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If a plane is on a Conveyor belt can it fly?

26.7k ToeTips  2 months ago

It's a question I came across recently and apparently it's been quite a debated topic for some while now.

-Yes the conveyor matches the speed of the plane's tires

Me personally, I think the plane won't go anywhere as long as the conveyor can keep up, unless the air is also on a conveyor or the plane in question is a Harrier or anything VTOL.

But what do you think?

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    @ToeTips
    The conveyor belt causes a very small acceleration of the plane in the direction of the conveyor belt due to rolling frictional force, assuming the brakes are off. This is true for either direction.
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    Thrust is the main factor of acceleration and will easily overcome this friction, just like it does on a plane on a normal runway.
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    Tip: draw a free body diagram

    Pinned 2 months ago
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    29.6k 32

    @ToeTips wait the edit changes things.
    I assumed you meant that the plane had its engines off, and was just sitting there on the conveyor belt. This is different. functionally speaking, if the engines are producing thrust, the plane will start moving in the opposite direction of the treadmill. The wheels will basically act as bearings, making it so the treadmill is in essence a frictionless surface. The plane is free to go in that direction relative to the ground, so if the belt is long enough it should take off.

    Pinned 2 months ago
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    26.7k ToeTips

    Broo
    I was legit getting bullied on Facebook cause of this

    Pinned 2 months ago
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    26.7k ToeTips

    Edit
    The conveyor belt is running against the direction of the plane trying to take off.

    Pinned 2 months ago
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    3,845 Quercon

    @CaptainNoble The conveyor belt is pulling the plane towards its tail, so the plane is experiencing relative tailwind. If the conveyor would be moving in the opposite direction, then aircraft will be experiencing relative wind in the opposite direction also. In both cases its just takeoff with some wind - which is definetily possible

    2 months ago
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    34.2k Dissent3R

    @Quercon the conveyor belt is going in the opposite direction in this case, not in the same. I personally feel like a lot more should be added to the question to give a more definitive answer

    2 months ago
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    3,845 Quercon

    @crazyplaness As all motion is relative, saying that a plane couldnt take off from conveyor belt is like saying that it cannot take off with a tailwind (not true)

    2 months ago
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    The engines provide thrust not lift. The wings provide lift when air flows over them. So if the plane is staying in the same spot due to the conveyer belt pulling it back the wings won’t get any airflow over them to generate lift. Therefore it can’t take off.

    2 months ago
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    29.6k 32

    @ToeTips as far as I know, yes

    2 months ago
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    @ToeTips no the plane can’t fly

    2 months ago
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    26.7k ToeTips

    @crazyplaness
    No need for that, I was wrong, I guess the plane can actually fly?

    2 months ago
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    26.7k ToeTips

    @MrSilverWolf
    Man I miss mythbusters.

    2 months ago
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    26.7k ToeTips

    @32 @hpgbproductions
    Okay so basically no matter how fast the conveyor goes, the plane will fly regardless?

    2 months ago
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    34.2k Dissent3R

    I think CaptainJoe explained this pretty well

    2 months ago
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    No way we got testing planes on the dyno before gta 6

    0_0

    2 months ago
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    Remember the engines provide thrust that move the plane not wheels, it will still take off, myth busters actually did this with a LSA and found that you can indeed take off on a oversized conveyor belt

    +2 2 months ago
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    @ToeTips Can I see this facebook post? I would like to see why the wrong people think they are right

    2 months ago
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    34.2k Dissent3R

    @ToeTips in that case, it will remain static

    +1 2 months ago
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    26.7k ToeTips

    @hpgbproductions
    Is this with the Conveyor going against it or for it? Because in this scenario the conveyor is running against the plane trying to take off.

    +1 2 months ago
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    26.7k ToeTips

    @CaptainNoble
    The issue is, the conveyor matches the speed of the tires and whatever thrust the engines produce to accelerate the plane will be reflected on the tires cause the tires will spin faster and the moment the the tires spin faster, the conveyor will speed up to counter. So my guess is that the Aircraft will remain static.

    +1 2 months ago
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    34.2k Dissent3R

    Funny how I was just thinking about this while taking off from the USS tiny. I think if the plane moves in the opposite direction as the belt at the same speed, it won't go anywhere, assuming the air that the plane is contained in is not somehow magically attached to the belt. So yeah, if the air somehow managed to "follow" the conveyor as it moved while the plane moved at that same speed in the opposite direction, it would probably takeoff, but like overlord said, the engines are what push the plane and not the wheels so if they can produce enough thrust to counter (provided the speed of the plane must not match the conveyor belt) then why not?.

    +1 2 months ago
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    29.6k 32

    There's no airflow over the wings. Like hpgbproductions said, the plane might roll forward a little bit, but nowhere near fast enough to take off.

    +2 2 months ago
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    I assume that the rolling resistance between the plane and conveyor belt is constant and small compared to thrust. The conveyor belt will have almost no effect.
    .
    If you can put a car in neutral at low speeds, where drag is very small, the acceleration will mostly be from rolling resistance.
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    If you put a plane with brakes off on a conveyor belt and gradually start the conveyor belt from rest, the plane should accelerate very slowly from rolling resistance. The acceleration is in the direction that the conveyor belt is moving.
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    If the conveyor belt is moving forwards, you can apply the brake to reach the same speed as the conveyor belt without using the engine.
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    If the conveyor belt is fast enough, you can approach takeoff speed, but rolling resistance (and friction during braking) are proportional to normal reaction force of the belt on the plane, which is equal and opposite to weight of the plane on the belt. The normal force will be zero somewhere around takeoff speed, so speed is asymptomatic at the takeoff speed (if drag is ignored). You cannot exceed the takeoff speed unless you do something that reduces lift first, like pitching down or retracting flaps.
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    The above paragraphs assume that air is static. If you want to consider it, there should be a small effect from the no-slip property of fluids, where the air touching the belt moves at the same speed of the belt. This will affect the takeoff speed if the conveyor belt is fast enough, and the wings are low enough.
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    Conclusion: You can still take off if you have thrust, but not if you have no thrust
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    tl;dr 👆🤓, i am bored rn

    +3 2 months ago
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    @TheMouse Sounds about rite

    +1 2 months ago
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    43.7k ShinyGemsBro
    • Belt running with the plane? Provided it's fast enough, yes. Like an aircraft carrier catapult, and the gears don't snap off.

    • Belt running against the plane? No. Since there's no proper airflow going on to generate lift with the wings even if there's thrust happening with the engines. The plane itself would just run endlessly on the conveyor belt unless it stops and it (the plane) moves on a static surface to allow lift to happen with the air moving around the wings again.


    This could just be a shortened response from what @TheMouse wrote.

    +2 2 months ago
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