Will it take off?

[TraceZ]

Well that gets back to my first post. Is the plane moving or not. The question is contradicting itself and therefore invalid.

read the question again. it does not specifcally say the plane will not be able to move forward.

[Steel2686]

read the question again. it does not specifcally say the plane will not be able to move forward.

I think this is where the confusion is coming from. We need a clearer explanation of the plane's movement or non-movement.

[DierDesire824]

Trace has the idea

it doesnt matter what the wheells are doing as told in the original ? they do not matter because they are not the driving force the point here is the Prop is the driving force

[Jeff_in_Atl]

I still can't see how the plane would generate airlift when it's remaining in the same spot. If I am to understand this correctly, let's put this in perspective.

The plane is on a giant treadmill. The treadmill is moving at a speed in order to keep the plane in place. There is a person standing next to this giant treadmill, but not on the belt. Is the plane moving past this person, or is it staying in the same position? How can air be generated from this?

If you assume the plane is moving then the treadmill is really not part of the equation as the speed of the plane is derived from the propeller not the wheels. If this were a car accelerating on a treadmill the car would remain stationary. Since the plane is driven by thrust not from driving a wheel the treadmill plays no part in the equation (except drag from the wheels which is no where near enough to keep the plane from moving.)

[Jeff_in_Atl]

read the question again. it does not specifcally say the plane will not be able to move forward.

I have several times. It says...

A plane is standing on a runway ...

It says the plane is "standing" which implies it does not move.

Now saying that I think what they mean is that it is moving not "standing" but using that word is confusing. The question is poorly written. If the plane is moving you are correct.

[Steel2686]

Yeah... agreed completely. If the question were worded "Would the treadmill's speed keep the plane from moving forward", the answer is no. Unfortunately, it was a bit confusing.

[TraceZ]

I have several times. It says...

It says the plane is "standing" which implies it does not move.

Now saying that I think what they mean is that it is moving not "standing" but using that word is confusing. The question is poorly written. If the plane is moving you are correct.

At the beginning of the experiment the plane is standing.

but...
As soon as the pilot hits the throttle, it begins moving and there is nothing that the runway can do to stop it.

[Trash man]

im too lazy to read the post right now, but the plane will take off, the wheels have nothing to do with thrust, the thrust propellles the plan forward. as for the ? it standing then as soon as it begins to move, the treadmill moves to match the speed.

[fastTa]

Jeff and Tracy, you guys went off on your own tangent and confused the theory of the orginal post with your own. The orginal question mentioned nothing about simulation of air velocity to assist in lift. And since the moving runway has esentially no effect on the air immediately surrounding the aircraft, the moving runway is not only counter-productive, it is irrelavant to the meausure of the ability of the aircraft to produce lift. It merely questioned whether or not a moving runway (as opposed to a stationary runway) could provide an aircraft the capacity to fly. The answer is....IT CANNOT.

I never EVER said that it was not possible for an aircraft to move forward with a conveyor belt type runway that is moving in the opposite direction.

The moving runway does not move the air guys....cmon think bigger. It is a physical improbability.

[fastTa]

I see what's going on here now. Some are arguing that it can never take off period, while others are arguing that it cannot take off while standing still.

LOL, of course the plane can eventually take off, but it would take more double the energy(thrust) to do so because of the added friction of the oppositely moving runway.

The only thing that matters here....and I'll say it again...is the air velocity over the wings and body. The thrust DOES NOT directly provide that. Only aircraft velocity relative to the ground (NOT the runway) provides that.

[fastTa]

Well that gets back to my first post. Is the plane moving or not. The question is contradicting itself and therefore invalid.

I agree that the question is not very specific. I think it is oppurtunistically malicious just to create a thread of arguments.

[TraceZ]

LOL, of course the plane can eventually take off, but it would take more double the energy(thrust) to do so because of the added friction of the oppositely moving runway..

Actually, the added friction is almost not noticable. Very small. The wheels of an airplane spinning make very little friction. The added RPMs in the wheels from the moving runway would have almost no effect on the airplanes ability to gain airspeed.

When you are on a jet and it touches down do you feel the plane immediately slow way down from the drag of the wheels?? .. . no...

The plane slows down when the pilot reverses thrust and hits the brakes. If there were no attempt made to hit the brakes, the plane would coast for quite a long ways because there is very little friction in the wheels without the brakes on.

[Jeff_in_Atl]

Originally Posted by fastTA
...It merely questioned whether or not a moving runway (as opposed to a stationary runway) could provide an aircraft the capacity to fly. The answer is....IT CANNOT.

Uhhh, I don't know where you got that idea but the question is whether the plane can take off or not. It does not ask whther it "could provide an aircraft the capacity to fly. "

Originally Posted by 88bird5spd
The question is:

Will the plane take off or not? Will it be able to run up and take off?

[2Fbodcru]

This reminds me of a Nascar race ( I think it was Nascar), back in the early Eighties. This was the first race with them using the new downsized cars, that were required to be downsized due to the oil crises at the time. All of the Grand Prix’s, Lemans, and whatever else they were using at the time, were very boxy and not aerodynamic at all, as far as the kind of aerodynamics that are required to push a car down closer to the road. As the race got underway, cars started actually flying into the air and crashing, because of the lightweight and non-aerodynamic characteristics of the cars.
Now in a theoretical race:
If they had been driving on a big conveyor and they had all been going the same speed, and the conveyor matched the speed exactly, going in the opposite direction, there is no way that any of those cars would have flown up into the air, unless some strong hurricane force wind came along and lifted them off of the track. It was the air resistance combined with the forward motion, that caused the cars to “fly” - without the air resistance, the cars would have stayed on the ground...right?

[2Fbodcru]

I agree that the question is not very specific. I think it is oppurtunistically malicious just to create a thread of arguments.

It could be - there is a technique, that I can't remember the name of at the moment, that is taught in some college classes. You simply throw a theoretical question out there for discussion, and arguments begin to erupt to try to argue it to be true, and of course on the other side, to argue that it is untrue.