RE: Can It Take Off??

RE: Can It Take Off??
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RE: Can It Take Off?? - 2/8/2007 1:25:42 AM

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This proves one thing... For any Action there is an EQUAL and Opposite reaction.

Mutually exclusive question = Ridiculously Exclusive answers.

The real question is CAN IT BLEND??

< Message edited by RealPilotAce -- 2/8/2007 1:29:50 AM >

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RE: Can It Take Off?? - 4/18/2008 6:23:46 PM

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in short, no. there must be sufficent air mass and velosity moving across the wing.

Jets, no- thrust is at the back so if the forward air speed is 0 then no air mass is moving across the wing therefor no lift.

high wing trainer- probably not- insufficent velosity and air mass across the wing.

3d- maybe. (depends on wing placement and airfoil)

You don't need a conveyer belt. just block the wheels with something like a 2x4. set the blocks up on edge> run up the throttle> according to some of the people in the thread the plane will achieve vertical take off...simply not true in most cases.

I want to see video of the VTO (vertical take off)

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RE: Can It Take Off?? - 4/18/2008 6:44:41 PM

aflipz

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HA!

Ooooolllld thread.

you are dead wrong smh20502 wheels don't drive the planes, turbines and props do. The only difference with the treadmill is that the wheels will encounter slightly higher rolling resistance, but the plane will still accelerate, gain airspeed and lift.

to put this excercise in stupidity to rest once and for all "Myth Busters" did a special on this myth and not only took off from treadmills with rc planes but also got a full scale ultralight to take off from a makeshift treadmill reproducing the exact conditions described.

Don't beat yourself up too much though even the ultralight pilot though it would not take off!

How people can still not grasp this concept is beyond me... seems so simple!

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RE: Can It Take Off?? - 4/18/2008 6:54:46 PM

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The treadmill is a red herring. The only difference is that the wheels will be spinning faster on the treadmill (airplane groundspeed + treadmill speed). So, yes the airplane will take off like normal. The airplane is driven forward by air, not the ground. People need to understand that the airplane in relation to ground has nothing to do with anything besides calculating trip time (using groundspeed) and runway length needed.

< Message edited by Nathan King -- 4/18/2008 6:58:37 PM >

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RE: Can It Take Off?? - 4/18/2008 11:16:14 PM

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Looks like I misunderstood the intent of the thought experiment. Yes, if your intent is to just use a "Treadmill" then of course the plane will take off because of the separation of air and ground. I was under the impression that we wanted to know if the plane can stay in one place and take off.

So, looks like I needed to read a little more carefully. (no more reading the forum quickly before a meeting)
Thanks for pulling on my shoulders...I CAN SEE!!

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RE: Can It Take Off?? - 4/20/2008 9:49:41 AM

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Ity is too bad I caught up on this thread just now, when the action ceased

. The airplane willl NOT take off, as many of our geniuses said. And airplane relies on thrust and lift in order to lift itself off the ground, and with the conveyor belt, matching the speed of the wheels, will create a O thrust propulsion for the airplane. Therefore, with the airplane remaining stationary, the airplane will not take off as no lift is created at 0 speed.

Yishht.

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RE: Can It Take Off?? - 4/20/2008 10:40:13 AM

F2G-1

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quote:

ORIGINAL: Yishht87

Ity is too bad I caught up on this thread just now, when the action ceased . The airplane willl NOT take off, as many of our geniuses said. And airplane relies on thrust and lift in order to lift itself off the ground, and with the conveyor belt, matching the speed of the wheels, will create a O thrust propulsion for the airplane. Therefore, with the airplane remaining stationary, the airplane will not take off as no lift is created at 0 speed.

Yishht.

So then, if i spin my wheels backwards while in flight, the plane should slow down, and maybe even fly backwards, all because of the wheels? right?

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RE: Can It Take Off?? - 4/20/2008 12:07:32 PM

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quote:

ORIGINAL: Yishht87

Ity is too bad I caught up on this thread just now, when the action ceased . The airplane willl NOT take off, as many of our geniuses said. And airplane relies on thrust and lift in order to lift itself off the ground, and with the conveyor belt, matching the speed of the wheels, will create a O thrust propulsion for the airplane. Therefore, with the airplane remaining stationary, the airplane will not take off as no lift is created at 0 speed.

Yishht.

A lot of the action ceased when a U.S. TV show video taped a model airplane take off from a treadmill in the first half hour, and taped a full scale airplane complete with human pilot take off for the grand finale.

Both airplanes had no problem taking off.

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RE: Can It Take Off?? - 4/20/2008 7:03:42 PM

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I've just deleted a number of recent posts that were highly confrontational and outright flaming. If you cannot discuss the topic in a polite and respectful manner please do not post anything. This goes for both of the "combatants".

If you wish to try again then do so but repeats of the comments and attitude used in the last set of posts will not be tolerated.

< Message edited by BMatthews -- 4/20/2008 7:05:38 PM >

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RE: Can It Take Off?? - 4/20/2008 8:44:24 PM

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quote:

ORIGINAL: BMatthews

I've just deleted a number of recent posts that were highly confrontational and outright flaming. If you cannot discuss the topic in a polite and respectful manner please do not post anything. This goes for both of the "combatants".

If you wish to try again then do so but repeats of the comments and attitude used in the last set of posts will not be tolerated.

Discussing this any further is pointless anyway since it has actually been tested under real conditions.

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RE: Can It Take Off?? - 4/20/2008 9:15:13 PM

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The real conditions it was tested on werent right because the plane accelerated rather than staying in the same position relative to another object. the plane can only take off if there is life on the wing and there isnt if the plane isn't moving forward.

Farr01

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RE: Can It Take Off?? - 4/20/2008 9:41:55 PM

aflipz

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quote:

ORIGINAL: farr301

The real conditions it was tested on werent right because the plane accelerated rather than staying in the same position relative to another object. the plane can only take off if there is life on the wing and there isnt if the plane isn't moving forward.

Farr01

Yes they were, and yes it will take off, because it will accelerate.

read the initial question: "Imagine an airplane is on the beginning of a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.
There is no wind.

Can the plane take off? "

So, in the scenario the plane is sitting still on a stopped conveyor belt as the plane accelerates, the belt accelerates at the same speed as the plane but in the opposite direction. In the "myth busters" televised test with the truck pulling a long tarp with the ultralight taking off from it in the other direction this is exactly what happened the plane takes off as easily as if there was no conveyor belt.

the direction of said conveyor belt would make practically no difference in one the wheels remain perfectly still while the plane accelerates and takes off while in the other they are turning at twice the speed of the plane in relation to the actual ground (not to be confused with the belt)

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RE: Can It Take Off?? - 4/20/2008 10:57:06 PM

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I can't believe this is still going on!

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RE: Can It Take Off?? - 4/21/2008 12:18:07 AM

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I think it was a unfair setup on Myth Busters !!!!!!!!!!!

I have had electrics go backwards. On the ground. Great ground crew of me.

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RE: Can It Take Off?? - 4/21/2008 7:01:08 AM

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quote:

ORIGINAL: cyclops2
....I have had electrics go backwards. On the ground. Great ground crew of me.

Hooked the motor up backwards did you?

Yes the plane will take off. Ask yourselves why having the wheels turn twice as fast would prevent that? As mentioned before, unlike a car the wheels of an airplane are just a low friction method of holding up the airplane and allowing it to move forward UNDER THE EFFECT OF THE PROP OR JET ENGINE. It is like saying that a seaplane on a river will not be able to take off if it is trying to go upstream.

Yes the wheels will be turning faster thanks to the belt but so what. Outside of a little extra drag in the wheel bearings there is nothing there to prevent the aircraft from accelerating normally.

< Message edited by BMatthews -- 4/21/2008 7:02:38 AM >

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RE: Can It Take Off?? - 4/21/2008 1:54:26 PM

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quote:

It is like saying that a seaplane on a river will not be able to take off if it is trying to go upstream.

The friction of wheels is quite different than the hydrodynamic drag of a hull in water. While there is no doubt that the treadmill would only slightly delay takeoff (due to the extra rotational energy stored in the wheels), the water takeoff is a different can of worms.

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RE: Can It Take Off?? - 4/21/2008 6:58:32 PM

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Perhaps so. But it'll still take off and that's the point.

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RE: Can It Take Off?? - 4/24/2008 2:07:25 PM

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lets look at this accurately

*** Brain Teaser ***

Imagine an airplane is on the beginning of a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.
There is no wind.

Can the plane take off?

"...Exactly match the speed of the wheels at any given time..."

NO. If at any time there is forward movement of the plane we expect the wheels to turn at a proportional rate, right? IF, that is the case then ANY time there is acceleration (forward movement of the plane) then the conveyer belt speed must match the forward speed in the opposite direction to get the wheel speed to zero out. No forward movement, no air mass over the wings (other than prop wash), no or very little lift.

The arguement of ground speed and air speed has no bearing here because of the "Conditions" placed on the test. None of the real world tests account for acceleration.

You can try to contest the above statement but you would be waisting your time....if there is ANY forward movement of the plane then the speed of the belt IS REQUIRED TO BE MATCHED IN THE OPPOSITE DIRECTION. WHy? Because the wheels are attached to the air craft. So now we can see that the plane is always stationary.

SO the correct question to ask is...

If a plane is sitting in one place and the throttle is opened to provide under "NORMAL" take off conditions, adequate thrust for lift off... can it take off?

(in reply to BMatthews)