For terminal/enroute flight you have to have a CDI. I have the UPS GX55
and love it. I only have one CDI in the plane and it has a switch to go
back and forth between the ILS radio and the GPS. If you have two CDI's
you can have your shop rig up a switch to your VOR only CDI. You will
also need the annunciator if you go the switch route. If you go with
the CDI designed for the GPS it will have the annunciator built into the
face of the CDI.

Stephen Merrifield wrote:
I seem to be having a hard time grasping this...

My ADF has taken a nose dive for the final time and I'd like to install an
IFR GPS to be able to use it in lieu of an ADF and DME and the moving map
would be nice as well. ( I fly with a handheld Garmin 196 already ). So
here's my problem. I think I'm about two years away from installing a whole
new avionics package with a MFD etc... So, I'd like to keep my costs down to
a reasonable level at present but still have a very workable system that
gives me the option of a /G flight plan. GPS approaches are not what I'm
really after here. I'm getting conflicting advice on whether I need a system
with the annunciator and an OBS for the GPS or can I have the 89B ( or
similar model ) installed and simply use the readout from the face for legal
IFR enroute flight? Or am I going about this all wrong to start with? Having
never flown an aircraft with an IFR approved GPS, I'm kinda confused about
what to do. The cost between the two setups is substantial.