Airplane on Conveyor Belt Mythbusters 12/12

[Randy]

On a bunch of internet forums (fortunately, not here :yahoo: ), a ton of bandwidth was wasted on the hypothetical situation of the ability of an airplane to take off if it was on a conveyor belt spinning in the opposite direction of the wheels at the same speed of the wheels. Laypersons, physicists and scientists alike provided point/counterpoint with no clear cut conclusion (but, I think the majority leads to the theory that it could take off). Mythbusters is schedule to tackle the topic tomorrow. Check your local listings.

 

[exskibum]

So the airplane is standing still with no airspeed over and under the wings? And we're not talking about a rotary winged aircraft?

 

[borrec]

They are joking right? On a treadmill there is no forward movement, you are running but not moving forward. The wheels could be going 500 MPH but no airflow over wings equals zero lift. :dribble:

 

[Fencer]

They are joking right? On a treadmill there is no forward movement, you are running but not moving forward. The wheels could be going 500 MPH but no airflow over wings equals zero lift. :dribble:

oster_stupid:

 

[Scythian]

They are joking right? On a treadmill there is no forward movement, you are running but not moving forward. The wheels could be going 500 MPH but no airflow over wings equals zero lift. :dribble:

'Cuz airplanes are driven forward by its wheels.... :blink:

So how does it fly with no wheels?

Unlike motorcycles, airplanes are not dependent on friction for forward motion. The are powered by thrust by prop or jet. Thrust doesn't care about the treadmill--the engines will drive it forward on the treadmill until it reaches slight velocity--or the wheels come off....

 

[v65]

fortunately, not here :yahoo:

Oopsie

 

[Kevin Daly]

So the airplane is standing still with no airspeed over and under the wings? And we're not talking about a rotary winged aircraft?

so the prop provides air movement but the plane does not get the added benifit of moving forward such that wind is moving over the entire wing. In principle if the prop produced enough airflow over the wings to produce enough lift the plain would come off the ground. but in reality the props thrust is mainly on the wing surface near the fuselage hence produces relatively little lift from the wing relative to what the wing can produce as it moves through air. We all know that if a plane is still in still air and you apply full throttle it does not lift off the ground but if it is a windy day a good head wind will lift a plane off the ground

 

[tinpusher]

Hell, maybe these people have solved the problem at our countries major airports of where to put 10000 ft runways. :thumbsdownsmileyanim:

 

[Kevin Daly]

They are joking right? On a treadmill there is no forward movement, you are running but not moving forward. The wheels could be going 500 MPH but no airflow over wings equals zero lift. :dribble:

'Cuz airplanes are driven forward by its wheels.... :blink:

So how does it fly with no wheels?

Unlike motorcycles, airplanes are not dependent on friction for forward motion. The are powered by thrust by prop or jet. Thrust doesn't care about the treadmill--the engines will drive it forward on the treadmill until it reaches slight velocity--or the wheels come off....

yes they are powered by thrust, which makes them move through air and it is the differential velocity of airflow over the top vs. bottom of the wing that causes low pressure above the wing and hence lift :clapping:

 

[madmike2]

'Cuz airplanes are driven forward by its wheels.... :blink:
So how does it fly with no wheels?

Unlike motorcycles, airplanes are not dependent on friction for forward motion. The are powered by thrust by prop or jet. Thrust doesn't care about the treadmill--the engines will drive it forward on the treadmill until it reaches slight velocity--or the wheels come off....

I believe the theory is that if the treadmill is driven so that the wheel speed matches the airspeed at which the thrust would be driving the aircraft, the effective groundspeed would be zero and thus the aircraft would be relying solely on the thrust produced by the engine(s).

There qre some very powerful military aircraft that might be able to fly relying completely on the thrust produced by the engines, but my estimation is that 99.9% of the remaining aircraft require windspeed over the wings that is caused by the thrust actually moving the aircraft forward rather than having the craft in a relative stationary state because the treadmill would be negating that forward movement needed to create the pressure differential on the wings that we call "lift".

Butt whudda eye noe? I hain't noe en-gun-eer. All in all, it should prove to be an interesting experiment.

 

[FatNakedGuy]

I remember my first flight lesson.... taxing to take off and I'm yanking the "steering wheel" all over the place trying to make that plane turn... The instructor must have been laughing his ass off! haha I wonder how many others make that same mistake their first time out... doh!

 

[tinpusher]

They are joking right? On a treadmill there is no forward movement, you are running but not moving forward. The wheels could be going 500 MPH but no airflow over wings equals zero lift. :dribble:

'Cuz airplanes are driven forward by its wheels.... :blink:

So how does it fly with no wheels?

Unlike motorcycles, airplanes are not dependent on friction for forward motion. The are powered by thrust by prop or jet. Thrust doesn't care about the treadmill--the engines will drive it forward on the treadmill until it reaches slight velocity--or the wheels come off....

Actually an aiplane uses thrust to overcome friction (read "drag"), to generate enough speed (read "velocity"), which generates lift. If you have enough thrust (read "NASA"), you dont need velocity to generate lift. However, airplanes use lift to fly, otherwise they wouldnt have 120ft wingspans......and they would be called rockets, not airplanes.

JS

 

[Bearly Flying]

The wheels have NO effect other than freely spinning on the treadmill, the Prop will drive the aircraft forward until sufficient airspeed is achieved for take off.

The wheels may be spinning a lot faster than normal due to the effect of the treadmill, but that is the only difference.

 

[madmike2]

The wheels may be spinning a lot faster than normal due to the effect of the treadmill, but that is the only difference.

I believe the premise of the experiment is to use the treadmill speed to negate any forward movement so the ground is "0" knots, though the wheelspeed would be enough to indicate sufficient speed to "lift off". To me, that means the effective airspeed will also be "0" because the wheel speed will be matching (negating any forward movement) whatever the thrust would be producing. That "should" mean no lift at the wings.

 

[tinpusher]

The wheels have NO effect other than freely spinning on the treadmill, the Prop will drive the aircraft forward until sufficient airspeed is achieved for take off.
The wheels may be spinning a lot faster than normal due to the effect of the treadmill, but that is the only difference.

I've seen an airplane take off in as little as 18ft.



But it does this because of the very low weight of the airplane.

Less weight = Less lift required = Less Velocity = Less Runway to generate that velocity

The Super Cub weighs in at a whopping 983lbs empty.

Piper PA-18

 

[Bearly Flying]

Thats the whole point Mike. The speed of the tread mill does not effect forward motion of the plane, the wheels just spin freely. Airplane wheels are just large castor's they do not drive the aircraft.

 

[wfooshee]

Bearly is correct here. The treadmill has absolutely no effect on the power output by the plane's engine. The treadmill CANNOT reduce the plane's forward motion. It can only make the wheels spin way faster.

The only way the treadmill will affect the takeoff is if the brakes are on, which is always how they take off, right?

Now, if you're launching a glider from a truck, then you're no go. The truck won't move fast enough, because it IS wheel-driven, and the treadmill fights its forward motion.

 

[Silver Penguin]

On a bunch of internet forums (fortunately, not here :yahoo: ), a ton of bandwidth was wasted on the hypothetical situation of the ability of an airplane to take off if it was on a conveyor belt spinning in the opposite direction of the wheels at the same speed of the wheels. Laypersons, physicists and scientists alike provided point/counterpoint with no clear cut conclusion (but, I think the majority leads to the theory that it could take off). Mythbusters is schedule to tackle the topic tomorrow. Check your local listings.

Duh! It's simple. The good people from Mythbusters will blow it up. :lol:

Jill

 

[worldbound4now]

Logic tells me the plane will take off without a problem. The plane pushes itself forward off of the density of the air, not off of it's traction/friction between the wheel and the ground.