL INFORMATIONAn autopsy of the pilot that was conducted by the Kalkaska County Medical Examiner, Kalkaska, Michigan, found that his cause of death was "multiple blunt force injuries." Toxicology testing performed at the FAA's Forensic Sciences Laboratory identified tadalafil in the pilot's blood and liver specimens. Testing for cyanide was not performed, and no ethanol was detected in the pilot's vitreous specimens.