Debate: Will this plane take off?

[RandyA]

I think most of us assumed that the runway was short. I don't think a video is necessary to prove your point. i think most of us can use our imagination.

Everyone is focusing on the engines providing thrust separate from the wheels, but on the ground the wheels turning against the ground is what allows the plane to move fast enough to attain the speed to achieve lift.

Busted this one above. The wheels move as a result of being in contact with the ground. I'll ask it again, how would a plane fly in the air without the wheels touching the ground?

Thrust. Lift. Forward motion. Flying above stall speed.

without the wheels how would a plane that weighs 399,000lbs,(Standard operating Weight) even move on a "normal" runway. Not to mention that the bottom of the plane is not the best platform to launch from www.airliners.net/open.file?id=116440&size=L&width=800&height=552&sok=&photo_nr= From the looks of the undercarriage it looks like it would just roll over on one of its wings, without the wheels. making launch absolutely impossible

[Jackson]

randya said:

Busted this one above. The wheels move as a result of being in contact with the ground. I'll ask it again, how would a plane fly in the air without the wheels touching the ground?

Thrust. Lift. Forward motion. Flying above stall speed.

without the wheels how would a plane that weighs 399,000lbs,(Standard operating Weight) even move on a "normal" runway. Not to mention that the bottom of the plane is not the best platform to launch from www.airliners.net/open.file?id=116440&size=L&width=800&height=552&sok=&photo_nr= From the looks of the undercarriage it looks like it would just roll over on one of its wings, without the wheels. making launch absolutely impossible

I guess I poorly stated that above statement. <-- Just like that one.

What I meant is that people are saying that the wheels allow it to move forward and I was trying to counter that with in the air there are no wheels touching the ground yet it moves forward so the wheels are not providing the forward motion.

Without wheels a plane cannot take off because the force of friction is too great. The wheels reduce friction allowing it too take off on a normal runway. The treadmill/conveyor just doubles the speed at which the wheels are turning. This adds a slight amount of additional friction but not enough to prevent the jets from moving the plane forward fast enough to attain a proper airspeed to take off.

[firemedic]

I see all points. However, If a man screws up and there isn't a women there to tell him so.... Is he still wrong?

I think yes on the plane. When can we know the answer?

[Kreeper X]

a5pballer1337 said:

A plane (747 passenger jet) is sitting on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the planes speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

Here is the part of the question that is in doubt.

The "Riddle" says that the conveyor tracks THE PLANE, not the wheels, and matches the forward speed of THE PLANE with it's own backward motion exactly.

As the riddle is written, the conveyor is matching any forward motion of the airplane regardless of it's air speed or the wheels on the ground. Since the forward speed of the plane is tracked exactly, it is negated by the conveyor belt and the plane remains stationary.

Since the plane isn't actually moving in the air, then there is no way for lift to be generated by the wings. Therefore I stand by my answer that the plane will not lift off.

[Vashthestampede]

kreeperx said:

a5pballer1337 said:

A plane (747 passenger jet) is sitting on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the planes speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

Here is the part of the question that is in doubt.

The "Riddle" says that the conveyor tracks THE PLANE, not the wheels, and matches the forward speed of THE PLANE with it's own backward motion exactly.

As the riddle is written, the conveyor is matching any forward motion of the airplane regardless of it's air speed or the wheels on the ground. Since the forward speed of the plane is tracked exactly, it is negated by the conveyor belt and the plane remains stationary.

Since the plane isn't actually moving in the air, then there is no way for lift to be generated by the wings. Therefore I stand by my answer that the plane will not lift off.

But it says in the opposite direction which means its only interaction with the plane is through the wheels, the same wheels that are unable to prevent the plane's takeoff.

[Kreeper X]

So the idea is that the forward motion of the wheels and the reverse motion of the conveyor create a "zero-point" platform on which forward motion is generated regardless of speed of the wheels or the conveyor belt? In other words the equal motions cancel each other out and as such the plane will move forward and thus can achieve liftoff?

My problem with this scenario is that while the wheels are unable to prevent the plane from taking off, the wheels would have to spin faster than the backward motion of the treadmill which is impossible because the faster the plane moves forward, the faster wheels move, but the conveyor belt also accelerates. I still cannot see a way that the plane make ANY forward motion at all...

Even with the jets providing thrust, the plane cannot go anywhere without that forward motion at the wheels. While the flight of that plane is independent of the wheels, if the plane itself cannot move forward, then the wings cannot generate lift.

The Rocket car on ice argument doesn't work for me because we're talking about a zero-friction surface that can allow for motion regardless of the motion of the wheels on the car and because the ice is providing no equal and opposite interaction with the wheels on the car.

With the conveyor belt, there is friction created between the wheels and the belt, meaning that for the plane to move forward at all the wheels are needed to provide the platform for motion. If you take a jumbo jet and throttle it up with the breaks on, it won't go anywhere. The same principle applies here. If the plane was on an Ice runway with the breaks on and it throttles up, it may well take off...

The treadmill arguement doesn't make much sence either. The arguement is faulty in that there is a difference in being pulled along against a conveyor belt and being pushed on that conveyor belt. A more appropriate scenario is standing on a skateboard on a tread mill and pushing off against someone behind you while the treadmill is programed to match your forward speed with equal reverse speed.

As an example, take an Icy hill and two cars, one front-wheel drive and one rear-wheel drive. The front wheel drive car is pulling the rest of the car along up the icy hill, while the rear wheel drive car is pushing it along. Which will actually make it?

[flyboy]

If you allow the treadmill speed to accelerate beyond Vlof (lift of speed) (or even maintain v1 for an extended length of time) eventually the tires are going to blow and probably the undercarriage collapse and you have a nice mess on your hands ;D

If the aircraft has no forward motion there is no lift being generated irreguardless of thrust.

[ferkjace]

But there will be forward motion

It would be easy enough to prove, all you need to prove is the plane can accieve forward velocity...

Someone get an R/C plane and a convayor

Heck, a rubber band plane and a piece of paper being pulled...

It will fly...

I'm trying to think of a parallel to when they land and use the thrust reversal things.

[Gen]

Maybe we can simplify this a little. Instead of the 747, how about airplane X.

Lets get rid of some variables for this discussion.

1) Airplane X needs to achieve 100MPH airspeed over the wings to lift off.
2) The runway/treadmill is endless
3) There is no friction between the tires and treadmill
4) There is no wheel bearing friction
5) The tires will never blow up.

As the plane increases speed forward from the thrust of the engine, the endless treadmill begins to move in the other direction. The plane hits 50mph forward airspeed, which is the same 50mph forward ground speed relative to the ground OTHER than the endless runway/treadmill. But since the treadmill is moving in the opposite direction and equal speed. The wheels on the plane register 100mph groundspeed. Once the plane hits 100mph airspeed. The treadmill is moving at 100 mph in the opposite direction. But the wheels are now registering 200 mph. The plane can still lift off because it has reached 100 mph over the wings. The treadmill can still travel in the opposite direction of the plane at an equal speed. The wheels on the plane are traveling twice as fast as normal.

Did I expain that well? Or did I just confuse everyone more?

[retardedfury2p1]

OK, this whole thing is making my brain hurt, and causing me to question 4 years of aviation and physics learning I had to go through. ME NO LIKEY! Explain to me how this airplane is any different from a car on a dyno? The car may be saying it's going 100mph, but since the dyno rolls the other way, the car goes nowhere. If the plane is basically in the same situation, it can't move, therefore no air moves over the airfoil, and no lift is generated. Someone just give the friggin' answer in a way I can understand please!? I just fly them and tell them what to do. Getting this crazy hypothetical math stuff involved is like heresy to me.

David

[Gen]

retardedfury2p1 said:

Explain to me how this airplane is any different from a car on a dyno? The car may be saying it's going 100mph, but since the dyno rolls the other way, the car goes nowhere.

David

Because a car achieves its forward momentum from the wheels themselves. While a plane is pushed forward by the engine that is attached to the fuselage or lifting surfaces, not through the wheels.

[GRRWingNut]

Okay, guys, here we go...

If a paintball is sitting in the breech, and the barrel is a conveyor belt that was somehow set up to move opposite the direction of the paintball, when you pull the trigger, would the paintball leave the barrel?

The propeller(or turbine) is the thing that provides the thrust for the aircraft. This source of thrust acts on the air around the aircraft, not the runway, like a car.

Therefore, the wheels have no effect on the acceleration of said aircraft.

Therefore, the conveyor would have no effect on the acceleration of said aircraft.

Groundspeed does not matter, only airspeed.

Let's say that this aircraft needs to achieve 100 mph before it can lift off.

Let's pretend that this aircraft is taking off into a headwind of 50 mph. It will still take off at 100 mph airspeed. But because it started with a 50 mph headwind, it only needs another 50 mph airspeed to be at 100 mph. Therefore, the aircraft can take off with a groundspeed of 50 mph

This same airplane, again lifting off at 100 mph, takes off again, this time into a tailwind of 50 mph. This time, it needs to accelerate to 50 mph to get an airspeed of 0, and then accelerate more to an airspeed of 100, making it's groundspeed 150 mph.

So if this aircraft was on some sort of conveyor, this conveyor would only affect groundspeed. Airspeed is a direct result of thrust, and therefore not affected by groundspeed.

jj

[Kreeper X]

grrwingnut said:

The propeller(or turbine) is the thing that provides the thrust for the aircraft. This source of thrust acts on the air around the aircraft, not the runway, like a car.

Therefore, the wheels have no effect on the acceleration of said aircraft.

Not so. Like I said before, put the brakes on and throttle up and there is no forward accelleration of the air craft at all.

The wheels don't provide motion for the plane, but they are a very important piece of the puzzle.

Therefore, the conveyor would have no effect on the acceleration of said aircraft.

Groundspeed does not matter, only airspeed.

Now this I agree with. The problem is weither or not forward motion can be achieved when the forward motion at the wheels is being counter balance not by the speed of the wheels but rather by the forward speed of the aircraft.

My point of contention is that I still don't see how the aircraft moves forward when it HAS TO DO SO on the wheels that are being negated by the treadmill...

Of course, I'm probably wrong.

[MerrSonn]

kreeperx said:

My point of contention is that I still don't see how the aircraft moves forward when it HAS TO DO SO on the wheels that are being negated by the treadmill...

Of course, I'm probably wrong.

The thing is that the conveyor matches the speed of the plane itself, not the wheels. The plane will move forward due to the thrust of the engines, and the wheels will effectively move twice as fast as they would if the plane was on a normal runway.

Edit: Just got confirmation from my physics teacher.

[Jackson]

kreeperx said:

grrwingnut said:

The propeller(or turbine) is the thing that provides the thrust for the aircraft. This source of thrust acts on the air around the aircraft, not the runway, like a car.

Therefore, the wheels have no effect on the acceleration of said aircraft.

Not so. Like I said before, put the brakes on and throttle up and there is no forward accelleration of the air craft at all.

But with the conveyor, the wheels are still allowed to rotate. The brakes don't allow them to.

PS: Also confirmed this with my physics teacher. He says that the plane will take off.