Seem to remeber this from an SFC instructor in the early nineties. It is for approximate , quick guide to x-wind component.
Landing runway 27 , surface wind 300/20....wind 30 degrees off nose then take the next two figures down from 3( from the 30 degree bit) , ie 2 and 1. 1/2 OF 20 KNOTS EQUALS 10KTS X-wind comp.
Again landing runway 27, surface wind 320/30 , this time 50 degrees off nose then , 5, 4,3. 3/4 of 30 equals approx 22.5 knots or 22 knots for rough estimate.
Obviously only a rough rule but quite quick to establish if within limits!
Hope this is useful.
