Mythbusters — TONIGHT!

Don’t forget that tonight’s episode of Mythbusters promises to answer the question about whether or not an airplane on a treadmill could achieve flight.

UPDATE: Full spoilers and discussion of the episode after the break.

The plane took off, as I believe I guessed and for all the right reasons. That is, the power is generated by the propeller and NOT the wheels.

But you know what? This is the internet. This episode of the Mythbusters will be further debated until the end of time. I guarantee you that there are those who believed the plane would not take off who are explaining why the experiment was flawed. They’re probably saying there was some give in the tarp that they used as a conveyor belt, thus gaining traction for the plane and derailing the experiment. Or something. I have no doubt this is NOT the end of it, though it works for me.

Here, let me quote me for a second, from last November:

I think I have it. The plane WILL take off. The power of the plane’s movement come not from how fast the wheels are going. That’s what a car does. A plane catches air from the propulsion in its wings — prop place or jet place. The fact that the wheels are negated in the distance they travel doesn’t matter one bit. The whole plane is moving above it.

And they used the car analogy on the show, to boot.

Adam from Mythbusters hangs out at MetaFilter.  It’ll be interesting to see if the debate rages on there in the morning.

One thought on “Mythbusters — TONIGHT!

  1. Yeah, this is clearly not going to stop discussion/argument. What I wasn’t expecting is why — that the myth seems inadequately defined. From my point of view, they didn’t even implement the myth properly.

    Their premise is that the plane “is moving at takeoff speed” on a belt moving at the same speed in the opposite direction, that the belt is “matching the plane’s forward speed in reverse”. To me this meant the plane is moving relative to the belt at takeoff speed, and so by definition the plane would seem stationary relative to someone standing just beside the belt. That’s why I got so hung up in your earlier post in boggling over how a plane could possibly take off with no airflow over the wings.

    The answer is that instead of what I thought was the obvious meaning of the premise, they apparently meant that the plane’s engine and prop are running at the rate that would under normal conditions be just sufficient to take off. Thanks to the fact that as you say the prop acts on the air, not the ground, this means that the plane will get up to the same takeoff speed relative to the air (and twice takeoff speed relative to the belt) and of course have the usual airflow over the wings and take off with no problem.

    It seems that if the wheels are sufficiently free-spinning (that there’s sufficiently little friction) then what I thought was the premise is next to impossible to enact — the belt will not be able to exert any force on the plane, so it’ll refuse to stay stationary relative to a person next to the belt. So there’s no question of take off or not take off, the situation basically just can’t occur. I admit that I missed that when thinking about the myth. I guess I was figuring they could run the prop at a rate just fast enough to cancel that belt friction pulling it backwards and not any faster — I didn’t think the friction would be so tiny.

    But I was close to yelling at my TV by the end of the episode — Jamie, if the plane moves forward off the end of the belt then the belt is clearly not “matching the plane’s forward speed in reverse”. :-) Now, for what it was, their implementation was fun and nicely done, but to me it seemed like a nice look at something different from what they said they were going to test. Clear wording is definitely a prerequisite for busting myths. :-)

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