Most reasonable explanation and experienced in both weaker UK lift and
strong western US lift. In many cases, ASI response quicker than vario
response.

Frank


"John Galloway" wrote in message
...
It's called the Yates Effect and the mechanism described
by Yates in Gliding magazine in 1951 is basically an
expanded version of what Robin says. Derek Piggot
has an Appendix on the subject in Understanding Gliding.

The inverse is also the explanation for the more important
phenomenon (in terms of thermallling and final turn
stall/spin safety) of the loss of airspeed when we
hit sink

John Galloway

At 21:30 27 March 2005, Robin Birch wrote:
In message , Fred
writes
Just got asked this question, didn't have a quick and
easy answer. How
do you explain it?

I've always thought of it as a change in the lift drag
vector. If your
glider is flying in still air the lift drag vector
is pointing up and
towards the tail. If rising air is entered, which
effectively increases
the lift vector the new lift/drag vector points slightly
more forward
than previously. This reduces the effective drag and
the glider
accelerates until everything balances out again.

This may be total rubbish but it is the model I've
found easiest to
visualise.

Robin
--
Robin Birch