LARRY KETTERLING FEW P-51 MUSTANG — Lisbon, ND

What happened

The private pilot was conducting a local flight in the experimental amateur-built airplane. Recorded flight data showed that about 2 minutes before the end of the flight, the airplane's airspeed began to decrease, which was followed by a decrease in altitude. Engine parameters were not recorded. Multiple witnesses reported hearing unusual engine sounds coming from the airplane. One witness reported that the airplane's nose rose slightly, and then the airplane rolled and began a slow spin toward the ground. The witness lost sight of the airplane as it went behind a tree line, and a few seconds later, he saw a plume of smoke. Postaccident examination of the airplane revealed no anomalies with regard to the airframe or flight control system. Engine crankshaft and valve train continuity was confirmed. The engine was a converted automobile engine and used electronic ignition and fuel injection components. Testing of the ignition and fuel injection systems was not possible due to the extensive impact and postcrash fire damage.

Based on the recorded flight data and witness observations, the airplane's engine lost partial power, resulting in the pilot's inability to maintain the airplane's altitude. As the airplane descended, the pilot allowed the airplane's airspeed to decrease to the point where the wing's angle-of-attack exceeded its critical angle-of-attack, resulting in an aerodynamic stall followed by a spin. The stall/spin occurred at an altitude that was too low for recovery. The reason for the loss of engine power could not be determined based on the available evidence.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.