A question...

[98Camaro3.8]

Originally posted by 3.4 slow to go:
put that same plane on teh ground w/o landing gear & kick the engiens, what happens?

You get asked by the local FSDO to appear for a 709 ride. [img]tongue.gif[/img]

[3.4 slow to go]

Originally posted by MTMike:
A plane is standing on a movable runway (something like a giant treadmill). As the plane moves the treadmill moves but in the opposite direction. The treadmill has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

The question is: will the plane take off or not?

Discuss....

W=FxD

there is no distance in the question

[JusFlyinBy]

Originally posted by 3.4 slow to go:
the jet/prop wash will only hit certain parts of the wing, but not enough to create the lift required.the engines create enough force to overcome the friction between the wheels and the surface. Once the let/plane gets going, it's the full effect of the air moving over/under the surface area to generate lift. Once the plane gets going fast enough, then there will be lift to fly.


</font><blockquote>quote:</font><hr />Originally posted by MTMike:
And the jet engines or prop create this "air rushing" effect under it's wings by creating thrust and PUSHING the plane forward through the air regardless of what the landing gear is doing Whether that landing gear is on asphalt, on a treadmill or tucked up inside of the plane.

so if the landing gear is up, and teh plane is sitting on the tarmac, it will still move even if th eengines are running? </font>[/QUOTE]Thats a ton of friction. If the engines can overcome the friction, then absolutley it will move forward. Im guessing 30,000 lbs of force will over come the friction of metal on asphalt too.

Now the wheels, the only friction they apply is ball bearing friction in the wheels. Pretty much nothing.

[3.4 slow to go]

you're forgetting friction of the the rubber to the pavement (aka traction, or lack of ;) ) and the weight being imposed on the rubber as part of the friction.

[fbird01]

[img]graemlins/slap.gif[/img] to anyone who thinks the plane will take off and fly

[mwh27]

Ok people. I only wanna post ONE example to end this madness. So please read.

Say your in a wheelchair, with a big *** fan attachted to the rear, and your on an infintly long treadmill.

You turn the fan on you roll forward, the treadmill turns on, it takes you back to your orignal starting point.

Got that? That can happen till your going very fast and the treadmill will be going equally in the oppsite direction.

Now do you agree that the wind directly in front of me and directly behind me is going X mph because my fan is rotating very fast?

Well, it is, or I would be in a huge vaccum.

Now all of a sudden attach a wing behind the fan, the air will go over the wing and produce lift, if that lift is greater than the weight of me in the wheelchair, I will rise.

There is no possible way for the treadmill to couteract force in the Y axis, on the X it can.

But lift isnt on the X axis.....

PS: and to anyone who thinks it wont get off the ground or fly. Please explain on the ground can counteract the force of lift on the wing.
--------------------------------------------------------------------------

Another situation to think about.

In a common situation is the differential relationship between air-speed and ground speed. If an aircraft has a set speed of let's say 75knts and it hits a head wind of 75knts, it's ground-speed would be 0. Even though the lift + trust is present, the plane isn't moving forward.

The plane isn't moving forward... BUT IT IS FLYING!!

----------------------------------------------------

Damn, I'm on a roll. Last one.

Lets say this "plane" is a harrier jet(look up V-STOL harrier jets)

Now, some people would say that you cant use this jet in this sitation cause of the air tubes that would point down.

But I ask, what are the wings doing? pointing the air down and creating a high pressure system, just like the air tubes of the harrier?

[ November 30, 2005, 10:47 PM: Message edited by: mwh27 ]

[98Camaro3.8]

Originally posted by mwh27:
Ok people. I only wanna post ONE example to end this madness. So please read.

Say your in a wheelchair, with a big *** fan attachted to the rear, and your on an infintly long treadmill.

You turn the fan on you roll forward, the treadmill turns on, it takes you back to your orignal starting point.

Got that? That can happen till your going very fast and the treadmill will be going equally in the oppsite direction.

Now do you agree that the wind directly in front of me and directly behind me is going X mph because my fan is rotating very fast?

Well, it is, or I would be in a huge vaccum.

Now all of a sudden attach a wing behind the fan, the air will go over the wing and produce lift, if that lift is greater than the weight of me in the wheelchair, I will rise.

There is no possible way for the treadmill to couteract force in the Y axis, on the X it can.

But lift isnt on the X axis.....

PS: and to anyone who thinks it wont get off the ground or fly. Please explain on the ground can counteract the force of lift on the wing.

The plane isn't moving forward... BUT IT IS FLYING!!

A) The airplane/wheelchair will not stay in the same location. The treadmill will not move it back to its starting point.

B) IF (big IF here)....IF the airplane didn't move, the fan/propeller would not induce enough airflow to create lift. I can sit at the end of the runway with my brakes on and apply full power without taking off. That's how we do a short field takeoff.

If the airplane isn't moving, it won't fly. But in this case, it is moving so it does.


Edit: Now let's say the conveyor is moving, but you're stradling the treadmill with a rope tied to the airplane (brakes off). The airplane does not pull you backwards at X mph. You are able to hold the plane in its position even though the treadmill is moving the other way. Now replace your weak body with an extremely strong propeller/jet. It will accelerate, then it will reach the proper speed and takeoff as it would any other time.

[ November 30, 2005, 11:00 PM: Message edited by: 98Camaro3.8 ]

[AZ3.8Camaro]

I thought about this at work today.

I originally said no, because I a used to thinking about car, where power is transmitted to the wheels.

On a jet, the power is transmitted to the air.
The plane moves, and most likely flies.

[SpeedingFirebird]

Originally posted by 98Camaro3.8:


25 pages of arguing among pilots: http://forums.flightinfo.com/showthread.php?t=66860

I find that quite scary.

Oh, and to answer the question. Planes great lift via aerofoil (sp?). The wind going over the wing does not match that of the wind going under the wing, thus creating lift (I forgot which moves faster).

The treadmill part is not relevant. The air going over the wing is stagnat; therefore, she won't fly cap'n.

[C.O.Jones]

Why is it that no one thinks outside the box on this one and asks

"What kind of plane is it?"

A Harrier would most certainly take off......

[98Camaro3.8]

Originally posted by SpeedingFirebird:

Oh, and to answer the question. Planes great lift via aerofoil (sp?). The wind going over the wing does not match that of the wind going under the wing, thus creating lift (I forgot which moves faster).

The treadmill part is not relevant. The air going over the wing is stagnat; therefore, she won't fly cap'n.

wtf are you talking about? How could the treadmill not be relevant?

And the air over the wing is not stagnant, because there's plenty of airflow caused by the plane moving through the air.

FWIW, Bernoulli's principle isn't the only reason an airplane flies. Newton has a little something to do with it as well. ;)

[camaro_speedemon]

I can't believe no one has said it, we all need to email Mythbusters [img]graemlins/rofl.gif[/img]

[vroom-chirp]

look at it like this....
a plane is made to fly like this way ------&gt;
the tread mill is rolling this way &lt;------
so this means the plane wont move right?..wrong

top of the runway is going this way ------&gt;
so that means the bottom is moveing &lt;------
causing the runway to roll like a wheel.
so if the plane is on top it is actually rolling the wrong way to take off!!
plane
------&gt;
top
&lt;------
bottom
------&gt;
direction of travle
&lt;---------
so you see, the plane cannot take off because it wasnt made to fly backward!!, but as posted a harier would have no problem...
im an aircraft refueler

[ December 01, 2005, 12:07 AM: Message edited by: vroom-chirp ]

[3.4 slow to go]

I still fail to see how there is any air moving over the wings, since the wheels treadmill is going the exact speed opposite that the plane is going. Talking commercial jets, the engines are under the wings, thus no air speed over the wings. And for those saying the thrust under the wings will provide the lift, well that thrust isn't under all the wings underside surface area.

obtw, it's the pressure difference between the slower upper side & faster underside of air that creates lift.

[98Camaro3.8]

Originally posted by camaro_speedemon:
I can't believe no one has said it, we all need to email Mythbusters [img]graemlins/rofl.gif[/img]

Actually, this was suggested on the Mythbuster's forum on the Discovery Channel website. There's 47 pages of arguing there. At the end, most of the people understood the airplane would fly. They also agreed the Mythbusters would not do it for a show because it's just simple physics. That's not just my opinion, that's what on their site.

Originally posted by vroom-chirp:
this is the end and answer, (im an aircraft refueler)

I'm a commercial pilot and am 1 flight away from being a certificated flight instructor....didn't seem to make much of a difference to them. [img]tongue.gif[/img]