Can this airplane take off?

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I have another question.

If we assume that the plane does not take off, as there is no air flowing over the wings...

Now, we add a hypothetical giant fan at the front of the treadmill. This blows air at the same rate as the speed the aeroplane is going on the treadmill. Will the aeroplane be able to take off now?

(If so, will we soon see the USAF installing giant fans and treadmills to their carriers?)
 
But why would you need a treadmill, teeb?

The fan alone would have the same effect. Wether the wheels turn or not has no influence.


And once you leave the stream of wind generated by the fan you would loose lift, so not very useful I suppose ;).



The original question would have the wheels and treadmill moving with infinite speed (theoretically of course) and the plane taking of in the usual distance.

Think of the opposite, if you land your plane on a treadmill that is moving in the opposite direction with the same speed you are moving forward, would you come to a sudden halt once you touch the ground or roll out as usual (with added friction in reality)?
 
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Understanding that the wheels below me do not apply any force on my movement on the bike

Ah, but what about the invisible force that will hold you up for the sake of avoiding a paradox? :) (yes, I know, it will destroy the bearings first, but unfortunately you've chosen the undestructable ones)

Offtopic: This reminds me of the physics lecture I watched from Berkley webcast (brilliantly lectured by R. A. Muller, why don't we have such lecturers :(). He was describing superconductivity, explaining how electrons can only have certain energy levels, and how normally when electron travels through the solid it bangs into something and that changes electrons energy level. But in superconductor energy gaps are so wide, that no collision could throw an electron so far that it can reach another level. It will always end up in the gap. But gaps are not allowed. Therefore electrons don't collide :lol: Ok, maybe not everyone finds this funny, but I did :)
 
But why would you need a treadmill, teeb?

The fan alone would have the same effect. Wether the wheels turn or not has no influence.


And once you leave the stream of wind generated by the fan you would loose lift, so not very useful I suppose ;).

I have the treadmill in the experiment because I like the idea of a plane appearing to take off exactly on the same spot. If you had the fan and no treadmill, then it'd just be a normal takeoff, albeit presumably with a shorter takeoff length.

It is true that once outside the fan's influence the plane would plummet, so I guess we'd have to build the fan on a telescopic arm allowing it to extend upwards with the plane.
 
I have the treadmill in the experiment because I like the idea of a plane appearing to take off exactly on the same spot. If you had the fan and no treadmill, then it'd just be a normal takeoff, albeit presumably with a shorter takeoff length.

It is true that once outside the fan's influence the plane would plummet, so I guess we'd have to build the fan on a telescopic arm allowing it to extend upwards with the plane.

Nope, treadmill is still not needed :) If your airplane's engines still work that is. If they don't, and you only rely on the treadmill to keep you in place, your airplane will be thrown backwards when it starts lifting off :)
 
I have the treadmill in the experiment because I like the idea of a plane appearing to take off exactly on the same spot. If you had the fan and no treadmill, then it'd just be a normal takeoff, albeit presumably with a shorter takeoff length.

But it makes no difference. Imagine you have a kite but no wind. Would the kite fly if you run on a treadmill?



Say your plane takes of at 200mph. You set the fan to 200mph, set the engines to 200mph, release the brakes and you would start on the spot.
 
But it makes no difference. Imagine you have a kite but no wind. Would the kite fly if you run on a treadmill?



Say your plane takes of at 200mph. You set the fan to 200mph, set the engines to 200mph, release the brakes and you would start on the spot.

The treadmill is there solely to keep the aeroplane in the same spot.

Imagine I am running down the street at 5mph an hour, and there's a 5mph wind blowing at me. I'll still be able to make progress, albeit at a slower pace than 5mph.

Thus, if we have the plane going forward at 200mph and a wind of 200mph being blown at it, the plane would still move forward (as well as up). So the treadmill is there so that the plane, relatively speaking, is in the same spot.

If nothing else a plane is more aerodynamic than me running.
 
The difference between you and the plane is, and this is the key to the whole problem:

You are pushing against the ground to move you forward (so the wind (air) makes no difference), the plane is pushing against the air to move forward (the ground makes no difference).


In reality the wind makes it a bit harder for you, so you are slower and friction will slow the plane down a bit.
 
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Like it was said before, the engines act on the air, not the treadmill to push the plane forward. So the plane is moving through the air at the proper speed, even though the wheels are still, and when it reaches the right speed, it'll take off.

Now please, </thread>
 
The plane will take off. The people saying it won't are probably applying the method of propulsion of a car to a plane.

If you were to place a car in this hypothetical situation, it would not move. The treadmill is matching the speed of the tyres, a forward motion, with an equal backwards motion. Think of it as yourself on a treadmill in a gym. If you set it right, you, if you run at a constant speed, don't move an inch, forwards or backwards.

The plane, however, does not rely on the force of the wheels turning for propulsion. It instead relies on the thrust of the engines/propellers to provide the forward motion. This force is entirely independent of the speed of the ground passing below the thing it is attached to. The ground could be completely stationary, for all it's worth, and it wouldn't make a hint of a difference. As such, the plane would continue to gain airspeed, until it achieves enough lift to take off, (with some horrifically overworked landing gear.)

It's a similar concept to the reason why the plane doesn't lose airspeed as soon as it leaves the ground: The wheels do nothing to power the plane, they simply support it, and reduce the friction.

(Note: The above comes from a 16-year-old boy, who is a decidedly non-aerospace engineer, with a limited understanding of aerodynamics.)
 
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Nah, you just think logically, has nothing to do with aerospace engineering.
 
And to finalize that, the plane will take off, flip a taxi behind it, and make better waffles than Belgium.

:mrgreen:
 
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