Airplane on Conveyor Belt Mythbusters 12/12

[twowheelnut]

Did you know that you could eat a different apple every day for more than 21 years, and never eat the same kind twice! Yup, it's true. There's 7,500 different varieties of apples and the apple tree is in the same flora family as the rose bush. Bet'cha didn't know that!

Oh, and JimLor... You're full of poo. A conveyor belt conveys things. That means it's in motion. I'm just sayin'... :grin:

 

[Scythian]

This has got to be the most amusing and ridiculous thread ever ! LOL...now I know why there are so few pilots around. There are 4 forces involved in flight...Thrust, Drag, Lift , and weight. Regardless of Thrust, Drag, or Weight ,without adequate air flow over a wing to create LIFT, that wing WILL NOT FLY...Ground speed means NOTHING. AIR SPEED is the determing factor to generate lift. Based on the assumption that a treadmill will spin at the same rate as the rolling landing gear, the plane remains motionless, both in ground speed and air speed(save for the little prop wash, which is not "clean" air flow over the entire wing). No air speed, no fly.
For the mathmatically challenged... L=CLV2p/2S

L = Lift

CL=Coeffieicent of lift

V = Velocity (in ft per sec)

p=Air Density

S = Wing surface area (Sq. ft.)

Jay

'04 FJR 1300

Private Pilot , Single Engine Land, PPC Land

HAHAHAHAHA! A Pilot! Condescending and Wrong.

The trick is that the treadmill cannot prevent motion relative to the ground (and air) unless the A/C is teathered. The question doesn't state it is teathered to the treadmill--if the treadmill were long enough, the plan would certainly take off.

Unlike motorcycles, airplanes don't use their wheels to gain velocity and the treadmill cannot prevent you from gaining airspeed.

 

[FJRay]

How many FJR owners does it take to fly a f#%*ing airplane?????????? :yahoo:

 

[GunMD]

Did you know that you could eat a different apple every day for more than 21 years, and never eat the same kind twice! Yup, it's true. There's 7,500 different varieties of apples and the apple tree is in the same flora family as the rose bush. Bet'cha didn't know that!

Getting a little soft in your old age, aren't you? What happened to the confrontational guy we all know and love like? And what, no " :****: "??

 

[twowheelnut]

Did you know that you could eat a different apple every day for more than 21 years, and never eat the same kind twice! Yup, it's true. There's 7,500 different varieties of apples and the apple tree is in the same flora family as the rose bush. Bet'cha didn't know that!

Getting a little soft in your old age, aren't you? What happened to the confrontational guy we all know and love like? And what, no " :****: "??

Go back and look at my edit. :****:

 

[JimLor]

Nutman - that's why I stipulated a freewheeling conveyer belt - I have seen them used to xfer stuff - usually from higher to lower using gravity as the motive force.

Actually, if the belt is in fact moving, the plane will likewise takeoff as normal.

And Happy Birthday.

 

[twowheelnut]

I shoulda left the heavy tackle at home.

 

[Groo]

An airplane's jet engine or propeller are equivalent to and can be replaced by someone standing in front of the conveyer belt with a rope, tied to the nose of the plane (think a hang glider...). The conveyer belt can rotate as much as it wants, and at an infinite speed to make the planes wheels spin backwards, but if the guy in front of the conveyer belt pulls on the rope (or the engine pushes on the body of the plane), the plane moves forward.

 

[Fred W]

I shoulda left the heavy tackle at home.

4 lb test woulda' been just fine...

 

[SouthernCruizer]

HAHAHAHAHA! A Pilot! Condescending and Wrong.

The trick is that the treadmill cannot prevent motion relative to the ground (and air) unless the A/C is teathered. The question doesn't state it is teathered to the treadmill--if the treadmill were long enough, the plan would certainly take off.

Unlike motorcycles, airplanes don't use their wheels to gain velocity and the treadmill cannot prevent you from gaining airspeed.

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

when you decide to mock someone, make sure your argument makes sense so you don't look even more the fool.

1. "The trick is that the treadmill cannot prevent motion relative to the ground ..." WHAT ARE YOU TALKING ABOUT?? the treadmill *IS* the ground!! The plane is SITTING ON THE TREADMILL!!

2. "Unlike motorcycles, airplanes don't use their wheels to gain velocity..." WHAT??? How the hell does an airplane gain velocity to achieve take off speed??? On the ground, its by use of wheels...on water, its by pontoons or boat belly! Imagine an airplane, lets say a Cessna 152 for example. Take off its wheels, and it will not take off! Thrust has to overcome drag in order for it to fly. Lift has to overcome weight in order for it to sustain flight. What you probably meant to say was that unlike a motorcycle, the wheels are NOT powered. This is true, but the thrust from an airplane (generally speaking) is not great enough to pull the weight along the ground fast enough to achieve take off speed without help from wheels/skids/etc.

So, lets analyze the scenario. The Cessna 150 is put on a treadmill. The treadmill can either be powered or free wheeling (kinda like a dyno for a bike). The Cessna is powered up...the pilot has his brakes on, so the plane and the treadmill do not move at all. He releases the brakes, engine at 1000 rpm (idle)...the plane starts to roll forward, but the treadmill moves rearward at exaclty the same speed as the wheels, so the plane does not move relative to you standing there watching. Now, although the wheels on the plane are not gear driven, the prop pulling air will cause the mass of the plane to move forward, thus the treadmill moves rearward. Net movement relative to you is zilch. Remember, the plane has WEIGHT, so it is VERY much attached to the treadmill(ground). Until the plane achieves enough forward motion to have mandatory air speed for liftoff, it WILL remain heavy on the wheels, which WILL drive the wheels, which WILL move the treadmill. As the pilot continues to apply power, the plane continues to be thrust forward, and of course, the treadmill continues to move rearward. Again, there is ZERO wind moving across the wings (cept for prop blast), so it cant lift off, but it WILL continue to roll forward on the "ground", which causes the "ground" (treadmill) to quicken its rearward movement. We can keep this up all day long, throttle firewalled, and the damn treadmill will continue to match the "speed" of the takeoff roll to the point that the plane never achieves its rotation speed to take off, since there is NO airspeed.

If you really dont think that the wheels have anything to do with the plane taking off, think about this. Have you ever seen a big jet airliner that has gone off the runway, and is stuck in mud or snow? You can give it throttle, but I be damn if the sunny beach flys off the ground! Cause the damn wheels are STUCK!! The jet is pushing the air, but that dont mean squat if the wheels cant move!

The same thing would happen to a boat if you made a "water treadmill" that could be controlled so that the current would run opposite the thrust of the boats prop...you would give the boat full throttle, and the current of water would increase to match the thrust, and the boat would just SIT THERE with no relative movement to the beach.

The ONLY way a plane could take off from a treadmill in calm air would be if somehow it could move forward to take off speed before the treadmill was active. In the case of the Cessna 150 , you would have to achieve a forward speed of 55mph or more to get the air flow over the wings enough to cause lift!

Jay

'04 FJR 1300 :dribble:

 

[SouthernCruizer]

An airplane's jet engine or propeller are equivalent to and can be replaced by someone standing in front of the conveyer belt with a rope, tied to the nose of the plane (think a hang glider...). The conveyer belt can rotate as much as it wants, and at an infinite speed to make the planes wheels spin backwards, but if the guy in front of the conveyer belt pulls on the rope (or the engine pushes on the body of the plane), the plane moves forward.

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

Only one problem with that scenario...in the case of a plane, the engine and prop are ON the treadmill, not off in front on solid ground like someone pulling with a rope.

Jay

'04 FJR 1300

 

[Rondo777]

An airplane's jet engine or propeller are equivalent to and can be replaced by someone standing in front of the conveyer belt with a rope, tied to the nose of the plane (think a hang glider...). The conveyer belt can rotate as much as it wants, and at an infinite speed to make the planes wheels spin backwards, but if the guy in front of the conveyer belt pulls on the rope (or the engine pushes on the body of the plane), the plane moves forward.

Your rope is the reason the plane didnt shoot off backwards! If the rope wasnt there the wheels would not turn and the plane would move along backwards on the tread. The plane, relative to the tread would still have a 0 ground speed. Now if you gradually start to add power to the plane it would start rolling along the tread. The plane would be moving forward on the tread but still be moving backwards from the point of view of somebody watching from the side (NOT ON THE TREADMILL) as you increse power to the plane, it would be moving forward faster and faster in relation to the tread on the treadmill but until you give the plane enough power to at east match the speed of the treadmill it is still moving backwards and until you actually have forward motion in relationship to the surrounding air, you aint gonna be flyin. If you keep increasing power past the point of the speed of the treadmill (your EXTRA tug on the rope) then yes, you will start to move forward. I'm under impression that this is a powered treadmill that can be made to move at the same max speed as the plane can produce forward thrust. If it were a free wheeling treadmill then the plane would indeed just take off as usual.

 

[Rondo777]

This has got to be the most amusing and ridiculous thread ever ! LOL...now I know why there are so few pilots around. There are 4 forces involved in flight...Thrust, Drag, Lift , and weight. Regardless of Thrust, Drag, or Weight ,without adequate air flow over a wing to create LIFT, that wing WILL NOT FLY...Ground speed means NOTHING. AIR SPEED is the determing factor to generate lift. Based on the assumption that a treadmill will spin at the same rate as the rolling landing gear, the plane remains motionless, both in ground speed and air speed(save for the little prop wash, which is not "clean" air flow over the entire wing). No air speed, no fly.
For the mathmatically challenged... L=CLV2p/2S

L = Lift

CL=Coeffieicent of lift

V = Velocity (in ft per sec)

p=Air Density

S = Wing surface area (Sq. ft.)

Jay

'04 FJR 1300

Private Pilot , Single Engine Land, PPC Land

HAHAHAHAHA! A Pilot! Condescending and Wrong.

The trick is that the treadmill cannot prevent motion relative to the ground (and air) unless the A/C is teathered. The question doesn't state it is teathered to the treadmill--if the treadmill were long enough, the plan would certainly take off.

Unlike motorcycles, airplanes don't use their wheels to gain velocity and the treadmill cannot prevent you from gaining airspeed.

HOHOHOHOHO! I'm another pilot and l say YOUR wrong. I defend my Pilot Brother! The plane would be moving backwars relative to the air if it were just sitting on the tread mill. If the plane was powered up it would first have to overcome the backward motion exerted on it from the tread mill just to stay in one place. If the power on the tread mill is increased or decresed to match the forward thrust of the plane then NO FORWARD MOTION, NO AIR SPEED, NO FLYING :argue:

 

[GunMD]

1. "The trick is that the treadmill cannot prevent motion relative to the ground ..." WHAT ARE YOU TALKING ABOUT?? the treadmill *IS* the ground!! The plane is SITTING ON THE TREADMILL!!

In this argument the treadmill (or conveyor as it has been refered to) is NOT the same as the ground. The conveyor is indeed what the plane is sitting on but it is distinctly different than the ground. The ground doesn't move while the surface of the conveyor does. When speaking about the ground we're talking about the area of land around the conveyor that is totally stationary.

Have you ever seen a big jet airliner that has gone off the runway, and is stuck in mud or snow? You can give it throttle, but I be damn if the sunny beach flys off the ground! Cause the damn wheels are STUCK!! The jet is pushing the air, but that dont mean squat if the wheels cant move!

I think here you have illustrated the point against your argument. In the scenario of the mud beyond the end of a runway (or sand, snow, whatever) the wheels cannot move...they're being held in place. Almost as if they were chained down to the ground. However, in the scenario with this conveyor type runway the wheels are free to do what wheels generally want to do...rotate...move...spin...however you define it there is nothing securing them to their surface. Poof! The aircraft is free to move forward relative to the air and relative to the stationary ground around the conveyor. (Most importantly relative to the air).

Crap, when is this episode supposed to be on TV? We need to settle this soon b'for someone get's hurt feelin's.

 

[Scab]

Somebody kill me.

 

[xviper]

Ooooooo....here is a much better way to look at it.
This helps clear it up (I think so anyway).

OK, I promise this is the last response till the show airs. h34r:

One big flaw in this illustration - the chopper is not exerting its full weight on the treadmill. In the stated scenario where the treadmill is horizontal on the ground, the full weight of the craft is on the wheels. This weight will give rolling resistance to the wheel bearings and the bigger component of all, rolling resistance to the tires (they aren't just free spinning, frictionless). The more weight, the more rolling resistance. Can a Piper Cub do it? I don't think so. Can an F18 Super Hornet do it if the treadmill was long enough? Probably. But then, why even bother with building a treadmill that long? Wasn't the "flavour" behind this myth, to not have a long runway? Again, it would be nice to know what the original intention of this myth was.

Crap, when is this episode supposed to be on TV? We need to settle this soon b'for someone get's hurt feelin's.

This is always a risk, especially if you take everything as a "pissing match". If you're mature enough to take it as a debate or a discussion where everyone is free to give a statement of opinion and others are free to give a rebuttal, then feelings shouldn't get hurt. It's only when egos get the better of people that it becomes a pissing match.

 

[GunMD]

If you're mature enough to take it as a debate or a discussion where everyone is free to give a statement of opinion and others are free to give a rebuttal, then feelings shouldn't get hurt. It's only when egos get the better of people that it becomes a pissing match.

Agreed....I was being a bit sarcastic. :thumbsup: I'm rather enjoying the thought provoking conversation here.

Then again, this crowd does have a tendency to get a little "excited" about debates. :dntknw:

 

[twowheelnut]

Somebody kill me.

OK. Watch this SLIGHTLY NWS vid...

https://youtube.com/watch?v=zIyBms6k9vY

Can we please have video embedding? Please?

 

[Rondo777]

Ooooooo....here is a much better way to look at it.
This helps clear it up (I think so anyway).

OK, I promise this is the last response till the show airs. h34r:

One big flaw in this illustration - the chopper is not exerting its full weight on the treadmill. In the stated scenario where the treadmill is horizontal on the ground, the full weight of the craft is on the wheels. This weight will give rolling resistance to the wheel bearings and the bigger component of all, rolling resistance to the tires (they aren't just free spinning, frictionless). The more weight, the more rolling resistance. Can a Piper Cub do it? I don't think so. Can an F18 Super Hornet do it if the treadmill was long enough? Probably. But then, why even bother with building a treadmill that long? Wasn't the "flavour" behind this myth, to not have a long runway? Again, it would be nice to know what the original intention of this myth was.

Crap, when is this episode supposed to be on TV? We need to settle this soon b'for someone get's hurt feelin's.

This is always a risk, especially if you take everything as a "pissing match". If you're mature enough to take it as a debate or a discussion where everyone is free to give a statement of opinion and others are free to give a rebuttal, then feelings shouldn't get hurt. It's only when egos get the better of people that it becomes a pissing match.

HELI is a completly different animal and the example is 100% unrelated. Helicopters do not fly. "THEY BEAT THE AIR INTO SUBMISSION". The Rotor on the top of the heli flys and is just taking the fusalage along for the ride. The rotor is equivilent of the wing on an airplane. The rotatation of the Rotor creates the airflow across the blade and thus produces the lift. The "wing" of a helicopter is driven forward directly by the motor thus no motion of the fuselage is required, thats why they can hover. The heli treadmill has 0 effect. That guy that did the experiment in the video should have used an RC plane on a treadmill, He is clueless!!!

 

[ponyfool]

Xviper and Rondo, sorry, but you are wrong.

We all agree the plane will not fly because there is no air flow over the wings. No argument there.

Where we don't agree, and where you are wrong, is the fact that you are confusing forward motion due to wheels (like a car or motorcycle) to forward motion by an external force that is NOT related to the contact between the wheels and treadmill.

I'll explain it a different way.

Get a skate board and put it on a treadmill. Turn the tread mill on. The skate board wheels will spin, but the friction between the wheels and tread, as well as the bearings friction will cause the skate board to fly off the back of the treadmill. We agree on that, right?

Now, take a scale (like they use in the grocery store to weigh fruit) and attach it to the front of the skateboard. With the treadmill running at 5 mph, and you holding the scale steady so the skateboard doesn't have any forward or backwards motion (zero ground speed). Read the scale. It will have X pounds. This is the amount of force needed to overcome the friction of the wheels and bearings. In a zero friction environment (which doesn't exist), this would be zero because the wheels would spin and the skateboard will just sit still. We agree on that, right?

Now, using your hand pull on the scale. What happens? Does the skate board stay still and maintain zero ground speed? Or, does the skateboard move forward?

If you are having problems the answer is, it moves forward. The weight displayed on the scale will increase. This is the amount of force above the friction you are applying to move the skateboard forward. This is no different than the thrust an engine provides.

Now, assuming the treadmill's speed doesn't increase, the instant you pull on the scale, the skateboard's wheel speed increases because it is now moving forward on the treadmill.

Now, let's assume the treadmill's speed increases at the same rate of forward motion of the skateboard. Since you are already pulling on the scale at a force above and beyond what's necessary to overcome the friction aspect, the ONLY thing that will happen is, the skateboard's wheels will spin faster and the skateboard will move forward as you pull it.

So, if you can explain to me how your pulling on the scale wouldn't result in the skateboard moving forward, I'd love to hear it.

By the way, this was a question that we investigated, tested, and proved using very similar apparatus as outlined above in my college physics class in 1987.