What was found
(CAN) DURING PROGRESSIVE CARE OPERATION NR 2, INSP OF THE CARBURETOR HEAT BOX (P/N 05521644) REVEALED THAT THE 2 ALUMINUM RIVETS THAT HOLD THE FLAPPER DOOR TO THE ACTUATOR SHAFT WERE VERY CLOSE TO SHEARING OFF. IF THE ALUMINUM RIVETS DID SHEAR, AND THE AC WAS FLYING IN CARBURETOR ICING CONDITIONS, ENGINE FAILURE COULD OCCUR. THERE IS ALSO THE CONCERN OF PIECES OF RIVETS BEING INGESTED INTO THE ENGINE. THE CARB AIR BOX WAS PURCHASED NEW FROM MFG, INSTALLED 16 MONTHS AGO AND IN SERVICE ON THIS ENGINE FOR 704.7 HRS. NOT SO LONG AGO, MFG USED STEEL RIVETS INSTEAD OF ALUMINUM. THIS DID NOT SEEM TO BE A PROBLEM IN THE PAST WITH STEEL RIVETS. (TC NR 20061123005)