A Level 1 AOA clarification

"G.R. Patterson III" wrote in message
...
I'll try to simplify it a bit. An angle of attack is the angle at which
the wing
"attacks" the air. If the air is relatively stable and you raise the nose,
you
have just increased the angle of attack. Lower the nose, the angle
decreases.

To elaborate a bit: Ramapriya's assertion that "the angle of the wings can't
be varied" is incorrect. The angle of the wings can be and is varied, by
using the elevator control to adjust the pitch attitude of the aircraft, and
thus of the wings.

This is what George means by "raise the nose".

[...] If I undrestand him correctly, Andrew is stating that
the angle of attack at which this occurs is the same regardless of
airspeed. I
believe he is incorrect in this - definitely my aircraft will stall at a
much
lower angle of attack at 50 mph than at 60 mph

You understand Andrew correctly, but not stalling.

Since you mention stalling at two different airspeeds, let's look at those
as examples. Let's assume that at the lower airspeed, you are stall in
unaccelerated flight. There are two ways to stall the airplane at a higher
airspeed then: one is to pull hard on the yoke to increase loading and pitch
attitude to stall before the airplane slows further; the other is to have
the flaps out at the slower airspeed, but not the higher.

In the first case, the pitch attitude appears higher, but the angle of
attack is the same. The airplane, because of the higher pitch angle, is
accelerating upward, which changes the direction of the relative wind
somewhat downward, making a given angle of attack occur at a higher pitch
angle.

In the second case, the pitch attitude appears higher, but the angle of
attack is the same (sound familiar? ). When the flaps are extended, the
effective chord of the wing changes, essentially pitching the wing upward
and increasing angle of attack. This increases the angle of incidence of
the wing (the angle between the wing chord and the fuselage), causing a
given angle of attack to occur at a lower pitch angle, compared to a
no-flaps stall (at a higher airspeed).

The flaps might also change the stalling angle of attack subtly, but a) most
of the perceived change in angle of attack comes from the change in
effective angle of incidence, and b) the change in AOA in that case is due
to the change in shape of the wing, not the change in airspeed.

[...]
Now, there *is* a misconception that stall airspeeds are constant, and
this is
not true. The way the truth is usually phrased is "an airplane can stall
at any
speed."

You forgot the other half of that: an airplane can stall at any attitude.
Pilots often mistake pitch angle relative to the ground for angle of attack.
In level, 1-G flight this is the case. But you can exceed the critical
angle of attack with the nose pointed down (pulling out from a high-speed
dive for example), and you can have the nose pointed quite high (during a
climb in a high performance airplane, especially at lower weights), without
exceeding the critical angle of attack.

[...]
I do not know whether or not the stall angle of attack changes with
weight, but
the stall airspeed in any configuration increases as weight increases.

Weight does not affect the stalling angle of attack.

Pete