"Andreas Maurer" wrote in message
...
On Thu, 30 Dec 2004 13:36:59 -0800, Eric Greenwell
wrote:

A Google search turned up laser airspeed sensors that, in concept, could
be used to measure L/D directly from the glider. Some of them were good
for the low speeds we need to measure sink rates. So, have one pointing
forward, one pointing down, divide the forward speed by the sink rate,
and ta-da! L/D. It wouldn't matter what the airmass was doing, since the
measurements are relative to the airmass.

This is exactly what is accomplished by today's L/D calculators that
use GPS speed and barometrical measured height loss over a given time.

No, it's not. That will give you the glide made good over the ground, but
it includes airmass movement.

It's confusing, because glider pilots tend to use glide angle and L/D
interchangeably.
I would suggest "glide angle" for the glide relative to the ground, and
"L/D" for the performance relative to the air.
To show you what I mean:
When I get into weak shear, my 1-26 may make a glide angle of 50:1. But its
L/D is more like 20:1


Tim Ward


Bye
Andreas