Quick way to calculate crosswind?

[bc2209]

I remember hearing my instructor say there is a fast way to calculate crosswind in your head but I can't remember what it was. Something like a 3 5 9 rule?

Anybody know a trick like this?

Going to be a little gusty tomorrow and I want to make sure I've got a way to figure this out if I have to divert because of strong crosswinds.

Thanks in advance.

 

[jtrain609]

I remember hearing my instructor say there is a fast way to calculate crosswind in your head but I can't remember what it was. Something like a 3 5 9 rule?

Anybody know a trick like this?

Going to be a little gusty tomorrow and I want to make sure I've got a way to figure this out if I have to divert because of strong crosswinds.

Thanks in advance.

I've always just gone around when I ran out of rudder? Does your FBO has a limit on crosswinds or something?

You could also just use an E6B. Or an electronic E6B. Or an E6B application on your phone.

 

[Shiftace]

Something about sine tables too....

 

[Old Dominion Flyer]

As I young learner I was told about a "Clock Rule". 60 degrees or more is like 60 minutes, the full hour, so all of it is crosswind. 45 degrees is 3/4 of the hour, so 3/4 of the wind is crosswind. 30 degrees is 1/2 of the hour, so half of the wind is crosswind. This method may be oversimplified, but it sure is quick.

In practical application, if you feel uncomfortable, divert.

 

[Shiftace]

A quick Google search found this..

http://www.pprune.org/archive/index.php/t-320182.html

 

[bc2209]

I've always just gone around when I ran out of rudder? Does your FBO has a limit on crosswinds or something?

You could also just use an E6B. Or an electronic E6B. Or an E6B application on your phone.

I'm starting to do a little time building. I figure if i took off and the winds shifted and it started gusting stronger I'd get close or over to the max demonstrated crosswind of the diamond 20.

As it looks from the forecast I might not be taking off anyways. Thanks for your input though.

 

[MoMatt]

30 degrees off the runway - 1/2 of it is crosswind
45 degrees off the runway - 2/3 of it is crosswind
60 degrees off the runway - 90% of it is crosswind

Remember those 3 as a pretty good estimate and anything in between is easy to approximate.

 

[CFI A&P]

There is something with sin, cosine or tangent... I can never remember which one and how to use it, like I said, I'm not smart so I just go with when the rudder bottoms out.

 

[drunkenbeagle]

I remember hearing my instructor say there is a fast way to calculate crosswind in your head but I can't remember what it was. Something like a 3 5 9 rule?

Anybody know a trick like this?

There isn't any trick, just trigonometry. It is the sine of the angle of the wind relative to the runway.

Assume 10kts:
sine(30)=0.5. 10x0.5 = 5kts
sine(45)=.74. .... 7.kts
sine(60) = .89 .... 9kts
sine(90)=1. 1x10 = 10kts

Basically, if it is windy, and more than 30 degrees off the centerline, it becomes a signicant factor.

 

[Zondaracer]

Drunkenbeagle beat me to it.

Conversely, if you want to figure out the headwind component then you use cosine.

 

[jtrain609]

I'm starting to do a little time building. I figure if i took off and the winds shifted and it started gusting stronger I'd get close or over to the max demonstrated crosswind of the diamond 20.

As it looks from the forecast I might not be taking off anyways. Thanks for your input though.

Whatever you do, always have an out. Know what the winds are forecasted to be, and if things go pear shaped, don't be afraid to pull the trigger and head to a runway that is more aligned with the wind, and know where that runway is.

I never had to do it as an instructor, but I always had a few other airports that were close by stuck in my head that would have worked as good wind alternates. If you run out of rudder, be ready with that backup plan, and don't be afraid to execute it if you don't feel comfortable.

 

[subpilot]

Degrees - percent(fraction)
10- 1/6
20-1/3
30-1/2
40-2/3
50-3/4
60+ - above 85%+

 

[auw2fly]

Quick one I use, is determine the difference in degrees between the runway and the wind. Put a decimal in front of that number and add 0.2. Multiply the wind speed by that number to determine the crosswind.

For example, winds 030 at 10 knots, landing runway 7. 0.4 + 0.2 = 0.6 x 10 = 6 knots crosswind.

 

[T/O w/FSII]

I just look around the glass for a little box with an arrow with a number next to it.

 

[hook_dupin]

I just look around the glass for a little box with an arrow with a number next to it.

Funny... I look for an orange flappy conical thing near the runway. Failing that, I can usually see a flag or two.

 

[ElihuSmails]

Even easier....figure out how many degrees it's off, and add 20.

30deg = 50 %
40deg = 60%
50deg = 70%, etc...

 

[USMCmech]

30 degrees off the runway - 1/2 of it is crosswind
45 degrees off the runway - 2/3 of it is crosswind
60 degrees off the runway - 90% of it is crosswind

Remember those 3 as a pretty good estimate and anything in between is easy to approximate.

That's what I teach.

Simple, easy to remember, and pretty accurate.

 

[Fly_Unity]

That's what I teach.

Simple, easy to remember, and pretty accurate.

Same here

 

[Markf64]

Even easier....figure out how many degrees it's off, and add 20.

30deg = 50 %
40deg = 60%
50deg = 70%, etc...

Pretty much what I teach as well. I also tell my students that assume anything greater than 60 deg is 100%.

 

[Landis]

That's what I teach.

Simple, easy to remember, and pretty accurate.

Pretty much the same for me. I just figured out the error on this and it's not too bad if you also advise the use of some common sense. Obviously a direct headwind doesn't have a 20% crosswind. A direct crosswind isn't 110%. Anything beyond 60° could probably be considered 100% for more accuracy.