Quote Originally Posted by Hotboat View Post
Aircraft (prop or jet) generate thrust. They pull themselves through air. Bernoulli's principal and the wing allows them to fly.

The speed the wheels are turning or the direction they're turning is irrelevant.
Well, lets look at it from a different direction. Lets look at the landing gear as being the same as roller skates on your feet. If your on a treadmill with skates on, the only way you can move forward is by holding onto a stationary object. I.E. and handle bar, or a rope. Otherwise, you might roll back, actually. That's what the air is for the plane. It's a rope or stationary object that it grabs onto and pulls itself forward, unlike the tires on a car for instance. Which lets it move forward regardless of wheel speed. Right? Sorta. As you move forward, the treadmill speed increases, meaning you have to work harder to keep moving forward due to increased friction between the wheels of your skates and the treadmill. As the speeds increase, so does the strength needed to pull yourself forward. Sooner or later, it's just too much work, and you stop moving forward. This is the same with the plane, it can only pull forward so hard, and then that's it. Same here. Everyone concentrates on the wheels, and not the forces themselves at work here. The wheels are only the instrument with which the engines transmit thrust into movement. They are not powered.