There is a debate raging on another board I visit here is the topic:

A plane (747 passenger jet) is sitting on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the planes speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

The question is:

Will the plane (747 passenger jet) take off or not?

 

i say no, because there is no wind moving under the wings to create lift. remember airplanes run off of lift, not how fast the tires are spinning.

 

If I'm reading the question correcly, the plane is basically 'running' on a treadmill, right? If that's the case, then no the plane will not take off. Planes fly because more air is flowing over the wings than under. This creates lift. If the plane is not actually moving forward, then there will not be any air moving over the wings. No air moving = no lift = no flight. Of course, this is assuming that I correctly understand the question.

 

now if there was a biggo fan blowing air on in front of the plane then it could possibly take off standing still? (maybe)

 

Yes, it would, because no matter how fast the "treadmill" runway goes, the plane's wheels will spin just as fast.

The thrust from those 4 massive engines are what's propelling the entire airplane forward, no matter how fast or slow the "treadmill" runway is going.

From another perspective...if the runway treadmill direction was reversed, where the speed of the runway was kept constant to the forward speed of the aircraft, it would still take off due to the airflow over the wings (creating negative pressure or "lift"). The tires could be standing still in relation to the moving runway, it would still fly.

The thrust is what is moving the plane forward and allowing the wings to create lift. As long as there is sufficient forward motion to generate enough lift, it will fly.

The wheels rolling on the treadmill runway have no physical bearing on whether it will fly or not. As long as they are freely spinning, it doesn't matter how fast or how slow the treadmill moves...all that is relevant is how fast the wings are moving through the air.

 

With no airspeed it will not fly. The wings create lift by way of the airflow over them.

On anothert note; when you boil water just where do those bubbles really come from??

 

the airplane doesnt run off torque from the tires though it runs off of a jet so it could move no matter how fast the conveyer moves i think

 

Lift is generated by "relative wind" seen by the wing, in other words airspeed. Groundspeed does not matter. It will not fly.

Example: I am sitting on runway 25R at Long Beach in a Cessna 152. The tower reports temperature 15C, altimeter setting 29.92, wind 250 degrees at 10 knots, a 10kt headwind. VR or liftoff speed is 54kt. I firewall the throttle and accelerate to 54kt on the airspeed indicator, but the wheels are only seeing 44kt, below stall speed. If I pull back on the yoke will it fly? YES!

Jim

 

I think an easier analogy to understand is running on a treadmill. You are running in one direction, the treadmill is going the other. Even though you are running at 10 mph, YOU AREN'T GOING ANYWHERE! If you put your arms out like wings, there is no air speed.

 

I think the principals are being misunderstood by a few.

Forward speed, or simulated forward speed is not what makes a plane of any kind fly.
You can cut the wings off that plane and drive 400MPH up the freeway, it ain't flyin..
In the same vein, smaller aircraft need to be tethered down in stong wind storms, because the wind passing over the wings creates lift, and will move the plane.

In assuming that a plane could fly without generating lift (the only reason you need forward motion to gain flight), you are also therefore assuming a helicopter needs a running head start. Same principal, only difference is, the blades rotate to move air across them, creating lift.

EDIT: Here's a link that explains it, probably more than ya wanna read....
http://travel.howstuffworks.com/airplane.htm

 

No, no will fly.

Will the level of a lake rise when a very large bolder is thrown overboard from a boat floating on the lake?

If a tree falls in a forest when no one is around, does it make a crashing noise?

Why does water expand when frozen and steel contracts when cooled.

Can you break an egg in your hands when it is placed end to end between your palms and squeezing it with all your strength with your fingers locked, palms applying the pressure against the egg ends?

Lots of oddities of nature and unexlained events, but air speed has no correlation to landing gear wheel speed, but it definitely affects wing lift.

 

The wheels of the plane are not what move it the thrust does. Thus the plane would move forward creating the airflow to lift it off the ground. The wheels would just spin along. Imagine that instead of a treadmill the runway is a frictionless surface the plan still takes off. The wheels dont move the plane the jet engines do.

 

That one is actually quite easy to explain. It has to do with the molecular structure of the H20 molecule. When it's liquid they can slide by each other quite closely, but when it turns solid (freezes to ice) the molecules move into a rigid pattern where they are further apart than they would be in the liquid state, hence it gets bigger.

 

if a man says something in the woods, and no one hears him, is he still wrong?

HT

 

The question is incomplete, therefore it cannot truly be answered.

Is there any force acting on the plane to actually keep it from moving forward?

When the planes engines are throttled up, it is the thrust itself from the engines that make the plane move forward, not the rotation of the tires. The tires rotate in order to allow the trust to move the plane easier.

Unless there was an outside force holding the plane in one position relative to the world it would still move forward as the engines were throttled up. Try sitting in an office chair and spraying a fire extinguiser away from you.

The only way that the "treadmill" could keep the plane from moving relative to the world would be for it to spin so fast that the force created by the friction in the wheel bearings would be equal to the force that the engine thrust would be putting out. This would pretty much be impossible. Theoretically though, if you could keep the plane stationary in relationship to the earth, no it would not fly.

This of course is assuming that the engines do not have enough power to force enough air over the wings to create lift without the plane moving.