Airplane on a treadmill

Will the airplane take off?

  • Yes

    Votes: 4 25.0%

  • No

    Votes: 10 62.5%

  • I have no idea

    Votes: 2 12.5%
  • Total voters
    16
Luis G

Luis G

<i><b>Problemator</b></i>
Staff member
That's typical over here. Record for a topic to go off-topic is 1st reply :lol:
 
Gato_Solo

Gato_Solo

Out-freaking-standing OTC member
Nope. Physics applies to this, so there really is no need. Planes can't fly unless they have air moving over their wings...Harrier and F-35 not-with-standing.
 
L

loon_B4ll00N

New Member
I didn't see the episode, but somebody told me about it. They said the pilot of the airplane thought it'd sit there like a rock. Wow. ..and he's a licensed pilot?

-Makes me wanna laugh, and re-evaluate the stupidity of perfesshunal peeple!

There. I said it. I blanket-stated all professional people as "stupid"...(esp pilots):la:

It's an "apples and oranges" comparison... unless:

Okay - just for the sake of argument: When that particular plane reaches lift from a regular runway, what was the speed in RPM's of the wheels? Is that then, the "speed" to match? Or is it the "airspeed" that they were trying to attain? Somebody said in a post before that an airplane is not a helicopter.. (Made me laugh also!) Well, yes it is! It's a Horizontal helicopter..
(or a helicopter is a vertical plane...) The medium thru which the craft moves is air, so the ground speed has nothing to do with its lift. A plane "flies" due to the differential of pressure above and below the airfoil. Surely, without proper airspeed, there's not enough air pressure under the wing to overcome the negative pressure then caused by the shape of the airfoil to achieve lift. I would assume that no tug or winch or pickup truck or whatever could possibly pull that tarp at a fast enough rate to make the plane "stay in one spot", while the airscrew is working in an entirely different medium!

If the airplane was hooked to the rafters in the sky(God's ceiling?) No amount of pulling at the tarp would cause the plane to move backwards, engine running or not. Because The skyhook has nothing to do with the ground road.

Now, if say the bearings in the wheels got hot and ceased up, then you'd have a bit more force pulling on the airframe (drag) which would cause the engine to werk harder to try to achieve lift. If you have enough drag, the plane won't achieve airspeed, not even if you cram the throttle to the max (WEP!) and lean out the carbs... But we're not talking about drag, we're talking about "speed". I just don't know what the fuck "speed" we're talking about... Airspeed is totally different from groundspeed, and

Wait a minute! Why in hell is "airspeed" a word, and "groundspeed" isn't, according to my spelcheck?

(speaking of OFF TOPIC):sex2::hairbang:
 
L

loon_B4ll00N

New Member
Oh, and one more thing: The poll is bunk, cause there's no option for "Not enough information" - so I'd have to conclude that I'd have to vote "I have no idea"! *which makes me sound ignorant, so I guess I am ignorant*

I hate these fucking polls:banghead:
 
L

loon_B4ll00N

New Member
oh, crap! I just re-read the first post. They're asking about a jet engine! That changes everything (no) same physics apply, except for my comment on carburetors and possible war emergency power.

What'd happen (I have no time to figger this out, I gotta go to werk) if ya took two identical planes, each facing opposite directions, but the one hooked to an infinite tarp lying on the ground (in a perfect vacuum, with no rolling resistance what-so-ever..etc..)(just the tarp in the vacuum otherwise it'd change the whole make-up again), while the other is on that tarp trying to take off in the opposite direction?

screw this I have to go to work....:rainfrow:
 
BeardofPants

BeardofPants

New Member
BeardofPants said:
*sigh* There are two different questions. This is the straight dope question: "Imagine a plane is sitting on a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.

Can the plane take off?"

The answer to that question is YES, the plane will take off as per the straight dope column that was posted up by the thread starter. HOWEVER, according to the parameters set up by THIS thread in which the treadmill will match what the plane does in terms of speed, the plane will never gain acceleration to take off.
Click to expand...


mythbusters said:
Myth Description: Can an airplane on a conveyor belt running in opposite motion to the airplane's tires at the same speed keep the plane from taking off?
Click to expand...

*vindication*
 
BeardofPants

BeardofPants

New Member
Thursday, January 31, 2008

Airplane on a treadmill

I created this blog specifically to make this post. It may be the only post I ever write, but since human ignorance is seemingly unbounded, perhaps it won't be.

I thought that today would be a monumental day for this topic. Today, the Mythbusters debuted their long-awaited "Airplane on a treadmill" episode. For years, physics teachers around the world have cringed in horror at heated internet debates concerning a ludicrous thought experiment. Sadly, half of them recoiled in disgust at the correct arguments. Forum posters signed their names with such epithets as "Ph.D. Aerospace Engineer" and "20-year pilot." Somewhat tellingly, these ego-boosters were most often employed by those delivering the wrong answers. Mythbusters finally attempted to end the insanity by performing the experiment themselves.

AND YET...

The debate rages on. Even after being shown seemingly conclusive evidence of the other side's argument, forum-goers from near and far continued to staunchly defend their own theories.

Here and now, the debate will end. I intend this long-winded article to be the definitive answer to the great AOAT conundrum. No further debate is necessary - simply direct the ignorant people to this page, tell them to read it, and let's all get on with answering more intriguing questions, like does P = NP?

For those of you just joining us, "Airplane On A Treadmill" is a thought experiment in physics. Some consider it a litmus test for assessing one's knowledge of airplane physics. In its most basic form, the experiment is worded thusly:


A plane is standing on a large treadmill or conveyor belt. The plane moves in one direction, while the conveyor moves in the opposite direction. This 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 plane take off?

The question suffers from many rewordings that muddle much of the debate about the thought experiment. The basic idea is that there's a plane, on a treadmill, and we're going to run the treadmill backwards in an attempt to stop the plane from taking off. And here, at the very beginning of this explanation, is the definitive answer. There are in fact two correct answers to this question:

-No, the plane can't take off.
-Yes, the plane can take off.

Fooled you! But that's just the point. The experiment is meaningless, and the passionate internet debates more so, if we cannot agree on what is truly meant by the question. But don't worry, I won't pull a Lost on you - I do intend to give a truly airtight answer later on. For now though, we need to debate semantics.

Really, we do.

You see, the AOAT confusion all arises from misses - misconceptions, misinterpretations, and misunderstandings. Consider three rewordings of the question:

1) An airplane is sitting at rest on a very powerful treadmill. You are at the controls of the treadmill, while I am at the controls of the airplane. On some signal, I begin to attempt to take flight in the plane, and you attempt to match my speed to try to keep me stationary. Will the plane take off?

2) An airplane is sitting at rest on a very powerful treadmill. You are at the controls of the treadmill, while I am at the controls of the airplane. On some signal, I throttle up the airplane and you turn on the treadmill, and we conspire by our joint effort to try to keep the plane stationary relative to the ground. Will the plane take off?

3) An airplane is sitting at rest on a very powerful treadmill. You are at the controls of the treadmill, while I am at the controls of the airplane. On some signal, I attempt to take flight in the plane, but you match my speed with the treadmill and keep me stationary relative to the ground. Will the plane take off?

Here are the absolute, 100%, bet-your-life-on-it answers to these rewordings:

Yes.
No.
Whoever asked this question is an idiot.

And that's about all this debate comes down to, folks. If we could all agree on one set of rules for the thought experiment, then we ought to be able to make the explanation of the answer clear. As it stands, normally one side has interpretation (1) in mind, and argues vehemently with someone else who has interpretation (2) in mind, and the whole thing blows up into a senseless squabble.
Click to expand...

from: http://www.airplaneonatreadmill.com/
 
chcr

chcr

Too cute for words
loon_B4ll00N said:
oh, crap! I just re-read the first post. They're asking about a jet engine! That changes everything (no) same physics apply, except for my comment on carburetors and possible war emergency power.

What'd happen (I have no time to figger this out, I gotta go to werk) if ya took two identical planes, each facing opposite directions, but the one hooked to an infinite tarp lying on the ground (in a perfect vacuum, with no rolling resistance what-so-ever..etc..)(just the tarp in the vacuum otherwise it'd change the whole make-up again), while the other is on that tarp trying to take off in the opposite direction?

screw this I have to go to work....:rainfrow:
Click to expand...
Neither an airplane nor a jet take off in a vacuum.
1. Need oxygen to run.
2. Need air moving over the wings to generate lift.
:shrug:
A rocket, OTOH...
 
JJR512

JJR512

New Member
1. An airplane's wings need to have airflow over their surfaces to generate lift. The wings are the sole component of an airplane that generates lift, not counting directed thrust, such as the Harrier or Osprey.

2. An airplane's engines generate thrust. This is true of jet engines, propeller engines, rocket engines, whatever. Thrust pushes the airplane forward through the air, not on the ground. This is an important distinction.

3. The wheels of an airplane are not powered. They simply roll on the ground (or treadmill, as the case may be).

The treadmill does't match the speed of the airplane's wheels. It's the other way around: The airplane's wheels match the speed of the treadmill. The wheel are free-spinning; they are not powered. If the airplane's engines begin to generate thrust and the airplane would begin to move forward, at, say, 10mph, and the treadmill began to roll backwards at 10mph, here is what would happen:

The airplane would continue moving forward (relative to the space around it) at 10mph. It's wheels would spin at the same speed as if the airplane were moving at 20mph on a fixed non-moving surface.[/i]

But you don't have to take my word for it. As noted previously, the MythBusters have tackled this. Look here: http://mythbusters-wiki.discovery.com/page/Plane+on+a+Conveyor+Belt
 
Nixy

Nixy

Elimi-nistrator
Staff member
I haven't read this thread but when I opened it all I saw was a statement saying all professional people are stupid...I think I shan't get involved in this...lest I lose my cool.
 
Professur

Professur

Well-Known Member
The sad part of this conversation is that some folk simply can't accept that the mere precept is impossible. A conveyor belt could never match the wheel's speed. The wheels are moving, not with relation to the belt, but in relation to the frame supporting the belt. Belt speed is irrelevant.
 
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