At first glance, “It must not be possible”, but as you question, “I wonder!” an idea to say.
We asked someone who knows about the subject and Engineer Fatih İnal explained to us whether this idea is actually possible or not, in a language that everyone can understand.
If we put a conveyor belt (conveyor belt / treadmill) under a passenger plane and give full throttle to the engines, can we get this plane to take off?
In order to understand the answer to this, we need to touch on some basic concepts.
There are 4 fundamental forces acting on an airplane: weight, thrust, drag, weight.
- Weight: The force originating from the Earth’s gravity, always perpendicular to the ground and pulling the plane down.
- Thrust: It is the thrust that the aircraft gains by accelerating the air it takes from the front thanks to its engines and transferring it to the rear. As the engine power increases, this power also increases.
- Drag: It is the wind resistance that the aircraft encounters during its movement. As the plane accelerates, drag increases. As the plane accelerates, the speed of the air passing around its wings will increase. To better understand this situation, you can imagine that the plane is stationary on the ground and the wind on the plane is getting faster and faster. We can give an example of the aircraft hovering in the air when the ground speed is 0 (Ground speed: The speed of the projection of any aircraft in flight on the ground).
- Lift: The source of lift is the velocity and direction of flow of air around the aircraft’s wings. This is why the wind speed and direction to which the aircraft is exposed is very important for takeoff and landing. Because they have direct effects on buoyancy.
In other words, we can summarize the take-off of an airplane at the beginning of a runway as follows:
- Because of its weight, the plane is always gravitationally pulled towards the ground.
- With the engines powered up, the aircraft accelerates the air in front of it, transfers it to the rear and starts accelerating forward.
- Drag force is not a problem at this stage, as the thrust force produced by the engines is much higher than the drag force due to air resistance.
- As the plane accelerates, the amount of air flowing by its wings per unit time also increases. This increases the lift force.
- As soon as the lift force increases and starts to support the weight, the wheels of the plane are cut off from the ground and the plane starts to take off.
Now that we have learned the basics roughly, we can understand more easily whether the plane can take off with the idea here.
As the aircraft generates thrust, it will try to accelerate, but will not be able to advance at all because of the ground moving in the opposite direction at the same speed as its wheels.
All the power it will generate will result in it accelerating the ground beneath it in the opposite direction. Since the aircraft cannot accelerate, there will be no air flow around its wings. Therefore, a lifting force that can outweigh the weight is not possible in this case.
In the same scenario, if we consider that we increase the wind speed against the aircraft excessively, the wings can produce the necessary lift force to take off, but it should not be forgotten that the drag force will increase considerably in this case.
In this case, whether the aircraft will maintain its stability should be investigated specifically for the aircraft. Even if we could make this possible, it wouldn’t make much sense as it would be an unnecessary effort.
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