OK...how about this.

Regardless of whether a wheel is driven through a drivetrain or rotates freely, it covers a given distance per rotation. In this scenario, the distance covered per rotation is reduced to zero because the treadmill moves that distance back as the wheel tries to advance forward. Again, this is true regardless of what's driving the wheel forward.

So the relative forward motion is zero, the relative wind over the wing is zero, airspeed is zero, and your chances of taking off are...you guessed it...zero.

Socal....

You're a smart guy. If you were the outside observer looking down on the experiment in our hypothetical scenario.... (Remember plane and conveyor speed are matched)

What would you see? Describe it.... start to finish.

.......................

Now... it is not a windy day when you are observing this scenario.

Describe the wind condition on the top of the wing of the plane in the scenario. Is the wind blowing hard....

Or is the wind condition almost the same as where you are standing?

They would see the plane take off with a little extra wheelspin due to the conveyor belt.

No, it's not. In the scenario of a freewheeling wheel, what's driving it forward?

Alright. Let me clarify.

Leading up to the hypothetical takeoff...

What do you see as the plane and conveyor are building up speed?

What is the plane's appearance relative to your position?

Ah HA!

No - you ran ZERO MILES.

You stayed in ONE PLACE, and, COVERED NO DISTANCE.

You moved your legs AS THOUGH you had run 4 miles...but, in fact, you did not.

It's a chicken or the egg scenario though.

What we see is dependant on the result of the findings of this question.

An observer would see a large jet on a treadmill type conveyor belt. Initially the plane would not be moving as the wheel movement is being negated by the conveyor.

But as thrust is applied how that overcomes the lack of forward motion is the question here. I believe that wind speed and atmosphere are irrelevant to the plane achieving flight since propultion along with the wing design and purpose are enough to overcome the lack for forward motion.

But a vehicle moving at 200+ MPH without wings is also able to achieve flight. So again: the chicken or the egg?

I still believe that forward motion works in a symbiotic relationship to the method of thrust and wing design but they can also produce flight independant of each other.

There WILL be air moving over the wing, due to the plane moving forward....the wind blowing out THE BACK OF THE ENGINE is pushing it forwards THROUGH THE AIR.

The Belt does not matter, or change the air around the plane in ay way whatso ever.

How does a plane move through the air? Its engines push the air through them, right?

How does a car move? Its powered wheels push the ground out from under it, right?

Now, here's a trick question: How does a car move through the air? Hint: as long as the car's tires are on the ground, it moves forward.

Well, if the wheel moves, something is causing that, correct? It could be a guy pulling his kid in a Radio Flyer or a soap box derby racer coasting, but if the wheel is moving, it is covering a given distance per rotation. If that distance is negated by a moving surface underneath that moves an equal distance in the opposite direction, the vehicle will not move relative to its surroundings.

No, I covered four miles of the treadmill.

Again - what is the speed relative to in the question?

If I drive my car for four miles on a dyno - do you really think I can claim it has no miles on it if I resold it? No.

So, you're saying that a guy pulling his kid in a radio flyer will be unable to keep pulling the wagon if the wagon suddenly rolls over a conveyor belt?

If air speed over the wings is required for flight then why have F1 and Indy cars been airborne and why is a primary concern for land speed attempts maintaining enough downforce at speed to prevent the vehicle from achieving flight.

No, I'm saying that if the conveyor belt it's on speeds up to match how hard he pulls, the wagon will not move forward, assuming it's on the belt and he isn't.

The question is whether the same amount of wind and air move over the wings as does in a conventional takeoff.

That is the key and the only thing that needs focusing.

Quote:

I still believe that forward motion works in a symbiotic relationship to the method of thrust and wing design but they can also produce flight independant of each other.

Remember the four forces required for flight.

We know we have three.

The only variable yet to be determined is the air at a certain point in time moving over the wing and body of the plane.

If it is even remotely less than that for a conventional takeoff....

Will this plane in the scenario achieve takeoff and flight?

The bearings in the wheels would fry and the whole thing would crash before it took off.

Or the tread mill would snap and fly through the cockpit effectively killing pilot and any chance the plane had to take off.

BlueSky-

Here's another scenario.

Let's say I'm riding my bike on a treadmill. No matter how fast I pedal, the treadmill keeps up, so I don't roll off the treadmill.

Now, let's say that you come long next to me and grab my arm and start pulling me forward. Will you be able to pull me off the treadmill?

No because , as is the case with the plane, you are not being self propelled. (nor are the wheels) You are being propelled by an external force (the jet engines or whoever is pulling you) and the conveyor is still mathing whatever percieved forward progress you are making.

Even if a team of clydsdales were you be pulling you, you could not be pulled off of the treadmill.

Airflow over a wing allows aircraft to achieve CONTROLLED flight. The vehicles you mentioned do not "fly" per se, they are propelled into the air by various aerodynamic forces that temporarily provide enough lift to elevate them off the ground.

I can see where it would take off and I can see where it would not there is just not enough information to say yes or no.

Simply because there were no limits put on the treadmill? And are the wheels totally magically not creating drag? And do the engines have enough power to overcome the weight of the plane dragging on the treadmill?

Hell if there were no limits put on the friction of the wheels on the ground and engines had insane power then yes I believe it could take off.

But this is a fictional situatoin so who is to say there are limits.

socalpunx- whoa, that's some crazy logic.

OK, let's take this to the off-road arena.

Let's say I'm stuck on an uphill slope in my 4x4. No matter how much gas I give it, gravel/rocks/scree keep rolling under my tires so I can't move forward. (Let's assume that I'm not digging any holes and that there's an infinite supply of gravel to keep me slipping.)

I call up to you in your X and tell you I'll give you a case of beer for a winch up the hill. Can you pull my truck up?

Further to the above:

Flight:



Not flight:

But your next example has definable factors. Traction, the type of along with the weight of your vehicle all come into play and we can determine the best possible way to pull you up the hill because the hill you are trying to drive up is not moving in the opposite direction as your attempt at movement.

Your treadmill is set up to negate the amound of force you apply towards forward progress therefore even if you were being pulled by that car I posted a picture of (assuming that your feet could move at three hundred MPH or you had wheels instead of feet) you would still be riding the treadmill to nowhere.

Matching exact speed is matching exact speed regardless of whether the force applied is internal or external. Remember the wheels of the plane has no source of power themselves. Their only movement is as the result of an external force.

Did Mr. Stewart "take off" though?

The question is not to consider the quality of the flight or the length of flight but if or not the plane can "take off".