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Subject:Osoba and dynamic soaring...
From:Al Bowers
Date:Tue Sep 05 12:51:25 2000

I had the great fortune to listen to Gary Osoba talk at the Western
Homebuilders Workshop this weekend about his latest work on dynamic
soaring. I may be overstating the case, but I believe Gary (and Taras
Kiceniuk Jr) are onto something, perhaps as fundamentally challenging
as Paul MacCreadys original speed ring idea.

While the decription sounds like the "dolphin flying" which were
accustomed to, it is different for some radically different reasons.
Gary and Taras think that it is necessary to fly at very high speeds,
which rotates the lift vector very far forward. Drag is also rather
large, so the resultant of lift and drag opposes gravity. But when a
small vertical component of airt is encountered, the effect is to
rotate the lift vector further forward. At this time, Gary performs a
very strong pull, increasing G on the airframe to about 2. As soon as
the following sink is encountered, Gary perfoms a push to 0 G. the
theory from Taras says that sink should be countered with negative G,
but Gary feels that an error in timing would destroy any gains he has
made, while 0 G imposes no induced drag penalty (or minimizes the
total drag penalty is probably a better way to put that). Gary is
using this technique on the old Sigma open class variable geometry
sailplane that was modified by Professor Marsden.

Gary showed some data taken with an integrated GPS/barograph unit. In
the first segment, he flew at something over 120 mph, using his 2G
pull and 0G push technique. At the end of a 12 mile segment, he had
lost 1000 ft of altitude. So he stopped and thermalled up (as Gary
puts it, "thermalling is a waste of time"). Gary felt that perhaps he
had not rotated the lift vector far enough forward, so in the second
segment, he pushed his speed up to 183 mph. In this 16 mile run, he
GAINED altitude. But the maneuvering is VERY dynamic, the push/pulls
are coming every 14.4 seconds with altitude variations of 1000+ ft
everytime. Gary described the lift that day as very normal, with no
streeting or organization. The data was astounding.

Perhaps the old adage (Ive usually heard it credited to George
Moffat) of "fly straight ahead and climb" should be revised to "fly
straight a head, push, pull, and climb." If you get a chance to see
this talk, please do so.

Thinking about it, it requires a coupling of the airmass (total energy
vario, but without filtering), the sailplanes polar (at various G
levels), and the airspeed. Gary says that the math indicates an
optimum G level which rapidly exceeds the ability of the sailplane (or
pilot) to perform. But even with "moderate" 2G/0G technique gary is
flying seems to work. I could see where an LED light system operated
by those instruments and a microprocessor could be made to indicate
what G level should be pulled for every flight condition...

Al Bowers

Al Bowers

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