what the heck is lift?

don't take may word for ask NASA...

http://www.grc.nasa.gov/WWW/K-12/airplane/factors.html

Generally speaking lift = AOA * Airspeed.

Except when accerlating or decelerating up or down (i.e Beginning or
ending a climb or descent) the lift = weight of the airplane. Check out
the 1st few pages of any physic book to verify this. Another way of
thinking about it is that the tension on an elevator (Building elevator
not an airplane elevator) cable always equals the weight of the
elevator and occupants even if the elevator is moving. It changes only
as the elevator accelerates or decelerates.

so since the lift seldom changes the only other 2 variables are AOA
and Airspeed. If you slow down you must increase the AOA to maintain
lift. If you decrease the AOA you must increase airspeed to maintain
lift.

The Rate of Climb indicator directly show excess or Power in a climb or
insufficent power (to maintain alt) in a descent.
Movement of the Rate of climb needle (decreasing or increasing) shows
changes in the amount of lift generated.
A G Meter will directly show the amount of lift being Generated. i.e.
2G = 2x gross weight of the airplane is being generated.

Hope that helps a little

Brian
CFIIG/ASEL

On Fri, 09 Sep 2005 14:29:18 +0200, Thomas Borchert
wrote:

Wings generally tend to have a curved suface. The upper surface has a
greater arc or curvature than the lower surface. As the air flows across the
surfaces of the wing, the upper surface air is forced to move faster than
the lower surface air thus causing a pressure difference between the two
surfaces.

Forced by what? And how does your "theory" explain inverted flight? I don't
buy it.

BTW, this has been beaten to death in countless aviation newsgroup
discussions. I once thought like you, because I was taught that way. It's
still a bad theory. I suggest googling. Keywords might be: lift, flight,
Bernoulli, Newton.


He is describing the traditional airfoil theory which is correct. It
is the most efficient method as it produces lift with minimal drag.
That's what most people are taught.

There is another mode that is related to the force of the air
impacting on the bottom of the wing at high AOA producing lift as
well. Think of your control surfaces. Your rudder control surface is
symmetric, yet it produces horizontial components of force. IIRC, the
Jeppesen books cover high AOA effects as well.

Inverted flight is accomplished by the second of the two effects.
They have to fly at a higher AOA relative to normal flight to
compensate for the airfoil effect. Some aerobatic planes have
symmetric airfoils for this reason.

As AOA increases, the deflection takes more of a role. At stall, the
deflection is suffcient for the airfoil effect to be interfered with
and ceases. Thus a large component of left is lost. You drop. You
still have some lift, but it is not sufficient to keep you airborne.





Jim

http://www.unconventional-wisdom.org

Jimbob,

He is describing the traditional airfoil theory which is correct.


Uhm, no.

--
Thomas Borchert (EDDH)

Gone,

don't take may word for ask NASA...


I do. Sentences no.2 and 3:

"An aerodynamic, curved airfoil will turn a flow. But so will a simple
flat plate, if it is inclined to the flow."

That's a direct contradiction to what you said. Also, see:

http://www.grc.nasa.gov/WWW/K-12/airplane/right2.html

Nothing about curvature, nothing about pressure. My point exactly.

--
Thomas Borchert (EDDH)

Buttman,

This guy is an amazing instructor.


Apparently.

--
Thomas Borchert (EDDH)

"T o d d P a t t i s t" wrote in message
...
Jimbob wrote:

He is describing the traditional airfoil theory which is correct. It
is the most efficient method as it produces lift with minimal drag.
That's what most people are taught.

There is another mode that is related to the force of the air
impacting on the bottom of the wing at high AOA producing lift as
well.

You make it sound like there are two effects, one that
applies in some cases and one that applies in other cases.
The reality is that both descriptions apply in all cases.
They are alternative descriptions of the same thing, and
both "explain" the effect 100%

Inverted flight is accomplished by the second of the two effects.

No, both descriptions (often referred to as the Bernoulli
and Newton descriptions) are 100% correct and either can be
used.




Not AGAIN!!!!!!!!!
:-)))))))))))))))))))))))))))))))))))))))))))))))))) ))))))))))))))))))))))

Dudley

He is describing the traditional airfoil theory which is correct.


Uhm, no.


Oh uhm, YES!

Roger Long wrote:
Lift in a fully developed spin or steady sinking mush is also exactly
the same as in level flight.

Not even close!

Hilton

On Fri, 09 Sep 2005 13:57:30 +0000, Jimbob wrote:

[snip]

There is another mode that is related to the force of the air
impacting on the bottom of the wing at high AOA producing lift as
well. Think of your control surfaces. Your rudder control surface is
symmetric, yet it produces horizontial components of force. IIRC, the
Jeppesen books cover high AOA effects as well.

Isn't this the theory behind lifting bodies (aka, Space Shuttle) and why
many low wing planes tend to generate some minor amount of lift across the
fuslage area, in between the root coords?

[snip]