On Tuesday, 23 February 2021 at 16:10:07 UTC, Eric Greenwell wrote:
Jon May wrote on 2/23/2021 3:46 AM:
On Tuesday, 23 February 2021 at 11:07:26 UTC, Jon May wrote:
On Sunday, 21 February 2021 at 19:55:22 wrote:
Does anyone not consider that there is a difference between pattern speed where maneuvering and other factors come into play versus on short final approach speed say starting at 1/4 mile where a stabilized approach using the manufacturers numbers by design gives you a safe, consistent, lower energy spot landing (hopefully) every time and still enough energy to use a lot of spoilers if needed whether you are heavy or light to adjust some. If you are convinced YT is wrong for your airframe, talk to others in type before you decide to move it a knot or two up or down and after you are convinced about the accuracy of your stall speed vs the POH.
Carl, 7E
I am posting an paper on wing profiles because it helps explain the effects newer wing shapes have on the flare to land.
Jon
Effects of the step in lift-curves of wing profiles with flaps
by Karel Termaat
Introduction (third alinea modified since publication in S&G)
Some years ago, I found that when landing our new sailplane it usually made a couple of bumps onto the ground before it decided to stay there; very interesting to friends observing your flying skills with the new toy of course. Another surprising thing happened to me with this sailplane when I made a long cross-country flight, came back a little late and low and decided to divert from my shortest route to the airfield to an area where small flocks of cumulus clouds were still forming. To my surprise I could not climb there, even though the air was quite turbulent and going up on average. I tried another identical spot with the same disappointing result. I flew out of this promising area and found a weak smooth thermal which brought me home.. Quite a frustrating experience.
I noticed this difficulty during landing with my ASH26E about 25 years ago, but did not know
the cause until listening to Loek Boerman lecture on the subject a few years later. He
confirmed my guess it was due to the same CL step that was affecting the thermal climb in
gliders designed in that early '90s era. Later, when I began routine use of the 40 degree
landing flap, it seemed the effect was not so pronounced. Getting the attitude correct for a
two-point (or a tail-first) touchdown seemed to be best; keeping the spoilers constant after
the flare made it easier.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
The current generation of flapped high performance gliders (e.g. the Diana 2, ASH 30 [and no doubt the 33], the JS1 [same section as the JS3/2/5], Arcus, and the Ventus 3) have airfoils designed to avoid a step in the lift curve, as Karel Termaat pointed out in his article version he
http://home.planet.nl/~kpt9/thermiek...%20deutsch.htm