"Koopas Ly" wrote in message
m...
Just a quick question...

During a crosswind landing, for instance a left crosswind, you'd lower
the left, upwind wing to counter the right drift induced by the
crosswind.

You'd also use some right rudder to keep the nose straight and prevent
it from "weathervaning".

Is this "weathervaning effect" caused by your leftward relative motion
due to the left bank OR by the rightward crosswind ITSELF?
Personally, I think that the former applies. The rightward crosswind
only displaces the airplane to the right. Only the relative motion of
the airplane with respect to that airmass would induce the
weathervaning effect. I presume that the airplane does not know,
aerodynamically, of the left crosswind.

From the point of view of the aerodynamics, the only thing the airplane
"knows" is the sideslip angle. It doesn't matter if you perceive this as a
forward slip (nil wind, tracking 270, heading 280) or a side slip (S'ly wind
causing 10 knots right drift, tracking 270, heading 270). In both cases
there's a sideslip angle of 10 degrees.

Is the sideslip angle because of the left bank or the rightward (from the
left?) crosswind? Is my mousemat compressed because the mouse presses down
on it or because the table presses up on it? :-)

If there is a sideslip angle there is a yawing moment, because of the
lateral lift from the fin. You can counter this with rudder, or let the
airplane yaw at a rate that increases until the natural yaw damping moment
balances it, as it does in a turn if you don't use rudder.

Next thing I was wondering, which is related to the above: say you're
dead on centerline on landing, and all of a sudden a crosswind from
the left starts blowing. The effect would be that you should only be
displaced to the right of runway centerline. Your airplane nose would
still be parallel to the centerline. Do you agree?

No, not if you make no change in control inputs. You've introduced a
sideslip angle, so the airplane yaws.

Julian Scarfe