CPL - Coupled mode. This mode is a generic way to name all modes that are Coupled to something like a TACAN, and ILS or a WAYPOINT. What you are coupled to, depends on the mode that has been selected on the HSI screen. To change Coupling mode, select either "TCN", "ILS" or "WPT" on the HSI, to toggle between modes. NOTE: Of course, to use WPT mode, you first have to create a flight plan! Without a flight plan, the only modes available for coupling will be TCN and ILS.
Guess you missed this mode ! ( Taken from a new article on the F-18c secs and avionics systems. )
The KA-50 does have a waypoint follow autopilot mode although clunky. As for the A-10 it dose not. But the real world A-10 warthog Does.