Airworthiness Directives; Precision Airmotive Corporation Carburetors

This amendment supersedes an existing airworthiness directive (AD), applicable to Precision Airmotive Corporation carburetors, that currently requires the inspection of those carburetors equipped with a two-piece venturi at each annual inspection to determine if the primary venturi is loose or missing, and requires the replacement of a two- piece venturi with a one-piece venturi within 48 months after the effective date of the existing AD. This amendment eliminates the requirement to install a one-piece venturi, and allows the installation of a one-piece venturi on affected carburetors as an optional terminating action; or, requires repetitive inspections of a two-piece venturi on affected carburetors. This AD also adds an additional carburetor model, and requires the installation of a new fuel nozzle on certain carburetors when a one-piece venturi is installed. This amendment is prompted by service difficulty reports describing engines that fail to attain rated power, run rough, or experience power loss after installation of a one-piece venturi in accordance with the existing AD, and by incidents of forced landings of aircraft powered by engines modified to comply with the existing AD. The actions specified by this AD are intended to prevent disruption of fuel flow to the engine resulting in failure to attain rated power, power loss in flight, and forced landings.