Sometimes the MSFS ATC chooses RNAV as my approach over ILS…and was recommended it by a VATSIM controller once too. I was wondering why a controller, or robo controller would do that.
The only things I could find is if there are planes on the runway you are landing on that could mess up the ILS radar or if the ILS is not operating. Are there other reasons why an RNAV landing would be better? For context I am referring to flying an a320.
I find the MSFS ATC assignments are random. Sometimes I get ILS, sometimes I get RNAV. Sometimes I even get visual approach in a CAT III weather condition. I usually just request a different approach and choose ILS from the menu.
I can’t say the same about VATSIM though, I never use it.
Yes forget SIM ATC. As for Vatsim, you would have to share the airport and the flight plan you filed or even better ask in the Vatsim Forum the controllers which control that airport.
ILS is more accurate but some airport approaches eg LOWI from the west over the mountains can only be flown via RNAV as they don’t follow a straight line.
Indeed typically with both options for a given runway you’d only use an RNAV approach if the ILS is unserviceable.
As you mentioned there are other cases, for example into Gatwick it was (prior to this pandemic anyway) not uncommon to be instructed to fly the RNAV 26L when the A380 is ahead of you as it messes with the ILS beam and can give less than desirable results to any aircraft trying to shoot the ILS.
There are however sometimes other considerations such as noise. For example LFML prefer the RNAV for the northerly runways and only use the ILS if weather is deemed unsuitable (obviously minima, but also some tailwind criteria and no reported windshear etc).
It can be less work for the ATC controller as they don’t have to vector you to intercept the ILS localizer.
ie)
ACA123 vectors to final, turn left heading 170, decend 2000
wait and watch to time the 30 degree intercept
ACA123 turn left heading 110, cleared ILS RWY 08L approach
And this is all based on timing the turn correctly to intercept the localizer at the right altitude and distance, so you actually have to watch the aircraft more closely.
vs
ACA123 cleared RNAV Z RWY 8L VINLO transistion
and as long as the airplane is on the STAR you can clear them to the approach much earlier and you don’t have to watch the timing so closely, and as you can see, there is one less communication exchange. When things are busy, this can be a big deal.
You can also approach from the west on a conventional approach, I have flown that one many times. Only “problem” is that you’ll pass the airport and then have to circle for either runway. From the east it’s more or less straight in, strictly speaking there are no ILS approaches at Innsbruck, although the east approach has a glideslope, both are strictly localizer approaches and the glide is only for reference.
Yes. I meant the one over the Mieminger mountains (RNP Z RWY 08)
Hmm, I don’t understand why ATC has to vector. An ILS approach plate shows the IAF, IF and FAF with the required height to intercept the glideslope. Why is that any different than RNAV?
That makes sense for some approach like I think irnmn2 into LAX I think when you are supposed to get vectors at the end of the star. I can see on VATSIM if someone is doing clearances departures arrivals ect. they would like to reduce workload.
Yea, I don’t get it either. Arrivals (STARs) work with ILS and no vectoring is needed.
Yeah I’ve been cleared a few times for RNAV approaches with a perfectly working ILS on vatsim myself. Not being a vatsim controller, I have no idea what their policies are. This said, I would assume that certain airports and certain runways have preferred procedures in place, and that sometimes RNAV approaches are better suited for certain lateral and vertical profiles (terrain and spacing considerations). Not to mention there are some airports where ILS interference caused by aircraft being too close to the runway and other factors is quite a real thing.
Vectoring is used for separation… For example look at the approaches (STARS) into EDDM e.g. NAPSA 26L RNAV Transition… although being RNAV, you will always be vectored onto the ILS.
Meaning for a major European airport, there is no direct approach to any of the runways ILSs - you will always be vectored, regardless if you take the RNAV Transitions or any of the other STARS e.g. NAPSA 1B ARR via the OTT VOR. (Yes there are RNAV / VNAV approaches e.g. RNP RWY 26L, but these obviously dont use ILS).
The VATSIM controllers try to follow the real life policies… you can often find these controller directions (SOPs) on the VATSIM regional websites under the controller sections for a certain airport, where they give insights to new controllers on how to handle traffic. Being a pilot on Vatsim, I find this an interesting read as it gives one a better understanding, why things are happening as they are.
In addition the VATSIM forums give you also a very accurate response to any such questions.
I can tell you that from real life experience, I can’t come up with a scenario where I have been cleared for a RNP approach when an ILS approach was available. It doesn’t really happen in real life, ILS is always the preferred approach. Maybe the ILS was out of service in the NOTAMs and the VATSIM controllers were trying to replicate this?
This is not an issue unless talking about CAT II / III approaches, in which case you obviously need to fly the ILS due to the lower minima, just the flow of traffic in and out of an airport is reduced in such a way that the preceding aircraft has vacated and cleared the ILS sensitive area or has passed overhead the localizer antenna in case of departing traffic before passing a point where interference cause a significant effect.
Edit: ok I did come up with one scenario, in places like Innsbruck it might be better to fly the RNP-AR but only if the operator, crew and aircraft are suitably equipped, trained and approved for flying such a RNP-AR approach.
It is unusual, did you request the ILS and were asked to take the RNAV instead? Or did the controller simply suggest the RNAV?
Generally you’re completely within your rights as a pilot to request the ILS.
It is just about impossible for anyone here to get inside the head of a vatsim contoller if we don’t know everything that was going on that might have led him to some particular decision. Next time just ask for the ILS with the controller and see what he says… Most of the time they are trying to help you out, so maybe there was a reason the RNAV would be easier for you.
Worthy of mentioning that if you were landing at a secondary airport, and the controller was giving you ‘top down’ service from the Primary airport approach or enroute, he may not have known all the options at that secondary, or been as familiar with the procedures for that airport. I have seen that happen a few times with some oddball airports that the controllers aren’t used to servicing.
In my case I think the controller said “is RNAV ok?”
Can you say “Negative, ILS only please”?
You wouldn’t normally be so abrupt as ‘negative’, but you might go with something like “We’d prefer the ILS if available”
Disagree… you would say simply negative. Short and concise communications is required especially when it’s busy. It’s not considered rude in this context.
I saw someone state that vectoring is not required leaving a STAR to go to an ILS. This is actually the norm in the US and many other places. Europe does provided a lot of RNAV transitions but those are usually used only when traffic needs to be spread out; otherwise vectoring is expected to save time.
I am aware of two circumstances where a RNAV approach will be used in lieu of an available ILS. One, controller may pack traffic with less separation using GPS/GNSS in some situations; and the other, using GLS if aircraft is equipped.
None of this applies to MSFS, which in this regard is just a game when using artificial ATC. The stock ATC is the least realistic thing about this platform… well, sometimes the weather competes for the distinction.
Heh, no, YOU would simply say negative. I would not.
“Negative” implies that you’re simply not going to do it. You are in effect asserting that ILS is your only option. This is not the case in this discussion. The ILS is a request, so tacking on negative wouldn’t be appropriate (in my opinion).
While it is true you’re not saying something like ‘Negative, Unable’, the ‘negative’ on its own carries a bit of an imperative by context.