A glider in steady free flight is always descending through the air in
which it is flying. If you can fly in air that is going up as fast or
faster than the sink rate of the glider, then you can gain potential
height energy. Isn't that what soaring flight is all about?

Derek Copeland
(Qualified gliding instructor with Gold C and 3 Diamonds BTW)

At 22:07 18 March 2009, The Real Doctor wrote:
On 17 Mar, 19:04, Darryl Ramm wrote:

Say what? Gravitational potential energy *increases* not decreases as
the glider climbs.

Sorry, typo.

And that "store" is the transfer mechanism that allows the glider to
glide.

No it's not. The gravity force is necessary, but it's perfectly
possible to soar for extended periods and distances without adding to
or drawing from the potential energy store. It happens any time we fly
level - along a wavebar, running a ridge, following a cloud street.

There is no other mechanism. With no gravity, even with an
atmosphere (which would be difficult to arrange), your glider could
not glide.

You miss, as so many people do, the point. Because the force of
gravity is necessary for a glider to work, people assume that gravity
somehow "powers" the flight. Which it does not.

Guy's this has wandered into junior-high school level physics.

No, it has wandered into junior high school level misconceptions about
physics!

Here's another one for you. Does a glider turn (normally) by (a)
rolling (b) pitching (c) yawing or (d) other?


Ian