this invention relates to a clutch mechanism for selective power transmission between starter means and an engine . more particularly , the invention discloses a dual clutch mechanism for use in selectively coupling a turbine driven starter assembly with a gas turbine engine to affect engine start up and disengage thereafter . the invention provides a clutch mechanism , comprised of two clutches in series , which can deliver positive torque transmission from a starter to an engine at any speed within an operating range and disengages at any speed greater than the operating range .