On August 4, 2023, about 1030 eastern daylight time, an experimental amateur-built Challenger II, N906WV, was substantially damaged when it was involved in an accident in Port Orange, Florida. The pilot sustained serious injuries and the passenger incurred minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot and passenger departed Spruce Creek Fly-In (7FL6), Port Orange, Florida, for Deland Municipal Airport (DED), DeLand, Florida. Shortly after departure, when the airplane reached about 900 ft above ground level, the engine lost power. The pilot established best glide speed and attempted to restart the engine several times; however, the engine did not regain power. The pilot performed a forced landing, during which the airplane impacted a tree and terrain. Examination of the wreckage at the accident site by a Federal Aviation Administration inspector revealed that the wreckage came to rest inverted in a residential area about 2 miles from 7FL6. Examination of the airplane revealed that the fuselage and wings sustained substantial damage. Postaccident examination of the two-cylinder, two-stroke engine revealed that PTO cylinder displayed significant scoring along the cylinder walls, consistent with the cylinder and piston being subjected to an out-of-temperature seize condition. An examination of the coolant pump, radiator, and coolant hoses revealed no anomalies that would have prevented normal operation of the coolant system. The radiator was noted to have adjustable louvers to facilitate changing the amount of cooling air flowing through the radiator fins. The louvers were noted to be near the fully closed position. The magneto cylinder and the rest of the engine displayed normal operating signatures. The examination of the airframe revealed no anomalies or mechanical failures that would have precluded normal operation.