X-wind calculation
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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?
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.
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.
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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 !
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 !
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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.
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.
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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...!
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...!
Originally Posted by captainpaddy
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...!
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
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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.
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.
Wunderbra
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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.
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.
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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 ...
(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 ...
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.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!