X-wind calculation
 

Given a wind and a runway direction calculate crosswind. I have always used the x-wind charts to do this, does anyone know a formula/rule of thumb to do this in your head?:ok:

Use the 'clock' method:

If angle between wind and RW is 15 deg - use 1/4 wind speed
If it's 20 deg - use 1/3
If it's 30 deg - use 1/2
If it's 40 deg - use 2/3
If it's 45 deg - use 3/4
If it's 60 deg or more - use all wind speed.

or using the figures from the last post and imagine the old analogue type wrist watch .

so if its 15' off runway use the 1/4 past position (15mins) so its a quarter of the dial/hour so quarter of the strength. 20' off use 20mins which is one third of the face/hour so a third of the strength. if its 45' off use the 45min position so thats 3/4 etc etc. anything over 60' just use full strength. much easier than having to use your brain to work it out !

so in summary - whatever the wind angle - use the same figure in minutes on the face of your watch and then its just the proportion of the minutes to the full hour ! even i can use this technique.

failing that ignore the wind shut your eyes and hope for the best !

I always used to tell my students every pilot in the world is born in 1975.
Why they ask me.

Now this is the reason:
Put the numbers vertical:
1
9
7
5

Now change the in

1,0 = 90 degrees
0,9 = 60 degrees
0,7 = 45 degrees
0,5 = 30 degrees.

For a 90 degrees x-wind take the wind speed x 1,0
For a 60 degrees x-wind take the wind speed x 0,9
Etc. etc. etc.

You can do a lot more with it if you turn it around, like calculating your groundspeed and drift correction. But that was not asked for.

I always used the sixths (6th's) rule!

10 deg off = 1/6 of total wind speed
20 deg " = 2/6 " " " "
30 deg " = 3/6 " " " "
40 deg " = 4/6 " " " "
50 deg " = 5/6 " " " "
60 deg or more = 6/6 " " " "

Easy peasy. Very similar to BEagles one actually...!

Only from a brit.... 6th´s... jeez

Another way is the following:
wind angle + 20 = %

Eg:

runway 27 = runway heading 270°
W/V 300°/20 kts
wind angle = 300 - 270 = 30
30 + 20 = 50% of the wind speed (20 kts), so the crosswind component is 10 kts.

A wind angle of 80° or more means that the full wind speed is the crosswind component, and wind angles of 0 - 10° = no crosswind.

I hope this helps.

Get yourself a flight computer. A CRP-5 or similar allows you to do all those calcs quickly and easily.

Alternatively it's a straight geometric relationship. Just take the sin of the angle between the wind and the heading, call this a.

Call the wind speed x

Now crosswind velocity is x.sina.

without my calculator or CR3 - ;)

(yes it is always in my flightbag together with MP3 and calculator)

I use the third rule.

Runway Track is 0 degrees

Wind from 0 to 30 deg left or right take 1/3 as crosswind.
Wind from 30 to 60 deg (30 to 60 deg) take 2/3 as crosswind
Wind from 60 to 90 deg take 3/3 or the full as crosswind.

Works and does not distract me ... :)

Too complicated to calculate in % or 1/6ths or 4 segments ... :\

http://windwiz.com/ :ok:

A cheap, $3.00 piece of plastic [Xw computer:) ], I hate excessive mental math:\ :ugh: :{ :confused: :* :(

See also, Holding Pattern Entry Computer :ok: :ok: :ok:





See Applicable Notams :\
rhov :)

BEagle - I love it, even I can work with this. Thanks so much

matt_hooks
 

And use the CoSine for the headwind.

.5, .7 & .9 of the wind for 30, 45 and 60 degrees respectively. It's close enough for government work and if you need it more accurate figures then it's probably outside limits!