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Scott -
I won't answer your question about "tripping" or
"turbulating" an airfoil because it really is horribly complex and
situation-dependant. Here's some info in the "Aerodynamics" section of Dr.
Martin Hepperle's site:
However, I *will* (in my own novice way) attempt to
explain why the nose of the plane changes pitch when you activate spoilers or
flaps:
Remember that your airplane has two "centers", the
center of gravity and the center of lift (or effort). One is the
theoretical "balance point" for downward forces on the plane; the other is for
the theoretical "balance point" of upward forces on the plane from the wing's
lift (which passes through the "center of pressure" of the airfoil).
See these links for more detail on
this:
http://142.26.194.131/aerodynamics1/Basics/Page2.html
(currently offline, but excellent)
These two opposing forces rarely line up; and often
the tail surfaces are used to counteract any pitching moment that the airfoil
produces as it flies through the air and generates lift.
Changing the camber (the curvature) of the wing
surface changes the center of pressure and possibly the "effective" angle of
attack relative to the oncoming airstream (think about an imaginary line running
between the trailing edge of the wing and the leading edge. Now drop the
flaps - see how the angle of this imaginary line has changed?). Since the
center of gravity DOESN'T change, the distance between the CG and the center of
pressure/effort might change and the pitching moments and forces may all
change. It is these changes that must then be counteracted by changing the
tail-surface deflection.
Hope this makes things more clear - the web links
are really great sources of info!
Take care,
--Noel
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- RE: [RCSE] Tripping modern airfoils, and why do flaps and s... Noel Wade
