will it take off?

[Iplayfarmer]

Will the plane take off or not?

Yes.

I'm in the "Airplanes are propelled by prop./jet thrust, not by wheels" camp. Seems pretty cut and dried to me.

 

[rback33]

I think I can say yes somewhat definitively, thanks in part to the "Reynolds number." (lol I loved that btw).... while the plane may be stationary, the conveyor and props/jet engine will eventually create enough enough airflow across the wings through their mere function to get the bird off the ground. (this next part, I am applying terms to things that are obviously theoretical... I mean look at the subject..)

I also think the "theoretical speed" being the speed the plane would be flying at if it were not for the conveyor will be MUCH higher than twice the speed of normal lift off. To create that much airflow the conveyor would be moving much faster than that. I am trying to envision what would happen after it left the ground. Would there be enough airflow to keep it airborne, or would it come right back down? Would it just hop up and down in and out of the flow?On another thought... are the engines on this plane infinitely capable of increasing the "thrust" it uses to become airborne? If so, is THIS flow the effect that causes the lift not the conveyor? If so, I don't think know how the plane would handle the dynamics as it began to fly.

 

[Jimbrown]

Having spent a good amount of my life flying military aircraft the answer is it depends on the aircraft. Normal airplanes require airflow over the wing to fly. If there is no airflow it will not fly. So 99% of airplanes would not fly If they could you could simply lock the brakes and run the engine to full power and lift off with out any runway. Normal airplanes can not do this. However there are some that can. A good Platus Porter with a strong turbo and no weight inside if run to max power can be made to lift off from a dead stop. I never tried it but am pretty sure and F16 or F14 with no payload setting on a aircraft carrier if run to full power and afterburner would probably fly straight up. Assuming you could control it which you probably could not as it takes airflow over the controls to make the thing turn. Engine torque would probably spin the thing out of control. It would probably be near impossible to get one in that configuration with out breaking something.

 

[rback33]

Having spent a good amount of my life flying military aircraft the answer is it depends on the aircraft. Normal airplanes require airflow over the wing to fly. If there is no airflow it will not fly. So 99% of airplanes would not fly If they could you could simply lock the brakes and run the engine to full power and lift off with out any runway. Normal airplanes can not do this. However there are some that can. A good Platus Porter with a strong turbo and no weight inside if run to max power can be made to lift off from a dead stop. I never tried it but am pretty sure and F16 or F14 with no payload setting on a aircraft carrier if run to full power and afterburner would probably fly straight up. Assuming you could control it which you probably could not as it takes airflow over the controls to make the thing turn. Engine torque would probably spin the thing out of control. It would probably be near impossible to get one in that configuration with out breaking something.

Makin a lot of assumptions there, so I think we have to rule your practical knowledge of the hypothetical situation as invalid. Someone that KNOWS something cannot reply to this thread.

You did however explain some things I had going through my head and couldn't properly convey so I guess it can stand.

 

[BillyP]

The question is, can a plane take off from a stand still. It's possible but highly improbable. At some point the prop has to create a lift under the wings and it ain't gonna happen on a prop driven plane. Harrier jet, yeah.

 

[CharlieTR]

The plane is not moving because the magical conveyer is matching the speed of the wheels in the opposite direction. If the plane does not move the plane does not fly.

 

[rback33]

The question is, can a plane take off from a stand still. It's possible but highly improbable. At some point the prop has to create a lift under the wings and it ain't gonna happen on a prop

driven​

plane. Harrier jet, yeah.

OK, now what is your explanation for this? I mean, we are defying SOOOO many physical possibilities already, what makes it IMPOSSIBLE for a prop plane of any imaginary composition to do this? Now, don't get me wrong, I don't know if there is or isn't. My degree is in biology. I just love science a whole so this discussion is fascinating to me.

 

[rback33]

The plane is not moving because the magical conveyer is matching the speed of the wheels in the opposite direction. If the plane does not move the plane does not fly.

I agree that the plane is NOT moving. However, the conveyor and the props or jet engines will MAKE airflow. At some (ridiculously impossible) point there WILL be enough flow to get off the ground. I just don't think it can STAY off the ground. That's my story and I'm stickin' to it. lol

 

[bx23barry]

I didn't hear the tree fall

 

[755inNY]

Assuming the plane is on wheels and the wheels can spin freely at the speed of the movable runway, the plane will take off when it reaches the airspeed required for take-off. The airflow from the prop or jet or the breeze from the moving runway will never provide enough lift for take-off.

Look at it this way. There is a 1 mile long conveyor 2 feet wide 4 feet off the ground (for convenience). On the conveyor is a box. The box has wheels at each corner. A pole runs through the box and extends 3 feet to either side of the conveyor. You are on one side of the conveyor and schmism is on the other side. You both start walking at the same speed each pushing on the pole running through the box. The box will move along the conveyor. The conveyor is controlled to move in the opposite direction of the box at the same speed as the box is being pushed by you and schmism. The faster you and schmism go the faster the conveyor goes. As you pick up the speed and run pushing the box at 10 mph, the conveyor increases its speed to 10 miles per hour in the opposite direction. Will you get to the end of the 1 mile conveyor (assuming you both can run a mile at 10 mph)? Of course you will. And, in reaching the the end of the conveyor, you would have moved though the air mass surrounding you at a speed of 10 mph.The force moving the box is independent of the wheels contacting the conveyor. The wheels will be spinning at a rate equal to 20 mph during your run.

A similar condition exists with the plane. The plane is being moved by the propeller, or jet engine if you prefer, independent of the wheels contacting the movable runway. The plane will move through the air mass while the movable runway moves at the same speed in the opposite direction. At the proper airspeed (plane moving through the air mass) the plane will take off and the wheels will be very thankful because they can finally stop spinning so **** fast!

Jeff