Plane on a conveyor belt

[j2379]

awesome.... i love that show.

[RobRR]

THE THRUST IS FROM THE JET ENGINES! JET ENGINES! JET ENGINES! JET ENGINES!

The wheels just roll along. A planes speed is measured in air speed, not ground speed for a reason. The conveyor belt effectively doubles the ground speed, but has absolutley no impact on airspeed.

Ok, look at it this way. If a car with wings was on a conveyor. The car would not take off, because obvously, the conveyor would match the wheels speed and the car would stay staionary. This is because the cars propultion derives from the wheels.

The plane on the other hand is getting its propultion from the AIR, which the conveyor has no effect on. The wheels will be moving TWICE the speed of the airplane, but would not hinder it from taking off.

[JacksonDean]

Yes, aircraft measure speed with airspeed; however if the engine is only pulling the aircraft at the same speed the conveyor is pulling in the opposite direction, the aircraft is stationary.

Stationary aircraft means the wings are not moving through the air and are not generating lift. No lift; no flight.

[pott]

Yes, aircraft measure speed with airspeed; however if the engine is only pulling the aircraft at the same speed the conveyor is pulling in the opposite direction, the aircraft is stationary.

Stationary aircraft means the wings are not moving through the air and are not generating lift. No lift; no flight.

No. Wheels will be turning with the belt, the plane is then stationary, thrust makes it go forward hence airspeed.

ALL That'll happen is that the WHEEL speed will be twice normal. That's it. IT WILL move forward. Well physics laws say it should

[Sunbane]

No. Wheels will be turning with the belt, the plane is then stationary, thrust makes it go forward hence airspeed.

ALL That'll happen is that the WHEEL speed will be twice normal. That's it. IT WILL move forward. Well physics laws say it should

Wasn't the whole idea of the conveyor belt, that the aircraft would remain stationary?

[Bengal]

After watching the video, both planes in the examples were sitting still on the belt. No movement, no lift. No lift, no fly. Seems simple to me...

[Jason1212]

The wheels on the bus go round and round yet it doesnt fly. Without forward motion to generate air movement over the wing's surface or a fan blowing air over the wing's surface there will be no lift. No lift = no flight. Also if this theory work why are there not conveyor belts on aircraft carriers.

[z1n]

What about the air moving under the wings from the propeller? If the motor generates enough air, would that lift the plane? Or maybe if the plane had a motor in front of each wing. Would that work?

[dg]

no

If this was possible, then vertical takeoff planes would have been much easier to design, & we would've had them 60 or 70 years ago.

[JacksonDean]

What about the air moving under the wings from the propeller? If the motor generates enough air, would that lift the plane? Or maybe if the plane had a motor in front of each wing. Would that work?

dg is right. It's the airflow over the top of the wing (among other things) that create the lift.

[pott]

Yesyesyes but that is not the issue guys. The laws of physics tell us the plane WILL move forward :P Wheels cancel out the conveyor belt once the thrust starts, and thrust WILL push the plane forward.

[Bengal]

Yesyesyes but that is not the issue guys. The laws of physics tell us the plane WILL move forward :P Wheels cancel out the conveyor belt once the thrust starts, and thrust WILL push the plane forward.

That doesn't look like what they are doing in the video in the first post. Take the second example, the one with the tarp and the real plane. They are matching the speed of the tarp with the speed of the plane while thrusting. If the belt is matching the speed of the plane during thrust, it won't move. I see what you are saying but I don't think that's what they are doing. They are matching the speed of a thrusting airplane with the speed of the conveyor belt. That removes the thrust, the plane stays motionless, the plane can't fly...

But maybe I have it wrong. I'm no scientist, that's for sure...

[JacksonDean]

Yesyesyes but that is not the issue guys. The laws of physics tell us the plane WILL move forward :P Wheels cancel out the conveyor belt once the thrust starts, and thrust WILL push the plane forward.

Those very same laws of physics tell us that the plane without any thrust will be dragged backwards by the tarp. They also tell us that the plane will be dragged backward by the tarp if there is thrust but not enough to match the pulling force of the tarp.

No one is arguing ( that I've seen, anyway ) that if the thrust generated is greater than the pulling force of the tarp that the airplane will move forward.

Up to the point where the forces cancel each other out ( as the aircraft revs its engine to match the speed of the tarp ), there will be reverse airflow over the wing.

Beyond the point where the forces cancel each other out ( if the aircraft is moving faster forward than the tarp is backward ), there will be airflow over the wing.

But that is not the experiment.

The experiment is a stationary aircraft on a moving surface will be able to take off. And that's not going to happen.

When the forward force of the aircraft matches the backward force of the tarp, the two forces cancel each other out. The net force is zero. Which means the aircraft is stationary.

Since wings only generate lift as they are moving through the air, a stationary aircraft means a stationary wing. That equates to no lift.

[jim777]

If we could prove this for certain with beer, I'd be willing to drink a bunch to find the answer.

Just sayin'

[Evilution]

OK, let me make this simple to understand.

When you try to work out a formula, to get it to its base parts you have to subtract the same amount from both sides. In this case they are using a conveyor to null the foward speed of the plane.

If you removed the conveyor belt and removed the wheels so the plane was THEORETICALLY stationary no matter how much thrust the prop made you would have the same set up.

The prop doesn't create enough thrust to pull the plane forwards AND lift the plane, the prop has no bearing on the lift. Therefore if you have no forward momentum the plane will not take off.

It is similar to something else I tested.
Imagine getting a boat with big sails, if you hold a big fan behind it, the boat moves.
If, however, you attach the fan to the boat it doesn't move. This is because the fan would cause a backwards thrust which is negated by the forward motion of the air filling the sails plus the drag of the sails through the air.