A question...

[98Camaro3.8]

Originally posted by 3.4 slow to go:
I still fail to see how there is any air moving over the wings, since the wheels treadmill is going the exact speed opposite that the plane is going. Talking commercial jets, the engines are under the wings, thus no air speed over the wings. And for those saying the thrust under the wings will provide the lift, well that thrust isn't under all the wings underside surface area.

The lift isn't created by the engine. The thing to try to figure out is that the treadmill does not effect the movement of the airplane. The plane accelerates normally with or without the treadmill there. The air over the wings is because the airplane is moving through the air like during a normal takeoff.

Originally posted by 3.4 slow to go:
obtw, it's the pressure difference between the slower upper side & faster underside of air that creates lift.

That's backwards, but that is mostly correct for Bernoulli's principle. Newton's 3rd law(action/reaction) is just as important for the creation of lift. Your hand outside a moving car creates lift because of this "barn door effect".

[camaro_speedemon]

OK seriously, think about this. You're running on a treadmill, do you feel a breeze? No, because your not moving THROUGH air, YOU'RE running at 10MPH, but the air around you is stationary.

OK now to translate this to the plane, if the plane is remaining stationary, then the air is remaining stationary and not moving across the wings to create lift. You may have groundspeed of 400MPH, but airspeed of 0 MPH.

Think of this, if you put a giant wind machine infront of a stationary plane(minus the treadmill), it would allow the plane to take off because it is moving wind across the wings, creating lift and the wheels wouldn't have to move at all. The opposite is true here, the wheels are moving, but the air is not.

[98Camaro3.8]

Originally posted by camaro_speedemon:
OK seriously, think about this. You're running on a treadmill, do you feel a breeze? No, because your not moving THROUGH air, YOU'RE running at 10MPH, but the air around you is stationary.

I know it's been said before, but.....you can't compare that!! An airplane isn't pushing against the ground, it's pushing against the air...totally different here.

Originally posted by camaro_speedemon:

OK now to translate this to the plane, if the plane is remaining stationary, then the air is remaining stationary and not moving across the wings to create lift. You may have groundspeed of 400MPH, but airspeed of 0 MPH.

The airspeed will be at a normal value for takeoff. Lift will be created because the plane is actually moving through the air. The wheels will be turning at twice the airspeed (because the treadmill is turning in the opposite direction). The treadmill has absolutely no effect besides turning the wheels a little faster.

[airfrmr]

Know matter how fast the "treadmill" is going, without thrust forcing the aircraft through air and creating lift from the wings, it can not and will not fly.
Oh BTW, do some more research on Bernoulli's principle. "Bernoulli's Principle states that as the speed of a moving fluid increases, the pressure within the fluid decreases" An aircraft can fly without it.

[camaro_speedemon]

Originally posted by 98Camaro3.8:
</font><blockquote>quote:</font><hr />Originally posted by camaro_speedemon:
OK seriously, think about this. You're running on a treadmill, do you feel a breeze? No, because your not moving THROUGH air, YOU'RE running at 10MPH, but the air around you is stationary.

I know it's been said before, but.....you can't compare that!! An airplane isn't pushing against the ground, it's pushing against the air...totally different here.

Originally posted by camaro_speedemon:

OK now to translate this to the plane, if the plane is remaining stationary, then the air is remaining stationary and not moving across the wings to create lift. You may have groundspeed of 400MPH, but airspeed of 0 MPH.

The airspeed will be at a normal value for takeoff. Lift will be created because the plane is actually moving through the air. The wheels will be turning at twice the airspeed (because the treadmill is turning in the opposite direction). The treadmill has absolutely no effect besides turning the wheels a little faster. </font>[/QUOTE]How can the plane move through stationary air, if the plane is stationary?

[vroom-chirp]

look at it like this....
a plane is made to fly like this way ------&gt;
the tread mill is rolling this way &lt;------
so this means the plane wont move right?..wrong

top of the runway is going this way ------&gt;
so that means the bottom is moveing &lt;------
causing the runway to roll like a wheel.
so if the plane is on top it is actually rolling the wrong way to take off!!
plane
------&gt;
top
&lt;------
bottom
------&gt;
direction of travle
&lt;---------
so you see, the plane cannot take off because it wasnt made to fly backward!!, but as posted a harier would have no problem...
im an aircraft refueler

[98Camaro3.8]

Originally posted by airfrmr:
Know matter how fast the "treadmill" is going, without thrust forcing the aircraft through air and creating lift from the wings, it can not and will not fly.

Yeah, what's your point? Nobody ever said the airplane didn't have thrust. The problem people have is seeing that the thrust has no drag to counteract it, so the plane moves forward, which allows the wings to create lift.

Originally posted by airfrmr:

Oh BTW, do some more research on Bernoulli's principle. "Bernoulli's Principle states that as the speed of a moving fluid increases, the pressure within the fluid decreases" An aircraft can fly without it.

Oh BTW, this just happens to be the main reason a wing creates lift (that and downwash). The air passes over the curved surface much like a venturi. As it passes through this area, the velocity of the fluid (air) increases. At the same time, the pressure decreases. Now you have a high pressure on bottom and low pressure on top. Pressure gradient force tries to move the high pressure towards the low pressure, which forces the wing up = lift. So tell me, wtf is your point?

Originally posted by camaro_speedemon:
How can the plane move through stationary air, if the plane is stationary?

The plane isn't stationary!!!!!!!!!! [img]smile.gif[/img]

[vroom-chirp]

so when a plane is running, but not moveing, their is no air sweeping over the wings, inturn it cant fly, no lift... the only way for an aircraft to fly is to be in motion.

[airfrmr]

My point is your a dumba$$. bernoulli's principle is for fluid not air retard.
the plane is stationary if it's on a treadmill, where the hell is it going to go?

[98Camaro3.8]

Originally posted by airfrmr:
My point is your a dumba$$. bernoulli's principle is for fluid not air retard.

You cannot be serious. You graduated high school didn't you? Here's a link to HowStuffWorks. Then maybe you should enroll in another physics course. And an English course while you're at it.

[camaro_speedemon]

How can the plane not be stationary?

[asdf1234]

Originally posted by camaro_speedemon:
How can the plane not be stationary?

Why WOULD it be stationary?

[98Camaro3.8]

Originally posted by camaro_speedemon:
How can the plane not be stationary?

It's all about forces. There is no force to cancel out the thrust from the engine. The plane is rolling freely over the treadmill, with very little friction.

If the airplane is moving to the left:
&lt;------------------ Thrust from the engine
-&gt; Drag from friction on the wheels (because they're rolling with the brakes off).

That results in a net force of thrust, so the plane accelerates.

[airfrmr]

My apologies , I have always applied Benoulli's principle to fluid not air.

[vroom-chirp]

dont make me pull this car over you two!!!!!!! [img]graemlins/rant.gif[/img]