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Tailwind Landings DCA  
User currently offlineMagcheck From United States of America, joined Aug 2010, 33 posts, RR: 0
Posted (3 years 7 months 3 days 14 hours ago) and read 4450 times:

Listening to ATC tonight and was surprised to hear a few CRJ's landing on 33 (5,204 x 150). Wind 10009. Even for small jets I thought this was strange.

1.) Is this unusual?
2.) Is there a tailwind "limit" per se for certain aircraft/runways/conditions or do they just crunch the numbers and go with ground roll figures?
3.) Even if the math works out, why not go conservative and take Runway 1?

Thanks!

12 replies: All unread, jump to last
 
User currently offlineloggat From United States of America, joined Feb 2000, 666 posts, RR: 0
Reply 1, posted (3 years 7 months 3 days 13 hours ago) and read 4415 times:

1. Not unusual to use 33. That wind condition makes it less likely though.
2. Tailwind limit for many airliners is 10kts, regardless of runway length. A tailwind requires a higher rate of descent so the possibility of harder landings. It does not depend on specific runway configurations, you just have to crunch the landing performance numbers and add the pilot comfort factor and see how the numbers line up. If the data shows you need 3000' then you are only using 60 percent of the runway. For my aircraft (E170/E190) I wil generally land at flaps 5 on runway 1, and flaps full on runway 33 so I end up using the same percentage of the available runway.
3. Although it is more conservative to take runway 1, there are still different levels of conservatism. As long as runway 33 is deemed to be almost as safe as 1, then sometimes it is used for a shorter taxi and to assist the tower in able to get a higher departure rate.



There are 3 types of people in this world, those that can count, and those that can't.
User currently offlineGoBoeing From United States of America, joined Jun 2000, 2706 posts, RR: 15
Reply 2, posted (3 years 7 months 3 days 13 hours ago) and read 4410 times:

Quoting Magcheck (Thread starter):

1.) Is this unusual?

Not really, but the runway is probably about the shortest you'd want it to be with a tailwind.

Quoting Magcheck (Thread starter):
2.) Is there a tailwind "limit" per se for certain aircraft/runways/conditions or do they just crunch the numbers and go with ground roll figures?

Each aircraft has a max tailwind component limitation. For the two jets I'm most familiar with, the EMB-135/145 and the EMB-170/175, it's 10 knots under normal conditions.

That's component though. In this instance, my rough mental math estimates the component would be about 6 knots.

As for the number crunching, there is a certain distance that is to be added for each knot of tailwind component if it gets that close to the actual runway length.

I can't recall off the top of my head what they are because I haven't looked them up in quite some time. To give you an idea, for the E-175 with a normal amount of landing fuel, and say 50-60 pax with their bags, we'll usually show a demonstrated stopping distance of 2200-2500 feet and minimum required of 3500ish for flaps full which we'd probably use for runway 33. So, a 6 knot tailwind component would probably not necessitate adding 2000 feet to what we need.

Quoting Magcheck (Thread starter):
3.) Even if the math works out, why not go conservative and take Runway 1?

It is always an option. It is nice to take the other if able to help ATC but if you can't do it then you can't do it.

It is a bit strange that some of nation's airports are based on not only VFR weather all day long but also ATC pulling every string to create gaps to work more planes in.

Visual 1 circle 33 is fun so I'd do it every time as long as it's safe.  


User currently offline1010101 From United States of America, joined Nov 2006, 5 posts, RR: 0
Reply 3, posted (3 years 6 months 2 weeks 5 days 3 hours ago) and read 3812 times:

Quoting loggat (Reply 1):
For my aircraft (E170/E190) I will generally land at flaps 5 on runway 1, and flaps full on runway 33 so I end up using the same percentage of the available runway.

I am curious why you wouldn't use full flaps for all landings. Is it something particular to your aircraft type?


User currently offlineajd1992 From , joined Dec 1969, posts, RR:
Reply 4, posted (3 years 6 months 2 weeks 4 days 22 hours ago) and read 3746 times:

Quoting 1010101 (Reply 3):
I am curious why you wouldn't use full flaps for all landings. Is it something particular to your aircraft type?

Sometimes it's a noise issue.

Less flaps = less thrust for the same speed, which = less noise. Does mean a slightly faster landing though.


User currently offlinedispatchguy From United States of America, joined Jan 2006, 1249 posts, RR: 2
Reply 5, posted (3 years 6 months 2 weeks 4 days 22 hours ago) and read 3743 times:

Quoting loggat (Reply 1):
2. Tailwind limit for many airliners is 10kts, regardless of runway length

The standard TW limit is always 10 kts, you can get an operations specification permitting up to 15kt tailwinds for specific aircraft and airports. For example, when I dispatched at Air Wisconsin, we had the 15kt tailwind authorization for one aircraft (N632AW) and at only one airport (Aspen CO).



Nobody screws you better than an airline job!
User currently offlineLemmy From United States of America, joined Dec 2004, 260 posts, RR: 0
Reply 6, posted (3 years 6 months 2 weeks 4 days 22 hours ago) and read 3722 times:

Quoting dispatchguy (Reply 5):
we had the 15kt tailwind authorization for one aircraft (N632AW)

Interesting. Why just one airframe and not a whole type? Was there something different about N632AW or was it just easier to get a specification that plane only?



I am a patient boy ...
User currently offlineloggat From United States of America, joined Feb 2000, 666 posts, RR: 0
Reply 7, posted (3 years 6 months 2 weeks 4 days 20 hours ago) and read 3693 times:

Quoting 1010101 (Reply 3):
I am curious why you wouldn't use full flaps for all landings. Is it something particular to your aircraft type?

There are at least a couple of reasons we don't use full flaps on all of our approaches. The biggest one is fuel conservation. The extra thrust required to overcome the increased drag from full flaps means more fuel burn, which over the course of many flights will add up. The only time we generally use full flaps would be on a short/slick runway.

The difference in Vref speeds for flaps 5 versus flaps full on my plane is about 10 kts. At our general landing weights, that is the difference between 120kts and 130kts. When you have ample runway for landing, then that 10kts doesn't really make a difference, so it goes back to the fuel burn argument.

The last reason is to do with crosswind landings. If there is a pretty stiff crosswind, the aircraft is much easier to control with a lower flap setting. Higher approach speeds from flaps 5 make the ailerons more reactive to the wind.

1. Fuel
2. Ample runway
3. Crosswinds



There are 3 types of people in this world, those that can count, and those that can't.
User currently offlinedispatchguy From United States of America, joined Jan 2006, 1249 posts, RR: 2
Reply 8, posted (3 years 6 months 2 weeks 2 days 16 hours ago) and read 3481 times:

Quoting Lemmy (Reply 6):
Was there something different about N632AW or was it just easier to get a specification that plane only?

It was a lighter airplane - the AFM for the heavier aircraft might not have permitted 15kt tailwind opns, and ASE is a very short runway to begin with...



Nobody screws you better than an airline job!
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 9, posted (3 years 6 months 2 weeks 1 day 21 hours ago) and read 3373 times:

Quoting dispatchguy (Reply 5):
The standard TW limit is always 10 kts, you can get an operations specification permitting up to 15kt tailwinds for specific aircraft and airports.

Is the 10kt limit coming from the Ops Spec? A 777 AFM gives 15kt limit, and the plane is capable of far more. I've done 30+kts...not particularly good for the brakes though.

Tom.


User currently offlinedispatchguy From United States of America, joined Jan 2006, 1249 posts, RR: 2
Reply 10, posted (3 years 6 months 2 weeks 22 hours ago) and read 3273 times:

Quoting tdscanuck (Reply 9):
Is the 10kt limit coming from the Ops Spec?

Looking at the FAA website, they actually did away with the OpSpecs paragraph that permitted it - so now, its just the AFM Chapter 1 limitations which apply....

Wow, the FAA doing away with a rule - never saw that coming!



Nobody screws you better than an airline job!
User currently offlineMSJYOP28Apilot From United States of America, joined Jul 2009, 228 posts, RR: 1
Reply 11, posted (3 years 6 months 2 weeks 13 hours ago) and read 3194 times:

My airline doesnt allow any tailwind on landings on runway 33 at DCA. No wet runways and captain only doing the landing. As a dispatcher, I have to approve them to land on runway 33.

Company tailwind limit though is standard 10 knots with no tailwind for winter airports with contamination on the runways plus for runways that are below a certain standard.


User currently offlinerwessel From United States of America, joined Jan 2007, 2368 posts, RR: 2
Reply 12, posted (3 years 6 months 1 week 3 days 7 hours ago) and read 3017 times:
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Quoting dispatchguy (Reply 8):
and ASE is a very short runway to begin with...

Getting a thousand feet longer in the next few months (work just started).


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