Plane on a conveyor belt
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No. A plane takes off due to lift. Lift is caused by air moving under the wings. If the plane is physically sitting in the same spot, wheelspeed does not matter.
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Yes, Planes are propeled by air, the wheels are free to roll as they will so they will just be rolling twice as fast as the plane is actually traveling. So the plane would still be pushing forward by pushing the air.
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Why do planes need X amount of runway space to safely take off then? They have to come up to speed before they can generate enough air movement under the wings in order to take off.
However this is not wheelspeed, it is the physical speed of the chassis. This happens from the wheels moving along the ground. If the wheels are moving 300 mph but the plane has not moved more than 2" it is not going to take off, as the airflow under the wing is nonexistent.
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Correct. The only thing this would be negated by is a harrier. It'd just go straight up.
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integra_gsr98 wrote:
Why do planes need X amount of runway space to safely take off then? They have to come up to speed before they can generate enough air movement under the wings in order to take off.However this is not wheelspeed, it is the physical speed of the chassis. This happens from the wheels moving along the ground. If the wheels are moving 300 mph but the plane has not moved more than 2" it is not going to take off, as the airflow under the wing is nonexistent.
If i understand it correctly, it would be moving, the wheels don't propel the plane. They are powered by jet engines. which would push the plane forward no matter how the ground is moving backwards.
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And this topic has been argued to death on every board online and never can anybody actually prove it. I leave it to the Mythbusters and vote it will not fly.
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here is 13 pages on this if your bored......
http://www.mnsportcompacts.net/forum/showthread.php?t=23115&highlight=plane
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inspector01 wrote:
If i understand it correctly, it would be moving, the wheels don't propel the plane. They are powered by jet engines. which would push the plane forward no matter how the ground is moving backwards.and if the plane is moving forward at 50mph (speed of the plane calculated by air speed, not wheel speed), the conveyor would be moving backwards at 50mph. In turn, the wheels of the plane would be turning at 100mph.
the plane would require a bit more thrust on the conveyor than on a traditional stationary runway to acieve the same speeds because it must overcome a small bit of friction in the wheel (bearings) that try to pull it in in the direction of the conveyor.
but no matter what the plane will move forward.
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harwood39 wrote:
Yep, it will take off, it will still be moving just the wheels will be moving at twice the speed they normally would.Planes dont take off based on how fast the wheels are spinning...how is it going to move at all with a conveyor matching its speed? It will just sit in one spot with the wheels spinning out of control....
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TsiTom wrote:
Planes dont take off based on how fast the wheels are spinning...how is it going to move at all with a conveyor matching its speed? It will just sit in one spot with the wheels spinning out of control....The conveyor is matching its speed, but the plane can still go forward because it isn't propeled by its wheels, it is pushing air which is still sitting still.
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NO, the plane will not take off. Like Nick said, in order for an airplane to lift off, air is required under the wings. The wheels are spinning, but the plane isn't moving=no air under the wings.
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TsiTom wrote:
Planes dont take off based on how fast the wheels are spinning...how is it going to move at all with a conveyor matching its speed? It will just sit in one spot with the wheels spinning out of control....psst...
if the plane is sitting in one spot, the conveyor wont' be moving either..
this is something you need to think about.
Car speed is refering to wheel speed. If a car was on the same conveyor then yes, it would sit in the same place as the car's wheels would be moving 50mph in one direction and the conveyor 50mph in the other.however plane speed is measured as airspeed - speed relative to the air (or static spot on the ground). So for a plane to be moving 50mph it HAS TO BE MOVING in relative space. The plane's wheels could be moving 100mph, but if the plane has no air speed, the plane's speed is flat out ZERO (and it's sitting in one spot).
However, like people have said.. thrust acts on the air around the plane which is not moving...therefore the thrust will act just as it would if the plane was not on a conveyor...
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T ! N wrote:
NO, the plane will not take off. Like Nick said, in order for an airplane to lift off, air is required under the wings. The wheels are spinning, but the plane isn't moving=no air under the wings.but it will move! hands down, no doubt about it, it will move..
now yes there may be a very small range at low speed where the thrust of the engines is not enough to overcome the friction in the wheels.. HOWEVER, even so the airspeed of the plane would be zero, therefore the conveyor would not be moving either...
Essentially you're throwing out an impossible situation here... (short of holding the brakes).
People are say that even though there is thrust, the plane sits in the same spot because the conveyor is moving in the opposite direction. WRONG. if the plane is sitting in the same spot it's speed is ZERO. therefore the conveyor speed would be zero..
well if the conveyor speed is zero the plane is going to move.... -
The plane will take off. The conveyor will keep matching the wheels speed but the plane itself will continue to move forward in space due to it's propulsion being independent of the restrictions imposed by the conveyor.
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Dubbsy, you weren't supposed to post in this thread! Since people have begun linking to other threads already, I'll throw in my link (scotwithonet actually described the situation a lot better than people on other boards):
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