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Optimize Runway Capacity  
User currently offlineFlexo From St. Helena, joined Mar 2007, 406 posts, RR: 0
Posted (7 years 5 months 3 weeks 4 days 5 hours ago) and read 2142 times:

I looked at Denver Airport on Google Earth and noticed that they had the runways 25 and 26 in use while using 25 for take-off and 26 for landing only. At the time the picture was taken that configuration resulted in a 15 plane take-off queue for runway 25.

(North is on the right side of the picture)

Big version: Width: 959 Height: 317 File size: 62kb

So I was wondering if they really used their runway capacity in the best possible way or if they could have shortened the line by making better use of the runways.

So my question is, if you were to cramp in as many flights as possible with two runways, would you split them up - one only for take-offs and one only for landings or would you use both runways for both purposes at the same time? I.e. one plane takes off, one lands, one takes off and so on.

11 replies: All unread, jump to last
 
User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 1, posted (7 years 5 months 3 weeks 4 days 5 hours ago) and read 2138 times:

My experience says you are able to maximize runways best with the current runway separation criteria in the U.S. by segregating runways for arrivals and runways for departures. With that situation you have the ability to bang departures out with no delays while waiting for the landing aircraft to roll out and exit the runway....first departure rolls, next aircraft into position and hold, roll the second, third on and hold again, and so on and so forth. Only delays if you have diverging courses would be wake turbulence separation.

Arrivals, first aircraft on the runway and turns off, second aircraft crossing the threshold and exits the runway, third aircraft at the threshold and on and on and on....only delays again for wake turbulence separation.

There are many operating techniques, some of them are necessary due to airport layout and then others dictated by weather at the time.



Any views shared are strictly my own and do not a represent those of any former employer.
User currently offlineNbgskygod From United States of America, joined May 2004, 815 posts, RR: 1
Reply 2, posted (7 years 5 months 3 weeks 4 days 5 hours ago) and read 2136 times:

The thing about Google Earth and other Aeriel imaging sites, is that it doesn't show the full picture of air traffic. The reason they may be using one runway for departures and one runway for arrivals is that there may also be a lot of arrivals as well. By using this configuration they can sequence the arrivals and departures tighter because they don't have to make room for both on the same runway.

This shot does look like a very inefficient way of moving traffic, but it may just have been one of those times when everyone leaves at the same time.



"I use multi-billion dollar military satellite systems to find tupperware in the woods."
User currently offlineFlexo From St. Helena, joined Mar 2007, 406 posts, RR: 0
Reply 3, posted (7 years 5 months 3 weeks 4 days 4 hours ago) and read 2129 times:

Quoting IAHFLYR (Reply 1):
only delays again for wake turbulence separation

That was why I thought ATC could take advantage of the delays between arriving flights to squeeze in a departure.

Quoting Nbgskygod (Reply 2):
The reason they may be using one runway for departures and one runway for arrivals is that there may also be a lot of arrivals as well

Yes, I was thinking the same thing, arriving flights are hard to spot on Google Earth as they can obviously taxi straight to the gate without having to wait in line.


User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 4, posted (7 years 5 months 3 weeks 4 days 2 hours ago) and read 2103 times:

Quoting Flexo (Reply 3):
That was why I thought ATC could take advantage of the delays between arriving flights to squeeze in a departure.

The wake turbulence situation on arrivals would only apply when added separation is required....there are far more arrivals in a day at most airports that don't require added separation for wake turbulence, then there are those that get a bundle of arrivals that are all requiring added room.

Your idea in most cases doesn't significantly reduce any departure delays and a B744 as example quite often makes no haste in exiting the runway for the departure holding in position if the ATC facility is lucky enough to be able to use position and hold even.



Any views shared are strictly my own and do not a represent those of any former employer.
User currently offlineInnocuousFox From United States of America, joined Dec 2003, 2805 posts, RR: 14
Reply 5, posted (7 years 5 months 3 weeks 3 days 22 hours ago) and read 2075 times:

Keep in mind, Usually DEN is using 4-6 runways - not 2. The only time they would use 2 is if they had killer winds from the east or west and couldn't use the N/S sets.

The flow on departures is much better if you use it only for that. I have often listened to the DEN tower controllers get into a groove with their radio calls. Other departure only runways will be the same. Typically it will be like this:

B, clear for takeoff
C, position and hold
A, contact departure
C, clear for takeoff
D, position and hold
B, contact departure
D, clear for takeoff
E, position and hold,
C, contact departure

They are blowing them out of there like crazy! The next aircraft is given the p&h call when the one prior is rolling. That way, he's sitting there pointing straight down the runway when the prior aircraft gets to the exact right distance - then he gets the call to roll out.

When you mix and match, there's too much variation in speeds and distances between the flights to get it completely efficient. Let's face it, they aren't exactly 3 miles apart at all times. It depends on when they turned base, their speed, etc.

Also, about the original question, remember that UAL runs banked hubs in DEN - this sort of queue will always develop anyway. Heck... look at the simultaneous pushbacks! And that's just a few gates on one side!


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User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 6, posted (7 years 5 months 3 weeks 3 days 14 hours ago) and read 2057 times:

Quoting InnocuousFox (Reply 5):
they aren't exactly 3 miles apart at all times.

Keep in mind, they don't have to be!

Visual approaches following the preceding aircraft and runways that have reduced separation on final available to them are legal to go down to 2.5 NM on final inside of 10 miles from the threshold even in IFR weather as long as the tower is able to see the turn off points, not having wake turb as an issue.  

[Edited 2007-03-30 14:04:12]


Any views shared are strictly my own and do not a represent those of any former employer.
User currently offlineSailorOrion From Germany, joined Feb 2001, 2058 posts, RR: 6
Reply 7, posted (7 years 5 months 3 weeks 2 days 14 hours ago) and read 1989 times:

It very very much depends on procedures. With the standards of the EU, a mixed mode operation will give you a higher throughput than a segraded mode on a single runway. However, it depends a whole lot of fleet mix. The more Heavies you get, the more you gain with mixed mode. If you're all Mediums (i.e. can come in with 2.5nm seperation and leave with about a 6.000ft speration) it doesn't really matter much. But in DEN the taxi from the terminal to the 26 is lengthy. Another thing you never should forget is airspace. Even if you have a fleet mix and conditions that allow you to spit out 60 or planes off a single runway doesn't mean the airspace can cope with it. Famous example are for example 22L departures in ORD with MDW in 13C mode give trouble, other problems can be found with JFK-EWR-LGA interaction. Also en-route airspace is a problem. I've already been sitting in perfectly good WX at a smoothly running MUC airport for 45 minutes to get an en-route slot to LGW because airspace over western Europe was crowded. RVSM have allevated that problem a little.

If I look at my home airport, MUC it does operate two runway in mixed mode, yielding 90 operations an hour (maximum landings and take-offs at 58/hour) in IFR conditions with non-contaminated runways (i.e. dry or wet). Perfect VFR mode give over 100 (107 was the max afaik), fleet mix is around 7% Heavies plus a bunch of 757s.

SailorOrion


User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 8, posted (7 years 5 months 3 weeks 2 days 10 hours ago) and read 1971 times:

Quoting SailorOrion (Reply 7):
With the standards of the EU, a mixed mode operation will give you a higher throughput than a segraded mode on a single runway. However, it depends a whole lot of fleet mix. The more Heavies you get, the more you gain with mixed mode. If you're all Mediums (i.e. can come in with 2.5nm seperation and leave with about a 6.000ft speration) it doesn't really matter much.

Respectfully, if you've ever attempted to have departures in between arrivals when the arrivals are 2.5 NM apart on final, the only way you get more throughput is by counting the go around as an arrival and departure, which it would be.

There is physically no way that with airline or large corporate aircraft an arrival can cross the threshold, roll out and exit which takes lets say 45 seconds to clear (typical)....the departure is then cleared for takeoff which takes another 45 seconds (typical)....and the second arrival is traveling at 140 KTS over the ground speed (typical), the second aircraft reaches the landing runway threshold before the depature is airborne.....a separation error, so the controllers sends the arrival around.

If the average controllers is able to get around 45 departures airborne from a dedicated departure runway while the dedicated arrival runway is capable of around 40....for sake of arguement lets chop 5 off each...that still equals 75 ops for that those runway combinations, much higher than for a single runway used for arrivals/departures.
  

[Edited 2007-03-31 17:44:53]


Any views shared are strictly my own and do not a represent those of any former employer.
User currently offlineFlexo From St. Helena, joined Mar 2007, 406 posts, RR: 0
Reply 9, posted (7 years 5 months 3 weeks 2 days 8 hours ago) and read 1955 times:

One more thing about DEN: Since this airport is so spread out and does not have intersecting runways, would it be ok from a safety standpoint to also use the runways 7R and / or 7L as dedicated departure runways if the winds allow it (let's say wind from 260)?
Operating these also doesn't seem to interfere with operating runways 26 and 25, if they and 25 are used for deparure only.


User currently offlineInnocuousFox From United States of America, joined Dec 2003, 2805 posts, RR: 14
Reply 10, posted (7 years 5 months 3 weeks 2 days 7 hours ago) and read 1943 times:

DEN airport diagram

DEN will often do just that. They can run a number of configurations there, but one common one is this:

Arrivals: 26, 19L (or R) and maybe 17L
Departures: 17R and 25

Flip it over for a north/east flow.



Dave Mark - Intrinsic Algorithm - Reducing the world to mathematical equations!
User currently offlineSailorOrion From Germany, joined Feb 2001, 2058 posts, RR: 6
Reply 11, posted (7 years 5 months 3 weeks 1 day 19 hours ago) and read 1912 times:

Quoting IAHFLYR (Reply 8):
Respectfully, if you've ever attempted to have departures in between arrivals when the arrivals are 2.5 NM apart on final, the only way you get more throughput is by counting the go around as an arrival and departure, which it would be.

Yes of course, with mixed mode, the gaps in the arrival stream must be bigger than 2.5nm. Sorry for not being clear.

SailorOrion


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