50-18-02 DOUGLAS: Applies to All Model DC-6 Aircraft Equipped With Hamilton Standard 43D60/6841A-O, 6851A-O, and 6873A-O Propeller Blades and R-2800-83AM4, R-2800-83A or CA Type Engines. \n\n\tTo have been accomplished by April 28, 1950. \n\n\tA recent propeller blade tip failure of a Hamilton Standard 43D60/6851A-O propeller on a DC-6 powered with R-2800-CA-15 engines probably resulted from a worn 4 1/2 order engine crankshaft torsional damper P/N 101169. Until further notice or until the engines are known definitely to comply with P&W Service Bulletin No. 1033 dated November 30, 1949, all DC-6 aircraft using Hamilton Standard 6841A-O, 6851A-O and 6873A-O blades and R-2800-83AM4 or CA type engines shall be placarded to avoid all operation between 1,800 and 1,975, between 2,025 and 2,175 and between 2,225 and 2,450 r.p.m. Only acceleration and deceleration through placarded ranges shall be permitted. For gross weights above 80,000 pounds, 2,450 r.p.m. is permissible for normal climb. For gross weights below 80,000 pounds, climbing r.p.m. between 2,450 and 2,600 permissible. For gross weights above 80,000 pounds avoid operation above 2,450 r.p.m. except for takeoff and emergencies. For R-2800-83A engine installations, operating restriction presently covered in Aircraft Specification A781, Note 5C (1) applicable and until further notice operation between 1,800 and 1,975 and between 2,025 and 2,175 shall be prohibited.