IFR avionics panel planning - need for VOR /LOC/GS?

[AJ88V]

 I'm a VFR pilot just starting my IFR training, so I'm pretty ignorant and welcoming of advice.

My current panel has a pair of King radios and indicators, one just VOR and a the other VOR/GS.  I haven't really used them since I bought my first handheld GPS, although I always would tune in VORs as habit on long cross countries just for situational awareness, habit, and ready backup in case the GPS failed.

I'm looking at replacing the entire panel with Dynon HDX glass and a Garmin GNC 355 or GPS 175.  This leaves the plane without a VOR/GS receiver.  Dynon's VHF radio is comms only.  I could put in a GNC 215 as the second radio instead to get the VOR/GS, but is it  even needed anymore?  

What am I realistically giving up by not having VOR/GS? I don't think most of the smaller airfields I'd be using would even have it.  

And if I went for a VOR/GS like the GNC 215, what's the utility of having only one, or do I really need two of them?

I appreciate your input. Thanks!

 

[hammdo]

I like options, still I train with VOR, ILS, and do 30 day VOR checks. MON networks are around so ILS is the way to get in when GPS is out - and that does happen. One will keep you busy, 2 would be nice but not a necessity.

G5s, GNC355, KX 155/ GS/LOC with independent indicator…

-Don

[kortopates]

The Dynon HDX supports multiple navigation sources beyond just GPS. It integrates with VOR, ILS, and other traditional navigation systems. You just need to include a GPS with NAV/COM or another NAV/COM radio. You won't need the display heads.

Although its legal to fly IFR only with GPS, i personally things its nuts! The GPS signal is very weak and easily jammed. I may laugh at losing GPS signal from someone jamming while VFR but when it happens in IMC its a very serious matter, No way am I launching without it. Only my opinion but it seems careless and reckless to place such confidence in GPS always being there for you.  

[Paul Thomas]

I've had a GPS failure. It was VFR and dead reckoning got me home.

If you're planning on flying IFR places, I wouldn't build a GPS only panel. I would only do 1nav; there is no need for 2 when you'll be on GPS 99% of the time.

[Utah20Gflyer]

I have a Garmin 355 and 255.  That gives me two coms , waas gps, VOR and GS.  Everything I need and nothing extra.   Because GPS can go down I want ground based legacy nav for redundancy.  I tend to just use the GPS and have never actually needed the legacy stuff but I like it for training and there are still a lot of approaches that require it.   You are going to really limit your training with no nav radio.   

[midlifeflyer]

I think there’s a little “where and how do you expect to fly IFR?” in the answer to your question. Already mentioned is the potential need for an ILS in case of a GPS failure.  Same for VOR enroute capability (I don’t put VOR or LOC approaches in the same category since too many of the remaining ones in many areas also require DME.)

A third reason to retain VOR capability is, there are some tasks that are simply easier and more efficient with VOR than with GPS. I’ve seen pilots screw up things as simple as intercepting a radial inbound (outbound is more difficult). One would hope that a GPS only pilot will have learned how to do them, but instrument training, with its emphasis on local approach procedures, tends to be deficient in that area. 

If none of those reasons apply to you, I don’t see a problem with having only GPS IFR navigation capability. 

[McMooney]

14 hours ago, AJ88V said:

 I'm a VFR pilot just starting my IFR training, so I'm pretty ignorant and welcoming of advice.

My current panel has a pair of King radios and indicators, one just VOR and a the other VOR/GS.  I haven't really used them since I bought my first handheld GPS, although I always would tune in VORs as habit on long cross countries just for situational awareness, habit, and ready backup in case the GPS failed.

I'm looking at replacing the entire panel with Dynon HDX glass and a Garmin GNC 355 or GPS 175.  This leaves the plane without a VOR/GS receiver.  Dynon's VHF radio is comms only.  I could put in a GNC 215 as the second radio instead to get the VOR/GS, but is it  even needed anymore?  

What am I realistically giving up by not having VOR/GS? I don't think most of the smaller airfields I'd be using would even have it.  

And if I went for a VOR/GS like the GNC 215, what's the utility of having only one, or do I really need two of them?

I appreciate your input. Thanks!

 

Just keep the king radio and cdi with vor/gs.  No changes necc.

or if you really want it integrated, swap the 355 for a 650xi,  which will approx cost the same as a 355 + 215

 

[Vance Harral]

I think one thing poorly understood in these debates is how likely your airplane is to lose GPS signal, vs. availability of the GPS network overall.

The reliability of GPS as a system is very good, legitimate stories about jamming and spoofing not withstanding.  There are many redundant satellites, the receivers have excellent discrimination, and overall hardware and software availability is very reliable.  Widespread outages are essentially unheard of - any such thing would immediately make national news as shipping deliveries were disrupted, Uber drivers didn't arrive, etc.  Because of this, there's an understandable tendency to think a GPS-nav-only airplane isn't a big deal.

But GPS nav failure in an individual airplane is a different analysis.  Antennas and cabling break, faulty COM radios generate harmonics that disrupt GPS receivers, etc.  You also get the occasional, rogue interference in a small local area (sometimes near your airport) from some moron trying to disrupt tracking by his employer or parole officer, or whatever.  I won't say these sorts of problems are frequent, but they're not unheard of.  Most of us that have used panel-mounted GPS in a variety of airplanes for many years have seen an incident or two.  When it happens, you can ask ATC or the CTAF or whoever, "Hey, what's going on with GPS?", but all you get is the verbal equivalent of a shoulder shrug, and reports that it's working for others.  That's a pretty lonely feeling in VMC, can't imagine what it would feel like in IMC.

[DCarlton]

I addition to GPS, I have dual VOR/GS/LOC capability and wouldn't want to be without at least one of them on a separate radio from my GPS NAV system (and I prefer two).  I tune them both in, cross check them, and use ILS approaches often.  

[kortopates]

I think there’s a little “where and how do you expect to fly IFR?” in the answer to your question. Already mentioned is the potential need for an ILS in case of a GPS failure.  Same for VOR enroute capability (I don’t put VOR or LOC approaches in the same category since too many of the remaining ones in many areas also require DME.)
A third reason to retain VOR capability is, there are some tasks that are simply easier and more efficient with VOR than with GPS. I’ve seen pilots screw up things as simple as intercepting a radial inbound (outbound is more difficult). One would hope that a GPS only pilot will have learned how to do them, but instrument training, with its emphasis on local approach procedures, tends to be deficient in that area. 
If none of those reasons apply to you, I don’t see a problem with having only GPS IFR navigation capability. 

I teach GPS manual holding with the OBS (and arcing) that of course works with any IFR GPS to ensure they can use OBS. But without that, most don’t have a clue how to intercept GPS radials.


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[kortopates]

I addition to GPS, I have dual VOR/GS/LOC capability and wouldn't want to be without at least one of them on a separate radio from my GPS NAV system (and I prefer two).  I tune them both in, cross check them, and use ILS approaches often.  

To be fair, the ILS is your only precision approach capability with a non-waas GPS. If you had WAAS, GPS LPV might be preferred and it’s LOC or GS never go out of service.


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[AJ88V]

9 hours ago, McMooney said:

Just keep the king radio and cdi with vor/gs.  No changes necc.

or if you really want it integrated, swap the 355 for a 650xi,  which will approx cost the same as a 355 + 215

 

I was actually thinking of doing exactly that (keeping one Kx155 and CDI).  But you also make a good point that about the cost of the GNC 215 + GNC 355 being almost the same as a GTN 650xi.  In fact, the 650 is only about $1K more with the current rebate, plus that would be simpler to install and it's a much more desirable unit.

[dkkim73]

You asked for opinion, so here it is;

- since you're training, learn to fly VOR nav and approaches, and get proficient at visualizing radial and aircraft position via the CDI (there is a great mental approach in the "Instrument Flying Manual" by Peter Dogan, which I think a fair number of instructors use), learn the 5-6 T's and flying a 6-pack IFR, dual-VOR position finding, arcs, etc, etc.

Provides 1. the familiarity Paul mentions 2. ability to jump in and fly a wider range of aircraft 3. good mental muscle development... This helps keep from just following the magenta line. You can do that later when you want. 

- keep ILS and VOR capability

GPS is great but it's much more complicated tech vs. the simple RF in the VOR/LOC. It's a fabulous technology but just inherently more susceptible to interference, etc. Sure, it mostly just works. But why just have one fancy thing instead of robustness through diverse tech? 

Two is one and one is none. 

You asked. I'm sure someone will be along to say "just use GPS and an iPad" and throw shade on my desire for a DME and ADF ...

 

[Will.iam]

48 minutes ago, AJ88V said:

I was actually thinking of doing exactly that (keeping one Kx155 and CDI).  But you also make a good point that about the cost of the GNC 215 + GNC 355 being almost the same as a GTN 650xi.  In fact, the 650 is only about $1K more with the current rebate, plus that would be simpler to install and it's a much more desirable unit.

Or if you are going dynon anyway the avidyne 540 would be a great unit as well and a drop in replacement if you have a garmin 530. 

[Skates97]

I'm one of those that has GPS only in the panel. I have a GNC355 and a SL-40 (comm only) as my #2 radio. I'm not saying it can't happen, but in five years and about 600 hours I haven't had a GPS failure. As Mark mentioned above intercepting radials is more difficult (especially the outbound) but it is doable with some practice. In my IFR training we may have covered it, I can't remember, but I learned it all over again after I got my ticket and know the buttonology to do radials if necessary.

My homebase is always advertising the VOR so I request the RNAV. Only once did I get pushback from ATC and I told them I was GPS only and needed the RNAV unless they could vector me and get me below the layer. They said they needed to vector me around a bit but would put me on the RNAV and did. The vectors added maybe 10 minutes to my flight.

When I was doing my IFR training the way the ACS was written I couldn't take the check ride in my plane.  In one of the appendixes for the Non-Precision Approach it said:

"Task A. Nonprecision Approach
The evaluator will select nonprecision approaches representative of the type that the applicant is likely to use. The choices must use at least two different types of navigational aids."

The interpretation was that GPS is one type so you needed a ground based option as well. They have since updated the appendix removing the "two different types" which now reads:

"Task A. Non-precision Approach
A non-precision approach is a standard instrument approach procedure to a published minimum descent altitude without approved vertical guidance. The applicant may use navigation systems that display advisory vertical guidance during nonprecision approach operations, if available.

The evaluator must select and the applicant must accomplish at least two different non-precision approaches in simulated or actual instrument meteorological conditions:"

[DCarlton]

12 hours ago, kortopates said:

I teach GPS manual holding with the OBS (and arcing) that of course works with any IFR GPS to ensure they can use OBS. But without that, most don’t have a clue how to intercept GPS radials.


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PHX approach often assigns you outbound radials from the BKY VOR.  I remember figuring out how to do that on the GNS the first time.  It was nice! 

[midlifeflyer]

12 hours ago, kortopates said:

I teach GPS manual holding with the OBS (and arcing) that of course works with any IFR GPS to ensure they can use OBS. But without that, most don’t have a clue how to intercept GPS radials.

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I’d be careful of that broad statement. The manual hold in OBS mode wont work with Avidyne units.  Interceptions, yes, but manual holds, no. Avidyne OBS mode does not suspend automatic sequencing.  

[Pinecone]

20 hours ago, DCarlton said:

I addition to GPS, I have dual VOR/GS/LOC capability and wouldn't want to be without at least one of them on a separate radio from my GPS NAV system (and I prefer two).  I tune them both in, cross check them, and use ILS approaches often.  

Same here.

Having two makes the 30 day VOR check easy.  I do it every longer XC flight.  Tune in the same VOR on both, put one on needle 1 and one on 2, and they match bearings, I write it on my kneeboard.

[AJ88V]

On 5/7/2025 at 8:17 AM, McMooney said:

Just keep the king radio and cdi with vor/gs.  No changes necc.

or if you really want it integrated, swap the 355 for a 650xi,  which will approx cost the same as a 355 + 215

 

I was actually thinking of doing exactly that (keeping one Kx155 and CDI).  But you also make a good point that about the cost of the GNC 215 + GNC 355 being almost the same as a GTN 650xi.  In fact, the 650 is only about $1K more with the current rebate, plus that would be simpler to install and it's a much more desirable unit.

Really appreciate the discussion above.  As a VFR pilot, a lot of it is going over my head, but some is sinking in.  

Also thinking of keeping the steam gauges.  I was pretty good on aircraft control under the hood when I tried getting my IFR cert 15 years ago.  Not sure there will be room for the old gauges in the Mooney panel, or if that will drive the cost unnecessarily.  How hard was it for you to transition to a glass panel with tapes instead of dials?

[Andy95W]

You can have the best of both worlds with G5s.

 

[Skates97]

11 hours ago, DCarlton said:

PHX approach often assigns you outbound radials from the BKY VOR.  I remember figuring out how to do that on the GNS the first time.  It was nice! 

Yes, they like that. The first time I asked for a heading (which they gave to me) not knowing or remembering that function from my IFR training. I wrote about it in an article and Don Kaye was kind enough to email me and fill me in on what I was missing. I spent some time with the simulator on the computer and figured it out. The next time they assigned me an outbound radial I pushed all the right buttons and tracked it out.