Dolphin flying

maanantai 15. helmikuuta 2016 15.45.15 UTC+2 kirjoitti:

Read Brigliadori as he describes extended glide. MC is based on a a model of climb and glide that does not apply directly much of the time, especially with higher performance gliders.
UH

I have and have read Brigliadori. It's still challenge to prove MC theory invalid, it has been attempted many times. MC theory applies under cloudstreet, there is optimum speed for current lift or sink.

BTW Brigliadori has nonsense in some parts of the book. I would take everything with at least a grain of salt.

MacCready theory is perfectly valid for both thermal soaring and cloud-street dolphin flying as long as the assumptions under which the theory is valid hold. Since this is almost never, flying at an appropriate MacCready setting may not be optimum under any conditions!

Out west, you run the risk of flying into the ground when thermals are widely spaced and perhaps short-lived - hence the recommendation to slow as you get lower.

Under a solid cloud street, MacCready can give you good guidance overall, but goes out of the window if you have to fly fast in lift to stay out of cloud!

Mike

McR theory are correct in almost all conditions, could be that on the ridge with dynamic lift should other theories be used.

But with that said di I also have to say:
The master of McR theory will never outperform the master of finding good climbs and the master of finding the best route.
I spend very little time and energy in decisions on STF, I try to spend most of my time and energy to find the best route and to get the best climbs. And most important of all, avoid the bad climbs.

On Tuesday, February 16, 2016 at 8:46:08 AM UTC-5, Per Carlin wrote:
McR theory are correct in almost all conditions, could be that on the ridge with dynamic lift should other theories be used.

But with that said di I also have to say:
The master of McR theory will never outperform the master of finding good climbs and the master of finding the best route.
I spend very little time and energy in decisions on STF, I try to spend most of my time and energy to find the best route and to get the best climbs. And most important of all, avoid the bad climbs.

Yep- right and left is much more important than up and down.
UH

On Saturday, February 13, 2016 at 6:46:48 AM UTC+11, Jonathan St. Cloud wrote:
Was reading an article by Mike Borgelt that when flying through a thermal you will not circle in you should just fly the STF.

I have always slowed in such thermals, sometimes slowing to thermal speed while putting the thermal flaps. I do try to accelerate before I leave the lift. My thought being try to stay in the lift as long as possible while still moving forward, sometimes even s-turning to stay in large thermal but still moving down the course line.

Would appreciate any comments, critique, thoughts...

The simple answer is to suck it and see, as it depends
When encountering lift, note the altimeter reading, then try any of the following: slowing down a little, a gentle pullup, a vigorous pullup and S-turn.

Could any of you shed some light on use of flaps while dolphin flying? I.e., in my DG-400, cruising at 70 - 75 knots with -4 degrees flaps, if I fly under a cloud and want to maximize the climb without thermalling, what is the best approach in terms of shifting gears with the flaps? I assume this is dependent on many different factors, but is there a general consensus about whether or not to down-shift to 0 degrees or positive (thermalling settings) flaps when flying straight?

On Sunday, February 28, 2016 at 7:54:18 AM UTC-7, Paul Villinski wrote:
Could any of you shed some light on use of flaps while dolphin flying? I.e., in my DG-400, cruising at 70 - 75 knots with -4 degrees flaps, if I fly under a cloud and want to maximize the climb without thermalling, what is the best approach in terms of shifting gears with the flaps? I assume this is dependent on many different factors, but is there a general consensus about whether or not to down-shift to 0 degrees or positive (thermalling settings) flaps when flying straight?

My answer to this flap question will not agree with the intuition of some flyers -- here is the truth on the matter according to GW:

Flap optimization is not about airspeed; it is about angle of attack. If you are going to slow down, the time to lower the flaps is when you make that decision and start pulling the stick back increasing AOA. Conversely, when you speed up, best to raise the flaps as you begin to push.

However, there is an important caveat to this. Most gliders have a structural speed limit for positive flaps. Despite what may be performance optimal, one must never overspeed the flaps.

Should someone express a counter opinion (likely), please do not misinterpret a lack of further reply on my part.

Years ago I talked to Wil Schuemann about the system he installed in his modified ASW 12. The stick had a detent for the center position and he used it primarily for aileron control. Pitch control was almost exclusively using the flap lever except for takeoff, tow, landing, etc.

I didn't install a detent in my LS-3 but because my glider had no detents in the flap drive as it came from the factory, I started using the flaps somewhat as Wil did. As he had assured me, it was a wonderfully smooth way to fly. Pull ups were slower than I wanted in those days of dramatic zoomies so I would "help" the process along with a quick pull on the stick as I entered a thermal at cruising speed. But at the top, instead of pushing over, I'd use the flap lever to bring the nose down smoothly, than bank and snap the flaps down for thermaling. I used the stick normally to thermal because the airplane reacted faster although I wonder now if I could have benefited there, too. When I was ready to exit, I'd use the flaps to lower the nose and accelerate.

The caveat was that this worked best if the glider was set up so the stick was in the same position for slow and higher speed flight. At Wil's advice, I measured the distance between the instrument panel and the top of the stick in straight flight at min sink and again at cruising speed (defined as the lowest speed for which I would use full negative flaps) and found that with my aft CG position, it was spot on.

I'm not saying this is the best way to fly. But it might be worth experimenting with. One caution as a layman: be careful about getting too slow with the flaps in negative position. The fuselage will be rather nose high and if you were to lower the flaps quickly, the angle of attack would increase just as quickly. If you stall in that position, the wing wake could be higher than the tail, which is a nasty prescription for "deep stall." I know a pilot who apparently did just this, entered what sounded like deep stall (stable, uncontrollable, nose-high, very high rate of descent, with no ability to lower the nose) and was lucky to escape about the time he was thinking about bailing out.

Chip Bearden

Can anyone point me towards literature on this subject?
I wonder if anyone has done simulations, calculating the cost of those 6.5G pulls for example.

On Tuesday, March 1, 2016 at 3:07:03 PM UTC-5, wrote:
Can anyone point me towards literature on this subject?
I wonder if anyone has done simulations, calculating the cost of those 6.5G pulls for example.

Wil Schuemann wrote an article for Soaring Symposium back in the late 60s called "The Price You Pay for Flying McCready Speeds". He did a monumental amount of calculations comparing dophin technique pulling and pushing to match the STF according to McCready vs flying simply at two selected airspeeds. Over a cross country flight, choosing to fly at the two selected speeds equated to a much better flight in terms of speed achieved. I once had a discussion with a world class pilot who stated that the drag incurred by pulling and pushing the stick is much greater than most people appreciate. Read the literature in the Soaring Symposium on Competitive Flying authored by Wil Schuemann. Indirectly, that may also validate the use of flaps as being more efficient than using the stick (elevator).