747 on a treadmill conundrum..

[Jenny A]

They will result in some drag because their bearings are not totally frictionless. But wheel drag will be negligible next to the thrust of the engines, or the aerodynamic drag on the aircraft resulting from forward motion. So the wheels will have little effect whether it is rolling on the treadmill or a concrete runway.

The rated speed of the tires are a concern. Airplane tires, like car tires, have a rated speed. Putting the plane on a treadmill will cause them to roll twice as fast as normal and likely exceed rated tire speed. I don't know how long they will last and whether they will survive one complete take off run. But I don't think this kind of detail is what the original puzzle was getting at. The original puzzle was about pulling the leg of people who don't much about how aerodynamic flight work in principle.

Or what causes the plane's forward propulsion for that matter. I thought about this this morning in terms of the Kitty Hawk planes that were pedal powered, but since the peddles turned the prop not the wheels, the problem remains the same with regard to the treadmill.

It's speed relative to the air not the ground that matters for flight. If you don't believe it all you have to do is think about how an airfoil kite flies. It's not going anywhere relative to the ground, but wind-speed lifts it and keeps it aloft and drag from the string hold the angle of attack. http://en.wikipedia.org/wiki/Foil_kite