46-36-01 CONTINENTAL: (Was Mandatory Note 8 of AD-675-2: 11 of AD-728-1; 2 of AD-751-1; 1 of AD-761-2; 6 of AD-718-6; 9 of AD-737-1; 1 of AD-759-3; 11 of AD-729-1; 8 of AD-720-1; 2 of AD-611-1; 9 of AD-725-1; 11 of AD-691-1; 9 of AD-703-1; 5 of AD-740-1; 9 of AD-725-1; 10 of AD-694-4; 6 of AD-709-1; 8 of AD-730-2; 8 of AD-746-1; and 11 of AD-696-3.) Applies to Aeronca 65-CA; 65-TC, 65-TAC, YO-58; O-58A, O-58B, SO-58B; 11AC; Air Products (Erco) 415-C, 415-CD; CallAir S-1A; Champion 7AC, S7AC; Commonwealth (Rearwin) 175, 180, 185; Northwestern (Porterfield) CP-65, CS-65; 75C; Piper AE-1, HE-1; J3C-65, J3C-65S; J4, J4A, J4A-S; J4E; J5A, J5A-80, J5C; Silvaire (Luscombe) 8, 8A, 8B, 8C, 8D, 8E; Stinson HW-75, 10; Superior (Culver) LCA; Taylorcraft DC-65, DCO-65; Universal (Taylorcraft) BC, BCS, BC-65, BCS-65, BC12-65, BCS12-65, BC12-D, BC12-D1, BCS12-D1 Airplanes Having Continental A-65 Series Engines With Serial Numbers From 3456658 to 4109568, Inclusive; or Continental A-65, A-75, or A-80 Series Engines Which Have Had A-21422 Piston Pins or New 3-Ring Pistons Installed Since September 25, 1945.
Compliance required immediately if possible, but in any event not later than 50 hours of engine operation after August 27, 1946.
A certain percentage of piston pins installed in engines of the above numbers and distributed as replacement parts are subject to failure without warning. The weakness of these pins cannot be detected by normal inspection methods. Piston pin breakage can result in complete engine failure. It is the owner's responsibility to avoid this risk by making the changes outlined in (a) and (b) at the earliest possible time.
(a) Replace piston pin P/N A-21422 (0.626 inch inside diameter) with thick wall piston pin No. A-25127 (0.5945 inch inside diameter). The engine manufacturer has given assurance that every possible effort will be made to supply the required quantity of replacement piston pins.
(b) Simultaneously with (a), all pistons should be examined for skirt cracks and the necessity for rework of the bottom rib. This rework involves reducing the height of the rib until it is at least 1/16-inch wide and rounding all sharp corners.
(c) As an acceptable alternate to (a) and (b), cam ground pistons, P/N 40731, which necessitate using piston pins of greater outside diameter, may be installed. This change will likewise remove the possibility of piston pin failure and piston skirt cracking.
(Continental Motors Service Bulletin M46-6 covers this same subject.)