A question...

[MrCoffee]

I do not think so. A plane needs air to move across its wings. Prop or jet plane, if the air going over the wing is not moving faster than the air below the wing the plane will not take off. If the wheels are spinning but the plane (wings) itself is stationary you do not get the drag effect.

however if you manage to land the plane on a treadmill like device it should instantly stop assuming the speed of the device counter matches the speed that the wheels would spin when it hits the ground.

[huggercamaro99]

No

[BLLDOGG]

Originally posted by MrCoffee:
however if you manage to land the plane on a treadmill like device it should instantly stop assuming the speed of the device counter matches the speed that the wheels would spin when it hits the ground.

exactly

[98Camaro3.8]

Originally posted by BLLDOGG:
Airplanes require air flow around the wings providing lift which is not achievable while being stationary.

That's the thing, it wouldn't be stationary. It's also the hardest part to figure out.

As far as the plane is concerned, nothing has changed. The propeller is acting on the air, not the treadmill (like if we were running on it, or a boat in a current). At rotation, the wheels would just be rotating at twice the airspeed.

[v6man]

even if the tredmill was to match the planes ground speed it would not beable to just take off.

it couldnt even leave the treadmill, there would be no forward motion of the plane just the wheels.

if the treadmill was to match the planes airspeed in a counter rotation the plane would still go off the treadmill while landing because of the plane as a whole is moving and the treadmill can only math the movement of the wheels.

[98Camaro3.8]

Let's say the airplane is making 1000 lbs of thrust. You agree the wheels will be rolling. The only force on the airplane from the ground is a bit of friction on the wheels (not even close to 1000 pounds). That means there's a net force in the forward direction, which pulls the airplane forward.

If you hit the brakes on the airplane, the moving conveyor would place a much larger force in the rearward direction (drag) because of the brakes...which would cancel out the thrust being created. With the brakes off, though, there's not enough drag to keep the airplane still.

[BLLDOGG]

Originally posted by 98Camaro3.8:
</font><blockquote>quote:</font><hr />Originally posted by BLLDOGG:
Airplanes require air flow around the wings providing lift which is not achievable while being stationary.

That's the thing, it wouldn't be stationary. It's also the hardest part to figure out.

As far as the plane is concerned, nothing has changed. The propeller is acting on the air, not the treadmill (like if we were running on it, or a boat in a current). At rotation, the wheels would just be rotating at twice the airspeed. </font>[/QUOTE]but how would the plane move? the engine would pull in the air, do its things and cause movement but at the same instant, the tread mill would counter act preventing movement. there would be no added air flow past the wings other than normal air current.

[BLLDOGG]

Originally posted by 98Camaro3.8:
Let's say the airplane is making 1000 lbs of thrust. You agree the wheels will be rolling. The only force on the airplane from the ground is a bit of friction on the wheels (not even close to 1000 pounds). That means there's a net force in the forward direction, which pulls the airplane forward.

If you hit the brakes on the airplane, the moving conveyor would place a much larger force in the rearward direction (drag) because of the brakes...which would cancel out the thrust being created. With the brakes off, though, there's not enough drag to keep the airplane still.

im trying to explain why i think it would stop so give me a sec to gather ny thoughts

[98Camaro3.8]

Originally posted by BLLDOGG:
but how would the plane move? the engine would pull in the air, do its things and cause movement but at the same instant, the tread mill would counter act preventing movement. there would be no added air flow past the wings other than normal air current.

To remain still with the engine creating 1,000 lbs of thrust, there needs to be 1,000 lbs of drag in the opposite direction.

The treadmill moves in the other direction, which speeds up the wheels. The treadmill doesn't actually impart a force on the airplane. It simply makes the wheels go faster. There is only a very small force of drag on the wheel bearings from the spinning wheels.

[v6man]

the thrust being cancelled out with the brakes being applied (if the brakes are applied suddenly) would just throw the plane in the directon of the treadmill. which would be backwards. with the brakes off it will just stay stationary until the treadmill or conveyor stops moving to allow the air to move over the wings and the airplane into flight.

[BLLDOGG]

Originally posted by 98Camaro3.8:
</font><blockquote>quote:</font><hr />Originally posted by BLLDOGG:
but how would the plane move? the engine would pull in the air, do its things and cause movement but at the same instant, the tread mill would counter act preventing movement. there would be no added air flow past the wings other than normal air current.

To remain still with the engine creating 1,000 lbs of thrust, there needs to be 1,000 lbs of drag in the opposite direction.

The treadmill moves in the other direction, which speeds up the wheels. The treadmill doesn't actually impart a force on the airplane. It simply makes the wheels go faster. There is only a very small force of drag on the wheel bearings from the spinning wheels. </font>[/QUOTE]even with 1000 lbs of thrust, it cant be conveyed into forward motion without being able to to over come the counter force, friction or in this cause, the treadmill

[v6man]

no matter the thrust the treadmill is counter acting all movement by moving in the oppsite direction.if the wheels can not make any real movement forward and allow more air than a breeze to go over the wings the plane will stay on the tread mill and do nothing .

what do you thing would happen if you didnt tie your car down on the dyno and the drum was to just free spin. your car would remain in place.

[fbird01]

Back to if it will fly, do you actually think that once the last wheel of the plane lifts off of the ground the plane will go from 0 to ~150mph to take off and fly?

And as for stopping the plane on the ground with the treadmill i think it would be impossible.

Im just thinking of it as standing away from the plane watching it.

Whens the last time uve seen something go from ~200mph to a dead stop without being destroyed?

[MTMike]

If you're on a treadmill wearing rollerblades what happens? If you pull yourself forward while on a treadmill wearing roller blades, do you move forward?

[img]graemlins/popcorn.gif[/img]

[98Camaro3.8]

Originally posted by v6man:
what do you thing would happen if you didnt tie your car down on the dyno and the drum was to just free spin. your car would remain in place.

You can't use a car here, because a car acts on the ground, not on the air. That's a big difference.


The question says the treadmill moves at the same speed as the airplane. So when the airplane is moving forward at 10 mph, the treadmill is moving 10 mph in the other direction. The airplane is actually moving forward at 10 mph, just the wheels are rolling at 20 mph.