SESGDL
Topic Author
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Why Doesn't ATL Use Immediate Departures?

Sun Sep 03, 2006 1:41 pm

I've flown out of ATL three times in the past year, most recently this past Tuesday, and was wondering why immediate departures weren't being used on any of the occasions. Most recently, we left about 45 minutes late from the gate on my flight from ATL-MSP due to a malfunctioning lavatory, but sat in a line of about 25-30 planes on runway 26L, which took roughly 50 minutes. I was frustrated to see that planes would taxi into position and hold and then sit for 2-3 minutes before finally revving up and departing. My plane of course rolled onto the runway and immediately took off.  Yeah sure The weather was clear and with parallel runways I would've thought that ATL could have had immediate departures, or at least not have aircraft sit on the runway for as long as they did. Does anyone know why they don't?

Jeremy
 
vikkyvik
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RE: Why Doesn't ATL Use Immediate Departures?

Sun Sep 03, 2006 2:00 pm

Quoting SESGDL (Thread starter):
Does anyone know why they don't?

I don't know if this is the reason, but I believe departures have to be spaced by a certain distance (or time, I forget) due to wake turbulence from the previously departed aircraft.

~Vik
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onetogo
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RE: Why Doesn't ATL Use Immediate Departures?

Sun Sep 03, 2006 11:46 pm

Perhaps a combination of wake turbulence seperate (3 mins behind a heavy) and departure spacing and sequencing restrictions placed on the tower by the TRACON and/or the center.
 
IAHFLYR
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RE: Why Doesn't ATL Use Immediate Departures?

Mon Sep 04, 2006 12:06 am

Wake turb separation is applied using miles rather than minutes at most airports. So, that in itself if a large number of B752/3's or widebodies can account for some of the added delay in departures. Another reason may be due to an enroute restriction out a departure route or routes from ATL Center or a second tier center such as JAX etc.

Weather can be totally wonderful and restrictions get put in place simply due to volume or weather 200 miles down the road. If you get caught up in that line and no way out of it guess what, you're gonna site an wait till your number rolls up.

Yet another possible reason for the delay on some departures might have been for the RNAV departures that are creating an issue if the crew has not loaded the correct runway into the FMC or the waypoints aren't verified. The tower might be staggering the departures slightly so they don't have any more of the crossovers that have occurred off the end of the runway as the first waypoint on the SID is the active waypoint and the south runway departure makes a turn to the north runway waypoint and vice versa which has been taking place too many times....all ya need is to add some smoke and you've got the total airshow!  Smile Simply too many reasons for departures to not be rolling one after the other.
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xjramper
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RE: Why Doesn't ATL Use Immediate Departures?

Mon Sep 04, 2006 2:19 am

How was the weather? When in IMC conditions, when there is a plane landing on one runway they don't depart another aircraft, just in case they have to do a go around. Gives the pilots and ATC a little more breathing room.

XJR
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SESGDL
Topic Author
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RE: Why Doesn't ATL Use Immediate Departures?

Mon Sep 04, 2006 3:07 am

Thanks for the responses. Answers my question perfectly!

Jeremy
 
twal1011727
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RE: Why Doesn't ATL Use Immediate Departures?

Mon Sep 04, 2006 9:36 pm

At ATL - Try being in an RJ or MD88 taking off behind 25 int'l B777/B767s.
and the ever wake turbulent B757. I was in an MD88 landing behind a B767 and went through their wake..rolled us 40 degrees and bounced us around for all of about 1 second then smoothed out. Quite fun....

KD
 
IAHFLYR
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RE: Why Doesn't ATL Use Immediate Departures?

Mon Sep 04, 2006 10:20 pm

Quoting TWAL1011727 (Reply 6):
At ATL - Try being in an RJ or MD88 taking off behind 25 int'l B777/B767s.
and the ever wake turbulent B757. I was in an MD88 landing behind a B767 and went through their wake..

At any airport.....thus wake turbulence separation standards. A non wake turbulence separation required airplane is the B738 and B739's.....wonder if those are being looked at in some dark room for added separation?
Any views shared are strictly my own and do not a represent those of any former employer.
 
vikkyvik
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RE: Why Doesn't ATL Use Immediate Departures?

Tue Sep 05, 2006 12:02 am

Quoting Iahflyr (Reply 7):
A non wake turbulence separation required airplane is the B738 and B739's

Meaning there's no separation requirement for takeoff behind a 738 or 739?

~Vik
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
learpilot
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RE: Why Doesn't ATL Use Immediate Departures?

Tue Sep 05, 2006 2:44 am

Also, in ATL they land on the outer runways and depart from the inner runways. They have to give the guys who landed a chance to cross the departure runway so they can taxi to the gate. A lot of the time you'll be sitting in position on the departure runway and see 5 aircraft that have landed cross in front of you.
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IAHFLYR
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RE: Why Doesn't ATL Use Immediate Departures?

Tue Sep 05, 2006 7:20 am

Quoting Vikkyvik (Reply 8):
Meaning there's no separation requirement for takeoff behind a 738 or 739?

Exactly...unless a small taking off from an intersection, nor is there any for arrivals again unless a small is following on an approach and is not on a visual following the Boeing jet. So put a string of Boeings on final behind an 800 or 900 all that is needed is 3 miles or inside 10 from the runway if able to used reduced separation on final, you go down to 2.5 behind........departure rock and roll baby!
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Pope
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RE: Why Doesn't ATL Use Immediate Departures?

Sat Sep 16, 2006 3:11 am

The rapid fire pace of ATL ATC has them issuing position and hold clearances before the aircraft rolling has even departed the runway - that way there's always someone ready to go as soon as ATC or spacing issues allow the plane to be released. Add the mix of various aircraft types from ATR's (and until relatively recently EMB120's) to 747's and everything in between and it's just impossible to "launch" everyone without a hold if for nothing else other than spacing.

But the notion that they always have you position and hold isn't the case. Late at night (I'm a FF on the last ATR flight from ATL to GNV) you usually get cleared directly for takeoff without even holding short of the runway.

But even at busy times controllers do some interesting things to keep the traffic moving efficiently whenever possible. It was a 1730 departure on an ATR72 and we were taxing from D concourse via Mike to 27R when all of a sudden we crossed 27R at Kilo then taxied via November to Juliet and took off from 27L. There must have been a break in the arrivals because we had to have been something like #15 for takeoff from 27R. I'm sure that move saved us at least 25 minutes.

A couple of weeks before that, we were headed for a 9L departure via Mike when we were cleared via Tango and November to 9R. Again it saved us a ton of time during rush hour.

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