Lets see the BRAINS of RME

[way2nosty]

The wheels under the plane are essentially free-spinning, a conveyor running equal to a 30 knot wind eastbound is not going to prevent the plane, pulling air aft, reaching the 30knot westbound needed to lift. The wheels will be spinning equivalent to 60knots but the plane will take off.

Except that the motor doesn't produce lift, the airfoil does, which means that the physical speed of the big chunk of metal is whats important, and for the record, there would be no airspeed because the way it is measured is off the speed of the wing in front of the propellar. it would be like an airplane running in a wind tunnel with the air travelling the opposite direction, It couldnt' produce enough lift either.

 

[BioNuke1]

Except that the motor doesn't produce lift, the airfoil does, which means that the physical speed of the big chunk of metal is whats important, and for the record, there would be no airspeed because the way it is measured is off the speed of the wing in front of the propellar. it would be like an airplane running in a wind tunnel with the air travelling the opposite direction, It couldnt' produce enough lift either.

im sure you could fly an airplane in a wind tunnel, you might even be able to leave the engine off. (or at least make it produce enough thrust to counterbalance the drag so you stay in one spot) you might not get anywhere, but you would be airborne

 

[Brad]

ok i'm going to try to break this down the way i am imagining it.

ok image first thing you put the plane on the conveyor and turn the converyor to 30mph.

the plane is going backwards at 30mph.

now slowly throttle the plane until it is stationary to a single point on the ground.

this is the equalibrium.

at this point the plane obviously will NOT lift off cuz the air isnt moving around the wing at all.

now if you throttle the engine hard, the plane will overcome the conveyor because the acceleration if coming from the air being pushed by the prop and not through the wheels. the plane will slowly gain speed and eventuallly take off.


the question is kinda vague and there is alot to be considered, but theres my solution for each view

You won't reach a point of equilibrium. The moment you increase throttle in the plane to a point sufficent enough, the plane will start pulling itself through the air. It doesn't matter what the wheels beneath it are doing at this point (except for a nominal amount of drag). You can't think of a plane functioning like a car, where the reverse movement of the conveyor would cancel out the forward movement against the medium, which would be the conveyor itself.

 

[BioNuke1]

You won't reach a point of equilibrium. The moment you increase throttle in the plane to a point sufficent enough, the plane will start pulling itself through the air. It doesn't matter what the wheels beneath it are doing at this point (except for a nominal amount of drag). You can't think of a plane functioning like a car, where the reverse movement of the conveyor would cancel out the forward movement against the medium, which would be the conveyor itself.

think of it this way instead, if you have a 30mph tailwind and you are going down the runway at 30mph, the airspeed is 0, you cant lift off

the wheel speed is irelevant, the speed of the plane over the ground (or through the air since the ground and air are equal in the question) is what is relevant

 

[crimsonride]

this is the longest, dumbest thread I've ever wasted my time reading.

 

[crimsonride]

think of it this way instead, if you have a 30mph tailwind and you are going down the runway at 30mph, the airspeed is 0, your cant lift off

What if it was a helicopter, or a car, or some kind of helicopter/car vehicle on a huge conveyorbelt flown by a fat chick who runs on a treadmill?

 

[Brad]

think of it this way instead, if you have a 30mph tailwind and you are going down the runway at 30mph, the airspeed is 0, your cant lift off

Read the excerpt Greg posted above. It covers this. You'd have to have 60mph groundspeed and a longer runway.

 

[BioNuke1]

Read the excerpt Greg posted above. It covers this.

I know. air speed is what matters, that's what ive been saying since my first post

 

[Fester]

This caused a thread of more than 200 pages on another board due to people being idiots....lets see who's smart on here. :greg:

Are the smart ones the people who were able to avoid being drug into this and beaten down with ignorance?

The plane flies.

 

[way2nosty]

think of it this way instead, if you have a 30mph tailwind and you are going down the runway at 30mph, the airspeed is 0, you cant lift off

the wheel speed is irelevant, the speed of the plane over the ground (or through the air since the ground and air are equal in the question) is what is relevant

I'm Gonna have to turntail on this, I asked an astro-physicist friend of mine, here is the reasoning.

Because the thrust is acting against the air behind the aircraft, Not against the ground it is going to push the airplane forward, it doesn't matter if the Conveyer belt is travelling at 300 miles per hour. The wheels on a plane only hold the plane up off the ground, and do little else. He said that the example with the crane is inaccurate, because the plane would pull against the cables because the force is against the air behind the plane, and has nothing to do with the ground.

 

[crimsonride]

Wow, so you're saying an airplane isn't a car????? Weird...I was just about to beat this topic into the ground when I suddenly realized airplanes are powered with propellers and not transmissions and axles and wheels...what the heck, let's go another 193 more pages just for the heck of it.

 

[Brad]

I'm Gonna have to turntail on this, I asked an astro-physicist friend of mine, here is the reasoning.

Because the thrust is acting against the air behind the aircraft, Not against the ground it is going to push the airplane forward, it doesn't matter if the Conveyer belt is travelling at 300 miles per hour. The wheels on a plane only hold the plane up off the ground, and do little else. He said that the example with the crane is inaccurate, because the plane would pull against the cables because the force is against the air behind the plane, and has nothing to do with the ground.

It makes sense when you look at it from a physics standpoint instead of engineering or mathematics. But now that it makes sense from a physics standpoint, it makes sense from an engineering standpoint too. Go figure.

 

[way2nosty]

Its all based on a well overlooked fact that air has mass and therby can be acted on or against by an outside force - un named astronomical engineering type, who I argued with for 2.5 minutes before he made me see the errors of my way.

 

[way2nosty]

Wow, so you're saying an airplane isn't a car????? Weird...I was just about to beat this topic into the ground when I suddenly realized airplanes are powered with propellers and not transmissions and axles and wheels...what the heck, let's go another 193 more pages just for the heck of it.

Change the channel, its easier then complaining!

 

[crimsonride]

Oh, I'm not complaining, just making fun of how it's taken us 7 pages to realize planes don't drive, they fly.

Not aimed at anyone.

 

[way2nosty]

Oh, I'm not complaining, just making fun of how it's taken us 7 pages to realize planes don't drive, they fly.

Not aimed at anyone.

US

 

[crimsonride]

US

Ok...yeah, sure, it's aimed at all of us. And you all deserve it.

 

[waynehartwig]

I'm Gonna have to turntail on this, I asked an astro-physicist friend of mine, here is the reasoning.

Because the thrust is acting against the air behind the aircraft, Not against the ground it is going to push the airplane forward, it doesn't matter if the Conveyer belt is travelling at 300 miles per hour. The wheels on a plane only hold the plane up off the ground, and do little else. He said that the example with the crane is inaccurate, because the plane would pull against the cables because the force is against the air behind the plane, and has nothing to do with the ground.

This is what I said at 930 this morning, shortly after the question was posted...

Yup... The wheels aren't driven. The jets are what moves the plane so the conveyer is then useless.


And to think you actually had me second guessing myself.... Becuase my first instinct was no, it wouldn't fly because of the air thing that you have been talking about. But then I got to thinking about it, for oh 30 seconds, and re-nigged on my original post. If it was a car on the treadmill with the fat chick in the drivers seat...Oh wait, it can't fly anyway...

 

[Cody]

that was obvious. whats so hard about that?

brett, get a job.

 

[troutbum]

Agreed without lift which is generated my the WING moving thru the air that plane will just burn lots of kerosene

agreed , it does no tmatter how much air trvels through the engine if there is no air traveling over the wing...


EDIT----guess I should have read all 10 pages first...Now I am not sure if there is air traveling over the wing.. . damn it...