Accident Summary
On March 24, 2022, at approximately 1730 central daylight time, a Cessna 172N airplane, registration N733KP, was substantially damaged when it came to rest inverted in a field near Springtown, Texas. The flight instructor was not injured, and the student pilot sustained minor injuries. The airplane was being operated as a Part 91 instructional flight.
Flight Details
According to fuel transaction records, at 1657:45, the flight instructor purchased 7.5 gallons of 100 low-lead fuel from a self-serve pump at Bridgeport Municipal Airport (XBP) in Bridgeport, Texas. The instructor stated that the fuel tanks were already “pretty full” when she added the fuel. Approximately seven minutes after departure from XBP to the south, while in cruise flight at about 3,500 feet mean sea level, the engine sputtered and the airplane was unable to maintain altitude. The flight instructor took control from the student pilot and performed troubleshooting steps, but engine power was not restored. ADS-B data showed the airplane made a right descending turn then continued descending on a straight path.
Pilot Statements
The flight instructor reported that during the descent, the propeller windmilled and the engine would intermittently catch and operate for a few moments before dying again, indicating the issue could not be remedied in the air. She noted the fuel selector valve was positioned to BOTH and was not manipulated during the event. She did not remember the tachometer RPM and did not apply carburetor heat while troubleshooting. The student pilot stated that when the throttle was pulled to idle, the engine smoothed out somewhat but would start missing when throttle was pushed forward.
Postaccident Examination
During the forced landing, the airplane nosed over and came to rest inverted, resulting in substantial damage to the fuselage, empennage, and both wings. Fuel was leaking from the wings after the accident. The airport manager at XBP reported that the fuel source was checked for contaminants and none were found; two other airplanes fueled from the same source around the same time reported no issues. Atmospheric conditions at the time were not conducive to carburetor icing. A postaccident examination revealed uncontaminated blue fuel inside the carburetor and fuel strainer bowl. The propeller rotated with no binding, all pistons and rocker arms moved normally, suction and compression were obtained from each cylinder, and spark was produced from ignition wires. No mechanical malfunctions or failures that would have precluded normal operation were found.
Probable Cause
Not determined by the investigation report.