Bigtank52,

It's got a LOT to do with it. It proved that the plane will MOVE even if the treadmill matches the take off speed.

That toy plane moves forward and backward on that treadmill set to speed. That proves that the speed the tires are going doesn't mean anything when it comes to moving the plane.

You can't keep a plane stationary on a treadmill if you're trying to take off. Now, if you're PURPOSELY trying to keep the plane stationary, you could - but that's not what this is about, is it?

Here's the search string for the youtube videos on "plane on a treadmill"
http://www.youtube.com/results?search_query=plane+on+a+treadmill&search=Search

MythMod

Let me try to explain this slowly: If the aircraft does not appear stationary then the speeds are not matched.

Wow, exactly as predicted. All these new "yeah, but, but, but,....... it's just, they,.... didn't test it right" is sour grapes. Myth busted. These silly rebuttals arguments defy physics and miss the point of the myth. The plane flies. Period.

The myth has been going on for a long time and has many misinterpretations. One of them is the "same speed" take which is arguably not even possible. The myth is not that they match speeds - obviously if the belt and plane's wheels are at the same speed the ground speed and therefore airspeed will be zero - plane can't fly.

But as has been demonstrated and discussed in hundreds of threads, the belt CANNOT PREVENT forward movement of the plane - therefore airflow - therefore flight.

Some people here are badly confused. There is absolutely nothing a conveyor belt can do that will keep a plane stationary. Nothing. The ground is irrelevant. The plane will take off, regardless of anything the conveyor belt could ever do.

Now, there are certainly things that can be done with air to prevent a plane from taking off - but a conveyor belt is NOT air. The conveyor belt does NOT affect airflow over the wings in any way.

Ok, for all the people that say it was done wrong because the plane moved forward.

Please answer this.

How fast do YOU think they would have to pull that conveyor in order to actually STOP the planes motion???????? 100mph? 200? 300?

noone ever said the plane was just going to lift up into the sky because a conveyor was moving under it. They said YOU CAN"T STOP THE PLANES MOTION with a conveyor belt.

Okay, ONE last time.

The Mythbusters tested it correctly.
What YOU guys want, is to make the testing give yout he result you want. The idea behind testing to to see what the answer is, not to formulate the test to give you the result you want.
The treadmill CANNOT negate the forward motion of the plane. You might as well glue it to the ground, and declare yourself right. A treadmill CANNOT negate the plane pulling itself forward by the propeller. It's impossible in real world physics, get over yourselves.
Since not one person can read, and only wants to WHINE about how it must have been done wrong, since they didn't get the result THEY wanted to see, and not one person wants to admit they are REWORDING the myth to suit themselves, I won't bother explaining it again.
Read ym first post in the thread, that expalins you guys would start whining as soon as you were PROVEN wrong.
MYTH BUSTED!! Go guys! Great test. The plane TOOK OFF. The treadmill went FASTER than takeoff speed, and the plane TOOK OFF.
So you guys whining are all WRONG. Get over it. But since you won't just admit it, and want the universe to rearrange PHYSICS to suit your preconceived notion, you can have the thread to congrat yourselves on thinking you can fight physics.
You want it, YOU go do it yourselves.

This was a huge oversight! The ground camera clearly showed that the plane had forward motion. Anyone that knows anything about how a plane flies knows that the wings must have air flowing over them in order to produce lift. Spinning the wheels does nothing to produce lift. The experiment proved nothing. I don't know why the pilot didn't contest the validity of the test!

They changed the wording of the Myth for the show, because the original question is flawed. The problem is that the whole reason for all the discussion is because of the flaw in the question.

"This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in opposite direction)."

The conveyor they used did not do this, it simply moved at about the takeoff speed of the plane. Unfortunetly the behavior described in the quote isn't possible because of the thrust of the propeller, as Jamie and Adam explained at the end of the show.

The tarp matched the speed if the airplanes body, not the wheels. Airplane speed is measured in airspeed, not wheel speed. Why would the Mythbusters try to match the wheel speed? The myth says nothing about matching wheel speed.

The problem with this myth is more with the explanation of what the myth really is. I just watched the episode and was really angry at what I thought was a horrible perversion of physics, but then I just realized that they weren't explaining the myth well.
I thought they were saying they would move the conveyor belt and then attempt to keep the airplane stationary relative to the surroundings and at takeoff speed relative only to the belt. That obviously would mean zero indicated airspeed and thus zero lift (other than the slight amount caused by the propwash over the wing roots).
What they really meant, but failed to explain, was they would move the belt, but allow the airplane to move relative to everything. This makes it simple to conceptualize how it works. Airplane flight is simple vector addition. Thrust vs. drag and lift vs. weight. For this myth, induced vs. parasite drag is irrelevant, so let's look at the physics of how the takeoff roll progresses. As the pilot applies max power with the brakes held, the prop produces its maximum thrust, then at the moment of brake release the "drag" is just the inertia of the mass of the plane trying to stay where it is (relative to the earth, regardless of what it's resting on). As it accelerates, the inertia changes, rate of acceleration slows due to the addition of parasite and induced drag. The effect of placing the airplane on a belt is just that the engine has to counter the additional rotational inertia of accelerating the wheels to twice their normal ground speed, as well as the additional drag from the wheel bearings spinning twice as fast.
If all that didn't make sense for whatever reason, just think of it in a different context: floatplane on a calm lake vs. going upstream against a river current. Going upstream the aircraft engine has to produce enough thrust to overcome the resting inertia of the mass of the aircraft + the drag of the floats in the water AT DOUBLE NORMAL TAKEOFF SPEED + induced and parasite drag.
Bottom line, I think all of this "controversy" is merely caused by a poor explanation of constraints of the myth. Anybody agree?

The plane moved forward. It was beyond the cones when it took off. The plane was accelerating faster than the treadmill was moving...thus it had airflow over the wings, which provided the lift for take-off. Most aircraft cannot accelerate straight up...they need airflow over the wings to to produce "lift". Only a few, mostly military and acrobatic aircraft...and most R/C models...can accelerate vertically...which means the thrust is overcoming the weight. Do this "busted" myth again with a camera placed 90 degrees from the plane. Keep the plane in that position and pull the conveyor belt as fast as you want...the plane won't take off. The propeller won't produce enough airflow over the wings to produce lift.

quote:

Originally posted by mitchio83:
Im really dissapointed at the "no flys" here. I havnt seen one person admit they were wrong. What "Greatnt249" said is exaclty right, the results didnt go your way, so you say "the results were not what i expected, therefore you did it wrong"

What part of "A treadmill cannot hold an airplane stationary" do you not understand?

Imagine this you "no flys"

If they myth was "can airplane is sitting on a cd player playing a song at the same tempo as the mph of the airplane, can the plane take off?"

They test the plane on a cd player myth and it takes off, but you "no flys" say "But the tempo of the song didnt hold the plane stationary like i thought! you did it wrong!"

Same scenario here. a treadmill does not have the capability to hold an airplane stationary.

So what you are saying is a plane has enough thrust to make it move faster than a conveyor? IF it did not, then all planes in the world would rev their engine and stand still. Never being able to break free from the starting friction. This would be just about as bad of a myth to test as the one actually aired. Of course the thing can go faster than the conveyor, other wise all airplanes should be called stationarycrafts...

To the no-flys:

SPEED DOESN'T MATTER!

It seems that many, many people misinterpreted what this puzzle was about, and will never believe any experiment that proves their preconceptions wrong.

Don't you think the conveyor belt, even if improperly executed, would have had SOME effect on the takeoff? It had exactly NONE.

It's a good thing planes never try to take off facing west, while the earth rotates 1000 miles an hour underneath them.

Oh wait...

Helifly83

The classic wording of the physics question doesn't state the plane had to be stationary. It just says it needs to match the speed of the wheels.

MythMod

Wolfy-hound + +

if the conveyor belt were going at the same speed it will not take off put some head wind infront of it for drag to simulate it going down the runway and the plain will not go noware .........................

I was always part of the "it will fly" club. The mythbusters set it up correctly and came to the right conclusion. Here is why some people get confused.

It all comes down to the frame of reference. When comparing the speed of two seperate objects, you must have a common frame of reference. If two cars are traveling side by side on a road at the same indicated speed on their speedometer's, then they are traveliong at the same speed relative to the ground. But relative to each other, they are traveling at 0 MPH. If they are traveling in opposite directions at the same indicated speed(say 50 MPH), they are traveling at that speed relative to the ground, equal speed but in opposite directions. If you compare there speeds relative to each other, they would be traveling at twice their indicated speed, since they would be moving away from each other at 100 MPH.

The myth as stated says that the plane and treadmill are traveling at the same speed, but in opposite directions. Their common frame of reference would be the ground since it is independant from each. So the belt would travel at say 25 MPH one way, and the plane would move at 25 MPH the other way, both going down the runway, but in opposite directions. Since the wheels of the plane are not powered, they are free moving, they will not be affected by the backwards motion of the belt. The plane will be able to move down the runway, being pulled forward by the prop, and when it reaches a speed of 25 MPH(with the belt moving 25 MPH or more in the opposite direction), the planes wings will be moving fast enough through the air to create enough lift to allow the plane to leave the ground, and takeoff.

quote:

Originally posted by idoubtit:
Let me try to explain this slowly: If the aircraft does not appear stationary then the speeds are not matched.

You obviously don't understand the physics at work. What you describe is impossible. A conveyor belt cannot cause a plane to remain stationary. It doesn't matter if the accelerations are matched or anything else. It simply can't be done.

i already posted once, but i want 2 do one more just to say the mythbusters did a great job. i cant believe how many people watched the show and still dont get it. the myth wasnt "can a stationary plane take off" it was "can a plane on a conveyor belt take off" im a huge fan of the show and i want 2 say again, great job guys and i cant wait for all the new episodes.

p.s. looks like u got through that rights battle with macguyver. bring em on haha