Abstract: An expandable spar filler block device for use in combination with a spar member of an articulated main rotor assembly of a helicopter. A preferred embodiment of the device includes first and second filler members and an expansion mechanism. Each filler member includes a spar engagement surface that is complementary to the inner mold line (IML) surfaces of the spar member and first and second tapered surfaces. The expansion mechanism for the preferred embodiment of the expandable spar filler block device is a pull shim that includes a first segment and a constant tapered segment having tapered surfaces that are complementary to the first tapered surfaces of the filler members.