> A10 wrote:

> The treadmill moves the wheels at whatever speed it wants. The conveyor still matches the speed of the wheel. The plane pushes air against air to move. It doesn't push against the ground. Thus a plane can take off on a conveyor . . .

there was never a question if a plane can take off from a conveyor. because the conveyor could be going a fraction of a mile per hour and it would be cake. the question is if the conveyor matched the wheel speed, so that the plane would be stationary, if it could take off. and when the plane is moving forward while still ont he ground, it shows that the conveyor isnt matching the wheel speed, so the experiment is void, its no more impressive then taking off from a conveyor moving at a fraction of a mile per hour.

Ugh. Right, this is getting disgusting. I'm an aerospace engineering student (informally known as rocket science ). From a book I have:

http://books.google.co.uk/books?id=6-_iGbJHM-8C&pg=PA301&lpg=PA301&dq=%22when+a+moving+wing+is+close+to+the+ground%22&source=bl&ots=uD6m9ZTdrS&sig=wqfFtBthakNX2rVHb9nhG2Z28yg&hl=en&ei=b-SySYXsI6TEjAfera3tBQ&sa=X&oi=book_result&resnum=1&ct=result [edit] bah..you'll have it open this link in a seperate tab, doesnt work by click on this link :s.

If you take a look at that graph you'll see lift is totally dependant on AIRSPEED. Lift is the force on the aircraft used to overcome the aircrafts mass and take it off off the ground. If the aircraft is on a conveyer belt, and is not going anywhere, no lift is generated. If the thrust produced by the aircraft matches say a conveyer belt speed of 100mph, it is still not going anywhere, and still no lift is produced.

So if you have a conveyer belt to compensate for the forward thrust produced by an engine, the plane is effectively stationary.

Im not sure if you're getting confused A10. A propeller accelerates air in one direction (a force), and so results in an equal and opposite force which is what thrust is. Increasing this acceleration of air increases the thrust produced, and hence forward velocity. Once their is a forward velocity (the aircraft is moving forward through the ambient air), there is an airflow over the wings of the aircraft. This airflow produces lift. Once enough lift is produced (lift > weight of aircraft), the aircraft will take off. The airflow produced by the propellers/turbines of the engine has nothing to do with generating lift.

Yeah but. Until the lift from forward velocity is sufficient to cancel out gravity its still gonna put weight DOWN onto the wheel.  That's why it has wheels instead of legs, so it can still move while pushing down.  A VTOL gets around that by having engine thrust go to lifting the plane up.  Releived of the need to fight gravity, moderate lateral engine thrust builds airspeed.  If the speed of the conveyor belt was equal to ENGINE thrust (not wheel speed) the plane would just bob up and down in place.

Now, how many 100kg Jews would it take to stop a freight train weighing 1,000,000 kg moving 50kp/h?

didnt you see "Flight of the Phoenix"? a model aircraft is not a toy!!!

it takes 1 100kg Jew to put the brake on a train.

That seemed funnier when I wrote it, guess I shouldn't stay up until 8 am if I'm gonna tell jokes

would you not say that the airoplane is actualy generating thrust? because if it didn't how could it stay stationary on a conveyor belt?

Does this not mean that there is actual airflow? because if there wasn't how does the plane stay there. All you need is enough force

> Pixies wrote:

> There is an airflow created by the acceleration of air through the engine, however that airflow does not flow over the wings. Airflow over the wings produce lift. The thrust moving an aircraft forward means the aircraft is moving through ambient air, meaning an airflow is created over the wings. If a conveyer belt cancels this forward movement of the aircraft, the aircraft is effectively stationary in relation to the ambient air and so there is no airflow over the wings.

Due to the shape of a wing, air flowing over the top is accelerated more than the air beneath the wing. The faster the air flows, the lower the air pressure. So effectively a wing creates a region of lower pressure above it than below it, creating a net aerodynamic force upwards, called lift.
<

Obviously that is all bullcrap

If you have a small enough plane with a strong enough engine it works. Only thing limiting it is the strength of the engine, although a propeller engine also creates its own life by blowing the air backwards no?

Or a couple of propellers mounted on the wings

I thought we were talking about a 747?

I'm an aerospace engineering students ffs. I've made working remote control aircraft from scratch, I'm currently designing a small 2-person aircraft. Don't argue with me about this

Jeez, I am a friggin math man from heck, and I am telling you that it is not possible.

1) Thrust == Drag in your example, therefore there is only air through the engines, the engines do not lift an aircraft unless it is that Marine transport, or a helicopter, or a VSTOL type aircraft like the harrier.

2) Wing span is essential, why do you think if you take the wings off that a standard aircraft cannot fly?

3) Some propeller aircraft DO provide thrust UNDER a wing by incidental circumstances, half the propeller on each wing goes under the wing. So in theory a propeller aircraft could take off. However a jet engine never places air flow under a wing.

WILL IT TAKE OFF!????

op is a faggot

Avo, Shut it troll.

Say we have two objects. A long (like the size of a runway) conveyor moving at the planes max speed and a stationary tree next to the conveyor.

Now how do planes work? Do they turn their wheels or do they create thrust by pushing air against air?

On a conveyor at the planes max speed the plane will turn on it's engines and push against the stationary air. No matter how fast it's wheels are spinning it will move forward relative to the tree. It will take off in it's normal takeoff distance relative to the tree no matter how fast the conveyor is moving. The planes wheels are free moving. By the time the plane takes off the wheels will be spinning twice as fast as the speed of the plane but the plan doesn't move forward by depending on the traction of the wheels. It moves forward by pushing the air which unlike the conveyor is not moving.