quote:

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Also, don't really understand whoever said Bernoulli's Principle isn't why aircraft fly. Change in momentum of the air describes the same thing...

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But saying that the Lower pressure on top of the wing coupled with higher pressure on the bottom of the wing is what causes lift is wrong.

check that...

it's a definite maybe.

it will fly

yup!>..i think thats what everyone finally agreed about

has your thread broken the record yet @ video?

No. Im thinking I should have posted this in the nerdery.

ah!...post them the link and invite them over here

idiots. the plane will fly.


bernoulli's principle isn't why airplanes fly. it's why your shower curtain attacks your legs while you're taking a shower, but it isnt what makes airplanes fly.

It all depends on your frame of reference. We're all moving around the Sun at about 67,000 miles an hour.

The moving runway basically is set up to counteract the thrust of the engines. So while the instruments in the plane will read that it is gaining speed and the engines will be pouring out thrust, it won't be going anywhere outside the reference on the plane a.k.a. it'll be sitting at the head of the runway.

So, no, it won't take off.

It's not really that simple:

http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/airfoil.html#c1

No

I'm going to eat crow. I'm a retard. It will fly.

No it won't.

It will take off.
The wheels are irrelevant.

Uh, the wheels are very relevant.

quote:

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But saying that the Lower pressure on top of the wing coupled with higher pressure on the bottom of the wing is what causes lift is wrong.

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Is anyone really advocating this position?

quote:

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It's not really that simple

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Yeah, it really is. No movement in reference to the everything outside the plane and runway equals no airflow, which means no lift, which means no flight.

The plane must move down the runway to create airflow. If this runway works successfully to counteract the thrust of the engines, then it doesn't move and doesn't fly.

I'm pretty sure on this one. Not just because I answered, but I also forwarded the question to a retired Air Force pilot and instructor (and an Ag) and he said that if the runway works as described, then it wouldn't fly.

It flys.

It doesn't.

My it's not that simple comment was intended to fuel the Bernoulli argument.

Make no mistake; the plane would fly.

No airflow = No flight.

Chipotle

Flys

I'll take the Air Force pilot's word over yours, unless you want to post some creditials.

What would keep the plane from moving forward?

I don't have credentials. It's all ball bearings these days. Maybe you need a refresher course.

Aircraft do not derive their forward thrust at their wheels. If a plane is traveling at 250mph on a conveyor belt, and the conveyor belt is moving at 250mph in the opposite direction, the aircraft is still moving at 250mph. The wheels are spinning at 500mph. That's the only difference.

Kramer you are a moron....the runway does not work as it IMPLIES. The runway does not keep the plane from moving down it......if it did, then obviously the plane would not fly.

My hunch is that you didn't explain the original question right to Colonel Sanders.

This is where you went wrong:

quote:

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The moving runway basically is set up to counteract the thrust of the engines.

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The runway only moves the wheels. Airplanes' wheels do not supply the thrust towards takeoff.

MY GOD IIIHORN WHY DID YOU TTT THIS AGAIN

weight(gravity), lift, thrust, drag affect flight.

no lift, no flight

hth

quote:

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Aircraft do not derive their forward thrust at their wheels. If a plane is traveling at 250mph on a conveyor belt, and the conveyor belt is moving at 250mph in the opposite direction, the aircraft is still moving at 250mph. The wheels are spinning at 500mph. That's the only difference.

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This means it flys, it is still moving forward and would have airflow and fly


If the question had said that the belt couteracted ALL forward thrust and the plane sat STATIONARY on the belt with full thrust on the engine and the wheels spinning backwards to make this happen somehow it WOULD NOT take off.

The airplain would fly.

Think of this......Imagine the situation described in the thread, a plane on a moving runway. Now, attach a rope or cable to the front of the plane holding it in place while the runway/conveyor is moving backwards. The force that the rope or cable has to exert to hold the plane in place is the force that the engines of the plane need put out to start movement....from this point in the process on, it all depends on the assumption that the wheels of the plane exert the same retarding frictional force wheither they are rotating at 2 mph or 300mph.....usually the force needed to start motion and therefore overcome the initial friction is more than the force needed to overcome friction after the process is started.

Hope this makes sense. I am an Engineer not a writer.

Let me break this down for you the way it was told to me:

This is a very simplistic question with LOTS of variables missing, but we'll approach this from a theoretical standpoint.

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A plane is standing on a movable runway(something like a conveyor).

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Plane's speed (A)= 0

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As the plane moves, the conveyor moves but in the opposite direction.

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Plane movement (A). Conveyor Belt movement (B).

Now here's the key statement:

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The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

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Note that the statement says that the movement of the belt matches the speed of the plane EXACTLY. Now this could never happen in the real world, but in this answer, we have to assume those conditions. Therefore, Plane speed A. Conveyour belt (B) = -A.

So when the planes starts down the runway, the runway starts matching it's speed exactly. At 5 mph (plane speed), the belt is moving at 5 mph in the opposite direction. 5 + -5 = 0. So the plane thinks it's going 5 mph. The instruments wuold read that it's moving 5 mph, but because of the belt, it's not going anywhere. If the total speed of the system is 0, then there is no airflow, thus, there can be no flight.

This remains true no matter what the plane's speed. 250 mph + -250 mph = 0 total speed. Same at 500 or even 1000.

Given what we were told in the question, which isn't much, this is the only solution one can come up with. The plane never moves down the runway, even with engines wide open because the belt is matching speed EXACTLY and always has been.