Mythbusters tonight

[CT_Nismo]

Originally Posted by kennith

Unstrap the Frontier and put a jet engine in the bed. Then see what happens.

The is a rediculous question. The plane will take off. Period.

Cheers,

Kennith

I don't know why I am having such a difficult time communicating my thoughts.

I totally agree that the plane will take off, no questions. It is only under partial throttle that the plane will not take off. But this is ludicrious because applying partial throttle on a plane on a runway will also result in no take-off.

The dyno example was to demonstrate that the conveyor cannot instill translational velocity to the plane.

Let me rephrase. To test a vehicle for emissions, the driven wheels are placed between adjacent metal rollers. Engine rpm is raised and the tailpipe gases are tested. The car does not physically move. Examine this scenario and you will see that it is the same as the conveyor and the plane. Whether torque is applied by the drive wheels to the adjacent rollers or vice versa, the car does not move.

However, as I am learning, even this example may be too abstract for viewers of this thread.

[Nitewulf]

I cannot believe this has made it to TEN PAGES. Ok folks, all those saying it wont matter because the jet engine is pushing it, pat yourself on the back. Everyone else (cant believe I actually have to post this..)

http://www.fi.edu/flights/own2/forces.html

This explains all for those of you that cannot grasp how it works. I is called a runway because it needs to get up to speed for adequate air flow over the top of the wing to create lift for the underside of the wing. Spinning the wheels to make the plane launch. Wait there is a few planes that I know of that do not require a runway.

the harrier jumpjet:
http://www.militaryfactory.com/aircr...aircraft_id=47

the osprey:
http://www.fas.org/man/dod-101/sys/ac/v-22.htm

both of those are verticle ascent planes, other than that it is why the captain yell prepare for take off, cause you need to get moving at high velocity to feed the wings the airflow they need.

[kennith]

Originally Posted by CT_Nismo

I don't know why I am having such a difficult time communicating my thoughts.

I totally agree that the plane will take off, no questions. It is only under partial throttle that the plane will not take off. But this is ludicrious because applying partial throttle on a plane on a runway will also result in no take-off.

The dyno example was to demonstrate that the conveyor cannot instill translational velocity to the plane.

Let me rephrase. To test a vehicle for emissions, the driven wheels are placed between adjacent metal rollers. Engine rpm is raised and the tailpipe gases are tested. The car does not physically move. Examine this scenario and you will see that it is the same as the conveyor and the plane. Whether torque is applied by the drive wheels to the adjacent rollers or vice versa, the car does not move.

However, as I am learning, even this example may be too abstract for viewers of this thread.

Sounds like you are saying that if the car doesn't roll off the Dyno, the belt won't affect the plane. Now THAT makes sense.

It's not that great an example, because cars have to be strapped to Dynos to prevent them running off, but in a perfect scenario, it makes sense.

If that's what you are getting at, I understand what you mean. I wouldn't personally use that example, but I get it.

That's not how it read the first time you said it.

Cheers,

Kennith

[ARCTICFRONTIER]

This thread was started two days ago. What was the verdict on the show?

[westexasrepublic]

this myth never made it to the show,

But i think its funny how people are starting to back out of their ludicris theories that the plane will not take off on a moving runway.

Of course now that I posted the videos explaining the simplicity.

[Mainerunr]

Originally Posted by westexasrepublic

this myth never made it to the show,

But i think its funny how people are starting to back out of their ludicris theories that the plane will not take off on a moving runway.

Of course now that I posted the videos explaining the simplicity.

the only reason I said it wouldnt is because of the wording mountaineer was using...under the conditions he specified, I stand by my staement that it woudl not get airborne. and before that, when I thought the wording was what it is, I said it would take off...change the specified conditions and the answer changes

[Mountaineer]

The way I've heard the problem put is that the plane and the treadmill are at the same speed. Its been a few months since I read it on the website, but that's how I remember.

[fleaofsc]

Originally Posted by Mainerunr

the only reason I said it wouldnt is because of the wording mountaineer was using...under the conditions he specified, I stand by my staement that it woudl not get airborne. and before that, when I thought the wording was what it is, I said it would take off...change the specified conditions and the answer changes

Ok, then yah, I did agree with you... thats what I thought you were getting at. We can safely know that we are right.

[roastbeef]

i still maintain my theory that the plane would not take off.

there is very significant resistance against the free spinning wheels.
pretend you have a toy car on a treadmill. the treadmill is on, and you are holding it in place. the moment you let go of the car, it will immediately begin to 'slow' and fall off the back of the treadmill pretty quickly.

the same applies to an airplane. even though the airplane is moving by creating thrust, the engines are still working to keep the plane from falling off the back of the treadmill. the engines can not create and infinant amount of trust, and therefore, can not create enough thrust to overcome the resistance against the spinning wheels. im willing to bet the turbines would burn up too.

in a perfect world where there was no friction, the plane would take off. if there was no friction, the toy car on the treadmill would remain stationary when you let go, also.

[CT_Nismo]

Originally Posted by fleaofsc

Ok, then yah, I did agree with you... thats what I thought you were getting at. We can safely know that we are right.

The situation you and Maine are describing does nothing to explain if the plane will take off. To attain the friction balance point, the engines must be significantly throttled back. Any plane, whether on a treadmill, or runway cannot take off without take-off thrust.

You have only proven that the plane will not take off due to lack of power. That is not what this myth is about.

Originally Posted by roastbeef

i still maintain my theory that the plane would not take off.

there is very significant resistance against the free spinning wheels.
pretend you have a toy car on a treadmill. the treadmill is on, and you are holding it in place. the moment you let go of the car, it will immediately begin to 'slow' and fall off the back of the treadmill pretty quickly.

the same applies to an airplane. even though the airplane is moving by creating thrust, the engines are still working to keep the plane from falling off the back of the treadmill. the engines can not create and infinant amount of trust, and therefore, can not create enough thrust to overcome the resistance against the spinning wheels. im willing to bet the turbines would burn up too.

in a perfect world where there was no friction, the plane would take off. if there was no friction, the toy car on the treadmill would remain stationary when you let go, also.

As you are holding the toy car in place on the moving treadmill, take a sense of the force needed to resist the moving conveyor. Now imagine what force will be needed to accelerate the toy car to take-off speed. This is about 150 mph. Imagine holding this toy car out your car window at 60 mph. How much force will you need to keep it from flying away? Imagine if you held the car out the window of a car going 150 mph. Get the idea? The force needed to hold a toy car at 150 mph against rushing air is the same force needed to accelerate the car to 150 mph. This force is orders of magnitude larger than the force needed to hold the car against the motion of the treadmill.

But you say, as the toy car accelerates, the treadmill drag goes up also. It goes up some, but not as dramatically as air drag. If the treadmill were running at 60 mph, would you expect the force need to hold the car in place to be the same as in 60 mph rushing air?

The frictional traction forces at the plane-treadmill interface are trivial when compared against the massive forces generated by the engines to acccerate the plane to take-off speed.