CJ3/CJ4 driver; I agree with the above. Only thing I'd add is to be in APPR when shooting a LOC to get it to auto-sequence to green needles, then once it's sequenced to green needles, go back to NAV so it won't possibly pick up an errant GS and blow through your MDA (I think the book, at least the FSI training manual, has words to this effect).

Refresh my memory...will the switch to green needles only happen when in apprch? I can't recall ever doing a stand alone localizer approach sine flying the airplane.

Must have FMS as active Nav Source AND have APPR selected for the Nav-to-Nav transfer to occur.

Edited to add that the Loc will NOT auto-tune unless your Nav Source is FMS to begin with.

What aircraft is this on?

As another person mentioned, there can be significant differences from one aircraft or manufacturer to another. I'd suggest checking with your training provider or the aircraft manufacturer on this.

In the King Air, you fly a precision approach in APP or APP/VNAV. Non-precision approaches are flown in NAV or NAV/VNAV.

Also, the PL21 in the King Air only has green needles.....green for FMS, green for VOR/LOC. None of that silly color coded stuff so you can tell when a change happens. Confusing, huh?

Unless you've got a single FMS.

If PFD1 & 2 are looking at the same Nav source, such as both on VOR1 or both on FMS w/a single FMS then they'll be green and yellow.

But I know what you mean!

People fly with only 1 FMS?! Scary stuff

Ha, I know, right?

You guys have two FMS Units in the King Air? Not a Garmin 500 that the manufacturer labels FMS II, but x 2 FMS 3000's?

All true, as far as I can recall. Not many LOC-only approaches in my experience; they definitely fall into the "weird" category when it comes to making the FMS magic work.

Optional, not sure which models are standard though, if any.