CEN17LA096 · Cook Smith Aviation Repli

The private pilot reported that he departed in the experimental, amateur-built airplane with 10 gallons of fuel in the left fuel tank and 15 gallons of fuel in the right fuel tank. He had flown for about 15 minutes in straight and level flight, then he conducted a simulated forced landing to a wheat field. During the recovery from the practice maneuver, he turned off the carburetor heat, applied full engine power, and raised the nose to a steep pitch attitude of about 35° to 40° nose up. He stated that the engine experienced a total loss of power in the climb about 200 to 500 ft above ground level. He pushed the control stick full forward to maintain airspeed and chose to land straight ahead. The engine started to "sputter" and regain power about the time that the airplane struck the trees, which resulted in substantial damage to the wings and fuselage.

Examination of the accident site revealed that no fuel was present; however, the airplane's fuel system was largely compromised by impact damage. There were no apparent fuel stains on the fabric-covered wings. Based on the temperature and dew point about the time of the accident, the conditions were not favorable for carburetor icing at any power setting. The engine was installed on an engine test stand and operated through a range of engine power settings between 1,200 to 2,700 rpm, and at idle. Examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.

The airplane had a 180-hp engine installed that was not equipped with an engine-driven fuel pump or electric fuel boost pump. The airplane's gravity feed fuel system had 24-gallon fuel tanks installed in each overhead wing, but there was no fuel header tank installed. Leading edge slats were installed along the entire span of the right and left wings, which allowed the airplane to be flown at a very high nose-up pitch attitude.

It was possible for the airplane to climb at a very steep angle, which could put the carburetor higher than the wing tanks. With inadequate fuel pressure to deliver fuel to the carburetor, it is possible that a gravity feed fuel system might experience a disruption of fuel flow in high nose-up pitch attitudes; given the lack of any mechanical anomalies with the engine, it is likely that the loss of power was the result of a disruption of fuel flow during the climb.

Verbatim NTSB analysis and probable cause from the NTSB dataset