"Neil Gould" wrote in message
. ..
Recently, T o d d P a t t i s t posted:

This is a matter of semantics. I consider myself to be
flying even when practicing spins with both wings stalled.

I thought one could only maintain a spin where *one* wing is stalled, and
the other not? If both wings stall, the spin should stop and the plane
should fall.

Anyone trying to describe spin aerodynamics in one or two sentences is
doomed to failure. That said, to think of it as a "one wing stalled,
one wing flying" scenario is insufficient, IMHO. Each wing is creating
different amounts of lift, true...and a stall has occurred, also true. But
both wings can still be generating lift, while still both remaining stalled.
It's the asymmetric lift that causes the spin, regardless of whether both
wings are stalled or not.

First point:
I also consider aerobatics pilots to be flying when using a
powerful engine to supplement reduced lift and fly with both
wings stalled.

Well, they're "flying" by power lift, in the same sense that a Harrier is
"flying" when hovering. The wings are irrelevant in those situations. So,
in the context of "greasing on" a full-stall landing in a typical SEL,
those scenarios are irrelevant to the OP.

If the wing has non-zero motion relative to the air, it has a defined
angle-of-attack, and thus can be determined to be stalled or not stalled.
Whether the wing is providing any significant lift contribution to helping
the airplane maintain altitude is irrelevant to the question of whether the
airplane is flying with both wings stalled or not.

In particular, Todd's comment simply corrects the statement that "when
you're stalled, you're falling, not flying". Using power to keep oneself
aloft is still "flying", even if the wings are stalled. Thus, it is not
always true that "when you're stalled, you're...not flying", even if it IS
true in most situations.

The
point I'm making here is that a stalled wing still produces
lots of lift. In fact, near stall, it's producing nearly
the maximum lift that the wing is capable of producing.

Is that like saying, "Even those that don't have an income can purchase
the most expensive plane they can afford"? ;-)

That depends on what you mean by "don't have an income". It's more like
saying that "even those whose income has peaked and is now going back down
can purchase an airplane almost as expensive as one they could have afforded
at their peak income".

In other words, what Todd is saying is that lift doesn't just quit in a
discontinuous way at the stall. If you look at the graph of lift versus
angle of attack, the peak of that graph occurs right at the stalling angle
of attack, and then starts to drop off from there. It does drop quite a bit
more rapidly than the other side of the graph where lift is increasing, but
it doesn't just jump to zero.

Assuming you could maintain control of the airplane in a fashion to ensure
that you exceeded the stalling angle of attack only by a tiny fraction of a
degree, you would wind up getting almost as much lift as you were getting
right at the instant you stalled.

There are, of course, other issues. The graph I'm talking about is actually
the lift coefficient graph; actual lift depends on the lift coefficient
(angle of attack) and airspeed. Drag increases dramatically at stall, and
it would require a lot of extra power to maintain an airspeed sufficient to
produce lift equal to the airplane's weight, flying just past the stalling
angle of attack. But it certainly is theoretically possibly.

Second Point:
It is exceptionally difficult to actually get to a full
stall attitude for landing. What is often called a "full
stall landing" or "3 point landing" does not actually have
the wing at stall AOA. Many aircraft would hit their tail
if they were low enough to safely land and the wing was at
stall AOA.

I completely disagree with this notion. The AOA is a vector of the
relative direction of travel through air.

The AOA is the "angle-of-attack". It's not a vector at all, never mind the
one you describe. It is true that the AOA is relative to direction of
travel through air (ie the "relative wind").

There is no requirement that
there be a nose-high attitude in a stall, only that the wind traveling
over the wing is lower than what is required to produce lift. It isn't
difficult to hold a typical SEL aircraft in a nose-down stall, and in
fact, a descending turning stall is a required manouvre in the private
PTS.

Read Todd's statement again. He is clearly talking only about the situation
during a landing. The motion of the aircraft through the air just prior to
touchdown is necessarily nearly or precisely parallel to the ground. And it
is true that with most airplanes, the stalling angle-of-attack produces a
pitch angle so nose-high that the tail will hit the ground before the main
gear does.

Which was the entire point of the phrase Todd uses: "if they were low enough
to safely land and the wing was at stall AOA". If they are low enough to
land and are at a nose-down stalling AOA, they are milliseconds from
crashing. Which is clearly not the scenario we're talking about here.

You are certainly correct that an airplane can be stalled in any attitude.
But that in no way provides a basis for disagreement with Todd's statements.

Pete