Mythbusters – Plane on a Treadmill

The amount of attention this little problem has attracted on the intertubes proves two things:
1.  People have far too much time on their hands (myself included), and
2.  People generally don’t know shit about even reasonably simple physics.

The proposition is this:  An airplane sits on a treadmill which operates in such a way as to counter the forward motion of the airplane’s wheels.  Thus, even as the propellers (or jet engines, as the case may be) attempt to move the aircraft down the runway, the treadmill (running in the opposite direction) keeps the plane stationary relative to the rest of the world.
Question:  Can the plane take off?

Now, some geniuses like to point out that the airplane is not powered by its wheels.  The power, they insist, comes from the jet engines (or the propellers).  Thus, the plane can take off.  These people are twits, who when asked will further assert that LIFT is similarly created by the jet engines (or the propellers).

LIFT, without which no plane is getting a fucking hair’s width off the ground, is created by air moving over the wings…or the wings moving through the air (a distinction without a difference).
If the plane is stationary relative to the air around it – a feature built into the premise of the argument – then it cannot develop lift and, consequently, cannot take off.

On the Mythbusters episode in which they tackled this problem, Adam and Jamie attempted to drag a sheet of paper beneath a remote-controlled plane.  Sadly, as the footage clearly shows, they were unable to match the speed of the paper to the speed of the plane.  The plane was faster, developed forward motion over the paper sufficient to create lift and permit take-off.  Pfft.  This merely proves a principle Orville and Wilbur worked out in Kitty Hawk about 1903.

Here’s the thing, kids.  Lift comes from the wings, not the engines (or the wheels).  It is created by airflow over the wings.  You may confirm this by asking any pilot what happens when their airspeed drops to zero.
All the thrust and propellers in the world won’t help you if you aren’t MOVING FORWARD THROUGH THE AIR.  In point of fact, a headwind of a few hundred miles per hour would work equally well in theory – one only need watch seagulls soaring in place on a windy day to figure that out.  Note the gulls do not move relative to the beach, nor flap their wings to stay airborne.  They simply ride the wind, taking lift from the moving air rather than generating forward motion though stable air.  On calm days, there’s much more flapping and no hovering.  And, of course, relatively speaking, wind is the same thing as forward motion through a stable air mass.
One might also note which way the fucking model is aimed when tested in a wind tunnel for LIFT.
Tailwinds.  Not helpful.  Fuck me.

This is not dissimilar to the old argument that says, “Guns don’t kill people, people kill people.”  To which Chris Rock replies, “Don’t be fucking stupid.  Guns don’t kill people…BULLETS kills people.  Guns just make the bullets go fast.”

Well, propellers and jet engines don’t provide lift.  They just make the wings go fast.  Take away the guns and bullets are harmless.  Take away the forward motion and so are wings.

Now, and this is important, the premise of the treadmill question demands that the plane is NOT moving forward through the air surrounding it.  No forward motion = no airflow = no lift = no take-off.
If you think otherwise, you might further consider how they get aircraft off carrier decks.  They catapault the fucker up to speed using a huge steam-powered drag line.  They DON’T just roll the jet over to the edge of the deck, fire up the engines and magically zip off into the wild blue yonder.  In fact, they turn the whole damn carrier INTO THE WIND.  Now why do you think they might do that?
If you STILL think stationary aircraft can take off if only you get the propeller turning fast enough, castrate yourself.  You’re too fucking stupid to breed.

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9 Responses

  1. Other geniuses will point out that “it’s” is the contraction of “it is” and not the possessive of “it.”

    Twat.

  2. Those people aren’t geniuses – they’re grammar Nazis. Especially hard to distinguish in your case, what with the SS uniform, toothbrush mustache and goose-stepping.
    Just one twats opinion.
    Zeig Heil, Ace.

  3. Turns out I may have misunderstood the problem.
    It would seem that it is not necessarily built into the premise that the reverse treadmill MUST counter the “forward motion” of the plane. Some have stated the problem in a way that the treadmill merely counters the non-powered wheels as they roll in response to the forward thrust (which isn’t the question I started out with at all).
    This now seems to me to be open to at least two interpretations – one from a physics perspective, the other from what might be termed an engineering perspective.
    In terms of force vectors, it would seem to be an impossibility to have the treadmill counter the forward thrust of the engines – it would, speaking in terms of the friction of the wheels vs. the thrust of the jets/propeller, simply result in the wheels spinning faster and faster and really very much faster, even while the plane developed forward motion through the surrounding air. Whether it could get up to take-off speed would depend on a few other variables which one can vary to one’s heart’s content (or until you get the result you want).
    In any case, if the premise were as I thought it were, the question of getting airborne is just silly.
    I hate poorly defined thought experiments. HATE’EM.
    Anyone who followed my directions in the post and castrated yourselves, you may now uncastrate yourselves. Oh…well…sorry about that.

  4. Your interpretation (that the treadmill must counteract the forward motion of the plane) is physically impossible. No matter how fast the treadmill is moving, the engines are thrusting against a stationary column of air, and this will only result in forward motion.

    The physically realistic interpretation is exactly what they did on mythbusters. The plane thrusts against a stationary air column, moves forward and takes off. What the wheels are doing is irrelevant, as long as the plane is moving forward in the air.
    We both agree on that, what’s important for the plane taking off is that it’s moving forward in the air. But your interpretation that the problem states the treadmill will counteract the forward motion of the plane is not possible. The plane will experience a forward acceleration no matter how fast the treadmill moves the opposite way. The plane is thrusting against the air, not the ground.

    I suppose it’s just two interpretations of an ambiguous problem, but I would consider the physically possible interpretation to be the preferable one.

  5. Oh wait, you already addressed that interpretation in the comments.
    Nevermind 😛

  6. @Jason

    Yeah…so much has to do with how the premise is presented.
    That’s where the engineers start getting really excited about the argument. “…and how to you propose to do THAT?”
    Puts me in mind of the guy I once heard explaining Schrodinger’s Cat. He swore a cat was literally placed in a box, and the result was proof that time travel is possible. He was trying to impress some chick in a bar. I wish now that instead of walking away shaking my head, I’d stayed to find out if it worked (picking her up, not time travel)…
    HEY! If I get a cat and a box, I can go back and find out!

  7. @Jason (again):

    It’s not impossible. Unless you’re one of those engineering sorts…pfft.
    You just need an infinitely fast treadmill, wheels that won’t melt, and determination.

  8. I so want to strap wings on Hawking’s chair and let him be the first to ride the infinitely fast treadmill.

  9. Seriously? People still aren’t getting this?

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