HISTORY OF FLIGHTOn August 29, 2022, about 1204 Alaska Daylight Time, a Charles Brad Story TT FOX amateur-built airplane, N2723P sustained substantial damage when it was involved in an accident at the Wolf Lake Airport (4AK6), Wasilla, Alaska. The pilot was fatally injured. The airplane was operated by the pilot as a Title 14 Code of Federal Regulations Part 91 test flight. Family reported that the purpose of the flight was for the pilot to complete the required flight hours during the phase I testing of the amateur-built airplane. Witnesses at the airport observed the airplane departing to the south and then heard the airplane returning towards the airport. The pilot made a call on the radio saying he was on the downwind leg of the traffic pattern for landing; no other transmissions were heard from the airplane. The flight path downloaded from an onboard Dynon Skyview D1000 showed the airplane turned crosswind after takeoff then entered a right downwind for runway 08. Once abeam the departure end of the runway, the airplane stopped its climb, began a descent, and turned toward the approach end of the gravel strip, runway 02. (Figure1) Witnesses then observed the airplane flying low and fast, heading toward the gravel strip. Witnesses reported hearing changes in the engine rpm which were described as the engine revving, going to idle, and surging. They also reported the airplane was traveling “fast,” with two witnesses reporting pitch oscillations. A witness saw the airplane “abruptly pitch down as if the airplane hit something “and impacted the hangar. Figure 1. Flight path data from the Dynon Skyview. The yellow path indicates the flight track of the accident airplane. PERSONNEL INFORMATIONThe pilot was the owner and builder of the airplane. The pilot had completed 4 test flights in this airplane starting on August 21. The first and second flights were logged for 0.6 hours each. The third and fourth flights were for 1 hour each. The fourth flight was on August 27th. All flights were conducted at 4AK6. AIRCRAFT INFORMATIONThe pilot had started building the airplane about 3 years before and finished a couple of weeks before the accident. The Federal Aviation Administration DAR-F Inspector completed a Conformity Inspection of the airplane on August 13, 2022. A Special Airworthiness Certificate was issued on August 13, 2022. When the airplane passed this inspection, the next step was that a pilot must fly between 25-40 hours of test flights in specific non-populated areas to make sure all components are operating properly. Only after that test flight time was completed could the pilot fly the airplane with passengers on board. The airplane was in the test flight stage with about 3.2 hours of flight time completed. AIRPORT INFORMATIONThe pilot had started building the airplane about 3 years before and finished a couple of weeks before the accident. The Federal Aviation Administration DAR-F Inspector completed a Conformity Inspection of the airplane on August 13, 2022. A Special Airworthiness Certificate was issued on August 13, 2022. When the airplane passed this inspection, the next step was that a pilot must fly between 25-40 hours of test flights in specific non-populated areas to make sure all components are operating properly. Only after that test flight time was completed could the pilot fly the airplane with passengers on board. The airplane was in the test flight stage with about 3.2 hours of flight time completed. WRECKAGE AND IMPACT INFORMATIONThe accident was in a relatively flat, residential area next to 4AK6. All components of the airplane were located in the vicinity of the main wreckage. The airplane impacted in a nose-low attitude into the back of a hangar and came to rest inside the hangar. About 60 to 80 ft before the impact site there was evidence of an impact with a tree. The top 10 to 12 ft of the tree was broken off and laying on the ground in the direction of the flight path. Branches and parts of the tree were found scattered between the tree, the hangar, and inside the hangar. The airplane came to rest inside a hangar. The main fuselage was on the floor, with the right wing still attached to the airplane in the attic. The left wing was impact-separated and located outside the building. The flaperon handle was set to the 10° position. Flight control continuity was established in all flight controls with separation from impact damage. Examination of the engine revealed that both cylinders had compression. The spark plugs were not fouled. Engine continuity was confirmed by operating the starter pull handle and watching the propeller move. The engine was a Rotax 850 engine that was designed to be used in snowmachines and was not for aircraft use. The airplane was equipped with a three-blade composite propeller. All three blades exhibited impact damage. There were no mechanical malfunctions or anomalies with the engine that were noted that would have precluded normal operation. A Dynon Skyview system was removed from the airplane and sent for data download at the National Transportation Safety Board Recorders Laboratory. The flight data indicated that at 1203, about 8 seconds before impact, the engine rpm went from idle to max rpm 3 times. Auditory witnesses also recalled hearing the engine fluctuating rpm right before impact.