CEN20LA042 · Cessna 172 M

The student pilot and his flight instructor completed an uneventful 15- to 20-minute flight in the airport traffic pattern before the flight instructor deboarded so the student pilot could continue on his first solo flight. The engine was not shut down while the flight instructor deboarded the airplane. The student pilot then taxied to the hold-short line for the runway where he completed an abbreviated before takeoff check, which included verifying that elevator trim was positioned for takeoff, carburetor heat was turned off, flaps were fully retracted, and that the fuel mixture control was full rich. The student pilot did not complete an engine runup before takeoff.

The student pilot stated that after takeoff, the airplane climbed to about 200 ft above the runway where the engine began to splutter briefly before a total loss of power. The airplane sustained substantial damage to the fuselage and both wings during a forced landing in a wooded area.

The flight instructor stated that he taught his students to pull the mixture control knob aft about 1 1/2 inches during taxi to avoid fouling the sparkplugs. The flight instructor recalled that he told the student pilot to lean the fuel mixture while they taxied back to the ramp at the completion of their dual-instruction flight. The flight instructor stated that shortly after the accident, the student pilot told him that the mixture control was pulled aft about 1 1/2 inches and that the carburetor heat control was on.

The student pilot subsequently reported that that he did not lean the fuel mixture during taxi and that leaning typically was only completed during cruise flight. Additionally, before he exited the airplane, the student pilot turned off the electrical master switch and both magnetos, repositioned the fuel selector from both to off, and pulled the mixture control knob full aft.

Postaccident examination revealed uncontaminated 100 low-lead aviation fuel present in the fuel strainer and the carburetor bowl. There was no evidence of fouling or excessive carbon deposits on the sparkplugs that would have prevented normal engine operation. The lack of fouling or excessive carbon deposits on the sparkplugs was consistent with a proper air-fuel mixture and normal carburetor function during the flight. Additionally, a postaccident engine test run did not reveal any mechanical anomalies with the engine that would have prevented normal operation during the flight.

Although the carburetor heat control system did not function properly during the test run, the sparkplugs did not exhibit features consistent with a carburetor icing situation that would have resulted in an excessively rich air-fuel mixture had the airflow through the carburetor venturi become restricted due to carburetor icing during the flight. Additionally, the engine test run confirmed that while at maximum static speed, the engine would stop running due to fuel starvation with the mixture control knob moved aft about 1 1/2 inches. It is likely that the student pilot did not reposition the mixture control to full rich before takeoff, which resulted in a total loss of engine power due to fuel starvation.

Verbatim NTSB analysis and probable cause from the NTSB dataset