Preprogrammed in flight plan with an ILS landing - PFD display is AP/NAV and all working correctly. When I get in range of the localizer when ILS landing will it automatically change from FMS/GPS to LOC when the signal is picked up or do I manually have to change it? Is it the same across all AP systems or vary by system/aircraft? Any help is appreciated. Thanks.
Which aircraft are you referring to? On the A320, you have to press the APPR button manually to arm the LOC and G/S which will engage as soon as it can lock onto the signal.
I’m not sure how to for the other aircrafts though.
Sorry, I only fly GA aircraft at the moment so I was referring to the TBM or 350i. I know the APR button must be pressed manually to engage but I’m referring to the PFD showing FMS/GPS when the localizer signal is picked up. Does the FMS/GPS displayed on the PFD automatically change to LOC or do I need to manually change it?
Well, I’m only good with Airbus systems. I don’t know anything about GA aircraft systems, so I’ll leave it for the more knowledgeable people to answer your question. Best of luck.
IIRC the Garmin systems should also switch from FMS to NAV1/LOC on the final approach, though I mostly fly VFR when doing GA so I haven’t practiced it as much.
If you set up the flight plan, it should preprogram NAV1 to the right frequency as well, but I always recommend double-checking it against the chart before you arrive. 
Thanks Vibstronium!
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Since you receive a reliable ILS signal at 10-15NM, it doesn’t hurt to switch from GPS to NAV manually latest at 10NM if it doesn’t happen automatically.
Not sure if there’s any ILS info displayed on the PFD if you, or the aircraft, don’t switch from GPS to LOC.
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I’ve found the automatic switching rather hit or miss when I tried to use it. Sometimes it works, sometimes it doesn’t when it should.
I just punch in APR and switch to LOC mode manually. That way, I know for sure it’s done correctly and don’t rely on questionable system to do it for me.
Just checked with the TBM:
- Switch from GPS to LOC.
- Check that LOC1 and the GS diamond are displayed.
- arm the APR mode.
With NAV in GPS you don’t get any ILS info on the PFD.
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As noted by others, automatic switching from GPS to NAV1 / NAV2 (whichever one is dialed into the ILS frequency) can be hit-or-miss. It doesn’t hurt before the FAF to switch manually.
In theory, it should automatically load the ILS frequency into your nav radio as well as those other functions. I’ve had it fail all those steps far too often for me to trust it. I look up my ILS frequencies, manually enter it into standby and then switch everything manually.
Maybe some day things will work as intended every time and we can fly care-free knowing everything is going to work as it’s supposed to. But today is not that day.
As PZL104 has said, with the TBM there is no automatic switching of Nav modes, and it’s best to preset the ILS frequency in the radio in good time to avoid playing catch up.
This is also the case when intercepting the localiser in AP HDG mode when being vectored or cleared direct to the FAF pressing the APR mode won’t capture the localiser unless first manually changing to Nav mode briefly.
In my experience the AP should automatically change from HDG to Nav LOC mode when APR is armed and the aircraft is receiving the signal.
Just did a flight yesterday in the CJ4, which may be similar.
I planned it in the World map, using IFR and choosing an ILS landing
In the plane, I checked there was a frequency for NAV1 (ILS frequency)
Once in range of LOC, I changed from FMS to VOR/LOC
Once on the approach, I pressed the APPR button for the plane to follow the glideslope.
From my understanding, FMS and GPS are the same and have to be switched to NAV/VOR in order to ILS working
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I’m like 99% sure I’ve had the G3000 in the TBM 930 auto switch from FMS to NAV/LOC on multiple ILS landings. Are you sure it doesn’t ever happen?
When it works, it will automatically enter your ILS frequency in your NAV1, switch it to your active channel, then switch your CDI to LOC1. The G1000 will do the same.
The issue is that it doesn’t work reliably. Sometimes it works, sometimes it doesn’t.
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I know that in the WT-modded CJ4 the misses happen with some (all?) add-on airports because the mod cannot look up the ILS frequency for some reason. At least that’s what Matt from WT said in the excellent CJ4 tutorial he made together with FilbertFlies, and I have since confirmed that it doesn’t work in Tampa’s EKCH Copenhagen add-on.
Maybe it’s a related issue?
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It’s certainly possible that custom airports play a role, but it also happens on stock airports. I fly into KOPF pretty often, and it’s stock scenery. The FMS switching itself automatically is as hit or miss there as anywhere else. Same for other stock airports I fly into.
That’s why I just got into the habit of doing all my stuff manually. There’s far less of a margin of error that way.
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I just so happened to perform an ad-hoc Localizer only approach last night simulating a weather divert. I cleared the plan by doing a Direct-To to a GPS NavPoint that was far enough and lined me up (as closely as possible) with the desired approach end to the alternate field. Before I got there, I dialed in the LOC frequency on NAV1, but remained on GPS. Once I got to within 1nm of the reference point, I switched to NAV1 and changed modes from NAV to APR. The FMS captured lateral guidance correctly (Green Arrow), and I manually managed the altitude to get set up for a three mile final to touchdown.
The above is an exception case to your original question, but it’s one of the ways where manual intervention is required to switch FMS guidance. It all works together and well - but you need to experiment to get familiar with how the navigation systems are going to behave or react.
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Just tried it again, think this is a recent bug, still not happening for me. Used to be fine, just like the real thing.