naruto38700
Topic Author
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### Crosswind Runway In Relation To Primary Runway

Hi everyone, this is about the project I am doing now. We are asked to design an airport with relevant details on the runways.

So here is my question, I wonder if crosswind runways are always perpendicular to the primary runway, or are they just oriented to the prevailing crosswind?

One more thing, according to the question paper, only one runway is needed to satisfy current traffic demand. However, prevailing wind is at 050° while Crosswind is at 120°, so is it safe for me to assume that a crosswind runway will be needed?

Thanks!

vikkyvik
Posts: 12051
Joined: Thu Jul 31, 2003 1:58 pm

### RE: Crosswind Runway In Relation To Primary Runway

 Quoting naruto38700 (Thread starter): So here is my question, I wonder if crosswind runways are always perpendicular to the primary runway, or are they just oriented to the prevailing crosswind?

My suggestion would be to go look at airport diagrams. Many US ones are available here:

www.airnav.com

You'll find that runways have all sorts of orientations, and most of them aren't exactly perpendicular.

 Quoting naruto38700 (Thread starter):However, prevailing wind is at 050° while Crosswind is at 120°, so is it safe for me to assume that a crosswind runway will be needed?

That's not enough information to make that determination. If the crosswind only gets up to, say 2 or 3 knots, then I'd say no, you don't need it. But there are more factors that would have to be considered.
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tdscanuck
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### RE: Crosswind Runway In Relation To Primary Runway

 Quoting naruto38700 (Thread starter):So here is my question, I wonder if crosswind runways are always perpendicular to the primary runway, or are they just oriented to the prevailing crosswind?

Exactly perpendicular is relatively rare. If you're going to go to all the trouble to make a crosswind runway, you might as well align to the prevailing crosswind. Especially since exactly perpendicular takes up the most space so you only want to do it if you really have to.

 Quoting naruto38700 (Thread starter):However, prevailing wind is at 050° while Crosswind is at 120°, so is it safe for me to assume that a crosswind runway will be needed?

As noted, it's going to depend a lot on the wind. But also on other weather factors (do you have enough capacity on your single even if the weather is bad? could you do simultaneous operations on the crossed runways?). And what shape is your land plot? Who's under the approach and departure ends of each runway? This all factors in.

Tom.

Mir
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Joined: Mon Jan 05, 2004 3:55 am

### RE: Crosswind Runway In Relation To Primary Runway

 Quoting naruto38700 (Thread starter):So here is my question, I wonder if crosswind runways are always perpendicular to the primary runway, or are they just oriented to the prevailing crosswind?

It really depends. Normally, you would have it aligned with the prevailing crosswind to the extent practical. But if you're going to start talking about using it not only as a crosswind runway but as a second usable runway (i.e. have two runways going at the same time to improve traffic flow), then a perpendicular runway has some advantages.

-Mir
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rfields5421
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Joined: Thu Jul 19, 2007 12:45 am

### RE: Crosswind Runway In Relation To Primary Runway

A great many runways / airports around the world have runways based on the early history. The runways at Heathrow evolved from three runway pairs to the current two runways.

Chicago's O'Hare was a mess of runways for different wind conditions - slowly being converted to a predominant wind direction runway setup.

Airports like JFK, LGA, EWR, PHL all have physical geography constraints which limited the way the runways could be built. SAN is an example of successfully combining wind direction and physical geography to allow a busy airport to operate near the city center. It just has absolutely no possibility of growth, or alternate operation if winds are bad.

 Quoting tdscanuck (Reply 2):Exactly perpendicular is relatively rare.

True, but back before WWII - perpendicular runways seemed to be a preference which make it common at many of the older airports - i.e. SFO, JFK, LGA, PHL.

The Army Air Corps built many training bases across the US, which the USAF later upgraded to jet bases with perpendicular runways, and 45 degree cross runways. Seemed to be a standard pattern many places, despite normal wind speeds and directions.

Perhaps a good example of modern wind directed airport design (even though the design is 50 years old) is DFW with a primary wind direction 5 runways, and an alternate pair usable most of the time, and occasionally the only usable runways in wind conditions like we had a couple weeks ago.

Or DEN - where the wind change possibilities must be extreme with four north/south runways and two east/west runways.

Starlionblue
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Joined: Fri Feb 27, 2004 9:54 pm

### RE: Crosswind Runway In Relation To Primary Runway

Another issue is the type of traffic. Modern airliners can handle way more crosswind than smaller aircraft, particularly GA planes. Compare KMCO, which services airliners, and KISM, which services primarily GA. They are quite close to each other, so wind conditions are close to each other. KISM has two runways at 90 degrees while KMCO has parallel ones. No way a Cessna 172 can handle 20 knots crosswind, something an airliner lands in without problems.

BTW for an airport with V-shaped runway layout, check out KGNV. http://155.178.201.160/d-tpp/1213/00973AD.PDF
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

JoeCanuck
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Joined: Mon Dec 19, 2005 3:30 am

### RE: Crosswind Runway In Relation To Primary Runway

YYC has two runways crosswind to the main north/south runway. They are both significantly shorter but since they are only in to airliners during severe crosswind situations, they don't have to be as long.

The crosswind runways also serve to keep smaller GA aircraft out of the landing and takeoff patterns used by the airlines. There is more than enough room for most smaller aircraft to stop short of the intersection.

That being said, crosswind ops seem to be a real pain sometimes, resulting in lots of holds and delays.

A larger version is available here;

http://www.gcmap.com/diagrams/pdf/CYYC.pdf
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LU9092
Posts: 106
Joined: Thu Oct 18, 2007 2:09 am

### RE: Crosswind Runway In Relation To Primary Runway

 Quoting rfields5421 (Reply 4):Or DEN - where the wind change possibilities must be extreme with four north/south runways and two east/west runways.

Having grown up in CO, I was somewhat surprised to learn that the prevailing wind in DEN is from the south, except for the month of April, where it is instead from the north. My impression from having lived there for nearly 30 years is that the typical case is light winds that allow any runway to be used. The most common high wind scenarios - and this is based only on my own observations - would be high, gusty downslope winds, mostly in winter and spring, and then straight line thunderstorm winds caused by downdrafts in the summer that can be from any (or all!) directions. Less common are the steady 10-15kt upslope winds from the east or southeast that tend to herald the arrival of wet, heavy snow from late winter through spring. If you notice a strong upslope from mid-July into August, keep your eye on the sky. Someone is likely to see serious flooding, as in Ft. Collins on July 26-27, 1997, or the Big Thompson River basin in 1976.

Bringing it back to perpendicular runways, DEN certainly has the space for them, and the fact that when there are crosswinds, they tend to be strong and gusty, makes that pair of east-west runways essential. I believe that DEN's master plan allows for two more parallel east-west runways and four additional north-south.

naruto38700
Topic Author
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Joined: Sat Dec 29, 2012 3:19 pm

### RE: Crosswind Runway In Relation To Primary Runway

 Quoting vikkyvik (Reply 1):My suggestion would be to go look at airport diagrams. Many US ones are available here: www.airnav.com

Thanks for giving me this website! We are also asked to draw the layout of the airport so this will be very helpful!

So I think I will be adding a crosswind runway oriented to 120°/300° since the prevailing crosswind is at 45 knots

DiamondFlyer
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### RE: Crosswind Runway In Relation To Primary Runway

 Quoting Starlionblue (Reply 5): No way a Cessna 172 can handle 20 knots crosswind, something an airliner lands in without problems.

Say what? A 172 can absolutely handle 20 knots of crosswind.

-DiamondFlyer

Starlionblue
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### RE: Crosswind Runway In Relation To Primary Runway

 Quoting DiamondFlyer (Reply 9):Quoting Starlionblue (Reply 5): No way a Cessna 172 can handle 20 knots crosswind, something an airliner lands in without problems. Say what? A 172 can absolutely handle 20 knots of crosswind.

Ok fair enough but it is well beyond the demonstrated max.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

naruto38700
Topic Author
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Joined: Sat Dec 29, 2012 3:19 pm

### RE: Crosswind Runway In Relation To Primary Runway

 Quoting JoeCanuck (Reply 6):The crosswind runways also serve to keep smaller GA aircraft out of the landing and takeoff patterns used by the airlines. There is more than enough room for most smaller aircraft to stop short of the intersection.

Hi, I understand you are saying that crosswind runways serve two purposes, both for airliners to take off and land when crosswind prevails, as well as for GA aircraft to operate under normal conditions.

But in the case of YYC, would it not be a problem if GA aircraft operate on crosswind runway while airliner operate of main runway at the same time? You know, since they intersect each other, would it not reduce the efficiency of both runways?

Starlionblue
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### RE: Crosswind Runway In Relation To Primary Runway

 Quoting naruto38700 (Reply 11):But in the case of YYC, would it not be a problem if GA aircraft operate on crosswind runway while airliner operate of main runway at the same time? You know, since they intersect each other, would it not reduce the efficiency of both runways?

I'll speculate that if you can get GA to use another runway you're increasing efficiency even if they intersect. Just the decrease in wake turbulence separation between airliners and smaller GA planes will save you a boatload of time.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

naruto38700
Topic Author
Posts: 7
Joined: Sat Dec 29, 2012 3:19 pm

### RE: Crosswind Runway In Relation To Primary Runway

 Quoting Starlionblue (Reply 12):I'll speculate that if you can get GA to use another runway you're increasing efficiency even if they intersect. Just the decrease in wake turbulence separation between airliners and smaller GA planes will save you a boatload of time.

Now that is very true! I failed to take the wake turbulence into consideration, especially since I will have A380 operating in my airport! Truly grateful for the answer, have a happy new year since we are in the same time zone :P

JoeCanuck
Posts: 4214
Joined: Mon Dec 19, 2005 3:30 am

### RE: Crosswind Runway In Relation To Primary Runway

 Quoting naruto38700 (Reply 11):But in the case of YYC, would it not be a problem if GA aircraft operate on crosswind runway while airliner operate of main runway at the same time? You know, since they intersect each other, would it not reduce the efficiency of both runways?

While ATC won't let 2 aircraft land or take off at the same time on intersecting runways, they don't need the same kind of spacing if everybody is one behind the other on the same runway.

Basically, ATC will give the planes time and space to execute a go-around in case of runway excursion. Everybody will know a crosswind runway is being used so everyone is ready to act if an incursion takes place. With proper spacing, time is allowed that even if the landing or taking off plane does cross the intersection, it will probably not be an issue. The plane just has to make it across the taxiway hashmarks to be clear of the main runway...which only takes a few seconds.

You also don't have the wake turbulence issues which are a large consideration to approach spacing.
What the...?

vikkyvik
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Joined: Thu Jul 31, 2003 1:58 pm

### RE: Crosswind Runway In Relation To Primary Runway

 Quoting JoeCanuck (Reply 14):Basically, ATC will give the planes time and space to execute a go-around in case of runway excursion. Everybody will know a crosswind runway is being used so everyone is ready to act if an incursion takes place. With proper spacing, time is allowed that even if the landing or taking off plane does cross the intersection, it will probably not be an issue. The plane just has to make it across the taxiway hashmarks to be clear of the main runway...which only takes a few seconds.

Or (at least in the US), they use LAHSO operations, if the pilots/airlines accept them.
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".

JoeCanuck
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Joined: Mon Dec 19, 2005 3:30 am

### RE: Crosswind Runway In Relation To Primary Runway

I've done that in a Cherokee at YYC. Even with this, they still have to stagger the crosswind flights since an incursion could happen despite best efforts...but you don't need anywhere near the gap that all using the same runway would.

It's a bit of an awkward system but when it's working right, it's better than a single runway.
What the...?

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### RE: Crosswind Runway In Relation To Primary Runway

 Quoting Starlionblue (Reply 10):Ok fair enough but it is well beyond the demonstrated max.

So...? And it isn't much beyond the demonstrated max just FYI.

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