Float-Type Carburetors Indicated In Engine Fires

The FAA has issued a Special Airworthiness Bulletin for  potential hazards associated with normally-aspirated carbureted engines. However, they say that for the time being, the airworthiness concern is not an unsafe condition that would warrantan AD.

The SAIB results from reports of numerous accidents and incidents over the past 20 years that resulted from an engine stoppage or engine fire involving float-type carburetors. Numerous service information letters (SILs) and service bulletins (SBs) were issued during that time to address float-type carburetor issues related to poor idle cut-off and fuel leaking from the carburetor after engine shutdown.

The FAA issued SAIB CE-06-33R1 in April 2006 to address those conditions. These conditions are often the result of fuel leaking into the carburetor float, a damaged or worn float, or a damaged or worn float valve. Despite the availability of the SILs and SBs, the FAA is still receiving reports of accidents and incidents resulting from carburetor float anomalies. In comparison to the SILs and SBs previously issued, the SAIB is applicable to all aircraft with reciprocating engines with float-type carburetors installed and provides more detail and focaused recommended actions.

The SAIB says pilots should examine the engine area for evidence of fuel leakage during pre-flight inspection . During engine start, be alert for carburetor flooding or the need for excessive leaning. Hard starting might be an indicator of a deteriorating or damaged carburetor float. During engine operation, excessive fuel consumption and/or poor idle performance might indicate a deteriorating or damaged carburetor float. Difficulty shutting down the engine with the mixture cut-off control might be an indicator of a deteriorating or damaged carburetor float. If any of these conditions are observed, the pilot should have qualified maintenance personnel inspect the aircraft before the next flight.

FMI: www.faa.gov