Re: [RCSE] Wind comments

[Mike Smith]

That is known in the soaring community as wind gradient.  This can also 
cause a nice looking approach at what would appear to be the perfect 
airspeed, to end either short of target due to the airspeed suddenly 
dropping off, or worse, a stall close to the ground.  Most of us notice 
this happening only after we touch down short of the spot.  We can be heard 
mumbling something about using too darn much flap  ;^)

Mike

At 09:04 AM 11/24/2004, John Erickson wrote:
Once everyone has found the wind gauge...it's interesting to learn about
ground effect.  We had a cross country event out in Lancaster.  The wind was
blowing at a moderate clip.  If you held the wind meter about 4' off the
ground it was reading 8-10 mph.
Joe W. then took the meter and put it up to about 10' off the ground.  I
think he tacked it to a pole or something, I can't quite remember.  In any
case, the meter now registered 15-18 mph.
This made sense with what our planes were doing up in the air (read going
backwards).  This also shed light on hot landings with ballasted planes.
You're driving into the wind about 50' off the ground, you bring the plane
down to the deck and the speed goes up, much higher than anticipated.
JE
--
Erickson Architects
John R. Erickson, AIA
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