Quoted: Quoted: Holy fuck, not another one WILL NOT FLY. (IF IT STAYS IN FIXED LOCATION) The wheels can be spinning 10,000 RPM, but unless there is AIRFLOW moving over the wings, it will not create lift. Unless the aircraft has a positive thrust to weight ratio with enough sheer thrust to take off strait up, the thing will not move. Or if the aircrafts speed overcomes the conveyors speed, and the aircraft starts moving. THE PLANE NEEDS TO MOVE FOREWARDS IN ORDER TO FLY. END IT NOW!!! It'll end as soon as people quit saying it won't fly There's nothing in the original scenario to keep the plane from moving.

Thank you for letting me know something i already know

Quoted: Okay, heres my question. Since i was under a wrongful assumption (IE, some "force" not allowing the plane to move individually of the treadmill), Then WHAT THE HELL ARE WE ARGUING ABOUT?! If the plane can move individually of the treadmill (IE, in real world without "magical" constraints), then what the hell is stopping it from moving?! The airplane wheels go from 0 RPM to full speed when a plane lands, and it doesn't affect the plane at all..... Where the fuck did this whole cluster fuck even come from?!

Quoted: Takes airflow over a wing.  thats why an airplane flies.  the wheels can go as fast as they want, but if there is no airflow on the wings, you ain't going no-where.  youre tires will blow depending on their rating. Its like a car on a dyno tester.  the wheels are movin, but it aint going anywhere, and the spoiler on the back....yeah it aint doing jack. This is an incredibly dumb question/scenario

What makes you think there wouldn't be airflow over the wing?
There is nothing in the original scenario to prevent the plane from moving thus creating airflow.

Quoted: Quoted: Won't fly.  No airflow over the wings for lift. ....except for the breeze created by that spinning thing in the front of the plane.

Wrong air source.

Quoted: Takes airflow over a wing.  thats why an airplane flies.  the wheels can go as fast as they want, but if there is no airflow on the wings, you ain't going no-where.  youre tires will blow depending on their rating. Its like a car on a dyno tester.  the wheels are movin, but it aint going anywhere, and the spoiler on the back....yeah it aint doing jack. This is an incredibly dumb question/scenario

This is an incredibly dumb answer.

Car =/= plane. Your "car on a dynamometer with a wing on the back" comparison is fucked.

Quoted: assuming the conveyor belt is long enough for the plane to gain speed, the plane will fly.

You have been converted!!!

Quoted: Thank you for letting me know something i already know

You obviously didn't know that at the point in the thread where I quoted you. you learned it later in the thread and had to go back and correct yourself.
My point still stands, this idiocy will end when people quit claiming the plane won't fly.

Quoted: If the plane can move individually of the treadmill (IE, in real world without "magical" constraints), then what the hell is stopping it from moving?!

Nothing.

The story goes that an airplane is on a magical conveyor belt in place of a runway. As the airplane accelerates, the conveyor belt moves in the opposite direction, supposedly at exactly the same speed as the airplane.

Now, if we were talking about a car, the belt could easily hold it in place. And thats why this has confused so many people who are not familiar with how airplanes work. People instinctively know that a conveyor belt could hold a car in place, because it would hold a person in place, and assume that the same rules for cars and people apply to airplanes.

Obviously they don't. The car must accelerate by directing it's thrust through it's wheels and into the ground, so the motion of the ground it's in contact with is relevant. A runner must direct his thrust into the ground with his legs. Airplanes universally direct their thrust into the air, somehow, and so the motion of the ground is irrelevant.

But the no fly people somehow manage to miss this distinction. They then try to sound smart by spouting some crap about airplanes needing airflow over their wings to fly which is correct but inane. As long as they can't understand the difference between how a car moves around on the ground and how an airplane does, they sure shouldn't be listened to when they talk about how an airplane flies.

-Local

Quoted: Quoted: Takes airflow over a wing.  thats why an airplane flies.  the wheels can go as fast as they want, but if there is no airflow on the wings, you ain't going no-where.  youre tires will blow depending on their rating. Its like a car on a dyno tester.  the wheels are movin, but it aint going anywhere, and the spoiler on the back....yeah it aint doing jack. This is an incredibly dumb question/scenario What makes you think there wouldn't be airflow over the wing? There is nothing in the original scenario to prevent the plane from moving thus creating airflow.

What is the origional scenario.  I thought it was an aircraft on a conveyor belt and the conveyor is running, the aircraft is going along the conveyor at the exact same speed creating relative motion?  yes or no?

If the airplane is magically stationary relative to the ground (0 groundspeed), then it is my understanding it wont fly because the airplane is not moving forward relative to the ground, not gaining airspeed to create lift to fly.


eta in the real world it will fly

Quoted: Takes airflow over a wing.  thats why an airplane flies.  the wheels can go as fast as they want, but if there is no airflow on the wings, you ain't going no-where.  youre tires will blow depending on their rating. Its like a car on a dyno tester.  the wheels are movin, but it aint going anywhere, and the spoiler on the back....yeah it aint doing jack. Now if they provide airflow over the wing/to the engine(s) when they are running at takeoff power, then you have a different scenario. Or if engine thrust to weight ratio is great than 1:1 and the aircraft is angled (then its a rocket, but it would fly) But sitting on an opposite rotating conveyor belt with no relative motion, the only thing that will turn are the wheels and the motors.  it takes at least somewhat of a relative forward motion for the plane to fly. And I'm a pilot, so whoever said pilots and engineers say it'll fly, not me. So unless I am misunderstanding the scenario, I vote it won't fly.

So I guess you can say a conveyor belt won't let this plane off the ground, right.
Stolen from another ar15.com thread

ETA: Not a RR
There is no power being used to drive the wheels like a car. There fore the plane will fly.

Quoted: Quoted: Thank you for letting me know something i already know You obviously didn't know that at the point in the thread where I quoted you. you learned it later in the thread and had to go back and correct yourself. My point still stands, this idiocy will end when people quit claiming the plane won't fly.

Im sorry if i offended you. I wasn't looking at it in the right "way" (again, because of false assumptions)

Quoted: Quoted: Quoted: Takes airflow over a wing.  thats why an airplane flies.  the wheels can go as fast as they want, but if there is no airflow on the wings, you ain't going no-where.  youre tires will blow depending on their rating. Its like a car on a dyno tester.  the wheels are movin, but it aint going anywhere, and the spoiler on the back....yeah it aint doing jack. This is an incredibly dumb question/scenario What makes you think there wouldn't be airflow over the wing? There is nothing in the original scenario to prevent the plane from moving thus creating airflow. What is the origional scenario.  I thought it was an aircraft on a conveyor belt and the conveyor is running, the aircraft is going along the conveyor at the exact same speed creating relative motion?  yes or no?

Here's the question.

A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?"

If they do it according to the word problem, or simulate the conditions on a smaller scale, then the plane will take off.

Quoted: Takes airflow over a wing.  thats why an airplane flies.  the wheels can go as fast as they want, but if there is no airflow on the wings, you ain't going no-where.  youre tires will blow depending on their rating. Its like a car on a dyno tester.  the wheels are movin, but it aint going anywhere, and the spoiler on the back....yeah it aint doing jack. Now if they provide airflow over the wing/to the engine(s) when they are running at takeoff power, then you have a different scenario. Or if engine thrust to weight ratio is great than 1:1 and the aircraft is angled (then its a rocket, but it would fly) But sitting on an opposite rotating conveyor belt with no relative motion, the only thing that will turn are the wheels and the motors.  it takes at least somewhat of a relative forward motion for the plane to fly. And I'm a pilot, so whoever said pilots and engineers say it'll fly, not me. So unless I am misunderstanding the scenario, I vote it won't fly.

you either misunderstand the scenario, or misunderstand how your machine works.  unlike a car on a road (or dyno), the airplane does not push against the ground to create any sort of movement.  The engines push against the air which in turn causes the airplane to move forward.

You should know that an airplane can fly with zero groundspeed-- IE, if it takes 100kts of airflow over the wings to produce enough lift to overcome the weight of the aircraft, it will fly, regardless of movement across the ground.  That means that if an airplane is pointed into a 100kt headwind, it will appear to hover over the ground.

The movement of the wheels are irrelevant.  An airplane propels itself by pushing against the air mass, not against the ground.

Sig line.

Quoted: Quoted: If the plane can move individually of the treadmill (IE, in real world without "magical" constraints), then what the hell is stopping it from moving?! Nothing. The story goes that an airplane is on a magical conveyor belt in place of a runway. As the airplane accelerates, the conveyor belt moves in the opposite direction, supposedly at exactly the same speed as the airplane. Now, if we were talking about a car, the belt could easily hold it in place. And thats why this has confused so many people who are not familiar with how airplanes work. People instinctively know that a conveyor belt could hold a car in place, because it would hold a person in place, and assume that the same rules for cars and people apply to airplanes. Obviously they don't. The car must accelerate by directing it's thrust through it's wheels and into the ground, so the motion of the ground it's in contact with is relevant. A runner must direct his thrust into the ground with his legs. Airplanes universally direct their thrust into the air, somehow, and so the motion of the ground is irrelevant. But the no fly people somehow manage to miss this distinction. They then try to sound smart by spouting some crap about airplanes needing airflow over their wings to fly which is correct but inane. As long as they can't understand the difference between how a car moves around on the ground and how an airplane does, they sure shouldn't be listened to when they talk about how an airplane flies. -Local

The thrust creates the forward motion, just the same as the vehicles tires or the runners shoes exert the forward motion to the ground.  airplanes simply displace air.  If the plane is moving at the exact same speed as the converyor belt in the opposite direction, it has no reltive motion and no relative wind.  There is no airflow going over the wings which is what is required for *most* airplanes to fly (those with greater than 1:1 thrust to weight ratio can takeoff vertically and that is all due to engine power and the wings and stabs are simply there for control surfaces and stability.)
If there is no realtive wind, the wing will not generate lift.  The wing has to create more than it's own weight in lift.  Lets say a Regional Jet weighs 50,000 lbs.  The wing has to produce more than 50,000 lbs of lift in order to get off the round.  The size of the wing will determine how much weight is "carried" by each sq. in. of the wing (loading)
But in order to get lift, there has to be airflow over the wing.
In your situation, there is no airflow over the wing.

Now if there was a huge fan out in front of the conveyor that was producing a wind, thats a different story.  If its a super windy day and the aircraft has a headwind that would allow the wing to generate more than its weight in lift, it will fly.

But under no circumstance will it fly if there is no wind going over the wings.  its basic aerodynamics.  The wheels will turn and turn until they blow, but the plane isn't leaving the ground.

There are many scenarios that could be put together with the plane/belt question, and they're all easily answerable.  Here are a few very simple variations:

1) The aircraft is on a backwards-moving conveyor belt.  A pilot would see the ground moving forward, and people on the ground would see the plane rushing backwards.

2) The aircraft is on a forwards-moving conveyor belt.  Things mentioned above reversed.

3) The aircraft is on a backwards-moving conveyor belt, but is holding the engines just high enough to keep the plane stationary with the ground.


Here's how #1 would play out:

The pilot wants to take off.  He turns on the engine and begins to power it up.  He begins to slow down.  Right now, the wind is rushing against the rear of the plane, trying to slow it down and fight against the motion of the belt.  It doesn't take much power to begin to turn the wheels.  He's still moving backwards, but not as fast, and the wheels are turning.  
 
He turns up the power, and finally he is stationary with the ground, and the wheels are spinning fast to keep up with the motion of the belt.  At this point, now that he has fought against the plane's backwards momentum, he can lower the throttle.  Remember, the only force that is trying to bring the plane along with the belt is the friction in the spinning wheels.  That's the only force the engine has to fight against.  How much power he needs to stay stationary with the ground depends on what condition the wheels are in - old and rusty and flat, or new and well-oiled.

Now the pilot is ready to take off.  He turns up the power.  Everything feels the same, except that the wheels are spinning faster than normal.  Since the ailerons and rudder steer a plane on the ground (at least the planes I'm familiar with), and therefore require airflow, steering would be the same on or off of a belt - except when he's moving backwards.  That might be weird.  His steering only depends on how he's moving in relation to the ground.

He begins to accelerate forwards down the backwards-moving belt.  Let's say his take-off speed is 60mph.  By the time he takes off, he is only moving at 60mph in relation to the ground, but the wheels are spinning at 60mph + the speed of the belt.  But other than the small amount of extra friction from the extra motion of the wheels, the takeoff is exactly the same.


Here's how #2 would play out:

Basically, he has a strong headwind.  His takeoff speed is 60mph minus the speed of the belt.  Takeoff is a breeze [rimshot].

Here's how #3 would play out:

This is just the second half of #1.



Any questions?  Would anyone like to insist that a conveyor belt has the ability to alter the laws of physics?

Quoted: If the airplane is magically stationary relative to the ground (0 groundspeed), then it is my understanding it wont fly because the airplane is not moving forward relative to the ground, not gaining airspeed to create lift to fly.

The airplane would have a groundspeed because the ground under it is moving relative to the airplane.  But, there is no airspeed.  The airspeed is what determines if a plane will fly or not.

There are different airspeeds, but the one to deal with is indicated airspeed.

Take for example a cessna 172 flying in the air at approach speed of 70 knots.  If there is a 70 knots head wind, the aircraft will be indicating 70 knots on the airspeed.  The groundspeed will read zero.

In the converyor belt situation and the conveyor is moving at 70 knots, the groundspeed would be 70, but since there is no air entering the pitot tubes because the airplane is stationary and there is no headwind or relative wind, the airspeed is 0

Quoted: Takes airflow over a wing.  thats why an airplane flies.  the wheels can go as fast as they want, but if there is no airflow on the wings, you ain't going no-where.  youre tires will blow depending on their rating. Its like a car on a dyno tester.  the wheels are movin, but it aint going anywhere, and the spoiler on the back....yeah it aint doing jack. Now if they provide airflow over the wing/to the engine(s) when they are running at takeoff power, then you have a different scenario. Or if engine thrust to weight ratio is great than 1:1 and the aircraft is angled (then its a rocket, but it would fly) But sitting on an opposite rotating conveyor belt with no relative motion, the only thing that will turn are the wheels and the motors.  it takes at least somewhat of a relative forward motion for the plane to fly. And I'm a pilot, so whoever said pilots and engineers say it'll fly, not me. So unless I am misunderstanding the scenario, I vote it won't fly.

The plane will move forward just as fast as if it was sitting on an airfield...the wheels will simply be spun faster than normal.
The thrust moving the plane foreward comes from the PROP...the wheels are just freewheeling.

It is NOTHING like a car on a dyno...the WHEELS move the car.
A rocket powered car on a dyno would shoot right off the end of the dyno.

Quoted: But under no circumstance will it fly if there is no wind going over the wings.  its basic aerodynamics.  The wheels will turn and turn until they blow, but the plane isn't leaving the ground.

But there WILL be air over the wings. No fan required.

Before we continue, I want you to understand that you actually disagree with people on this very board that design aircraft for a living. I'm not kidding. Do you really want to be THAT guy, who thinks an aeronautical engineer is full of shit? Think carefully before you continue. Re-read the responses so far, then read them again.

Quoted: The thrust creates the forward motion, just the same as the vehicles tires or the runners shoes exert the forward motion to the ground.  airplanes simply displace air.  If the plane is moving at the exact same speed as the converyor belt in the opposite direction, it has no reltive motion and no relative wind.  There is no airflow going over the wings which is what is required for *most* airplanes to fly (those with greater than 1:1 thrust to weight ratio can takeoff vertically and that is all due to engine power and the wings and stabs are simply there for control surfaces and stability.) If there is no realtive wind, the wing will not generate lift.  The wing has to create more than it's own weight in lift.  Lets say a Regional Jet weighs 50,000 lbs.  The wing has to produce more than 50,000 lbs of lift in order to get off the round.  The size of the wing will determine how much weight is "carried" by each sq. in. of the wing (loading) But in order to get lift, there has to be airflow over the wing. In your situation, there is no airflow over the wing. Now if there was a huge fan out in front of the conveyor that was producing a wind, thats a different story.  If its a super windy day and the aircraft has a headwind that would allow the wing to generate more than its weight in lift, it will fly. But under no circumstance will it fly if there is no wind going over the wings.  its basic aerodynamics.  The wheels will turn and turn until they blow, but the plane isn't leaving the ground.

I weep.

Airplanes are not cars. They don't care how fast the wheels turn. The wheels have nothing to do with how fast the airplane accelerates.

Think about it this way. Lets say you are standing on a skateboard placed on a conveyor belt. You are also holding onto a rope connected to the wall in front of you. Crank that conveyor up to 50 miles an hour while holding on to that rope. Now pull forward on the rope.

Do you really think you're not going to go forward?

It's the same situation for the airplane. The airplanes thrust has nothing to do with the ground, just like while on that skateboard your thrust has nothing to do with the wheels. All the wheels ever do in these situations is eliminate the friction with the ground, and by doing so they eliminate any influence the conveyor belt can have on you.

-Local

Quoted: Quoted: Takes airflow over a wing.  thats why an airplane flies.  the wheels can go as fast as they want, but if there is no airflow on the wings, you ain't going no-where.  youre tires will blow depending on their rating. Its like a car on a dyno tester.  the wheels are movin, but it aint going anywhere, and the spoiler on the back....yeah it aint doing jack. Now if they provide airflow over the wing/to the engine(s) when they are running at takeoff power, then you have a different scenario. Or if engine thrust to weight ratio is great than 1:1 and the aircraft is angled (then its a rocket, but it would fly) But sitting on an opposite rotating conveyor belt with no relative motion, the only thing that will turn are the wheels and the motors.  it takes at least somewhat of a relative forward motion for the plane to fly. And I'm a pilot, so whoever said pilots and engineers say it'll fly, not me. So unless I am misunderstanding the scenario, I vote it won't fly. So I guess you can say a conveyor belt won't let this plane off the ground, right. Stolen from another ar15.com thread ETA: Not a RR There is no power being used to drive the wheels like a car. There fore the plane will fly.

Okay, let me explain something to you.  you obviously must not be a pilot or anything close that has aeronautics involving it.

Did you not see the Husky move forward?  That creates airspeed.  Did you not see how large of a headwind the airplane had?  The camera catches the cound of the wind, the waves show how strong the headwind was, and the grass blowing also shows the headwind.

An aircraft can takeoff in 0 feet if the headwind is strong enough to create enough airflow over the wing for the wing to generate the amount of lift necessary to get the plane off the ground.

That airplane moved forward (and a husky can takeoff in an insanely short distance, but not sitting still.

You have to have relative wind over the wing moving at a speed fast enough to create the necessary lift.

If there is no headwind (as in the converyor belt situation), the plane will not fly.  It will have groundspeed, but no airspeed.  Airspeed is what is necessary for an airplane to fly.

Quoted: If there is no headwind (as in the converyor belt situation), the plane will not fly.  It will have groundspeed, but no airspeed.  Airspeed is what is necessary for an airplane to fly.

There will be airspeed. One more time, you actually disagree with people who design airplanes for a living. The airplane will move forward relative to a fixed object adjacent to the conveyor, regardless of conveyor speed. The conveyor can move backwards at 1,000,000mph, and it you nail the throttle on a Cessna, it will move forward and take off.

Quoted: Quoted: Quoted: If the plane can move individually of the treadmill (IE, in real world without "magical" constraints), then what the hell is stopping it from moving?! Nothing. The story goes that an airplane is on a magical conveyor belt in place of a runway. As the airplane accelerates, the conveyor belt moves in the opposite direction, supposedly at exactly the same speed as the airplane. Now, if we were talking about a car, the belt could easily hold it in place. And thats why this has confused so many people who are not familiar with how airplanes work. People instinctively know that a conveyor belt could hold a car in place, because it would hold a person in place, and assume that the same rules for cars and people apply to airplanes. Obviously they don't. The car must accelerate by directing it's thrust through it's wheels and into the ground, so the motion of the ground it's in contact with is relevant. A runner must direct his thrust into the ground with his legs. Airplanes universally direct their thrust into the air, somehow, and so the motion of the ground is irrelevant. But the no fly people somehow manage to miss this distinction. They then try to sound smart by spouting some crap about airplanes needing airflow over their wings to fly which is correct but inane. As long as they can't understand the difference between how a car moves around on the ground and how an airplane does, they sure shouldn't be listened to when they talk about how an airplane flies. -Local The thrust creates the forward motion, just the same as the vehicles tires or the runners shoes exert the forward motion to the ground.  airplanes simply displace air.  If the plane is moving at the exact same speed as the converyor belt in the opposite direction, it has no reltive motion and no relative wind.  There is no airflow going over the wings which is what is required for *most* airplanes to fly (those with greater than 1:1 thrust to weight ratio can takeoff vertically and that is all due to engine power and the wings and stabs are simply there for control surfaces and stability.) If there is no realtive wind, the wing will not generate lift.  The wing has to create more than it's own weight in lift.  Lets say a Regional Jet weighs 50,000 lbs.  The wing has to produce more than 50,000 lbs of lift in order to get off the round.  The size of the wing will determine how much weight is "carried" by each sq. in. of the wing (loading) But in order to get lift, there has to be airflow over the wing. In your situation, there is no airflow over the wing. Now if there was a huge fan out in front of the conveyor that was producing a wind, thats a different story.  If its a super windy day and the aircraft has a headwind that would allow the wing to generate more than its weight in lift, it will fly. But under no circumstance will it fly if there is no wind going over the wings.  its basic aerodynamics.  The wheels will turn and turn until they blow, but the plane isn't leaving the ground.

You're forgetting one thing...the free-spinning wheels of the plane negate any force the rear-moving treadmill  could exert on the airplane.  That leaves the engines producing thrust against the air behind them (not the ground, remember?), pushing the plane forward relative to the air and generating airflow over the wings.

Think of it like this...if you could build a conveyor belt of ice and put an ice-skater on it, then give that ice-skater a rope to hold onto, as the 'ice-belt' increases in speed, is the ice skater going to have to "pull harder" on the rope to stay in place?  Not measurably anyway, so that ice-skater could just as easily pull herself forward relative to, say, a knot tied in the rope when the ice-belt is turning 100 MPH as when it's standing still because the blades of the skates negate any rearward movement.  So think of the belt turning 100 mph and the skater is holding onto the rope.  As long as she can pull hard enough to overcome the tiny bit of resistance caused by the friction of the blades on the ice, so could a plane move forward through the air if it can overcome the small amount of friction in the wheels.

Quoted: Here's the question. A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?"

No, it won't fly.  it would have groundspeed as read from a GPS because the ground beneath it is moving relative to the wheels.  It won't have groundspeed as read from DME.

It WILL NOT have any airspeed.  Airspeed is what you need to get off the ground.  That is measured in the pitot tube(s)

Think of it as a car in neutral and a dyno hooked up.  the engine doesn't even have to be running.  Can you walk around the car?  do you feel any airflow over the car anywhere?  NO is the correct answer.

Lets take the plane in the same scenario.
Lets put a small airplane on a treadmill...same scenario as a large aircraft on a runway, just on a smaller scale.
With the engine(s) running at takeoff power and the treadmill/conveyor belt working in the opposite direction at the same speed, you walk around the airplane.  do you feel any airflow over the wings?  NO is the correct answer.  You will feel air being displaced from the engines, but that is relative.  if it is a turbojet airplane, no displaced air whatsoever is passing over the wings therefore, no lift.  No air goes into the pitot tube, therefor no airspeed.
No airspeed and no lift = no flying.

With a prop airplane, the props are usually ahead of the wings.  The displaced airflow would create some lift over the wings (accelerated lift) but you would have to have a C130 motor on a 172 to create enough lift to get it off the ground.  And if it did, it would be so noseheavy, it would wreck anyways.

So the plane will not fly...at all

Quoted: No, it won't fly.  it would have groundspeed as read from a GPS because the ground beneath it is moving relative to the wheels.  It won't have groundspeed as read from DME.

It WILL have groundspeed as read from DME. I'm frankly puzzled as to WHY you think people that design airplanes for a living are full of shit.

Why do you think airplanes are driven by their wheels? WHY? Why do you keep comparing it to a car? Why don't you think the wheels on an airplane do anything other than sit there and spin freely? WHY?

Quoted: Quoted: Here's the question. A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?" No, it won't fly.  it would have groundspeed as read from a GPS because the ground beneath it is moving relative to the wheels.  It won't have groundspeed as read from DME. It WILL NOT have any airspeed.  Airspeed is what you need to get off the ground.  That is measured in the pitot tube(s) Think of it as a car in neutral and a dyno hooked up.  the engine doesn't even have to be running.  Can you walk around the car?  do you feel any airflow over the car anywhere?  NO is the correct answer. Lets take the plane in the same scenario. Lets put a small airplane on a treadmill...same scenario as a large aircraft on a runway, just on a smaller scale. With the engine(s) running at takeoff power and the treadmill/conveyor belt working in the opposite direction at the same speed, you walk around the airplane.  do you feel any airflow over the wings?  NO is the correct answer.  You will feel air being displaced from the engines, but that is relative.  if it is a turbojet airplane, no displaced air whatsoever is passing over the wings therefore, no lift.  No air goes into the pitot tube, therefor no airspeed. No airspeed and no lift = no flying. With a prop airplane, the props are usually ahead of the wings.  The displaced airflow would create some lift over the wings (accelerated lift) but you would have to have a C130 motor on a 172 to create enough lift to get it off the ground.  And if it did, it would be so noseheavy, it would wreck anyways. So the plane will not fly...at all

LOL....you are hilarious.

Groundspeed has NOTHING to do with a plane generating lift.  the fact of the matter is, the wheels negate any force the ground can apply on the plane, so the rest of the equation is left to the engines and the air.

ETA:  Have you actually WATCHED the video linked to at the top of page 2?

Quoted: Quoted: Takes airflow over a wing.  thats why an airplane flies.  the wheels can go as fast as they want, but if there is no airflow on the wings, you ain't going no-where.  youre tires will blow depending on their rating. Its like a car on a dyno tester.  the wheels are movin, but it aint going anywhere, and the spoiler on the back....yeah it aint doing jack. Now if they provide airflow over the wing/to the engine(s) when they are running at takeoff power, then you have a different scenario. Or if engine thrust to weight ratio is great than 1:1 and the aircraft is angled (then its a rocket, but it would fly) But sitting on an opposite rotating conveyor belt with no relative motion, the only thing that will turn are the wheels and the motors.  it takes at least somewhat of a relative forward motion for the plane to fly. And I'm a pilot, so whoever said pilots and engineers say it'll fly, not me. So unless I am misunderstanding the scenario, I vote it won't fly. you either misunderstand the scenario, or misunderstand how your machine works.  unlike a car on a road (or dyno), the airplane does not push against the ground to create any sort of movement.  The engines push against the air which in turn causes the airplane to move forward. You should know that an airplane can fly with zero groundspeed-- IE, if it takes 100kts of airflow over the wings to produce enough lift to overcome the weight of the aircraft, it will fly, regardless of movement across the ground.  That means that if an airplane is pointed into a 100kt headwind, it will appear to hover over the ground. The movement of the wheels are irrelevant.  An airplane propels itself by pushing against the air mass, not against the ground.

You just answered your own question.

There is no headwind.  The wheels will turn and you would get a relative groundspeed, but you would not get an airspeed.  There is no wind in the conveyor belt scenario.  With no wind, there is no lift, with no lift, there is no flight (except for those aircraft with greater than 1:1 thrust to weight ratios)  which we aren't talking about.

The average airliner needs about 140 knots of airspeed give or take depending on weight...to take off.

In the conveyor situation, the wheels would turn and would have no bearing whatsoever on airspeed.  there is no air going into the pitot tubes, there is no air going over the wings, let alone the control surfaces to get the airplane off the ground.

Without any air over the wings, you get no lift.  Without any air over the elevator, you get no downpressure on the horizontal sbailizer which will not lift the nose of the airplane and will not create an angle of attack to get the airplane off the ground.
(all this is a mute point because there is no lift from the wing because there is no relative wind)

Quoted: Quoted: Quoted: Takes airflow over a wing.  thats why an airplane flies.  the wheels can go as fast as they want, but if there is no airflow on the wings, you ain't going no-where.  youre tires will blow depending on their rating. Its like a car on a dyno tester.  the wheels are movin, but it aint going anywhere, and the spoiler on the back....yeah it aint doing jack. Now if they provide airflow over the wing/to the engine(s) when they are running at takeoff power, then you have a different scenario. Or if engine thrust to weight ratio is great than 1:1 and the aircraft is angled (then its a rocket, but it would fly) But sitting on an opposite rotating conveyor belt with no relative motion, the only thing that will turn are the wheels and the motors.  it takes at least somewhat of a relative forward motion for the plane to fly. And I'm a pilot, so whoever said pilots and engineers say it'll fly, not me. So unless I am misunderstanding the scenario, I vote it won't fly. you either misunderstand the scenario, or misunderstand how your machine works.  unlike a car on a road (or dyno), the airplane does not push against the ground to create any sort of movement.  The engines push against the air which in turn causes the airplane to move forward. You should know that an airplane can fly with zero groundspeed-- IE, if it takes 100kts of airflow over the wings to produce enough lift to overcome the weight of the aircraft, it will fly, regardless of movement across the ground.  That means that if an airplane is pointed into a 100kt headwind, it will appear to hover over the ground. The movement of the wheels are irrelevant.  An airplane propels itself by pushing against the air mass, not against the ground. You just answered your own question. There is no headwind.  The wheels will turn and you would get a relative groundspeed, but you would not get an airspeed.  There is no wind in the conveyor belt scenario.  With no wind, there is no lift, with no lift, there is no flight (except for those aircraft with greater than 1:1 thrust to weight ratios)  which we aren't talking about. The average airliner needs about 140 knots of airspeed give or take depending on weight...to take off. In the conveyor situation, the wheels would turn and would have no bearing whatsoever on airspeed.  there is no air going into the pitot tubes, there is no air going over the wings, let alone the control surfaces to get the airplane off the ground. Without any air over the wings, you get no lift.  Without any air over the elevator, you get no downpressure on the horizontal sbailizer which will not lift the nose of the airplane and will not create an angle of attack to get the airplane off the ground. (all this is a mute point because there is no lift from the wing because there is no relative wind)

So answer me this one question.....WHY is there no headwind?

Again?

Just because it's labelled as official, doesn't mean it's not a dupe.

The plane will absoluetly fly. I will scoff at those of you who think it will not when you are proven wrong.

(Hint, I'm an avid R/C flyer, and I KNOW it will take off.)

The wheels have bearings that allow them to spin freely at any speed with a negligible amount of force imparted to the airplane.

If you put a model airplane (or anything with wheels on a conveyor belt) and turn on the belt, you could hold the plane (or hot wheels car, or whatever) in place on the moving belt with your finger. The bearings reduce the friction to almost nothing. The force needed to hold it there would be a fraction of an ounce.

Compare that to the multiple ounces (and sometimes, pounds) of thrust produced by your model airplane prop, and you can easily see how the plane will take off.

Quoted: Quoted: Takes airflow over a wing.  thats why an airplane flies.  the wheels can go as fast as they want, but if there is no airflow on the wings, you ain't going no-where.  youre tires will blow depending on their rating. Its like a car on a dyno tester.  the wheels are movin, but it aint going anywhere, and the spoiler on the back....yeah it aint doing jack. Now if they provide airflow over the wing/to the engine(s) when they are running at takeoff power, then you have a different scenario. Or if engine thrust to weight ratio is great than 1:1 and the aircraft is angled (then its a rocket, but it would fly) But sitting on an opposite rotating conveyor belt with no relative motion, the only thing that will turn are the wheels and the motors.  it takes at least somewhat of a relative forward motion for the plane to fly. And I'm a pilot, so whoever said pilots and engineers say it'll fly, not me. So unless I am misunderstanding the scenario, I vote it won't fly. The plane will move forward just as fast as if it was sitting on an airfield...the wheels will simply be spun faster than normal. The thrust moving the plane foreward comes from the PROP...the wheels are just freewheeling. It is NOTHING like a car on a dyno...the WHEELS move the car. A rocket powered car on a dyno would shoot right off the end of the dyno.

But the conveyor is moving at the exact same speed as the aircraft which means the aircraft looks as if it is still.

take a small plane and put it on a treadmill.  the plane is moving just as fast as the treadmill in opposite directions.  the speed cancel each other out.  the wheels are turning, but the entire airplane has no relative motion (you could walk around the treadmill while the wheels and conveyor belt are turning)

plane won't fly because there is no airspeed.  read my other posts for details

Quoted: No, it won't fly.  it would have groundspeed as read from a GPS because the ground beneath it is moving relative to the wheels.  It won't have groundspeed as read from DME. It WILL NOT have any airspeed.  Airspeed is what you need to get off the ground.  That is measured in the pitot tube(s) Think of it as a car in neutral and a dyno hooked up.  the engine doesn't even have to be running.  Can you walk around the car?  do you feel any airflow over the car anywhere?  NO is the correct answer. Lets take the plane in the same scenario. Lets put a small airplane on a treadmill...same scenario as a large aircraft on a runway, just on a smaller scale. With the engine(s) running at takeoff power and the treadmill/conveyor belt working in the opposite direction at the same speed, you walk around the airplane.  do you feel any airflow over the wings?  NO is the correct answer.  You will feel air being displaced from the engines, but that is relative.  if it is a turbojet airplane, no displaced air whatsoever is passing over the wings therefore, no lift.  No air goes into the pitot tube, therefor no airspeed. No airspeed and no lift = no flying. With a prop airplane, the props are usually ahead of the wings.  The displaced airflow would create some lift over the wings (accelerated lift) but you would have to have a C130 motor on a 172 to create enough lift to get it off the ground.  And if it did, it would be so noseheavy, it would wreck anyways. So the plane will not fly...at all

That's just sofa kind we todd did.

As I said before, the only thing . . . let me repeat . . . the ONLY THING keeping the plane following the conveyor belt is the friction of the spinning wheels.  That friction is a very tiny force, especially compared to the power of the engine.  To keep a plane stationary with a conveyor belt with the plane's engine on full power, you would have to accelerate the treadmill AMAZINGLY, MIND-BOGGLINGLY rapidly for that small force to keep up.  In a fraction of a second, the wheels would be spinning so fast that they'd pull themselves apart.

In a realistic scenario, you would not be able to do that.  No matter how hard you tried, the tiny force of the wheel friction would just not be strong enough to keep the wheels glued to the belt.

Live with it.

Quoted: No, it won't fly.  it would have groundspeed as read from a GPS because the ground beneath it is moving relative to the wheels.  It won't have groundspeed as read from DME. It WILL NOT have any airspeed.  Airspeed is what you need to get off the ground.  That is measured in the pitot tube(s) Think of it as a car in neutral and a dyno hooked up.  the engine doesn't even have to be running.  Can you walk around the car?  do you feel any airflow over the car anywhere?  NO is the correct answer. Lets take the plane in the same scenario. Lets put a small airplane on a treadmill...same scenario as a large aircraft on a runway, just on a smaller scale. With the engine(s) running at takeoff power and the treadmill/conveyor belt working in the opposite direction at the same speed, you walk around the airplane.  do you feel any airflow over the wings?  NO is the correct answer.  You will feel air being displaced from the engines, but that is relative.  if it is a turbojet airplane, no displaced air whatsoever is passing over the wings therefore, no lift.  No air goes into the pitot tube, therefor no airspeed. No airspeed and no lift = no flying. With a prop airplane, the props are usually ahead of the wings.  The displaced airflow would create some lift over the wings (accelerated lift) but you would have to have a C130 motor on a 172 to create enough lift to get it off the ground.  And if it did, it would be so noseheavy, it would wreck anyways. So the plane will not fly...at all

You have some very odd ideas here. I'm not sure if your even thinking about the same scenario. I can't even begin to understand what the hell you are talking about.

An f15 has something like 30,000 lbs of thrust at full afterburner. Lets for a moment suppose that the f15 manages to get up to 10mph before the belt kicks in. That means that the belt has to some how generate 30,000 lbs of force in the opposite direction in order to hold that aircraft motionless. The wheels are spinning at a net of 20 miles an hour.

So where, pry tell, is that additional 30,000 lbs of force in the opposite direction coming from? 3 greased roller bearings?

If you mention cars on dynos, you've misunderstood the scenario or the physics. There is simply no correlation to how an airplane behaves on the ground and how a car behaves. An airplane would roll right off a dyno just like a car would if you pushed on it's rear.

-Local

sigh

Quoted: Quoted: But under no circumstance will it fly if there is no wind going over the wings.  its basic aerodynamics.  The wheels will turn and turn until they blow, but the plane isn't leaving the ground. But there WILL be air over the wings. No fan required. Before we continue, I want you to understand that you actually disagree with people on this very board that design aircraft for a living. I'm not kidding. Do you really want to be THAT guy, who thinks an aeronautical engineer is full of shit? Think carefully before you continue. Re-read the responses so far, then read them again.

Read what he said before posting a knee-jerk response.  He said "if there is no wind going over the wings" it will not fly.  That is correct.  You're building a ridiculous strawman by claiming that he disagrees with aeronautical engineers.  No aeronautical engineer would ever disagree with what he posted.

You're doing what so many other people do that created this entire mess.  You're talking about one scenario while he is talking about another, and you're not taking the time to read what he actually posted.  This entire discussion is more about human nature and egos than about science.  With the usual scenario of course the plane will fly, and I can't imagine anyone ever not understanding that.  With the half-ass posts here that describe the problem, of course people get confused.  The problem isn't with the answers.  It's with the poor job done stating the problem.z

Sniper7, you have to be trolling. There's no way in hell you're this dense. After it's been explained to you countless times, you insist that there will be no air over the wings, when it is an absolute fact that there will be. Know why? Because the airplane will move forward relative to a stationary object adjacent to the conveyor, regardless of conveyor speed.

Put your car on a treadmill, leave it in neutral, and strap a jet engine on top. Let the conveyor move backwards at any speed you like (let's make it 1,000mph) Do you not agree that the car will move forward, albeit with the wheels turning VERY quickly?

Oh, for all you "conveyor belt will negate the plane's forward thrust" people...

The plane is NOT thrusting against the belt. It's thrusting against the AIR.

Doesn't matter how fast the belts going. If the AIR is still relative to the plane, it's going to fly, period.

Quoted: But the conveyor is moving at the exact same speed as the aircraft which means the aircraft looks as if it is still. take a small plane and put it on a treadmill.  the plane is moving just as fast as the treadmill in opposite directions.  the speed cancel each other out.  the wheels are turning, but the entire airplane has no relative motion (you could walk around the treadmill while the wheels and conveyor belt are turning) plane won't fly because there is no airspeed.  read my other posts for details

Please, quit flying now.  You obviously have NO clue about how your AC functions and it would seem that you are a danger to your general surroundings...

Quoted: I weep. Airplanes are not cars. They don't care how fast the wheels turn. The wheels have nothing to do with how fast the airplane accelerates. Think about it this way. Lets say you are standing on a skateboard placed on a conveyor belt. You are also holding onto a rope connected to the wall in front of you. Crank that conveyor up to 50 miles an hour while holding on to that rope. Now pull forward on the rope. Do you really think you're not going to go forward? It's the same situation for the airplane. The airplanes thrust has nothing to do with the ground, just like while on that skateboard your thrust has nothing to do with the wheels. All the wheels ever do in these situations is eliminate the friction with the ground, and by doing so they eliminate any influence the conveyor belt can have on you. -Local

Do you feel any wind on your face while you are on the skateboard?  From a bystander, you are still over than the fact that the wheels are turning on your skateboard and the conveyor belt is moving in the opposite direction.
You won't feel anything wind on your face.

Same with an airplane in your exact scenario.  the airplane won't feel any wind.  without any headwind, the plane WILL NOT FLY

Quoted: do we have to post the fucking you tube video 20 more times? www.youtube.com/watch?v=-EopVDgSPAk

That was my first time seeing that. If anyone still thinks it won't fly, I suggest watching the video.

why do you asshats keep hashing this shit out. I can understand starting another thread about the mythbusters show and discussing the show. but damn guys its getting old watching you guys act a fool saying the damn shit over and over.

Quoted: Quoted: Quoted: Takes airflow over a wing.  thats why an airplane flies.  the wheels can go as fast as they want, but if there is no airflow on the wings, you ain't going no-where.  youre tires will blow depending on their rating. Its like a car on a dyno tester.  the wheels are movin, but it aint going anywhere, and the spoiler on the back....yeah it aint doing jack. Now if they provide airflow over the wing/to the engine(s) when they are running at takeoff power, then you have a different scenario. Or if engine thrust to weight ratio is great than 1:1 and the aircraft is angled (then its a rocket, but it would fly) But sitting on an opposite rotating conveyor belt with no relative motion, the only thing that will turn are the wheels and the motors.  it takes at least somewhat of a relative forward motion for the plane to fly. And I'm a pilot, so whoever said pilots and engineers say it'll fly, not me. So unless I am misunderstanding the scenario, I vote it won't fly. The plane will move forward just as fast as if it was sitting on an airfield...the wheels will simply be spun faster than normal. The thrust moving the plane foreward comes from the PROP...the wheels are just freewheeling. It is NOTHING like a car on a dyno...the WHEELS move the car. A rocket powered car on a dyno would shoot right off the end of the dyno. But the conveyor is moving at the exact same speed as the aircraft which means the aircraft looks as if it is still. take a small plane and put it on a treadmill.  the plane is moving just as fast as the treadmill in opposite directions.  the speed cancel each other out.  the wheels are turning, but the entire airplane has no relative motion (you could walk around the treadmill while the wheels and conveyor belt are turning) plane won't fly because there is no airspeed.  read my other posts for details

Read my last post to see how wrong you are, but I'll just say again and put it another way . . . the plane's propellor is what moves it forward.  If the conveyor belt is moving backwards, what is pulling the plane backwards?  Only the friction of the wheels.  That's the only grip the belt has on the plane.  The propellor can EASILY fight against that and move forwards.

You are stuck on the wheels.  You are absolutely right that if the conveyor belt is moving as fast as the wheels, the plane isn't moving.  Your problem is that your whole PREMISE is wrong.  YOU CAN'T GET THE CONVEYOR BELT TO FIGHT AGAINST THE ENGINE!

Quoted: Quoted: Here's the question. A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?" No, it won't fly.  it would have groundspeed as read from a GPS because the ground beneath it is moving relative to the wheels.  It won't have groundspeed as read from DME. It WILL NOT have any airspeed.  Airspeed is what you need to get off the ground.  That is measured in the pitot tube(s) Think of it as a car in neutral and a dyno hooked up.  the engine doesn't even have to be running.  Can you walk around the car?  do you feel any airflow over the car anywhere?  NO is the correct answer. Lets take the plane in the same scenario. Lets put a small airplane on a treadmill...same scenario as a large aircraft on a runway, just on a smaller scale. With the engine(s) running at takeoff power and the treadmill/conveyor belt working in the opposite direction at the same speed, you walk around the airplane.  do you feel any airflow over the wings?  NO is the correct answer.  You will feel air being displaced from the engines, but that is relative.  if it is a turbojet airplane, no displaced air whatsoever is passing over the wings therefore, no lift.  No air goes into the pitot tube, therefor no airspeed. No airspeed and no lift = no flying. With a prop airplane, the props are usually ahead of the wings.  The displaced airflow would create some lift over the wings (accelerated lift) but you would have to have a C130 motor on a 172 to create enough lift to get it off the ground.  And if it did, it would be so noseheavy, it would wreck anyways. So the plane will not fly...at all

you're so close to understanding!  you walk around the airplane and you feel the engine pushing air right?  it's not pushing against the ground, it's pushing against the rest of the air around it!  it's the whole Newton thing... the engines are pushing air against other air, not air against the ground.  

the car comparison doesnt work here.  imagine this-- you have a boat on the surface of a shallow bit of water, and the boat has a wheel down to the bottom, and the wheel is resting on a treadmill.  The treadmill moves much like that in the airplane example-- does the boat move across the surface of the water (negating drag)?  YES!  because the boat engine pushes against the water, not the bottom of the lake, same as an airplane engine pushes against the air, and not against the ground the airplane takes off from.

Quoted: Quoted: I'd like to see how they're going to test it. Somehow I think acquiring a jet and building a big-ass conveyor belt are beyond even the mythbusters capabilities. And lets face it, a scale model won't suffice. Why won't a scale model suffice? Lift is lift. A conveyor is a conveyor. What's size got to do with it?

I stand corrected. I hadn't seen the youtube video with the guy, the air hog and the treadmill.  Looks like a scale model did a pretty damn good job to me.

Quoted: You're doing what so many other people do that created this entire mess.  You're talking about one scenario while he is talking about another, and you're not taking the time to read what he actually posted.  This entire discussion is more about human nature and egos than about science.  With the usual scenario of course the plane will fly, and I can't imagine anyone ever not understanding that.  With the half-ass posts here that describe the problem, of course people get confused.  The problem isn't with the answers.  It's with the poor job done stating the problem.z

The problem has been posted in it's entirety. He states (correctly) that if there is no air over the wings, the plane won't fly. What people are (enphatically) trying to explain to him - quite unsuccessfully - is that regardless of how fast the conveyor moves backwards, the plane WILL move forward and there WILL be air over the wings. The wheels will simply turn faster than they otherwise would.

He's glossing right over that, and keeps repeating the obvious fact that planes need air over the wings to fly.

Quoted: Quoted: If there is no headwind (as in the converyor belt situation), the plane will not fly.  It will have groundspeed, but no airspeed.  Airspeed is what is necessary for an airplane to fly. There will be airspeed. One more time, you actually disagree with people who design airplanes for a living. The airplane will move forward relative to a fixed object adjacent to the conveyor, regardless of conveyor speed. The conveyor can move backwards at 1,000,000mph, and it you nail the throttle on a Cessna, it will move forward and take off.

In the scenario, the airplane has no relative forward motion compared to a fixed object next to it.  lets say a building off the side of the runway.  you are on the other side of the runway (that is moving).  the airplane spools up its engines and andvances to takeoff power at the same time the conveyor is keeping the airplane in the exact same spot (no relative motion to the building).  The airplane is at full takeoff power and the conveyor keeps this airplane at a still spot (again no relative motion from the building behind from your spectator spot on the other side of the runway).
There is no headwind coming down the runway.  It is a calm day.

The airplane will not fly.  there is no headwind.  The engines are turning and the wheels are spinning, and there is no relative motion to the building, but the airplane will not fly.  no airspeed = no lift = no flight.

Quoted: Think about it this way. Lets say you are standing on a skateboard placed on a conveyor belt. You are also holding onto a rope connected to the wall in front of you. Crank that conveyor up to 50 miles an hour while holding on to that rope. Now pull forward on the rope. Do you really think you're not going to go forward? -Local Do you feel any wind on your face while you are on the skateboard?  From a bystander, you are still over than the fact that the wheels are turning on your skateboard and the conveyor belt is moving in the opposite direction. You won't feel anything wind on your face. Same with an airplane in your exact scenario.  the airplane won't feel any wind.  without any headwind, the plane WILL NOT FLY

As soon as I start pulling forward on the rope, absolutely I will feel wind. It won't be much, because I'm not going to be pulling my self to fast, but I would be moving forward and that folks is ground speed and airspeed.

Likewise, as soon as the airplane moves forward on the belt, and it will, it's wings will generate lift. As soon as it reaches it's takeoff speed it will take off. It will occur in virtually the same distance and the same amount of time, accepting for a tiny amount of extra drag in the wheel bearings (like, ounces).

look at it another way - an F15 comes in at 200mph for a touch and go landing pass. It flies down on the runway, but maintains its airspeed, so the wheels touch the ground, then it throttles up and flys away.

Ok, so add your moving runway to the picture. The plane comes it at 200mph again, the wheels hit the runway, which is going backwards at 200 mph, so what happens? does the plane instantly stop, ignoring the laws of momentum?!

no, the wheels go BRIRP! and spin up to 400mph, the pilot hits the throttle again and does his 'touch and go', just as before.

The engines on a plane do not react off the runway. If they did, then how do planes in alaska with skis instead of wheels get off the ground?!

You really seem to be stuck in the 'car' world of physics. Airplanes are not cars.