747 on a treadmill conundrum..

[Jenny A]

To my mind the real question is if a plane has thrust from its jet engines but no forward movement through the air, can it take off? The treadmill is a silly way to ask this question because the plane's wheels have nothing to do with it's forward momentum except to reduce friction. In other words keeping a jet plane stationary with a tread mill is not really possible.

You might try to slow the plane down by adding friction breaks to the wheels or scoops on the floats of a float plane but even in the case of locked wheels scoops sufficient to slow the plane to a stand-still the plane would probably either just skid along the runway and/or treadmill or tear the floats off the plane.

If you tie the plane in place you've restricted it's ability to lift for reasons having nothing to do with the thought experiment, i.e you've tied it in place, though you could measure the amount of upwards pull on the ropes and thus get at the heart of the question which is whether the plane can take off with the jets running but no air flow over the wings from forward motion. Would the jet engines produce air flow over the wings without forward motion such as to cause lift? They do have to suck in air in order to propel air backwards.