Yeah but if the plane wheels are movie 100 mph to the east and the coveter belt is movie 100mph to the west. There is not forward motion. Unless you add a big fan that will give you enough air to make lift. But if the body of the plane is standing in one portion how is the plane going to fly. I have not read the whole 10 or what ever pages but how is the plane going to get lift?

BTW: I am the master of page 11.

[This message has been edited by sonic50 (edited 04-07-2006).]

quote Originally posted by jstricker: This is where those that think it will not fly are missing the boat, based on the original question.

John, it's absolutely amazing at this point of discussion (11 pages! ) how many people are still simply not reading (and comprehending) the "original question".

I gave my reasons for initially being wrong at the top of page 7, but after all this time (and guidance), nobody else deserves to be excused.

[EDIT] Had to change "10 pages" to the now current "11 pages".

[This message has been edited by Patrick (edited 04-07-2006).]

quote Originally posted by Patrick: Come on Johnny, you're representing Canada here. Smarten up!

I don't even remember the original question, it was ages ago.. I recall it being that the conveyor will move backwards at any speed necessary to slow the plane down, hence my 'infinity/weight" theory, but, I misread. Apologies.

quote Originally posted by JohnnyK: ... but, I misread.

Right on! We've reclaimed yet another lost soul from the morass.

I'm afraid sonic50 may however be forever lost.

quote Originally posted by Patrick: Right on! We've reclaimed yet another lost soul from the morass. I'm afraid sonic50 may however be forever lost.

After reading his reply at the top of this page--I tend to agree with you.

quote Yeah but if the plane wheels are movie 100 mph to the east and the coveter belt is movie 100mph to the west. There is not forward motion

Forget the wheels. What are the wings doing? What is the fuselage doing? See the little faces in the little windows? See their little hands waving? They are waving bye bye as the plane moves on down the conveyor to takeoff. Wave bye to Sonic everyone-he's standing there wondering how the plane took off without him.

quote Originally posted by sonic50: Yeah but if the plane wheels are movie 100 mph to the east and the coveter belt is movie 100mph to the west. There is not forward motion. Unless you add a big fan that will give you enough air to make lift. But if the body of the plane is standing in one portion how is the plane going to fly. I have not read the whole 10 or what ever pages but how is the plane going to get lift?

But that's the point, the fuselage is moving. The wheels are just spinning rediculo-fast. The wheels are free to spin on bearings end of story. It's not a car, the motive force isn't provided by a transmission to the wheels, it's provided by an aerodynamic reaction with the air.

quote Originally posted by sonic50: Yeah but if the plane wheels are movie 100 mph to the east and the coveter belt is movie 100mph to the west. There is not forward motion.

Again, you're making assumptions about things that aren't stated and that's where you're screwing up.

Who says the wheels are going the same speed as the conveyor? Do you not agree that if the plane is going 100 mph East and the conveyor is going 100 mph West that the wheels must be going 200 mph?

So, what mechanism is keeping the wheels turning the same speed as the conveyor? There isn't one. The wheels are free to accelerate unless you put the brakes on. In the absence of brakes, the plane moves in one direction, the conveyor in the other, and the wheels turn at their combined speed.

OK, then the plane will fly

quote Originally posted by sonic50: OK, then the plane will fly

I dunno, you're not saying that with too much conviction.

quote Originally posted by maryjane: See the little faces in the little windows? See their little hands waving? They are waving bye bye as the plane moves on down the conveyor to takeoff. Wave bye to Sonic everyone-he's standing there wondering how the plane took off without him.

NO!! let me on! The plane will fly, the plane will fly the people over at ppf tell me! I want to come.

LOL...

Lift is based on AIRSPEED not ground speed. Other than a little extra wheel friction the conveyer belt has little effect on the plane. It may actually help develop a bit of a groung effect...

A plane flying at 45mph airspeed into a 50mph headwind will still fly but the groundspeed will be -5mph. The same plane flying 45mph airspeed with a tailwind of 50mph will fly with a groundspeed of +95mph. Propellers/jets push against the air not the ground for takeoff and flying - wheels provide no thrust they keep planes from having to skid across the ground until proper airspeed is reached.

quote Originally posted by Sjuice: Propellers/jets push against the air not the ground for takeoff and flying ....

Aaaarrrrgggghhhh!!! Yet another misunderstanding!

Propellers/jets work by accelerating the air that passes through them. It's the change in momentum of the air mass that results in thrust.

We really should have saved this topic for another class.

Marvin,

So if the LongEZ is moving forward at 70 knots, and the belt is moving backwards at 70 knots, and you're sanding the wing fillets micro, will the dust still get in every pore of your body??

John Stricker

(Marvin knows what I mean)

quote Originally posted by Marvin McInnis: Aaaarrrrgggghhhh!!! Yet another misunderstanding! Propellers/jets work by accelerating the air that passes through them. It's the change in momentum of the air mass that results in thrust. We really should have saved this topic for another class.

quote Originally posted by jstricker: So if the LongEZ is moving forward at 70 knots, and the belt is moving backwards at 70 knots, and you're sanding the wing fillets micro, will the dust still get in every pore of your body??

[IRONY]I'm not so sure about the airplane anymore,[/IRONY] but I guarantee that the dust absolutely, positively will fly! (Now where did I put that dust mask? Cough, cough, ....)

[This message has been edited by Marvin McInnis (edited 04-08-2006).]

But seriously, to set my mind at ease, can we at least agree if the conveyor can 'accelerate up to infinity', and the plane does in fact have mass and bearings indeed have friction, that it won't be moving anywhere?

We could also agree that space aliens could hold the plane motionless with their ray gun, but that wasn't part of the original scenario either.

ok let me put it this way. The conveyor belt moves as fast as the forward motion of the plane, that is what the problem states. So at takeoff the belt should really only be moving at 65mph (for a cessna) in the opposite direction, so that would 130mph total that the wheels have to handle. That speed doesn't create enough friction to keep the plane motionless. Therefore the thrust will overcome that and the plane will fly. Thats it in a nutshell

I think this thread now has "Grandfathers" status- Here is some added confusion to the senerio If the convayer matches the forwqard speed of the airplane that would mandate that the plane would have effective zero forward velocity therefore the convayer would have zero rearward velocity and would be stopped.

quote Originally posted by JohnnyK: But seriously, to set my mind at ease, can we at least agree if the conveyor can 'accelerate up to infinity', and the plane does in fact have mass and bearings indeed have friction, that it won't be moving anywhere?

Good morning Johnny.
Are you saying we are going to throw out the "matches the forward speed of the plane" bit?
OK. If so:
An interesting scenario, but here is something to consider. Most airplanes-short those heavy haulers with huge payload capacities--will move fwd even at idle, as soon as the brake is released and chocks pulled. This is especially true with prop jobs. If you are talking about a loaded 747 or C5-that's one thing, but if we are using a small Cessna--that may be another. An airplane by design is made from very light weight materials--as you probably well know better than I. A conveyor, in comparison--is not. To be wide enough to support the plane, the rollers that drive and support the belt will have to be very wide, which equals heavy. So, you need to re-write your scenario to include a wireless dual remote and sensing for both plane, and conveyor, and you should specify that the conveyor is ultra lightweight material. I say this, because I work with belt driven conveyors every day, and in this scenario, the huge mass of the conveyor's rollers and belt would cause it to self destrutct long before the landing gear on the plane did. Instantinputs is essential as well. IE if the acceleration of the plane is increased, the conveyor is instantaneously also equally increased as it's recieving the same inputs from the dual output remote control system. No lag time--and that is important. There can be no seesaw effect at all. No"Catch up" on the conveyor's part of the experiment. If there is a lag time, the plane will move fwd at least in little spurts, till the convey or catches up. To be an accurate experiment tho, some provisos really should be edited into your paragraph above:

1. The conveyor and it's rollers/bearings/belt assembly must also have mass. Fair is fair.
2. The wheel bearings and tires on the aircraft can match the equivilent rolling rpm of the conveyor's supporting rollers.-ie, the wheels of the landing gear can also rotate up to infinity without self destructing.
3. The planes propulsion system must be capable of infinite HP outputs-same as the magical conveyor.
4. And, you have to build everything in this scenario from materials impervious to heat. The friction of the air molecules in contact with belt moving at infinite speeds will cause heat usually only seen when an object reenters the atmosphere from space. Space shuttle's heatshield glows red hot-and meteors burn completely up more times than not.

Now, we have all the parameters equal for both primary pieces of equipment in the experiment. Plane and conveyor can do anything without material failure.

IMO I believe the plane will still take off. That's just my gut take on it, tho I can't explain it very well. For one thing, the weight of the plane, being distributed betwixt main and front landing gear, (usually 3 sets of wheels) and the small footprint of contact between the tire and conveyor makes the plane lighter in comparison to the conveyor's effect on the plane. Even at insane speeds, the plane's propulsion system will begin to 'drag' the landing gear-regardless of the belt's velocity. I believe this may happen even if you did not give the plane's propulsion system, wheel bearings and tires unlimited durability.

Here is what the pea sized science section of my brain says will happen regardless:

The plane will still take off. At infinity, ( or actually before-since we really have no concept of infinity) the rearward movement of the conveyor's belt will begin to move air along with it. (It will create a head wind for the plane.) This air is passing over/under the plane's wings, inducing lift, lightening the load on the plane's landing gear. Air has mass too, and because of it, friction between the air molecules and the conveyor's belt will cause the air molecules to be drug rearward-once the conveyor reaches extremely high speeds. It may be difficult to imagine this air movement, but we are talking hypothetically high speeds here. Once the air mass reaches the headwind speed that this particular plane requires to lift-it's done. The landing gear loses contact with the belt and off it goes into the proverbial wild blue yonder.

Now, we could negate this by saying we will put the whole experiment into a huge vacum chamber, but then, the experiment is fouled, because naturally, the plane flies due to what we just completely sucked out of the chamber--air/wings combo. It cannot take off under any circumstances in this case. Like wings on a spacecraft--useless.

[This message has been edited by maryjane (edited 04-08-2006).]

quote Originally posted by maryjane: At infinity, ( or actually before-since we really have no concept of infinity) ...

We don't actually have to worry about infinite velocities. The speed limit in the universe is the speed of light ... and the laws of physics, unlike some traffic laws, are rigidly enforced. Unfortunately, even attaining the speed of light has its problems, since it will require almost an infinite amount of energy ... certainly far more than the plane's fuel tanks can hold.

But the conclusion remains the same: Even at the speed of light, the airplane will fly!!!
(Although no one yet has answered the question, "What is the airspeed velocity of an unladen swallow?")

[This message has been edited by Marvin McInnis (edited 04-08-2006).]

Oh, I agree with you Marvin, just don't have the technical experience or knowledge to explain it very well. I really can see no scenario where the plane will not fly as long as it has the abilty to roll. Even then, it may be able to drag a locked up set of gear, if it has the power to do so.

I was just running Johnny's set of principles thru my little mind, since the initial subject seems to be pretty well gone over countless times.

quote Originally posted by maryjane: Oh, I agree with you Marvin, just don't have the technical experience or knowledge to explain it very well.

But you reached the right conclusion anyway, using logic and what you do know about mechanics, and you explained it well enough. It also didn't hurt that you read the original statement of the problem carefully and understood it correctly, and you even proposed a real-world experiment that would validate (or invalidate) your conclusion. I also admire those who originally reached the wrong conclusion but thought some more about it, listened to others, and changed their answer; they are the brave ones here.

Anyway ... this topic has long since degenerated into a parody of a Monty Python skit, and I just can't keep myself from adding a line here and there.

And now for something completely different: I'm actually a little surprised that no one (including any of the engineering types) has pointed out that although the airplane will undoubtedly fly, its acceleration on the moving belt will be slightly slower than on a stationary runway ... due to the rotational inertia of the wheels and tires, and the fact that at any point they will have to be turning exactly twice as fast on the moving belt as they would be on a fixed runway. Discuss!

[This message has been edited by Marvin McInnis (edited 04-08-2006).]