Weather and ground effect

"Andrew Sarangan" wrote in message
. 158...
"Maule Driver" wrote in
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"Paul Tomblin" wrote in message
What you're calling "ground effect" is actually the zone where the
wind is in the "boundary layer". Right at the bottom, turbulent air
will hit the gound and "stick", then each successive "layer" of air
above it will slow down a bit relative to the one below it, but also
stop moving across the layers. So near the ground, you get lower
wind speeds but also more laminar flow.

That 'boundary layer' effect which includes 'wind gradient' is also
what allows one to land in seemingly impossible xwinds. I've now
twice experienced x-winds too high to maintain a proper slip (wing
low, fuselage aligned) during final but once within a wingspan or so
of the ground, the xwind is reduced just enough to let me 'assume the
position'.

Which is one of the reasons I teach transitioning to the slip in the
flare rather than before. At 200agl you may not have enough rudder to
maintain runway alignment, but it may be just fine once you get down into
the flare.



Boundary layers are tiny.
Close to the ground the vertical component of air movement is constrained.
Maintain coordinated flight until the flare; then slip.
Keep the momentum vector nailed down the centerline.
That keeps you going straight in the transition to slip in the flare.
Use the correct airspeed for your craft; no more, no less.
Blue skies.
H.
CP AS&MEL IA