will it take off?

   / will it take off? #1  

schmism

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Sense we were having so much fun debating the finner points of tire pressure in the other thread....

i thought this would be kinda fun...

a plane is standing on a movable runway( something like a conveyor).as the plane moves the conveyor moves but in the opposite direction.the conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

the question is

will the plane take off or not?

(ps its been debated to death on other forums, its always fun to see how people present the theory behind there answer)
 
   / will it take off? #2  
Since there is no relative motion with respect to the wings and the surrounding air, there is no lift. All you do is wear out the tires!
 
   / will it take off? #3  
Conventional aircraft, normal wing, no forward motion in relationship to the air?

It will sit there and make a lot of noise,

At least until the wind blows across the wing enough to provide lift (be a lot of wind) at which point,,,, hmmm I think it would then rapidly accelerate being "disconnected" from your treadmill.
 
   / will it take off? #4  
I'm no aeronautical engineer, but it seems to me that what propels the airplane is the prop which is really pulling the aircraft forward through the air. The landing gear can spin as fast or slow as they want with little effect on the actual speed of the aircraft. I guess there might be some drag associated with friction on the bearings, but I would think that would be minimal. The conveyor would only have a negative affect if the airplane's forward movement where controlled by motors driving the landing/running gear.
 
   / will it take off? #5  
I'll play along...

The plane will take off and the plane's wheels will be spinning at twice the normal speed at that point.

The conveyor (runway) is dealing with ground speed and the plane needs airspeed to take off.
 
   / will it take off? #6  
This has been beating to death way too many times.

The plane will take off. The plane does not move by force of driven wheels (like a car). The plane uses thrust from the jets or props that propel the plane forward. Therefore, the conveyor belt can be spinning at 100mph and all that does is spin the free rolling wheels faster than the plane.
 
   / will it take off? #7  
Dmace said:
This has been beating to death way too many times.

The plane will take off. The plane does not move by force of driven wheels (like a car). The plane uses thrust from the jets or props that propel the plane forward. Therefore, the conveyor belt can be spinning at 100mph and all that does is spin the free rolling wheels faster than the plane.

Darn, your right, I am visualizing the plane remaining motionless with regards to forward air speed, but that would not be the case.
 
   / will it take off? #8  
plane moves the conveyor moves but in the opposite direction.the conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

If the plane is actually moving, that means air is moving over the wings, so yes it will lift off. Now the wheels will be moving twice as fast as normal because they will be rolling their normal speed plus the speed of the conveyer belt. The key here is the plane is moving.

Edit: Daggone, when I started typing this up. Nobody had responded and then people stopped by the desk and I actually had to work for awhile and then all of these responses.....
 
   / will it take off? #9  
schmism said:
the conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

Actually, this sentance is not clear enough to draw a conclusion. It seems to imply that the speed of the conveyor belt is sufficient to keep the plane fixed in a single point in space (it says it matches the speed of the plane, not the ground speed of the landing gear tires). This is nearly impossible, but that is what is tripping people up. It would take a lot of conveyor belt speed and very inefficient wheel bearings (etc) to achieve this but the sentance is not clear enough to rule this out. If the belt were capable of doing this, then the plane would not take off. It also does not specify the type of landing gear. Some planes have skids for landing gear and/or tail wheels.:rolleyes:
 
   / will it take off? #10  
Yes, Because there is a head wind created by the conveyor belt. Its a function of the Reynolds number and it is called ground effect.
Did I get you... cause I just made that up.
 
 
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