# Runways and wind

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I can't for the life of me figure this out. I'm not entirely sure what math is used. If I'm flying to an airport runway that has a runway of say 33 and 15 and the wind is say 240 at 15 knots, how do I figure out which runway I would use to land? Obsessively I'd probably take 33, but I'd like to know what math to use to figure it out for other runways.
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Basically you want to have as little crosswind component (and as much headwind component) as possible. There are 360Âº in a circle, and runways are numbered to the nearest 10Âº (rwy 33 is about 330Âº). So 330Âº - 240Âº = 90Âº giving you a direct crosswind. Thus, all else being equal, you can use either one.

But noise abatement, obstacles, and perhaps other factors may favor one or the other, depending on the airport. Basically you want the smallest crosswind component (in degrees). Of course with more than one piece of pavement (or grass) it's easier to find a smaller component.

Larry N.

As Skylab would say:

Remember: Aviation is NOT an exact Science!

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Hi CRJ.

In addition to what Larry said, which is entirely practically correct, for the theoretical purpose only, just an exercise, you can also use the Airport diagrams that have the exact / more accurate rwy direction listed on them i.e. KSNA rwy 20R is actually 195.8.

There is no real practical need for that much accuracy since you will not have the accuracy, and consistency of direction, from the wind monitors, and the wind itself, to get the accuracy to justify having to that, in practice / real life. In addition if you could get the precise data, practically a few degrees off, less than 10, it would not make that much difference, unless you have winds in category beyond the capacity that the acft can handle.

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just want to clarify that I know there are 360 degrees in a circle, I know the runway numbers indicate approximate mag heading and I know you want as little crosswind as possible.

I thought that I would minus the runway mag with the direction of the wind, but I wasn't sure.

So now based on what lnuss said, if I have a runway of 26-08 and the wind direction is 190 degrees that's 70 degrees for 26 and 110 for 08. So I'd take 26 as that's a lesser crosswind component?

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...

So now based on what lnuss said, if I have a runway of 26-08 and the wind direction is 190 degrees that's 70 degrees for 26 and 110 for 08. So I'd take 26 as that's a lesser crosswind component?

Correct.

Larry N.

As Skylab would say:

Remember: Aviation is NOT an exact Science!

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... if I have a runway of 26-08 and the wind direction is 190 degrees that's 70 degrees for 26 and 110 for 08. So I'd take 26 as that's a lesser crosswind component?

Hi Crj and everyone.

There are a few other things to consider, if you want to be exact, if you go for your written test for example.

1-Wind is given from a True direction, and the Rwys from a Magnetic / Compass, in US. The wind has to be adjusted / converted to Magnetic, by using the Variation for that area / runway. At KSFO that is 13.7 East, degrees, you can find that data on Charts and or Plates...

A memory recall is East is Least, West is Best, subtract East Variation from Wind True direction and you get your Magnetic, that now you can use.

2-If you calculate Crj's example given, assuming wind from Magnetic direction, you will find out that the Xwind component is the same, one is from the Right the other from the Left.

If all you want to find out is the Xwind direction the answer is, it is the same Xwind. The question now becomes what other factors you may want to take into account, do I want some head wind component during take off, typically yes, is the head wind component of any consequence, do I want to go in any specific direction of flight...

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WE use an inexpensive 'whizz wheel' from ASA to do our nav flights.

Much fun had by all, & it keeps us on our toes. (or use an app on your phone)

Robin

Cape Town, South Africa

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I was just asking this question to those that fly since I didn't know the real answer and it's for Sim related activities only. As much as I would love to fly both professionally and recreationally I currently can't due to the FAR's current rules. I have been diagnosed with a mental health issue and to top it off I have a some what green/red color blindness. Well, I can see red and green, but it depends on its saturation for lack of a better term. If I could take the test I'd have to do a signals test I think it's called. I've read you can only do that once. I fly fine in the Sim, but I know it's just a damn game and no where near real life. Especially from what I read in Plane & Pilot magazine.

At this point in my life the Sim is all I got. :(

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1-Wind is given from a True direction, and the Rwys from a Magnetic / Compass, in US. The wind has to be adjusted / converted to Magnetic, by using the Variation for that area / runway.

That depends on your source. A general rule is that if you hear the wind it's magnetic, and if you read it the wind is true. In other words, when the tower tells you the wind, it is magnetic, but if you're reading a weather report to make a flight plan then it's true.

Larry N.

As Skylab would say:

Remember: Aviation is NOT an exact Science!

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That depends on your source. A general rule is that if you hear the wind it's magnetic, and if you read it the wind is true. In other words, when the tower tells you the wind, it is magnetic, but if you're reading a weather report to make a flight plan then it's true.

Hi Larry.

When you plan a flight, before you take off, you have No access to Tower and or other spoken sources. The wind for all Planning calculations, are considered to be True, no confusion or debate, otherwise you are likely to fail your test.

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Hi Larry.

When you plan a flight, before you take off, you have No access to Tower and or other spoken sources. The wind for all Planning calculations, are considered to be True, no confusion or debate, otherwise you are likely to fail your test.

True, but CRJ was asking what runway to choose for landing, not how to plan with enroute winds or how to take a test, so he's most likely to get his wind information from ATIS or from the controller, either way being magnetic, so no correction for deviation is needed -- simplifies things for a pilot in flight. Mental math is much easier if you don't have that complication.

Larry N.

As Skylab would say:

Remember: Aviation is NOT an exact Science!

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From all my Siming I've learned there's a lot of math. Persoanlly, I'm math stupid and if I were flying for real I'd take a calculator and a few more for redundancy. LOL! I use my scientific all the time while I Sim.

I had this off brand graphing calc. with its own code, and I made an awesome password generator in that thing. I used it to create a password for my first E-mail account back in circa '99. LMAO! Ziplip was the E-mail service I used. Those were the days... Kids these days. They just can't appreciate that all too familiar dial-up sound of phase shift keying and a slow connection with slow loading webpages. I used to think I was "the bomb" when I had v92 and actually got full 33k.