All things equal - which approach are you taking

[kaiser]

Simple question - i think?

Let's say I am flying into an airport, weather is going to be OVC005 and the airport publishes an ILS and RNAV approach into the favored runway. All approaches have mins of 200' AGL - all approaches basically have the same published missed - climb straight to 1500, left turn to 3000 to hold (The ILS has a heading - the RNAV is a direct to .. but both to the IAF/IF basically). Nothing NOTAM'd INOP and the aircraft is well equipped to handle basically anything. The ILS even has a feeder similar to the T structure of the RNAV - so no difference there either.

So which approach would you choose? ground based or space based? If weather is low with rain etc, do you gain efficiency or reliability using one versus the other? Anything else I'm not considering?

 

[eman1200]

RNAV backed up by ILS.

 

[midlifeflyer]

RNAV every time. Two reasons, the second is the important one to me.

Less subject to interference. That airplane that didn't stop at the critical area sign won't be a problem.

Less workload. For example, no need to ensure the correct ILS frequency is tuned, identified, and switched to active. No need to change CDI sources for the approach, and since you mentioned it was low, after going missed. All that means less opportunity for the user errors I see fairly regularly when giving recurrent training. I actually include a full-coupled ILS to the missed on checkouts and IPC because of the number of mistakes I've seen.

 

[Jim K]

Didn't see an option for NDB?

RNAV is harder to screw up as Mark said. No worries about something getting screwed in the changeover from GPS to VLOC mode. I do lots of hand-flown practice ILS and VOR approaches, but in actual cross country situations where I have family on board, I'll fly the coupled RNAV every time.

It feels like airports with commercial service tend to give ILS as default. BMI and CMI at least do. I THINK that's because there's still a lot of older commercial aircraft that don't have GPS approach capability? If they are advertising the ILS, I won't ask for something else, but they're generally giving vectors so there's less chance of having something programmed wrong. If I thought there was a good chance I'd have to go missed, I'd probably ask for the RNAV, again for simplicity sake, but my navigator will fly the ILS missed in GPS mode anyway so that's probably pointless.

 

[Feh]

Depending on the mood, I’ll take the ILS and if I screw it up then take the RNAV if I’m feeling like I haven’t flown an ILS in a while.

 

[EdFred]

ILS.

Russia can't tamper with it as easily.

 

[Clip4]

Ok, Wx is 500 Ovc. What is the ground visibility?

If an airport these days has both an RNAV and ILS, the airport is likely controlled. The ATIS will advise the ILS is in use and ATC will be sequencing aircraft accordingly.

Given a calm winds choice of an ILS on a runway with ALSF-1 or 2 and an RNAV to a runway with just a PAPI or VASI, I am taking the ILS.

Just because the reported Wx is 500-1/2 doesn’t mean it’s going to be 500 -1/2 at the end of the approach.

 

[MackMooney]

pretty much, rnav always, less work.

 

[TCABM]

Whichever is less workload, pays more money, or fills a currency I need that expires before the next flight.

Pretty much in that order.

 

[asicer]

RNAV for the second reason cited by @midlifeflyer

However, I don't think it's a huge difference. Maybe it's because of the equipment I usually fly.

Also, both RNAV and ILS are subject to interference but I haven't quite figured out which is worse.

 

[midlifeflyer]

If they are advertising the ILS, I won't ask for something else,

I do.

It usually sounds a little more formal but this was the actual dialog on a flight.

“Expect the ILS 6.”
“Expect the ILS 6. Could we get the RNAV? ”
“That’s fine.”

 

[JVerb]

Ok, Wx is 500 Ovc. What is the ground visibility?

If an airport these days has both an RNAV and ILS, the airport is likely controlled. The ATIS will advise the ILS is in use and ATC will be sequencing aircraft accordingly.

Given a calm winds choice of an ILS on a runway with ALSF-1 or 2 and an RNAV to a runway with just a PAPI or VASI, I am taking the ILS.

Just because the reported Wx is 500-1/2 doesn’t mean it’s going to be 500 -1/2 at the end of the approach.

I fly into KLBX a lot, because they have an ILS and RNAV at an uncontrolled field. Plus, the food at the restaurant is pretty good.

 

[jbarrass]

RNAV.

 

[dans2992]

Are there really still airliners that can’t fly an RNAV?

 

[AV8R_87]

5 years ago, I would've told you RNAV.
Now, with GPS jamming and spoofing being a real threat, I'd favor the ILS.

If I can have both, RNAV as a primary (much more stable) with ILS also tuned and indicating for cross-check.

 

[eman1200]

I do.

It usually sounds a little more formal but this was the actual dialog on a flight.

“Expect the ILS 6.”
“Expect the ILS 6. Could we get the RNAV? ”
“That’s fine.”

agreed. have done that several times, zero issues or pushback.

 

[455 Bravo Uniform]

ILS. I have 2 indicators and 2 Nav radios, but only 1 GPS and 1 indicator for it.

I didn’t like the momentary loss of enroute GPS I experienced for the first time last month. It was about 5 seconds and my A/P reacted oddly. I’m less confident in RNAV but don’t do hard IFR anyway.

 

[midlifeflyer]

agreed. have done that several times, zero issues or pushback.

i received a pushback once. It was about 25 years ago. I asked for the RNAV. It was still new enough that some of the fixes weren’t in the controller’s scope

My impression is that people who prefer but don’t think to ask either don’t really prefer or don’t like telling ATC what they want. There’s plenty of that going around.

 

[midlifeflyer]

If an airport these days has both an RNAV and ILS, the airport is likely controlled.

Including my home base, there are a half dozen nontowered airports within 50 nm of my home base with an ILS and collocated RNAV.

The ATIS will advise the ILS is in use and ATC will be sequencing aircraft accordingly.

I can see a possible issue if mixing with airline traffic on the primary arrival runway at a Bravo, but otherwise, asking for the collocated RNAV at a towered airport is a non-event.

 

[WDD]

Seems like of the the places I fly so few ILS approaches are available. And if an airport has an ILS approach it usually has just one, where the other runway(s) will have an RNAV. If I plan on an ILS runway and the wind changes, I'm back to RNAV. So again, it's simpler to just be in the "RNAV mindset" and use ILS as back up if I need it.

 

[Clip4]

Including my home base, there are a half dozen nontowered airports within 50 nm of my home base with an ILS and collocated RNAV.

I can see a possible issue if mixing with airline traffic on the primary arrival runway at a Bravo, but otherwise, asking for the collocated RNAV at a towered airport is a non-event.

The interior regions of the US have had about all the ILS approaches shut down 5 years ago except the MON airports.

The Class C airports can and do have rush hours.

 

[dmspilot]

Are there really still airliners that can’t fly an RNAV?

We do RNAV but no WAAS.

 

[Jim_R]

Now, with GPS jamming and spoofing being a real threat, I'd favor the ILS.

Unless I start flying in the Mideast or around Ukraine, or GPS starts becoming unreliable in the US, I am not concerned about GPS (un)reliability.

I live in a location where I see GPS jamming NOTAMs several times a year. I have yet to experience a GPS issue while flying, even when such a NOTAM was in effect.

On the other hand, I have experienced "ILS Out of Service" NOTAMs at my destination far more frequently--even once would be infinitely more frequently than GPS outages, and I've seen ILS OoS numerous times.

 

[frfly172]

RNAV ,with the ILS dialed in.

 

[jordane93]

Are there really still airliners that can’t fly an RNAV?

Every fleet at my airline can do RNAV approaches but I believe only the 220 and 350 can go down to LPV mins. The rest of the fleets have to use LNAV/VNAV mins. It’s really a moot point though because pretty much every airport we go to has an ILS.

And to answer the thread question, RNAV

 

[Kitch]

ILS just because my AP will track the GS on an ILS (less workload) That being said I'm fine with an RNAV too.

 

[WDD]

We do RNAV but no WAAS.

That is not what I would have expected. Why in the world no WAAS?

 

[chemgeek]

There is a lot less knobology involved in flying the RNAV approach, and for some GA aircraft, the autopilot is easier to configure for the RNAV approach if it can be configured for the ILS at all. The ILS can be tuned on NAV#2 for situational awareness. GPS approaches are stupid-simple to fly.

 

[jordane93]

That is not what I would have expected. Why in the world no WAAS?

Pretty much every airport that 121 carriers go to have an ILS. So there’s no need to spend the money to put WAAS in the planes.

 

[AV8R_87]

There is a lot less knobology involved in flying the RNAV approach,

Dial ILS freq in the receiver. Follow the needles. Couple autopilot if available.

I don't think that it takes less to set-up and activate an RNAV approach.

 

[dmspilot]

That is not what I would have expected. Why in the world no WAAS?

Cost-benefit analysis. I can recall going missed one time in 3 years because the RNAV minimums were too high. But we were able to get on an ILS for the opposite runway with a tailwind right at our limit.

 

[chemgeek]

Dial ILS freq in the receiver. Follow the needles. Couple autopilot if available.

I don't think that it takes less to set-up and activate an RNAV approach.

Anyone with an IFR GPS will be using enroute GPS navigation. Flying an ILS approach will require verifying switching the CDI from GPS to VLOC at final approach intercept and monitoring the audio to verify the ILS frequency selected. For the missed, you must verify switching from VLOC back to GPS. Some GA aircraft can only fly a coupled approach with the #1 NAV (which will be GPS if installed). It's not that it's hard to fly an ILS if necessary, but there is much less involved in terms of configuration to fly the GPS approach from GPS enroute navigation. After activating the loaded approach, the GPS approach is seamless from enroute through the missed approach.

 

[midlifeflyer]

Dial ILS freq in the receiver. Follow the needles. Couple autopilot if available.

I don't think that it takes less to set-up and activate an RNAV approach.

Yes, if you are having a complete GPS failure or choosing to not load the approach in your FMS for situational awareness or to sequence for a missed, you are absolutely correct.

 

[WDD]

Cost-benefit analysis. I can recall going missed one time in 3 years because the RNAV minimums were too high. But we were able to get on an ILS for the opposite runway with a tailwind right at our limit.

I would have thought WASS would be required for airliners if for nothing else to aid with flying direct vs Airways/VOR to VOR, as well of course give options for approaches. Eh - learn something new everyday.

 

[midlifeflyer]

I would have thought WASS would be required for airliners if for nothing else to aid with flying direct vs Airways/VOR to VOR, as well of course give options for approaches. Eh - learn something new everyday.

You don’t need WAAS for direct point to point enroute navigation. And, while you would not have LPV minimums capability, you don’t need WAAS to fly an RNAV approach.

 

[WDD]

Yes, I know you don’t need WAAS for point to point. But it is more accurate. And you can’t get LPV min approaches with non WAAS. Just thought the airlines would want that extra performance.

I would have guessed wrong.

 

[kayoh190]

Yes, I know you don’t need WAAS for point to point. But it is more accurate. And you can’t get LPV min approaches with non WAAS. Just thought the airlines would want that extra performance.

I would have guessed wrong.

If there's no financial advantage, they won't spend the money. LPV minimums don't provide much extra capability in a typical airline environment, so there's no perceived need to go through the certification process and train everyone up on it.

 

[midlifeflyer]

Yes, I know you don’t need WAAS for point to point. But it is more accurate

Maybe (I don't know if normal scaling is affected), but since enroute RNAV only requires 2 NM accuracy and RNAV SIDs ad STARs only 1 NM (in both cases, a significant improvement over VOR), does that really matter? Where it does matter is approaches (no LP or LPV) and the need for RAIM checking.

 

[jordane93]

Airlines already run on razor thin profit margins. They’re not going to spend money on things that they don’t see financially fit for the operation.

 

[Larry in TN]

Maybe (I don't know if normal scaling is affected), but since enroute RNAV only requires 2 NM accuracy and RNAV SIDs ad STARs only 1 NM (in both cases, a significant improvement over VOR), does that really matter? Where it does matter is approaches (no LP or LPV) and the need for RAIM checking.

We do RNAV RNP approaches down to RNP 0.10 and with RF-legs.

Some of us can do GLS approaches which are a form of LAAS, though they call it something else now.

The E-175 can do LPV approaches but not RNP, AFAIK.