Will the plane take off?

[C0L0N3L]

If it were possible to put a plane on a treadmill that moves equal to the plane but in the opposite direction will the plane take off?

[stig0000]

If it were possible to put a plane on a treadmill that moves equal to the plane but in the opposite direction will the plane take off?

were never going to end on this one,,, lol

[350RRC]

No, because the plane needs air to move from the front over both sides of the wing surface.

The curve on top of a wing slows the air down compared with the time it takes to travel underneath, which is a straighter line.

This creates lower pressure on the top of the wing which creates lift, enabling the terrorplane to fly.

cheers, DL

[Bushie]

No, because the plane needs air to move from the front over both sides of the wing surface.

The curve on top of a wing slows the air down compared with the time it takes to travel underneath, which is a straighter line.

This creates lower pressure on the top of the wing which creates lift, enabling the terrorplane to fly.

cheers, DL

Other way around the air over the top of the wing has to speed up causing lower pressure so higher pressure below the wing gives it lift.

The plane won't take off, it needs movement, wing relative to the air to gain lift. On the treadmill it has ground speed but no airspeed.


Martyn

[seano87]

Not unless there is a whopping big fan in front of the treadmill as well :wasntme:

Seano

[TimNZ]

Or its very very very windy.

[Slunnie]

I think it will lift off.

It the plane is moving forwards and the treadmill is running backward by the same speed - well the ground speed is irrelevant really to an aeroplane as the wheels are not driven - drive is direct to the air that passes through the motor. What is important is the wind speed over the wings....

So if the plane needs to be travelling at 200km/h to lift off, then that is fine, the treadmill just means that the wheels will be spinning at 400km/h as about the only consequence (for the sake of this question)

[Lotz-A-Landies]

A number of factors are important here, mainly the wind speed and take off speed.

If the wind speed is enough to create sufficient lift for the aircraft to become weightless then the effect of the treadmill will be negated and the thrust of the turbine or propeller will cause the aircraft to rise initially slightly vertically then normal powered flight will take over.

The same effect can be observed by holding a model glider in the wind then releasing the model it will glide to the ground.

[C0L0N3L]

Other way around the air over the top of the wing has to speed up causing lower pressure so higher pressure below the wing gives it lift.

The plane won't take off, it needs movement, wing relative to the air to gain lift. On the treadmill it has ground speed but no airspeed.


Martyn

But the wheels should be irrelivant because the plane would use props or jets to push or pull air over the wings, therefore taking the treadmill out of the equation. The wheels are only used to reduce friction to allow the plane to take off normaly, so the wheels will just spin faster and the plane will take off.

[procrastination inc]

mythbusters have covered this conclusively

with an RC model and a full scale plane

your confusion comes from thinking the wheel bearings have enough friction to transfer a lagre enough force to counter the aircraft thrust. This does not happen

[350RRC]

Other way around the air over the top of the wing has to speed up causing lower pressure so higher pressure below the wing gives it lift.


Martyn

Yep. However, on top it would get slowed down at first, then must accelerate at some point along the chord to try to catch up.

Would this be at the max thickness of the section? Or somewhere near it?

cheers, DL

[seano87]

But the wheels should be irrelivant because the plane would use props or jets to push or pull air over the wings, therefore taking the treadmill out of the equation. The wheels are only used to reduce friction to allow the plane to take off normaly, so the wheels will just spin faster and the plane will take off.

During my younger Australian Air League days, I vaguely remember being told the jet/prop engine should not be thought of as forcing air over the wings, more as it creates a vacuum in front on the engine and pulls it forward, the resultant air movement over the wings then causes lift. Case in point would be Concord, it had engines at the rear of the wings, in no way actually forcing the air over the wings.

Seano

[harry]

maybe i should point out something to all you cretins -

carpenters use 'planes'

and unless you put the 'plane' in an -
aeroplane, aircraft, airplane,
or suchlike you will never get a 'plane' to fly.



ron, come home - in an aeroplane!!!!!!!!!!!!!!,
or ship, or something else.

[350RRC]

Here's one on the Canberra treadmill. Listen closely to the commentary........ classic laconic Oz humour.

YouTube - Russian IL-76 attemps to crash during takeoff

cheers, DL

[Bushie]

But the wheels should be irrelivant because the plane would use props or jets to push or pull air over the wings, therefore taking the treadmill out of the equation. The wheels are only used to reduce friction to allow the plane to take off normaly, so the wheels will just spin faster and the plane will take off.


Yep - you're right, had my line of thinking right in my head, just not in my fingers :o----:(:(:angel:

Airspeed will be created by the thrust from props or jets

[Lotz-A-Landies]

maybe i should point out something to all you cretins -

carpenters use 'planes'

and unless you put the 'plane' in an -
aeroplane, aircraft, airplane,
or suchlike you will never get a 'plane' to fly.
Except that the term "plane" is used commonly used to described a fixed wing aircraft that is documented first in Wikipedia and it's use is in the scenario discussing the property of achieving flight would be correct assumption. Any discussion asking the possibility of a carpenters tool achieving flight is plainly ridiculous and probably moronic of the author ("Moron" the term describing someone of low intelligence, whereas "cretinism" is a medical condition caused by iodine deficiency or hypo-thryoidism which has nothing to do with this thread)!

See: Wikipedia, the free encyclopediaWikipedia, the free encyclopedia "Plane

Plane or Planes may refer to:

Physical objects

* Aeroplane (Airplane), a fixed-wing aircraft
* Plane (tool), a tool or machine for shaving wood"

In fact the very scenario of an aircraft on a "treadmill" has been the subject of at least one quasi-scientific TV show.

[procrastination inc]

Harry, common usage is king in english

Or are you one of those who insist that the only correct plural for octopus is octopodes?

[seano87]

Harry, common usage is king in english

Or are you one of those who insist that the only correct plural for octopus is octopodes?

Wow. I just learnt something new. I only ever knew the plural as octopi. But.. right you are!

[B92 8NW]

I'm surprised this question caught out a few of the aviation people.

[350RRC]

the plane would use props or jets to push or pull air over the wings, therefore taking the treadmill out of the equation.

The props or jets force the whole plane through the air, which forces air over both top and bottom of the wings creating lift.

The airflow from the motors does not create lift without the wings. If it did, then the wings would not extend out out beyond the motors.

DL

[Captain_Rightfoot]

Someone is on the Happy Juice! :D

Can I watch while someone explains airspeed and ground speed. I'll just put some popcorn on. ;)

[StephenF10]

Yep - you're right, had my line of thinking right in my head, just not in my fingers :o----:(:(:angel:

Airspeed will be created by the thrust from props or jets

Not directly. The thrust from jet engines goes nowhere near the wings. Airspeed is created by the relative motion of the aircraft through the air.

Stephen.

[d@rk51d3]

Otherwise, you wouldn't need a runway. You would just give the engines some thrust, and she'd just leap into the air.

[procrastination inc]

"I only ever knew the plural as octopi."

and a "planely" incorrect pluralisation. But it is commonly accepted as correct and generally more correct than the anglecised plural octopuses or the translated greek root plural octopodes.

English is stupid

[Sprint]

to be accurate, we need to know if the plane is moving or not

if the plane is moving forwards at say 150mph, and the treadmill belt is moving in the opposite direction at 150mph, all it means is the wheels will be rotating at a speed equivalent to that of a plane moving along the ground at 300mph

now, the only trick is to get the plane to move forwards at faster than its required takeoff speed

[procrastination inc]

MythBusters Episode 97: "Airplane on a Conveyor Belt" (http://mythbustersresults.com/episode97)

[Slunnie]

You lot are all thinking parrallel and opposite vectors...


You should be thinking......



Harrier Jump Jet. :D



YouTube - Harrier Jet Vertical Takeoff

[350RRC]

Can I watch while someone explains airspeed and ground speed. I'll just put some popcorn on. ;)

Airspeed is the speed of the aircraft relative to the air, and nothing else.

Groundspeed is the speed of the aircraft relative to the ground, and nothing else.

Aircraft carriers always steam into the wind to maximize the airspeed (efficiency) of their aircraft when the planes take off or land, for a given groundspeed, which is the speed of the boat.

DL

[Slunnie]

MythBusters Episode 97: "Airplane on a Conveyor Belt" (http://mythbustersresults.com/episode97)

...


First some small-scale tests were performed with a model airplane on a treadmill and the plane was able to take off. For the large-scale test, the MythBusters used a 400 pound ultralight aircraft with a 2000 foot tarp under it. The tarp was pulled backwards to simulate a moving runway. The ultralight pilot had no trouble taking off. This is because the thrust of the airplane engines acts on the air, not on the ground.

[procrastination inc]

"for a given groundspeed, which is the speed of the boat."

you might need to rethink that

or at least reword it...

maybe I need to reread it :)

[B92 8NW]

MythBusters Episode 97: "Airplane on a Conveyor Belt" (http://mythbustersresults.com/episode97)

I noted this reply.

"You blew it big time. I am a pilot and I can tell you that the myth about the airplane conveyor belt is supposed to be confirmed. If you would have used an actual conveyor belt and the AIRPLANE’S wheels were allowed to free spin, then the airplane would not have been able to move when power for takeoff was reached. Your myth conveyor belt still allowed the wheels to contact a non-moving surface through the tarpoline. A non-moving plane(with no headwind either) like your pilot told you, will not have air moving over the wings, therefore would not be able to produce lift. Your “mythical” conveyor belt was just that, mythical. It did not act as a real conveyor belt. A real conveyor, would not have allowed any friction with the tires and surface. Your tarpoline did allow friction with the ground, and therefor forward motion for the plane to fly."

FROM A PILOT:eek:

[350RRC]

You should be thinking......
Harrier Jump Jet. :D


Try doing that in a Jap 4 swivel nozzle.

DL :)

[Slunnie]

, for a given groundspeed, which is the speed of the boat.

DL
I'm not pedantic about things, but thats definately not correct. Currents see to that.

[Slunnie]

Try doing that in a Jap 4 swivel nozzle.

DL :)
That sounds kinky. :lol2:

[procrastination inc]

FROM A PILOT...

meh, glorified bus drivers. what do they know about physics or engineering? :P

[aew849]

Being an ex navy pilot (and with 3 yrs on a carrier) with 20 yrs of flying there is really only one solution to this plane on conveyor belt bollox....

...go flying in a helicopter.:)



aew849

[350RRC]

"for a given groundspeed, which is the speed of the boat."

you might need to rethink that

or at least reword it...

maybe I need to reread it :)

And for Slunnie, aircraft carriers try to increase the efficiency of their planes when landing or taking off, by steaming into the wind. The ship is effectively adding some of its speed over groud to the planes airspeed to shorten take off or landing distance (on deck). Makes a dangerous operation a bit safer.

It is similar to the different runways used at airports.......... planes generally take off and land on a runway into the wind. They take off or land and pull up over a shorter distance. :)

DL

[C0L0N3L]

I noted this reply.

"You blew it big time. I am a pilot and I can tell you that the myth about the airplane conveyor belt is supposed to be confirmed. If you would have used an actual conveyor belt and the AIRPLANE’S wheels were allowed to free spin, then the airplane would not have been able to move when power for takeoff was reached. Your myth conveyor belt still allowed the wheels to contact a non-moving surface through the tarpoline. A non-moving plane(with no headwind either) like your pilot told you, will not have air moving over the wings, therefore would not be able to produce lift. Your “mythical” conveyor belt was just that, mythical. It did not act as a real conveyor belt. A real conveyor, would not have allowed any friction with the tires and surface. Your tarpoline did allow friction with the ground, and therefor forward motion for the plane to fly."

FROM A PILOT:eek:

One its the internet.. for all you know I could be an aeronautical engineer

2. Explain the scale model test which was on an actual treadmill..


"The plane accelerates by using jet engines to push against air, not wheels pushing against the ground. Imagine your standing on a skateboard which is on a conveyor belt. You are hanging onto a bar above your head that does not move. If you hold onto that bar, the conveyor belt wil move beneath the skateboard, but your relative position will not change. If you start to pull yourself along the bar, you will start to move forward, and the wheels of the skateboard will spin at the speed of the conveyor belt + the speed that your pulling yourself forward.

Now, back to the plane. The engines push against the air which does not move, the air is just like the bar in the scenario above. When the conveyor belt starts to move, the air will still be stationary, and therefore the engines will continue to push against it and move the plane forward. All that will happen is that the conveyor belt moving in the oposite direction will make the wheels spin twice as fast."

I'm confused as to why so many votes to no still

[procrastination inc]

I'm confused as to why so many votes to no still..

because it is a situation that doesn't relate well to daily experience

try a question on relativity >:)

[350RRC]

Haven't seen the scale model, but my bet would be propellor driven, ahead of the wings, with one or two motors pushing air over top and bottom of the wings.

Motor(s) big enough to create enough airspeed over wing surfaces to create lift.

You've answered the second part about the real plane yourself. No airspeed over the wings......... no lift.

DL

[seano87]

One its the internet.. for all you know I could be an aeronautical engineer

2. Explain the scale model test which was on an actual treadmill..


"The plane accelerates by using jet engines to push against air, not wheels pushing against the ground. Imagine your standing on a skateboard which is on a conveyor belt. You are hanging onto a bar above your head that does not move. If you hold onto that bar, the conveyor belt wil move beneath the skateboard, but your relative position will not change. If you start to pull yourself along the bar, you will start to move forward, and the wheels of the skateboard will spin at the speed of the conveyor belt + the speed that your pulling yourself forward.

Now, back to the plane. The engines push against the air which does not move, the air is just like the bar in the scenario above. When the conveyor belt starts to move, the air will still be stationary, and therefore the engines will continue to push against it and move the plane forward. All that will happen is that the conveyor belt moving in the oposite direction will make the wheels spin twice as fast."

I'm confused as to why so many votes to no still

I'm a nay-sayer, and I'll put it as I think of it. The question as I understand it is that if the treadmill is moving at the theoretical speed required for takeoff, there is still no air moving over the wings (the wheels are just spinning).

However, say the plane does lift off and is now a foot above the treadmill, it still has no forward motion or air moving over its wings creating lift, and hence would just drop straight back down - and as such it can't have taken off in the first place.

In the case of the argument that the propeller forces air over the wings and created the lift, and this happens as the treadmill is moving along at the speed required for lift to occur, the plane would be taking off with no forward motion and would be sitting above the treadmill... can a plane hover?

I may be wrong... but I'm not understanding the physics from the other side of the fence...

Seano.

PS. In the case of the mythbusters example, their light aircraft also had forward motion, it wasn't stationary to the ground underneath the tarp hence did have forward motion and airflow over the wings.

[procrastination inc]

the assumption seems to be that the plane can not achieve any forward movement relative to the air while the tread mill is running backwards.

I ask "Why is it so?"

watch the vid, it isnt so.

the little free wheels on the bottom of the plane just rotate faster as the plane gets purchase on the air.

[seano87]

the assumption seems to be that the plane can not achieve any forward movement relative to the ground while the tread mill is running backwards.

I ask "Why is it so?"

watch the vid, it isnt so.

the little free wheels on the bottom of the plane just rotate faster as the plane gets purchase on the air.


If it were possible to put a plane on a treadmill that moves equal to the plane but in the opposite direction will the plane take off?

My assumption comes from the original question... if it moves EQUAL to the plane. If the plane is going forwards relative to everything else, its not equal! ;)

IF the plane is going forward relatively, with enough airflow over the wings, then it will take-off, same as any other plane.

[B92 8NW]

One its the internet.. for all you know I could be an aeronautical engineer

2. Explain the scale model test which was on an actual treadmill..


"The plane accelerates by using jet engines to push against air, not wheels pushing against the ground. Imagine your standing on a skateboard which is on a conveyor belt. You are hanging onto a bar above your head that does not move. If you hold onto that bar, the conveyor belt wil move beneath the skateboard, but your relative position will not change. If you start to pull yourself along the bar, you will start to move forward, and the wheels of the skateboard will spin at the speed of the conveyor belt + the speed that your pulling yourself forward.

Now, back to the plane. The engines push against the air which does not move, the air is just like the bar in the scenario above. When the conveyor belt starts to move, the air will still be stationary, and therefore the engines will continue to push against it and move the plane forward. All that will happen is that the conveyor belt moving in the oposite direction will make the wheels spin twice as fast."

I'm confused as to why so many votes to no still

I was quoting a reply from the Mythbusters link - not expressing my belief. I was actually being sardonic.

Are you an aeronautical engineer?

[procrastination inc]

Originally Posted by C0L0N3L View Post
If it were possible to put a plane on a treadmill that moves equal to the plane but in the opposite direction will the plane take off?...


the surface of the treadmill relative to the ground has the same speed but opposite direction to the plane.

I agree, the original question posted is equivocal

[Lucy]

The treadmill is irrelevant, as planes are not wheel driven. The propellor or jets will pull/push the plane forwards through the AIR, the fact that the wheels are touching the ground - in this case a conveyor belt, doesn't matter.

[lardy]

mythbusters have covered this conclusively

with an RC model and a full scale plane

your confusion comes from thinking the wheel bearings have enough friction to transfer a lagre enough force to counter the aircraft thrust. This does not happen

i saw this too you are correct

[awabbit6]

Slunnie had it right back on the first page.


I think it will lift off.

It the plane is moving forwards and the treadmill is running backward by the same speed - well the ground speed is irrelevant really to an aeroplane as the wheels are not driven - drive is direct to the air that passes through the motor. What is important is the wind speed over the wings....

So if the plane needs to be travelling at 200km/h to lift off, then that is fine, the treadmill just means that the wheels will be spinning at 400km/h as about the only consequence (for the sake of this question)

As a Physics teacher, solutions to problems like this seem obvious to me. I can see how it is easy to be confused though.
I spent most of the MythBusters episode trying to get my wife to understand it - I'm still not convinced that she got it though ...

[procrastination inc]

here is a parallel closer to common experience.

If you swim upstream in a river at the same speed as the river flows down stream, you go no where relative to the bank. (car on a conveyor)

If you have a rope in the water tethered to a tree further upstream and you drag yourself along on that, you can make progress relative to the bank (plane taxis forward on conveyor)

Drag yourself fast enough and you can water ski :)
(plane flys)

[Bushie]

Being an ex navy pilot (and with 3 yrs on a carrier) with 20 yrs of flying there is really only one solution to this plane on conveyor belt bollox....

...go flying in a helicopter.:)



aew849

There is a thought that helicopters can't fly ........................................
They are that ugly the earth repels them ;);)


Love being in them though :D


Martyn

[BigJon]

The question as posted doesn't give enough information.

I read it as the airplane being stationary with the "ground" being pulled along under it.

Stationary means no airspeed.
No airspeed means no lift.
No lift means no takeoff.

As many others have noted, provided the airspeed is high enough, lift will overcome weight and the airplane will rise.

Engines whether piston prop jobs or jets provide thrust. The thrust moves the airplane forawards relative to the air. When the airspeed is high enough, up you go.

Engines don't (for all intents and purposes) force air over the wing to create lift.

[Shonky]

Can a hovercraft still travel up a flowing river? Yes...

The plane will take off - the only difference will be that the wheels will be free-spinning at twice the speed.

If this causes bearing failure before enough lift is produced, the plane may not take off I suppose... :p

[isuzutoo-eh]

"Will the plane take off?
If it were possible to put a plane on a treadmill that moves equal to the plane but in the opposite direction will the plane take off?"


So let me get this straight, the question did not exclude forward motion relative to a stationary frame of reference.
The 'ground' or treadmill frame of reference is travelling in the opposing direction to the aircraft.
The aircraft can be travelling at a speed of 100km/h North whilst the treadmill rotates at a rate of 100km/h South. So the aircraft's wheels are doing 200km/h to keep up.
The plane is still doing 100km/h relative to a stationary frame of reference, the wheel bearings are getting warm, and lift is still created due to forward motion. Take-off ensues.

How do I change my vote?

[Rudolf]

I have launched many gliders by just letting go. They went up with no foreward motion. And they have no wheels.

[StephenF10]

I have launched many gliders by just letting go. They went up with no foreward motion. And they have no wheels.

If you faced into the wind they DID have forward motion relative to the airflow before you even let go.

Stephen.

[HSVRangie]

The plane takes off.

the wheel speed has no effect on the plane as the plane is either pulled through the air by its prop/s or pushed by its jets.

Michael.

[Bigmark]

Ahhh you cant get wind speed if the actual plane is not moving, the wheels might be but not the plane- its like my defender stuck in mud with wheels spinning, i aint going anywhere--then again thats not likely to happen in a landrover.

[BigJon]

You can if it is a REALLY windy day :p.

I quite often fly my R/C planes at zero ground speed.

[Captain_Rightfoot]

I have launched many gliders by just letting go. They went up with no foreward motion. And they have no wheels.

Have we neglected to mention that that was on the face of a cliff? :D

[Jojo]

Funny how such a question can entertain a supposedly adult "auditory" for such a long time... :cool:;):D
To get things straight: an airplane needs lift to take off; lift is commonly created by air passing over the wings usually by forward motion with help of the aircraft's engines. Forward motion in the example is offset by the (hypothetical) runway moving into the opposite direction. The plane remains stationary. Hence no airspeed which equals no lift. The same would apply if you had a tailwind equal with the plane's ground speed. Basic physics, simply.
You can shorthen the length of runway needed considerably by taking off into a strong head wind or, if conditions are reversed and there is tail wind, the runway needs to be longer.

In short, the plane mentioned in the question will not take off, unless someone suddently stops the conveyor belt it is travelling on!

Cheers

[moose]

Goodness me, so much understanding of the needs of flight, yet so many wrong conclusions. the prop/jet driving the plane works by propelling the air around the plane, not the wheels underneath it. the conveyor belt makes no difference whatsoever.

The plane will take off. I refuse to read thru all the pages of this thread, but if you haven't done so already, look it up on youtube, mythbusters tested it.
YouTube - Mythbusters - Plane on a Conveyor Belt

[procrastination inc]

jojo, do the experiment

[Jojo]

...the prop/jet driving the plane works by propelling the air around the plane....

This is simply not the case, and the reason why any airport worth its salt is equipped with at least a looong runway which otherwise would be rendered obsolete...



jojo, do the experiment

I'd like to, mate, but I lack the necessary equipment in form of a suitable aircraft and an appropriately sized conveyor belt running at sufficiently high speed.

[procrastination inc]

it is the case jojo. but you seem to assume this means the original poster thinks that this is the direct source of airflow over the wings and the only source of lift.

the poster is trying to explain that planes don't apply thrust through the tyres, it is directly on the air.

Simple stuff that I'm sure you know

[moose]

oops, double reply

[moose]

This is simply not the case, and the reason why any airport worth its salt is equipped with at least a looong runway which otherwise would be rendered obsolete...


What exactly do you think propels the plane forward? It is the air around the plane being pushed in the opposite direction, creating the speed needed for the plane to take off. The wheel have no bearing on the situation, so unless you have your foot on the brake,

the plane will take off.

[warren9981]

If the plane will take off in this situation why do airports have long runways costing heaps of $$$ in land value. Why not put in a conveyor belt big enough to take a large jet and use a heap less space and therefore less $$$.;)
Also why would aircraft carriers not use this technique instead of runways. You could put a dozen treadmills across the deck of the carrier and take off 12 planes simultaneously.:D

[isuzutoo-eh]

Inertial frames of reference! Aah 1st year uni Physics, loved it.

The plane needs forward motion relative to the air. The ground has nothing to do with it, whether its a treadmill or terra firma.

The treadmill does not act on the wings, wind or propulsion.

The treadmill has no effect on the plane apart from making the wheels spin faster.

Windspeed must be the same for any other take-off no matter the length or type of airstrip at that air density.


Or at least thats what my physics and BAK taught me.

[Slunnie]

If the plane will take off in this situation why do airports have long runways costing heaps of $$$ in land value. Why not put in a conveyor belt big enough to take a large jet and use a heap less space and therefore less $$$.;)
Also why would aircraft carriers not use this technique instead of runways. You could put a dozen treadmills across the deck of the carrier and take off 12 planes simultaneously.:D
The planes have to land. Mind you, if they could reverse the converyor belt then perhaps the plane could just stop instantly when it hits the belt - and not need a runway. :D

[Jojo]

The treadmill has no effect on the plane apart from making the wheels spin faster.



...except for that the plane's forward motion, relative to the surrounding air, ceases...

[Slunnie]

...except for that the plane's forward motion, relative to the surrounding air, ceases...
Thats your flaw. The wheels just hold the plane up and let it roll. They are irrelevent to the forward drive on the plane - that all comes from the engines directly to the air - not the wheels.

[Rangier Rover]

I can't see how land speed can be very relivant to air speed other than friction of bearings and bow wave efect of the tyres. If it has air speed it will lift. Or fall off the tread mill and glide like a brick with the lack of air speed.

I think it will fly if we are talking a powered winged aircraft. Landing on a tread mill will take similar length in distance as conventional strip as the air speed is still relevant.

Better put on higher speed rated tyres and grease the wheel bearings if the treadmill is running backwards. If it was running forward the brakes wont help at all:eek:

Tony

[Captain_Rightfoot]

Two weeks ago I came back from Singapore. I was watching the inflight data tracker said that my aeroplane was travelling at 1100 kph. This impressed me because the speed of sound is around 1236 kph (depending on air density). Yet the cruise speed of the aircraft (Airbus Industries A330-300)I was travelling in is around 900kph.

So, for the conveyor belt fans does this mean they had the aeroplane really stoked up and was only 100kph (or thereabouts) below the speed of sound? :)

[B92 8NW]

The OP hasn't replied answering whether he is an aerospace engineer.

Whilst I'm not the type to ask digressive questions, I put the matter the professor at uni this afternoon. Naturally he validated the correct answer that the aeroplane will take off.

The argument of "why not have conveyor belts instead of large runways" doesn't hold water. As thrust is applied, the aircraft would move forward off the conveyor belt and still need to reach a certain velocity to take off. The undercarriage does NOT contribute any forward drive to the aircraft - although Airbus and Boeing are developing driven undercarriages in order to a) eliminate the need for engines to be used on concourses and b) provide regenerative power during landing.

[Slunnie]

b) provide regenerative power during landing.
:lol2:

I cant help but wonder if this is a waste. The small amount that it will make surely wont give a real benefit over the plane having to lug the weight of it and the maintanence costs..... especially when the planes are probably really the worlds largest polluters.

[BigJon]

The planes have to land. Mind you, if they could reverse the converyor belt then perhaps the plane could just stop instantly when it hits the belt - and not need a runway. :D

You can land a normal airplane vertically....



But you can't reuse it afterwards and the passengers get a bit upset! :p:p

[Rangier Rover]

You can land a normal airplane vertically....



But you can't reuse it afterwards and the passengers get a bit upset! :p:p
:lol2::lol2:
VTOL Engineering:eek:
Now that could be a great space saving idea + cull out overpopulation and create more employment wile moping it all up:twisted:

[StephenF10]

You can land a normal airplane vertically....



But you can't reuse it afterwards and the passengers get a bit upset! :p:p

You can if the aircraft is slow enough and the headwind is strong enough. While working at Parafield I heard the story of the Tiger Moth that took off into a stiff headwind. As the Tiger began to climb it gradually became stationary relative to the ground and then began to move backwards. The pilot realised what was happening and put it back down on the runway.

Stephen.

[Rangier Rover]

You can if the aircraft is slow enough and the headwind is strong enough. While working at Parafield I heard the story of the Tiger Moth that took off into a stiff headwind. As the Tiger began to climb it gradually became stationary relative to the ground and then began to move backwards. The pilot realised what was happening and put it back down on the runway.

Stephen.

My neighbor had a Auster gypsy and got overtaken by a semi trailer wile he was trying to fly over a hill in a head wind:eek: He near had to turn back.

Tony

[zulu Delta 534]

Going on the apparently more commonly held theory (with which I definitely don't agree) that the plane wont take off, does this mean that if an aircraft carrier sailed astern instead of forwards no aircraft could take off either.
Funny thing, but a seaplane can take off regardless of the direction of the current, and isn't that similar to a treadmill in effect.

A much more interesting question regarding the wonders of flight is;
How does a fly land on the ceiling upside down?
Does it reverse it's wing thrust?
Perhaps put it's feet upwards through it's hovering wings?
Does it do a roll?
It at least could take off on a treadmill!
Regards
Glen

[dullbird]

I just watched that film and I think there is being a bit of a mix up here...and I agree with what jo jo is saying.....

In that film that plane does not stay stationary.....I.e it hasn't lifted off the ground from the same spot! Which is what jo jo is saying is impossible I think and he is quite right unless of course your in a harrier jump jet.

the plane even though is on a convey still advances forward which gives it the opportunity to allow the air to flow over the wings and there for create lift.

Now if you are saying that the convey is moving at the same speed as the engines going forward that should me that the plane although going forward, is really due to the opposing speed of the conveyor is actually sat static. But how can we be sure in that film that both the car and the plan accelerated at the same speed? they both may well of had a target speed but it gives you no indication whether they reached it together at the same time....

This I feel means that at some stage the plane had the opportunity to gain ground as it may of some point been going faster than what the conveyor was backwards.

All this means to me is that a plane has the opportunity to take off on a shorter run was but not from a static point.

[Shonky]

I think it needs to be said that the question is "will the plane take off, or not?". It doesn't say that plane will stay stationary relative to the earth. ;)

If a plane needs a 100m long runway to take off, it will still need 100m of conveyer belt to do the same thing!

[dullbird]

I think it needs to be said that the question is "will the plane take off, or not?". It doesn't say that plane will stay stationary relative to the earth. ;)If a plane needs a 100m long runway to take off, it will still need 100m of conveyer belt to do the same thing!


I think you will find its how people interpret what take off means...take of in the conventional terms means no!

After all the original poster only mention a conveyor belt which is probably why some people are saying no, it doesn't say that the plane moves forward......when you jog on a running machine you don't move forward;).

Thats why I wrote that I agree with Jo Jo I think people are telling him he is wrong yet I think a lot are coming in from a different angle..and I don't think he is wrong looking at it form his point of view.

[aew849]

I would have liked to have seen the Mythbusters try two take off's.

1. Along a stationary belt, and
2. Along the moving belt as shown.

Record the distances the machine took to get airborne...given that all the factors such as throttle opening rate, brake release headwind etc etc were the same or could be factored out we could then make a better judgement.

The small ultralight in the vid was moving forward during the footage so no doubt creating an airflow over the wings. On top of that, the propwash also heads over the wings, assiting lift production. The is possibly some boundary airflow action happening as well.....this is friction dragging airflow along with it near a flat surface (such as conveyor belt). And finally it is likely that the experiment was set up into the wind (rule 1 in taking off).

So my view, there was enough airflow over the wings for the ultralight to take off in a very short distance...these machine have very low stall speeds, especially when the engine and prop are full throttle.

The original question I believe, discussed whether the aircraft would remain stationary to the ground, while the conveyor belt moved, and would lift vertically.......given the above comments re mythbusters, and my view of flying, I think it's bumpkin. Wings needs airflow over the upper and lower surfaces to create lift. The undercarriage could be wheels, snow ski's or floats which allow the aircraft to accelerate over the earth surface while the airflow over the fuselage increases.

But then again what do I care....helicopters are far more fun and we don't need runways or conveyor belts...no matter how ugly we are.:)

aew849

[strangy]

So much angst over this question.

Its all in the way you interperet the question and the technical outcome.

You are all wrong!

In some cases flght is achieved because the craft is so ugly, the ground actually repels it. i.e Helicopters.

The folowing may help in all other cases.

To quote Douglas Adams:

"Flying is not that hard, it is simply the act of hurling oneself at the ground
and missing"

This explains how Flies can land upside and along with cars and trucks, etc.
Now we dont need treadmills or wings do we?

Cheers

[WedWon]

You're all missing out on the crucial factor:

What colour is the plane?

[Shonky]

when you jog on a running machine you don't move forward;).

yes, but when you run on a running machine you are traveling relative to the surface you are running on, whereas a plane travels relative to the air. ;)


If a car was parked on the conveyor belt it would go backwards as it is fixed to the surface.

If a car was driving on the conveyor belt it would not move (same as the runner) as it is traveling equally opposing the surface.

If the car was in neutral (this is only theory - it assumes there is no friction), it would not move and the belt would just spin its wheels, as it is independent of the surface.

If the car was in neutral and had a large jet engine on its roof, it would move forward as the wheels are still independent of the surface (ie free spinning), but the jet is traveling through the air, taking the attached car with it.

[Shonky]

You're all missing out on the crucial factor:

What colour is the plane?


:lol2:

Deep Bronze Green?

[dullbird]

986245]yes, but when you run on a running machine you are traveling relative to the surface you are running on, whereas a plane travels relative to the air. ;)


If a car was parked on the conveyor belt it would go backwards as it is fixed to the surface.

If a car was driving on the conveyor belt it would not move (same as the runner) as it is traveling equally opposing the surface.

If the car was in neutral (this is only theory - it assumes there is no friction), it would not move and the belt would just spin its wheels, as it is independent of the surface.

If the car was in neutral and had a large jet engine on its roof, it would move forward as the wheels are still independent of the surface (ie free spinning), but the jet is traveling through the air, taking the attached car with it.

[/QUOTE]
which is exactly what the plane is doing when the belt goes backwards 100kph and the plane thrust forwards 100kph, I can't see how the plane travels relvant to air when the plane is yet to take off! Yes air plays a factor but surely so does the tarmac the wheels and other mechanical parts

in regards to the car being in nuetral yes and no I think...i think if you pulled the belt slowly up to a speed possibly not due to the wight pu on the wheels from the rest of the car....

If it was done quickly then momentum would play a part with the weight and then possibly. Thats just what I think anyway

[BigJon]

, I can't see how the plane travels relvant to air when the plane is yet to take off!

Move your hand quickly.

Do you feel the "breeze" on your fingers?

That is your hand moving relative to the air. You don't have to take off to feel it!

[moose]

which is exactly what the plane is doing when the belt goes backwards 100kph and the plane thrust forwards 100kph, I can't see how the plane travels relvant to air when the plane is yet to take off! Yes air plays a factor but surely so does the tarmac the wheels and other mechanical parts

in regards to the car being in nuetral yes and no I think...i think if you pulled the belt slowly up to a speed possibly not due to the wight pu on the wheels from the rest of the car....

If it was done quickly then momentum would play a part with the weight and then possibly. Thats just what I think anyway

Have a think about how a plane acheives its forward momentum, it is via thrust, and this is exerted on the air, not the ground. The wheels play no part in the takeoff apart from holding the plane off the ground.

The rest of the video is on youtube. They found out the plane's take off speed and accelerated the conveyor to that speed in the opposite direction. Since the plane's thrust is acting against the air, and the air is not affected in any significant way by the conveyor, the plane moves forward through the air until it acheives the speed needed to take off, regardless of how fast its wheels are spinning.

[dullbird]

ok help me understand......

Are you saying that If a conveyor is moving backward and a plane is moving forward at the same speed that the plane will still move forward from the opint it started from regardless and gain ground. It will not stay in a static point.

Just a simple Yes or no will be fine :D.........

I wonder if the same test works on a commercial jet:lol2:

[StephenF10]

Votes are running at more than two to one that the plane won't fly. which is surprising given the many good explanations of why it will.

Stephen.

[B92 8NW]

ok help me understand......

Are you saying that If a conveyor is moving backward and a plane is moving forward at the same speed that the plane will still move forward from the opint it started from regardless and gain ground. It will not stay in a static point.

Just a simple Yes or no will be fine :D.........

I wonder if the same test works on a commercial jet:lol2:

YES!:D

IT WON'T STAY AT A "STATIC POINT"

[moose]

ok help me understand......

Are you saying that If a conveyor is moving backward and a plane is moving forward at the same speed that the plane will still move forward from the opint it started from regardless and gain ground. It will not stay in a static point.

Just a simple Yes or no will be fine :D.........

I wonder if the same test works on a commercial jet:lol2:

Yes.
(For airspeed that is, which is what is needed for flight, ground speed is irrelevant)

[seano87]

Votes are running at more than two to one that the plane won't fly. which is surprising given the many good explanations of why it will.

Stephen.

I think it all comes down to how people interpret the original question. It stated that the treadmill is moving in the opposite direction at the same speed as the plane take-off speed. I think can be interpreted as equivocal and the plane is stationary relative to the actual ground (say treadmill at 100kmh, wheels spin 100kmh) OR plane moves forward as it normally would and it will take off, just with wheels at, say, 200kmh.

I can see how it can be interpreted both ways and will lead to the different conclusion. I hope that made sense, it does in my head.

Seano

[isuzurover]

I think it all comes down to how people interpret the original question.

Exactly. The original question is terribly worded.

The question says if the conyeor matches the PLANE's speed.
So the plane is moving forward at 100km/h, the belt is moving back at 100km/h, the wheels are doing 200km/h, the plane does not stay at a constant point in space, so therefore creates lift and take off.

The above is what would happen in any REAL situation with any REAL plane and conveyor. As stated, the wheels are not driven and the friction/drag from the wheels and bearings are insignificant.

Another wording of the question I have seen is if the conveyor matches the WHEEL speed of the plane. This scenario could possibly mean the plane stays stationary, IF the conveyor can instantly match the wheel speed of the plane, and turn infinitely fast. This scenario is impossible, and I suspect the conveyor would have to turn faster than the speed of light to negate the maximum thrust of a plane.

So, in any REAL situation, the plane would take off - the rest might as well be quantum mechanics.

[Captain_Rightfoot]

I dunno.. it's is irrelevant what is happening with conveyors, dogs, cats, planetary alignment etc - if the air moving over a planes wings does so at a speed which exceeds it's stall speed and assuming the aircraft can "rotate" it will become airborne. Once it is in the air you need some way of maintaining it's speed through the air...

[C0L0N3L]

Exactly. The original question is terribly worded.

The question says if the conyeor matches the PLANE's speed.
So the plane is moving forward at 100km/h, the belt is moving back at 100km/h, the wheels are doing 200km/h, the plane does not stay at a constant point in space, so therefore creates lift and take off.
.

Sorry.. but that is exactly what I intended to say.

also to person who asked if I was an aeronautical engineer.. no Im a high school student.

[dullbird]

Exactly. The original question is terribly worded.


The question says if the conyeor matches the PLANE's speed.
So the plane is moving forward at 100km/h, the belt is moving back at 100km/h, the wheels are doing 200km/h, the plane does not stay at a constant point in space, so therefore creates lift and take off.

The above is what would happen in any REAL situation with any REAL plane and conveyor. As stated, the wheels are not driven and the friction/drag from the wheels and bearings are insignificant.

Another wording of the question I have seen is if the conveyor matches the WHEEL speed of the plane. This scenario could possibly mean the plane stays stationary, IF the conveyor can instantly match the wheel speed of the plane, and turn infinitely fast. This scenario is impossible, and I suspect the conveyor would have to turn faster than the speed of light to negate the maximum thrust of a plane.

So, in any REAL situation, the plane would take off - the rest might as well be quantum mechanics.

Yeah......

[seano87]

Sorry.. but that is exactly what I intended to say.

also to person who asked if I was an aeronautical engineer.. no Im a high school student.

Well all it seems to have done is create ambiguity and a certain level of frustration.

So out of curiosity, how do YOU interpret your own original question COLON3L?

Seano

[C0L0N3L]

The plane is moving forward at x km/h, the treadmill is moving back at x km/h, the wheels are doing 2x km/h, the plane will continue to take off as normal because the treadmill is essentially irrelivant.. the wheels just have to spin twice as fast.. like i have said in a previous post.

[LOVEMYRANGIE]

I noted this reply.

"You blew it big time. I am a pilot and I can tell you that the myth about the airplane conveyor belt is supposed to be confirmed. If you would have used an actual conveyor belt and the AIRPLANE’S wheels were allowed to free spin, then the airplane would not have been able to move when power for takeoff was reached. Your myth conveyor belt still allowed the wheels to contact a non-moving surface through the tarpoline. A non-moving plane(with no headwind either) like your pilot told you, will not have air moving over the wings, therefore would not be able to produce lift. Your “mythical” conveyor belt was just that, mythical. It did not act as a real conveyor belt. A real conveyor, would not have allowed any friction with the tires and surface. Your tarpoline did allow friction with the ground, and therefor forward motion for the plane to fly."

FROM A PILOT:eek:

Well the ultralite did quite clearly move forward and they need very little forward motion to provide lift.

And just because its Mythbusters, it doesnt mean its true. Its quite easy to find gaping holes in what they attempt.

But, physics cant be ignored, if you have the plane traveling one way at 200kmh and the treadmill it runs on at exactly the same speed in the other, 200-200=0.
Either that or it runs "over" the treadmill coming in the other direction, crashes and burns in a big flaming heap at the end of the runway! :p

[350RRC]

The plane is moving forward at x km/h, the treadmill is moving back at x km/h, the wheels are doing 2x km/h, the plane will continue to take off as normal because the treadmill is essentially irrelivant.. the wheels just have to spin twice as fast.. like i have said in a previous post.

Yep, I've changed my mind on this and the above explanation is the most succinct.

The engines are only acting to push the plane through the air, treadmill and wheels are irrelevant, plane will gain speed relative to air and take off.

cheers, DL

[barney]

I'd like to quote Mr Garrison from South Park "there is no such thing as a stupid qestion, Just stupid people"

[Lionel]

Airspeed will be created by the thrust from props or jets

With respect, this is quite wrong. The air blast produced by the engines is not enough to gain lift sufficient to lift the aircraft. (Just as well - it would be extremely dangerous doing a mag test on a piston engined aircraft before take-off)

There has to be airspeed over the wings to create lift. All the engines do is to move the aircraft to produce airspeed, and hence, lift.

Cheers,

Lionel

[procrastination inc]

Airspeed will be created by the thrust from props or jets...

is only a very slightly ambiguous statement.

Airspeed is gained by accelerating the plane through the air. The force to accelerate the plane is applied as thrust from the props or jets.

Read that way, bushies statement is correct

[DiscoStew]

The situation as described occurs every day all over the world.

The planet is spinning in one direction, just like a big mother of a conveyor belt. Many aircraft take off pointing in the opposite direction, many in the same direction.

Adding another conveyor belt would have a minimal impact one way or the other on the big conveyor belt that is spinning so fast we go around the whole planet in just 24 hours.

As many have explained neither of these conveyor belts have any relevance to the lift.