AD 63-22-03

63-22-03 MARVEL-SCHEBLER: Amdt. 636 Part 507 Federal Register October 30, 1963. Applies to All MA4-5 Carburetors Not Having the One-Piece Combination Primary and Main Venturi and Used on the Following: Continental O-470 Series Engines Installed in Cessna 180 and 182 Series Aircraft; Continental GO-300 Series Engines Installed in Cessna 175 and P172 Series Aircraft; Lycoming O-540 Series Engines Installed in Aero Commander 500 Series Aircraft, Piper PA-23-250 Series Aircraft and Piper PA-24 Series Aircraft; Lycoming O-360 Series Engines Installed in Piper PA-24 Series Aircraft, Beech 95 Series Aircraft, and Mooney Mark 20 or 21 Series Aircraft; and Franklin 6A4-165 Series Engines Installed in Stinson 108 Series Aircraft.

Compliance required at next carburetor removal or overhaul of either the carburetor or engine whichever occurs first after the effective date of this AD, on all carburetors not having the one-piece combination primary and main venturi installed. Carburetorshaving the one-piece combination primary and main venturi installed are identified by the letter "V" stamped on the nameplate.

The primary venturi may become loose resulting in wear of the primary venturi support legs on the ends contacting the carburetor body and at the retaining clip area. As a result, the retaining clips may become dislodged or dislocated and wear may progress to the point the venturi becomes dislodged or dislocated. This can cause erratic engine operation or complete engine stoppage. To preclude this, accomplish the following:

Replace the existing primary and main venturi with a one-piece combination primary and main venturi of the correct part number for the carburetor involved. When accomplished stamp the letter "V" on the carburetor nameplate below the serial number.

(Marvel-Schebler Service Bulletin No. A4-63, Lycoming Service Bulletin No. 297, and Continental Motor Service Bulletin No. M63-18 cover this same subject.)

This directive effective December 2, 1963.