Physics

[Oni]

Imagine a 747 is sitting on a conveyor belt, as wide and long as a runway. The conveyor belt is designed to exactly match the speed of the wheels, moving in the opposite direction. Can the plane take off?

My theory is No it can't. A plane requires air flowing under the wings to create lift (if I am correct), so therefor if the plan is stagnant then there is no air flow under the wings, there for no lift. Lift is created by the negative pressure under the wings. Hense the curve on the underside of the wings, or why the top of the wing is curved. so there is a less air traveling under the wing than over... I am sure my concept is flawed but I think the basics are there.

what do you guys think?

[Oni]

It's weird I post a good thinking question and no one cares. LOL. I even came up with a decent theory.... and the smart people dont even look at it. ...
So I can only surmise that I am right.

[Taylor-MadeAK]

No, the "smart people" looked at it alright, but if they're anything like me they're not going to attempt to discuss physics with you.  Why?  Do you remember the time I tried to explain Einstein's Theories of General and Special Relativity to you?  That's why.

[Oni]

ya that was one of the times i feel asleep tlaking with ya. lol.

[Oni]

* Oni C@ pulls out two sticks and starts rubbing them together

I will make flame from this if its the last thing I do.

<a href="http://www.youtube.com/watch?v=YORCk1BN7QY" target="_blank">http://www.youtube.com/watch?v=YORCk1BN7QY</a>

[Taylor-MadeAK]

Can't call it "busted" because the "conveyor belt" wasn't moving at the same speed as the aircraft.  It doesn't even matter where the engine sends the power, the broken concept here is that it takes time for a vehicle to get up to speed.  The pickup truck that was pulling the "belt" in that video would take probably 30 seconds to get up to 60 MPH under load (the load being the tarp with the plane sitting on it).  That aircraft (Piper Cub, right?) has a top speed of 113 knots, or 130 MPH, and can reach that top speed in under 15 seconds with the throttle wide open.

There's no way that truck got anywhere near 60 MPH - let alone 130 MPH - before that plane's wheels left the ground.

The experiment was fatally flawed in that the equipment wasn't up to the task that it was put to, therefore the data is invalid.

Now, if you want to do it right, there are a couple variables that need to be covered:

• In order to generate lift, an airfoil needs to have air moving past it.  A forward-prop aircraft will push air past the wings just by having its engine running, generating a small amount of lift.  Rear-prop and jet aircraft do not have this advantage, and that's desirable for an experiment because once an aircraft has any kind of lift nothing will stop it from moving forward.
  
  
• If you really want to put a plane on a conveyor belt or treadmill, you need to have some way of driving that device at a speed and acceleration that matches the aircraft that you're experimenting with.  A truck pulling a tarp just won't cut it.

The "Myth Busters" experiment didn't deal with these variables in a reasonable manner, therefore their results are suspect.  QED.

[Oni]

Course that does leave the theory that a Piper Cub could do it but a plane with the prop on the back could not. Because the Cub is creating wind flow over the wings. That would be why on a windy day you can get a virtical take off with cubs.

[Taylor-MadeAK]

Yes and no.  If you engage the landing gear brake on a Piper, is the prop backwash alone enough to lift the plane off the ground?  If that were the case, Pipers would be capable of VTO, and we all know that simply isn't the case.  I only referred to the backwash issue because it helps facilitate forward movement by creating a minute amount of lift on the wings.

The Mythbusters experiment is invalid simply because their "conveyor belt" wasn't physically capable of moving at the same speed and acceleration as the aircraft.  Nothing more, nothing less.