A question...

[camaro_speedemon]

Originally posted by asdf1234:
</font><blockquote>quote:</font><hr />Originally posted by camaro_speedemon:
How can the plane not be stationary?

Why WOULD it be stationary? </font>[/QUOTE]Because the backwards movment of the treadmill would be counteracting any forward movement of the plane.

[airfrmr]

...and no I didn't gradiate H.S. Would you feel better if I told you I work on planes you may be flying?

[camaro_speedemon]

Originally posted by 98Camaro3.8:
</font><blockquote>quote:</font><hr />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. </font>[/QUOTE]But your missing this part

The treadmill has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

I'm taking that as the treadmill is putting sufficient force against the wheels to keep the plane from moving forward.

[fbird01]

if a plane didnt need to be moving to fly, then why wouldnt you just put the engines to full power and take off

theres a reason that planes fly into the wind and go a mile down the runway before they take off

going down the runway at over 100mph creates alot of wind going under and over the wings, producing lift, therefore lifting the plane off the ground.

so on the treadmill there would be no wind passing under or over the wings

have you ever seen a plane lift off the ground at 4mph??? probably not

my father is a retired pilot from NWA and not once did a plane he was flying just takeoff from a standstill, remember the treadmill makes it so the plane makes no foward progress

[98Camaro3.8]

Originally posted by camaro_speedemon:
Because the backwards movment of the treadmill would be counteracting any forward movement of the plane.

The thing is that there isn't a force to counteract the forward movement. The plane is rolling on top of the treadmill. If the brakes were set, the plane would sit right on top and move where the treadmill moved. But with the brakes off, it's rolling. There's no force to fight against the thrust from the engine, so the plane moves forward regardless of the treadmill.

Originally posted by camaro_speedemon:
But your missing this part

</font><blockquote>quote:</font><hr />The treadmill has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

I'm taking that as the treadmill is putting sufficient force against the wheels to keep the plane from moving forward. </font>[/QUOTE]When the airplane moves forward at 10 mph, the treadmill moves the other way at 10 mph. The airplane is still moving at 10 mph because there's no force to stop the thrust. The treadmill doesn't stop or slow the airplane at all.

There isn't a sufficient force against the wheels here. The wheels are rolling freely. You can easily push a car, because there's very little force to fight back.

Originally posted by fbird01:
remember the treadmill makes it so the plane makes no foward progress

No no no no. That's the problem here....it doesn't make the plane sit still. ;)

[ December 01, 2005, 12:37 AM: Message edited by: 98Camaro3.8 ]

[3.4 slow to go]

Originally posted by 98Camaro3.8:
</font><blockquote>quote:</font><hr />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. </font>[/QUOTE]you forgot to mention that runway is moving in the opposite direction of the thrust for this little project

and the french dude's formy is covered in Fluid Mechanics, and that course does cover wing design, at least my course did. Interesting college course that I seriously doubt is covered in high school.

[asdf1234]

Originally posted by airfrmr:
...and no I didn't gradiate H.S. Would you feel better if I told you I work on planes you may be flying?

I don't know about Matt, but that scares the **** out of me.

[fbird01]

then whats the purpose of the treadmill if it doesnt keep the plane still

its just like running on one, you stay on it cuz it moves

[3.4 slow to go]

stop it man, you're talking crazzzy

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.

the plane wouldn't be moving, as whatever thrust is generated by the engines to move the plane is immediately counteracted by the treadmill with the same force. It would by like a cars wheels on a dynometer; yeah it looks cool, but all that spining and going nowhere.

[vroom-chirp]

how about this!!!
if the tread mill is "programed" to match the speed of the wheels, then that meant the very instan the plane wheels start to move the tread mill moves as well, matching the speed, if the tread mill never allows the plane to move foward at all, how would you get the lift you need to take off?

[98Camaro3.8]

Originally posted by fbird01:
then whats the purpose of the treadmill if it doesnt keep the plane still

The purpose of it here is to throw you off by the obvious (but false).

Originally posted by fbird01:

its just like running on one, you stay on it cuz it moves

No, it's not like running. Because when you run you're pushing against the ground, not the air.

Originally posted by 3.4 slow to go:
you forgot to mention that runway is moving in the opposite direction of the thrust for this little project

The fact that it's moving doesn't matter. There's no force on the wheels. Push a car at 5 mph by hand....there's very little force fighting back. The plane is rolling, so there's only a little bit of friction. The treadmill doesn't push back.

Originally posted by 3.4 slow to go:

and the french dude's formy is covered in Fluid Mechanics, and that course does cover wing design, at least my course did. Interesting college course that I seriously doubt is covered in high school.

I'm not sure if you're implying that I only have a high school education, but I'm a senior at Embry-Riddle Aeronautical University. I have taken several classes on aerodynamics. ;)

Originally posted by vroom-chirp:
how about this!!!
if the tread mill is "programed" to match the speed of the wheels, then that meant the very instan the plane wheels start to move the tread mill moves as well, matching the speed, if the tread mill never allows the plane to move foward at all, how would you get the lift you need to take off?

That's not what's happening here. It's matching the speed of the plane not the wheels. In our case, the wheels turn at twice the speed of the plane.

[airfrmr]

I don't know about Matt, but that scares the **** out of me.
It shouldn't. I understand what he is getting at. Just not how an airplane sitting on a stationary treadmill is still moving forward, and I'm sure I'm not the only one.

[asdf1234]

You all are assuming that an airplanes wheels are working the same way as your f-body's wheels are.

An airplane is propelled by a propeller, the wheels are just along for the ride.

If you were to put on a pair of rollerblades and stand on a treadmill that was moving at 100mph, would you go anywhere? No, you would stay still. Now if somebody were to stand behind you and push you forward, you would move forward. Not faster than 100mph, but at the speed of which you were pushed forward. The airplane is being pulled by the propeller. No matter what speed the treadmill is moving, or what direction, the airplane would still move forward as much as it wanted to until it reached speeds able to sustain flight.

[Mogobs30th]

As the plane moves the treadmill moves but in the opposite direction. The treadmill has a system that tracks the speed of the plane and matches it exactly in the opposite direction

What the wheels are doing doesn't matter. The treadmill is counteracting the speed of the plane, NOT THE SPEED OF THE WHEELS. From the ground, the wheels AND the plane are both moving at the same speed, whether or not a treadmill is under it or not. The whole reason why the plane CANNOT take off is because the treadmill is counteracting the speed of the plane, and not the wheels, hence the plane is not moving at all, hence it cannot take off because of the lack of airflow over the flap, aileron, and droop (depending on the size of the plane is whether or not it has droop capabilities).

In order for the plane to take off, it must outrun the speed of the treadmill THROUGH the wheels. But it cannot because the planes speed is being counteracted by the treadmill THROUGH the wheels, regardless how fast the wheels are spinning.

[asdf1234]

Originally posted by airfrmr:
I don't know about Matt, but that scares the **** out of me.
It shouldn't. I understand what he is getting at. Just not how an airplane sitting on a stationary treadmill is still moving forward, and I'm sure I'm not the only one.

Well, as long as you're not designing the airplanes [img]smile.gif[/img]

Hopefully my last post makes some sense of it.