The WHOLE point of this is that the speed of the plane in relation to the air is completely independant from the speed of the plane in relation to the runway. This is the point I beleive you're missing...So a plane standing still in relation to the ground CAN be moving fast enough in relation to the air (because the ground is moving also).

The holding on to a remote control plane analogy has no bearing here, because in the question in post #1 the plane IS moving fast enough to take off with relation to the air.

I can't think of any more straight forward way to put it than this: the speed of the wheels is irrelevant to flight. Furthermore there is no way for the motion of the wheels on a plane to effect the air speed of the plane. Therefore a plane on a moving runway will take off as it would on a stationary runway, except the speed of rotation of the wheels would be different.

 

MVWRX, I think you are missing my point. The plane is moving fast enough to take off with relation to the air is/was my QUESTION. I was not stating that the plane is not capable of moving fast enough for take-off.

Also, I just re-read the #1, that statement (your statement below) is not there...

Ah yeah...

 

I don't think I am missing anything here... Re-read my post again. The only reason I mention plane moving forward at speed in relation to ground is because by doing so, you gain air speed. Imagine flying a kite, no prop or jet, just wings. You'll fly when you have enough air speed (Run and pull to fly the kite).

 

If a plane can take off on a stationary runway, it can also take off on a runway scrolling either forward or backward like a treadmill. Don't picture a treadmill, picture a runway that can move. The thing is: how is the plane and runway connected? The answer is that (for the purposes of this discussion) they are not connected, because the movement of the runway only effects the rotation of the planes wheels, not the movement of the plane itself.

The treadmill with skates is a good image. If you had the treadmill at full speed, and had rollerskates on and held on to the bar, you would stand still even though the tread and your wheels were hauling ***. Think of the 'plane' as 'you on skates' and the 'bar' as 'the planes engines pulling through the air'.
If you flex your arms and get closer to the bar, you will move toward the bar. Just like if the plane throttles the engine, it will move forward through the air.

 

If you think the plane can't take off, you are missing something.

 

so with your thinking, you are basically saying that with prop/jet alone, it can generate enough speed (plane relative to air) for it to take off. (which answers my question) Then I would have to say, yes, the plane will take-off.

But that brings another question. Why the hell do planes need to charge down the run way to take off? Why can't we just lockdown the brakes, bring prop/jet to full power, let the brakes go (maybe not even since we have 'enough' air speed), and off and we go?

Btw, you can bring the plane to full speed/power with brakes locked and stay in place. I just saw it on mythbusters the other day.

BTW, that episode was really cool. They blew away cars with jet wash (if that's what you call it) 50 ft away from the plane.

 

They need to charge down the run way because instant acceleration is impossible. So they have to cover every speed from 0mph to (liftoff)mph to take off. Planes can't take off how you suggest for the same reason cars don't instantly go top speed when you floor it.


That episode was cool.

 

You get it. A plane can generate enough speed for it to fly when it's not touching the ground, and that is the same speed it needs to take off (well usually they go faster in the air after they take off). So it can definatly generate enough speed relative to air for it to take off.

 

but why does it matter since air speed is all we care and need? Just like you can fly a kite without running down the park if you have enough air speed (relative to kite) right?

 

the only question you have to ask is;

how much air can pass over the wings?

so lets say for instance this conveyer belt is on the deck of an aircraft carrier. and the carrier can travel into the wind at 50knots (this is ridiculous number for a carrier of this size). on the deck we have a nice small 4 seater Cessna that requires a volume of air passing over the wings that can be met at a land speed of roughly 50knots. if said ship with said plane is heading into the wind at 50knots then there would be more then enough air passing over the wings to create the necessary lift for flight.

as said before the speed of the wheels and the belt are entirely irrelevant.

this being said, if the conveyer belt where in an enclosed room, then even if the belt and subsequently the plane where moving at 300 knots, because there is no air moving over the wings flight would be impossible.

but this entire process is ridiculous. the wheels on a plane are free standing, they spin freely. so even if you had this belt, and it was moving at 10 knots or 1000 knots as soon as you spun the prop, the plane would move forward over the belt.

 

You can fly a plane like you fly a kite on a windy day. But you have to have a very high speed wind that is very consistant, so I don't think it ever happens with wind outdoors. But in wind tunnels you can fly a plane similarly to how a kite flys in wind.

 

STOP IT!!!!!

Even in a room, the plane will move forward because of the thrust, can't you guys understand that?

The original question DOES NOT have an airspeed of 0- it states unequivocally "the plane moves one direction" the plane moves because its engines move air: therefore the airspeed does not =0

(Man, how I hate that the "unsubscribe" link drops you back in to see the latest nonsense)

This thread needs to die, and anyone who thinks the plane will not fly needs to go back to physics 101, not embarass yourselves here by making it known publicly that you don't know how planes work.

 

Pete,
I don't think it's a question if airspeed = 0 or not. I think we know the airspeed > 0. HOWEVER, in a real world, with jets/props alone, can they generate enough airspeed for the plane to take-off?

I do agree the plane CAN take-off IF the props/jets can generate enough airspeed for the plane to take off.

 

wait what? so what you are saying is that the props/jets alone DO NOT generate enough airspeed for the plane to take-off and it would require a wind tunnel.

 

All the answers are already in this thread.