Further enquiries suggest that the KFC230 probably does not require GPS to fly an ILS.
Only the GFC500 seems to, with the GFC600/700 using GPS for performance improvement.
Emir wrote:
What if I hand fly then turn on autopilot in NAV mode choosing ILS as source without loading the approach from database? Do I still need valid GPS position for GFC500 to fly the approach?
According to the POH any vertical guidance requires a valid GPS position. So the answer to your question is yes: Also in that case you can’t rely on working vertical guidance.
From the GFC500 AFMS (this for a PA28-181):
LOSS OF GPS INFORMATION
(GPS position information is lost to the autopilot.)
NOTE
If GPS position data is lost while the autopilot is tracking a GPS, VOR, LOC or BC course, the
autopilot will default to roll mode (ROL). The autopilot will default to pitch mode if GPS
information is lost while tracking an ILS. The autopilot uses GPS aiding in VOR, LOC and BC
modes.
Yes GFC500 goes to ROL/PIT mode if you lose GPS on LOC/GS, also when switching NAV1/NAV2 source even if both are on same ILS Freq or after any glitch on VHF signal, no drama just press APP 
Seems to me GFC500 needed more careful watch than GFC700, but it’s a good thing to keep and eye on the AP anyway, both are luxury compared to what I have now on my mount…
So, to recap, does all that mean that if I replace my KFC150 with a GFC500, I won’t be able to fly a LOC / GS coupled ILS approach down to DA in case my GPS source is unavailable ? So if the GNS / GTN is offline/out/down, I am also out of any other instrument options ? Or did I misunderstand something ?
EuroFlyer wrote:
So, to recap, does all that mean that if I replace my KFC150 with a GFC500, I won’t be able to fly a LOC / GS coupled ILS approach down to DA in case my GPS source is unavailable ? So if the GNS / GTN is offline/out/down, I am also out of any other instrument options ? Or did I misunderstand something ?
You can’t fly it coupled, but you can fly it manually.
@EuroFlyer post moved to existing thread.
The answer is Yes. The GFC500 needs GPS reception to fly ILS or, presumably, LOC.
And if the GPS is gone then, ahem, you can’t fly any GPS approach either
And this applies to the GFC500 and also to the KFC230 / Aerocruze ? Or only the Garmin (because of the source you quote on page 1) ?
You can’t fly it coupled, but you can fly it manually.
Sure; lack of GPS doesn’t prevent the NAV radio itself working, so you will still have the CDI bars doing the right thing – if you have a conventional CDI installed in your primary field of view (the CDI presentation on a GPS in the centre stack doesn’t count; I believe). And, presumably, the flight director too although I am not sure about that since the FD is generated by the autopilot, not by the “navigator” and is what is used to drive the servos, more or less.
And this applies to the GFC500 and also to the KFC230 / Aerocruze ?
The KFC230 seems to not have any GPS input, according to a source I have.
Bringing this up again.
I recently flew to Vienna, LOWW, and had prepared for the RNP16 Z approach. It was loaded and ready to go.
Only, the GS didn’t appear.
I remember there was an error message on the GNS530W telling me “not receiving 232 input channel #1”.
Because I had, as backup, set up the regular ILS frequency on NAV1, I could switch to VLOC and the GS markers popped up fine. So I could continue the approach.
This is a KFC150 autopilot, analog, which doesn’t need any additional GPS source. It can sail down the ILS just fine by itself.
As it turns out, there is an extra altitude sensor for the GPS which seems to have either gone or the wire has an issue, causing the error message. I didn’t know it when I set up the RNP, but I know now after a phone call to Avionik Straubing.
Now, if I’m not completely mistaken, with a Garmin GNC500 autopilot I WOULD NOT HAVE BEEN ABLE TO PROCEED, given that this device cannot fly an ILS without external GPS altitude source !! The GPS altitude sensor is a single source of failure in combination with a GNC500, effectively rendering BOTH the RNP and the ILS useless in case it quits.
I don’t know if you would at least the glide slope somehow, to fly it manually. I didn’t want to try that out.
Just raising the flag here, this has the potential to bite you, so be aware.
