Airplane on a treadmill

[VladTepes]

The question, as usually seen, is as follows.



An airplane is sitting at rest on a very powerful treadmill. You are at the controls of the treadmill, while I am at the controls of the airplane. On some signal, I begin to attempt to take flight in the plane, and you attempt to match my speed to try to keep me stationary. Will the plane take off?



If you think that it won't fly, then take a good hard look at yourself & then read this:


Airplane on a Treadmill Definitive Analysis (http://www.airplaneonatreadmill.com/2008/01/airplane-on-treadmill.html)

[67hardtop]

The wheels are in contact with the ground but the wheels are NOT driven, so of course, the plane will take off. I'm not too smart but i'm not stupid either. Yes i've seen the Mythbusters experiment on tv and even before they attempted the experiment i said that to my mate who was watching with me. I won $100 coz he bet me that it wouldn't take off. As soon as i secured the wager i explained why it would take off and he still didn't believe me so i waited till the experiment was over and collected. Its just a brain fart experiment. His did, mine didn't.

Cheers Rod

Sent from my GT-I9507 using AULRO mobile app

[ramblingboy42]

I may be late into this but the aeroplane (not airplane) clearly wont fly in that situation.

It will remain completely stationary unless more engine power is applied or the speed of the conveyor changes.

If the speed of the conveyor matches the input of the aeroplane there will be zero airspeed.

The groundspeed will be high but no lift is being produced by the wings.....see.....the aeroplane is not moving through the air , only rolling on the conveyor using it's engine power to to keep up to the conveyor operator's input......or conversely the conveyor operator is keeping abreast of the pilot's input.

No argument. It won't fly.

[vnx205]

It will take off. The conveyor belt has no effect on the thrust provided by the prop.

[pop058]

I may be late into this but the aeroplane (not airplane) clearly wont fly in that situation.

It will remain completely stationary unless more engine power is applied or the speed of the conveyor changes.

If the speed of the conveyor matches the input of the aeroplane there will be zero airspeed.

The groundspeed will be high but no lift is being produced by the wings.....see.....the aeroplane is not moving through the air , only rolling on the conveyor using it's engine power to to keep up to the conveyor operator's input......or conversely the conveyor operator is keeping abreast of the pilot's input.

No argument. It won't fly.

I would have thought the engine (prop) was producing air flow across the wings and therefore creating lift. Also if the plane is rolling on the conveyor and keeping up with it, then the net ground speed would be zip.

[FatBoy]

The treadmill won't be able to keep the aircraft stationary, no matter how fast the treadmill goes. The engines on aircraft don't drive the wheels, they only pull and/or push the aircraft through the air. Therefore once the aircraft gets enough airspeed via the thrust from the engines, it will become airborne.

[cripesamighty]

I know it's probably the wrong analogy, but in my head I think of an aircraft on skis that is gliding along on the ice and taxiing before for takeoff. Once the throttle is advanced, the aircraft moves forward until sufficient airspeed is attained and the aircraft can lift off. Doesn't matter what the undercarriage is doing or what surface it is on (so to speak).

[cjc_td5]

The treadmill won't be able to keep the aircraft stationary, no matter how fast the treadmill goes. The engines on aircraft don't drive the wheels, they only pull and/or push the aircraft through the air. Therefore once the aircraft gets enough airspeed via the thrust from the engines, it will become airborne.

Provided the treadmill is long enough of course...... (about a runway length long..)

[Blknight.aus]

but if you set the treadmill steep enough the plane wont generate enough thrust to roll the wheels up the tread mill as it will be acting as a wheel chock...

if the plane cane move laterally it cant generate airspeed over the wings to generate lift.

unless its a harrier which is out because its a jet.

What if it was an osprey, they have props.

[Slunnie]

Here is the truth!

https://www.youtube.com/watch?v=NgR8grJGNEQ

[Fourgearsticks]

An aircraft fly's because of air flow over the wings, what the wheels do has nothing to do with flight, only allowing the aircraft to move on the ground.

If the rubbish about making an aircraft fly impossibly by spinning up the wheels is true then why don't aircraft manufacturers have facility for driving the wheels?

The mythbusters "experiment" was using a stol machine that becomes airborne at a very slow speed, the only reason it flew was because it had a lot of power and it actually took off itself, there just happened to be a carpet being pulled out from under it. Without the engine running full power it would merely just roll.

An example is of windy conditions with the aircraft tied down, in very high winds an aircraft will "fly" on the tie downs with the wheels remain stationary.

A true test would be to tether the aircraft/model so it remains stationary but can lift off, also don't use the aircraft propulsion. All you have is something with it's wheels spinning.

A farmer came up to me many years ago and commented on the aircrafts wheels, they were typical Goodyear's with only lateral grooves. He asked with so much clover on the strip do I get much wheelspin on take off? :)

[Homestar]

I may be late into this but the aeroplane (not airplane) clearly wont fly in that situation.

It will remain completely stationary unless more engine power is applied or the speed of the conveyor changes.

If the speed of the conveyor matches the input of the aeroplane there will be zero airspeed.

The groundspeed will be high but no lift is being produced by the wings.....see.....the aeroplane is not moving through the air , only rolling on the conveyor using it's engine power to to keep up to the conveyor operator's input......or conversely the conveyor operator is keeping abreast of the pilot's input.

No argument. It won't fly.

Plenty of argument - Of course it will fly. The engines are pulling on the air, the treadmill rolling away merrily underneath the plane has nothing to do with it.

[Gordie]

A farmer came up to me many years ago and commented on the aircrafts wheels, they were typical Goodyear's with only lateral grooves. He asked with so much clover on the strip do I get much wheelspin on take off? :)


Haha, love it!!!

[Fourgearsticks]

Plenty of argument - Of course it will fly. The engines are pulling on the air, the treadmill rolling away merrily underneath the plane has nothing to do with it.
Sorry to disappoint you, no fly. See above post

[Homestar]

Sorry to disappoint you, no fly. See above post

Nope, it will fly - did you even read the article in the first post? I've seen more than one experiment show it will fly and the physics and math proves it too. The thrust of the engine will push the plane forward creating air speed which causes lift. What's happening at the wheels is irrelevant.

You said it yourself - airspeed is created from the engines and has nothing to do with the wheels. If the wheels had anything to do with flying, they'd be driven like a cars.

Do the math, don't rely on a YouTube video or a TV show.

[Gordie]

I concur with homestar, an aerofoil requires airflow to create lift. If enough thrust is given to make the aircraft move forward through the air, then lift will be created.
Picture a float plane on a tidal piece of water, say the plane requires 65knots (airspeed) to lift off...and it is being pushed backward by the tide at 5knots, obviously once the engine(thrust) has pushed the plane to a 'ground speed' of 70knots, it will fly.

[Fourgearsticks]

Your not arguing the point of the conveyer.
Yes an aircraft WILL fly if you power up the engine and take off, that's what it's supposed to do. An aircraft will not take off if you just spin it's wheels and do not power up the engine. If the moving belt is long enough, the aircraft is not restrained and you use the engine, what normally powers an aircraft to flight then yes an aircraft will take off a moving belt.
To fly an aircraft requires moving air over the entire wing surface above the stall speed then it will fly. That moving air is usually provided by powering up and using thrust to accelerate the aircraft to flight.

An obvious point would be a glider. If you stick a glider on a conveyer it will not take off, it can't.

Gordy's point about float aircraft. They can land in a moving body of water, either with the flow or against it, the aircraft still fly's one way or the other, the only difference being the actual waterspeed touchdown/take off being different.

Taking off or landing into wind or downwind being the same, aircraft still takes off at 60ish knots airspeed no matter what, the groundspeed into wind is less, tailwind more.

So if you lot are right we will be seeing airliners shortly with powered wheels? I'm sure Boeing will be keen to take on some of your vast aeronautical knowledge to help produce the next generation airliners. Perhaps you will go into civil airport construction and help producing the first moving runways?
So who's going to stick a glider on a moving belt and film it flying? Why do gliders waste money on tugs and winches when they could just get a conveyer belt to launch?
No good tomorrow being Sunday you lot will have to wait till Monday to patent all these cracker idea's :D

[vnx205]

You are the only one who thinks the wheels are important. They are only there to reduce the rolling resistance on the ground. They don't make the plane fly.
The plane will take off because the treadmill doesn't affect the thrust from the propeller.

[vnx205]

Have you read the question quoted in the original post?
Saying that the treadmill "attempts" to match the speed of the plane is a good way to pose the problem. The treadmill has no effect on the plane.
The plane takes off no matter how fast the treadmill goes.

[pop058]

I don't believe anyone is saying a plane will take off on a conveyor just because the wheel are rotating. My read is that as the prop is turning to keep pace with the movement of the conveyor then logically there is air flow over the wing surfaces. This airflow is causing lift allowing the plane to takeoff.

[Homestar]

Your not arguing the point of the conveyer.
Yes an aircraft WILL fly if you power up the engine and take off, that's what it's supposed to do. An aircraft will not take off if you just spin it's wheels and do not power up the engine. If the moving belt is long enough, the aircraft is not restrained and you use the engine, what normally powers an aircraft to flight then yes an aircraft will take off a moving belt.
To fly an aircraft requires moving air over the entire wing surface above the stall speed then it will fly. That moving air is usually provided by powering up and using thrust to accelerate the aircraft to flight.

An obvious point would be a glider. If you stick a glider on a conveyer it will not take off, it can't.

Gordy's point about float aircraft. They can land in a moving body of water, either with the flow or against it, the aircraft still fly's one way or the other, the only difference being the actual waterspeed touchdown/take off being different.

Taking off or landing into wind or downwind being the same, aircraft still takes off at 60ish knots airspeed no matter what, the groundspeed into wind is less, tailwind more.

So if you lot are right we will be seeing airliners shortly with powered wheels? I'm sure Boeing will be keen to take on some of your vast aeronautical knowledge to help produce the next generation airliners. Perhaps you will go into civil airport construction and help producing the first moving runways?
So who's going to stick a glider on a moving belt and film it flying? Why do gliders waste money on tugs and winches when they could just get a conveyer belt to launch?
No good tomorrow being Sunday you lot will have to wait till Monday to patent all these cracker idea's :D

Then I'm not sure what we are arguing about - that is the point of the experiment. Of course a plane won't take off if you don't power the engines up - it won't do that on a runway either...

[ramblingboy42]

Just a simple question....

Are there any trained pilots in this forum who believe that this aeroplane will fly off the conveyor?

I think the only people who believe it will , are those who do not know the theory of flight and the difference between airspeed and groundspeed.

[vnx205]

The only people who think the plane won't take off are those who are misled by the things mentioned on the question.
The question makes them think the treadmill will affect the plane. It won't. It has no effect.
Pilots are just as likely to be sucked in as anyone else.
The real issue is not whether you understand how planes fly.
The issue is whether you allow yourself to concentrate on the wrong thing and assume the treadmill will actually have an effect.
It won't.
The plane will take off.

[BigBlackDog]

Something to ponder. Drag on the wheels will slow the plane from getting to take-off airspeed, such as taking off on grass, long grass in particular, takes a lot longer for a given set of conditions. The conveyer will impart drag on the wheels I would guess, but I could be wrong.
A mate of mine, also a pilot, was asked by a guy once what was driving the wheels for take-off. Apparently the guys girlfriend ****ed herself laughing at him :)

The original question is poorly worded I think,which is confusing people. I think I get what it is trying to say but it's not a real clear picture

[FatBoy]

Just a simple question....

Are there any trained pilots in this forum who believe that this aeroplane will fly off the conveyor?

I think the only people who believe it will , are those who do not know the theory of flight and the difference between airspeed and groundspeed.

Yes, me. It will fly off the conveyor belt (if the belt is long enough).

No matter what speed the conveyor belt does, it cannot stop the aircraft moving through the air. The wheels are not driven on the aircraft, so are irrelevant in this question. The wheels will just rotate faster than the airspeed.

Have a look at the question again:

An airplane is sitting at rest on a very powerful treadmill. You are at the controls of the treadmill, while I am at the controls of the airplane. On some signal, I begin to attempt to take flight in the plane, and you attempt to match my speed to try to keep me stationary. Will the plane take off?

The pilot attempts to take flight, so to do this they increase the airspeed of the aircraft. Aircraft don't use the wheels to drive it on the ground. So it will use a propellor or jet to create thrust.

The person with the conveyor belt attempts to match the speed to try and keep it stationary. As stated before, and by many on here, what the wheels do are independent of the airspeed. Try as the person with the conveyor belt may, they can't stop the aircraft with the conveyor belt only.

So to use some basic figures, if the aircraft gets airborne at 60 knots, then it will need 60 knots of airspeed. If the person with the conveyor belt makes the belt go at 60 knots to try and keep it stationary, all that will happen is that the wheels will rotate at 120 knots (groundspeed relative to the aircraft), and the aircraft will maintain 60 knots of airspeed.

So, to repeat, IT WILL FLY.

I'm happy to be proven wrong, although I'm not. :p

[vnx205]

The original question is not poorly worded.
It is deliberately written to suck people in and obviously works. There are a lot of people who get fooled into thinking the treadmill will have an effect. It won't .

[vnx205]

Just a simple question....
.

A more important simple question.

When you eventually see the light, will you acknowledge that like so many others you have been tricked by a cleverly worded question? :)

The plane will take off.

[bee utey]

I'd like to pose a slightly different question: Could you launch a plane (engines not running, wheel brakes firmly applied) by using a perfectly flat and extremely long conveyor belt? :)

[Ferret]

I think the only people who believe it will , are those who do not know the theory of flight and the difference between airspeed and groundspeed.

Provided the friction in the wheel bearings is minimal (and what is the point of a wheel bearing and a non driven axle if this is not true) then the plane will take off under all conditions of conveyor movement, even if the conveyor is running so fast that the wheels of the plane are rotating backwards as the plane itself is moving forwards under the thrust created by its propeller.

The only reason the plane moves at all when the conveyor moves is due to friction. When the friction is broken in the wheel bearings the plane is free to move in the direction of any force applied to it.

[vnx205]

I'd like to pose a slightly different question: Could you launch a plane (engines not running, wheel brakes firmly applied) by using a perfectly flat and extremely long conveyor belt? :)

Do you want the short answer or the long answer?
The short answer is, "No". :)

Sent from my U8815 using AULRO mobile app

[BigJon]

I'd like to pose a slightly different question: Could you launch a plane (engines not running, wheel brakes firmly applied) by using a perfectly flat and extremely long conveyor belt? :)


Sure, but without the engine running it would be a pretty short flight.

[vnx205]

Sure, but without the engine running it would be a pretty short flight.

No!
It won't get off the ground at all.
As soon as it begins to get a little bit of lift, the wheels will begin to slip on the conveyor belt so the plane will stop picking up speed.
It will never get enough speed to lift off.

Sent from my U8815 using AULRO mobile app

[bee utey]

No!
It won't get off the ground at all.
As soon as it begins to get a little bit of lift, the wheels will begin to slip on the conveyor belt so the plane will stop picking up speed.
It will never get enough speed to lift off.
Precisely. The coefficient of friction multiplied by (the plane's weight due to gravity minus the lift generated) would be less than the aerodynamic drag and therefore no actual liftoff would take place. To exceed lift off speed a mechanical connection like a tow rope or sling shot is required.

However if the conveyor stopped at the edge of a cliff some flight might take place. :p

[Blknight.aus]

Precisely. The coefficient of friction multiplied by (the plane's weight due to gravity minus the lift generated) would be less than the aerodynamic drag and therefore no actual liftoff would take place. To exceed lift off speed a mechanical connection like a tow rope or sling shot is required.

However if the conveyor stopped at the edge of a cliff some flight might take place. :p

Id have though That would depend on the plane and the pilot.

once enough airspeed was generated to get the tail up enough elevator could be used to pitch the nose down and "fly" the aircraft downwards (areo drag would go up hugely but we get to ignore that in this case its an improbably/impossibly massive conveyor powered by a perpetual motion/energy hiclone) to maintain downwards pressure on the wheels.

you probably couldnt do it in a jumbo but one of those canadian short strip jobbies could probably pull it off

If you set no flaps youd also lower the lift and areo drag of the plane so you might also be able to get it up above full flaps take off speed with 0 flaps set, set full flaps and pull back.

IF it could be done it'd be a very short flight unless you had some very fast spool engines.

[BigBlackDog]

No!
It won't get off the ground at all.
As soon as it begins to get a little bit of lift, the wheels will begin to slip on the conveyor belt so the plane will stop picking up speed.
It will never get enough speed to lift off.

Sent from my U8815 using AULRO mobile app

Your assuming the plane lifts off at minimum flying speed though. If you waited until you were significantly above flying speed and then pulled back it would fly, inertia being what it is.

[BigJon]

I am with Blknight and BigBlackDog. I am pretty certain that you could get the conveyor belt fast enough while keeping the aircraft solidly on the deck to the "pop" it up in the air with some of the excess speed. Manipulating control surfaces as required, as you would never take off in any aircraft at stall speed.

[ramblingboy42]

I'd like to pose a slightly different question: Could you launch a plane (engines not running, wheel brakes firmly applied) by using a perfectly flat and extremely long conveyor belt? :)

Absolutely it will launch.

[Homestar]

Absolutely it will launch.

Wrong again, there's an explanation of why a few posts back. It will get to the point of creating lift, but never quite get off the ground as it will slip on the conveyor just as lift is achieved, then drop back again, and so on and so forth.

[ramblingboy42]

nope , in the first scenario it wont fly

in the second , it WILL launch.....no one has questioned how far...but it will.

[vnx205]

Several of us have pointed out that the treadmill has no measurable effect on the plane so it takes off normally.
Can you explain why you do not believe this?

[bee utey]

in the second , it WILL launch.....no one has questioned how far...but it will.
Only if the pilot can generate enough down force (as mentioned by others below) for belt-to-wheel friction to exceed aerodynamic drag to achieve a speed above lift off when he readjusts his flaps for takeoff. Otherwise the plane will just slip backwards on the belt without achieving liftoff. :)

[ramblingboy42]

I already have.

[vnx205]

I already have.


Are you are referring to post #4?
It does not address that issue at all.
That post shows that you have just accepted at face value the comment about the treadmill matching the speed of the plane.
The point is that it can't match the speed of the plane no matter how hard it tries.
You have assumed it will match the speed of the plane when in fact that is impossible.
All you have done is state the obvious point that the plane won't fly if it doesn't move.
Explain why it won't move.

[Ferret]

Consider a stationary plane with frictionless wheel bearings on a stationary conveyor.

If the plane's engine is not going and the plane's wheel bearing are frictionless then when the conveyor is started the planes wheels will spin but the plane will remain stationary.

It does not matter how fast the conveyor runs or which direction it runs, the plane will remain stationary because there is no force acting on the plane to move it. No force from the movement of the conveyor or the spin of the wheels can be transmitted through the frictionless wheel bearings to the plane. The wheels just spin as the conveyor moves.

Newton says - a body will remain at rest unless acted on by a force. There is no force from the conveyor acting on the plane.

Once the plane's engine is started the propeller generates a force. The plane now moves forward under the influence of that force. The direction of movement or speed of the conveyor is still having no influence over the plane because no force from the conveyor can be transmitted through the frictionless wheel bearing.

In the real world the wheel bearings are not frictionless but they are minimal friction so the the force transmitted to the plane caused by spinning wheels from the movement of the conveyor is also minimal. That minimal force is easily overcome by the thrust of the propeller allowing the plane to move forward almost as easily as if it was on stationary ground. So it will take off if the conveyor is long enough to approximate the length of a conventional runway.

Nothing about the movement of the conveyor has a great influence over the movement of the plane at any time. Provided the wheels spin freely then in practical terms it is not possible to drive the conveyor fast enough to impart a force through the spinning wheels on the plane that is equal but opposite to the force generated by the propeller and so bring it to a standstill preventing it from taking off.

[Milton477]

Not withstanding all of the above, it is money that makes a plane fly. That's what my flying instructor told me after I explained the high pressure low pressure thing over the wings. "Try not paying your instruction fees & see how far you fly" he told me.

[BigBlackDog]

Not withstanding all of the above, it is money that makes a plane fly. That's what my flying instructor told me after I explained the high pressure low pressure thing over the wings. "Try not paying your instruction fees & see how far you fly" he told me.

Truth right there.

Want to go faster, further, higher, heavier? That'll cost more:) it's an exponential curve too. Twice as fast = four times the money

[BigJon]

Not withstanding all of the above, it is money that makes a plane fly. That's what my flying instructor told me after I explained the high pressure low pressure thing over the wings. "Try not paying your instruction fees & see how far you fly" he told me.


And the propellor is a fan to keep the pilot cool. Want proof? See how much they start to sweat if it stops mid flight.

[Hugh Jars]

This is an hillarious thread.

Unless the aircraft has physical forward airspeed, yes - airspeed, it will not fly. The only exception is in a wind tunnel or a catapault launch. A model aeroplane really isn't a good example, as most of them have a huge power to weight ratio. When I say that, I mean the thrust of the propeller can just about lift the plane off purely on its own.

As others have alluded to, you would need a conveyor with the physical length of whatever runway is required. Doesn't matter whether it's running or not. The aircraft only recognises airspeed-not groundspeed.

I used to fly Dash-8's (Canadian STOL aeroplane). The quickest I got one airborne was in a headwind of about 45 knots (remember I said the aeroplane only recognises airspeed?) So when I lined up for takeoff, the airspeed indicator was reading 45knots. V1/rotate is around 95knots, so I only needed to accelerate another 60 knots. That took about 200m. In no wind, it would've been around 500m or so.

Had we been on a conveyor, it would still need to be 200m long in order to get sufficient AIRSPEED to fly. (And have a 45 kt wind blowing).

The B737 I fly now needs about 150kt to get airborne. Put it on a conveyor running at 150kt, and the aircraft will still need a 1200-1500m long conveyor to get up to 150kt airspeed. Problem is the tyres are only rated at around 200 mph, so theoretically you would need to run from the back to the front of the conveyor in order to get the 150kt forward airspeed, which would have the wheels turning at 300kt. Can't be done.

[vnx205]

200 metres isn't short by Canadian standards. :)

Have you seen these?

https://m.youtube.com/watch?v=gQJKW5vfvog&itct=CA4QpDAYASITCMiGiJmwk9ACFQeufgodvDkLgDIHcmVsY XRlZEjrvNDwu7jWjeYB&gl=AU&hl=en&client=mv-google

[vnx205]

I am having trouble working out if you are in the "fly" or "no fly" camp.

Your comment about airspeed puts you in the "fly" camp yet other coments suggest otherwise.

[superquag]

Truth right there.

Want to go faster, further, higher, heavier? That'll cost more:) it's an exponential curve too. Twice as fast = four times the money

Yes indeed.... but whilst 'money' keeps it in the air.... it's the paperwork that permits it to be in the air...

and 'paperwork' wrapped in Red Tape can get expen$ive too...:mad:

[Hugh Jars]

The long and the short of it is that if it doesn't have enough AIRSPEED to get airborne, it will not fly. Take conveyors and treadmills out of it. They have no effect.

[superquag]

Funny you should say that, - my Instructor had a fetish for me maintaining sufficient AIRspeed... made the occasional reference to 'staying alive' . . . ;)

[BigBlackDog]

Yes indeed.... but whilst 'money' keeps it in the air.... it's the paperwork that permits it to be in the air...

and 'paperwork' wrapped in Red Tape can get expen$ive too...:mad:

You don't have to convince me, most of my job revolves around paperwork, auditing it, creating it, trying to not let it take over the place:)

[harry]

hell, 6 pages of ****.
by the way,
Carpenters use planes!

bah humbug.

[vnx205]

hell, 6 pages of ****.I make it only one page of whatever it is that the swear filter dealt with. :)
I find it more convenient to set my preferences to show 30 posts per page, so I see only two pages. :)
Furthermore a significant number of posts were pointing out why the people who think the plane won't take off are wrong.
Surely those posts serve a useful purpose and don't fall into the category of whatever you described in terms that the swear filter modified. :)
So if roughly half the posts were useful, that leaves just one page that was humbug. :)

by the way,
Carpenters use planes!

bah humbug.
:) :)

[pop058]

hell, 6 pages of ****.
by the way,
Carpenters use planes!

bah humbug.

https://www.aulro.com/afvb/images/imported/2016/11/456.jpg

[ramblingboy42]

I am having trouble working out if you are in the "fly" or "no fly" camp.

Your comment about airspeed puts you in the "fly" camp yet other coments suggest otherwise.

his comments about airspeed puts him in the NO FLY camp.

NO AIRSPEED - NO FLY.... get it?

[vnx205]

his comments about airspeed puts him in the NO FLY camp.

NO AIRSPEED - NO FLY.... get it?

I see you are still under the delusion that the treadmill can prevent the plane getting airspeed. :)


The long and the short of it is that if it doesn't have enough AIRSPEED to get airborne, it will not fly. Take conveyors and treadmills out of it. They have no effect.

Did you miss Hugh Jar's comment about the effect the treadmill has? I think his recognition that the treadmill has no effect puts him firmly in the FLY camp. :)

[Homestar]

his comments about airspeed puts him in the NO FLY camp.

NO AIRSPEED - NO FLY.... get it?

Wrong - it puts him in the 'fly' camp. I didn't even know it was still up for discussion, it's been proven beyond any doubt.

[ramblingboy42]

no doubts about it...

there are facts though.....and laws....it won't fly.

[bee utey]

no doubts about it...

there are facts though.....and laws....it won't fly.

I think I get it now... the treadmill is covered with fly paper. :p

[Homestar]

no doubts about it...

there are facts though.....and laws....it won't fly.

I think yo need to go back to school and take year 10 Physics again. ;)

[vnx205]

no doubts about it...

there are facts though.....and laws....it won't fly.

I am beginning to suspect that you have realised by now that you are wrong and are just playing some sort of game.

Nevertheless, I am prepared to continue the game for a bit longer.

There must be some points on which we are prepared to agree, so it should save all of us some time if we can identify the issues on which we agree and where the areas of disagreement are.

If we ignore the points of agreement and focus on the disagreement, we may be able to bring this to a resolution more quickly.

If you could answer yes or no to each of the following, it should allow us to eliminate those things about which there is no disagreement. We can consider the reasons for your response later.


Do you accept that the wording of the original question was that the pilot attempts to take off and the treadmill operator attempts to match the speed of the plane?
Do you accept that for the sake of this debate, we should assume that the plane has been properly maintained and the pilot knows how to operate the plane?
Do you accept that the force that propels a plane forward is the thrust of the propeller or jet engine?
Do you accept that since the pilot is competent, attempting to take off will involve opening the throttle to get the engine up to the revs normally used for take-off?
Do you agree that a couple of men can easily push a light plane around on the ground and that a Land Rover Defender once demonstrated the effectiveness of the anti-stall feature by dragging a full size airliner?
Do you accept that the previous point demonstrates that the rolling resistance of the wheels on an aircraft is quite small compared to the thrust the aircraft engine can produce?
Do you accept that the only force allowing the treadmill to drag the plane backwards is the rolling resistance of the wheels?
Do you accept that the thrust produced by the plane propeller or jet is much greater than the drag created by the wheels?
Do you accept that if the above was not the case, then a plane would never be able to take off from level ground on a normal runway?
Do you accept that no matter how hard the treadmill operator tries to "match the speed of the plane", all that happens is that the plane's wheels spin a bit faster with no significant increase in the force dragging the plane back?


I look forward to your responses. :)

[Hugh Jars]

Without forward AIRspeed (airflow over the wing, sufficient to overcome the aeroplane's weight), the aeroplane won't fly. It's really a basic rule of aerodynamics.

The only place I'm aware of that an aeroplane could consistently fly with no forward GROUNDspeed is a wind tunnel :)

[austastar]

Hi,
Surely the hypothetical treadmill effect is the same as the practical effect of taking off downwind?

Take off air speed will need to be as normal, only achieved by overcoming the handicap of an induced tailwind plus the added resitance of wheel rotation speed needed along the backwards travelling treadmill.

Simiar to an amphibious aircraft taking off against a water current.

Cheers

Sent from my GT-N5110 using AULRO mobile app

[vnx205]

Without forward AIRspeed (airflow over the wing, sufficient to overcome the aeroplane's weight), the aeroplane won't fly. It's really a basic rule of aerodynamics.

The only place I'm aware of that an aeroplane could consistently fly with no forward GROUNDspeed is a wind tunnel :)

The point is that on a treadmill, the plane will have airspeed.

The treadmill has no noticeable effect.

The plane will fly.

Ground speed or treadmill speed is irrelevant.

The only thing that matters is airspeed and the plane will have that.

The plane will fly.

Why do people think the plane will not have airspeed?

[ramblingboy42]

Without forward AIRspeed (airflow over the wing, sufficient to overcome the aeroplane's weight), the aeroplane won't fly. It's really a basic rule of aerodynamics.

The only place I'm aware of that an aeroplane could consistently fly with no forward GROUNDspeed is a wind tunnel :)

g'day Hugh Jars, I was a private pilot and flew aeroplanes as you do , not planes or airplanes.

I was also an aircraft airframe fitter , trained in subsonic flight , supersonic flight and rotary wing.

you and I both know we are correct as well as any other pilots in here.

is it worthwhile bothering to continue this argument?

[vnx205]

g'day Hugh Jars, I was a private pilot and flew aeroplanes as you do , not planes or airplanes.

I was also an aircraft airframe fitter , trained in subsonic flight , supersonic flight and rotary wing.

you and I both know we are correct as well as any other pilots in here.

is it worthwhile bothering to continue this argument?

Please answer my questions.

You have never addressed any of the specific facts I have pointed out. You have just made general statements about the need for airspeed. I have explained why the plane WILL have airspeed. You have not explained WHY it won't.

I would like to know the particular point on which you disagree with me.

[ramblingboy42]

read back...

[strangy]

My goodness this thread is excruciating.

Its in the way an individual interprets a deliberately ambiguous hypothetical question.

The question is posed in AULRO and initially on the link in such a way as to highlight the way people think irrespective of the physics.
i.e some will think of a treadmill operating one direction while others consider in the opposite direction.

However, the key to the apparent question was answered many times and remains a law of aerodynamics.
No airspeed = no lift = no flight.

The concept may be better understood by considering an aircraft carrier.
Assume we are not bound by design limitations.
Sail along at 100kts which will provide a relative airflow of 100kts, with an aeroplane that flies at 100 kts or less and you have flight, though relative to the deck only the aircraft is stationary.

Now reverse this, the aircraft now has to provide the same nominal amount of thrust (and have an inconceivable deck length) to achieve a relative airflow of 0, which means no flight.however the inconceivably large deck is moving underneath the aircraft at 100kts.

, like some others i make my living maintaining aerofoils in suitable airflow.

[vnx205]

read back...
I have done that several times even though I am beginning to suspect that you have not actually read mine or anyone else's.

Lets's take your posts one at a time to see where you went wrong.

Your first post said:

I may be late into this but the aeroplane (not airplane) clearly wont fly in that situation.

It will remain completely stationary unless more engine power is applied or the speed of the conveyor changes.

If the speed of the conveyor matches the input of the aeroplane there will be zero airspeed.

The groundspeed will be high but no lift is being produced by the wings.....see.....the aeroplane is not moving through the air , only rolling on the conveyor using it's engine power to to keep up to the conveyor operator's input......or conversely the conveyor operator is keeping abreast of the pilot's input.

No argument. It won't fly.

There it is! Your very first post shows why you keep repeating your error.

The conveyor simply cannot prevent the plane from gaining speed.

I will repeat that since it is the most important point that you seem to have missed.

The conveyor cannot prevent the plane from gaining speed.

I have explained several times and others have explained several times why the conveyor or treadmill cannot prevent the plane from moving forward.

You appear to be assuming that the treadmill can prevent the plane from moving forward.

It can't!

Please explain why you think it can prevent the plane moving forward.

Perhaps you did not read the original question carefully.

It does not say that the treadmill drags the plane back so that it doesn't move forward. It says that the treadmill attempts to match the speed of the plane.

The treadmill can attempt that all it likes, but it will fail.

The plane will move forward, gain airspeed and take off.

In view of the effort that I and others have put into trying to help you understand, it would be nice if you could put some effort into explaining exactly where you believe our thinking is incorrect. Just repeating that a plane needs airspeed to take off is not a useful comment. Everyone knows that.

[vnx205]

My goodness this thread is excruciating.

Its in the way an individual interprets a deliberately ambiguous hypothetical question.


I'm assuming that people will read your post, so I won't quote all of it.

The question is not ambiguous. The question is not badly worded. It is not open to interpretation. The comparison with an aircraft carrier is quite unnecessary.

The question deliberately says that the pilot attempts to take off. It then says that the treadmill operator attempts to match the speed of the plane.

People who don't read the question carefully or are concentrating purely on the laws of aerodynamics will fail to grasp the fact that the treadmill can attempt all it likes, but will have no effect on the plane.

It is interesting that pilots on this forum seem to be the ones who have made the mistake that the question is deliberately and cleverly designed to encourage people to make.

It seems that pilots think only about what a plane needs to fly and are completely oblivious to the fact that the treadmill will have no effect.

The plane will fly!

[strangy]

Yep dumb ass pilots. what would they know right?
After all their understanding of phraseology and aerodynamics and application,, pfft.
I mean really who are they kidding
as I said excruciating.

[vnx205]

If you are so sure that you are right and the rest of us are wrong, why have you never addressed the specific facts that we have presented?

Don't just tell us we are wrong.

Explain WHY we are wrong.

[67hardtop]

See my post at the beginning.

I asked a qualified pilot this question on sunday night. He is currently employed as a pilot. He said unequivically that the plane wont fly. "Its impossible for it to move", he said. I could have made another $100.00 of him but i didn't. Seems everyone thinks the propellor is connected to the wheels...

Cheers Rod

Sent from my GT-I9507 using AULRO mobile app

[vnx205]

Rod, that adds weight to my claim that pilots are probably more likely to get the answer wrong than other people.
:)

[vnx205]

I and several others are making a genuine attempt to help the pilots understand why they are wrong.

They are wrong because they are thinking too much about aerodynamics.

In an attempt to show where they are making their mistake, I offer the following analogy. Like most analogies, it isn't perfect, but might start people thinking in the right direction.

Remember that old joke that went something like this:
A plane from Queensland on its way to Victoria crashes in NSW. In which state would the survivors be buried?

Someone with a legal or aviation background might consider the legalities, federal v state laws, the ethical issues, and such things, but someone who reads the question carefully will realise that you don't bury the survivors.

This question is not about whether a plane can fly if it is held stationary.

The point is that it won't be held stationary.

[vnx205]

https://www.aulro.com/afvb/images/imported/2016/11/351.jpg
:):)

[ramblingboy42]

See my post at the beginning.

I asked a qualified pilot this question on sunday night. He is currently employed as a pilot. He said unequivically that the plane wont fly. "Its impossible for it to move", he said. I could have made another $100.00 of him but i didn't. Seems everyone thinks the propellor is connected to the wheels...

Cheers Rod

Sent from my GT-I9507 using AULRO mobile app

... the pilot is unequivocally correct...again

[vnx205]

I see that you are still confining yourself to assertions with no explanation .

[67hardtop]

Has anyone watched the mythbusters experiment and subsequent explanation of why it will take off??

Cheers Rod

Sent from my GT-I9507 using AULRO mobile app

[vnx205]

Has anyone watched the mythbusters experiment and subsequent explanation of why it will take off??

Cheers Rod

Sent from my GT-I9507 using AULRO mobile app

Yes. I watched it.

I also read some of the responses on a couple of forums from people who think that Mythbusters got it wrong. They are all making the same mistake as the airframe fitters and pilots on this forum.

They all fail to realise that the treadmill can't stop the plane moving forward.

[Blknight.aus]

Im gunna go get some popcorn, this threads as much fun to watch as some of the ones about getting a 2:1 off of a single snatch block.

The planes going to fly, anyone on here who is a licensed pilot, or knows a licensed pilot that says otherwise in order of my preference

1. hand in your ticket.
2. at least let me know when and where you'll be in the air so I can go be somewhere safer
3. identify yourself to me before I get into a plane you'll be flying so I can get right back out again.

[cuppabillytea]

I can't imagine a plane which doesn't have enough thrust to counter the rolling resistance of it's wheels, so I'm in the she will fly camp.

[Tombie]

Unless it is a really small treadmill..
Then the plane will crash into the controls and stop...

Or it will go slow and fall of the back - activating the emergency stop lanyard...

At which time the crash site may be covered in Flies...

[cuppabillytea]

Unless it is a really small treadmill..
Then the plane will crash into the controls and stop...

Or it will go slow and fall of the back - activating the emergency stop lanyard...

At which time the crash site may be covered in Flies...

That happens to me every time I get on one.

[Tombie]

... the pilot is unequivocally correct...again



No he's NOT. And the quote has the answer...

Think of it like this:

Skateboard on a treadmill..
Support skateboard (hold in place)
Turn on treadmill...
Skateboard stays in place but the wheels rotate being driven by the treadmill. Let's say at 10km/h

Can the skateboard move forwards? Of course it can - just push it forwards using your hand that was holding it in place. Just like a Jet/Prop can push/pull the aeroplane forwards (increasing its SPEED through the AIR).

The side effect, the wheels underneath the skateboard are now rotating at the speed of the treadmill + the speed of the board moving forwards..

So the aeroplane can gain speed regardless - which, assuming a long enough conveyor - will allow the aeroplane to gain sufficient AIRSPEED across the wings to induce lift and eventually flight.

So IF the Aeroplane requires 100knots to lift off, and the head wind is 25knots, and IF the aeroplane accelerates to 75 knots SOG it will take flight.... (because AIRSPEED is now 100 knots)

And all this time - assuming the conveyor operator is running his belt at 75 knots the opposite direction (matching the aeroplanes speed on ground) the wheels on the aeroplane will be rotating the opposite direction to the aeroplanes direction of travel at a rotational equivalent of 150knots when it lifts off....

Not rocket science......

[squizzyhunter]

Good analogy Tombie, I was thinking skate board with a sail on it like a windsurfer.
At uni they always try to teach critical thinking and it takes a while for them to pick it up. This thread should be part of the critical thinking syllabus = don't believe what people state as fact even if they are experts in the field.

[pop058]

Good analogy Tombie, I was thinking skate board with a sail on it like a windsurfer.
At uni they always try to teach critical thinking and it takes a while for them to pick it up. This thread should be part of the critical thinking syllabus = don't believe what people state as fact even if they are experts in the field.

Firstly, this is a serious question. Would someone who is trained and operates a piece of equipment (bobcat, scissor lift, aeroplane, whatever) be considered an expert on it?. I appreciate that a pilot may have a greater theoretical understanding of how his chosen piece of hardware works as opposed to a grader operator ( for example), but does that make them a qualified expert?

Flame suit on just incase :D

[squizzyhunter]

Firstly, this is a serious question. Would someone who is trained and operates a piece of equipment (bobcat, scissor lift, aeroplane, whatever) be considered an expert on it?. I appreciate that a pilot may have a greater theoretical understanding of how his chosen piece of hardware works as opposed to a grader operator ( for example), but does that make them a qualified expert?

Flame suit on just incase :D

I agree on perhaps not being true "experts" in physics but when it comes to theory of flight I would like to kid myself that they are. I have only got a few hours up my sleeve but was impressed by the theory content.

[Ferret]

They all fail to realise that the treadmill can't stop the plane moving forward.

UNSW school of physics response. To stop the plane moving forward need one or more of:

a) conveyor running at supersonic speeds.
b) pilot applying wheel breaks.
c) pilot not revving engine creating less than normal thrust.
d) a conveyor so huge and fast it moves the surrounding atmosphere with it.

Of course it all been covered before and I know from previous experience it's pointless but anyhow...

UNSW School of Physics:- The plane on the conveyor belt (http://www.animations.physics.unsw.edu.au/jw/plane-conveyor.htm)

[vnx205]

I think some of the responses from the people on here with aeronautical qualifications suggests that they might be quite knowledgeable about things that are covered in their training and things that they have experienced.

However, when it comes to something they were not taught or have not discovered through experience, they are not necessarily more expert than the rest of us.

Flight training doesn't cover planes on treadmills, so our resident aeronautical experts are obviously quite out of their depth on that subject.

At the moment, I think they are the only ones who are still answering the question incorrectly.

[Tombie]

The treadmill is like a politician - it's all smoke and mirrors...

Ask a Pilot how they make a aircraft take off - they will answer correctly every time..

The only time any link to the landing gear has impact on taking flight is on the deck of an Aircraft carrier (the catapult)

[vnx205]

I have a theory about why so many pilots get this wrong. I'm starting with the assumption that they are generally intelligent people (although some can be particularly stubborn). :)

As soon as they hear a question about aircraft, their mind goes straight to their understanding of aerodynamics. That is hardly surprising since that is a subject they know about and a place where they feel comfortable.

Because they focus on aerodynamics, they assume the question says that the plane tries to take off and the spinning treadmill holds it stationary. Their answers are then based on that mistake.

If they thought a little more about treadmills and a little less about aeroplanes, they would realise that the question couldn't possibly say that because it would be a physical impossibility. The treadmill has no effect.

The question is correctly and carefully worded. The pilot tries to take off and the treadmill operator tries (and fails) to hold the plane stationary.

The pilots aren't answering the question that was asked, they are answering a different meaningless question.

It is because they know about planes that they leap to the wrong conclusion.

Since it is quite understandable that they would see the question as something about planes, it is appropriate that we have all been more tolerant in dealing with their recalcitrance than we might have been for less aeronautically qualified people. :)

[strangy]

Well Though Ive found this thread excruciating I can also admit being incorrect.
All of us are at one time or another.

So why do Pilots seem to have the most difficulty with this?

Heres why.

Firstly lift (and this not the universally correct terminology for all aerofoils however in the case of this fixed wing aeroplane will do) only comes from airflow which is one of the facts mentioned by myself and others.
So all pilots are looking for airflow to create lift which requires a fwd speed.
Obviously this is generated by whatever motive system is fitted.
Any perception of an action contrary to this instinctively leads to negative answer.
Particularly where in any case thrust is required for the aircraft to remain stationary relative to position on the conveyer.

Next. All manner of ground inhibits the generation of that fwd speed and therefore lift.
Ill stay on takeoff and ignore landing.
The takeoff run required for a given day i.e wind-temp-weight-altitude and surface, varies considerably and on a marginal rwy, is the difference between a happy day and turning the multimillion $ ship into ball with you in it.

The above is what I had to subconsciously hurdle.
Pilots dont theorise about landing surfaces such as the one posed. We work with data and factual numbers generated by actual operation on the surfaces encountered augmented by lessons learnt from failures and success over the history of aviation.
Which results in typically systematic, procedurally driven process coupled with a dextrous skillset.

Considering surface for takeoff capability.
eg. A long grass rwy can provide enough friction to prevent gaining enough airspeed for takeoff.
A tailwind increases the distance for take off (and landing) as more length of rwy is required to overcome the tailwind and generate fwd airspeed.
The practical use of these facts on daily basis causes an instinctive view that any surface which appears counter intuitive to the desired outcome as preventing or inhibiting takeoff.

Wheels: They are not frictionless marvels and breakaway thrust is needed to get a machine moving from standing.
Therfore if on a conveyer the aircraft is going backwards unless thrust is applied to breakaway from the initial wheel contact patch to get it rolling.
Because we all work with a calculated actual numerical distance required for takeoff run subconsciously we again discount the hypothetical.
Now subconsciously these and other experienced and mandatory initial factors are building a "no" position.
Add to this that all the above are always finite quantities which if disregarded end badly for any flight.
However
need to be disregarded in the hypothetical question eg. the absurdity of the conveyer in the first instance.
Now..
It is because of the above (very simply stated) factors to be considered for take off that some of us have put practical application and dismissal of hypothetical absurdity rather than pursue the final outcome.

If you were able to place any pilot who thought the plane woulndt fly, onto said conveyer, the initial response when the airspeed increased would be that the conveyer wasnt able to keep up with the plane. I reckon most would get it as soon as the thing left the ground.

So, this may help it may not. I certainly dont feel silly.
In fact Im going to use this thread as an example in Human Factors refresher courses to highlight how we can be conditioned to exclude or accept information based on our exposure to highly specific and demanding roles.

[Ferret]

If you were able to place any pilot who thought the plane woulndt fly, onto said conveyer, the initial response when the airspeed increased would be that the conveyer wasnt able to keep up with the plane. I reckon most would get it as soon as the thing left the ground.

The pilot in the mythbusters video was equally surprised when he took off. The question being tested by mythbusters was, I think, worded slightly differently to the one originally posed here though the mythbuster video nonetheless demonstrates the basics of it.

https://www.youtube.com/watch?v=0ul_5DtMLhc

[cuppabillytea]

Ah yes. In the OP Vlad (whom I suspect is a great red herring tosser) poses the question and shares a link. In the link a blogger named Chris gives us said question and some variants, then he predicts exactly what will happen on any forum it's posted on and carries on to tell us why the aircraft will take off.
He got it right, or should I say wright?

[BigBlackDog]

What if, instead of an aeroplane on the treadmill, there was a.....


















HELICOPTER:twisted:

[cuppabillytea]

:lol2::vampire:

[BigJon]

What if, instead of an aeroplane on the treadmill, there was a.....


















HELICOPTER:twisted:

Everyone knows that helicopters don't fly.



They are just so ugly that the Earth repels them! :D

[ramblingboy42]

What if, instead of an aeroplane on the treadmill, there was a.....

















HELICOPTER:twisted:

it will fly.....

[BigJon]

it will fly.....

Just like the aeroplane. Which has been proven.

[ramblingboy42]

errrrr.....it hasn't you know

[superquag]

The pilot in the mythbusters video was equally surprised when he took off. The question being tested by mythbusters was, I think, worded slightly differently to the one originally posed here though the mythbuster video nonetheless demonstrates the basics of it.

https://www.youtube.com/watch?v=0ul_5DtMLhc


... Forgive me if this has been covered (been 'by-passed't this past 10 days) but fly or not, it is all about the relative AIRspeed...over the wings. With the pilot accelerating .... and we notice the ASI increasing... regardless of the wheels spinning a lot faster than normal and the ground moving under him.... the airplane must obey its Laws of Flight and eventuallty respond to sufficient airspeed.
And fly.
We can illustrate this with a downwind landing... you are flying at just above stall speed-inside the lump of air - which lump is travelling down the runway in the same direction. - And boy, is the world going past you at a blurring rate of knots. !!!

If engine and air-surfaces are intelligently manipulated by a skilled pilot, the previously parked aircraft 'should' leave the ground and assume a suitable nose up attitude and climb out....whilst moving backwards from its original parking point. - Which is what toy kite will do, the string holding it in place to allow the wind to lift it. In this case, the engine can be called the 'string'.

Antonov An-2 | Australia (http://www.warbirdsonline.com.au/2014/01/22/antonov-an-2-australias-colt/)

But agree, a great inclusion into Human Factors... :twisted::twisted::eek::twisted::twisted:

[BigJon]

errrrr.....it hasn't you know

I am guessing you are either trolling (as suggested previously) or haven't watched the videos that show that it works.

[Ferret]

:D
...regardless of the wheels spinning a lot faster than normal and the ground moving under him.... the airplane must obey its Laws of Flight and eventuallty respond to sufficient airspeed.

And fly.

I think only one person is disagreeing with you ...and it's not me.

[ramblingboy42]

I have also watched model aeroplanes just hanging vertically on their propellor.

That doesn't prove that a GA aeroplane can do it.

[vnx205]

Have you read any of the posts that explain why the plane will fly?

Have you read any of the linked articles such as the one in post #92 that explain why the plane will fly?

Do you have any intention of addressing the specific points that anyone has presented that clearly show that the plane will fly?

Have you read the questions in post #64? Do you have any intention of answering them? It might help us to understand why you are persisting with your opinion.

Simply repeating that the plane won't take off does not constitute an explanation.

[Homestar]

That's because we all know now he's just trolling and having a lend of us all. Those who are continuing to explain are just feeding him...

DON'T FEED THE TROLLS!

[squizzyhunter]

This thread has been quite an eye opener. Next time I get in a prop plane I'm asking the pilot this question.