(September 6, 2014 at 5:01 pm)pocaracas Wrote: Even if the plane starts from a resting state, the treadmill should not influence the motion of the plane through the air, because it will just cause the wheels to spin twice as fast. Yes there will be a grater drag force, keeping the plane attached to the treadmill, but remember, the treadmill will only move as fast as the plane, never faster. The plane will never go backwards, due to the treadmill. So, sooner or later, the engine's power overcomes the ground drag force and the plane moves forward through the air.
The treadmill will influence the drag on the plane. It will blow the tyres up if they spin too fast.
As I said in a previous post, if the treadmill has to try and match the speed of the tyres, it will rapidly tend to an infinite speed, not just double. As per previous post:
1. Plane starts to roll down the treadmill. Wheel speed is say 1mph, treadmill is zero.
2. Treamill reacts by rolling 1mph backwards.
3. Since they are in contact, this must increase the wheel speed.
4. Which in turn means the treadmill must again try and match the speed.
5. This loop rapidly reaches a speed that will blow the tyres up. Even if they don't blow up, the friction increase will be enough to sttop the aircraft.
If however the treadmill starts at a backwards speed of Vrotate (the speed the a/c lifts off) and maintains this, the aircraft will probably take off fine as long as the tyres can handle it. In this case the maximum tyre speed is 2*Vrotate.
