Plane on a conveyor belt?

wing.jpg


Look at the above diagram (I got the simplist one i could)
For a plane to create lift air has to be moving around the wing, as the air above the wing has less pressure(its moving faster) then the air going under it it is pushed up by the pressure of the air and lift is created. Now if a plane is on a treadmill it would just keep going really fast as logn as the treadmill is capable of matching the speed of the engines. The engines are there to move ther plane and get the air going aroudn the wings and other parts of the plane. Either the plane has to be moving or the wind must have the same speed as the plane would have before launch.
When a car is on the Dyno does it cut through air? No becasue it needs a big ass fan to cool it.
 
But the wings will be moving through the air!!!!

The conveyor belt wouldn't stop the plane moving forwards!

Stop thinking 2 dimensional.

The wheels don't produce forward momentum and as they are the only point of contact the plane remains relatively disconnected from the forces of the belt.
 
Because the wheel bearings counteract any forces between the plane and the conveyor. When I say any I mean most of, there will be slight friction there but such a little amount it's not worth counting.
 
The conveyor could be rolling back at many times the speed of the plane, it'd be the effect of the thrust on the air that would make a difference. So long as the thrust given by the planes engines is sufficient to move the plane it will move.

If the wheels were driven it would be different but they're not.
 
ollyc98 said:
But the wings will be moving through the air!!!!

The conveyor belt wouldn't stop the plane moving forwards!

Stop thinking 2 dimensional.

The wheels don't produce forward momentum and as they are the only point of contact the plane remains relatively disconnected from the forces of the belt.
Click to expand...

No it won't stop it moving forwards but it will stop it moving through air though as air isn't like the ground as thats waht the tyres help it do mvoe through the ground so it mvoes faster through air creating the lift.

But it is possible on a plane with the propeller on the front which is turned by an engine as that will create the necessary air velocity. A 747 or similar plane would not be able to lift on a converyor belt.

If what you say is true then we would flying all over the place (because of thea air) because when the plane is ready to lift off the velocity of the air is immense.
 
sonic said:
ollys skateboard on a treadmill is a good analogy, if it was a powered treadmill moving at 10mph, and you were pushing the board at enough force to make it move at a speed of 10mph in the opposite direction of travel, then the board would stay still on the treadmill wouldnt it, there would be no air movement past our olly would there, so if olly was a plane he would have no lift, so no take off regard less of the effort put in.
Click to expand...

you hit it on the head,

if you where "stationary" on a moving tread mill and then pushed the skate board forward, you will have still pushed the skateboard forwards........ it would not stay still.... it will move....only the wheels are now moving faster than they normaly would be, much like it would if the treadmill was at twice the speed you started at. substitute the "you" for a jet engine and voila. take off.

how are people not getting this?

its simple. realy realy mind numbingly simple. like i said before, substitute stuff you dont understand for things you do.

a treadmill, a skate board.... and a piece of wood......
if you pushed the skate board forways with the wood and turned the tread mill on at the same time...... would the skateboard move forwards?..... of course it would. the only other outcome is that you move backwords...... how is that gonna hapen when all you are pushing is a skate board on wheels?????

pleas please dont make me explain this again.
 
ok going to try and help out here and take it from someone who is in the industry.

Fact...as mentioned earlier in the thread the only thing that allows an aircraft to attain flight is relative airflow over the wing at speed creating a low pressure above and a high pressure below = lift. once the lift overcomes the weight of the aircraft it will fly.....Easy

so a few scenarios for you take off speed say 100mph and assuming a conveyor of immense length

Aircraft on conveyor engines not running brakes off....

conveyor starts and progressivly increases in speed wheels will spin and also aircraft may move backwards slightly due to bearing drag...no flight

aircraft on conveyor engines at takeoff power brakes off......

conveyor starts and at the same time takeoff power is applied the aircraft will move forward over the conveyor once 100mph relative airflow over wings reached aircraft will fly only difference to a normal runway takeoff here is that the wheels will be spinning a lot faster assuming that the conveyor is trying to match the aircrafts speed

Aircraft on conveyor engines not running brakes on

the aircraft will move forward and once the conveyor has accelerated the aircraft to 100mph it will briefly fly then slow down and drop back onto the conveyor till it has reached 100 mph again just repaeat until bored basically there is no thrust to keep it airbourne so once clear of the conveyor it slows and therefore cannot maintain height

aircraft on conveyor engines at takeoff power brakes on

as above but once airbourne it will continue to climb and accelerate on engine thrust

I think that about covers it
 
Corbs said:
Can we just organise an MSC meet at heathrow?
Click to expand...

Lol

IT WONT TAKE OFF IF THE CONVEYOR MATCHES ITS SPEED COS IT WONT BE GOING ANYWHERE!

If for some reason, that defies the laws of physics, the plane left the conveyor it would technically be stationary in thin air and land. Surely this makes sense.

Im off to start my own mind ###### thread :)
 
To everyone that is thinking the plane will stay still:

STOP IGNORING ONE MAJOR PART JUST SO YOU'RE RIGHT!!! Think about the wheel bearings.

Ok science lesson time: what force does a conveyor belt use to move goods (or in this case a plane)?

FRICTION

And what does a wheel bearing do?

Reduces friction, and this stops the conveyor belts force being transfered to the plane.
 
Robb said:
Lol

IT WONT TAKE OFF IF THE CONVEYOR MATCHES ITS SPEED COS IT WONT BE GOING ANYWHERE!

If for some reason, that defies the laws of physics, the plane left the conveyor it would technically be stationary in thin air and land. Surely this makes sense.

Im off to start my own mind ###### thread :)
Click to expand...

so whats keeping it still?

the wheels moving forwards twice as fast? are you sure you honestly think that a jet engine with 40,000lbs of thrust can be held back by a rubber belt? on bearings?

it will move forwards as normal but with the wheels spinning twice as fast,

like i said before the belt could be running sideways and it would still take off (assuming the wheels were casters) its simple,




if i was stood at the side of a runway with a conveyor on it, and a plane decided to take off...... all that i would see is the plane making a lot of noise, maybe going backwords for a split second as the bearings friction is overcome. then off it would go, as normal, but with the wheels spinning wildly.

WE ALL KNOW IT TAKES AIRFLOW TO MAKE A PLANE FLY, WE ALL KNOW THAT LOW PRESSURE AND HIGH PRESSURE IS IN EFFECT AND WE ALL KNOW THAT WITHOUT THRUST THERE CAN BE NO LIFT.

we werent arguing that, the plane is actualy moving, as in relative to a stationary point. the belt has no effect on the plane at all...... you might as well remove the belt completely.
 
Clearly the plane would take off, i used to have this argument constantly with my so-called team leader. (I work building planes)

Another way of looking is to put your micra on a converyor, if the brakes are on and the converyor starts moving backwards, the car goes backwards. If the brakes are off then the car would move backwards but it wouln't imediately move backwards at the speed of the conveyor belt.
This is because the friction in the bearings and other parts that let the wheels turn means that some of the moving force from the conveyor is transferred to the car. If there was no friction in the wheels then wheels of the car would start moving backwards but the car would still still.

This is because for each action there must be an equal and opposite re-action. An object doesn't want to move, if it can it will sit still if the converyor belt moves backwards then if there is no friction then it is far easier for the wheels to turn then the plane to move. Its the same as when your car is on ice, you put your foot down on the accelerator, but because there is no friction between the wheels and the ground, its easier for the wheels to turn then the car to move forward.

Back to the plane, if the power to take off was generated through the wheels then no it wouldn't work because they would need to turn at twice the normal speed to take off.
Because the power is generated through the air, the wheels are free to turn at any speed they like, so providing there isn't a lot of friction we can ignore them.
Lets say an aircraft takes off at 200mph AIRSPEED, and the engines themselves are capable of pushing the aircraft up to 600mph AIRSPEED, then provided there isn't a lot of friction in the wheel bearings then the aircraft will be able to take off.

This is one of those things that is very hard to explain but trust use we're right, even the original source of the challenge says so.

On my boat i can be motoring at 7knots, but if i have the tide against me at 5knots i will only do two over the ground this is because my engine is using the water for drive. If i had a hovercraft then i could ignore the tide, because i am using the AIR not the water for thrust and there is minimal friction between the water and the craft.
 

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