How do RNAV STARs increase capacity?

[NorthSouth]

I see a lot of claims by airports that the implementation of RNAV STARs enables them to handle more traffic.

Can some kind ATC soul explain to me how - at airports where 3nm separation is already in place - a change from vectoring aircraft to final approach via quite widely laterally-separated routes, to routing every aircraft along a single narrow RNAV route to final, can possibly increase the number of arrival movements?

[ZOOKER]

Nice one. :E

[10 DME ARC]

Where I work RNAV star's are used to increase the amount of aircraft which the arrivals controller can handle only have to concentrate on merge points and making the best order. The aircraft only go on to headings for base and intercept turns, believe me having worked without RNAV star's it makes a lot of difference! plus it gives pilots a programmed arrival route with a known max track miles to touch down.

[eckhard]

plus it gives pilots a programmed arrival route with a known max track miles to touch down.

True, but what pilots really want is the realistic minimum track miles to touch down. When I used to fly to Dublin, the only thing known about track miles was that they were going to be a lot shorter than that shown by the full STAR. Generally speaking, on the VATRY arrival, the ‘arc’ to DW706 was cut off and we got a vector to intercept the LOC, or direct to LAPMO, which reduced the track mileage by about 30nm.

[good egg]

True, but what pilots really want is the realistic minimum track miles to touch down. When I used to fly to Dublin, the only thing known about track miles was that they were going to be a lot shorter than that shown by the full STAR. Generally speaking, on the VATRY arrival, the ‘arc’ to DW706 was cut off and we got a vector to intercept the LOC, or direct to LAPMO, which reduced the track mileage by about 30nm.

I’d guess that’s what airline ops departments do once they have sufficient evidence to build up a “base case” following a change in procedures?

[ZOOKER]

"Airline ops departments, sufficient evidence and base case".......Can't you just talk to the pilots? The folk at the 'pointy ends'........"End users", (In modern 'management-speak'), when you all meet at 'Pilot-Controller Forums'

You still hold 'Pilot-Controller Forums', don't you?

[good egg]

"Airline ops departments, sufficient evidence and base case".......Can't you just talk to the pilots? The folk at the 'pointy ends'........"End users", (In modern 'management-speak'), when you all meet at 'Pilot-Controller Forums'

You still hold 'Pilot-Controller Forums', don't you?

Zooker, I’m not sure who this is aimed at? It is simple math/maths (depending on your audience). You can ask a pilot, or crew, of their experiences, but it won’t necessarily reflect the overral factors. Everyone’s viewpoint is different. Some people are bullish, some are pragmatic...

[10 DME ARC]

Updated expected track miles are given as soon as sequence decided, especially if it involved a much reduced distance!

[eckhard]

Well that’s very helpful but never happened at DUB. The first we knew about it was, “route direct to LAPMO, report established”.

[NorthSouth]

it gives pilots a programmed arrival route with a known max track miles to touch down.OK, but if all traffic is following that single programmed arrival route, I still don't get how that increases the arrival rate, *unless* it's a point-merge or trombone design. If it's a single route design, with the only flexibility being the point at which aircraft are vectored to final, then all that's happening is that the point at which vectoring occurs is much later than under a non-RNAV set-up. Which means that you can't use lateral separation until much later in the sequence - which is surely less flexible and does nothing to increase the probability that you can achieve minimum separations on final? Am I missing something fundamental?

[core_dump]

This discussion of track miles is all very interesting, but nobody has answered the guy's question. I'm eagerly awaiting the answer as well.

[GASA]

From what I’ve heard about it the real ‘benefit’ will be to have less controllers handling more traffic. With the aircraft on standardised routes the controller can focus more on the initial order and then the final approach spacing. No need for radar 1 and 2, just one person doing both.

[ZOOKER]

GASA,
Call me cynical, but I think you've hit it. If I remember correctly, one of the contributing factors in the Uberlingen accident, was 1 controller doing 2 jobs. The 2 747s at FL340 over NEVIS a couple of years ago, might not have got so adjacent, had the 'planner' been in the vacant seat.
The more eyeballs you have, looking at the radar......Sorry 'situation display', the better, and with 30% more aeroplanes forecast, you'll certainly need more eyeballs.

[10 DME ARC]

We use trombones and the increase in traffic comes from not vectoring everyone all over the sky! With RNAV fixed tracks your work load reduces dramatically hence you can handle more traffic! I also know of places where RNAV/radar monitored tracks, done from the VCR, have replaced the radar controller over night!

[NorthSouth]

10 DME ARC, yes, I understand how it might increase arrival rates if you use a trombone, and the fact that doing less vectoring reduces controller workload, but I still can't see how - mathematically if you like - having all your arrivals one behind the other on the same route can lead to closer spacing on final than having your traffic on a variety of routes, using a combination of vertical and lateral separation, which then gives greater flexibility in getting them on to final with minimum separation.
And in any case, isn't the ultimate determinant of arrival rates always going to be wake separations on final?
The more I hear the more I think GASA's right.

[10 DME ARC]

NorthSouth - Correct the vortex order makes the arrivals rate but having multiple routes joining a couple of trombones and the ability to easily short cut/extend makes this possible far easier than by vectoring. Believe it or not but that does up the arrival rate!

[NorthSouth]

Like I say, it's not the trombone or point-merge designs I'm talking about. It's the situation at most UK airports where RNAV STARs more or less replicate the conventional arrival routes, so that in many cases you will now have a single route carrying the bulk of the inbound traffic, but without the flexibility of vectoring until you get much closer to the final approach.

[GASA]

Sorry but I still don’t see how it increases capacity. If a controller, or two, can sit there and vector planes at minimum wake turbulence spacing then where does this RNAV STAR fit more planes in? What I’m hearing is that it maybe fits the same amount of planes except that it’s only one controller doing it.

Actual increase of capacity would be what Heathrow did by introducing lower wake turbulence spacing in different winds.

[Dan Dare]

This is just TITS isn't it? A zombie resurected from the 80s which looked brilliant in the simulator by having more predictable (=inflexible) flow through the sectors to increase the airspace capacity. Wasn't it was shelved when they realised that the UK sometimes gets weather and when aircraft can't fly in the standard tunnel the whole system falls down. There is no improvement to runway capacity or final approach spacing.

TITS for those too young to know was Tunnels in the Sky

[ZOOKER]

Dan, that's the story I heard.

Allegedly, around £20m was spent on the project.....Glossy brochure and a BIG simulation down at the EU. One unit in the north sent a Scotsman down to find out what was taking place.....He was very impressed with what he observed.
Allegedly, on the last day/critique thingy he said....."Just one question.....What happens when everyone starts avoiding Wx?".

It all went a bit quiet, and CCF/TITS was never heard from again!

PS.....I had a splendid pub-lunch with aforementioned Scotsman today! :ok:

[NorthSouth]

So....when (for example) Edinburgh finally gets its ACP running again to the satisfaction of the CAA, and gets its RNAV routes approved, they'll last a couple of years until they demonstrably can't handle the amount of inbound traffic. So then they'll have to introduce a new proposal for point merge or trombones - or just vectoring to achieve lateral separation! The CAA and the public are gonna love that.

[LEGAL TENDER]

Zooker, any system falls apart when everyone starts avoiding weather. Just look at the Heathrow and Gatwick slots on a windy or foggy day.

[EastofKoksy]

In my experience increased capacity claims for RNAV, point merge etc are mainly just ‘spin’.

RNAV does create an opportunity for more standardisation which could reduce complexity. This in turn could reduce the number of controllers needed. The downside is less flexibility, increased fuel uplift to prepare for flying the full route and possibly an increase in track miles compared with present day ops.

[ZOOKER]

Hi LEGAL TENDER,

yes, I appreciate that it does, and it's provided a lot of entertainment down the years.
It's about 30 years since CCG/TITS it was trialled and deemed like a good idea at the time. Wx might not have been the only factor in it's demise, but was a large one. I still have the Technicolour brochure all about it.