Engines don't generate wind. Engines suck air through their turbine which creates thrust. Once the plane has lateral movement, air then starts to travel above and below the wings which create lift. It's a 2 part system. Engines make the plane go forward, the wings make it go up once it's moving forward.
Bad analogy. A good analogy would be a sea plane trying to take off on a body of water that is moving counter to its forward motion (assuming take off speed is about 120 knts and the water is moving in the opposite direction of @ 120 knts).
The watter current actually creates forces on the plane itself as the flotation stand at the bottom is directly connected to the plane. The wheels in a normal plane operate on their own bearings and can be spun to an infinite speed and create relatively little lateral force on the plane itself. I'm waiting for WWR's response. He just dismissed analysis from another board without offering much of his own, calling them "asshats" or something like that and making rolleyes to everyone who thinks the plane will move forward. If you want to be rude, at least engage yourself in the discussion.
I think of the riddle like this: Think of a car on a DYNO machine. The car is the plane and the DYNO is the conveyor. No matter how fast that car goes, no matter how high you get the RPMs, that car is going no where. But I think the riddle leaves alot out and can see both points of view.
Correction: The wheels are the contact-point between the plane and the ground. That is the point at which the inertia must be broken. All of the mass of the plane is focused on those very few concentrated points of contact - all of the weight of the entire plane, including engines, is going straight down through those points. There is a very strong inertial bond there which must be broken in order for the plane to begin to move. All the engines do is provide force, applied in a singular direction as thrust. If an equal and opposite force is applied in the other direction, from a magical conveyor belt, or a chain to a wall, or whatever, then the plane ain't moving. That's why it makes no difference for the experiment from simply 'standing still'. You are missing the point of the experiment entirely. The point is not to see if a very strong engine can overpower a magical conveyor belt. The point is to do a mental exercise to explore the idea of whether or not an airplane would be able to rise into the air if it never gets to establish forward momentum. Sure, you could blast off from just about any obstacle if you used a strong enough engine. What does that prove? Nothing at all. As someone else already re-iterated: the unspecified and very important distinction in the original 'riddle' is the difference between 'impede' and 'negate'.
but the riddle explicitly states a plane. so, now think of it as a plane with jet engines on a DYNO machine. I mean, the riddle says plane. Unless you strape that plane in, do you honestly think that DYNO machine has any chance in hell keeping that plane in place? The plane will jump right off that machine.
but the riddle explicitly states a plane, so you're version of it is about a car...not a plane. it is not the same. so, you much think of it as a plane with jet engines on a DYNO machine. I mean, the riddle says plane. Unless you strape that plane in, do you honestly think that DYNO machine has any chance in hell keeping that plane in place? The plane will jump right off that machine.
This is very simple. If you want to answer it in an abstract theoretical sense and ignore reality, then no, if a plane is on a treadmill and we can't factor in it's engines it will not fly. In reality, the power of a plane's engines will ultimately propel it forward despite the treadmill and it will fly.
The riddle specifies "same speed" not "equal force". The plane will take off simply because the force exerted by the conveyor on the plane is not enough to stop the plane from moving forward due to engine thrust. People are using the terms force and speed interchangeably and that is why this silly debate rages. And yes, the plane takes off.
1. some people take the riddle literally where a conveyor belt has no chance in hell of stopping a plane from taking off 2. others think the riddle is just figuratively using "conveyor belt" and is really asking "if the plane doesn't move forward, can it fly (ie generate lift)." imo, #2 is not a riddle.
This is exactly the problem. Of course if the question "Can an airplane that we don't allow to move forward fly?" the answer is no. This doesn't ask that though. It specifically asks if a plane is on a conveyor belt.
I dont understand why this is even a debate. 1) Engine moves plane forward 2) Movement forward forces wind over/under wings, providing lift. 3) If plane is unable to move forward due to conveyor belt negating wheel roll (that happens when engines push the plane forward), then wind doesnt move over/under wings. all this other more technical discussion is unneeded its quite simple as long as you understand what makes a plane leave the surface of the earth. if there is no wind from forward motion then there is no takeoff. Period.
I am one of those guys who evidently doesn't get it. If airspeed doesn't matter, why do airplanes always take off into the wind?
Airspeed does matter. The plane is moving at whatever mph it needs to take off...for the most part. Speed is a relative measurement. If you measure the speed of the airplane relative to the ground (ex. if you were standing on the grass with a radar gun) the mph would be whatever it is normally during a take off. If you were to measure if from the perspective of the runway, it would be double the normal airspeed since you (and your radar gun) would be moving very quickly in the opposite direction so it would appear that the plane is moving super quickly. No matter how you look at it, the plane still has a high speed. Addressing the whole situation, if you were in the airport hanger, the takeoff would look like any other takeoff you have seen in your life.
The wheel roll on an airplane is irrelevant. The engines will power the plane forward. The wheels will spin and it will move. But yes, if we accept that the plane can't possibly move forward then no, it won't fly. What we are arguing is that it will move forward.
Nero is talking about a problem that would arise if the example given was performed as it is described however I disagree with the idea that the expairment was created to test this problem. I think the fair interpretation is the one people have been discussing. His assumption seems flawed. The question asks us to assume the converyer is moving at the oppsoite speed, not that it creates the potential for opposite force. Once the plane has ANY speed, it has escaped it's stationary position so the belt would begin to move too late to stop the plane from getting momentun. Think about a train. It moves rather easily once it gets going but in order to move in the beginning, it's wheels have to move VERY quickly and create a lot of force to create momentum. In this first stage, the actual train does not move at all, only it's wheels. Once the train starts to move, it's wheels no longer have to work hard to accelerate it forward. Basicly, once the plane has any "speed" at all, the belt would not effect it's ability to move as it has already overcome it's inertia. I hope I am explaining this well.
