Osoba and dynamic soaring...

I had the great fortune to listen to Gary Osoba talk at the Western Homebuilder's 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 MacCready's original speed ring idea.

While the decription sounds like the 'dolphin flying' which we're 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 (I've 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,

I don't have an email address for Joe Wurtz, but maybe someone out there can hook you two up. Joe is a fellow Cal Poly Aero and a really smart guy. Back in school he could do things with his R/C sailplane that were just amazing.

Stan Fisher

I, also, have heard Gary speak at the convention in Albuquerque and have a different understanding of dynamic soaring. It exploits (extracts energy from) horizontal wind gusts. This is done by pulling up in the gust, extracting the energy of the faster air by gaining altitude. After the gust passes you push over and increase speed until you encounter the next gust. There is no vertical motion to the air mass whatsoever. The net effect is you make forward progress without loosing any, or little, altitude. This technique works best using gliders with very light wing loading such as the Carbon Dragon.

It might be helpful to have instrumentation to detect these gusts. You see it on the ASI as a sudden increase in air speed with no input on the stick.

You already have the instrumentation. Any Total Energy Vario shows them all too well. See the article on our website. www.ozemail.com.au/~mborgelt I have kept the maths very simple on the site but I have derived the complete mathematical treatment for myself.

It would be very simple to use a differential transducer connected to pitot and static in place of the absolute transducer in our B40 vario and have a pure rate of change of energy due to horizontal gusts instrument. The averager would tell you how successful each gust encounter was.

Is there anywhere online where Gary has a description of the maths and physics of his dynamic soaring theory?

I can see that, flying into a horizontal gust from the front the rate of energy increase due to the gust is proportional to the TAS squared and if you fly through the accompanying rear gust at slower speed there will be a net gain of energy as the time spent in each situation is linearly proportional to TAS. The problem is to change the speed of the glider quickly enough which is why Gary's technique is very dynamic and why it also is easier with light low wing loading gliders.

Mike Borgelt

Borgelt Instruments

I have had many, many hours of first hand experience dynamic soaring with RC sailplanes. There are many different techniques to dynamic soaring. The method I use (Joe Wurts was the first to demonstrate this technique) can be best explained on my website. This method works for models, but no sane pilot would try it with a full scale ship. Go to http://members.tripod.com/douglasturner/id27.htm for the information. For any skeptics out there, I would be glad to demonstrate it to you.

Doug Turner 7B

Tom,

Gary sees this as an extension to his previous work in 'micro-lift' soaring as he's expounded upon over the previous years while flying the Carbon Dragon. Based on the limited information at hand (nobody has fully worked through all the math and physics, though Taras Kiceniuk has come the closest) it appears that only ships at the extreme lightweight end of the spectrum (the Carbon Dragon) and at the extreme heavy end of the spectrum (the Sigma) are able to do this. It is possible that this is the reason that RC sailplane guys have been doing it for years, they are way below the extreme low end of 'full' scale sailplanes.

I think the point Gary is trying to drive towards is to extract energy from the air where differential velocities exist. Direction is of little importance, vertical or horizontal. The important thing is to extract the energy from them. At low speeds the differential seems to work best in a lateral mode, and at high speeds it seems to work best in a vertical mode.

I wish I had the brain cells to put all the math together!

Al Bowers

Soar).

ANY glider can do this. I have done it at 6.4 lbs/sq ft wing loading in an AC-4. I've done this at 5 lb wing loading in an L-13. If I'm understanding the concept correctly, there are certain types of shear that work well with high speed and high wing loading, and vice versa. You have to tailor the maneuver to the shape of the shear and the specs of the glider.

I think Gary is close to being able to articulate some rules of thumb on how and when to use certain maneuvers given the conditions and sailplane. Several other folks have made some interesting stabs at this issue, but Gary Osoba is one of the more articulate and enthusiastic working on this new frontier.

Chad Moore