I saw this on another board, thought I’d share if anyone is debating getting a GFC 500

From a Garmin rep:

“ It is correct that the GFC 500 will not remain in LOC/VOR and GS modes in the event of a complete GPS signal loss and the autopilot would revert to ROL and PIT. However, you will still be able to put it into HDG mode, as well as to climb/descend/maintain altitude using IAS, VS and ALT modes.”

Meaning it couldn’t fly you down on a ILS even or navigate to anything even a VOR

With how easily it is to implement and the growing amount of GPS jamming and spoofing, combined with how worried governments are after seeing what the common man can do with a drone, I see GPS jamming and spoofing increasing over the years. Like it wouldn’t surprise me if stateside TFRs incorporate jamming in the near future.

I’d recommend not spend good money on a GFC500 if one is in the market for a auto pilot, look at the GFC600 or other systems that don’t have this major flaw


https://static.garmin.com/pumac/190-02291-06_10.pdf


I’m not 100% sure but I think you might also lose your flight director, as I believe that’s AP driven, so you’d be hand flying a raw data approach if GPS signal is lost

That’s one heck of a failure mode, and anyone with a GFC500 should be practicing hand flying raw data approaches, as well as driving the plane around in hdg/IAS mode while manually adjusting for their CDI indications while in cruise and the terminal area

Another pointer, I would be very sure to have your hands on the controls following along and monitoring your score board while this autopilot flys ANY approach
If you’re shooting a ILS to mins and the GPS glitches the AP is going instantly drop to pitch & roll mode, that might be a bit of a pucker factor if Murphys law comes into play and it happens on that proverbial dark stormy night when you’re in the soup and only 300’ AGL

I wouldn't dream of shooting an approach without guarding the controls no matter the autopilot. Every approach I've ever done in the 737 has my hands on the controls as pilot flying regardless of the state of the AFCS panel.

I'll admit a lot of ignorance with GA autopilots as I've never used one. Is it common for your average GA autopilot to be capable of coupled approach with ground based NAV? (Loc/GS)

Halestorm wrote:I wouldn't dream of shooting an approach without guarding the controls no matter the autopilot. Every approach I've ever done in the 737 has my hands on the controls as pilot flying regardless of the state of the AFCS panel.

I'll admit a lot of ignorance with GA autopilots as I've never used one. Is it common for your average GA autopilot to be capable of coupled approach with ground based NAV? (Loc/GS)

Most folks at the pro level have seen enough to guard the controls, I do in the larg jet I fly, but I’ve also seen a few folks who have a wee bit too much faith in systems lol

Lots of the modern GA APs will do a coupled approach all the way through a coupled missed, very on par with what you’ll find in a Boeing capabilities wise, minus the redundant systems and vnav on the climb / auto throttles. They will shoot a ILS, LPV, VOR with a pseudo glide path to hit the constraints, etc

The newer garmins will climb in pitch, VS, airspeed mode, can to heading or track, TOGA, many even have a feature that will roll wings back if you bank beyond 60 degrees I think, heck you can even add yaw dampers. Pretty cool having this tech be so available.

Just some of it has some nasty failure modes like this GFC, as the famous red X Aspen PFDs

The issue on the GA side is mostly training, lots of IFR training from instructors who have hardly any IMC time they can teach you all the nitty-gritty details out of the Book but when it comes to coupling up keeping an eye on FMA’s, including outside air temperature in your scan, etc., they lack which makes sense based on average experience

I've been shooting a lot of approaches in the king air, around white sands missile range in southern NM, even in some fairly significant weather with icing. They are jamming the gps almost every week it seems. While I wasn't aware of this limitation of the GFC 500, it will still not deter me from owning one. A coupled approach is nice - but I'm pretty sure I can follow that ILS on the autopilot even with step downs and estimating what vertical descent rate the a/p needs to hang on to the needles. By the time I get to the final segment, the a/p is just gravy. The real benefit of that thing is all the beforehand when I can take my hands off and use the mental cycles to think about other necessary stuff while it does the stick wiggling.

LOC/VOR goes not come with glide path or slope, only ILS does so.

So yes, if you lose GPS or signal, you cannot generate a signal w reliability to perform a GP descent. This is not on Garmin but all navigators.

48Stinson1083 wrote:LOC/VOR goes not come with glide path or slope, only ILS does so.

So yes, if you lose GPS or signal, you cannot generate a signal w reliability to perform a GP descent. This is not on Garmin but all navigators.

Uhh the autopilot won’t navigate/work one way or another with a ILS/LOC/VOR/etc if it looses GPS, lots of other auto pilots don’t have that limitation

Do ANY other autopilots have that limitation?

Belloypilot wrote:Do ANY other autopilots have that limitation?

None that I know of

With the massive leaps in small solid state radio tech, be cool if these APs and navigators had some sort of basic IRS built in, even if it could just do DME/DME, it would be nice in a situation where some asshole jammed, or worse spoofed, our plane that the systems could still keep on keeping on, this is how most proper airliners fly uneventfully through GPS spoofing and jamming

Here’s one over Egypt

Before they jammed us they were sending us a false single almost 200nm from our position






GPS games don’t even require a state actor, it can be done pretty low budget

In 2024 being highly dependent on GPS is not wise especially if you’re going to fly in the soup

All LOC/VOR or ILS/GS approaches are a ground based navigation sources, they are not SBAS/GBAS augmented. I can understand a GPS overlay not providing LNAV/VPATH in APPR mode but all other APPR modes should remain fully functional and the autopilot should be capable to executing the approach regardless of the GPS status. If this is correct it's another example of Garmin not playing nice in the sandbox with others and a very good reason to avoid purchasing Garmin avionics.

Full disclosure, I've flown Collins Proline, Honeywell, Universal, Allied Signal. I've never flown a Garmin avionics suite so my knowledge is limited on their product but what I'm reading isn't very impressive.

For most of us the issue becomes what other autopilots are available for GA aircraft? The GFC 600 only has a few of the GA aircraft on the STC AML, and its almost 3 times the price of the 500. The bendix king 3100 also doesn't have a super lengthy AML. So short of spending a ridiculous amount of funds on an old rate based 55X, you really dont have many options other then the GFC500. Id be happy to hear some if there is, as I'm currently working with a DAR to get approval to have a 500 installed in my old 206. Rather not spend the money if there are other options.

GFC 500 is awesome! I've had mine installed in my 185 since the STC hit the street. I believe I was the second or third 185 to get one installed. I've never had any issues with GPS jamming since I don't fly my 185 to Egypt very often.

It is a fantastic upgrade for any GA aircraft.

MW

I haven't experienced any GPS failures here in the Pacific Northwest. There was a NOTAM a few years ago for the entire GPS system to be down in central Idaho a few years ago. I remember thinking I may need to bring a paper chart with me on the trip. I've seen a few approaches denigrate to LNAV/VNAV when I was expecting LPV.

I love my GFC500 but I also love hand flying IFR and would not feel comfortable going into hard IFR without having the skills to hand fly it in the same conditions. I monitor my PFD with AP engaged just like I would if were hand flying. It would be great if the avionics systems had some internal navigation system as a backup for a GPS signal failure. These systems have been expensive in the past but maybe the next generation Garmin APs will have this feature. MON networks will remain available because of the vulnerability of GPS due to its centralized structure. Having ground based independent systems is a great backup.


Josh

A1Skinner wrote:For most of us the issue becomes what other autopilots are available for GA aircraft? The GFC 600 only has a few of the GA aircraft on the STC AML, and its almost 3 times the price of the 500. The bendix king 3100 also doesn't have a super lengthy AML. So short of spending a ridiculous amount of funds on an old rate based 55X, you really dont have many options other then the GFC500. Id be happy to hear some if there is, as I'm currently working with a DAR to get approval to have a 500 installed in my old 206. Rather not spend the money if there are other options.

It’s odd that the Trio has the 190 and 195 on its AML but not the 206 or 210. Trutrak is even more limited.

Mapleflt wrote:All LOC/VOR or ILS/GS approaches are a ground based navigation sources, they are not SBAS/GBAS augmented. I can understand a GPS overlay not providing LNAV/VPATH in APPR mode but all other APPR modes should remain fully functional and the autopilot should be capable to executing the approach regardless of the GPS status. If this is correct it's another example of Garmin not playing nice in the sandbox with others and a very good reason to avoid purchasing Garmin avionics.

Full disclosure, I've flown Collins Proline, Honeywell, Universal, Allied Signal. I've never flown a Garmin avionics suite so my knowledge is limited on their product but what I'm reading isn't very impressive.

As I mentioned twice, that’s not the case with the GFC500, if it can’t pick up GPS the only modes that work are heading/VS/IAS/pitch/roll, so it’s not able to navigate off ANYTHING

I’ve flown pretty much all the avionics systems and I really like Garmin, the G1000 and up systems have been great, I still love my GNS boxes, etc, but it seems they majorly relied on GPS to “smooth” out the GFC5 to the point it can’t nav or shoot off anything of it doesn’t have GPS, they claim this was a cost savings choice.

My stec might not be a new model year, but it’s like a honey badger, it’ll still fly a VOR or ILS even with nil GPS

With how much our own gov jams up GPS (mostly SW areas) and the increase in other parts of the world, just don’t think it’s going to be getting better GPS wise with how target rich of a environment it as combined with how relatively easy it is to attack those systems

So your clear to fly an ILS approach, GPS coverage fails now what do you do ? How are you going to safely return to Mother Earth either at your planned destination or your filed alternate with a Garmin avionics suite ?

I got my IFR ticket in a bird with twin G5s, a 430W and a king Nav/Com. No AP.
Maybe just me, but I'm having a hard time thinking it's really that big a deal for the rare occasion you're flying an ILS and GPS kicks out to just keep hand flying.
Our IFR bird now has a full Garmin suite including GFC500. It's been fantastic. Thus yet I've only flown it IFR between Washington state and Minnesota, but it's been pretty flawless.
I suppose if I was flying a 4 seat IFR leisure travel Cessna into an active warzone or trying to shoot ILS approaches into restricted bombing ranges I'd feel different. I just have a hard time believing that when most folks have GPS enabled smart phones, watches, etc and GPS is utilized by emergency responders from police, fire, and military that if GPS jamming genuinely affected them in a material way that there wouldn't be an appropriate response.

Mapleflt wrote:So your clear to fly an ILS approach, GPS coverage fails now what do you do ? How are you going to safely return to Mother Earth either at your planned destination or your filed alternate with a Garmin avionics suite ?

Going to have to hand fly it raw data from what Garmin says, not the end of the world, but a whole lot more task saturation for a failure that in other auto pilot systems is a”nothing burger”

DreadPirateWill wrote:I got my IFR ticket in a bird with twin G5s, a 430W and a king Nav/Com. No AP.
Maybe just me, but I'm having a hard time thinking it's really that big a deal for the rare occasion you're flying an ILS and GPS kicks out to just keep hand flying.
Our IFR bird now has a full Garmin suite including GFC500. It's been fantastic. Thus yet I've only flown it IFR between Washington state and Minnesota, but it's been pretty flawless.
I suppose if I was flying a 4 seat IFR leisure travel Cessna into an active warzone or trying to shoot ILS approaches into restricted bombing ranges I'd feel different. I just have a hard time believing that when most folks have GPS enabled smart phones, watches, etc and GPS is utilized by emergency responders from police, fire, and military that if GPS jamming genuinely affected them in a material way that there wouldn't be an appropriate response.

I got my ticket in a old nasty rental with two analog nav coms, two nav heads (only one had a glide slope), no GPS, no iPad, vac driven AI & DG that had its good days and bad days lol

Still there is a reason flying pax IFR in the 135 world you NEED an autopilot or a second pilot.
If a working pilot walks out to the plane and the AP is found to not work, he legally ain’t flying IFR single pilot today.

Part 91 I would have been legal to load my entire family into that old plane I learned IFR in and launch into low IFR at night, l could even take off 0/0 with no nearby take off alternates, but it wouldn’t be prudent nor safe.

My skywagon has a very nice IFR panel in it, the old owner spent that $$ and never started on his instrument ticket, nothing wrong with that, his money his choice, and it worked out great for me. For him a GFC 500 would be fine as it would mostly be panel jewelry

That being said that GFC500 has a failure mode that doesn’t make it a serious autopilot choice if you’re going to be using it in the soup single pilot IMO

I’ve had GPS drop in the US a few times outside of any bombing range of anything like that, GPS failures and outages 100% do happen.

Most consumer stuff can also get its location off nearby wifi (google airhook) and other means, lots of military hardware has other means of navigation as jamming is in their own bag of tricks, larger jets have IRS systems, so it’s a lot different for GA compared to those examples


I would be surprised given the FAA/Feds history if they don’t start using and expanding stateside jamming much like we saw of TFRs after 9/11, I could be wrong

Personally if I was a baller building a new panel, I’d look at the other offerings when it comes to a AP, sometimes the slightly older model is better

Can't legally fly approaches of any sort with trio or trutrak. They are nice autopilots for sure, but definitely much more limited then the gfc500.

NineThreeKilo wrote:

Mapleflt wrote:So your clear to fly an ILS approach, GPS coverage fails now what do you do ? How are you going to safely return to Mother Earth either at your planned destination or your filed alternate with a Garmin avionics suite ?

Going to have to hand fly it raw data from what Garmin says, not the end of the world, but a whole lot more task saturation for a failure that in other auto pilot systems is a”nothing burger”

DreadPirateWill wrote:I got my IFR ticket in a bird with twin G5s, a 430W and a king Nav/Com. No AP.
Maybe just me, but I'm having a hard time thinking it's really that big a deal for the rare occasion you're flying an ILS and GPS kicks out to just keep hand flying.
Our IFR bird now has a full Garmin suite including GFC500. It's been fantastic. Thus yet I've only flown it IFR between Washington state and Minnesota, but it's been pretty flawless.
I suppose if I was flying a 4 seat IFR leisure travel Cessna into an active warzone or trying to shoot ILS approaches into restricted bombing ranges I'd feel different. I just have a hard time believing that when most folks have GPS enabled smart phones, watches, etc and GPS is utilized by emergency responders from police, fire, and military that if GPS jamming genuinely affected them in a material way that there wouldn't be an appropriate response.

I got my ticket in a old nasty rental with two analog nav coms, two nav heads (only one had a glide slope), no GPS, no iPad, vac driven AI & DG that had its good days and bad days lol

Still there is a reason flying pax IFR in the 135 world you NEED an autopilot or a second pilot.
If a working pilot walks out to the plane and the AP is found to not work, he legally ain’t flying IFR single pilot today.

Part 91 I would have been legal to load my entire family into that old plane I learned IFR in and launch into low IFR at night, l could even take off 0/0 with no nearby take off alternates, but it wouldn’t be prudent nor safe.

My skywagon has a very nice IFR panel in it, the old owner spent that $$ and never started on his instrument ticket, nothing wrong with that, his money his choice, and it worked out great for me. For him a GFC 500 would be fine as it would mostly be panel jewelry

That being said that GFC500 has a failure mode that doesn’t make it a serious autopilot choice if you’re going to be using it in the soup single pilot IMO

I’ve had GPS drop in the US a few times outside of any bombing range of anything like that, GPS failures and outages 100% do happen.

Most consumer stuff can also get its location off nearby wifi (google airhook) and other means, lots of military hardware has other means of navigation as jamming is in their own bag of tricks, larger jets have IRS systems, so it’s a lot different for GA compared to those examples


I would be surprised given the FAA/Feds history if they don’t start using and expanding stateside jamming much like we saw of TFRs after 9/11, I could be wrong

Personally if I was a baller building a new panel, I’d look at the other offerings when it comes to a AP, sometimes the slightly older model is better

What i run in to with this is the fact that a lot of the old analog systems are being 0hased out with many airports only offering gos approaches these days. Especially up in the great white north where it just doesn't pay to spend a pile fixing old equipment when its fairly cheap to just have a GPS approach made. In the event of a jamming, it doesn't matter what is in the panel, a LOT of airports are going to be unavailable. I don't plan on flying super hard IFR in my 206, as it's really not made for it. No FIKI and all that fun stuff. So I figure in the event of a failure I'll be able to get low enough on my AH to see and pick a place to land.

A1Skinner wrote:

NineThreeKilo wrote:

Mapleflt wrote:So your clear to fly an ILS approach, GPS coverage fails now what do you do ? How are you going to safely return to Mother Earth either at your planned destination or your filed alternate with a Garmin avionics suite ?

Going to have to hand fly it raw data from what Garmin says, not the end of the world, but a whole lot more task saturation for a failure that in other auto pilot systems is a”nothing burger”

DreadPirateWill wrote:I got my IFR ticket in a bird with twin G5s, a 430W and a king Nav/Com. No AP.
Maybe just me, but I'm having a hard time thinking it's really that big a deal for the rare occasion you're flying an ILS and GPS kicks out to just keep hand flying.
Our IFR bird now has a full Garmin suite including GFC500. It's been fantastic. Thus yet I've only flown it IFR between Washington state and Minnesota, but it's been pretty flawless.
I suppose if I was flying a 4 seat IFR leisure travel Cessna into an active warzone or trying to shoot ILS approaches into restricted bombing ranges I'd feel different. I just have a hard time believing that when most folks have GPS enabled smart phones, watches, etc and GPS is utilized by emergency responders from police, fire, and military that if GPS jamming genuinely affected them in a material way that there wouldn't be an appropriate response.

I got my ticket in a old nasty rental with two analog nav coms, two nav heads (only one had a glide slope), no GPS, no iPad, vac driven AI & DG that had its good days and bad days lol

Still there is a reason flying pax IFR in the 135 world you NEED an autopilot or a second pilot.
If a working pilot walks out to the plane and the AP is found to not work, he legally ain’t flying IFR single pilot today.

Part 91 I would have been legal to load my entire family into that old plane I learned IFR in and launch into low IFR at night, l could even take off 0/0 with no nearby take off alternates, but it wouldn’t be prudent nor safe.

My skywagon has a very nice IFR panel in it, the old owner spent that $$ and never started on his instrument ticket, nothing wrong with that, his money his choice, and it worked out great for me. For him a GFC 500 would be fine as it would mostly be panel jewelry

That being said that GFC500 has a failure mode that doesn’t make it a serious autopilot choice if you’re going to be using it in the soup single pilot IMO

I’ve had GPS drop in the US a few times outside of any bombing range of anything like that, GPS failures and outages 100% do happen.

Most consumer stuff can also get its location off nearby wifi (google airhook) and other means, lots of military hardware has other means of navigation as jamming is in their own bag of tricks, larger jets have IRS systems, so it’s a lot different for GA compared to those examples


I would be surprised given the FAA/Feds history if they don’t start using and expanding stateside jamming much like we saw of TFRs after 9/11, I could be wrong

Personally if I was a baller building a new panel, I’d look at the other offerings when it comes to a AP, sometimes the slightly older model is better

What i run in to with this is the fact that a lot of the old analog systems are being 0hased out with many airports only offering gos approaches these days. Especially up in the great white north where it just doesn't pay to spend a pile fixing old equipment when its fairly cheap to just have a GPS approach made. In the event of a jamming, it doesn't matter what is in the panel, a LOT of airports are going to be unavailable. I don't plan on flying super hard IFR in my 206, as it's really not made for it. No FIKI and all that fun stuff. So I figure in the event of a failure I'll be able to get low enough on my AH to see and pick a place to land.

In your situation I agree 100%

If all you got in your area of operations is GPS and no VOR/ILSs, having a loss of GPS remove your APs ability to use VOR/ILS, it wouldn’t really make a difference for you



THEORETICALLY

One could make some home brew approaches with a ADF and local AM radio stations, or with dual you could get a pretty good 2D position



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