AD 53-09-04

53-09-04 CONTINENTAL: Applies to All Aircraft Equipped With Continental W-670-9A (Ordnance-Tank) Engines and Ground Adjustable Propellers Having Blades 11C1 (Hamilton Standard Model Designation) or 4350, 4350F, or 4350F1 (Navy Model Designation.) Compliance required not later than May 15, 1953. In the absence of suitable propeller vibration stress data, the following precautionary measures should be taken to minimize the possibility of propeller blade fatigue failures: (1) Disassemble propeller and inspect for cracks by etching the shank areas of the blades under the hub clamp rings. (2) Cut propellers to between 102 inches maximum and 100 inches minimum diameter. (3) Set blade angle so that static r.p.m. is between 1,500 and 1,975. (4) Install propeller on engine in the zero degree position (blades in line with crankthrow). (5) Placard airplane, "Do not exceed 1,900 r.p.m. for all operations except takeoff." (6) Remove all nicks and gouges from tip region andmaintain propeller blades as outlined in Civil Aeronautics Manual 18.