Would this actually work

[razgriz]

talos is right, myself being an aircraft mechanic i can tell u that it is a combination of thrust and of course lift to get an aircraft up, a glider can generate lift necessary to stay in the air but it cant generate the thrust to get up there so thats y it needs to be towed, there have been wingless aircraft but they r referred to as lifting bodies and again they needed help getting up there. i jus dont see the feasibility of a giant treadmill to launch aircraft. now a linear catapult or mass driver that has some feasibility to it

[mcred23]

You guys are all saying no, but I find it very hard to argue with the Mythbuster episode, where they showed that a plane can take off from a treadmill (They referred to it in the episode as a conveyor belt) moving in the opposite direction, and their explanation is making a hell of a lot more sense to me than confusing techo babble-ish reasons you people are giving for why a plane can't do what they showed it can do...

[pd771]

You guys are all saying no, but I find it very hard to argue with the Mythbuster episode, where they showed that a plane can take off from a treadmill (They referred to it in the episode as a conveyor belt) moving in the opposite direction, and their explanation is making a hell of a lot more sense to me than confusing techo babble-ish reasons you people are giving for why a plane can't do what they showed it can do...

It would work, it did work, and people are just not thinking logically. As long as the plane has enough movement of air surrounding it, it can take off. Since the wheels are not tied to the engine, the wheels are not used for propulsion, and it does not matter if you're a moving surface or a stationary one.

[Lans]

I'm with Red on this one. That particular myth was busted.

[Brave Fencer Kirby]

I'm very confused.

In order to take off, a plane must have a certain airspeed. Now, it's important to differentiate between airspeed and ground speed. Airspeed is how fast a plane is moving compared to the air it's moving through, while ground speed is how fast a plane is moving compared to the ground it's moving over. A plane standing still on the tarmac facing into a 20 mph wind has 0 ground speed but 20 mph airspeed. A plane moving 20 mph down a runway in the same direction as a 20 mph wind has 20 mph ground speed but 0 airspeed.

If you set up a treadmill-runway that went at 20 mph, then put your plane on it, when they gained enough speed to "stop" (as in, staying in one place while on the treadmill instead of being carried along by it) its ground speed would be 20 mph.... and it's airspeed would be zero (assuming still air). Given that planes have to have a certain airspeed in order to take off, it seems like the only way to take off from a treadmill would be to power up enough to go FASTER than the treadmill (eg, treadmill is going 20 mph, plane is going 30 mph on the treadmill, so plane has a total airspeed of 10 mph), which would actually mean the runway would have to be LONGER than normal.

Right?

[Seraphic]

I'm confused a bit, also, but I think I figured a bit of it out:

We know that the engines and the wings are working with the airspeed to take off. So what are the wheels and treadmill doing?

Well, they're cancelling each other out. Remember, the wheels are spinning freely as the plane is trying to take off. If the treadmill is trying to move the plane backward at 20mph, then the wheels will spin as though they're moving at 20mph in the other direction. So the plane will sit still, given that the engines are on.

But once the plane picks up speed, say it has a takeoff speed of 50mph, the wheels will spin that fast, in addition to the backward speed of 20mph of the treadmill. So the wheels have to spin at a literal rate of 70mph to simulate the takeoff speed of 50mph. The plane is not working any harder to do this. It just happens due to the wheels.

So the key is: the wheels spin freely over the treadmill, so the damn thing might as well not be there. The only way for the treadmill to have an effect is to lock the wheels. Otherwise, nothing is happening to the plane at all.

The free spinning wheels is why we see the plane move forward during takeoff, regardless of the treadmill being there or not.

Does that do it?

[neolordmaxwell]

That's pretty much exactly it right there, Seraphic. The entire confusion here is that moving the wheels has any effect whatsoever on the rest of the plane, which it is shown not too because once again, they are completely free spinning and might as well not even be there.

[razgriz]

yeah wow i need to go back to my basic aerodynamics/physics class i change my vote to yes a plane can take off from a treadmill, or conveyor belt, now try finding one thats big enough to launch a c-5 give me a mass driver or linear catapult anyday or even rato

[neolordmaxwell]

You're missing the point to the thread, Raz- it's not asking if a treadmill will launch an airplane, it's asking if it will keep it from taking off. That's the question currently being asked- if a treadmill going the opposite direction of an airplane will have any impact on the plane's takoff. Which, as shown, it will not.

[scythedd7]

You're missing the point to the thread, Raz- it's not asking if a treadmill will launch an airplane, it's asking if it will keep it from taking off. That's the question currently being asked- if a treadmill going the opposite direction of an airplane will have any impact on the plane's takoff. Which, as shown, it will not.

and further more, it doesn't help with take of either. Treadmills and planes, no point what so ever other then to maybe move a stationary one around the tarmac, and even that's sorta dumb. Seraphic explained it better then I did, as I have a poor use of words for that sorta thing, and I agree completely. The wheels just spin faster then normal, but that has nothing to do with its airspeed.

Also, to Talos who brought up gliders obviously didn't think that one through. Go take your glider and set it on a runway, and see how well that thing takes off. O wait...gliders don't take off, they have to be launched either by another airplane or some sorta catapult or wench. I really don't know what you were trying to prove with that one dude, as the question isn't will this help it take of, but rather can it take off. Because the engine acts on air, if its pulling what ever unit you use for that that would be equivalent to 30 mph in airspeed, it will (depending on actual wind conditions) have that much air passing of the wing, regardless of the ground. The reason engines are important is for that reason. If you had a glider and launched by like a car, and put both the car and the glider on the same runway and brought the car to launch speed and it was going against the treadmill. then it wouldn't take off because the cars engine creating the pull that pulls the wings that creates the life acts on the ground. But a prop plan with the same launch velocity on the same treadmill and it will take off. This is an important difference. *breathes heavily* I hope that clears that up, and why I talked about the what the engine (by which I mean the force that moves the plane forward at a rate fast enough to create initial lift)

[Lans]

Guys, don't be locked up by the term "airspeed". What you seek is the speed of air on both wings. Propeller planes sucked up air to the airframe and wings; even without moving on tarmac they could gain up the necessary air speed to achieve lift.

[Phoenix012]

Guys, don't be locked up by the term "airspeed". What you seek is the speed of air on both wings. Propeller planes sucked up air to the airframe and wings; even without moving on tarmac they could gain up the necessary air speed to achieve lift.

That's what airspeed is. It's called airspeed because its the speed of the air moving past the aircraft. The air itself may or may not be moving with respect to a fixed inertial reference frame (i.e. the Earth). It doesn't matter because as far as airplanes are concerned, all they care about is the how fast they are moving against the air.

Mythbusters proved that you can get a plane to take off, but only because they could move enough air past the airframe independently of the airplane's speed against the ground. Since aircraft instruments (except GPS) don't even bother reading speed against the ground, this should be hardly mind-blowing.

I don't know why people keep dragging this topic back up. The treadmill can be there or it can not be there, the result is 100% exactly the same. It has no positive or negative effect on the ability of the aircraft to take off.

[ORegan]

You're missing the point to the thread, Raz- it's not asking if a treadmill will launch an airplane, it's asking if it will keep it from taking off. That's the question currently being asked- if a treadmill going the opposite direction of an airplane will have any impact on the plane's takoff. Which, as shown, it will not.

Actually, Raz was right in regards to what the topic is asking...sort of

I was asking if it would keep the plane in place wile picking up speed, much like a person on a treadmill, which it apparently won't.

[ydawg314]

ok then why even use the treadmill? Why not just have the airplane tied down to the ground by something... and then let loose when the planes engines are at full power?

This whole Idea seems stupid to me seeing as how it is airspeed and thus lift created by that airspeed that make most comventional planes fly.

example

[Lans]

Convincing other people by just that are usually not enough. Most people still do the “seeing is believing” or fantasy feels better than reality. And stupidity grows faster in the internet.

Even now, some people might actually not convince about that. I think it’s because that it’s so common for a plane to run in the tarmac to gain speed before they took off, anything that suggest otherwise is utterly not-normal and unacceptable. OFC, most people don't know or just chose to forget about the airspeed indicator.

[ydawg314]

Actually after reading back a couple posts... I realized that I said pretty much the same thing you said... whoops