Geeeeeeeeeez guys were still going on and on and on and on and on about this!?!?! I think we're all just going to have to agree to disagree on this one.





P.S- THE PLANE WON'T FLY!


P.P.S- I didn't see the mythbusters lastnight because it's on at different times in Canada, what happened?

 

well im not licensed but i am a student pilot.


it wont fly

 

I'm confused. If a plane lands on a treadmill that is rotating at the same speed as the airplane's ground speed, will the plane instantly stop, or instantly double it's speed?

 

A propeller corkscrews through the air, pulling the engine and its connected aircraft forward until sufficient air speed is attained for lift. A jet engine's exhaust thrusts against the air, pushing the engine and aircraft forward for the same result. The wheels merely support the craft until the lift is attained. The wheels do not supply any energy to the plane, and do not contribute to its lift (which means also that they do not hinder its lift).

 

will somebody just post the mythbusters results finally. Dan

 

Here's what I think will happen...I think the plane will stay grounded, and the treadmill will take off in the air...

Oh, and I'm not a pilot, but I did stay in a Holiday Inn last night...

Tim

 

I don't think that we will find out from Mythbusters....at least I am watchin it now and they ar enot covering this issue at all.

 

THe plane will take off for the fact that wheelspeed is not what causes takeoff. It's the thrust from the propeller that will pull the plane forward and take off.

 

Wow I must be insanly slow or something because I finnaly figured this thing out it won't fly, now if only it was possible to change my vote

 

but, if the wheels are connected to something causing the air speed to go reverse of what it needs, then first the plane needs to overcome that reversed air speed. if the plane can not go fast enough to over come the reversed air speed, it will not lift off the ground.

at least that is how i think of it.

 

Two answers:

If the conveyor belt has the ability to impart an opposing force to the forward movement of the plane, and hold the plane stationary, it will not become airborne.

If the planes forward movement exceeds the opposing force of the conveyor, and gains sufficient air speed it will become airborne.

The question then becomes:

Does the conveyor have the ability to create this opposing force?
A Boeing 747-8 weighs 485 tons. It has 18 tires. The tires are 4 foot tall. Width I don't know, but they are wide. Tremendous rolling friction, especially at speed. Add drag from brakes, bearing friction, gravity, etc., and you have one hell of a mass to overcome for the plane to move.

If you start the conveyor without the planes engines creating an opposing force, the plane will travel with the conveyor. If you want the plane to remain stationary, the plane will have to be tethered. This is indicative that the conveyor is creating a force against the wheels of the plane pulling it in the same direction as the conveyor.

My question then becomes how much drag can be increased by the conveyor speed, if any, before it is overcome by the forward motion of the plane. This is the unknown factor. Guesswork doesn't count. I know the plane can fly if it has sufficient air speed, what I don't know is if the conveyor can increase the drag sufficiently to hold the plane stationary, and for how long. jd

 

Is this really just semantics, or rather, a poorly worded challenge? There are assumptions which need to be stated before an answer can be agreed upon, such as what if any are the maximum rpms/speed the wheels can turn and what is the maximum takeoff thrust/speed of the airplane?

A quote from a comment on the video:

"The treadmill means nothing as the plane is not driven (me: "powered") by the wheels but by the force on the air around it by the engines. The air is the same if it's on the treadmill or not and so the plane will move forward and take off. The wheels will just be revolving twice as fast as they would normally be revolving."

This statement assumes the wheels can roll fast enough and the thrust is adequate to overcome the treadmill AND provide forward motion to the airmass.

So as I understand it, think of a seaplane taking off on a river, moving upriver. The river can be seen as analogous to the treadmill. If the plane can reach a speed fast enough to overcome the friction of the water AND develop enough forward motion relative to the air developing flow over the wings, then it will take off.

But if the current is fast enough, no go...unless the plane tries it downstream.

 

that would be one heck of a treadmill.

i can not see people on the mythbuster scale actually building one to test the debate correctly.

even if it is just some small prop plane or something, just the mechanics of it would be an undertaking for a show of their size.

 

Use a model airplane on an oversized treadmill.

 

Can we agree on this:

Insufficient airflow over the wings = no flight.

I think in the original proposition, the treadmill was supposed to negate any forward motion of the aircraft. If there is no forward motion, there is insufficient lift generated. Therefore, I stand by my answer that it will not fly.

So does the treadmill negate forward motion and thus lift?