Ok smart guys....

[toodles]

Imagine this improbable scenario...

There's a plane (what type of plane is immaterial, as long as it's not VTOL) sitting on a conveyor belt. A huge-arsed conveyor belt the length of the runway. Now this conveyor belt is designed in such a way that it will perfectly match the speed of the plane, but travelling in the opposite direction!

So, for example, if the plane takes off to the west, the conveyor belt travels towards the east. It's a perfectly calm day with absolutely no breeze to speak of.

Will the aircraft be able to take off?



p.s. please try and answer this under your own steam [AKA using your brain not google]. and make the answer Yes or No followed by a brief description if you are that way inclined.

PPS - you're a wanker if you cheat at this.

 

[S.]

Yes. Unless you somehow invented a wheel-drive plane

 

[dilemma]

OK, after looking at that ridiculous treadmill bike, I have a mental picture of a plane on a giant treadmill

I don't have an answer as my brain failed to switch on today

 

[Carlin]

If there is enough airflow over the wings to generate lift then yes

 

[scblack]

Yes.

I was about to say no, but of course it will. Engines push air, providing propulsion, not the wheels.

(I'm just soo smart. )

 

[Binaural]

Imagine this improbable scenario...

There's a plane (what type of plane is immaterial, as long as it's not VTOL) sitting on a conveyor belt. A huge-arsed conveyor belt the length of the runway. Now this conveyor belt is designed in such a way that it will perfectly match the speed of the plane, but travelling in the opposite direction!

So, for example, if the plane takes off to the west, the conveyor belt travels towards the east. It's a perfectly calm day with absolutely no breeze to speak of.

Will the aircraft be able to take off?



p.s. please try and answer this under your own steam [AKA using your brain not google]. and make the answer Yes or No followed by a brief description if you are that way inclined.

PPS - you're a wanker if you cheat at this.

Yes. The wheels will spin twice as fast, but will allow the plane to move forward under the power of the engines. Only limiting factor will be if the drag from the wheel bearings increases at very high velocities.

 

[josh_lives_here]

no, the plane needs to actually travel through the air in order to get enough airflow across the wings to get lift. How fast the wheels are going has nothing to do with it.


as far as i know the jets on an average plane do not create the lift, they create the movment through the air wich then makes the wings lift. planes dont fly because of the jets! do some research on bernoulies principle to find out how planes actually fly.

 

[skivi]

Yes. The wheels will spin twice as fast, but will allow the plane to move forward under the power of the engines. Only limiting factor will be if the drag from the wheel bearings increases at very high velocities.

my thoughts exactly , so the plane can generate enough thrust to allow suficient airflow over the wings to generate the required lift



hopefully the wheels are running a deemax hub

 

[Ryan]

No.

airspeed =/= groundspeed

Regardless of how fast the plane is travelling relative to the ground / runway / conveyor belt, if the wings aren't actually moving through the air then they can't generate any lift. I assume the purpose of this treadmill is to keep the plane stationary relative to the ground around it...so the plane doesn't actually move anywhere...just sits on this giant conveyor and runs it's engines while sitting in the one place?

If however you rigged up a giant hairdryer that could keep the plane stationary by blowing air over it with the same force the engines generate then it could take off no worries. You can hover a light aircraft in strong winds if you're a good enough pilot, I've seen it done with my own two eyes (as opposed to seen it done on TV / in a movie)

 

[S.]

no, the plane needs to actually travel through the air in order to get enough airflow across the wings to get lift. How fast the wheels are going has nothing to do with it.


as far as i know the jets on an average plane do not create the lift, they create the movment through the air wich then makes the wings lift. planes dont fly because of the jets! do some research on bernoulies principle to find out how planes actually fly.

Er, the jet engine thing is TOTALLY relevant. If it was the wheels providing the thrust, then it would be different. What we're saying however, is that the wheels are effectively just bearings, and it doesn't matter how fast they spin - the jet engines WILL propel the plane up to takeoff speed (which is relative to the air) because they provide thrust against the AIR not against the conveyor belt/ground.

 

[S.]

No.

airspeed =/= groundspeed

Regardless of how fast the plane is travelling relative to the ground / runway / conveyor belt, if the wings aren't actually moving through the air then they can't generate any lift. I assume the purpose of this treadmill is to keep the plane stationary relative to the ground around it...so the plane doesn't actually move anywhere...just sits on this giant conveyor and runs it's engines while sitting in the one place?

If however you rigged up a giant hairdryer that could keep the plane stationary by blowing air over it with the same force the engines generate then it could take off no worries. You can hover a light aircraft in strong winds if you're a good enough pilot, I've seen it done with my own two eyes (as opposed to seen it done on TV / in a movie)

Yes but there's nothing relating the plane's wheel speed to its actual speed relative to the air - they are FREE RUNNING wheels. Therefore, it will take off.

And you'd need air to be moving at the same SPEED not the same FORCE over the wings if you were to do that hairdryer thing. You'd also need to somehow incorporate an intercooler or whatever to make sure the air density is the same as it otherwise would be when the air is actually stationary and not being compressed by a giant turbine

 

[Red Rocket]

Ok smart guys...

You alienated 95% of your farkin.net audience right there

 

[josh_lives_here]

Er, the jet engine thing is TOTALLY relevant. If it was the wheels providing the thrust, then it would be different. What we're saying however, is that the wheels are effectively just bearings, and it doesn't matter how fast they spin - the jet engines WILL propel the plane up to takeoff speed (which is relative to the air) because they provide thrust against the AIR not against the conveyor belt/ground.

yeh i know the wheels are just bearings and have nothing to do with it but what i thought was that the jets on a plane only forced the plane forwards so that air would be moving fast enough past the wings so that the special shape of the planes wings could be effective.

so then if the jets are only making the plane move fast enough to keep up with the treadmill then there would not be enough air flowing past the wings to actually make the plane go up.

i mean exactly what ryan said its just im not as good at explaining it

 

[Carlin]

Imagine this improbable scenario...

...A huge-arsed conveyor belt the length of the runway...

The plane has plenty of distance to build up its airspeed.

 

[Dan.]

well the wheels would cause friction which would pull the plane backwards and the engines would push the plane but it would need the right amount of power. if it didnt get fast enough then it would still be on the ground so the answer is yes and also no because there are many variables.
ha and im only 13

 

[S.]

yeh i know the wheels are just bearings and have nothing to do with it but what i thought was that the jets on a plane only forced the plane forwards so that air would be moving fast enough past the wings so that the special shape of the planes wings could be effective.

so then if the jets are only making the plane move fast enough to keep up with the treadmill then there would not be enough air flowing past the wings to actually make the plane go up.

i mean exactly what ryan said its just im not as good at explaining it

It's ok, you and Ryan can be wrong together

Basically, the conveyor belt has no effect. Think about it. All it does is spin the wheels twice as fast, which makes no difference at all to whether the plane can build up speed, since the jets are pushing on static air rather than the ground.

 

[punk_downhiller]

okay umm this is probably a stupid reply and i will probs get bagged out for this but here goes....


No, the plane will not be able to take off because if the plane was trying to take off it would most likely remain stationary because the conveyor belt will be pulling the wheels one way at the same speed that the plane is trying to take off in the opposite direction

and it wouldn't matter if the wheels were free moving wheels because the friction between the wheels and the plane would still be enough to pull the entire plane backwards on the conveyor belt if the plane was not taking off

 

[spinner]

Yes , it will take off , as long as the tyres are rated to a speed double that of what they were designed to be used at !

The aircraft will propel itself through the air , regardless of the relative ground speed.

 

[No Skid Marks]

NO because of the surface of the conveyor belt. From my rough calculations on the air turbulence created from a smooth surface running at flying speed(normal), there would be to much turbalance for the planes wings to get lift.

 

[S.]

NO because of the surface of the conveyor belt. From my rough calculations on the air turbulence created from a smooth surface running at flying speed(normal), there would be to much turbalance for the planes wings to get lift.

Yeah? So you're saying that the boundary layer of air when the conveyor belt is moving at 220ish km/h (approximate takeoff speed) extends a full 4.5 metres high to reach the wing of a large jet plane? A likely story.

Edit: if that was true, then the turbulence caused by the plane wings themselves would mean that the plane could not generate lift even in normal flying conditions!