wrote:
On Mar 29, 11:43 am, Eric Greenwell wrote:
Eric Greenwell wrote:
I attended Boerman's lecture. The problem isn't thin, laminar flow
airfoils in general, but some specific designs over the last two decades
or so that have a "flat spot" in the lift coefficient (Cl) curve as the
angle of attack (AOA) approaches stall. Normally, the Cl increases with
increasing AOA, but in the flat spot region, it remains constant (or
nearly so) even as the AOA increases. Past this region, Cl begins to
increase again with AOA at the usual rate.
I should add that designers were aware of the flat spot years ago, but
did not appreciate the problems it could cause in gusty conditions.


If I understood Loek correctly, "gusty" isn't perhaps the right
description. Better "high frequency changes in vertical velocity,
causing momentary increases in required CL" ? Its not something
you'd necessarily feel as a pilot if I understood correctly.
Eric ?

I don't recall the presentation well enough to say for sure, but my
impression is the pilot would be aware that it's not smooth air,
probably enough that the pilot would be making some control corrections.
It would be better to ask Loek, or someone like Dan Somers or Mark
Maughmer, who are also aware of it.

--
Eric Greenwell - Washington State, USA
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