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Old 22 November 2007, 07:33   #11
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The conveyor belt is designed to match the speed of the plane exactly but moves in the opposite direction. The engines are running at take-off thrust, the brakes are off, etc. Everything is normal save for the fact the plane is on a treadmill.
If the conveyor matchs the speed of the aircraft, then for all intents and purposes the aircraft is stationary.

If the aircraft moves faster than the conveyor then that becomes another story!

jon
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Old 22 November 2007, 07:40   #12
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if you take the scenario of someone running on a treadmill.

To stay on the thing you have to match the speed of the treadmill. You are using energy running (ie thrust) but you are stationary

Jon
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Old 22 November 2007, 07:53   #13
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I have come across a very similar real situation when flying my model planes. The model trainer cessna i have takes off and lands at about 20mph. I have been in situations where there has been a 20mph headwind so i land stationary. So the airspeed is 20mph but Sog is 0. So i think the plane would take of because it would have the same airspeed as normal.


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Old 22 November 2007, 07:54   #14
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But the wheels do not propel the plain it is the thrust from the engines, so it will take of as normal moving forward through the air creating lift under the wing!
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Old 22 November 2007, 08:19   #15
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Quote:
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if you take the scenario of someone running on a treadmill.

To stay on the thing you have to match the speed of the treadmill. You are using energy running (ie thrust) but you are stationary

Jon

Jon

In this case you are matching Ground speed not air speed.
Thats the big differance, as the plane travels through air, and is not driven along the ground by motion of its wheels.

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Old 22 November 2007, 08:25   #16
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Jon

In this case you are matching Ground speed not air speed.
Thats the big differance, as the plane travels through air, and is not driven along the ground by motion of its wheels.

Nasher.
exactly my point........where is the air speed???
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Old 22 November 2007, 08:30   #17
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The air speed comes from the thrust of the engines which are running at take off speed.

The engines are pushing against the air not the conveyer.

I'm not explaining myself very well I know.

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Old 22 November 2007, 08:37   #18
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The air speed comes from the thrust of the engines which are running at take off speed.

The engines are pushing against the air not the conveyer.

I'm not explaining myself very well I know.

Nasher.
The engines are producing thrust to keep the aircraft at the same speed as the treadmill speed against it. There is no airflow over the wings as the aircraft is stationary because the thrust producing forward motion is Exactly the same as the reverse motion of the treadmill

I'm starting to get confused now!
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Old 22 November 2007, 08:54   #19
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But the wheels do not propel the plain it is the thrust from the engines, so it will take of as normal moving forward through the air creating lift under the wing!
Only if the speed created by the thrust EXCEEDS the reverse speed of the treadmill. The aircraft will then be moving forward and creating lift under the wings. It would then give a shorter take off run. Conversly, if the thrust is less the aircraft would reverse on the treadmill. Remember in the original question there was no mention of any simulated wind speed.
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Old 22 November 2007, 09:16   #20
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I'm starting to get confused now!
you said it
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