A Level 1 AOA clarification

"Greg Esres" wrote in message
...

relatively small fraction of the total weight of the airplane in the
first place, less than 10% in at least some cases, perhaps most
cases)

Lift in a 10 degree climb should be reduced about 1.5%.

Yes. So? Not relevant to the statement you quoted (which was about
thrust).

I'm not sure your theory holds up very well.

"His" theory is mentioned in a number of aerodynamics books.

Fantastic. It would have been nice of you to provide the name of one
popular (i.e. easy to find) one, so that I can read up on it.

[...] If
you had enough unused AOA left to generate a load factor, you could
change the flight path then return the AOA to its original value. The
aircraft may be able to stay on a steeper flight path due to the
reduced parasite drag and reduced effective weight. Don't forget that
thrust will increase slightly with a lower airspeed.

I admit, I didn't consider scenarios where one is taking advantage of
transient changes in drag and lift. Still, there's not much "unused AOA" in
the regime of flight we're talking about, nor did David suggest that might
be required (his implication, to my reading, was that his suggestion applied
generally, not with very specific pilot techniques and situational
characteristics).

To have a vertical component high enough to support the airplane
will require a horizontal component so high that the airplane won't
slow.

Not really clear on what you mean by that.

Yeah, I was posting pretty late. That wasn't clear at all. My point is
simply that I don't see how you can increase thrust enough to support the
airplane significantly, while still managing to slow the airplane down to
theoretically lower-drag steady state. Perhaps the zoom maneuver you
described is the answer to that.

All of the above is very vague. What I hear you say is "I don't want
to believe you." ;-)

Yes, I admit that readily. But the reason I don't want to believe is that
the proposal bears no resemblance to the behavior of any airplane I've
flown, not while I've been flying it anyway.

I agreed up front that my response is as much hand waving as anything else.
But then so is David's. I'd be more than happy to see someone step in with
some real math that shows the answer one way or the other. I don't happen
to be patient enough with the math. There's a reason that, when I was
working on my math degree, I focused on theory and stayed away from numbers.
Topology was my favorite class, differential equations my least.

There are an infinite number of steady states; every time I move the
elevator, I create a new steady state.

It seems to me that in this context, my qualification of "new steady state"
(and David's for that matter) should have been clear. That is, he's
proposing that at the same speed, there are multiple steady states that
produce different amounts of drag.

Lift is always generated perpendicular to the wing's chord.

No, for subsonic flight, it's perpendicular to the *local* relative
wind, the relative wind that is modified by wingtip vortices.

Mea culpa. Still, in a climb (or descent), lift is not being applied
entirely to counteracting weight.

If lift
were perpendicular to the chordline, you would have induced drag in a
wind tunnel, and you don't.

I understand my error regarding chord versus relative wind. Still, I'm
boggled by the lack of induced drag in a wind tunnel. If the wing's not
creating lift (0 AOA), I can see how there wouldn't be induced drag. But
this would happen in the real world too. If the wing is creating lift,
shouldn't there be a measurable force parallel to the relative wind? Even
in a wind tunnel?

You can measure lift in a wind tunnel. Why not induced drag?

Pete