Airplane on a converter belt question.

[sushijerk]

I recently heard this and gave it a lot of thought:

Suppose a normal commercial airplane is ready to begin takeoff. The thrusters are turned on and the wheels of the airplane begin to move forward. However, the plane is on a converter belt which is rigged to move/spin in the opposite direction of the plane at the exact speed of the wheels. Image that there is a electronic device gauging the speed of the wheels and then immediately relays the information to the belt to accelerate/deccelerate accordingly. Will the plane ever be able to achieve takeoff?

[MidGe]

use the search facilty... been discussed to death already

[Lestat]

My answer would be no.

So I see I'm wrong. This was a cool problem! Glad you posted it. Thanks.

[sushijerk]

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use the search facilty... been discussed to death already

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Really? Doh. A mechanical engineering friend of mine said the answer is yes, but I'm still not sure why.

[Bork]

conveyor belt

If the plane moves forward fast relative to the air then it will take off, if not no it won't take off.

Air needs to flow rapidly over the wings to generate lift.

[MidGe]

plane + conveyor belt

BTW, whether an aeroplane takes off or not has nothing to do with runway speed (A/c carrier), aeroplane ground speed, or torque on the wheels. If it's airspeed is greater than take-off speed it will take off. I have seen planes flying backwards relative to the ground and they were not falling. lol.

[madnak]

The plane will take off. The wheels aren't moving the plane forward, they're just spinning idly.

[purnell]

[ QUOTE ]
I recently heard this and gave it a lot of thought:

Suppose a normal commercial airplane is ready to begin takeoff. The thrusters are turned on and the wheels of the airplane begin to move forward. However, the plane is on a converter belt which is rigged to move/spin in the opposite direction of the plane at the exact speed of the wheels. Image that there is a electronic device gauging the speed of the wheels and then immediately relays the information to the belt to accelerate/deccelerate accordingly. Will the plane ever be able to achieve takeoff?

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Clearly the answer is yes. The planes engine(s) are not connected to its wheels. The same low pressure ahead of the intakes would pull the plane forward, and it would move along the runway and take off as usual, regardless of how fast the conveyor belt runs in any direction.

edit: err, "...belt runs in either direction" (parallel to the engines' force). [img]/images/graemlins/crazy.gif[/img]

[purnell]

[ QUOTE ]
plane + conveyor belt

BTW, whether an aeroplane takes off or not has nothing to do with runway speed (A/c carrier), aeroplane ground speed, or torque on the wheels. If it's airspeed is greater than take-off speed it will take off. I have seen planes flying backwards relative to the ground and they were not falling. lol.

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While this is correct, aircraft carriers use a steam-powered catapult to accelerate the aircraft to the required speed in the very short distance available. If the catapult fails, the aircraft nearly always falls into the sea.

[MidGe]

[ QUOTE ]
While this is correct, aircraft carriers use a steam-powered catapult to accelerate the aircraft to the required speed in the very short distance available. If the catapult fails, the aircraft nearly always falls into the sea.

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This true of most high performance aircrafts, it is not so, of some other aircrafts (and I am talking about conventional a/c not STOL or VTOL). The reason is that whatever the plane, if it can reach its minimum take-off speed minus headwind by the end of the deck, there are no issues except the margin of safety. There are many examples of such unassisted take-offs from a/c carriers for demonstration, exhibition or routine actions. I don't even think that all a/c carriers have catapults... (see russia).