Airplane on Conveyor Belt Mythbusters 12/12

[Rondo777]

I fly r/c, both airplanes and Helis. I'm still trying to figure out a way to transport some rc toys on my Feejer

Enclosed trailer?

That would take the fun out of the ride, I may as well throw them in the back of my SUV like I do now

 

[mdisher]

Clearly the answer is '42'

 

[Rondo777]

I think we need to look at the precise wording of the original myth. I don't think the airplane is meant to move relative to the ground, only relative to the moving conveyer belt and the whole conveyer belt system is stationary to the ground.

So how does the treadmill do that?

I agree with looking at the wording of the myth. I personally think that if the myth is actually what we've been discussing that its too stupid to air on mythbusters. Its like the Myth that the world is flat, may be they'll do that one next?

 

[FJRottie]

A giant whipping cable will not cut a person in half.

 

[Rondo777]

A giant whipping cable will not cut a person in half.

BUSTED! Cool effect in that movie Ghost Ship though.

 

[xviper]

I think we need to look at the precise wording of the original myth. I don't think the airplane is meant to move relative to the ground, only relative to the moving conveyer belt and the whole conveyer belt system is stationary to the ground.

So how does the treadmill do that?

Do what? I take it you're not asking how to bolt the conveyer belt system to the ground, so I'll answer the other one.

You need the propeller pulling on the plane to counteract the friction of the wheels and tires on the belt surface. Without the propulsion system of the plane operating, the moving belt would just push the plane off the end of the system. Without the belt moving, the propulsion system of the plane would just pull the whole plane off the other end of the tread. The 2 things are going on at once. Otherwise, what's the point to it all?

I believe the essence of the myth (correct me if this isn't the case) .................. Is it possible for an airplane on a moving conveyer belt (speed increasing), using the plane's propulsion system to hold it in a stationary position on that conveyer device, lift off?

 

[El Gordo]

Hmmm I think too many bikes are parked for the winter?

 

[madmike2]

Is it possible for an airplane on a moving conveyer belt (speed increasing), using the plane's propulsion system to hold it in a stationary position on that conveyer device, lift off?

That's how I understood the premise and why I gave the answer I did.

 

[xviper]

Is it possible for an airplane on a moving conveyer belt (speed increasing), using the plane's propulsion system to hold it in a stationary position on that conveyer device, lift off?

That's how I understood the premise and why I gave the answer I did.

And you were correct. That's the way I see it, too.

To put it another way so that perhaps more people will understand it ..........................

First, the treadmill is NOT being used as a catapult. That is, the tread is moving from front of plane to the rear, NOT the other way around.

Put an airplane (not a helicopter or a vectored flight airplane) on a treadmill that is bolted to the ground. There is no natural wind. Start up the plane's engine and increase the throttle to max. The plane will begin to move forward, BUT you start the treadmill and increase it's speed to keep the plane more or less in the same place relative to the solid ground. Will the plane lift off (or take off, if you will)?

My answer: It won't.

OK, this has been fun, but let's watch the show (if indeed it's on the show). Gotta go to work now.

 

[tinpusher]

I know I have participated exstensivly in this thread, so I'm not one to talk, but it reminds me of this........

WARNING : NOT EVEN CLOSE TO BEING POLITICALLY CORRECT <----Link

 

[Scythian]

The best thing about this thread is that now I have a basis to evaluate peoples' opinions on technical and riding issues!

And dogs can't look up....

 

[ponyfool]

Put an airplane (not a helicopter or a vectored flight airplane) on a treadmill that is bolted to the ground. There is no natural wind. Start up the plane's engine and increase the throttle to max. The plane will begin to move forward, BUT you start the treadmill and increase it's speed to keep the plane more or less in the same place relative to the solid ground. Will the plane lift off (or take off, if you will)?
My answer: It won't.

You are correct that it won't. But the point I think you are missing is, the treadmill can't do ANYTHING to keep the plane "more or less in the same place relative to the solid ground" unless there is something physically tethered from the ground (not the treadmill) directly to the plane. Well, unless the wheels are acting as a brake.
Even if the plane's propulsion system triggered the treadmill's speed, the thrust of the airplane isn't being derived from the treadmill or the plane's contact with the ground, it is being generated by the engines, which is using airflow, which is completely independent from the ground. Thus, when the propulsion system has enough thrust to move the plane 5 mph, and the treadmill starts to run at 5 mph, the plane will still move 5 mph in relation to the ground. The wheels of the plane on the treadmill will either skid (if there's enough propulsion) or the wheel speed will increase to 10 mph (5 mph for the thrust generated, and 5 mph additional for the treadmill speed).

 

[twowheelnut]

AAAAAAAAAAGH!!!! Please stop! Puh-leeeeeeeeeeeeeeeze! "Stop, or I KeeL YOU!"

 

[ponyfool]

AAAAAAAAAAGH!!!! Please stop! Puh-leeeeeeeeeeeeeeeze! "Stop, or I KeeL YOU!"

LMAO. Sorry to resurrect it, but stupidity needs to be addressed.

 

[Bearly Flying]

Ponyfool is 100 % CORRECT....

 

[Toecutter]

Did anybody actually watch the show?

 

[wallypiper]

As a pilot and aircraft owner for almost 30 years I can attest to the fact that: An airplanes ability to fly is 100% dependent on AIR SPEED (The measured speed of the air over the wing) Unless the tread mill is on the back of a truck moving at the appropriate speed for flight of the plane in question, that plane aint going any where. GROUND SPEED (The measured speed the aircraft is moving along the ground) is completely irrelevent flight. If your in a plane that can fly at 40 knots and the wind is blowing 40 knots directly at the plane then you can fly with no power and have no forward motion(ground speed) The airspeed indicator in the plane will show 40 knots. I used to live in Daytona Bch and on really windy days I would take my plane along the beach and fly backwards. Head wind of 50knots and my plane was capable of flight at 33 knots. I was actually moving backwards at a ground speed of 17 knots, really trippy to people watching from the beach.

While I completely understand most of this post and fully understand that a plane capable of flying at 30 knots can fly "backwards" relative to the ground in a 40 knot headwind, this statement baffles me:

If your in a plane that can fly at 40 knots and the wind is blowing 40 knots directly at the plane then you can fly with no power

How are you going to fly with no power? Your power might consist of a cable holding you stationary relative to the ground. But you have to have power to overcome the 40 knot wind or your plane will just move backwards at 40 knots or however fast it can move given the friction of the landing gear on the ground. In order to hover or move backwards over the beach, you were applying just enough power to balance the 40 knot wind, or slightly less to back up. If you can fly without power (gliders aside, since they need a powered tow to get them in the air to begin with), you should start an airline because you will eliminate the biggest operating cost (fuel). Of course, since your unpowered flights don't actually go anywhere but just hover in place, I don't suppose a lot of people will buy tickets.

As for the damn treadmill, if the myth is based on the treadmill going fast enough to balance the thrust and the only way for the treadmill to act on the plane is by spinning the wheels, its going to have to go very fast or you're going to have to limit the thrust the airplane is allowed to develop to a tiny amount, not sufficient to get it off the ground with or without the treadmill. Think a plane could take off from a frictionless surface? Of course it could because it does not depend on friction with the surface it's on for movement.

Its a silly myth not really worthy of a Mythbuster's test because its based on a misconception - that airplanes move forward by pushing against the ground. Its like a perpetual motion machine. It doesn't work because you have to suspend a law of nature (every action has an equal opposite reaction) for it to work. (Perpetual motion machines don't work for a variety of reasons, depending on their design - friction, thermal dynamics, gravity, entropy.)

Now the water heater launches - those were awesome. That was the best test they've ever done.

 

[Fred W]

Did anybody actually watch the show?

Yes, I did.

It gets even better. Here is a listing of yesterdays show on the Discovery.com website:

MythBusters Air Plane Hour

TV-PG

Jamie and Adam take wing to test if a person with no flight training can safely land an airplane and if a plane can take off from a conveyor belt speeding in the opposite direction. Tory, Grant, and Kari jump on some Hollywood-inspired skydiving myths.

I watched the show. They did all the other things mentioned in the above quote but did not even mention conveyor belts.

Was this all a big hoax?

 

[xviper]

Well, unless the wheels are acting as a brake.

The wheels are only resisting spinning by friction of the bearings and friction of the tires on the treadmill. That's the only "braking" there is.

when the propulsion system has enough thrust to move the plane 5 mph, and the treadmill starts to run at 5 mph, the plane will still move 5 mph in relation to the ground.

I disagree. The plane would be moving at 5 mph relative to the treadmill track, which is moving under it. It remains stationary relative to the ground that the treadmill is bolted to. (ie, 0 mph to the ground)

The wheels of the plane on the treadmill will either skid (if there's enough propulsion) or the wheel speed will increase to 10 mph (5 mph for the thrust generated, and 5 mph additional for the treadmill speed).

Why would the wheels skid? They're rolling with the treadmill. No brakes are applied. Why would the wheels be spinning at 10 mph when the treadmill is running at 5 mph? The wheels are still touching the treadmill track. If you add enough thrust for 10 mph, the treadmill speeds up to 10 mph. The plane stays stationary relative to the ground. It's not moving forward or backwards. The treadmill keeps in sync with what the plane is trying to do. If you're standing on the ground next to the treadmill with the airplane on it, the plane remains right beside you.

Was this all a big hoax?

It probably was. I can see the OP watching all of us beat the crap out of each other and having a great laugh.

 

[Bounce]

Did anybody actually watch the show?

yes. watched it last night. nothing to do with treadmills. some sky diving and talking in an unskilled passenger to a landing (using a simulator).