Best Tech. Debate: Groundspeed vs. airspeed

[Nikuk 5,000+ posts]

On a day with absolutely calm wind, a plane is standing on a runway that can move (some sort of band conveyor).

The plane moves in one direction, while the conveyor moves in the opposite direction.

The conveyor has a control system that tracks the plane speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

Can the airplane ever take off?"

Discuss.

This is the debate sweeping the internet, lately.

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[NhustlaR 10+ year member]

well if you listen to hoffmans 12th law of groundspeed you would find that the roto-technamovable objective of the conveyor belt will most definitly depress the E-gravatational pull of theyeah i dont know.

way too much thinking

 

[Nikuk 5,000+ posts]

lol, nice try.

 

[btnhfan 5,000+ posts]

The belt is moving but not the actual plane correct?

 

[Nikuk 5,000+ posts]

if the plane is carrying a groundspeed of 150 mph fwd, then the belt is moving @ 150mph rearward.

 

[jgarcia9102 10+ year member]

planes have to have air rushing past their wings to generate low pressure above the air foil. if the plane dosent move, then their is no wind, no lift, no take off.....

Ground speed means nothing to a plane. only the speed of the air rushing over the wings.

 

[Nikuk 5,000+ posts]

So You say that the plane is not moving? In reference to what?

 

[Do_ 10+ year member]

That's not entirely dooming this plane to the ground however. Think about this, what does a propeller do? It causes air to move and sucks the air around the wing. It would need to move a lot of air but I think a propeller driven plane could lift off under these circumstances. If you think about it the engines are still pulling the air past the wings at the same speed producing lift nonetheless.

 

[Mark_ab 5,000+ posts]

Considering only the wheels are turning and the engines aren't on, the plane will move slowly backwards.

 

[Nikuk 5,000+ posts]

Considering only the wheels are turning and the engines aren't on, the plane will move slowly backwards.

The plane moves in one direction, while the conveyor moves in the opposite direction.

Can the airplane ever take off?"

Good effort though.

 

[slim j 10+ year member]

Would it take off or lift...?

My assumption is that it wouldn't take off like an airplane on a runway but it would lift, but then fall down.

 

[Nikuk 5,000+ posts]

Why would it fall back down?

I think that You are closest to the truth insofar...

 

[Blazin_Jason 10+ year member]

Why would it fall back down?
I think that You are closest to the truth insofar...

After that point there is insuffiecient airpseed to generate any lift.

 

[jgarcia9102 10+ year member]

think about running on a treadmill though, there is no air rushing past you. its the same for the plane. its not moving in the same way your not moving when on a treadmill.

the prop thing may work, im no physics major, but the only real purpose of propellors/engines are to keep the plane moving at a fast enough speed to keep the lift on the wings. if the engines on a plane cut out its not like the plane falls out of the sky, it just slows down, and when it is going too slow for the airfoils to create lift, it glides down.

idk, im just rambling here, but it seems to make sense to me...

 

[JAZN 5,000+ posts]

I'm guessing it wouldn't lift off. Just a guess but lift is proportional to velocity (which is zero) and not speed (which is 150mph). And in this case, weight+drag > thrust+lift.