Originally Posted by
misd-agin
If you have any crab in equal to the amount of crosswind, day five degrees, the instant you reduce to 4.9 degrees with the wings level the plane will start to drift. And it increases at 4,8, 4.7, 4.6.... The decrabbing isn’t instantaneous. And your technique assumes you can also coordinate reaching touchdown point at the exact moment that you instantaneous go fly your crab angle to runway alignment. That’s impossible in real life. I’d love to see someone try that in 25 kt crosswinds. Wait a second...I have. It’s not pretty.
I am afraid your conclusion is not true. Decrabing is not done little by little but in one smooth application of downind rudder before touchdown. As correctly pointed out by pineteam during decrab the aircraft rotates around the vertical axis which is slightly ahead of the CG. That pushes the aircraft towards upwind. Also the inertia keeps the aircraft moving straight ahead. During this time the aircraft should touch down. During this yaw Flight control laws prevent upwind wing from rising. But if you have decrabbed high and keep floating then it will start drifting downwind and that will need to be corrected by banking upwind wing up to maximum of 5°. If it cannot be managed with five degrees then missed approach must be initiated.