I
imamartian
but do the wheels stay where they are due to the conveyor? or does the engine push against the air, which is not connected to the conveyor?
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Its already been answered above but my take on it is.....
You can simulate the plane going forward by having it on a conveyor belt all day long, but you need to simulate air like with a very large fan going over the wings otherwise the wings won't create lift.....simples!
You can simulate the plane going forward by having it on a conveyor belt all day long, but you need to simulate air like with a very large fan going over the wings otherwise the wings won't create lift.....simples!
I
imamartian
but thats the point, the engines push against the air....so want to move it forward.... however, the conveyor counteracts any forward movement... think about it !
Now about the hovering bird in a moving transit when the driver hits the brakes
The hovering bird in the transit is pretty much the same thing, the bird needs air hitting it straight on to create lift but the air in the transit is travelling at the same spped and direction as the bird so no lift is generated,
now put the bird on your arm and stick it out the window and you get your lift
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with the engine running the prop will pull at the air in front of it thus move the plane forward, the moving conveyor belt plays no part because the air above was stationary.
If the air moved at the same rate as the conveyor then you wouldn't even need an engine to pull the plane forward to create lift, the air moving with the conveyor would create lift going over the wings
If the air moved at the same rate as the conveyor then you wouldn't even need an engine to pull the plane forward to create lift, the air moving with the conveyor would create lift going over the wings
I
imamartian
so you have the force of the engines... and the counter force of the conveyor? so a stationary plane?
The wheels on a plane are not driven, they freewheel.
Thrust is provided by the engines and the plane will take off whenever the airflow over its wings reaches the planes take-off airspeed.
If the conveyor is moving in the opposite direction to the way the aircraft is facing then some thrust will be required from the engines to hold the plane from being moved backwards by the conveyor - but not actually all that much, just enough to overcome the rolling friction of the wheels so that the wheels spin on the conveyor while the engines hold the plane in place. Doesn't matter what speed the conveyor is going at, once the rolling friction is overcome then it's the conveyor which is driving the wheels round, not the engines.
From that point on, increased thrust will accelerate the plane forward and start to increase the airspeed over the wings. Once the airspeed reaches the take-off speed of the aircraft then up she goes. At that point the wheels will be spinning at take-off speed plus conveyor speed, but so what? They're only freewheeling anyway.
Thrust is provided by the engines and the plane will take off whenever the airflow over its wings reaches the planes take-off airspeed.
If the conveyor is moving in the opposite direction to the way the aircraft is facing then some thrust will be required from the engines to hold the plane from being moved backwards by the conveyor - but not actually all that much, just enough to overcome the rolling friction of the wheels so that the wheels spin on the conveyor while the engines hold the plane in place. Doesn't matter what speed the conveyor is going at, once the rolling friction is overcome then it's the conveyor which is driving the wheels round, not the engines.
From that point on, increased thrust will accelerate the plane forward and start to increase the airspeed over the wings. Once the airspeed reaches the take-off speed of the aircraft then up she goes. At that point the wheels will be spinning at take-off speed plus conveyor speed, but so what? They're only freewheeling anyway.
Absolutely correct, but the plane would still not take off because it needs forward motion to create lift or like i said before a big fan simulating forward motion
Inky Pete
From that point on, increased thrust will accelerate the plane forward and start to increase the airspeed over the wings.
Once the airspeed reaches the take-off speed of the aircraft then up she goes. At that point the wheels will be spinning at take-off speed plus conveyor speed, but so what? They're only freewheeling anyway.[/quote]
Couldn't put it better myself
From that point on, increased thrust will accelerate the plane forward and start to increase the airspeed over the wings.
Once the airspeed reaches the take-off speed of the aircraft then up she goes. At that point the wheels will be spinning at take-off speed plus conveyor speed, but so what? They're only freewheeling anyway.[/quote]
Couldn't put it better myself
I
imamartian
the air is not moving at the speed of the conveyor, it is still... so the plane needs to move quite quickly compared to the conveyor.. which runs against the plane?
But the conveyor is only spinning the planes wheels, so a relatively small amount of thrust from the engines will hold the plane stationary.
Depending on the weight of the plane, characteristics of the wheel bearings, friction between the tyres and the conveyor, etc. etc. etc. it's even possible that the conveyor could spin the wheels without moving the plane at all, the planes own inertia could be enough to hold it stationary.
The existence of the conveyor is actually irrelevent to the take-off of the plane. Engine thrust pushes the plane forwards through the (still) air, the airflow over the wings generates lift, when lift > weight then the plane takes off. What speed the wheels are going round at when this happens makes no difference at all.[/u]
Depending on the weight of the plane, characteristics of the wheel bearings, friction between the tyres and the conveyor, etc. etc. etc. it's even possible that the conveyor could spin the wheels without moving the plane at all, the planes own inertia could be enough to hold it stationary.
The existence of the conveyor is actually irrelevent to the take-off of the plane. Engine thrust pushes the plane forwards through the (still) air, the airflow over the wings generates lift, when lift > weight then the plane takes off. What speed the wheels are going round at when this happens makes no difference at all.[/u]
By jingo i think we've got it!
To put it in simple terms to generate lift you either need the air going backwards or the plane going forwards.
To put it in simple terms to generate lift you either need the air going backwards or the plane going forwards.
I
imamartian
but to move forward, to wheels would roll along the runway. but here the runway counteracts that forward motion, so the plane can't move forward !!!
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