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  #11  
Old 11-23-2005, 06:57 PM
d10 d10 is offline
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Join Date: Jan 2005
Location: Ft Campbell, KY
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Default Summary of this thread

Once we established the fact that lift requires forward airspeed (real aircraft take off at 0 KIAS btw, rotary wing >>>>>>>>>>> fixed wing), and that prop wash != airflow capable of producing lift, everyone seems to be on track, but it seems this argument will continue forever because the question posed can not ever occur, even in theory, once you assume that thrust from the engines will produce forward airspeed.

Group 1, led by OP and Patrick seem to be completely ignoring the fact that if the aircraft starts to move forward, the speed of the wheels will increase, which by definition means the speed of the treadmill must increase, which by definition means the speed of the wheels must increase, etc. It seems they're taking the situation as posted, then thinking about what would happen if you added thrust to the aircraft, and then not really caring about the fixed relationship between the wheels and the conveyor anymore. Basically these people are thinking of what would happen given the situation as posted as an initial state, and then thinking of what would happen in the real world based on physics, despite the fact that what would happen deviate from the rules of the OP.

Group 2 can't get around the fact that the OP states there is in fact a fixed relationship between the conveyor and the wheels of the aircraft. They realize that the only way to solve the equation of X=X+Y, where Y is the forward airspeed, is if Y=0. For this reason, they assume that the forward airspeed must in fact be 0, and therefore lift is impossible.

I have yet to see Patrick answer the question of how the forward airspeed can be anything but 0 while still maintaining the direct relationship of the wheels and the conveyor. I suspect that his ownage in the works will also ignore this.

This question is horrible, and probably designed to create confrontation just like we have here. The answer depends entirely on if you want to think in terms of the rules posted, or think in terms of what would be possible in the real world ignoring the rules (assuming that this set up is possible to begin with). Everybody realizes that if you take the OP as an initial state, and then accelerate the aircraft, allowing the wheels to spin faster than the conveyor, you could move the aircraft forward and take off. Everybody should also realize that moving the aircraft forward will move the wheels faster than the conveyor. Anyone who flames another party for not seeing the correct answer is really just ignorant themselves of what rules the other person is assuming. Although if I had to answer the OP, it states nothing about engines on the airplane, or anything else that would produce thrust, however it does state a relationship exists which forces the aircraft to maintain an airspeed of 0 KIAS. Therefore I would say lift is not possible, and before I get flamed, I fully understand what would happen if you added a thrust component to the aircraft. I'm assuming there is none because there was none stated, and if there was, the relationship between the wheels and the conveyor would not be possible.

Also, the Herrier picture is way off.
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