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Author Topic: KDCA Runway 1 and 33 takeoff seperation?  (Read 6170 times)

Offline blaze

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KDCA Runway 1 and 33 takeoff seperation?
« on: October 06, 2008, 09:55:07 PM »
Hello,

I'm neither a pilot or ATC but an enthusiast.  I was over by the Jefferson Memorial hanging out and watching the takeoff's, which I'm pretty sure were Runway's 1 and 33.

What is the lateral separation between takeoffs? (not sure if that is the correct terminology)

For some reason I assumed it was 5 miles  but they did seem a little closer.  Gets pretty busy in the afternoon, which makes for great spotting.

Thanks for the information on a pretty basic question!



Offline KSYR-pjr

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Re: KDCA Runway 1 and 33 takeoff seperation?
« Reply #1 on: October 06, 2008, 10:19:01 PM »
For some reason I assumed it was 5 miles  but they did seem a little closer.  Gets pretty busy in the afternoon, which makes for great spotting.

From a small aircraft pilot's perspective, here's a dramatic example:  When I would fly out of Boston Logan (another busy class B airport) tower would clear my Bonanza single engine for takeoff behind a medium-sized jet (Airbus 320 type aircraft) with about one minute of separation, which is somewhere around 3 miles.   The caveat in this case was the common, "Caution wake turbulence" warning that followed the clearance.

I would speculate that 3 miles is more the norm for departure separation, assuming no largely mismatched aircraft are involved (a typical heavy such as a B747 in front of a twin prop engine commuter aircraft).

pilot221

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Re: KDCA Runway 1 and 33 takeoff seperation?
« Reply #2 on: October 06, 2008, 10:32:56 PM »
The question might seem basic but it is actually quite more complicated that you think. Without knowing their specific procedures I can give some basics on departures (initial departure separation)

If someone is departing runway 33, the aircraft departing runway 1 cannot start it's takeoff roll until the other aircraft is across the intersection and vice versa.

You need at least 15 degrees course divergence if you plan on putting the two aircraft within 3 miles. So, between 33 and 1, you have 40 degrees. They can both go straight out and right away you have the 15 degrees. They wouldn't let them go if they were on the same route obviously.

Most aircraft at DCA are "Category III" (not to be confused with weather...this is for same runway separation). So, if two are departing the same runway, the second one can technically start it's takeoff roll as soon as the first one is 6000 ft down the runway AND airborne...we as controllers do this...not the pilot. However, you can't send a 737 up the butt of a slower type...you still need either 15 degrees, 3 miles, or visual separation. (Yes, whether or not we can see from the tower determines what we can and can't do)

Those are just basics...within the rules you can get them pretty close working at a tower as this is just the INITIAL separation. It's fun too  :-D
There are other rules depending on runway configuration, how far the runways are apart from each other, whether or not they are staggered...etc. There's quite a bit to it.

Offline rpd

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Re: KDCA Runway 1 and 33 takeoff seperation?
« Reply #3 on: October 06, 2008, 10:40:36 PM »
They would be on the same route, following the Potomac river northbound.  Straight out from Rwy 1 goes directly into prohibited airspace (P-56).

I believe the tower uses visual separation with departures often at DCA>

pilot221

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Re: KDCA Runway 1 and 33 takeoff seperation?
« Reply #4 on: October 06, 2008, 10:42:59 PM »
From a small aircraft pilot's perspective, here's a dramatic example:  When I would fly out of Boston Logan (another busy class B airport) tower would clear my Bonanza single engine for takeoff behind a medium-sized jet (Airbus 320 type aircraft) with about one minute of separation, which is somewhere around 3 miles.   The caveat in this case was the common, "Caution wake turbulence" warning that followed the clearance.

I would speculate that 3 miles is more the norm for departure separation, assuming no largely mismatched aircraft are involved (a typical heavy such as a B747 in front of a twin prop engine commuter aircraft).

In that example you could be cleared for takeoff as soon as that Airbus was 6000 and airborne. You would never catch him and the 3 miles would exist before you were probably even airborne. Perfectly legal. There is no wake turbulence requirement for that.

The only wake turbulence delay you would have would be if a Heavy/B757 departed ahead of you. Then it's either 2 minutes (we'll assume you are departing full length) or mileage if radar is available.

pilot221

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Re: KDCA Runway 1 and 33 takeoff seperation?
« Reply #5 on: October 06, 2008, 10:46:24 PM »
They would be on the same route, following the Potomac river northbound.  Straight out from Rwy 1 goes directly into prohibited airspace (P-56).

I believe the tower uses visual separation with departures often at DCA>

Quite possible. The only catch to the visual separation is that you need to be talking to at least one of the aircraft involved (meaning they need to be on your frequency). You would also need a form of separation  before and after the visual was being applied.

So...Runway separation...visual separation...radar separation. Can't be any grey areas.

They might also use visual separation between the pilots..."Maintain visual separation...". Obviously they need to see each first.

I'm sure they have some sort of procedure but I was just giving the basics.
« Last Edit: October 06, 2008, 10:48:19 PM by pt9 »

Offline blaze

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Re: KDCA Runway 1 and 33 takeoff seperation?
« Reply #6 on: October 07, 2008, 09:00:42 PM »
I really appreciate the replies!  These are all things I will think about the next time I go spotting in the area (tomorrow).  I do wait for the 757 departures as they are pretty spectacular going over the Potomac.. 

Thanks again for the informative replies!!