Will it Fly?

[Jotaru]

First off, I did a search, looked through a few pages, and feel I'm pretty up-to-date on the forum rules here, somewhat regular poster and very avid reader, so if this breaks any rules, plz warn before banstick ^^;; Anyhow... Somewhat of a copypasta from what I posted on my LS's site, just kinda a theoretical question because I know some people like to sit and ponder relatively impossible situations (myself included) and its a bit of fun brainwork if you're bored.

Edit: No, I did not design / think of / create this, yes it is on other forums, yes I did steal the idea, yes I do like to discuss it with people I don't take credit.

A jet plane is sitting on a runway, ready to take off. However, the runway is more like a giant treadmill, and has a system in place to constantly monitor the exact speed of the airplane on it. As the plane powers up the jet engines and moves forward, the treadmill moves rearward, in the opposite direction the plane is moving, at the same speed.

http://www.upgradetravelbetter.com/w...-treadmill.jpg

So, assuming there is no error in the control system for the treadmill (i.e. no cheap 'lawl the system is wrong' answers) and constantly matches the speed of the aircraft, but in the opposite direction, will the aircraft take flight?

Discuss And again, sorry if this is kinda not wanted in this section, can move/delete or whatnot, just kinda wanted to view more opinions on this. Banstix do not want ; ; ... GO!

Edit: Italicized where I edited, to clarify.

[Tristam]

No it won't, planes require air to be moving aganist the wings/body to take flight (a big reason it has wings), if the plane was rolling on a treadmill and the treadmill maintained the exact opposite speed of the wheels, the plane wouldn't be moving relative to the air around it.

[Necronus]

No.

A plane needs air flow to remain aloft. This plane will be motionless. If the "treadmill" is going backwards at the same speed of the plane, only the planes tires and the "treadmill" have any true speed, the plane will have a speed of 0

[Aodh]

No, flight is possible due to wind passing over the wings, if the plane is in a static location then there cannot fly. The wings are shaped so that the air passing over the top has a further distance to travel, and this creates a low pressure pocket over the wing. The air under the wing is relatively high pressure compared to above the wing, and therefore tries to equalize the pressure by moving up, creating lift.

http://www.ueet.nasa.gov/StudentSite...ingairflow.gif

[Skyylya]

Please go back to whereever you found this and tell the people that think it can fly that they are idiots and should spend 45 minutes each day banging their head into a wall.

As previous posters have said, what gives a plane it's lift is the air passage past the wings properly angled provided by the thrust of the engine, not the turning of its' wheels....

[Priran]

The jet engines create thrust but there's no lift, so no, it doesn't take off.

[Jotaru]

Ugh, don't be so harsh. If it was really so simple as 'lol it dun mewv' it wouldn't be on aviation forums.

[Isiolia]

Maybe if you had a really, really big fan...

Nah, like people said, you need (significant) airflow over the wings to create lift.

[Skyylya]

Ugh, don't be so harsh. If it was really so simple as 'lol it dun mewv' it wouldn't be on aviation forums.

But, it is that simple...please tell me this isn't a reflection on the intelligence level of modern pilots.

There are two possible way's to get lift out of something. Both are based on engine thrust and direction of movement. Things like planes operate on creating thrust for forward mobility, which would do nothing except push a plane accross the ground if it's wings weren't designed to push the air below the wings and lift the plane. Without that wind passage, there is no lift the plane would just skim accross the ground.

The other is vertical thrust i.e. rockets and such that are designed for the thrust to push them straight up, not requiring large scale wings but they do have stability wings but are mostly thrust/weight management to keep them angled vertically.


The treadmill Idea is foolish because the treadmill would essentially remove all airflow on the wings of the craft, so no amount of thrust is going lift the plane. If you were running the plane on the treadmill, then stopped the tracks and allowed the plane to move forward, then yes it would fly.

[Jotaru]

Do people really believe that the wheels spinning at double speed due to its inherent groundspeed from previous acceleration and the matched opposite speed of the treadmill will offset the enormous thrust?

[Influx]

Can a plane land on a treadmill as well?

[Venture]

No, but will it blend?

[Neosutra]

Ugh, don't be so harsh. If it was really so simple as 'lol it dun mewv' it wouldn't be on aviation forums.

So some random Joe posting on an aviation forum is the epitome of intellectual prowess? Seriously, it is that simple, its basic aerodynamis theory, im suprised the guy that posted on the other forum didnt get owned already.

[Skyylya]

Do people really believe that the wheels spinning at double speed due to its inherent groundspeed from previous acceleration and the matched opposite speed of the treadmill will offset the enormous thrust?

I've read this like 5 times and I don't get what you're trying to say.

[Alleya]

Do people really believe that the wheels spinning at double speed due to its inherent groundspeed from previous acceleration and the matched opposite speed of the treadmill will offset the enormous thrust?

I've read this like 5 times and I don't get what you're trying to say.

He seems to be arguing that the plane is already moving when it hits the treadmill and will somehow overcome equal contrary force in order to take off. That sound you hear is Newton spinning in his grave.

This is almost as dumb as the "a truck full of birds becomes magically lighter when all the birds fly at once" crap.

[Venture]

This is almost as dumb as the "a truck full of birds becomes magically lighter when all the birds fly at once" crap.

Mythbusters did a good job in busting this one.

[Septimus]

At least the picture is funny.

[ozz]

Do people really believe that the wheels spinning at double speed due to its inherent groundspeed from previous acceleration and the matched opposite speed of the treadmill will offset the enormous thrust?

I've read this like 5 times and I don't get what you're trying to say.

He seems to be arguing that the plane is already moving when it hits the treadmill and will somehow overcome equal contrary force in order to take off. That sound you hear is Newton spinning in his grave.

This is almost as dumb as the "a truck full of birds becomes magically lighter when all the birds fly at once" crap.

no,he's trying to say at the wheels,spinning at 300mph due the plane pushing them forward at 150mph and the treadmill pushing them backwards at 150mph wouldnt be able to hold the plane in place...a treadmill doesnt apply much force against an object with wheels though,it just spins them faster. the speed the airplane thinks it's going is measured by a windspeed indicator somewhere on the wing or fuselage,so if the airplane thinks it's traveling at it's v1 then it really is

the plane would take off,if the treadmill's speed is anywhere near the aircraft's speed,it wouldnt provide near enough force to hold it motionless

[divisortheory]

Do people really believe that the wheels spinning at double speed due to its inherent groundspeed from previous acceleration and the matched opposite speed of the treadmill will offset the enormous thrust?

I've read this like 5 times and I don't get what you're trying to say.

He seems to be arguing that the plane is already moving when it hits the treadmill and will somehow overcome equal contrary force in order to take off. That sound you hear is Newton spinning in his grave.

This is almost as dumb as the "a truck full of birds becomes magically lighter when all the birds fly at once" crap.

no,he's trying to say at the wheels,spinning at 300mph due the plane pushing them forward at 150mph and the treadmill pushing them backwards at 150mph wouldnt be able to hold the plane in place...a treadmill doesnt apply much force against an object with wheels though,it just spins them faster. the speed the airplane thinks it's going is measured by a windspeed indicator somewhere on the wing or fuselage,so if the airplane thinks it's traveling at it's v1 then it really is

the plane would take off,if the treadmill's speed is anywhere near the aircraft's speed,it wouldnt provide near enough force to hold it motionless

I always sucked ass at physics, but I do remember that Force = Mass * Acceleration. Surely the weight of a plane is far greater than the weight of a treadmill, as such if the treadmill is designed to produce exactly the same countervelocity as the plane at all points in time, it means the acceleration is exactly the same. Since Accelerattion is the same, you can conclude that the Plane has more force going forward than the treadmill has force going backward.

As such, the plane should continue to move forward, debunking the idea that the plane is motionless.

[Jotaru]

The general idea is that most people confuse aircraft mechanics with car mechanics.

Were this a car on a treadmill, I could completely see how it would not move. The faster the tires spun, the faster the treadmill would spin, and it'd be like running on a log in the water, you'd get nowhere. If it were a car with wings, I would agree.

However, the way I view it (and the general viewpoint that I've been following) is that the forward force is applied by the engines to the air (In an equal-but-opposite reaction, it pushes back, air being pushed back pushes plane forward), not the wheels. It seems relatively ludicrous to say that if you park an airplane on a treadmill and open up the throttle, it will not budge an inch just because its on a treadmill. As the plane were to accelerate (it would need to, for the treadmill speed to accelerate, and that thrust from the engines isn't just going to magically make the wheels spin with no connection in itself) the treadmill would accelerate as well... however, the power isn't being supplied through the wheels, so the fact that they are free-spinning is of no consequence. If the plane is going 20mph relative to the air, the treadmill will be going 20mph in reverse, the wheels will be spinning at an equivalent of 40mph, but the engines are happily pushing the jet along, because the only force to hold it back is wheel friction, which is, unless you decide to build a plane with no bearings, minimal. The treadmill would spin faster and faster, but as the wheels are free to spin, they would do just that, and wouldn't actually keep the aircraft in place.

Anyhow, that's how I view it, I wanted to leave my viewpoint out because 1) I don't much want to just be called a moron by people and 2) generally wanted to see how the thread developed, but if you look at this objectively (instead of IM RITE UR RONG) you can see why it is not as simple as 'can an aircraft fly without air flow over the wings', because excepting VTOL technology, they cannot. For the record, I do not argue that a conventional aircraft can fly without airflow over the wings