When coming in to land it is often difficult to work out the cross wind component quickly. There are 2 quick methods I know to be able to do this and when you understand them choose the one that suits you best.
The first one is known as the clock code and with it you assume that any wind that is more than 60 degrees off the runway heading is a full strength cross wind. So if landing on say runway 27 which is 270 degrees from North, then if the wind direction is less than 210 or more than 330 degrees, whatever the strength is it is regarded as full cross wind. So if the wind is say 200 at 15 knots then it is a 15 knots cross wind.
Now to work out how much of a cross wind there is between these 60 degrees either side of the runway heading you imagine that the number of degrees off the heading are the numbers of minutes round a clock face. Then imagine how far round the clock face that is, and that proportion round the clock face is the proportion of the wind strength.
So if the wind is 20 degrees off the heading, say for example 290 at 30 knots, then 20 minutes is one third of the way round the clock face, so the cross wind component is one third of 30 knots which is 10 knots.
If the runway was 03 which is 030 degrees, and the wind was 070 at 20 knots, this is 40 degrees off, and 40 minutes round the clock face is nearly nearly threequarters of the way round the clock face so the cross wind is three quarters of 20 or 15 knots.
As wind constantly varies in strength and direction, then you do not need to be highly accurate with your calculation. If the wind is roughly 30 degrees off, it is half strength so roughly half the wind strength is the cross wind component. 45 degrees off is 3/4 of the strength of the wind and 60 degrees or more full strength.
I will describe another method in my next article. It is similar, but it can be used for diversion planning as well.
