(no subject)

[grindmonkeh]

On Mythbusters January 30th:

A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction).

The question is:

Will the plane take off or not?

This has started a wager war here at work.

My money is that the plane will take off. Any one bet against it?

I've got my reasoning, but I'm keeping it under a lid for now...so that people can genuinely reason it out themselves.

Comments

[merenda.livejournal.com]

I'd say no, because there's no air current to lift the plane up...but I could be misunderstanding the situation. :)

[grindbastard.livejournal.com]

You're assuming that the plane will sit still. I don't believe that it will, due to the minimal friction (wheels) the conveyor is applying to the propulsion (engine-propellor-air).

[merenda.livejournal.com]

Yes. Yes I was. :)

[grindbastard.livejournal.com]

So you want in on the action? :)

[merenda.livejournal.com]

LOL! No way. :)

[merenda.livejournal.com]

I *also* assumed a jet engine plane, NOT propeller. So I didn't even have any air lift from the propeller in the equation. :)

That being said, and knowing it's a propeller plane, you can still put me in the "does not fly" category. Strictly. :)

I'd bet you on it, but I live in Asheville, NC. :)

talk to you soon!
-Frank

[grindbastard.livejournal.com]

[merenda.livejournal.com]

great, now I'm going to have to watch mythbusters on the 30th. :)

[xmoviebrainx.livejournal.com]

I agree with merenda.

If this worked why wouldn't aircraft carriers employ the technology? They need the airflow over the wing to produce the lift. If the plane is stationary with the ground moving under it (and assuming the conveyor belt doesn't affect air flow) how would it be different than the plane standing still without the engines on?

[grindbastard.livejournal.com]

I'll c&p my response to Miranda.

You're assuming that the plane will sit still. I don't believe that it will, due to the minimal friction (wheels) the conveyor is applying against the propulsion (engine-propellor-air).

I may be wrong...I have lots of people at work arguing with me! :)

[grindbastard.livejournal.com]

So you want in on the action?

[vertexnormal.livejournal.com]

Lift is provided by airflow over the wings, if the air isn't flowing over the wings at a fast enough rate it will not take off. It is the plane's movement through the air that causes it to fly, not its speed relative to the ground.

[grindbastard.livejournal.com]

I know the laws of lift...2 years wasted with AFROTC.

I'll c&p again...

You're assuming that the plane will sit still. I don't believe that it will, due to the minimal friction (wheels) the conveyor is applying against the propulsion (engine-propellor-air).

I may be wrong...I have lots of people at work arguing with me! :)

[scendan.livejournal.com]

My guess is that it will, because the plane needs to generate enough wind to create lift, not necessarily overall speed.

That's my guess, pre-coffee. So...not positive, but that's what I'd think. As long as enough air is moving under and over the wings at differing speeds due to wing design, you should be able to generate lift.

[merenda.livejournal.com]

I'd agree with this if the airplane was in a wind turbine, and the turbine was creating the wind against the airplane. I don't *think* that's the case here, but I could be wrong...

-f-

[xmoviebrainx.livejournal.com]

You'd need the air on top of the wings to be moving faster than the air under to generate the lift, and ground movement air friction would make the air under them go faster if it had any effect at all.

[scendan.livejournal.com]

I don't think so. The ground beneath a plane moving on its own volition is still moving relative to the plane at the same speed that this conveyer would. Airflow over a plane's wing is dictated by the shape of the wing, with the curved top surface of the wing causing the air to move relatively more slowly than over the flat bottom surface. That's what creates lift. As long as air is moving over the wing at "takeoff" speeds, whether the plane is moving relative to the environment or not, you should still achieve lift.

Otherwise, a bird standing still and facing a headwind couldn't take off from a cliff, it would have to take a running start, and you see that happen all the time.

[grindbastard.livejournal.com]

So you want in on the action? :)

[scendan.livejournal.com]

LOL! I was all about it until I read your comment below and you threw me into profound self-doubt.

[xmoviebrainx.livejournal.com]

Go ahead and put me in the "will not work" category, though I'll be watching to see how it turns out!

[grindbastard.livejournal.com]

6 pack of Goose Island on it?!?! (Hexnut or Honkers!)

I'm anxious to see what happens too.

[xmoviebrainx.livejournal.com]

Absolutely, 6pack it is!

If I win I'll let you choose what comes my way, as long as it's some micro brew from your area.

[grindbastard.livejournal.com]

Cool...if I lose I'll find something good out of Bloomington's Upland Brewery.

I found this video early today that demonstrates the principle:

[xmoviebrainx.livejournal.com]

Wow, OK, I just now had time to watch that video.

It brings me back to my give and take earlier in this thread. The propeller pushes against the air, the treadmill (and the tires) against the ground. You can't separate the two forces. However, if the experiment went as I originally thought it would, and that is with the treadmill "pushing" the plane back on the tires so it is accelerating against the windspeed at a net zero relative movement to the surrounding ground it would not take off.

My assumption that one force would be counterproductive to the other instead of separating pitting the two forces against each other for sake of the experiment was incorrect. If the experiment is indeed like this one... yeah... you'll win =)

[grindbastard.livejournal.com]

It depends on how you think the wind will be generated. The propellor doesn't generate the movement of air on the wings directly. The propellor pulls the plane along (independently of the ground/wheels/friction!) and that creates the "wind" for lift.

[scendan.livejournal.com]

Well, here's where I get a little dicey on my concept. I would THINK that there would be air movement generated...I think. Hmmm. However, I might need to rethink that.

Hmmmm.

Well, may hafta eat crow.

*ponders*

[grindbastard.livejournal.com]

Oh...I agree that it WILL take off. I just think your theories are a little off. :)

[scendan.livejournal.com]

Hmmmm.

Well, in the end, it comes down to lift generated by airflow over the wings. So, there's gotta be airflow for the lift. That's the brass tacks.

[grindbastard.livejournal.com]

Aye.

I believe that even though the plane and conveyor are moving at the same speed, the plane can be moving forward. ...airflow...lift.

[xmoviebrainx.livejournal.com]

My understanding of how lift is generated is this:

The air speed flowing over the wing, above and below, is constant. The difference is that the top of the wing is curved, causing more distance to be travelled, making the air less dense. It then causes the denser air to press upward on the bottom of the wing trying to get to the less dense area above the wing.

Matt: this is where I get confused on the question of if it will take off. I must also say that I haven't seen the teaser for the new Mythbusters. If the conveyor belt is equal yet opposite of the plane's forward momentum that, in my mind, means zero forward momentum, zero air movement over the wings. Where is starts falling apart for me is that the wheels provide zero propulsion on take off above 5-10 mph on the runway. The engines push agaist the air, the wheels (and therefore the conveyor belt) against the ground. Assuming this is a propeller-driven engine (and each "wing" of the propellor following the same principles of lift as the main wing of the aircraft itself) how can you separate the two forces to test the myth?

[grindbastard.livejournal.com]

I haven't seen the teaser either. This is the closest thing to what I've seen...
http://mythbusters-wiki.discovery.com/page/Airplane+on+a+Conveyor+Belt+-+Get+Exclusive+Photos!?t=anon

I think what people are missing is that the plane and conveyor CAN be moving at the same speed, but the wheels will be moving MUCH faster. The drive is from the propeller and not the wheels, and people are assuming that the plane will stay in the same place because THE WHEELS have to be going the same speed as the belt and not the plane? Ya dig? I could be wrong though! Everyone here at work thinks so. :)

[scendan.livejournal.com]

Yes, what you said about how lift is generated is correct as far as I understand it as well. It's the same principle with bird wings as well--flat underside, curved topside.

Your second statement is interesting. Shoot...this is making my brain hurt, but it's fun!

[grindbastard.livejournal.com]

I found this earlier today :)

I can't wait to see what happens full scale.

[charasan.livejournal.com]

It's taking off.

The confusion here is, in a car, the wheels do all the work, turning to push against the road to propel the car forward.

In a plane, all the work is being done by the engines/propeller. The wheels are there so it can land and to reduce the friction against the ground so the plane can take off easier. And lift isn't a 100% yes or 100% no proposition, either. Soon as that plane starts moving, lift kicks in, planes gets a little lighter (relatively speaking). The belt might make the whole process take a bit longer before it picks up some steam, but it'll happen.

So what's going to happen is, the plane starts moving, belt starts moving, the wheels will get a real workout, but the plane takes off normal, because all that belt is doing is spinning the wheels.

[charasan.livejournal.com]

Incidentally, seeing the plane might help with the initial question, GB.

More modern planes do have more traditional wheel assemblies for taxing and such, and probably do have a little to do with the take off of the planes/jets :)

[grindbastard.livejournal.com]

Exactry.

[jack-the-tyrant.livejournal.com]

I have a bit of part time work that I do on composite materials in winglets in 747-777s.

The plane is going no where.

[grindbastard.livejournal.com]

You're assuming the plane will stay stationary...as in that it's unable to overcome the friction between it and its wheel bearings. In that case it won't have any airflow over the wings.

I think the plane will move forward regardless of the speed of the conveyor.

My money is that it will be plausible or confirmed that the plane flies.

[charasan.livejournal.com]

If you think about, the hardest part about a plane taking off is breaking from its initial state of rest. Most of the energy involved in movement is used in breaking that state. Since the belt isn't going to move until the plane does, this hurdle should ideally be exactly the same as a normal take-off.

[charasan.livejournal.com]

What'd I win?

[grindbastard.livejournal.com]

Depends who you bet against!

I've won two lunches at the Grand Traverse House of Pie, and a six pack of Goose Island Ale.

[merenda.livejournal.com]

I just remembered about this, and looked to see what happened on your blog...looks like I was wrong. :)

Glad I didn't bet LOL!