AD Issued on Lycoming Engine Carburetors
February 24, 2012 - The FAA has issued an airworthiness directive (AD) on carburetors installed on many Lycoming engines. The AD targets only 409 carburetors - but 10,700 engines must be inspected to determine if they have one of the defective carbs. Effective date for the AD is March 27, 2012. (Click here to view the AD.)
The problem is with Marvel-Schebler carburetors built with a "machined-from-billet" body instead of the more common die-cast body. In some of the defective machined body carbs the mixture control has failed, blocking fuel to the engine and causing power loss.
The AD requires aircraft operators to have the carburetor inspected to determine if it is machined or die-cast. If the carb is the common die-cast type no further action, except recording the inspection, is required. If the carb is the machined type, a remedy is to replace it with an airworthy cast type. Or, you can click here for Service Bulletin 18, Revision A for options to repair the problem.
The name of the company that has manufactured the carburetors changed from Marvel-Schebler to Facet Aerospace to Precision Airmotive to most recently Volare, but all carburetors of the type specified are included in the AD.
The AD requires that the carburetor on the affected Lycoming engines be inspected within 50 flight hours of the effective date (March 27).