On October 23, 2021, about 1825 Alaska daylight time, an experimental, amateur-built PA-18 Replica airplane, N368G, sustained substantial damage when it was involved in an accident near Willow, Alaska. The commercial pilot was fatally injured, and the passenger sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot departed from Anderson Lake Airport, Wasilla, Alaska, and was returning to Minuteman Strip Airport (AK68), Willow, when the accident occurred. According to the passenger, while on final approach to the runway, the airplane impacted something, which she presumed was a tree, at the same time the tail became “squirrely.” She could not remember the exact order of the events. The next thing she remembered was being slumped over after the airplane had come to rest. A witness located about .3 nautical miles to the southeast of AK68 observed the airplane fly over his location and reported that the engine appeared to be at a low power setting, as it was fairly quiet, which he thought was unusual. The airplane subsequently made a turn and disappeared from view. He then heard an increase in engine power followed by the sound of an impact. He stated that he did not hear any unusual sounds from the airplane and that the engine appeared to be operating normally. The airplane impacted in a near-vertical attitude at an elevation of about 274 ft, resulting in substantial damage to the fuselage and wings. All major components of the airplane were located at the main accident site. No significant tree impacts were observed on the airframe. The flaps were found in the fully extended position. A postaccident examination of the airframe and engine revealed no pre-accident mechanical malfunctions or failures with the airplane that would have precluded normal operation. According to the owner of the company that manufactured the kit from which the accident airplane was built, the accident pilot requested numerous design changes into the wings, ailerons, and flaps. The owner of the company stated that he was not comfortable with and recommended against some of these changes; however, the kit was manufactured to the pilot’s specifications. The designer of the wing flaps installed on the airplane stated that he remembered working with the pilot on his build request and saw several “red flags.” He stated that too many changes were being made to the design without the knowledge of how these changes would affect each other. He strongly recommended against the requested changes. A note found in the airplane’s maintenance records described the stall characteristics of the airplane and stated in part: “Stalls - The nose drops like a rock.” The note went on to say: “Another anomaly I have seen is the big flaps kind of shadow the rudder when at slow speeds. So I suggest retract flaps on stall recoveries. Obviously this will be at altitude for stall/slow flight maneuvers.”