Practicality of single radio IFR

[MarkH]

Discussing with a friend about ADS-B options, we started talking about the GNX 375 for a Cessna 150 with the original KX-170 Nav/Com and an AT-50 transponder.

Since neither of us is Instrument rated (I am planning on pursuing it soon), we have no first-hand experience to say how much the single comm setup will add to the pilot workload. In that situation, I would definitely carry a handheld in case of failure, but that does not do much good outside of emergencies.

How much would a single comm radio add to the pilot workload in a single pilot IFR scenario? Would you be willing to take that on an IFR flight plan often enough to justify the extra $4k of a GNC375 over a GTX-345 transponder?

 

[Greg Bockelman]

You give up an awful lot of redundancy with just one nav and one com. That’s fine for occasional light IFR, but if I were to do a lot of it, I would want a second nav source at least.

 

[MarkH]

You give up an awful lot of redundancy with just one nav and one com. That’s fine for occasional light IFR, but if I were to do a lot of it, I would want a second nav source at least.

With the GNX, you will have 2 Navs, GPS and VHF Nav (in the KX-170). But you will not have a secondary comm for monitoring a secondary frequency enroute or even a flip-flop function to quickly change back and forth.

 

[MauleSkinner]

Discussing with a friend about ADS-B options, we started talking about the GNX 375 for a Cessna 150 with the original KX-170 Nav/Com and an AT-50 transponder.

Since neither of us is Instrument rated (I am planning on pursuing it soon), we have no first-hand experience to say how much the single comm setup will add to the pilot workload. In that situation, I would definitely carry a handheld in case of failure, but that does not do much good outside of emergencies.

How much would a single comm radio add to the pilot workload in a single pilot IFR scenario? Would you be willing to take that on an IFR flight plan often enough to justify the extra $4k of a GNC375 over a GTX-345 transponder?

With a single comm, I always wrote frequencies down. With two comms I never did that. That’s the workload difference for me.

It’s the redundancy level that most people determine to be a need for more than one comm (or NAV).

 

[geezer]

Addressing just one element of the question, the KX 170 does not have flip flop frequency selection, which make later radios work almost as well as 2 radios. That allows setting up the next frequency at a convenient time, in advance, or if just assigned an unexpected new freq, the ability to come back to the original quickly if the new one does not work.

I believe that an "old technology" radio that can be tuned in bad turbulence is a necessity, as the knobs serve as an anchor while turning to the new frequency. The all in one magic boxes assume that you will always hit the right button, or spot on the screen. Fine on the ground or in smooth air. Other members here have agreed with this, relative to bumpy air.

A good used radio with glide slope should be easy to find in the present environment of everyone going all glass. It also serves as a backup that does not use the same input as a GPS does, so a safer redundancy.

 

[Sinistar]

With the GNX, you will have 2 Navs, GPS and VHF Nav (in the KX-170). But you will not have a secondary comm for monitoring a secondary frequency enroute or even a flip-flop function to quickly change back and forth.

Could you clarify how he would have 2 NAV's in this setup. He would have a VHF nav in the KX-170 but it was my understanding that the GNX375 is only GPS and no NAV or COM radio receiving capability. I think that low profile box is filled to the brim with transponder and GPS and no room for radio stuff.

 

[MauleSkinner]

Could you clarify how we would have 2 NAV's in this setup. He would have a VHF nav in the KX-170 but it was mu understanding that the GNX375 is only GPS and no NAV or COM radio receiving capability. I think that low profile box is filled to the brim with transponder and GPS and no room for radio stuff.

How about “2 NAVs—GPS, and VHF in the KX170.”

Just like “Let’s eat Grandma,” punctuation is your friend.

 

[MarkH]

Could you clarify how we would have 2 NAV's in this setup. He would have a VHF nav in the KX-170 but it was mu understanding that the GNX375 is only GPS and no NAV or COM radio receiving capability. I think that low profile box is filled to the brim with transponder and GPS and no room for radio stuff.

By 2 Navs, I mean 2 navigation sources, not 2 Nav radios. You would have a single radio Nav source, but the GPS would still be available if the Nav failed. (Keeping in mind, I have not started my IFR training) I would think that would be enough since I have heard some pilots argue that with the decommissioning of many radio nav approaches, they would consider ditching the radio Nav altogether.

 

[Sinistar]

No worries. Our GTX345 installer had told me the GNX175 had room in the case for one other goodie which turned out to be a COM and became the GNC355. Had the GNX375 also had a radio for COM/NAV, at its price Garmin would never be able to make enough so I was wanting to be sure I didn't miss something regarding the GNX375. We decided to go the GTX345 and will do the GNC355a on the next update to get one integrated radio.

 

[Greg Bockelman]

With the GNX, you will have 2 Navs, GPS and VHF Nav (in the KX-170). But you will not have a secondary comm for monitoring a secondary frequency enroute or even a flip-flop function to quickly change back and forth.

Ok. I misinterpreted that.

 

[Jim Carpenter]

To bring up a side-issue, if your radio is really a KX 170, rather than a KX 170B, I don't think it's even allowed to be used for transmitting, due to the "width" of frequency overlap in the old 360 channel units.

Edit: Evidently, KX170 could be modified to meet the tighter frequency tolerances, but would still be limited to 360 channels, meaning it would not be able to tune any xxx.x25 or xxx.x75 channels, not very practical for IFR comms.

 

[MarkH]

To bring up a side-issue, if your radio is really a KX 170, rather than a KX 170B, I don't think it's even allowed to be used for transmitting, due to the "width" of frequency overlap in the old 360 channel units.

I didn't realize that, but in this case, it's a KX-170B. I just remembered it as the click wheel style and I found a picture that looked like it on the internet.

 

[Jim Carpenter]

I didn't realize that, but in this case, it's a KX-170B. I just remembered it as the click wheel style and I found a picture that looked like it on the internet.

Aha, good to go, then, with consideration to everyone else's comments.

 

[PPC1052]

With only one COM, you will have to leave the ATC frequency to check the ATIS, ASOS, ect. to get weather and information about the destination airport. That adds to the stress level because you can't listen for an ATC instruction while you do so. You will have to ask permission to temporarily leave the frequency to get the weather.

 

[James331]

A single com is as practical as a c150 is for IFR

 

[SbestCFII]

With the GNX, you will have 2 Navs, GPS and VHF Nav (in the KX-170). But you will not have a secondary comm for monitoring a secondary frequency enroute or even a flip-flop function to quickly change back and forth.

Replace the KX170 with a MX-170C unit (you'll get the digital flip-flop function at least) or you can just add an MX-170C and have two NacCom radios, plus the GNX-175 and your transponder. Add a skybeacon and you've got ADS-B out. GDL/Stratus for ABS-B In.

 

[DesertNomad]

With a single comm, I always wrote frequencies down. With two comms I never did that. That’s the workload difference for me.

It’s the redundancy level that most people determine to be a need for more than one comm (or NAV).

So when you get a new frequency, do you enter it in both radios?

 

[455 Bravo Uniform]

I believe that an "old technology" radio that can be tuned in bad turbulence is a necessity, as the knobs serve as an anchor while turning to the new frequency. The all in one magic boxes assume that you will always hit the right button, or spot on the screen. Fine on the ground or in smooth air. Other members here have agreed with this, relative to bumpy air.

This is correct for the newer Garmins such as the 650 & 750. This is NOT correct for the similar Avidyne IFD-440 & -540. The Avidynes are fully touch screen functional WITH redundant push buttons to accomplish the same task without having to touch the screen if you don’t want to or can’t. Plus it reduces fingerprints, lol.

 

[brcase]

I think the 345 is a great option for you. You are going to be doing very little if any actual IFR in a C-150 in most locations. But it will let you get your Instrument Ratings for inexpensive. A Non-Flip Flop radio is not nearly as nice as a flip-flop or dual radios, but certainly acceptable for Instrument training.

I did my CFII in a Piper Tomahawk with a KX-170B and a DME.

Brian
CFIIG/ASEL

 

[MauleSkinner]

So when you get a new frequency, do you enter it in both radios?

No, I alternate radios for each new frequency (assuming they’re not flip/flop radios).

 

[MuseChaser]

No, I alternate radios for each new frequency (assuming they’re not flip/flop radios).

I don't currently have two radios, so I'm just asking... is that a common way to use two radios? My thinking was that one would be used for ATC communications, and the other one for ATIS, FSS, or monitoring guard or CTAF frequencies so you could do those things w/out missing ATC communications..... and as a redundant backup, too, of course. Thoughts?

 

[MarkH]

I don't currently have two radios, so I'm just asking... is that a common way to use two radios? My thinking was that one would be used for ATC communications, and the other one for ATIS, FSS, or monitoring guard or CTAF frequencies so you could do those things w/out missing ATC communications..... and as a redundant backup, too, of course. Thoughts?

That is how I have used dual radios in my club trainers.

 

[MauleSkinner]

I don't currently have two radios, so I'm just asking... is that a common way to use two radios? My thinking was that one would be used for ATC communications, and the other one for ATIS, FSS, or monitoring guard so you could do those things w/out missing ATC communications..... and as a redundant backup, too, of course. Thoughts?

It’s all technique, not procedure.

 

[mcmanigle]

I don't currently have two radios, so I'm just asking... is that a common way to use two radios? My thinking was that one would be used for ATC communications, and the other one for ATIS, FSS, or monitoring guard or CTAF frequencies so you could do those things w/out missing ATC communications..... and as a redundant backup, too, of course. Thoughts?

I've heard all kinds of different schemes. For me personally it's com1 for ATC air (tower, app/dep, center, etc) and com2 for weather (ATIS, ASOS, FSS) and ATC ground (incl clearance). I suspect that whatever dual-radio strategies people have, they will have in common that ATC air and weather are on different radios for obvious reasons. I like to have tower and ground on different radios so that I don't have to worry about exactly when they want me to switch over.

I'll also use com2 for monitoring local airport CTAF while in cruise with ATC on com1 if I'm low enough to care, or to monitor guard if not doing anything else.

 

[lancie00]

I don't currently have two radios, so I'm just asking... is that a common way to use two radios? My thinking was that one would be used for ATC communications, and the other one for ATIS, FSS, or monitoring guard or CTAF frequencies so you could do those things w/out missing ATC communications..... and as a redundant backup, too, of course. Thoughts?

That's how I do it. One radio for ATC/tower/ground and one radio for ATIS/AWOS/guard, etc... I think a single radio for IFR would be doable, but tough. Especially one without flip-flop.

 

[TheGolfPilot]

The comm two on one of my planes works maybe 10% of the time. Unit gets replaced this week. I flew almost a whole year with it like that. I fly single pilot IFR often in it and it just became habit. I have been picking up atis between handoffs on comm1. I have been using the comm2 to "save" frequencies. But you could just use a piece of paper for that. Once you get the flow, one radio isn't a big deal. Unless that last radio fails...

 

[N1120A]

I don't find VFR practical with 1 radio, let alone IFR. Leaving frequency in IFR is absolutely insane, particularly as you are getting ATIS/AWOS/ASOS as you transition from en route to terminal, or within the terminal environment. Now, maybe if the radio has a monitor function, you can get away with it, but to do this where you have to leave frequency - forget about it.

This is correct for the newer Garmins such as the 650 & 750. This is NOT correct for the similar Avidyne IFD-440 & -540. The Avidynes are fully touch screen functional WITH redundant push buttons to accomplish the same task without having to touch the screen if you don’t want to or can’t. Plus it reduces fingerprints, lol.

Actually, this is NOT true for comms. The GTN650/750 comm functions can be fully executed with a knob.

 

[unsafervguy]

No, I alternate radios for each new frequency (assuming they’re not flip/flop radios).

This is a very good technique for non flip flop radios. That way if you mess up the new freq you still have the old freq in the other radio.

 

[Martin Pauly]

This is NOT correct for the similar Avidyne IFD-440 & -540. The Avidynes are fully touch screen functional WITH redundant push buttons to accomplish the same task without having to touch the screen if you don’t want to or can’t. Plus it reduces fingerprints, lol.

Speaking of Avidyne IFDs, they have a second VHF receiver so you can, with one unit, stay on your assigned frequency and listen to ATIS etc. at the same time - which covers 99% of what I use my second radio for. I would be comfortable flying IFR that way - after all, these modern radios are pretty reliable; it's rare to hear of in-flight failures.

- Martin

 

[N1120A]

The GTNs allow for monitoring on one radio as well. When my 430W had its screen go bad, I did this for a while.