ILS or RNAV that is the question...

[jwenham 1]

Just out of curiosity... what kind of approaches are you all flying, ILS or RNAV and why would one be more appropriate than the other? Also... question #2, if flying a RNAV app. do you also program the ILS frequency or do you just rely on VNAV for descent to the runway?Thanks in advance, Jim

[NJ_Flyer 3]

I mix it up and fly all types. ILS, VOR, NDB, RNAV. Not all runways have an ILS or RNAV so you might have to do a VOR or NBD app. If given the choice between an ILS and RNAV in marginal weather... the ILS is a precision approach and will get you to a lower level before you miss out.If you are commencing a RNAV app, you do not need to have the ILS tuned. As a matter of fact it may very well confuse the issue if you do. The decent path for the ILS maybe slightly different to the RNAV; you might get away with it but at some fields this could be dangerous.

[jwenham 1]

So RNAV is a more visual type approach where the pilot is responsible on his/her own for the final G/S path?

[fakeflyer737 1,021]

So RNAV is a more visual type approach where the pilot is responsible on his/her own for the final G/S path?

No, RNAV (I think most of them) have Lateral Guidence, just like an ILS except its RNAV and not as accurate so you'll have higher mins. Remeber, RNAV is NON PRECISION.

[ACA034137 37]

My understanding is that RNAV is LNAV/VNAV controlled down until minimums. No autoland...but I could be wrong :(

[Tabs 2,790]

That's correct - RNAV is still considered non-precision and have much higher minimums than an ILS.

[downscc 1,327]

However, GLS is a GPS-based approach that is considered precision. Last I checked they had a couple at KEWR. The approach is supposed to be a lot cleaner than UHF/VHF technology-based ILS; no problems with aircraft in the wrong place on the ground, no bending of the beam, no false glide slope and so on.

[jwenham 1]

So you would want a ILS over a RNAV unless the airport is not equiped with ILS? Im just trying to figure out why the need for an airport to have RNAV AND ILS options for the same runway. Take for an example KTPA - I can choose ILS for 1R or RNAV for 1 R. What would be the situation for RNAV to be used over ILS when both options are available?

[Tabs 2,790]

It's really up to the pilot. You could also use the RNAV if the ILS was out for servicing or something. A lot of airports also have VOR or NDB approaches to the same runway that an ILS is present on too. In practice you're usually going to see two approaches actually being used at most major airports though - visuals and ILSes.Dan, yeah GLS is different, it's not technically called an RNAV approach - it uses both the FMS/GPS and a ground-based transmitter called LAAS that ensures there's no error in the GPS signal and position:Here's an example of it:http://flightaware.c...GLS+RWY+04L/pdfHas the same minimums as a Cat I ILS. Notice the LAAS channel and ID at the top left.The LAAS technology:http://en.wikipedia....entation_System

[jwenham 1]

Thanks for the info guys!

[masneoquil 66]

On the same topic... Is permitted to fly a visual approach with the autopilot on and ILS captured until the visual minimums?

[scandinavian13 5,192]

For what it's worth, if you listen in to ATC on LiveATC, you'll primarily hear visual or ILS to the major fields (unless requested otherwise).

On the same topic... Is permitted to fly a visual approach with the autopilot on and ILS captured until the visual minimums?

For those who nitpick, spare me on this one, I'm paraphrasing broadly:Visual essentially means you can do whatever you'd like to get down on the runway (provided it's reasonable). That said, you're more than welcome to fly down on APP mode on the LOC/GS. There are no visual minimums, by the way. There are autopilot minimums, but no vis minimums.

[masneoquil 66]

For those who nitpick, spare me on this one, I'm paraphrasing broadly:Visual essentially means you can do whatever you'd like to get down on the runway (provided it's reasonable). That said, you're more than welcome to fly down on APP mode on the LOC/GS. There are no visual minimums, by the way. There are autopilot minimums, but no vis minimums.

Thanks Kyle, the autopilot minimum it's in the chart or it's a general rule?

[scandinavian13 5,192]

Thanks Kyle, the autopilot minimum it's in the chart or it's a general rule?

You're welcome. It's actually an FAR.It's something to the effect of "twice the max loss of altitude expected on an unexpected AP disconnect ("AP malfunction"), or 500', whichever is higher." Most of the time, company SOP dictates somewhere around 1000' except in certain circumstance (CAT-II/CAT-III approaches, and so on).That reference is specifically from Part 135, but the 737 is mostly flown by Part 121 rules. I'd expect similar there, however.EDIT: Just saw your location. The above is obviously for the States (per the FARs). I'd expect Argentina to be similar, but their rules might be slightly different.

[masneoquil 66]

You're welcome. It's actually an FAR.It's something to the effect of "twice the max loss of altitude expected on an unexpected AP disconnect ("AP malfunction"), or 500', whichever is higher." Most of the time, company SOP dictates somewhere around 1000' except in certain circumstance (CAT-II/CAT-III approaches, and so on).That reference is specifically from Part 135, but the 737 is mostly flown by Part 121 rules. I'd expect similar there, however.EDIT: Just saw your location. The above is obviously for the States (per the FARs). I'd expect Argentina to be similar, but their rules might be slightly different.

Thanks. Anyway, I don't fly over here to much. It's quite desolated here in FSX :(