Plane on a treadmill .. to be on Mythbusters

[omgwtfbbq]

Sqrl said:

omgwtfbbq said:
you're all getting it wrong! you're all saying "if the plane has no airspeed it won't fly" which is of course true, but you're missing the point that they're trying to slow down a plane with a treadmill. It simply won't work! The plane is pushing against the air. If it were a car it would be stationary. Imagine this scenario then:

You have a car driving at 100 MPH. It's a front wheel drive. The two back wheels are on a treadmill (ok, you'll have to imagine a mobile treadmill here so that the back wheels are on it and the front wheels aren't) and this treadmill is going backwards at 100 MPH. Will the car stay stationary? Of course not! The front wheels are providing the force, the back wheels are simply there for the ride. It doesn't matter how fast those back wheels are spinning, the front wheels will keep the car moving at 100 MPH.

This is the exact same scenario. The plane will move forward because no treadmill in the world can stop a plane from moving.

I don't think anyone is arguing if the plane's own motive thrust can overcome the treadmill. What we are saying is that the myth seems to prescribe a plane that cannot move. By the rules of the myth it's only ever allowed to provide itself enough thrust to overcome the backwards thrust produced by it's wheels friction with the treadmill. And thus no airspeed is obtained and thus no lift.

If you put a plane on an infinite treadmill going to the left at 200mph and let the plane get up to 200mph due to the friction on it's wheels, theorotically it would still be able to overcome this with its own motive thrust because its motive thrust is based on relative windspeed and is limited by such. Therefor it would be able to slowly speed up and overcome the leftward 200mph thrust until it reached a speed vector of 0. At that point the wheels would be rolling along the belt at 200 mph, but the plane relative to the earth would still be moving a 0mph and the same would be true of the airspeed over the wings. Thus no lift here.

Now since the plane's motive thrust is limited by the relative airspeed , which is currently at 0, it is capable of continuing to speed up and taking off on the treadmill if it should choose to do so.

But as I said before the myth is poorly worded and I don't think anyone here can really claim to have the absolutely correct interpretation of the myth. I really hope they do a better job of explaining the myth on the show, but in the meantime I have double checked my season pass and am looking forward to it =)

@Bod, thats pretty much what I said in my first post also =)

you are correct. If they do this, the plane won't take off. But I'd be very impressed if they manage this, though. I suppose they could move the plane at minimum speed, and then slowly increased the speed of the treadmill until the friction in the wheels stopped the plane moving. But this is a ridiculous scenario, because the plane won't take off without the treadmill, of course putting a treadmill underneath it won't change anything.

This whole scenario is stupid. The treadmill quite smply will not make any difference at all to whether the plane will take off. If a plane uses its full thrust to accellerate, then no treadmill in the world will stop it. If it doesn't, then moving a treadmill BACKWARDS will certainly not help it take off. In the end the treadmill does absolutely nothing to stop or help a plane take off.

I suppose it would be more interesting to see whether a treadmill can actually accellerate a plane enough to get it to lift off