24th May 06 at 18:59

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And since there is no air flow over the airfoil (wind or realitive wind), there is not lift. quote]

For Lee.

Everyone is convinced the plane would not be moving forward. Hence they think it won't work.

It's simple maths. This is not a car, it's a plane. The conveyor can be miles and miles long.

Question says Conveyor goes same speed as plane but in reverse.

The above questions say the plane would be stationary, hence no air over wings. So what speed is the conveyor going when the plane is stationary?

Plane speed forward = 0. Conveyor speed backwards = 0.

So straight away the picture in your head of a plane sitting on the spot with a conveyor underneathe whizzing past is complete crap. As if the plane is not moving, the conveyor will be stopped too.

Now simple physics, to get an equilibreum - you must have 2 equal forces acting against each other.

So you have the force of the engine's going out one end 26400 lb ft. What force do you have acting against it at 0 mph?

0. So at the start the conveyor is stopped and the plane moves forward. Now when plane is @ 1 mph MOVING FORWARD, conveyor is going backwards at 1 mph, 10 mph forward, 10 mph backwards etc.

Now, since the wheels will just spin on a plane (same as steve's example of holding a toy car on a tread mill - there are no or very little forces actually pushes the plane backwards. The only forces acting are resistance forces with the wheels and bearings, so you could say due to weight and gravity down on the wheels if you switched on the conveyor and there was no thrust of the plane the plane would go backwards.

however, due to the question - the conveyor would not be on if the plane is not moving, and thus wouldn't send the plane backwards.

Too many people are thinking there's some equilbreum at force acting equally towards the thrust of the plane - thus the plane is not moving forward. But where is this magical 26400 lb ft of force coming from to hold the plane where it is? against the engines?

the conveyor belt will only make the planes wheels spin, possibly effectively pushing the plane backwards only a 10th of the force of the conveyor belt.

It's quite possible for a plane to take off at 180 mph, (say the conveyor belt then has to go 180 mph in reverse) the force against the plane will still be far less than the 26400 lb ft of thrust pushing out the back of it. If this is the case the plane will move forward.

HELL if the plane was on skies, and the same rules were applied, I think the plane at full thrust would still be able to power along the long long long long conveyor belt and take off - it may take twice or more length of a normal runway - but still would accelerate.

24th May 06 at 19:08

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Originally posted by Paul_J

quote:

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Originally posted by LiVe LeE

Providing the plane moves forward at a fast rate, it will get lift and take off.

IT can't take off straight away as you say, as it'll be too slow for enough lift.

say 180 mph FORWARD? So even with the treadmill stuck at 180 mph in reverse. the force pushing the plane FORWARD - will get the plane to 180 mph eventually.

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What i think your missing Paul is the plane will not be travelling forward in a sense, it is stuck on the spot. Because whatever speed the engines are putting out, the converoy belt matches