Would you give up ILS for LPV approaches?

Chip Sylverne

Chip Sylverne

Final Approach
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Quit with the negative waves, man.
I am preparing to be disappointed in the Garmin 175. Looking over the IM, it looks like it will support my HSI and A/P, but won't share it with my SL30. There are a couple dedicated pins missing on the J connector to support the ACU, like OBS HOLD/Susp, term, wpt. The only two outputs are LOI and APPCH. No interconnect diagram either. Not a good sign, I think.

So that leaves the question. If the 175 won't support sharing an HSI, would it be worth the trade off, LPV for ILS?
 
I've got the SL30 using a TKM MC60 CDI - works perfectly. Called Garmin last week to find out if the 175 will talk to the MC60 - they're not sure and are researching it. Because, I've got a second MC60 CDI on the shelf that would be the display for LPV with the 175.

Looking at the docs, the 175 is an ADS-B out....I'm assuming it can be turned off, since I have the GTX 335.
 
I would. The only thing the ILS beats the LPV at is CatII/III ops (for now and small GA can’t do it anyways).

Stand by for the “you’ll be sorry when the Russians shoot down our satellites” comments. :)
 
Radar Contact said:
I would. The only thing the ILS beats the LPV at is CatII/III ops (for now and small GA can’t do it anyways).

Stand by for the “you’ll be sorry when the Russians shoot down our satellites” comments. :)
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I'll be first. Reminds me I haven't seen Gravity in a while.
 
Cost to maintain ILS: ~$100,000
Cost to maintain LPV: ~$3,000

I'd give up ILS for LPV.

That said, I'd fight pretty hard to have both.
 
Right now, today? Only if the price for those fancy IFR WAAS GPS boxes comes WAY, WAY down!
 
murphey said:
I've got the SL30 using a TKM MC60 CDI - works perfectly. Called Garmin last week to find out if the 175 will talk to the MC60 - they're not sure and are researching it. Because, I've got a second MC60 CDI on the shelf that would be the display for LPV with the 175.

Looking at the docs, the 175 is an ADS-B out....I'm assuming it can be turned off, since I have the GTX 335.
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175 doesn’t have ADSB , does it?
 
With space wars starting to happen (
), I like the idea of having a string hanging off the earth to grab ahold of to lead me home.

I wish we could have both; I get the costs thing.
 
Oh! It’s a position source meaning it can feed WAAS to a transponder jnstead of installingaWAAS antenna solely for thetransponder.
 
Chip Sylverne said:
I am preparing to be disappointed in the Garmin 175. Looking over the IM, it looks like it will support my HSI and A/P, but won't share it with my SL30.
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This doesn't make sense. What nav radio would provide the autopilot switching you're talking about? That's either going to be provided in the autopilot control head, the HSI system, or some other means.

https://www.aircraftspruce.com/catalog/avpages/ais200a-35.php?clickkey=3875829

https://www.aircraftspruce.com/catalog/avpages/remoteswitchrelay.php?recfer=14036
 
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bnt83 said:
This doesn't make sense. What nav radio would provide the autopilot switching you're talking about? That's either going to be provided in the autopilot control head, the HSI system, or some other means.

https://www.aircraftspruce.com/catalog/avpages/ais200a-35.php?clickkey=3875829

https://www.aircraftspruce.com/catalog/avpages/remoteswitchrelay.php?recfer=14036
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In order to use those relays, you need to have an external control unit, or ACU. The pilot uses the to ACU select the nav source to the HSI, either by selecting Nav for vor/ILS, or GPS. The ACU (Mid Continent MD 151x for Garmin touch scrern navigators) requires certain outputs from the gps to correctly operate and annunciate for ifr ops. Among them is obs/suspend, wpt, term...and it looks from the 175 pinout those discrete outputs are missing.

I need to call Garmin and see what the deal is. I hope I'm mistaken, because if this is being marketed as a replacement for the GX, most of those swap between the gps and nav via the apollo acu, because WAAS was just a gleam in an engineers eye at the time they wee installed.
 
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Chip Sylverne said:
I am preparing to be disappointed in the Garmin 175. Looking over the IM, it looks like it will support my HSI and A/P, but won't share it with my SL30. There are a couple dedicated pins missing on the J connector to support the ACU, like OBS HOLD/Susp, term, wpt. The only two outputs are LOI and APPCH. No interconnect diagram either. Not a good sign, I think.

So that leaves the question. If the 175 won't support sharing an HSI, would it be worth the trade off, LPV for ILS?
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I would favor the LPV over ILS. Because LPV is not a ground installation, all approaches look pretty much the same. ILS can have some variations, such as DME required, radar required, or some other oddities. Not a big deal if you fly all the time, however, but for the occasional IFR flyer, LPV is much more standardized.
 
Having either is fine. I'd give up ILS if the initial savings for maintain ILS went to making more LPV approaches at other airports.

I like having one or the other though, as sometimes the ceiling is below standard RNAV limits.
 
I won’t be giving up my glideslope any time soon. It is on a separate circuit and provides redundancy. You never know.
 
I prefer to use an LPV approach over an ILS approach. The LPV approaches tend to be more stable and less susceptible to issues like prop shadowing (the 310 was very bad about this). Plus LPVs are more available at a larger number of airports than ILSs are. Pretty much all airports with an ILS also have an LPV to equal minimums, but many airports with LPVs do NOT have an ILS.

That said, I would not want to give up ILS for the simple reason that at busier airports you will often be assigned an ILS, and in some cases if you ask for the LPV you will be told "No." So then that puts you in the position of having to say "Unable" and wondering what NY approach will do with you, or else shooting the LPV approach to the same one (assuming there is one) and hoping you don't get in trouble for it. I don't like that position.
 
false dichotomy. get a second cdi and retain your legacy localizer capability. im not even all that concerned about precision minimums, im just saying vor/loc approach guidance capability is so cheap these days, it truly is worth the second cdi imo.
 
hindsight2020 said:
false dichotomy. get a second cdi and retain your legacy localizer capability. im not even all that concerned about precision minimums, im just saying vor/loc approach guidance capability is so cheap these days, it truly is worth the second cdi imo.
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Exactly!
 
Having just retaken the IR written, if you file for an LPV approach, and you require an alternate, the alternate (assuming less than VMC from MEA to runway) must be a different approach type, (ILS or LOC) correct? That alone would be enough reason to me.
 
Walboy said:
If you file for LPV that implies you have a WAAS GPS in which case you can plan for RNAV at both destination and alternate.
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I know there were questions on this topic on the written where (assuming you needed to file an alternate and the alternate was not forecast to be VMC) the alternate had to have another approach type. When you actually get there, you fly what you can. But to file, it had to be some other type than RNAV. I'll see if I can find the question(s) later.
 
Walboy said:
That is true for a non-WAAS GPS.

Specifically...it's TSO-C129 and TSO-C196 versus TSO-C145 or TSO-C146. AIM 1-1-17 a.5.c and d
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Ah! Didn’t catch the non-WAAS part.
 
I got bored and read this part of the AIM yesterday, and it speaks of the Minimum Operational Network that will still be in place as a backup in case that Satellite-Based navigation is unavailable. The plan is that you'll always have a ground-based approach capability within 100Nm no matter where you are in the system. So, it would be nice to have some sort of back up still installed in your aircraft so that you'd have that option if it ever happened. Of course, your fuel planning might need to be altered if you actually had to fly that far to find a ground-based instrument approach, but...
 
Interesting discussion that might affect my avionics choices down the road.... are there situations where there is ILS but no RNAV to the same runway? Most airports I have flown to have 1 or 2 ILS and rest are RNAV, wondering if there are a lot out there the other way around...
 
wilkersk said:
Right now, today? Only if the price for those fancy IFR WAAS GPS boxes comes WAY, WAY down!
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$5000 is way, way down. Shooting the ILS at the home base today and the localizer was OOS, GS working fine...working fine yesterday. As long as the satellites are operational, the box works just fine all the way to DA, usually the same or at least close to ILS minimums. Besides, if you're buying a 175 to replace your KLN unit, you'll still have your NavCom/GS since BK never had an integrated unit anyway. BK abandoned all of us in GA almost 2 decades ago. They won't even support their radios anymore. Honeywell makes more dollars on vacuum cleaners than GA avionics.
 
SbestCFII said:
$5000 is way, way down. Shooting the ILS at the home base today and the localizer was OOS, GS working fine...working fine yesterday. As long as the satellites are operational, the box works just fine all the way to DA, usually the same or at least close to ILS minimums. Besides, if you're buying a 175 to replace your KLN unit, you'll still have your NavCom/GS since BK never had an integrated unit anyway. BK abandoned all of us in GA almost 2 decades ago. They won't even support their radios anymore. Honeywell makes more dollars on vacuum cleaners than GA avionics.
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"A bird in the hand..." and all that. RE the OP's situation, and given only the info he provided, I still say 'right now, today: No!' Ask me again in a couple of years.
 
If I had to choose, yes I would take LPV over ILS.

I think for the sake of redundancy I would prefer to have *a* way of shooting both on the plane, but it wouldn't have to be the same indicator. If you can use a "steam" indicator like the GI 106A for the ILS and a G5 for the LPV, that's what I would do in your shoes.
 
LPV will get you into more places than ILS. I'm keeping both for now, though. Practically speaking, you always get assigned the ILS at major terminals, unless it's out of service.
 
I'm building a plane and the possibility of having a GNX 375 and two GTR 20 comm radios (total $10,000) vs. a GTN 650, a GTR 20, and a GTX 45R (total $14,500) is something I have been thinking about a lot. Of the airports I have ever flown into, only two have an ILS with lower minimums (200) than the same-runway LPV (250 in both cases). I have never had to fly an ILS in the real world. I was assigned a back-course localizer approach once and asked for the LPV to the same runway instead and got it. Being able to honestly say "unable" when offered a back-course might be reason enough to ditch the nav radio.

I would be comfortable going without ILS most of the time. The only exceptions I can foresee are (1) if the GPS signal is unreliable or (2) if you are @Ted DuPuis and get into a stare-down with NY Approach (post #17). The latter doesn't scare me because the worst-case is that I have to divert to a more friendly airport. The former does scare me a little, because the worst-case is that I am in or above clouds and cannot get vectors to VMC before running out of fuel.
 
iamtheari said:
I would be comfortable going without ILS most of the time. The only exceptions I can foresee are (1) if the GPS signal is unreliable or (2) if you are @Ted DuPuis and get into a stare-down with NY Approach (post #17). The latter doesn't scare me because the worst-case is that I have to divert to a more friendly airport. The former does scare me a little, because the worst-case is that I am in or above clouds and cannot get vectors to VMC before running out of fuel.
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There's what's scary and then there's also getting the job done. Remember my flying is much more mission-oriented and so if I can't get into an airport, that really screws up things for a lot of people (and dogs). So, I want as many tools at my disposal as possible, and I also want to make sure I can't say "unable" because I lack a piece of equipment I knew I was likely going to need at some point.
 
Ted DuPuis said:
There's what's scary and then there's also getting the job done. Remember my flying is much more mission-oriented and so if I can't get into an airport, that really screws up things for a lot of people (and dogs). So, I want as many tools at my disposal as possible, and I also want to make sure I can't say "unable" because I lack a piece of equipment I knew I was likely going to need at some point.
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While one could conceivably put a GPS 175 or a GNX 375 into a plane like an MU-2, it seems unlikely to become common to do so. The people whose business travel is in a Cirrus or a Seneca already accept greater limitations on completing their missions than being GPS-only would impose. Your story about ATC not authorizing approaches other than the ILS is a concern for some, including you, because of your mission. But for most of the target market of Garmin's GPS-only navigators, we have to weigh the price of the ILS equipment against a much smaller convenience factor.
 
iamtheari said:
While one could conceivably put a GPS 175 or a GNX 375 into a plane like an MU-2, it seems unlikely to become common to do so.
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The GPS 175 and GNX 375 are not approved for Class 3 aircraft, so putting one in would probably not actually be feasible.

The people whose business travel is in a Cirrus or a Seneca already accept greater limitations on completing their missions than being GPS-only would impose. Your story about ATC not authorizing approaches other than the ILS is a concern for some, including you, because of your mission. But for most of the target market of Garmin's GPS-only navigators, we have to weigh the price of the ILS equipment against a much smaller convenience factor.
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As with anything it depends on what and where you fly. Because RNAV approaches have become increasingly common it's gotten to the point where if you file /A or /U you're really hurting yourself in the terminal area. Using NYC as an example, going into MMU last year in the MU-2 they were only allowing aircraft to do the RNAV to whatever runway it was, so if I didn't have the ability to shoot an RNAV approach I couldn't have gotten in there. The day was not a bad enough day that a PA28 shouldn't have been flying, unless you don't like low IFR in a piston single. Still, the fact that I'm LNAV only and not LPV was an issue, as I just barely made it in (right at minimums, didn't see the runway until just before the MAP).

If you only fly around the great flatlands, the land of D-> "Cleared as filed" and where every airport has an LPV approach, then I think losing ILS wouldn't be too big of a deal. But I do think if you're going to go into an airspace where "Ask for what you want" will receive a response of laughter from ATC, it's wise to try to give yourself as many options as feasible.
 
Radar Contact said:
I would. The only thing the ILS beats the LPV at is CatII/III ops (for now and small GA can’t do it anyways).

Stand by for the “you’ll be sorry when the Russians shoot down our satellites” comments. :)
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I'd be a lot more concerned about the actual interference testing by the U.S. military than a hypothetical attack by the Russians.

gps-interference-testing-png.61670
 
wayne said:
Having either is fine. I'd give up ILS if the initial savings for maintain ILS went to making more LPV approaches at other airports.
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There are currently 3998 LPV and 1549 ILS. Pretty much all runways that have an ILS also have an LPV.
 
I have not flown an ILS since 2008 in actual conditions. I regularly practice an ILS, but if ATC is using an ILS, I will request the RNAV. I have never been turned down, although vectors to final is the normal method of joining the approach because the path will overlay the ILS and I won't interfere with others flying the ILS. All that said, I would keep my ILS/VOR system as a backup. In the older installations with a separate GPS and Nav/Com, the primary CDI is usually switched between GPS and Nav and in most cases, the relay has spare poles to add the GS signals. If not, update the relay and keep the SL30, after all you still need a Com unit.
 
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