I still stand by my original post. No where does the riddle say the aircraft is even running. It says it is "standing". If it is standing, and the conveyor moves according to the planes movement - then nothing is moving - the conveyor or the plane.

It will never move - as soon is movement is detected the conveyor moves keeping it back zero point. So the conveyor would crawl at a barely detectable speed.

The better way to word the riddle would be to ask if a plane landed on a conveyor the length of the plane running at the same speed as the ground speed of the plane - would the plane run off the conveyor?

Yes.

Its all about wind speed over the wing. Everything else is irrelevant.

But to take off its True Airspeed has to match its TakeOff speed....




No - the riddle says - "This conveyor has a control system that tracks the plane's speed and tunes the speed of the conveyor to be exactly the same (butin the opposite direction) instantly."



To get to sufficient air speed the plane needs to move through linear space for air to pass over the wing (assuming no wind) If the conveyor negates any forward movement of the plane it is not moving through space. The engines are producing thrust, but the conveyor is the one consuming this work - not the plane.



ARGHHHHHHHHHHHHHH! How can it move forward if the forward movement is matched with equal and opposite movement from the conveyor??

I have 20HRS solo time. So you can't argue with me <img src="/forums/images/graemlins/lol.gif" alt="" />

Because it is NOT attached to the conveyer. the wheels provide minimal rolling resistance. The conveyer CANNOT tether a plane by its wheels.

The conveyer can match speed of the plane, but it will have 0 effect on the plane.

OK, If I'm running on a treadmill, and the treadmill is matching the speed at which I'm running then I don't move.

Now, lets say that I decide while I'm running, that I want to "walk" down the handrails using my arms. Does it matter how fast the treadmill and my feet are moving? NO.

The plane is not moving because of it's wheels, it's moving because of the engines acting against the air.

So I was right with my initial idea, it won't move, right? LOL <img src="/forums/images/graemlins/lol.gif" alt="" /> <img src="/forums/images/graemlins/lol.gif" alt="" /> Frank or Eddy will have to build us a giant treadmill for testing.

NO NO NO Yes it will fly people.

My best example.

Go buy a cheap RC plane at Harbor Freight. On a windless day, run the thing at full throttle, hold it above your head and let it go.

You should probably bring bandaids.

You have to THROW it or run with it. So that the velocity of wind over the wings matches its takeoff speed. There has to be forward motion through linear space for the air to move over the wing.

It is attached figuratively speaking, by gravity until its take off speed (airspeed over the wing needed to produce lift) is reached. On a windless day, ground speed will have to match T/O speed (or more precisely TAS required for takeoff) for the plane to take off since the air is stationary. In this case, ground speed is zero.

Any forward momentum from the thrust, is negated by an equal and opposite momentum of the conveyor. We need momentum to move the plane through linear space so that air can move over the wing. It aint going anywhere. And if it was calibrated exactly, you would hardly see the conveyor move.

I am going crazy <img src="/forums/images/graemlins/zombie.gif" alt="" />

But the wheels aren't driven! They're just big casters basically. The force of the conveyor only spins the wheels. The thrust of the plane acts on the air and propels the plane forward. The conveyor has no impact on the relationship between the air and engines.

This is a good brain teaser. After thinking about it for a while I think I was originally wrong, and that if the treadmill was the length needed to take off then the plane will get in the air.

If it doesn't blow up the landing gear first!!! <img src="/forums/images/graemlins/scared.gif" alt="" />

So, back to my point...

Then why is the treadmill system not employed at airports or aircraft carriers? Or is this treadmill infinitly long or just as long as a normal runway?