"I thought you were asking about the GPS. Setting to the CDI on the GNS does not require an active VOR, so you lost me there."
I'm really sorry if I was not clear. If I just use the 530 to input my flight plan in the 525 (forget the FMS, say), and then I look at the HSI, if the GNS has VLOC set, the HSI will probably reference a VOR as tuned in the NAV part of the GNS, I suppose. In some HSI's the needle goes green. Some planes have a NAV/GPS switch on the panel, but that often (in X-Plane, usually!) just does the same thing as pressing the button on the 530 to switch to GPS. What I was trying to get across was, if I switch the GNS to display GPS (which, again, in many later HSI's turns the needle to magenta), will that have the same effect - not necessarily with a colour change of the needle)? Will the AP now be following the 530's GPS course? As I saw the plane last night, the panel switch was for NAV/FMS, as I remember it, but had no refernce to the GPS installed (in that case, the TDS ones).
So, in effect, the 530 will tune the radios (COM and NAV), and may affect the HSI in VLOC (?), but just be for situational awareness/decorationn as far as its GPS capabilities are concerned. Or am I wrong?
Thanks for looking at this. I'll buy the 525 anyway