Aerodynamics Discuss the physics of flight revolving around the aerodynamics and design of aircraft.

Can It Take Off??

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Old 04-20-2008, 03:15 PM
  #576  
farr301
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Default RE: Can It Take Off??

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.

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Old 04-20-2008, 03:41 PM
  #577  
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Default RE: Can It Take Off??


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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Old 04-20-2008, 04:57 PM
  #578  
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Default RE: Can It Take Off??

I can't believe this is still going on!
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Old 04-20-2008, 06:18 PM
  #579  
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Default RE: Can It Take Off??



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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Old 04-21-2008, 01:01 AM
  #580  
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Default RE: Can It Take Off??

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.


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Old 04-21-2008, 07:54 AM
  #581  
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Default RE: Can It Take Off??

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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Old 04-21-2008, 12:58 PM
  #582  
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Default RE: Can It Take Off??

Perhaps so. But it'll still take off and that's the point.
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Old 04-24-2008, 08:07 AM
  #583  
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Default RE: Can It Take Off??

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?

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Old 04-24-2008, 08:20 AM
  #584  
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Default RE: Can It Take Off??

Ahahaha

I love this thread, it's like a venus fly trap catching prey for all to point and laugh at.


The answer is always in the question.
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Old 04-24-2008, 08:40 AM
  #585  
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Default RE: Can It Take Off??

And because there are bearings in the wheels, until they burn up and lock up, they can't retard the forward movement of the airplane enough to do anything at all to it's ability to take off. And you saw exactly that happen on TV. Twice. Once with the model and once with the fullscale with it'd disbelieving pilot.

Everyone watching the show saw the airplanes take off. What about what everyone saw actually didn't happen?
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Old 04-24-2008, 09:28 AM
  #586  
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Default RE: Can It Take Off??

O.K. I might as well add to the waterfall of posts.
The short answer is YES, the aircraft will takeoff. As it is not deriving its forward
motion from its wheels, it will move forward from the thrust created from its propeller or jet.
Its wheels will be turning at a higher rate of RPM due to the treadmill speed.
If you could hold the aircraft stationary (eg hold the wings) and the tread mill could be
at 1000 mph then when the aircraft throttle was opened it would move forward as normal
except any wheel bearing friction would slow its forward acceleration by a small amount.
The ONLY way to have the aircraft take off with no forward movement is to have a
WIND SPEED that matches the aircrafts takeoff speed. Then in the plane, the pilot would
see an airspeed of take off value and could begin to fly. The only thing is here that you would need
takeoff power, not to takeoff, but to maintain flying speed once you left the ground.
Dan
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Old 04-24-2008, 09:46 AM
  #587  
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Default RE: Can It Take Off??

Oh boy, here we go again.
all the " but it exactly matches the speed of the wheels ", blah blah is the actual phrase of the question that seems to trip up the no-fly crowd.

The belt speed matching the wheel speed is imposible senario, because the wheelspeed it calculated by the forward motion of the aircraft PLUS the rearward motion of the belt.
WS =BS + FM ie: belt goes 10 mph backwards, plane goes 5 mph forward, wheels spin 15 mph. Mo matter what the belt puts out, you have to add the forward motion component to it to get the wheel speed.

Fly, Fly, Fly away, little airplane, away from the stupid, forged in hell by satan himself, treadbelt.
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Old 04-24-2008, 11:36 AM
  #588  
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Default RE: Can It Take Off??

Artificial intelligence is no match for human stupidity.


Keep the "no, it won't take off because of my super science.." answers coming guys, i need another good laugh...
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Old 04-24-2008, 04:44 PM
  #589  
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Default RE: Can It Take Off??

ORIGINAL: aflipz
QUOTE AND POST REMOVED AS IT VIOLATES THE POSTING RULES...
huh? you talkin to me?
you do realize i'm saying it flys, right?
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Old 04-24-2008, 05:15 PM
  #590  
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Default RE: Can It Take Off??

ORIGINAL: F2G-1


ORIGINAL: aflipz



QUOTE AND POST REMOVED AS IT VIOLATES THE POSTING RULES... ...
huh? you talkin to me?
you do realize i'm saying it flys, right?

No, I know you get that the plane will take off... I hope others will come and say it won't with even more whacky and imaginative pseudo-science so we can all point and laugh!

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Old 04-24-2008, 05:21 PM
  #591  
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Default RE: Can It Take Off??

OK, it's back to calling each other stupid etc


The question was answered on TV.
Since the majority of posters can't seem to understand Please resist the urge to curse, flame, degrade, insult or embarrass someone in your post. and it's simply a constant edit or cut thread,

this thread is going to get a rest for awhile.

Locked until further notice.
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