What happened
On October 23, 2021, at approximately 1825 Alaska daylight time, an experimental, amateur-built PA-18 Replica aircraft, N368G, crashed near Willow, Alaska. The flight departed from Anderson Lake Airport in Wasilla and was on final approach to Minuteman Strip Airport (AK68) when the accident occurred.
A witness located approximately 0.3 nautical miles southeast of the airport observed the airplane flying over at a low power setting. The witness noted the engine sounded quiet, which seemed unusual, before the aircraft turned out of sight. Shortly after, the witness heard an increase in engine power followed by the sound of an impact.
The aircraft struck the ground at an elevation of about 274 feet in a near-vertical attitude. The impact resulted in substantial damage to the wings and fuselage. The pilot sustained 1 fatal injury, and the passenger sustained 1 serious injury.
The investigation
Post-accident examinations of the engine and airframe found no mechanical failures or malfunctions that would have prevented normal operation. The flaps were found in the fully extended position, and no significant tree impacts were noted on the airframe.
Investigators learned that the aircraft had been built to the pilot's specific instructions. The manufacturer of the kit and the designer of the wing flaps both stated that the pilot had requested numerous design changes to the wings, ailerons, and flaps. The kit manufacturer noted they had recommended against some of these changes, and the flap designer reported seeing "red flags" because the modifications were made without understanding how they would interact.
Maintenance records for the aircraft contained a note regarding stall characteristics, stating that the nose "drops like a rock" and noting an anomaly where the large flaps could shadow the rudder at low speeds.