Dynamic soaring works only when the glider is passing through a path of
changing wind velocity. In this way the glider can gain or loose
energy independent of it's own kinetic and potential energy (as in a
shear or wind gradient). For example on final approach into a 15 knot
headwind, we increase our approach speed because we know as we descend
through the wind shear, we will loose airspeed (energy) and might have
to put the nose down (giving up our potential energy to get kinetic) to
keep the glider flying. Indeed, if we think we are going to be short,
we "dive under the wind" and then bleed off our speed in the weaker
headwind closer to the ground. This is Dynamic soaring that we all
have done.

In order to continuously extract energy from wind gradients or shears
in a closed loop path, our upwind path must be different than our
downwind. For example, of the Albatross was able to "hang a 180"
and fly back along the exact same path to it's starting point, it
would loose exactly the same amount of energy it had gained. It claims
it's free energy from "the area inside the loop" of it's flight
path that contains a gradient.

From a practical perspective, wind gradients are hard to see/feel
unless we have some topology like the ground or a hill for reference,
and even then we are only inferring the boundaries and makeup of the
shear, rather than measuring it directly like airspeed. So even if the
theory works, how do we practice? for example, no matter how sensitive
our backside may be, finding and centering lift is a whole lot harder
without a vario.

Proposal #1
As pilots that want to take advantage of dynamic soaring, we need an
instrument that can measure the rate at which the glider is gaining or
loosing energy independent of the normal Newtonian exchanges of
kinetic, potential and frictional (drag) forces. Such an instrument
could be created based on predicted v.s. actual airspeed. It is
possible to accurately model the dynamic flight parameters of a given
glider such as velocity, rate of sink, angle of attack, etc. in still
air. If we pull back on the stick, increasing the angle of attack by 2
degrees, we can predict what the airspeed will be in 1 second, 5
seconds, 20 seconds, etc.

Now imagine we pull up into a wind shear. Two seconds later, our
airspeed is actually three knots higher than our model predicts. We
are gaining energy! The needle (and tone) in our new instrument starts
to rise. If the airspeed was five knots higher, the needle (tone)
would rise even further. It shows us the rate of energy absorption
through airspeed. Similarly it would show loss, just like a vario.

Of course we could locate convergence lines with this instrument as
well. Who knows, we might even get thermal information from the
ability to detect horizontal gusts.

Proposal #2
While it is possible to design and build this new instrument, and just
how to do it will make an interesting discussion in itself, it will
take some time to perfect it and get it into production. In the mean
time, we want to learn how to use it before we have it. Just like the
albatross has several different techniques for taking advantage of the
same surface shear conditions, there are probably many new ways that
have not been discovered at "full" scale to soar dynamically. What
is the best way to fly in wind gradients that run side to side, rather
than top to bottom? What is the best way to dynamically soar
orthogonal to the wind direction?

While our instrument is difficult to build in the real world, it's a
snap to create in a flight simulator where the glider is already fully
modeled. Lets build a virtual instrument and experiment by flying in
virtual shear using one of the excellent glider flight simulators on
the market. Anyone have an in with the programmers?

Food for a winter discussion,

Matt Herron (jr)