The sport pilot reported that, as he was approaching the runway at the airport in Hilton Head, S.C., he retarded the throttle and descended from 1,300′ to 1,000′ mean sea level.
He added that, a few seconds after retarding the throttle, the engine “ran rough” for a few seconds and then lost all power and would not restart.
He did not attempt to apply carburetor heat, configured the Flight Design CTSW for best glide speed, and maneuvered for a forced landing on a golf course. After landing, the left wing hit a tree.
Post-accident examination of the airframe and engine revealed no evidence of preimpact mechanical failures or malfunctions that would have precluded normal operation, and there was sufficient fuel onboard at the time of the accident. A test run of the engine revealed no anomalies.
Given that the weather conditions at the time of the accident were conducive to serious carburetor icing at glide power and the pilot chose not to apply carburetor heat after the engine initially lost power, it is likely that the engine lost power due to carburetor icing.
Probable cause: The pilot’s failure to apply carburetor heat following a loss of engine power due to carburetor icing.
NTSB Identification: ERA16LA148
This April 2016 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.
Not mentioned? The effect of motor malfunction causing panic in pilot which precludes proper action of switching on carb heat. Panic kills.
Some engines are very prone to carb ice and some are less effected, but all engines can develop ice. The carburetor that is mounted on a manifold is more prone than an engine with the carb mounted on a hot oil sump.
But a carb is a refrigerator because gasoline is vaporized which makes the cooling caused by the venturi pale. Fuel injection systems use venturi that are less extreme but the refrigerant effect of gasoline conversion from liquid to vapor doesn’t happen in the venturi [pressure carbs excepted].
Carb heat needs to be applied before closing the throttle, while the engine is producing heat.
Carb heat only works on a running engine. High temperature and high humidity lead to carb ice because cold winter arctic air is dry. The venturi may drop temperature 10-20 degrees but the evaporating gasoline will drop the temperature 60 degrees. Carb ice may not be a problem in Death Valley when it is 120 F. But when it is 80-90 degrees F in Illinois, Florida or Texas carb ice happens.
Your POH and several FAA and mfg’r SB have the answer, .
Well said Jim! Often in my long aviation career I have seen instances where carb heat would have kept an accident from happening.