Airplane on Conveyor Belt Mythbusters 12/12

[jestal]

Ever stick your arm out the car window and twist your hand and feel it move up and down due to the force of the air against it...??

Perfect example of "flying". Surface area and air speed. That is what you need and all you need.

Put your car on a chassis dyno or tread mill and spin the tires up to 70. Stick your arm out the window and twist your hand and see if it "flys". Not.

Any one that thinks the airplane will fly on the treadmill needs to get some common sense.........LOL.

Unless you put some huge flaps on the tread mill (to suck air along with it) or blow air over the tread mill at the same speed as the tread mill there isn't a chance in hell the airplane will fly.

Wings "generate lift" yes but surface area and angle of attack in the presence of moving air will "fly" without a cambered wing. A sheet of plywood will "fly" if you get it moving. For all the explainations of how a wing works (I know...Iknow.....high pressure below/low pressure above due to the camber of the wing) try to explain how the plane keeps flying when it is upside downwards..... Angle of attack and airspeed.

JimLor ...... Now that I've commented on an "other discussion" or "NEPRT" thread it is sure to be closed and I'm sure to be warned....

 

[Rondo777]

SouthernCruizer, like Xviper and Rondo, are dead on when it comes to the principal of flight. We all agree on that. No airflow means no flight. They just can't get passed the fact that the thrust is independent of the contact with the treadmill and they somehow think the treadmill will act as some kind of brake holding the plane in place.
Go look at the skateboard post above. There is no ability for the treadmill to negate the forward movement.

I wouldn't have a problem flying with any of them. I'd have a problem while the plane is on the ground!

Ponyfool,

I'm assuming that this is a powered treadmill moving in the oposite direction of the intended flight. I fully get that there is no power driving the wheels of the plane. But unluss this is a magical weightless plane it is going to exert a force on the treadmill and the wheels are not going to spin, the plane will move backwards on the treadmill. You will need to apply thrust to overcome the motion of the tradmill just to stay still. If the treadmills speed is increased to match that of the thrust from the airplane then the plane will never move forward and never atain any airspeed. The full weight of the plane will be on the treadmill and you wont be flying.

If its not a powered treadmill just freewheeling then I absolutly agree that the plane will just roll down the tread and fly. I dont think there is so much a difference in opinion over the physics of flight as there is the perception of the type treadmill being used. Honestly, I dont know but was assuming the powered type treadmill.

PS, you'd be welcome to fly with me anytime, I promise to taxi safely!

 

[germany]

What is the airspeed velocity of an unladen swallow?

 

[SouthernCruizer]

Check out this treadmill.....and notice that the dude is tethered to a frame so that he wont' "fly" away from the surface of the treadmill like our amazing magical no airspeed airplane!! LOLOL



Jay

'04 FJR 1300

 

[Scythian]

If the treadmills speed is increased to match that of the thrust from the airplane then the plane will never move forward and never atain any airspeed. The full weight of the plane will be on the treadmill and you wont be flying.

Threre's yer problem right there: How does treadmill speed exert a force to counteract the thrust of the airplane?

Force = Mass x Acceleration

The treadmill cannot impart an acceleration to the aircraft body through the wheels 'cuz airplane wheels turn. So 'A' = 0.

So there can be no Force opposing the thrust of the aircraft so if the treadmill is long enouge, the airplane zooms into the sky with the wheels spinning madly

No matter how fast the treadmill turns, it can't impart a force to the aircraft because the only interface between the aircraft and the treadmill is the aircraft wheels and they freely spin.

The Mass (weight here on earth) of the airplane doesn't matter, it is orthogonal to the direction of motion of the treadmill.

It's a trick, the treadmill cannot ever oppose the thrust....

 

[twowheelnut]

What is the airspeed velocity of an unladen swallow?

Wot you mean? African or European?

 

[Scythian]

Check out this treadmill.....and notice that the dude is tethered to a frame so that he wont' "fly" away from the surface of the treadmill like our amazing magical no airspeed airplane!! LOLOL

HAHAHAHA! That's, unlike an airplane, 'cuz he uses the action of his feet to propel himself and an airplane uses its thrust, not its wheels to propel it!The treadmill can exert a counteractive force to his feet, it cannot exert a counteractive force to the thrust of the airplane.If that guy had a propeller on his back he wouldn't need a tether!

 

[germany]

What is the airspeed velocity of an unladen swallow?

Wot you mean? African or European?

I don't know that. AAAAAAAIIIIIIIEEEEEE!!!!!!!!!

 

[SouthernCruizer]

If the treadmills speed is increased to match that of the thrust from the airplane then the plane will never move forward and never atain any airspeed. The full weight of the plane will be on the treadmill and you wont be flying.

Threre's yer problem right there: How does treadmill speed exert a force to counteract the thrust of the airplane?Force = Mass x AccelerationThe treadmill cannot impart an acceleration to the aircraft body through the wheels 'cuz airplane wheels turn. So 'A' = 0.So there can be no Force opposing the thrust of the aircraft so if the treadmill is long enouge, the airplane zooms into the sky with the wheels spinning madlyNo matter how fast the treadmill turns, it can't impart a force to the aircraft because the only interface between the aircraft and the treadmill is the aircraft wheels and they freely spin.The Mass (weight here on earth) of the airplane doesn't matter, it is orthogonal to the direction of motion of the treadmill.It's a trick, the treadmill cannot ever oppose the thrust....

*******************Dude, you have a SERIOUS problem comprehending, or, you are just yannking some chains to get a reaction...I'll just say this, and leave it at that...the ONLY way an airplane that is sitting on a runway can take off is to start a TAKE OFF ROLL....the plane HAS to have foward speed in order to attain AIR SPEED...now here on this planet, we have to assume that the airplane has WEIGHT, and this WEIGHT is sitting atop of wheels....the WHEELS are on the surface of the TREADMILL, which can match the speed of the rotating WHEELS of the airplane, and NO MATTER what kind of prop is pushing or pulling the aircraft, the aircraft CANNOT move forward without its wheels turning...unless you have some ******* magical way to suspend the airplane mere centimeters above the surface...so just because the damn prop is pushing or pulling against AIR , that dont mean squat. The forward motion HAS to transfer to the wheels, which will be negated by the counter moving treadmill. Have you EVER seen an airplane take off from ANYWHERE without its wheels turning first???? You use lots of buzzwords like thrust and mass and orhtogonal to make an impressive story, but its nonsensical!! Use your God given logic and think about it!As for the ridiculous post earlier about some stupid experiment with a helicopter...geeze! A helicopter and a plane are 2 completely different animals...a plane has a fixed wing and relys on forward motion of the fuselage that it's attached to in order to generate lift...whereas a helipcopter has a ROTATING WING that is powered to produce its own air speed. It can take off vertically and doesn't rely on its wheels having to turn at all.Peace out! Jay'04 FJR 1300

Check out this treadmill.....and notice that the dude is tethered to a frame so that he wont' "fly" away from the surface of the treadmill like our amazing magical no airspeed airplane!! LOLOL

******************* :blink: [SIZE=36pt] MORON[/SIZE]

 

[Scythian]

If the treadmills speed is increased to match that of the thrust from the airplane then the plane will never move forward and never atain any airspeed. The full weight of the plane will be on the treadmill and you wont be flying.

Threre's yer problem right there: How does treadmill speed exert a force to counteract the thrust of the airplane?Force = Mass x AccelerationThe treadmill cannot impart an acceleration to the aircraft body through the wheels 'cuz airplane wheels turn. So 'A' = 0.So there can be no Force opposing the thrust of the aircraft so if the treadmill is long enouge, the airplane zooms into the sky with the wheels spinning madlyNo matter how fast the treadmill turns, it can't impart a force to the aircraft because the only interface between the aircraft and the treadmill is the aircraft wheels and they freely spin.The Mass (weight here on earth) of the airplane doesn't matter, it is orthogonal to the direction of motion of the treadmill.It's a trick, the treadmill cannot ever oppose the thrust....

*******************Dude, you have a SERIOUS problem comprehending, or, you are just yannking some chains to get a reaction...I'll just say this, and leave it at that...the ONLY way an airplane that is sitting on a runway can take off is to start a TAKE OFF ROLL....the plane HAS to have foward speed in order to attain AIR SPEED...now here on this planet, we have to assume that the airplane has WEIGHT, and this WEIGHT is sitting atop of wheels....the WHEELS are on the surface of the TREADMILL, which can match the speed of the rotating WHEELS of the airplane, and NO MATTER what kind of prop is pushing or pulling the aircraft, the aircraft CANNOT move forward without its wheels turning...unless you have some ******* magical way to suspend the airplane mere centimeters above the surface...so just because the damn prop is pushing or pulling against AIR , that dont mean squat. The forward motion HAS to transfer to the wheels, which will be negated by the counter moving treadmill. Have you EVER seen an airplane take off from ANYWHERE without its wheels turning first???? You use lots of buzzwords like thrust and mass and orhtogonal to make an impressive story, but its nonsensical!! Use your God given logic and think about it!As for the ridiculous post earlier about some stupid experiment with a helicopter...geeze! A helicopter and a plane are 2 completely different animals...a plane has a fixed wing and relys on forward motion of the fuselage that it's attached to in order to generate lift...whereas a helipcopter has a ROTATING WING that is powered to produce its own air speed. It can take off vertically and doesn't rely on its wheels having to turn at all.Peace out! Jay'04 FJR 1300

Check out this treadmill.....and notice that the dude is tethered to a frame so that he wont' "fly" away from the surface of the treadmill like our amazing magical no airspeed airplane!! LOLOL

AHAHAHAHAHA! Sorry I used those 'fancy' physics terms and 'equations' and that mumbo-jumbo....

Don't worry your head about this silly problem, just remember when you push the stick forward the houses get bigger....

HAHAHAHAHA He called me a 'moron'! :lol:

Somehow, somebody is going to find a way to 'splain this on you in a way you can apprehend. I look forward to the apology.

 

[FJR1300Mark]

The propeller would have to generate enough forward thrust to keep the airplane stationary to the ground with the treadmill trying to push it backwards.

The propeller / fuselage / wing combination on some planes will actually create lift while doing a static runup of the engine. So with the wheel breaks locked ie no forward motion, and the engine and propeller at max thrust the plane will weigh less on the ground as it has created some lift. A jet creates no lift as its exhaust is not directed over the wing.

And it can't create enogh lift over enough of the wing to lift itself. That is called a helicopter. Then it would work even if the "tread mill" was not moving.

Now put the airplane in a wind tunnel with the engine (or jet) providing enough thrust and having the wind tunnel matching and the plane could fly at a zero ground speed.

It is possible to fly smaller planes at a slowing speed than the wind and hense fly facing forward and go backward.

Fun thoughts

 

[exskibum]

Reason I asked the simple question up front (post no.2) and have watched this free for all since is exactly what Southern Cruizer pointed out in the problem: the treadmill is MATCHING the speed of the airplane wheels.

There IS friction in the bearings of the wheel, and because of that, the treadmill exerts a backwards force on the plane. The question seems to be whether the forward force vector of the plane created by the thrust of the prop or jet is equaled by the reverse force vector of the plane created by the treadmill (given the friction of the wheel bearings transmitting some of the force of the treadmill to the plane).

Seems to me this question is answered in the affirmative by the problem, though, since the wheels and treadmill are defined to be moving at the same speed. If the airplane is moving forward (generating airspeed and lift via differential air pressure over and under the wings), then the wheels MUST BE SPINNING FASTER than the treadmill. To stay within the parameters of the problem, the treadmill needs to speed up to match the wheel speed, until the friction of the wheel bearings is sufficient to overcome the thrust of the plane's prop (or jet engine) and keep it at a standstill (where wheel speed = treadmill speed) with no airspeed. No airspeed = no fly.

Looking forward to the namecalling to follow here.

 

[SouthernCruizer]

Reason I asked the simple question up front and have watched this free for all since is exactly what Southern Cruizer pointed out in the problem: the treadmill is MATCHING the speed of the airplane wheels.
There IS friction in the bearings of the wheel, and because of that, the treadmill exerts a backwards force on the plane. The question seems to be whether the forward vector of the plane created by the thrust of the prop or jet is equaled by the reverse vector of the plane created by the treadmill (given the friction of the wheel bearings transmitting some of the force of the treadmill to the plane).

Seems to me this question is answered in the affirmative by the problem, though, since the wheels and treadmill are defined to be moving at the same speed. If the airplane is moving forward (generating airspeed and lift via differential air pressure over and under the wings), then the wheels MUST BE spinning faster than the treadmill. To stay within the parameters of the problem, the treadmill needs to speed up to match the wheel speed, until the friction of the wheel bearings is sufficient to overcome the thrust of the plane and keep it at a standstill with no airspeed. No airspeed = no fly.

Looking forward to the namecalling to follow here.

*****************

That is the logical conclusion...so there are those that will HAHAHAHA it for sure

Jay

'04 FJR 1300

 

[Ford68xl]

Wow! Someone should tally up everyone in this poll who says the plane won't fly and those who say it will, then when the episode airs the "losers" owe the 'winners a huge F%*&^%$ing apology for 10 pages of crap!

Put me down for the plane will take off as normal ONCE the thrust over comes the friction of the bearings and tires caused by gravity. Once that occurs the plane won't care if the treamill spins at a million miles an hour. The skateboard test will prove this without the Mythbusters episode.

 

[SouthernCruizer]

I say that to all that think the airplane can fly off of a moving treadmill, cash out your pension funds, your 401K plans, IRA's, Bank CD's, mortgage your home, and INVEST in some huge treadmills!! You'll become instant billionairs, as you would save millions of square miles of land that is now being WASTED by airports for silly things like 2 mile long runways.

I think I'll keep my money in the bank though

Jay

'04 FJR 1300

 

[CDN_FJR]

Logic tells me the plane will take off without a problem. The plane pushes itself forward off of the density of the air, not off of it's traction/friction between the wheel and the ground.

Ding, Ding... we have a winner... the prop is grabbing air as it cork screws through the "fluid" (yes air is considered a fluid). If I was riding a skate board on a treadmill and had something like a rope (or propeller with engine instead of rope strapped to my back) to pull myself forward, I would be able to pull myself off the front of the treadmill. Forward motion would be achieved completely independent of what the skate board or treadmill was doing.

 

[Fred W]

I say that to all that think the airplane can fly off of a moving treadmill, cash out your pension funds, your 401K plans, IRA's, Bank CD's, mortgage your home, and INVEST in some huge treadmills!! You'll become instant billionairs, as you would save millions of square miles of land that is now being WASTED by airports for silly things like 2 mile long runways.
I think I'll keep my money in the bank though

Jay

'04 FJR 1300

Of course a plane *could* take off from a treadmill. The treadmill would just have to be 2 miles long, or the same length as a regular runway. I don't see how that would save anyone anything, but... no treadmill is going to MAKE a plane stand still if you crank up the engine thrust.

Yes, you could throttle way back and have the plane be stationary on a moving treadmill belt, but what's the point of doing that? Obviously it wouldn't take off that way.

 

[exskibum]

Logic tells me the plane will take off without a problem. The plane pushes itself forward off of the density of the air, not off of it's traction/friction between the wheel and the ground.

Ding, Ding... we have a winner... the prop is grabbing air as it cork screws through the "fluid" (yes air is considered a fluid). If I was riding a skate board on a treadmill and had something like a rope (or propeller with engine instead of rope strapped to my back) to pull myself forward, I would be able to pull myself off the front of the treadmill. Forward motion would be achieved completely independent of what the skate board or treadmill was doing.

Original problem: " . . . the hypothetical situation of the ability of an airplane to take off if it was on a conveyor belt spinning in the opposite direction of the wheels at the same speed of the wheels."

Please explain how one stays within the parameters of the problem (see highlighted portion above) with forward motion of the plane. If the plane is moving forward (to achieve lift via air moving over and under the wings), then the wheels MUST BE moving at GREATER SPEED than the treadmill. NO???

I'm not arguing that you couldn't throttle up the plane to overcome the rearward force of the treadmill. Of course you could, BUT the wheels would NECESSARILY be moving faster than the treadmill then, AND THAT ISN'T THE WAY THE PROBLEM WAS DEFINED!

 

[SouthernCruizer]

Logic tells me the plane will take off without a problem. The plane pushes itself forward off of the density of the air, not off of it's traction/friction between the wheel and the ground.

Ding, Ding... we have a winner... the prop is grabbing air as it cork screws through the "fluid" (yes air is considered a fluid). If I was riding a skate board on a treadmill and had something like a rope (or propeller with engine instead of rope strapped to my back) to pull myself forward, I would be able to pull myself off the front of the treadmill. Forward motion would be achieved completely independent of what the skate board or treadmill was doing.

****************

So, how could you pull yoursef forward off the front if the treadmill matches your foward motion? You pull harder, the treadmill simply spins faster to match your motion, net speed = 0

 

[Fred W]

So, how could you pull yoursef forward off the front if the treadmill matches your foward motion? You pull harder, the treadmill simply spins faster to match your motion, net speed = 0

That's a big Negative on that one, Mr. Name Caller.

The amount of reverse force applied from the treadmill belt will be limited to just that caused by the friction of the wheel bearings as they run on the belt (that is unless some dope has the brakes on).

The engines thrust is always applied to the air (not the wheels) and will be considerably greater than the reverse thrust from the freewheeling wheel drag.