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ATC Changing Traffic Patterns At Airports  
User currently offlineSpeedbirdHeavy From United States of America, joined Jan 2004, 427 posts, RR: 0
Posted (10 years 5 months 1 week 6 days ago) and read 2109 times:

Since I live near KPHX, I see the airport being turned around quite often.

I've always been interested to know about the process. Who actually makes the call to do it and under what conditions? Here at PHX, it is pretty consistent as to which direction the traffic is flowing and what runways are in use at certain times of the day. Sometimes they differ though.

I'm sure there is a method to this whole process. It certainly can't be instantaneous either. Aircraft have to be re-routed in the air, as well as, on the ground. So, there must be some lead time.

I imagine that it can be quite dangerous during the period where the last flights are departing in the same direction that other flights are beginning their approach.

Any details would be most appreciated. Especially from you ATC guys.



China Airlines...Come fry with us!
15 replies: All unread, jump to last
 
User currently offlineTimz From United States of America, joined Sep 1999, 6822 posts, RR: 7
Reply 1, posted (10 years 5 months 1 week 6 days ago) and read 2086 times:

"I imagine that it can be quite dangerous during the period where the last flights are departing in the same direction that other flights are beginning their approach."

Why?


User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 2, posted (10 years 5 months 1 week 5 days 23 hours ago) and read 2078 times:

The process is known informally as "turning the airport around" and it's not all that big a deal, and certainly not dangerous...

The big driver in this are the surface winds. At PHX, the day usually starts with winds favoring use of 08 and 07L/R, but later in the laternoon, the winds swing to favor 26 and 25L/R. The max tailwind most airliners can handle is 10 knots, so when the winds start heading that way, they'll turn it around.

For aircraft on the ground, the aircraft lined up for departure will play -follow-the-leader and all taxi to the opposite end of the runway from where they were.

For aircraft in the air, they will either get additional vectors to approach the new runway in use, or depending upon traffic density, may have to circle in holding patterns for 5-10 minutes until the new flows of aircraft to the new runway in use can be established.

..Ain't no big thang....


User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 3, posted (10 years 5 months 1 week 5 days 23 hours ago) and read 2070 times:

>>>"I imagine that it can be quite dangerous during the period where the last flights are departing in the same direction that other flights are beginning their approach."

..and to add to Timz's response, ATC won't start arrivals to the new runway until the last departure off the old is well out of the way. Putting aircraft nose-to-nose can be quite problematic due to the high closure speeds and minimal cross-section to sight another aircraft, and ATC knows that...



User currently offlineCoa764 From United States of America, joined Feb 2004, 328 posts, RR: 3
Reply 4, posted (10 years 5 months 1 week 5 days 23 hours ago) and read 2068 times:


Tracon controls the airport configuration and winds/weather are what drive the it. I believe PHX is optimal on the west configuration but one of the problems they can run into is that they need 5000 feet for the freeway visual approach. If your ceiling drops below that and the ILS is needed things start to slow down.

Since I am not that familiar with PHX I will use IAH for an example. The optimal configuration for the airport is dept 15L/R and landing 26R/27. If, like today, the winds are out of the southwest 130 at 15 kts that gives us a tail wind on landing. I90 (IAH Tracon) will turn the field around to an east config landing 8L/09 and still dept 15L/R. It is not really dangerous since anyone on approach will land and the rest of the aircraft will be held and/or vectored around to the new approach fix. In the case of IAH if the field is turned the depts are not usually effected but at PHX they have to go from landing/departing west to landing/departing east so the aircraft on the ground have to be turned as well.

The other issue is the acceptance rate. IAH on an optimal configuration is 88 aircraft and hour vs. today on the east configuration with 60 aircraft and hour. When the arrival rate drops you can get arrival delays in the form of airborne holding and/or ground stops. If it is going to be a prolonged event that will effect traffic over multiple hours then you can run into a ground delay program.

So field configuration plays an important role in the amount of flights that can both depart and land in any given hour. If they day is VFR-severe clear with calm winds you have no delays but if and afternoon thunderstorm parks right over the approach end of the runway or the winds pick up and shift forcing and the airport into a less than optimal configuration expect delays until he event dissipates..

Hope that helps..  Big thumbs up



Please oh please Mr Moderator Nazi, dont delete my thread.
User currently offlineSpeedbirdHeavy From United States of America, joined Jan 2004, 427 posts, RR: 0
Reply 5, posted (10 years 5 months 1 week 5 days 18 hours ago) and read 2012 times:

I always thought the the Tower made the call to turn around an airport. Do they usually wait for a lull in arrivals to make the turn, or does it not really matter what the conditions are?

How come the arrival rate changes by configuration?

Also, at an airport like KIAH, how long does it usually take to turn the airport around? Let's just say from the time when the decision is made, to the first departure or arrival in the new configuration?

Many thanks for all the responses!



China Airlines...Come fry with us!
User currently offlineCoa764 From United States of America, joined Feb 2004, 328 posts, RR: 3
Reply 6, posted (10 years 5 months 1 week 5 days 18 hours ago) and read 2003 times:

Tracon controls the approaches and departures (roughly a 40 to 45 mile ring around the field) and they turn can come at anytime. If the winds shifts or and airmass develops that can cause the runway changes it is done pretty quick. At IAH the switch from a west to east configuration is seamless as long as departures are still off of the 15's. if they have to move the depts to the 33's that could take some time.

The reason for the rate reduction is that when not operating at optimal the airport cannot accept as many aircraft as when they are. IAH for example. on a west configuration landing 26/27 and dept the 15's you never have crossing traffic (88 ARR (Arrival Rate)). When landing 8/9 and departing the 15's Tracon has to stagger the arrivals to 09 because the arrival flow crosses the departing aircraft on 15L (60-64 ARR). All airports have their optimal and less than optimal configurations and depending on what runways they are using. EWR can be landing the 22's with the overflow to 11 and push a 50 ARR with VAPS (visual Approaches). Turn it around and land on the 04's with the overflow you can get around 46 an hour. Now if you loose the VAPS (3000 foot ceiling and 4 miles on the visibility) a 04/11 op will get you around a 38 ARR but if the winds force you off of 11 then your looking at a 35 rate under VFR and a 31 IFR. SO the runway configuration coupled with the winds and weather make a huge impact on the acceptance rate at any given airport.



Please oh please Mr Moderator Nazi, dont delete my thread.
User currently offlineSpeedbirdHeavy From United States of America, joined Jan 2004, 427 posts, RR: 0
Reply 7, posted (10 years 5 months 1 week 5 days 18 hours ago) and read 1999 times:

Okay, I understand what you're saying about IAH, but at PHX, the runways run from east to west, with no intersecting. Am I to assume that there is no less than optimal configuration for the airport, since it is pretty much the same no matter what direction the arrivals and departures are?


China Airlines...Come fry with us!
User currently offlineCoa764 From United States of America, joined Feb 2004, 328 posts, RR: 3
Reply 8, posted (10 years 5 months 1 week 5 days 17 hours ago) and read 1993 times:

I believe in PHX that it is more about being able to use VAPS (5000/5) rather than runway configuration. When your ceiling starts to drop below the 5000 mark the tower cannot maintain visual separation on final which slows things down considerably. Great thing about PHX is that monsoon season and dust storms aside it is usually VFR there.


Please oh please Mr Moderator Nazi, dont delete my thread.
User currently offlineSocalatc From United States of America, joined Jan 2004, 527 posts, RR: 1
Reply 9, posted (10 years 5 months 1 week 5 days 17 hours ago) and read 1982 times:

TRACON Has nothing to do with when the airport will switch the pattern, its all the tower. We call the TRACON and let them know were switching and they do their part. Its a pretty painless process, pilots really hate it though when they are #1 and then we tell them they are going down to the other end of the airport, but we have to make sure pilots know who the boss is, right??

User currently offlineCoa764 From United States of America, joined Feb 2004, 328 posts, RR: 3
Reply 10, posted (10 years 5 months 1 week 5 days 16 hours ago) and read 1980 times:

I stand corrected on that note! I mostly communicate with the ATCSCC, Centers and Tracons while going through the local ramp towers to communicate with the towers.


Please oh please Mr Moderator Nazi, dont delete my thread.
User currently offlineSilver1SWA From United States of America, joined Mar 2004, 4783 posts, RR: 26
Reply 11, posted (10 years 5 months 1 week 5 days 4 hours ago) and read 1911 times:
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If I am wrong here, somebody please correct me...

I heard that at KSJC, they cannot switch from 30L/R operations to 12L/R until SFO is turned around as well. Is this true? And if so, I would imagine in that situation SJCs tower does not make the official call.



ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
User currently offlineCorey07850 From United States of America, joined Feb 2004, 2527 posts, RR: 5
Reply 12, posted (10 years 5 months 1 week 5 days 2 hours ago) and read 1883 times:

Silver1SWA,

I can't confirm or deny that because I am not familiar, but airports generally do communicate with each other if they are going to be switching runways in order to coordinate traffic.

Here in DAB, if ATC wishes to swap runways they will coordinate with MCO ATC to work it out.


User currently offlineTimz From United States of America, joined Sep 1999, 6822 posts, RR: 7
Reply 13, posted (10 years 5 months 1 week 5 days 1 hour ago) and read 1871 times:

"I heard that at KSJC, they cannot switch from 30L/R operations to 12L/R until SFO is turned around as well."

You picked a good day to ask that. If you look at http://www4.passur.com/sjc.html for around 0805 this morning (25 March) you'll see aircraft approaching the 28s at SFO while SJC is using 12. Oakland was using 11, but don't know whether SFO was departing the 28s or the 1s (probably 28?).


User currently offlineN1641 From United States of America, joined May 2000, 220 posts, RR: 0
Reply 14, posted (10 years 5 months 1 week 4 days 20 hours ago) and read 1833 times:

towers owns the runways, TRACON has been known to suggest a runway change though. I work at a slow USAF tower and we try to change them at a convenient time based on the traffic situation, example... ok the last ones down lets switch now... or after the C-141 in the IFR pattern departs turn the runway around and they get to come back in the other way. I bet changing the runway at any busy facility would be a pain. As for coordination, approach is the most important to tell obviously, call base ops, tell weather because they control the wind sensors, tell the fire dept.

User currently offlineWillo From United Kingdom, joined Dec 2003, 1352 posts, RR: 12
Reply 15, posted (10 years 5 months 1 week 4 days 9 hours ago) and read 1792 times:

"I heard that at KSJC, they cannot switch from 30L/R operations to 12L/R until SFO is turned around as well."

the same with LHR and LGW (and probably LTN/LCY/STN - I can't hear the on ATC from where I live) as they are all pretty close and have sids feeding to similar points.


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