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tunnelcat

Conveyer Belt Takeoff- Mythbusters jumps in!!!

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>This December; Mythbusters will settle once and for all>whether an aircraft can take off from a conveyer belt matching>its forward speed. They utilised a quarter mile belt and an>ultralight.>>Savage was quoted- "I won't say the outcome, but the pilot and>the entire flying club got it wrong.">>Last chance to put your money where your mouth is... did>L'adamsonget it right??? :-)>It takes off,,,,,Right???? :-hah L.Adamson

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We shall finally see... Just to be fair; I think it takes off too!!!:-)FLYing? It's cool. Trillions of birds and insects can't be wrong.

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Does the wing have air going around it?Yes, then it creates liftNo, then it stays on the ground.I don't know what the treadmill has to do with the aerodynamics of the wings.

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I don't think so. Conveyor belts do not have enough aerodynamic lift to take off. I suppose you could shoot one out of a magnetic rail gun and it would "fly" for a while, but a conveyor belt on its own? I don't think so. :)

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>Does the wing have air going around it?>>Yes, then it creates lift>>No, then it stays on the ground.>>I don't know what the treadmill has to do with the>aerodynamics of the wings.The idea of the treadmill, is to technically pull the aircraft back as the prop tries to pull it forward. No forward velocity, & no lift.Supposably..

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The problem is that it is just a horribly written question that can be interpreted many ways.

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There were two very long threads "Something to think about" in which the question was expressed much clearer; if I can find one I will bump it. I merely wanted to report that Mythbusters has graciously settled the question, and we will see the fruits of their labor come December.Best Regards, Donny :-waveFLYing? It's cool. Trillions of birds and insects can't be wrong.

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I'm no expert, but here's the way I see it....Put a car on the conveyor belt, and it will stay absolutely still (or only move a tiny amount, depending on how quickly the belt will adjust to speed changes) in relation to the rest of the world. Because the force of acceleration is being applied to the conveyor belt itself. The car will not be able to overcome the conveyor belt..However, an aircraft, I believe, will. An aircraft, any aircraft, applies its force of acceleration to the air, not to the ground. Applying the thrust against the air will still cause the aircraft to move in relation to the rest of the world, and take off once the correct airspeed is reached. The conveyor belt will likely apply a certain degree of drag to the aircraft, as it attempts to pull the aircraft backwards via the small amount of friction in the landing gear, but that would not be enough to prevent forward motion or takeoff..You could get an aircraft to stay still in relation to the rest of the world by replacing the conveyor belt with a wind tunnel, but even that won't prevent the aircraft from taking off because there'd still be airflow over the wings generating lift..So, my bet is that their tests prove you can take off...

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The only way to make this theory plausible is to have the aircraft takeoff using only the power of the conveyer belt. The aircraft's engine(s) would have to be turned off with zero wind conditions at the test site.The Mythbusters' experiments have been busted in the past by slightly more scientific minds......they do make for good entertainment though.John

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I'm confused as to how it's going to be set up. If the brakes of the aircraft are set, then yes it's going to fly a short distance. What you would have is the equivalent of a catapult launch. If the wheels are allowed to turn freely, then no way it's going to obtain flight. You would have no movement of air over the wings. Fitz

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>The problem is that it is just a horribly written question>that can be interpreted many ways.That's not the problem, that's the point. ;)

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>>The problem is that it is just a horribly written question>>that can be interpreted many ways.>>That's not the problem, that's the point. ;)This is the point exactly. The whole question as laid out is a paradox and thats what makes it fun. There are many finer technical points that could make it an interesting physics problem but with out those points as stated, there is no answer.

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>> No - PLEASE... Let's not start this all over again! Way too much bandwidth being consumed. Let's just wait until we can watch the Mythbusters and then we can start all over again... :)

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This December; Mythbusters will settle once and for all whether an aircraft can take off from a conveyer belt matching its forward speed. They utilised a quarter mile belt and an ultralight.Savage was quoted- "I won't say the outcome, but the pilot and the entire flying club got it wrong."Last chance to put your money where your mouth is... did L'adamson get it right??? :-)Best Regards, Donny :-waveFLYing? It's cool. Trillions of birds and insects can't be wrong.

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> I'm confused as to how it's going to be set up. If the>brakes of the aircraft are set, then yes it's going to fly a>short distance. What you would have is the equivalent of a>catapult launch. If the wheels are allowed to turn freely,>then no way it's going to obtain flight. You would have no>movement of air over the wings.>If this is done, as in the original question, it's not a case of the conveyor belt providing the forward speed. Just the opposite. The belt is suppose to move backwards, at the same speed the aircrafts wheels rotate in a forward direction with the prop turning at takeoff speed. This is supposeably to stop all forward motion, which would in turn stop the creation of lift.However, using my treadmill as a sample belt, I discovered that my toy airplane tied to a string, had virtually no rolling resistance from the belt going in the opposite direction. The plane will almost act as though it's skimming ice...........and takeoff.L.Adamson

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Larry;Retry your experiment with a piece of plastic or similar mounted justabove the belt to block the "Wind" that might be generated by the movement of the belt.Also I've seen recent Utube vids of guys launching and recovering MODELaircraft from vertical status.....something that to my knowledge hasnot been done with real aircraft.Probably something to do with not being able to duplicate the horsepowerto weight ratio. Also prop size would figure in.In other words if everything is to SCALE....IT WON'T FLY..

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What happens after your airplane "takes off" and you move it left or right from your treadmill and the airplane is now over stationary ground. A "successfull" flight is one where you can takeoff and sustain an altitude for some kind of distance.I can make any reasonably sized object "fly" by simply throwing it in the air, yet I can't say it's sustained flight.

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The converyor belt pulls back on the wheels only, which spin freely.Plane takes off.Does anyone know when the episode of Mythbusters will be aired in the UK, or will it be the same as in the US?Dave

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>The whole question as laid out is>a paradox and thats what makes it fun. It is a paradox or it is not - depending on interpretation. If you think it is 'fun' to debate ambiguous statements it is your choice but I think the problem is actually far more interesting when it is stated clearly in which case it becomes a real physics problem.How it can be stated unambiguously? For example: the belt moves in the opposite direction to the airplane with a speed (in relation to the fixed ground) equal to the takeoff speed of the airplane.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

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It wont take off. It will only spin the wheels.

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It won't,here's why I think not:The forward speed of the aircraft is equal to the opposite speed of the belt, therefore the aircraft is not carrying any actual forward speed. No forward speed in real terms means no airflow around the wings, erego no lift, so no take off.I assume we are talking about the belt running against the aircraft anyway?I tried a small experiment in FS, whereby I set the wind speed equal to the takeoff speed of a light aircraft, the result was that with no ground speed, the plane still got lift, so take off was achieved. You don't need ground speed and I think this is the common misconception with flight, you need airspeed alone to lift, so it doesn't matter what ground speed you show, if you have zero airspeed you won't lift. simple as that.

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:-rollThe thing people keep forgetting concerning this issue is that aircraft don't in ANY fashion propel themselves by pushing backwards against the ground, runway or giant treadmill they are supported on prior to takeoff. Note that they don't immediately lose speed, and thus lift, immediately after takeoff. This is because the forward propulsion is produced by exerting force rearward on some combination of air (propeller driven aircraft), engine exhaust (turbojet and the occasional rocket propelled aircraft) or a combination of air and exhaust (the fan jets used by many modern "jet" airliners). Every action (forcing air and/or exhaust rearward) absolutely MUST result in an equal and opposite reaction (forward force against engine and the attached aircraft). The modest amount of bearing friction in the wheel hubs would accomplish little to counter the forces generated by the engine(s).:-jumpyAs long as the wheel brakes are released the treadmill would have negligible effect on the ability of the aircraft to move forward compared to the air and the rest of the world. The ONLY thing the treadmill could accomplish would be making the wheels spin at double the usual RPM.

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lol...if the engine is at takeoff setting, and the wheels spin as you say....what stops the forward velocity (and therefore takeoff lift)? Certainly not an interface between the conveyor and the wheels...you've already agreed they spin.So if not that, then what pray tell degrades this planes motion? The answer, of course, is nothing...there is nothing that changes the planes forward motion.Therefore, it takes off.And since its engine is on, the takeoff is no different from a normal takeoff. The only impact from the conveyor would be felt if the conveyor speed was so fast that the wheel bearings failed and the wheel was no longer able to spin freely.Bob

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