[Closed] What is this aircraft on a conveyor belt that people often quote?

have only heard about this?am wondering what it is about also ❓

Good god Nooooooooooooooooooooooooooooooooooo!

It's the old debate about whether an aircraft on a treadmill would be able to take off, IIRC. No idea whether that's from a thread or not.

I heard it's the only way that South African aircraft can avoiding hitting antelope when they take off.

The argument happens because some idiots think the aeroplane will take off [i]even if the conveyor belt is running at the same speed as the aeroplanes wheels!!![/i] I guess some folk just don't understand physics

Need to watch Mythbusters.

There have been many threads about it over the years, as Pyro said it's just that debate.

To nip it in the bud... Yes it can, as the engines provide the thrust not the wheels, but the treadmill would have to be as long as a normal runway. People think of it as gaining pace on the spot and being able to take off in no space, which is bollocks, the airspeed at take off would be identical, the wheels would just be going rather faster.

It's a bit like the P, only you didn't pay for the privilege to be a pre-hacked member

and we're off...

Mythbusters covered this a while ago.

See - I told you. There's always some idiot (njee in this case) that just doesn't get it at all.

allthepies - Member
and we're off...

and so it begins......

lol at druidh

🙂

But surely it's the speed (pressure/lift) of the air flowing under and over the wings that give lift to make a plane take off?

A better question would be: can you blow air at a stationary plane and make it lift off the ground? Let's ignore for a moment how you would do that.

Yes, it's called a wind tunnel.

karinofnine - how would there be any air flowing under the wings of the treadmill was running at the same speed as the wheels? There wouldn't be any forward motion to generate lift.

And your second example is commonly known as "A Kite" (google it).

I am 100% with DruidH. Air speed across the wings is all that matters. If the conveyor constantly matches matches the acceleration of the aircraft then the air over the wings is static and the thing will never take off.

Unless the rotation of the wheels generates lift?

Exactly, the plane has to travel forward through air - I was disregarding the treadmill entirely.

We used to go to RAF Coltishall and watch the Lightnings take off. Fantastic.

Oh, they didn't use a treadmill either 😉

Surely everyone knows this by now?

(And you always choose the other door, as it's more likely you'll win a car.)

No, but the wheels aren't powered, so the speed of the wheels is 100% irrelevant!

Can you push a bike along a conveyor belt?

That's what the engines are doing - pushing the plane forward. If the conveyor matched the speed of the plane, at takeoff the airspeed would be 150mph, whilst the wheels would be doing 300mph. It'd still take off just fine!

A car however, or a bike you were trying to cycle, would not move.

druidh.. stop it, you are being naughty!!!

Next you'll be telling me not to swap doors when offered the chance too!!

Edit: mike... snap!!

I think Njee is playing games.

I got another one....

If I am playing table tennis with a mate ( I do have one...)

on a flat bed truck

and it turns a corner just as I hit the ball...

which side of the table does the ball go off?

njee20 - that's the way I picture this too.

eviljoe - Member
I got another one....
If I am playing table tennis with a mate ( I do have one...)
on a flat bed truck
and it turns a corner just as I hit the ball...
which side of the table does the ball go off?

Top side. Fact.

A rocket, strapped to a skateboard on a supermarket checkout?

How about this one...

I'm running forward carrying a ball and I throw it behind me. Does the ball travel forward or back?

That's because you are right.

what was that old one about birds in a lorry?

Antelope

On a bicycle

In a wind tunnel

will it make any difference if the wheels are 26in or 29in?

[img] [/img]
This would need forward speed equal and opposite to the speed of the treadmill to remain stationary prior to attempting to take off.
Can it go forwards and vertically upwards at the same time?
If it was on the treadmill going 'forwards' (ie stationary but forwards relative to the treadmill) while the pilot went through the pre-flight checks and plane was readied for take-off would the act of switching from 'forward' to vertical movement sufficiently impeed the forward movement for it to fall off the back of the treadmill?
I suspect a plane capable of vertical take off may be the only kind not able to take off from a treadmill.

Antelope

On a bicycle

In a wind tunnel

will it make any difference if the wheels are 26in or 29in?

Yes...

Now where was that video of the ostriches and the rally car?

You've missed out one crucial detail that the OP needs to know. There were at least TWO subtley different versions of the questions meaning that arguements could run and run...

1. the belt matches the aircrafts speed

2. the belts speed always matches the speed of the wheels.

Next question.
Aircraft needs to do 200mph to take off.
Aircraft carrier is travelling at 100mph (for ease of maths rather than realism)
Aircraft accelerates and has a 'ground' (carrier) speed of 100mph when it reaches the end of the deck.
Airspeed is 200mph so it should fly.
Am I right?
Now imagine an aircraft carrier doing 100mph in reverse.
1) Aircraft has a ground speed of 100mph when it leaves the deck at the bow, air speed is 0 and it crashes.
2) Aircraft has a ground speed of 200mph when it leaves the deck at the bow, air speed is 100mph so it crashes.
3) Aircraft has a ground speed of 300mph when it leaves the deck at the bow, air speed is 200mph so it flies.
Does this help?
.
Doesanyone have either a really large treadmill or a really fast aircraft carrier so that we can proper observations rather than just relying on conjecture?

Is that rotational speed or forward speed HH?

I suspect a plane capable of vertical take off may be the only kind not able to take off from a treadmill.

HoratioHufnagel has it, unfortunately many people seem to miss this. People don't read the question properly.

Thrust SSC would still be able to break the world speed record on a treadmill.
If the turbine drove the wheels rather than just 'pushing' it along, then it wouldn't.

Thinking about it a bit more. We also need to specify what kind of propulsion the aircraft has. I am wondering if an aircraft with high lift wings and and powered by a prop might be able to manage take off.

Yes Scuzz, but it would be having to use all it's thrust in a forward direction to stay on the treadmill, switching to vertical isn't instant so the loss of forward thrust would see it shot off the back of the treadmill before it had got airborn.

Aaaaaaaargh... andrewh... scuzz.. etc...

Firstly, the treadmill only moves if the aircraft, or it's wheels, depending on the question, moves... so, a stationary aircraft would be sat on a stationary treadmill.

Next... uphillcursing, unless there is some kind of aircraft which propels itself through it's wheels, it doesn't matter how it's powered...

And finally, dear god please stop me reading and responding to this thread... I thought I got over it the first time this appeared!!!

Surely using a conveyor belt running in the same direction as the intended takeoff is no different to the catapult takeoff methods used on an aircraft carrier,just a different form of propulsion, assuming that the velocity of the conveyor belt can match the takeoff speed of the aircraft. The point being that it is the speed of the airflow over the wings that gives a plane lift, not the speed of the wheels

A treadmill on the other hand... the plane would have to travel the speed of the treadmill PLUS its own take off speed in order to counteract the effects of the treadmill running in the opposite direction.

Mussssssssssst resissssssssssssst....

Firstly, the treadmill only moves if the aircraft, or it's wheels, depending on the question, moves... so, a stationary aircraft would be sat on a stationary treadmill.

Oh. I thought we had a powered one.

Funky, I dont believe it is possible in theory. Please see earlier post. What I do think "might" be possible is due to how a prop works, ie accelerating a cone of air. It "might" be possible that with a high lift wing this cone of air may be enough to generate the required lift due to airspeed over a portion of the wing whilst drag on the rest of the aircraft keeps the groundspeed(speed on the conveyor) to zero.

if that makes sense

This is an amusing thread, [i]Even though[/i] I am far from sure who is taking the mickey and who doesn't realise... There appears to be an element of double bluffing. Reminds me a little of Mornington Crescent... Love it.

Oh god noooooo...

uphillcursing... it has nothing to do with that. The way the aircraft moves forwards is by forcing air backwards, either by the use of a prop, or a jet. The wheels are merely there to reduce the coefficient of friction between the fuselage and the ground. If the wheels provided any motive force then how does an areoplane fly once it leaves the ground?

To nip it in the bud... Yes it can, as the engines provide the thrust not the wheels, but the treadmill would have to be as long as a normal runway. People think of it as gaining pace on the spot and being able to take off in no space, which is bollocks, the airspeed at take off would be identical, the wheels would just be going rather faster.

Couldn't we just lock the thread after this?

I'm pretty good at mechanical, dynamical, type physics and maths. This is what I believe would happen. I've talked to a pilot, and he confirmed my assumptions.

Not sure this really proves anything as I think the plane was going faster than the belt when it took off, it was definately moving forwards before it left the ground.
.
Scuzz, an infinately long treadmill? Then you would be right. However most, maybe even all, treadmills are not infinately long. I was assuming that it would be about the length of the plane, which is much realistic 😉

Another thought, as the plane accelerate does the treadmill accelerate to match? If not all the plane has to do is out-accelerate the treadmill. If the treadmill is at a constant speed then Realman and whoever he is quoting are correct, but I think they have answered the wrong question.

Shirley the most important question in all of this is what tyres for the conveyer belt

andrewh - Member
Another thought, as the plane accelerate does the treadmill accelerate to match? If not all the plane has to do is out-accelerate the treadmill. If the treadmill is at a constant speed then Realman and whoever he is quoting are correct, but I think they have answered the wrong question.

I would have thought that the aircraft size was critical, you would need something Bomber size

Surely it also depends on the viscosity of air. If it was abnormally viscous then the conveyor would drag it backwards (or was it forwards?) which might or might not affect the air speed relative to the wing.

Funky.... Agree totally. What I am trying, and failing it seems to say . Is that to achieve any forward motion there has to be a force exerted by the prop. This is a force localised behind the diameter of the prop. If the diameter of the prop extends to cover a length of wing then this section will have airflow and therefore lift. The rest of the wing will not experience any any airflow and therefore produce no lift. given that conveyor keeps the aircraft stationary relative to a point on the ground.

Will the amount of airflow ever be big enough to let the aircraft take off? I think this may depend on the diameter of the prop. (maybe)

Am i dreaming? Is this really the nightmare returning to haunt me again?

Someone please make it stop!

Noooooooo.....

*deep breaths*

What you seem to be trying to answer is, can an aircraft ever take off will no forward speed, just the effect of the propwash over the wings. I'm fairly sure the answer to that question would be no.

But that is not the situation here.

There is nothing stopping the prop pulling the aircraft forwards. The treadmill is just a distraction.

Unless there is some way for the speed of the treadmill to influence the aircraft, which has non-driven, freely-spinning wheels, then there is no way for the treadmill to stop an aircraft taking off.

Uphillcursing, are you being serious? Lol

Beats a "what tyres for XXX " thread if nothing else 😉

Beats a "what tyres for XXX " thread if nothing else

we haven't even started on the 'what tyres for conveyor belts'question yet...

Conti Vert Pros obviously...

Next!

It has already been asked.
But not answerd.
Nobby nics for general all-round treadmills.
Do they do them in 42x23" folding?
.
[EDIT] Funky's answer is better.

Well am I the only one wondering if it comes with a crown race?

uphillcursing - Member

Will the amount of airflow ever be big enough to let the aircraft take off? I think this may depend on the diameter of the prop. (maybe)

Surely it also depends on the viscosity of air. If it was abnormally viscous then the conveyor would drag it backwards (or was it forwards?) which might or might not affect the air speed relative to the wing.

I may have made it all up, though.

Noooooooooooooooooooooooooooooooooo

Scuzz, could we experiment with a hyrofoil and an infinity pool to test the theory by using something more viscous than air? Would the principle be the same?
Do they make hydrofoils with a prop at the front?

😛

Right off to bed. Might try and dig out a text book from the attic tomorrow.

Same principle, we'd need an impellor powered submarine shaped like a plane with a hydrofoil, and a large pump system to simulate the forward airflow the plane would generate from thrust and a sheet of plywood to simulate the treadmill surface such that boundary layer viscous effects could be taken into account!

There needs to be a whole new definition for people like you lot. Troll is wrong, as it implies nastiness and a 'victim'. You lot know exactly what you are doing, and you derive an almost perverse pleasure from it. I shall call you gnomes, and I require you all to sign the gnome offenders register at once. 😆

@ the OP, yes to the first, but that depends on when you joined, and no to the second question, because I can't be arsed.
HTH.

[img] [/img]
No reference points to gauge speed but doesn't look like it's going very quickly.
Whole tribe of gnomes over on the stupid headset question thread.

What if the treadmill was travelling at almost the speed of light?

Not sure. Depends what the chaps at CERN find, they may be able to get the plane to go a bit quicker than that (once they have found a way of scaling it up from one nuetrino).
.
BTW Scuzz, I have added your last post to my purple book of silly quotes. No one in the whole of history has ever said that sentance before.

[img] http://i93.photobucket.com/albums/l41/xeroate/plane.jp g" target="_blank">http://i93.photobucket.com/albums/l41/xeroate/plane.jp g"/> [/img]
Can't quite make out treadmill from this angle.

as tthew hints at with Thrust SSC on the treadmill.... the jet engine is pushing against the air that it piles up behind itself

the wheels just allow the thrust power to used as efficiently as possible

imagine thrust lying on the ground dragging itself along on its belly, it could still move it'd just need more power* to counteract the chassis/ground friction
- Or lying on the treadmill pushing against the direction of the travel, needs much more power still
- but add wheels to thrust and the wheels and bearings allow the treadmill resistance to be nullified, the wheels can spin as fast as they want as long as the bearings don't pop

*trademark J Clarkson

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