The pilot reported that, as the Cessna 172 approached the runway at the airport in Houston after a short personal flight, the engine lost power.
He checked the fuel valve, mixture, and engaged the starter, but engine power was not restored.
The airplane was “headed directly toward a concrete revetment on the south bank” of a creek, so he banked the airplane left, and it subsequently landed in the creek.
During recovery of the airplane, the fuel selector was found in the “both” position, and the throttle, mixture, and carburetor heat controls were found in the “forward” (off) position.
Examination of the wreckage revealed no evidence of any preaccident mechanical malfunctions or failures that would have precluded normal operation.
The atmospheric conditions at the time that the engine lost power were conducive to serious icing at any power, moderate icing at cruise power, and serious icing at descent power. Given the evidence, it is likely that carburetor ice accumulated during the flight and the pilot did apply carburetor heat, which resulted in a loss of all engine power.
Probable cause: The pilot’s failure to apply carburetor heat while operating in an area conducive to carburetor icing, which resulted in a total loss of engine power on approach and subsequent forced landing into a creek.
NTSB Identification: CEN19LA015
This October 2018 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Three reasons for applying carb heat prior to reducing power.
1. You get instant large RPM drop if you pull the mixture by mistake, easy in older Cessna 172s with little dissimilarity between mixture and carb heat knobs.
2. You get a burst of heat before the air gets cold.
3 In the engine failure case the carb heat is a source of alternate air should the main air filter become blocked.
Good lessons.
People do not realize how fast that heat muff cools down when the engine quits. There may not be any significant heat even if you do apply the carb heat. That’s why it is the first step and should be done immediately as Warren says. Also, I was taught that during the run up befor take off, you should leave the carb heat on for 10 or 15 seconds to clear any ice that may have accumulated during taxi. If the rpm goes down, and then comes back up, you had ice.
You’re right Bob sad those lessons are not always taught today
Incredible. For C172’s, the carb heat should be applied before reducing the rpm below the green arc, so that should be done on the downwind abeam the aiming point. As the POH says, if there is engine roughness or loss of rpm, it is a sign of carb icing. The carb heat is the first system item on the restart checklist. It should be immediately applied without question.