quote Originally posted by rogergarrison: No matter how many times I read it, it still says to me the treadmill is comptr controlled to stop any forward movement no matter how much power the engine has.

You can interpret it any which way floats your boat Roger, but that's clearly NOT what the original scenario states.

quote Original scenario: 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). The question is: Will the plane take off or not?

Even concrete floats.

I'm kinda with Roger. There's something missing. No joking here.
Via laser radar, if a plane is taxiing at 30 mph and moves onto the conveyor, moving in the opposite direction at 30 mph, why would the plane be moving forward from a ground spectator's point of view? Thrust is pushing it to go 30 mph but if the conveyor is moving in reverse, it's standing still.

If a plane is flying at 100 mph and hits a headwind of 100 mph, is it moving forward?

quote Originally posted by Gokart Mozart: If a plane is flying at 100 mph and hits a headwind of 100 mph, is it moving forward?

totally different.. I cant believe there are still people talking about this, its so simple this is pathetic... no wonder this world is such a mess..

quote Originally posted by AJ7: totally different.. I cant believe there are still people talking about this, its so simple this is pathetic... no wonder this world is such a mess..

This explains how everyone should be judged. Warning NWS language.

quote Originally posted by Gokart Mozart: Even concrete floats.

You’re willing to concede that concrete floats, but not that the plane will fly?

Alrighty then, my post from page one still stands.

quote Originally posted by Patrick: Oh good gawd, this is hopeless...

lol, OK, lets go out of the box.

You all know the swamp boats used in places like the everglades. They operate by skimming over whatever surface, water, plants, mud etc powered by an engine driven propeller just like a plane. Could even be a jet engine for that matter. Now lets look at one of these....lets say this airboat goes 40 mph on calm water at max power. It would take no time at all to travel a measured mile right. Now take this same airboat and put it on a river that has a 40mph fast moving current. Will the airboat still travel that measured mile ? Im thinking this airboat isnt going anywhere because it cant go faster than 40 mph and its taking all its power against the current just to maintain its position....Now isnt this the same thing as our airplane with the boat representing the propeller driven airplane and the opposing current representing the treadmill ?

quote Originally posted by rogergarrison: lol, OK, lets go out of the box. You all know the swamp boats used in places like the everglades. They operate by skimming over whatever surface, water, plants, mud etc powered by an engine driven propeller just like a plane. Could even be a jet engine for that matter. Now lets look at one of these....lets say this airboat goes 40 mph on calm water at max power. It would take no time at all to travel a measured mile right. Now take this same airboat and put it on a river that has a 40mph fast moving current. Will the airboat still travel that measured mile ? Im thinking this airboat isnt going anywhere because it cant go faster than 40 mph and its taking all its power against the current just to maintain its position....Now isnt this the same thing as our airplane with the boat representing the propeller driven airplane and the opposing current representing the treadmill ?

no but it would still go up stream... this has already been covered in this thread with a hovercraft...

hovercraft is completely different...it has no contact with the ground at all.

So how come my RC airboat got swept downstream in the creek ? It wouldnt come back against the current with full throttle and went byby somewhere downstream................

quote Originally posted by rogergarrison: So how come my RC airboat got swept downstream in the creek ? It wouldnt come back against the current with full throttle and went byby somewhere downstream................

Pilot error.

quote Originally posted by rogergarrison: hovercraft is completely different...it has no contact with the ground at all. So how come my RC airboat got swept downstream in the creek ? It wouldnt come back against the current with full throttle and went byby somewhere downstream................

Were the boat's landing gear deployed?

quote Originally posted by Gokart Mozart: I'm kinda with Roger. There's something missing. No joking here. Via laser radar, if a plane is taxiing at 30 mph and moves onto the conveyor, moving in the opposite direction at 30 mph, why would the plane be moving forward from a ground spectator's point of view? Thrust is pushing it to go 30 mph but if the conveyor is moving in reverse, it's standing still. If a plane is flying at 100 mph and hits a headwind of 100 mph, is it moving forward?

Once again, air has a much greater impact on the plane then the friction introduced through the wheels. The 100MHP headwind would certainly affect the plane, whereas the conveyor belt would barely have an impact. The friction imposed on the wheels by the conveyor belt is not equal to the trust generated by the engine of the plane. The additional friction of the wheels and bearings introduced to the plane once it hit the conveyor belt may slow it down a tad bit, but it wouldn't be enough force to bring the plane to a stop.

Here's an experiment. Take any R/C plane (even a cheap $20 air hog will suffice) and place it on a conveyor belt. The R/C plane will move backwards with the conveyor belt once you place it on it, but as soon as you power it up; it will soon out run the speed of the conveyor belt, and take off. (A treadmill or baggage belt at an airport would work for this experiment, although the Youtube videos posted a while ago already show this to be true).

quote Originally posted by rogergarrison: hovercraft is completely different...it has no contact with the ground at all. So how come my RC airboat got swept downstream in the creek ? It wouldnt come back against the current with full throttle and went byby somewhere downstream................

Once again, the key element is friction. There's a lot more friction between water and any object placed in that water then there is with an object with wheels placed on tarmac. Take a cheap used Honda for example. A cheap used Honda may make about 100HP, but yet that's still enough power to overcome the rolling resistance and air resistance (land and air friction) for it to be able to reach 100MPH. Now take a lightweight boat and power it with the same Honda engine. Due to the water's friction, that boat will never reach the same 100MPH in water that it can reach on land. Why? Because there's a lot more friction between that boat & water then there is between the car & road/air. (Bad annology, I know, but the best illustration I could come up with between the plane and water, and the plane and road/conveyor belt).

In short, the reason the plane was swept downstream is there was a lot more friction between the plane and the moving stream; and your plane's motor just couldn't create enough thrust to overcome that friction.

quote Originally posted by Deabionni: Here's an experiment. Take any R/C plane (even a cheap $20 air hog will suffice) and place it on a conveyor belt. The R/C plane will move backwards with the conveyor belt once you place it on it, but as soon as you power it up; it will soon out run the speed of the conveyor belt, and take off. (A treadmill or baggage belt at an airport would work for this experiment, although the Youtube videos posted a while ago already show this to be true).

I've already posted video of this type of demonstration. They still don't believe it. It's useless to keep trying.

Ok, I’ve been avoiding this since it started.

Everyone agrees enough airflow has to go over the wings to create lift regardless of the planes speed.

Correct?

A full sized aircraft (Cessna) engine cannot pass enough air over the wings to create the lift needed to get airborne without forward momentum.

Correct?

But could a twin engine turboprop with both engines attached to the wings?

?????

However: Nick’s toy plane with the two engines directly over the wings can create enough lift at zero mph to lift the extremely light plane. I’d bet if Nick held onto the plane and maxed the engines he could feel the lift being generated. Even if he used his bandaged hand.

quote Originally posted by mike-ohio: Ok, I’ve been avoiding this since it started. Everyone agrees enough airflow has to go over the wings to create lift regardless of the planes speed. Correct? A full sized aircraft (Cessna) engine cannot pass enough air over the wings to create the lift needed to get airborne without forward momentum. Correct? But could a twin engine turboprop with both engines attached to the wings? ????? However: Nick’s toy plane with the two engines directly over the wings can create enough lift at zero mph to lift the extremely light plane. I’d bet if Nick held onto the plane and maxed the engines he could feel the lift being generated. Even if he used his bandaged hand.

The airplanes engine is not blowing air over the wing to generate lift. The spinning propeller is producing a force that is equivalent to thrust. This force pulls the airframe of the aircraft forward, wing being part of the airframe. The wheels will roll because the axles they are attached to are attached to the airframe (like wheels on a matchbox car when you roll it) . The conveyor beneath the airplane will not effect the engines ability to pull the airframe forward through the air. The conveyor will only be able to apply a force against the free rolling wheel of the airplane. Since the conveyor will try to match the aiplanes speed but in reverse it will spin the tires faster. The faster rate of the tires will not cause the airplane to slow down because they are free spinning on the axles.

Roger your problem with your R/C airboat is that water generates alot of drag against the hull of the boat. The airplane ,if it had no wheels would have a helluva time trying to overcome the drag produced by the landingear draging across the runway/conveyor. This is why wheels are installed . Have you ever run your airboat on dry/wet grass? Which surface did it actually move easier/at all on? I'm betting the wet grass since it would produce less friction/drag against the hull. Essentially the aircraft does not realy on its wheels for propulsion only its engine and propellor.

Lets say this. How about as the airplane accelorates the conveyor moves in the same direction as the aircraft . Would the cause the aircraft to take off faster? Only ever so slightly because any drag produced from having to roll the wheels would be eliminated and the airplane could accelorate faster . . . . slighty as in an insignificant amount.

The only way to make make the plane not fly is to blow air into the propellor at the same speed the propellor is pushing it out, but only in the area of the propellor. If you did it around the whole aircraft it would have the necesary airflow over the wings to produce lift.

The airplane will fly

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ARCHIES JUNK IS FASTER THAN SHAUNNA'S JUNK

quote Originally posted by mike-ohio: Ok, I’ve been avoiding this since it started. Everyone agrees enough airflow has to go over the wings to create lift regardless of the planes speed. Correct? A full sized aircraft (Cessna) engine cannot pass enough air over the wings to create the lift needed to get airborne without forward momentum. Correct? But could a twin engine turboprop with both engines attached to the wings? ????? However: Nick’s toy plane with the two engines directly over the wings can create enough lift at zero mph to lift the extremely light plane. I’d bet if Nick held onto the plane and maxed the engines he could feel the lift being generated. Even if he used his bandaged hand.

None of that matters. The only relevant question is can the conveyor keep the plane from moving. If it can, the plane doesn't fly. If it cannot, the plane can accelerate and fly.

FIEROPHREK/Formula88,

I agree that there would not be enough airflow over the airframe/wings on a standard plane due to the propeller only supplying thrust and not enough airflow over the structure/wings to create the necessary lift for flight. Forward acceleration through air would be required to provide the necessary lift.

Does that sum it up?

That being said: Don’t toy/RC planes have different characteristics? The one Nick was using had the propellers pull air directly over a section of the wing which would provide some percentage of lift.

quote Originally posted by mike-ohio: FIEROPHREK/Formula88, I agree that there would not be enough airflow over the airframe/wings on a standard plane due to the propeller only supplying thrust and not enough airflow over the structure/wings to create the necessary lift for flight. Forward acceleration through air would be required to provide the necessary lift. Does that sum it up? That being said: Don’t toy/RC planes have different characteristics? The one Nick was using had the propellers pull air directly over a section of the wing which would provide some percentage of lift.

R/C airplanes behave just as real ones. i don't think Nicks R/C would have enough prop-wash (for lack of a better term) to generate the lift required to lift the whole airplane. It's all about wing loading and airspeed. If you could generate enough airflow from the props it would be possible to lift the aircraft as long as the wing structure could handle those airspeeds .

With enough airspeed and a curved surface you can make anything fly
http://www.youtube.com/watch?v=NL6eiDHISUk

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ARCHIES JUNK IS FASTER THAN SHAUNNA'S JUNK

quote Originally posted by FIEROPHREK: R/C airplanes behave just as real ones. i don't think Nicks R/C would have enough prop-wash (for lack of a better term) to generate the lift required to lift the whole airplane. It's all about wing loading and airspeed. If you could generate enough airflow from the props it would be possible to lift the aircraft as long as the wing structure could handle those airspeeds . With enough airspeed and a curved surface you can make anything fly http://www.youtube.com/watch?v=NL6eiDHISUk

The "propwash" with the RC plane was my question. It does force some air over the wing surface with that specific design. A single propeler in the frot would not.

quote Originally posted by mike-ohio: The "propwash" with the RC plane was my question. It does force some air over the wing surface with that specific design. A single propeler in the frot would not.

If you could get those props to turn really fast and produce alot of "propwash" it might try to lift up. But then your only prblem would be controlling it You need air over your flight controls ie rudder elevator ailerons to manuever.

If propwash created meaningful lift, the plane would hover.
It's forward movement through the air that creates lift.

And some planes even *gasp* have propellers on the wings.

less than 2 days to go.

quote Originally posted by PontiacJ829: less than 2 days to go.

I'll be interested to see the episode and how the do the tests, but regardless of outcome, it won't matter. No one is going to magically start believing something they don't already believe.

quote Originally posted by Formula88: I'll be interested to see the episode and how the do the tests, but regardless of outcome, it won't matter. No one is going to magically start believing something they don't already believe.

They'll end up getting a lot of complaints telling them how they did the test wrong, and I predict that it will end up being in a myths revisited episode later on.

quote Originally posted by Deabionni: Once again, the key element is friction. There's a lot more friction between water and any object placed in that water then there is with an object with wheels placed on tarmac. Take a cheap used Honda for example. A cheap used Honda may make about 100HP, but yet that's still enough power to overcome the rolling resistance and air resistance (land and air friction) for it to be able to reach 100MPH. Now take a lightweight boat and power it with the same Honda engine. Due to the water's friction, that boat will never reach the same 100MPH in water that it can reach on land. Why? Because there's a lot more friction between that boat & water then there is between the car & road/air. (Bad annology, I know, but the best illustration I could come up with between the plane and water, and the plane and road/conveyor belt). In short, the reason the plane was swept downstream is there was a lot more friction between the plane and the moving stream; and your plane's motor just couldn't create enough thrust to overcome that friction.

Ah yes, but if the power can overcome the resistance, that treadmill isnt working as stated.....computerized to counter the thrust/forward motion. You are either slowing the treadmill or increasing your thrust relative to each other.

So if you had water skis on the plane instead of wheels it would make a difference ? If my 40 mph swamp boat had a wing of sufficient size would it fly going into the 40mph current ? (assuming the wing was sized to take off in still water at 40 mph)..?

Roger, you have added an aspect which wasnīt in the original dimension..the conveyor belt is not able to match 'thrust'...it can ONLY match the speed of the wheels of the plane.
Nick

quote Originally posted by rogergarrison: Ah yes, but if the power can overcome the resistance, that treadmill isnt working as stated.....computerized to counter the thrust/forward motion. You are either slowing the treadmill or increasing your thrust relative to each other. So if you had water skis on the plane instead of wheels it would make a difference ? If my 40 mph swamp boat had a wing of sufficient size would it fly going into the 40mph current ? (assuming the wing was sized to take off in still water at 40 mph)..?

every time a plane takes off - it overcomes the resistance - treadmill is irrelavent. still have the wieght of the plane on the wheels. the wheels still spin. and, yes - ski based airplanes can take off against a current of ANY speed, ANY direction - even sideways.

quote Originally posted by rogergarrison: Ah yes, but if the power can overcome the resistance, that treadmill isnt working as stated.....

That's the flaw in this whole scenario. It's physically impossible for the treadmill to impose enough resistance to the plane through it's wheels to keep the plane stationary, and unable to move forward to generate the speed necessary for flight.

*Being a pilot yourself, I would think that you of all people would know this.*

[This message has been edited by Deabionni (edited 01-29-2008).]

Not having ever flown a seaplane myself, Ill take your word on it. Just dont seem possible for it go go against a fast current with no effect. Yes it can with it flowing across, but it does alter the course ie/ crosswind flying or landing.

While model airplanes as a general rule do fly by the same rules as full size (sometimes even better)....all the ones I have experience with take off in a MUCH shorter distance by scale. My 6' F4C can be airbourne in about 30'. By the same scale a full size one cant take off in 250'.

I never said that a treadmill was or wasnt capable of keeping up....the original problem states hypothetically anyway, that its computer controlled to counteract it....at least as its worded to me. It dont say it spins the wheels in the opposite direction.

not saying it has no effect. just saying its not gonna stop the plane. it will still take off at the same speed. it will require more power to achive that speed - but it has the power acheive that speed. doesn't take all that much to push a pair of pontoons thru the water. yes - this is in fact MUCH more work on the plane than the treadmill. but - it'll do it.

quote Originally posted by rogergarrison: I never said that a treadmill was or wasnt capable of keeping up....the original problem states hypothetically anyway, that its computer controlled to counteract it....at least as its worded to me. It dont say it spins the wheels in the opposite direction.

No, it says the plane moves in one direction and the treadmill moves at the same speed as the plane in the opposite direction - always at the exact same speed as the plane.

Look at the question again:

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).
The question is:

Will the plane take off or not?


Break it down to exactly what is stated - make NO assumptions.

The plane moves in one direction.
The conveyor moves in the opposite direction.
Plane speed and conveyor speed are always exactly the same (but in opposite direction).

Now, what does that mean?

If the plane moves - that means the plane, uh, MOVES. If the plane can move, it can take off.
If the conveyor could somehow counter the speed of the plane and keep the plane from moving, that means the plane would not be moving. If the plane is not moving, then neither is the conveyor.

If you think the conveyor can counteract the movement of the plane, that would mean the plane is sitting still with the engine running, and the conveyor is moving backwards, holding the plane in place. If that happened, the plane's speed and the conveyor's speed wouldn't be the same.

Read the actual words - don't try to interpret or reword it. The word "counteract" is nowhere in the question. No where does it say anything about the conveyor stopping the plane or preventing the plane from moving. You're drawing that conclusion on your own.

A lot of people are thinking of the airplane's tires traction the same way they are thinking of tire traction on a car. (which is natural...this is a car forum after all) In cars tire traction IS how a car moves (which is why drag slicks are so wide...more surface area means more traction which equates into faster acceleration), therefore if you had a surface that was moving in the opposite direction equal to the forward movement of the car it wouldn't move. Aircraft move by AIR TRACTION.

An experiment you can try would be to put on a pair of rollerskates and step onto a conveyor belt with a rope strung down the length of it for you to hold on to. No matter how fast the conveyer is going, you would be able to pull yourself hand over hand in the opposite direction. The props on a plane act like hands that "grab" the air and pull it forward. If the prop is pulling the plane forward at 40 miles an hour, and the conveyor is moving in the opposite direction at 40 mph, then the planes tires will be spinning at 80mp, but the forward motion of the plane will still be 40 mph because the props are not being affected in their ability to pull the air.

What a lot of people are not realizing is that on normall take off the tires generate no forward motion whatsoever, so the wheels are designed to make there natural resistance extremely minmal. They have very little surface area, and are well lubricated to spin without resistance. If they weren't designed that way a plane couldn't take off on a normal runway. So, the friction that is going to be generated by the tires spinning twice as fast as the forward motion of the craft will not have any effect on the planes ability to move forward via the prop. The plane will fly.

note: edited for spelling error

[This message has been edited by Flying Pony (edited 01-29-2008).]

I guess we'll see what happens tommorrow and if some fact is missing or not. If it works, why havent airports done away with runways. It has to be a lot cheaper to rig up some kind of powered deal that goes 150 mph than paving 10.000 feet of runway. They could even put big airports in the middle of town as long as they have a clear .flight path out of the buildings.

I see the airplane sitting still idleing and not enough power to move, so treadmill is stopped also. now I add some power and the plane starts pull itself forward at 1..5..10mph and the treadmill reacts by immediately spinning faster as needed to keep it at 1...5...10 mph to keep it in the same place. Thats how come I see the plane staying in the same place. I was never good at thought problems in school either....like Bobs train is going 2 times faster than Jims train and will Bobs train catch him before the next stop.....LOL. I always just use the charts and current weather to determine to take off or not unless its obvious. Cessna on a 11,500 foot runway.... ...ya thatll work.

quote Originally posted by rogergarrison: I guess we'll see what happens tommorrow and if some fact is missing or not. If it works, why havent airports done away with runways. It has to be a lot cheaper to rig up some kind of powered deal that goes 150 mph than paving 10.000 feet of runway. They could even put big airports in the middle of town as long as they have a clear .flight path out of the buildings. I see the airplane sitting still idleing and not enough power to move, so treadmill is stopped also. now I add some power and the plane starts pull itself forward at 1..5..10mph and the treadmill reacts by immediately spinning faster as needed to keep it at 1...5...10 mph to keep it in the same place. Thats how come I see the plane staying in the same place. I was never good at thought problems in school either....like Bobs train is going 2 times faster than Jims train and will Bobs train catch him before the next stop.....LOL. I always just use the charts and current weather to determine to take off or not unless its obvious. Cessna on a 11,500 foot runway.... ...ya thatll work.

"
I see the airplane sitting still idleing and not enough power to move, so treadmill is stopped also. now I add some power and the plane starts pull itself forward at 1..5..10mph and the treadmill reacts by immediately spinning faster as needed to keep it at 1...5...10 mph to keep it in the same place."

This part is accurate up to the point where you say the conveyor keeps the plane in the same place. The plane sits still, engine idling. You throttle up and the plane moves forward. At 10 mph, the conveyor is going 10 mph backwards. We're on the same page so far.

Now, the key is, the plane is still moving 10 mph forward AND the conveyor is going 10 mph backwards. The conveyor didn't slow down the plane. (that's why if you put a speedo on the wheels, it would read 20 mph)

Remember the speed of the plane and conveyor must be equal. If the plane is sitting in the same place, it's speed is 0, and it's speed cannot be equal to the conveyor's.

quote Originally posted by rogergarrison: I guess we'll see what happens tommorrow and if some fact is missing or not. If it works, why havent airports done away with runways. It has to be a lot cheaper to rig up some kind of powered deal that goes 150 mph than paving 10.000 feet of runway. They could even put big airports in the middle of town as long as they have a clear .flight path out of the buildings. I see the airplane sitting still idleing and not enough power to move, so treadmill is stopped also. now I add some power and the plane starts pull itself forward at 1..5..10mph and the treadmill reacts by immediately spinning faster as needed to keep it at 1...5...10 mph to keep it in the same place. Thats how come I see the plane staying in the same place. I was never good at thought problems in school either....like Bobs train is going 2 times faster than Jims train and will Bobs train catch him before the next stop.....LOL. I always just use the charts and current weather to determine to take off or not unless its obvious. Cessna on a 11,500 foot runway.... ...ya thatll work.

1> because planes have passengers, and the take off thrust is already enough to upset some of them. having an aircraft carrier launch would be great for some of us - but, dont think my Mom would approve. and, ya still gotta land these beasts.

2> the treadmill doesnt move the plane. its on free, unpowered wheels, which, thru the magic of technology have these things called bearings to reduce rolling resistance. pull a rug out from under a dolly. yes, there is some interaction, but mostly - the dolly stays. now add the massive thrust of a few jet engines. maybe try it with a hotwheel on a hotwheel track - yank the track out from under it. whatever. the friction is meaningless. especially against the jets. wheels. they roll. just like the plane wont instantly fall from the sky by flying over a backwards running treadmill. or, perhaps, a skateboard, on an airport "moving floor". pull yourself along by the fixed rails - no feet - that'll mess ya up. yes, it sure is easier one way - but, by no means a significant change. wheels & bearings are wonderful things.

quote Originally posted by rogergarrison: If it works, why havent airports done away with runways. It has to be a lot cheaper to rig up some kind of powered deal that goes 150 mph than paving 10.000 feet of runway.

Roger, this comment alone indicates that for whatever reason you still don't grasp the concept.

What happens when you grab a table cloth, on a table, that has a dinner plate sitting on it, and you pull it hard and fast? You get a lesson in the first law of motion. An object at rest will tend to stay at rest. Move the conveyor and the wheels will turn on the plane, unless they are glued to it or the brakes are on.

I forsee a lot of broken plates with this bunch.

quote Originally posted by Formula88: I forsee a lot of broken plates with this bunch.

remember the video camera!!

So....when is it going to be released, this Mythbusters thing? Tomorrow is the 30th January..is it a TV thing, or Internet thing? Or both? I canīt wait!! I took my model plane with me to the Airport to meet Ellie, but couldnīt get to try the experiment again ..but the two I have already done proved it to me conclusively...the PLANE WILL FLY!!! Taddadadadadaaaaaaaaaaaaaaaaaaaaaaaaa!!!!
Nick

[This message has been edited by fierofetish (edited 01-29-2008).]