GPS Navigation only vs with VOR/ILS

[DCarlton]

1 hour ago, EricJ said:

They're doing a bunch of expensive remodels at our airport (KDVT), moving taxiways, etc., etc., in order to make enough room to meet the clearance specs for an ILS installation.   In other words, they're spending a lot of money in order to be able to install an ILS.   We already have RNAV approaches from both directions.   I think for high-traffic or critical areas they're taking GPS outage/security seriously (like the VOR MON) and want to have approaches available at enough airports in the event of the unavailability of GPS.

Exactly.  I retired after 35 years as a Govt. engineer.  I've watched the Govt. foster competition to make sure there were always multiple solutions available to reduce dependencies on single vendor solutions.  I have this gut feeling that our ILS/VOR infrastructure will be around for a very long time.  IMO, planes need to be able to land with simple charts and plates and without total dependency on commercial suppliers and IT for data base updates.  The Govt. understands GPS vulnerabilities and the risk of single solutions.  

[kortopates]

They're doing a bunch of expensive remodels at our airport (KDVT), moving taxiways, etc., etc., in order to make enough room to meet the clearance specs for an ILS installation.   In other words, they're spending a lot of money in order to be able to install an ILS.   We already have RNAV approaches from both directions.   I think for high-traffic or critical areas they're taking GPS outage/security seriously (like the VOR MON) and want to have approaches available at enough airports in the event of the unavailability of GPS.

But since none of your LPV approaches are good down to precision minimums of 200 1/2 the infrastructure improvements will also provide for better minimums on your LPV approaches. For example you need a approach lighting system to get minimums down to 200 & 1/2 so i bet these changes will help the GPS approaches too

[carusoam]

If flying in IMC…

Have two independent systems of reaching the ground….

1) WAAS GPS

2) VOR/ILS

 Check to see if the fancy modern GPS boxes also have VOR/ILS capabilities built in… that actually use the ground based antenna system.

We have seen simple antenna issues keep an instrument from working…

GPS antennas are extra sensitive…

Those are the best available for a Mooney…

After that… have enough fuel to fly to VMC…

Or know where and how to use a radar approach….  

PP thoughts only, not a CFII…

Best regards,

-a-

[PeteMc]

12 hours ago, carusoam said:

Or know where and how to use a radar approach….  

I just moved next to an AFB.  I've always heard how they need to keep current on Radar Approaches, so I'll find out soon.

Haven't done one since a PPP years ago in RI.

 

[Pinecone]

On 5/2/2023 at 1:06 PM, DCarlton said:

Exactly.  I retired after 35 years as a Govt. engineer.  I've watched the Govt. foster competition to make sure there were always multiple solutions available to reduce dependencies on single vendor solutions. 

One of the coolest ones of these I saw was for ammunition for the GAU-8A on the A-10.

There were two companies.  But when the contract got rebid, the winning bidder got 80% of the production, and the losing one still got 20%.  So that the next time the contract was rebid, there would be two bidders.

And over about 5 years, the ratcheted the cost per round down by more than 40%, IIRC.

[Van Lanier]

Over the last 53 years of flying, I've found that having options and backups are good things.  My little 20C has a GNC 355 with separate indicator, a refurbished KX155 with GS and separate indicator, and a DME.  This gives me GPS nav and approach; VOR nav and ILS approach; the occasional VOR approach for fun, and MON capability if needed.  I back this up with an Aera 660 with its own battery.  If I could find an STEC 30 that came from another Mooney, I could stop hand flying all the time and learn how to really program the GPS!  

[hammdo]

Ditto on options! Hum… my wife’s maiden name is Lanier - from KY…

-Don

[PT20J]

I was kind of amazed on my last two 1000 nm+ trips how many VORs were NOTAMed OTS. 

[Pinecone]

But looking at a the charts, there were a LOT of VORs.

[jlunseth]

First, I prefer ILS approaches to RNAVs. ATC is much more comfortable giving vectors to final with an ILS and ILS approaches are generally inherently shorter approaches to fly anyway. RNAVs are fine and work well with GPS based nav systems, but man, you have to fly 15 or 20 miles past your intended airport in order to get on some RNAVs and then fly another 15 or 20 miles to get to the missed hold. Second, I want options. I have had the GPS decide, during an LPV, that it does not have enough satellites and the approach has to convert to something else or be abandoned entirely and then what? Or for whatever reason a Glideslope comes in on one receiver and not the other. I have two separate systems. System one drives the AP and is a 750 Xi with the signal going through an ICARUS Sam GPSS and then two 275's (AI and HSI) that are primary instruments. The second is a 430AW separately connected to its own CDI. Not a big fan of the "integrated system red X" that does actually happen. It is not common that one system cooperates and the other does not, but have had it happen on one or two occasions. Even once, when you are trying to get down with Tstorm activity advancing is enough to justify separate systems in my view. I also had a DME installed. Cheap insurance. And I have a primary AI (275) and a backup AI that is a different technology and separate from the primary.

[midlifeflyer]

2 hours ago, jlunseth said:

First, I prefer ILS approaches to RNAVs. ATC is much more comfortable giving vectors to final with an ILS and ILS approaches are generally inherently shorter approaches to fly anyway. RNAVs are fine and work well with GPS based nav systems, but man, you have to fly 15 or 20 miles past your intended airport in order to get on some RNAVs and then fly another 15 or 20 miles to get to the missed hold. 

They may be there but I have never seen either of those issues. Coming from the departure side of an airport, I have seen no difference inbeing vectored to intercept final; whether ILS or RNAV. (From the arrival side, if it's already on my route of flight, I'll happily ask for "the RNAV X from FXNME.")

Nor have I seen a 15-20 nm difference between the missed. Do you have any examples.?

Color me, "Approach. request the RNAV" although I'm happy to do an ILS too.

[ilovecornfields]

At one of the airport I regularly fly into the controller has mentioned that there’s more flexibility for the ILS compared to the RNAV approach for the same runway. Both approaches have the same minimums and the RNAV has an easier missed approach so that what I usually request but I guess with the ILS they can vector you closer in than with the RNAV.

I once had a controller tell me to hold as published on the KBFL ILS 30R on a day with particularly crappy and bumpy weather with my family on board. I didn’t really want to do that and I knew the RNAV didn’t have a hold so I just told him that we’d already set up for the RNAV and there was no hold published so could we just get vectors to final. He let us have it but then told everyone else to expect the ILS and gave them all holds 

[rbp]

ANother difference between LPV and ILS is that the MAP procedure on an ILS is usually a VOR, so the VOR has to also be working, and because a VOR signal is a “cone” the obstacle clearance surface for a VOR-based missed is wider (depending on the distance to the VOR) and therefore might be higher than for a GPS-based missed (which is a “tube”)

oh, and on an LNAV approach, as you get closer to the airport, the sensitivity of the needle goes from being a “cone” to being a “tube” (a “funnel”?)

an LPV can be established on both side of the runway, and the crosswind. its not unusual to have 1 ILS and 4 RNAV approaches to a “cross” configuration pair of runways. (are there still any BC approaches??)

[PT20J]

The controllers generally advertise the ILS because the assumption is that everyone can use that while not everyone has LPV capability. However, the pilot gets to select the approach, not the controller, and they will happily give you whatever approach you want to the active runway. I have even requested and been cleared for approaches in the opposite direction of the active when I didn't want to circle and could accept the tailwind. You have to ask for that early because the approach controller has to coordinate that with the local controller, but they are happy to do it if they can.

I prefer the LPV over the ILS because the workload is lower. All I have to do is put the GFC 500 in APR mode when cleared, rather than tuning, identifying, checking that the GTN switched from GPS to VLOC. Also, the missed approaches are often simpler with RNAV. It probably varies by approach design, but I've never found any substantial differences in vectoring for RNAV vs ILS approaches.

Skip

[47U]

13 hours ago, rbp said:

are there still any BC approaches??

Merced has a BC approach.  Perhaps more rare, at least in California central valley, is the NDB approach.  

   

[jlunseth]

20 hours ago, midlifeflyer said:

They may be there but I have never seen either of those issues. Coming from the departure side of an airport, I have seen no difference inbeing vectored to intercept final; whether ILS or RNAV. (From the arrival side, if it's already on my route of flight, I'll happily ask for "the RNAV X from FXNME.")

Nor have I seen a 15-20 nm difference between the missed. Do you have any examples.?

Color me, "Approach. request the RNAV" although I'm happy to do an ILS too.

Sure, they are the norm here, although to get to the 15-20 mile distance you may have to include the outbound leg of the missed hold. See e.g. the RNAV 31 at KGYL(11 miles to the missed hold plus 4 for the outbound leg), the RNAV 33 at KHCD (12 to the missed hold plus 4 for the outbound leg), or just about any of our rural RNAVs in MN. You can just skip around to any of the other rural airports in southern MN if you want to verify. Sure if you happen to be coming from the right side of the airport you may be able to fly in from a more convenient IAF but can’t count on that. Our ILSs in MN generally use a nearby VOR for the missed hold, which is either right on the airport (see e.g. the ILS 13 at Willmar (where Oasis Aero is located)) or close by (ILS 30 at KLVN). 

I fly quite a bit of practice approaches, both VFR and IFR. The RNAVs are all long compared to the ILSs. Long ride through the initial approach segment and long ride out to the missed. 

[rbp]

7 hours ago, 47U said:

Merced has a BC approach.  Perhaps more rare, at least in California central valley, is the NDB approach.  

   

can you actually get it? I asked for the KABE VOR-A, which was in the database, but they said its no longer available 

[rbp]

On 5/30/2023 at 8:56 AM, jlunseth said:

irst, I prefer ILS approaches to RNAVs. ATC is much more comfortable giving vectors to final with an ILS and ILS approaches are generally inherently shorter approaches to fly anyway. RNAVs are fine and work well with GPS based nav systems, but man, you have to fly 15 or 20 miles past your intended airport in order to get on some RNAVs and then fly another 15 or 20 miles to get to the missed hold.

5-9-1 VECTORS TO FINAL APPROACH COURSE

Except as provided in paragraph 7-4-2, Vectors for Visual Approach, vector arriving aircraft to intercept the final approach course:
At least 2 miles outside the approach gate unless one of the following exists:

When the reported ceiling is at least 500 feet above the MVA/MIA and the visibility is at least 3 miles (report may be a PIREP if no weather is reported for the airport), aircraft may be vectored to intercept the final approach course closer than 2 miles outside the approach gate but no closer than the approach gate.

If specifically requested by the pilot, aircraft may be vectored to intercept the final approach course inside the approach gate but no closer than the final approach fix. 
EXCEPTION. Conditions 1 and 2 above do not apply to RNAV aircraft being vectored for a GPS or RNAVapproach

------------------------------------------------------------

so, on a ILS, you could get vectored inside the gate under certain conditions, but 15-20 miles seems excessive

[midlifeflyer]

2 hours ago, jlunseth said:

Sure, they are the norm here, although to get to the 15-20 mile distance you may have to include the outbound leg of the missed hold. See e.g. the RNAV 31 at KGYL(11 miles to the missed hold plus 4 for the outbound leg), the RNAV 33 at KHCD (12 to the missed hold plus 4 for the outbound leg), or just about any of our rural RNAVs in MN. You can just skip around to any of the other rural airports in southern MN if you want to verify. Sure if you happen to be coming from the right side of the airport you may be able to fly in from a more convenient IAF but can’t count on that. Our ILSs in MN generally use a nearby VOR for the missed hold, which is either right on the airport (see e.g. the ILS 13 at Willmar (where Oasis Aero is located)) or close by (ILS 30 at KLVN). 

I fly quite a bit of practice approaches, both VFR and IFR. The RNAVs are all long compared to the ILSs. Long ride through the initial approach segment and long ride out to the missed. 

Well, I don't really care about practice approaches when it comes to an RNAV vs ground-based discussion. But...

KGYL only has RNAV approaches, so there's no ground based alternative to compare it to.

The VOR approach at HCD is scheduled to be decommissioned next year, so again, no choiceEven without that, I'll take the official vertical guidance to a lower DA on the LPV over the VOR as far more likely to avoid the need for the missed.

On the ILS at VLN, yes I agree the missed for the ILS is closer for that typically small percent of the time it's needed. I'm curious though... given the proximity to the LSP Class B, what is the real likelihood of getting the published missed in the real (as opposed to practice) world?

The is really personal preference. On balance, you like ground based navaids. I like RNAV.

 

 

[rbp]

36 minutes ago, midlifeflyer said:

what is the real likelihood of getting the published missed

I read in r/ATC that the published missed in a RADAR environment is only ever flown for lost comms, or in training. 

[midlifeflyer]

32 minutes ago, rbp said:

I read in r/ATC that the published missed in a RADAR environment is only ever flown for lost comms, or in training. 

It's definitely not "only." If they don't issue custom missed approach instructions the published is what you fly. Happens often at nontowered airports so long as the published missed doesn't put you where you might create a traffic conflict. But that's why I asked about it.  

Even with the published missed, once you check in with Approach, you're almost sure to get, "Radar contact. Fly heading..." so it would be rare to get to the MAPH unless you specifically asked for it for some reason. Interestingly, it may even be more common not to get custom missed instructions on an RNAV approach precisely because, not being tied to a ground navaid, so many are straight ahead climbs (another thing in their favor - typically less workload on the single busiest segment of an IAP than with a ground based missed).

[rbp]

1 hour ago, midlifeflyer said:

only ever flown for lost comms

yes, fair point. I shouldn't have said "only", 

although goong missed at an untoward airport is effectively "lost comms" because you have no one to give you alternate missed instructions until you switch back approach freq

[midlifeflyer]

On 5/30/2023 at 12:31 PM, rbp said:

are there still any

BC

approaches

 

43 LOC BC approaches still there.

[midlifeflyer]

1 hour ago, rbp said:

yes, fair point. I shouldn't have said "only", 

although goong missed at an untoward airport is effectively "lost comms" because you have no one to give you alternate missed instructions until you switch back approach freq

Custom missed instructions are given before  you leave ATC. It's really hard to say, "on the missed fly heading 230, climb and maintain 3000" after you have gone missed and flown straight ahead on the published.

[McMooney]

I'm sure iah and hou are better but around Houston most ILS/LOC/VORs are notam'd out most of the time.   Only reason I've even tried an ILS was to verify green needles on the G5's and that was notam'd unmonitored.

Edited May 31, 2023 by McMooney