Mythbusters will finally test...

[SarichFan]

Youtube or it didn't happen..

[Dan02]

Originally Posted by Bobblehead

And the official Mythbusters forum goes crazy with people who still don't believe the plane would fly. Even the Executive Producer posts that they did it correctly and explains why. I don't think it will matter to those who refuse to believe.

http://community.discovery.com/eve/f...m/f/9401967776

wow i didn't know people could be so stupid.

I figure that the majority must be misunderstanding the challenge, there can't be that many morons out there can there?

[FlamesInYourEyes]

If you were to suspened a jet in mid air, then spin its tires really fast (say the same speed the tires spin when the jet takes off) then drop the jet from its suspension would it be able to take off from mid air?

If you have any doubts about this, maybe physics is just not your subject, but this is the same principal as the conveyer belt!

[octothorp]

Wow, 90 pages of discussion on that site and still people arguing. I'm curious to get the opinions of those people here who thought the plane wouldn't fly:
Do you feel, as some people do on the fan site, that the expiriment was done incorrectly due to a failure to match the conveyor speed to the plane speed correctly?
Do you believe that they interpreted the myth wrong, and that the myth, by definition, means that the plane cannot move forward and is supposed to just lift off the ground like a helicopter?
Or do you now feel that you were wrong in your understanding of the myth or of physics and that the results are valid?

[llama64]

I don't get what the debate is...

Lift with an airplane is generated entirely by moving air over the wings. If the plane is allowed to move forward relational to a fixed position and enough speed is generated, the plane will begin to fly.

The conveyor belt will have no effect on the experiment whatsoever as long as forward force is being generated by the engines. Now if the wheels themselves were responsible for the forward motion, then the conveyor belt comes into play.

There is no debate as far as I can tell. Just people misunderstanding how an air-plane works.

[llama64]

Originally Posted by metal_geek

What would happen in the opposite situation... a plane landing on a conveyor belt moving the same speed at the plan in the opposite direction? I would think the plane would land on the belt and land the same as normal minus the distance caused by the breaking friction. The only difference would be the "Speed" of the wheels would be double that of normal landing speed on contact..

That's an excellent counter example!

In this case, the motion is directly being affected by the wheels contact on the conveyor-belt. The actual stopping distance travelled relational to the belt itself would be the same as an actual runway (assuming the same friction coefficients), but the relative distance to a fixed point off the belt would be less since the belt would push the plane back.

[Burninator]

Just glancing at those forums is painful. I bet the knowledgeable and reasonable posters are just banging their heads on their desks.

Me and my brother (engineering student) watched it last night and were very satisfied with the plane test. My brother even wrote up a force diagram before we watched it to show the result. I thought they did an excellent job explaining why they got the result they did. I can't really understand how someone could have watched that episode and disagreed with their conclusion.

The quote of the episode was when they were testing the small plane on the treadmill and after the plane left the runway Jamie said something to the effect of, "And we were expecting what to happen?" in a very sarcastic tone. Great, summed up everything quite nicely.

[Hack&Lube]

"Because the conveyor belt speed is the inverse of the plane's airspeed, we can say that the conveyor belt does not move until the plane begins to accelerate forward. Thus, rolling resistance has already been overcome by thrust when this problem really begins.

Initially, the engine thrust is considerably higher than the drag—this is what allows aircraft to take off on regular runways. So the question is, once we start moving and the conveyor belt starts up, does it impose some force on the aircraft that can overcome the force of thrust?"

The point is that people are expected the conveyer to be moving so fast that it counteracts the forward thrust of the plane completely, that kind of speed would probably melt the bearings on the wheels. I think that's the real spirit of the myth. That the plane remains in a stationary and static position relative to the ground where the conveyer belt is negating any rolling resistance completely and negating any thrust. Therefore, it achieves no airspeed and therefore the wings achieve no lift. That is what I believe to be the true spirit of the myth. Too bad they failed to actually test this.

[photon]

I don't think that's the spirit of the myth though, I think it's the whole cars push against the ground, airplanes push against the air part.

The myth as I've seen it most places is "the treadmill is going backwards at the same speed of the airplane", rather than "the treadmill is going backwards and many hundreds of times the speed of the airplane".

I would have liked to see them try to test that though, spin the thing fast enough to slow the plane down. It would have flipped it over or broken the gear though, planes aren't designed to take that kind of stress through the gear.

[Hemi-Cuda]

"The myth is that a plane on a conveyor belt will be able to take off"

so are there 94 CP members who were totally wrong, or just confused on the poll question as i was? i thought the myth was that the plan WILL take off (like the poll says) so i voted confirmed. but on the show they said the myth was that the plane WON'T take off, so in reality it's busted

i demand a repoll

[llama64]

The original version of the myth involved an assumption of no frictional force being acted on the wheels. Or at least the one I saw. Also the speed matching wasn't conveyor to plane but conveyor to wheel.

[Hack&Lube]

"The myth is that a plane on a conveyor belt will be able to take off"
-What do you think when you first read that line? When you imagine a plane on a conveyer belt you imagine a man running on a treadmill. He doesn't move forward, he stays in a stationary position. The spirit of a myth is the first thing you imagine about and form a concept of a plausible reality out of something absurd when you first think about it.

What they did is totally not the original spirit of the myth as I still contend. Of course it's a no-brainer that the plane's overwhelming thrust will allow it to take-off in such a situation. Of course it's also a no-brainer that the plane will not take off if it remains stationary due to the conveyer belt moving many times faster than the plane, negating forward thrust (and melting off the wheels) since there will be no lift generated. So I guess this myth is more about method of execution rather than any actual real concept or genuine rational thought which is totally stupid.

They might as well put the plane in a windtunnel where the windspeed matched the forward thrust of the plane and see if it disintegrates.

[Sylvanfan]

Yeah, after I read the thread I understood the "myth" better and how the test would likely work I started to doubt my initial selection. Probably still would have voted that the air plane wouldn't take off just based on the fact that land is expensive and that it would have been studied by now to help better use land at air ports to handle more traffic (I know lame quasi conspiracy by me). I incorrectly assumed that it meant the plane would not be moving forward and that the treadmill would be acting as a force against the plan trying to prevent forward movement.

I guess we can expect to see a lot of land around Airports possibly go up for sale now and specialty conveyor Take off run ways to help with Air Traffic increases?

[Hack&Lube]

Originally Posted by Sylvanfan

I guess we can expect to see a lot of land around Airports possibly go up for sale now and specialty conveyor Take off run ways to help with Air Traffic increases?

See aircraft carrier steam catapault.

[Dan02]

Originally Posted by Hemi-Cuda

"The myth is that a plane on a conveyor belt will be able to take off"

so are there 94 CP members who were totally wrong, or just confused on the poll question as i was? i thought the myth was that the plan WILL take off (like the poll says) so i voted confirmed. but on the show they said the myth was that the plane WON'T take off, so in reality it's busted

i demand a repoll

Indeed poll is hella confusing, i haven't voted and looked at the poll and still don't know which way to vote.

[SarichFan]

How is a video of this not online yet?

[Bobblehead]

Originally Posted by SarichFan

How is a video of this not online yet?

Because it is copyrighted material and as soon as it goes on Youtube a take-down notice is issued? That would be my guess.

[octothorp]

Originally Posted by Hack&Lube

"The myth is that a plane on a conveyor belt will be able to take off"
-What do you think when you first read that line? When you imagine a plane on a conveyer belt you imagine a man running on a treadmill. He doesn't move forward, he stays in a stationary position. The spirit of a myth is the first thing you imagine about and form a concept of a plausible reality out of something absurd when you first think about it.

What they did is totally not the original spirit of the myth as I still contend. Of course it's a no-brainer that the plane's overwhelming thrust will allow it to take-off in such a situation. Of course it's also a no-brainer that the plane will not take off if it remains stationary due to the conveyer belt moving many times faster than the plane, negating forward thrust (and melting off the wheels) since there will be no lift generated. So I guess this myth is more about method of execution rather than any actual real concept or genuine rational thought which is totally stupid.

They might as well put the plane in a windtunnel where the windspeed matched the forward thrust of the plane and see if it disintegrates.

See, that's the problem: the myth is designed as a thought expiriment meant specifically to trick people into confusing 'the spirit' of the myth with what will actually happen. You can do all this physics and math, but it's really a philosophical question that comes down to one self-evident statement: A plane moving 25 mph on a conveyor belt moving 25 mph in the opposite direction will not stay in the same place. (It will move forward relative to the air around it at 25 mph and move forward relative to the conveyor belt at 50 mph).

[SarichFan]

Originally Posted by Bobblehead

Because it is copyrighted material and as soon as it goes on Youtube a take-down notice is issued? That would be my guess.

True

I've found it via other methods.

edit: Boooooooooooooooooooooooooring... It wasn't how I expected AT ALL. The plane was still moving on the freaking belt...

I wanted to see it stationary... and it wasn't much of a plane. It may have been a glider.

Lame..

[llama64]

Originally Posted by SarichFan

I wanted to see it stationary... and it wasn't much of a plane. It may have been a glider.

Lame..

Why would it EVER stay stationary? Seriously, try and explain how the plane would stay in one spot without it being tethered.