Newbie Qs on stalls and spins

My comments in text...




"Peter Duniho" wrote in message
...
"Bill Denton" wrote in message
...
You are both right and wrong on this one.

No. I am entirely right, not wrong at all.

Obviously, different parts of an aircraft stall at different speeds.

This is true, but completely irrelevant to my statement.

[...]
You then take an airplane to 1,000 ft AGL, and trim it so it is flying
perfectly straight and level, but this time you completely close the
throttle. In a short time, the wings will stop producing enough lift to
keep
the airplane in flight, it will pitch down and impact the earth, even
though
some of the airplane's component parts may still be flying.

First, your scenario is completely incorrect as to what would happen if
you
brought the throttle to idle. The airplane would NOT stall. It would
simply pitch down enough to maintain the trimmed airspeed, and glide to
whatever final destination it was aimed at.

Both scenarios are incorrect as originally posted. Please see my second
respone to Bob Moore (just above) for my corrections.



But more importantly, your understanding of a stall is flawed. Even
simply
looking at just the wing, and even ignoring such design features as
washout,
upon reaching the critical angle of attack lift does not go straight from
maximum available lift to 0. There is a very narrow range of angle of
attack where the lift drops off rapidly, and within this range, there is
just as much lift as was available at angles of attack just below the
critical angle of attack.

For a variety of reasons, it's unlikely that a pilot would ever
successfully
negotiate this very narrow range. But it does exist, and a person who
claims that a wing is strictly "not stalled" or "stalled" is simply
demonstrated lack of completely knowledge of what happens during a stall.
A
stall is more like a dimmer light switch (with a very short throw) than it
is like a regular "on/off" light switch.

From my previous post: "Obviously, there is a range between the point where
an element is producing zero lift, where it is producing enough lift to
"fly" the unit itself at a consistent altitude, and where it is produing
enough lift to fly the required load at a consistent altitude."

The inverse would also be true.

Generally, I am using the term "stall" to indicate a state where the object
is producing zero lift, and "flying" to indicate that some lift is being
produced. However, I sometimes use flying to indicate that the object is
generating enough lift to raise itself and it's load above the earth. I will
try to be more consistent and clear in the future.

I don't claim that this is absolutely, or in any way correct, but this is
how I am using the terms.



[...] I think it is also evident that I do understand at least the
basic principles involved in the discussion.

Very basic principles. But you still have quite a ways to go. You might
do
well to stop telling people they are wrong, at least until you've actually
*mastered* the subject.

But please assume an airplane, accept my terminology, and consider the
following:

If a wheel is rolling, you cannot start it rolling.

My statement was: " If the airfoil is flying you cannot take off, and if
it's not flying it's stalled", which would translate as follows: "If the
airplane IS flying it cannot START flying"' the rest reflects the
flying/stalled paradyme, which I readly admit is not absolutely correct.

So you really did mean to write "if the airfoil is flying you cannot take
off". I've got to say, that's got to be one of the most intentionally
obtuse ways of saying something I've seen in a long time.

That is what I mean to write, but again I was not writing from scratch; I
was picking up on the orignal poster.



In any case, you are simply incorrect to say "if it's not flying it's
stalled". That is a patently false proposition. I have an airplane
sitting
in my hangar right now that is not flying (at least, it had better not
be!),
but it is not stalled either.

No argument that I am probably using the terms incorrectly; please see my
previous note.


Actually, it was the original poster who failed to define "flying" and
specify what was flying. As noted above, I am looking at this in the
context
of an entire airplane, which seems to have been the original poster's
intent.

Another red herring. It really doesn't matter whether you are talking
about
the entire airplane or the wing. But for the record, when one refers to a
"stall", they are generally referring to a stall of the main wing (and by
implication, the entire airplane).

Which is the way I am generally using the term, unless I am specifically
referring to a stall affecting only a specific portion of an airplane.


In fact, the airplane doesn't need to move on the runway at all;
given a sufficient releative wind, parts of the airplane would begin to
fly
without the airplane moving forward at all.

I thought your claim was that an airplane that was flying (and thus
presumably parts of an airplane that are flying) cannot take off. Now you
are saying parts of the airplane can fly while still on the ground. Your
statements are inconsistent with each other.

That was what I stated, if the ENTIRE airplane is flying, i.e. with no parts
in contact with the earth, it cannot take off.

But with a tail dragger, doesn't the horizontal stabilizer begin to produce
enough lift to raise the tail, and raise the tailwheel above the earth,
before the wing produces enough lift to raise the entire airplane abouve the
earth?



And given a relative wind even
slightly higher than the stall speed of the aircraft, it could
theoretically
take off and continue to ascend with no forward movement.

No, it could not. With a strong enough wind, the airplane might lift off
the ground, but it would immediately begin to slow within the airmass
(accelerating backwards relative to the ground) and descend back to the
ground. There would be no "continue to ascend" about it.

"accelerating backwards relative to the ground" is not the same as "no
forward movement".

I was incorrect with "continue to ascend".


I agree with your definition, but it has to be consiered in light of
whether
we are discussing a single element or an entire airplane.

We are discussing the wing, which is the only thing of interest in this
case. If you want to call that "the entire airplane", that's fine too,
but
make no mistake: it's still just the wing.

But just a wing in a wind tunnel behaves differently than the same wing when
attached to an airplane. And parts of an airplane other than the wing can
generate lift.



If an airplane is only moving at 1
kt. down a runway, it is probably not flying.

Again, you'll have to define "flying". But the wing certainly is
developing
lift, and certainly is NOT stalled.

I should have added "in a condition of zero wind". Given that, there are
probably wings out there that would not generate appreciable lift at 1 kt.



How 'bout if I throw in a 10 kt tailwind? g

If you want to change the discussion in an attempt to make your comments
make sense, feel free. I probably won't have the patience to bother
though,
and will simply feel justified in assuming that you aren't really
interested
in learning what the facts are.

I recommend you stick with the original ideas, and where you've clearly
meant "1 knot of relative wind" by saying "if an airplane is only moving
at
1 knot down a runway", you should avoid complicating things by trying to
reinterpret what you've written.

As I noted above, I failed to address relative wind and referred only to the
aircraft's speed.



Simply untrue. Virtually all of my landings involve touching down and
coming to a stop without ever exceeding the wing's critical AOA. I
hesitate
to claim that I've *never* stalled the wing during a landing, but I
sure
don't do it intentionally.

And this comes back to the flying/stalled paradym.

Sometimes I rely too much on spell chekers.



The word is "paradigm". And frankly, I have no idea what you mean by
"this
comes back to". This thread *should* have stayed with the question of a
stall all along. Only your digressions have prevented that.

The bottom line here is that your statements that "you can't take off
without a stall" and that "an aircraft will not land until it has reached
a
stalled state" are both patently false. You can very much both take off
and
land without ever stalling the airplane.

Again, that comes down to terminology; and I again state that I may well be
using it incorrectly.



Pete