BF2S Forums A question about a airplane on a treadmill.

burton wrote:

but seriously...it wont take off its like jogging in place, you can jog as fast as you want but do u feel any wind on your face? that is as long as its not windy outside.

Last edited by heggs (2006-12-28 06:04:49)

deeznutz1245 wrote:

d3athwi5h4 wrote:

No, the plane being stationary wouldn't create any lift

exactly

Coolbeano wrote:

Yes Heggs, I read (the bulk of) it, and you're forgetting one minor detail. Look at my 'diagram' above.

If the engines are in such a position and have enough power, there WILL be airflow over the wings.

The treadmill and wheels are only there as a means of 'keeping the plane stationary' as I have so delicately illustrated.

Last edited by heggs (2006-12-28 06:16:53)

-=raska=- wrote:

if you push a toy car that is on a treadmill, do you think you would be able to move it forward, even if the treadmill push it in the opposite direction ?

Yes, the treadmill may go in uberhigh speed, this will only affect the rotation of the toy car's wheels, and you will be able to move it forward.

Now replace your hand by jet engines...

aardfrith wrote:

deeznutz1245 wrote:

d3athwi5h4 wrote:

No, the plane being stationary wouldn't create any lift

exactly

Think about what happens when you're in an aeroplane, sitting at the end of the runway and you've been given permission to take off.  You (the pilot) increases the thrust through the engines - the thrust being the force that sucks air in and spits it out the other side.

Ignore the wheels at this point - the only purpose they serve is to keep the belly of the fat arsed plane from scraping on the ground.

Back to the engines.  They are going at full thrust now, sucking air in and pumping it out.  The air that's being sucked in is going to be replaced by more air and that's also going to go in through the engines and out the back.   

The pertinent question you have to ask here is whether any of the air around the engines is going to go over the wings.  I think the answer is a big fat, like the belly of the said aeroplane, no.

It's the same as if the aeroplane were still sitting at the end of the runway with its brakes on.  The wheels are straining to turn because there's all this power urging them forward but the brakes are still on.  And while that's happening, the plane's not lifiting into the air, is it?  Same thing as if the brakes were off but there was a humoungous treadmill or the plane were on a frictionless surface.

spray_and_pray wrote:

Even with engines the aircraft has to move forward somehow if its wheels meant nothing the aircraft wouldn't go anywhere the wheels roll to help the speed of an aircraft build up have you ever seen an aircraft thats performed a belly landing takeoff? With all the thrust in the engines after an eventual amount of thrust the wheels would move if wheels didn't move and werent a factor in aircraft we could just line the bottom of an aircraft in rubber so that way it could skid across the runway. Stationary wheels would never move an aircraft has anyone seen a video of a pilot landing an aircraft with parking brakes on? Thats what happens when wheels dont move at high speed and remain stationary you end up with the nose planted in the ground. When a pilot powers up an aircrafts engine it takes a little while for the power to go from the sucking and blowing to the wheels moving forward when the power gets to them. If the wheels could never move at any speed the aircraft wouldn't be able to move at anyspead unless it was a VTOL the treadmill wouldn't start moving until the aircraft would start moving because it matches the speed of the wheels. Someone could be giving a jet fighter 100% thrust with afterburners on a runway but if the wheels couldn't go forward the jet won't go forward. Its known on STOL fields to hold the brakes on an aircraft and power up to 100% until the engines stabilize the aircraft doesn't move forward even with 100% thrust simply because its wheels arent spinning cause the brakes arent on.

In this scenario the treadmill is acting as the brakes any movement in the wheels is counteracted by the movement in the treadmill and it stands still. I beleive most people understand how an aircraft works but for some reason people beleive that the aircraft engines generate lift and it will move forward and takeoff no matter that it is not moving what so ever on the ground. A propeller aircrafts engine might create the slightest amount of lift the most minescule and that would be if its a front mounted prop aircraft because prop aircraft also use bernoulli's theory when it comes to propeller design. Propellers can also be feathered in more complex aircraft this is when the actual blade of the prop itself moves. This is done when an engine fails to reduce the amount of drag the prop creates. This however is on the more complicated aircraft.

This thing alone leads me into wanting to buy a small fuel driven aircraft (model) and buy a treadmill  then match the speeds of the treadmill and the aircraft to show that it wont get anywhere. With all the thrust the engine is producing it would stay still if the thrust that it created was taken out because the wheels couldn't move at all. And if the aircraft starts at 0 kmph it will never accelerate the wheels would never move whatsoever no matter that thrust was being produced by aircraft. Tell you what ill call up my old physics teacher he had a PHd in Newtonian Physics and Quantum Physics (I dont know what the guy was doing in a highschool) and we will see... Then again I dont know how to get into contact with him since I was in highschool 8-9 years ago. Anyone got a friend that has PHd's in those two areas?

Sk wrote:

see now.. if this question had been worded oh so slightly different.. then the answer would have been NO...

However, the question clearly states
This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same

this means that if the plane is travelling forward at 10mph, the treadmill is only moving at 10mph, but that means the jet's wheels will be turning at 20mph... and the jet can continue forward at a leisurely 10mph forward, with it's wheels spinning freely at 20mph, until it get's off the runway.

You could exand this and say the aircraft accelerates to say 150mph, where it normally generates enough lift to take off.
AT THIS POINT, the treadmill is going 150mph in the opposite direction, which simply means the jet's wheels will be turning at 300mph as they leave the ground.

HOWEVER..... if the question had been worded as such:
This conveyor has a control system that tracks the
[u]speed of the plane's wheels[u/] and tunes the speed of the conveyor to be exactly the same
Then the answer becomes a LOT more complicated (and is still argued by scientists to this day )

-=]NS[=-Eagle wrote:

They way a plane works is as follows:  The airfoil creates lift because of a high pressure system created under it.  This is all explained in Bernoulli's principle.  The way the airfoil is shaped makes it so when air hits it, the air particles that go over the airfoil have to travel a longer distance than the particles that go under it.  And since air particles must all move at the same speed, the air that goes over the air foil must move faster to keep up with the air that goes under it.  This creates low pressure above the airfoiil which allows the high pressure beneath it to push it up.  SO if the plane wasn't moving, there wouldn't be any air moving over the airfoil to lift the plane up, therefore making the treadmill useless.

Thank you for your time :-P