Mythbusters will finally test...

[SarichFan]

Originally Posted by llama64

Why would it EVER stay stationary? Seriously, try and explain how the plane would stay in one spot without it being tethered.

What am I Dr. Emmit Brown? Think of someone running on a treadmill... Are they constantly moving forward?

The plane moved forward, of course it's going to take off.. It's getting wind under the wings.

I'm no scientist but that's kind of what I expected, I expected The Plane's propeller to pull it along but eventually the speed of the plane would match the speed of the treadmill, and that's where things would get interesting..

All the treadmill did was slow down the plane slightly.

It was 1.21 Gigawatts of Dissapointment...

[photon]

Originally Posted by Hemi-Cuda

"The myth is that a plane on a conveyor belt will be able to take off"

so are there 94 CP members who were totally wrong, or just confused on the poll question as i was? i thought the myth was that the plan WILL take off (like the poll says) so i voted confirmed. but on the show they said the myth was that the plane WON'T take off, so in reality it's busted

i demand a repoll

Ah good point, that is worded wrong, I just copied and pasted it from a source and didn't read it

So the poll results are null and void! And we can't repoll because everyone will just pick confirmed.

[llama64]

Originally Posted by SarichFan

What am I Dr. Emmit Brown? Think of someone running on a treadmill... Are they constantly moving forward?

The plane moved forward, of course it's going to take off.. It's getting wind under the wings.

I'm no scientist but that's kind of what I expected, I expected The Plane's propeller to pull it along but eventually the speed of the plane would match the speed of the treadmill, and that's where things would get interesting..

All the treadmill did was slow down the plane slightly.

It was 1.21 Gigawatts of Dissapointment...

Aside from the awesome reference to Dr. Brown, what you described is exactly the point. As the "myth" is described, the plane would move forward and would take off. There is nothing in the description that would ever cause it to remain stationary. Which is why I'm wondering what would make you think it would stay in one spot.

[SarichFan]

My own imagination I guess..

[BlackArcher101]

Not sure how the wording invalidates the results. I think the way it is now is clear. If we switched it to read "won't takeoff", 63% would have chosen "confirmed" instead.

Unless of course no one actually read the question on the poll and assumed it was something else.

[Hack&Lube]

Originally Posted by llama64

Aside from the awesome reference to Dr. Brown, what you described is exactly the point. As the "myth" is described, the plane would move forward and would take off. There is nothing in the description that would ever cause it to remain stationary. Which is why I'm wondering what would make you think it would stay in one spot.

Not at all, a plane on a conveyer belt moving at sufficient speed and with wheels that could withstand the forces acting on it will remain stationary. The myth as described and then executed by these guys totally misses the spirit of the myth in my opinion. The point is that it's not the distance covered that allows a plane to takeoff but the air moving over the wings. The way it was executed, the wings were moving faster, relative to the air than the plane was moving relative to the ground, therefore it took off. I think spirit of the myth is partly in reducing runway length, etc. This way just takes longer but you still take off.

[Iowa_Flames_Fan]

Originally Posted by BlackArcher101

Not sure how the wording invalidates the results. I think the way it is now is clear. If we switched it to read "won't takeoff", 63% would have chosen "confirmed" instead.

Unless of course no one actually read the question on the poll and assumed it was something else.

I voted the wrong way... is there any chance I can now claim that I was confused by the wording?

TBQH, I thought they did a very good job of explaining the myth on the show--and after they tested it, I felt pretty dumb for having been skeptical in the first place. I lost a bet to my wife too--that hurt.

[Hack&Lube]

Why is a stupid mythbusters segment causing us so much consternation? Maybe this is why I never visit the Mythbusters forum to read from the "fans" that send in things to the show. I used to love this show and think it was my 2nd dream job in the world (first would be to be on Top Gear) but now after this thread, I hate mythbusters and don't feel like watching it ever again.

[photon]

Originally Posted by BlackArcher101

Not sure how the wording invalidates the results. I think the way it is now is clear. If we switched it to read "won't takeoff", 63% would have chosen "confirmed" instead.

Unless of course no one actually read the question on the poll and assumed it was something else.

Lol well I voted confirmed because I knew the plane would fly, so I didn't vote according to my own question

Originally Posted by Hack&Lube

Not at all, a plane on a conveyer belt moving at sufficient speed and with wheels that could withstand the forces acting on it will remain stationary.

The gear aren't through the centre of gravity it'll cause the airplane to rotate and flip it.

Like I said before, the myth talks about the conveyor moving at the same speed as the plane in the opposite direction, not some high speed.

The way it was executed, the wings were moving faster, relative to the air than the plane was moving relative to the ground, therefore it took off.

But how fast the plane is moving relative to the ground doesn't have anything to do with flight, it's all about airspeed.

I think spirit of the myth is partly in reducing runway length, etc. This way just takes longer but you still take off.

It's not about reducing runway length at all, the question is will the plane take off or not.

[RogerWilco]

This was busted a long time ago, there are numerous web pages that show the plane will take off. The plane isnt propelled foward by its wheels, it is propelled forwards by its prop.

[ricosuave]

This is on tonight in Calgary at 8pm on Ch 35.

[Locke]

Did anyone watch this?

I only caught the tail end of it, but the plane took off.

[Textcritic]

Originally Posted by RogerWilco

This was busted a long time ago, there are numerous web pages that show the plane will take off. The plane isnt propelled foward by its wheels, it is propelled forwards by its prop.

This is precisely the point that the show made at its conclusion. Jamie Hyneman said just before pronouncing judgment: "no matter how many times you try to explain it, people just can't seem to grasp that a plane's engine controls its airspeed and not the wheels"...or something to that effect.

I thought the myth would work out another way as well. But watching last night caused me to wonder: If the statement about airspeed is true, then theoritically, no matter how fast the treadmill is going, the plane's wheels will always move faster in the other direction because of the plane's airspeed. In other words: it would be impossible to render it stationary on a treadmill, outside of a tether. Is that right?

[SebC]

Originally Posted by Textcritic

This is precisely the point that the show made at its conclusion. Jamie Hyneman said just before pronouncing judgment: "no matter how many times you try to explain it, people just can't seem to grasp that a plane's engine controls its airspeed and not the wheels"...or something to that effect.

I thought the myth would work out another way as well. But watching last night caused me to wonder: If the statement about airspeed is true, then theoritically, no matter how fast the treadmill is going, the plane's wheels will always move faster in the other direction because of the plane's airspeed. In other words: it would be impossible to render it stationary on a treadmill, outside of a tether. Is that right?

Nope. There is some friction through the wheels. Thus if the treadmill was going very, very fast, that frictional force would be enough to equal the thrust generated by the plane's engines.

[photon]

And assuming the landing gear was designed to take that kind of force, which it probably isn't. And since the force would be on the landing gear rather than through the plane's centre of gravity it would probably flip the plane too.

[ken0042]

In my mind they did the test "wrong"; or at least not what I thought they were going to test. They may have well been testing to see if you can have an airplane takeoff with a tailwind; because that's essentially all they did.

As you can see the plane is still moving past the stationary pilons; at about the ~30 mph or whatever they said was takeoff air speed. Seeing as we know the winds were calm (as the tarp was blowing in the slightest breaze), basically they were testing if the plane could take off with a higher relative ground speed.

[Bring_Back_Shantz]

Originally Posted by ken0042

In my mind they did the test "wrong"; or at least not what I thought they were going to test. They may have well been testing to see if you can have an airplane takeoff with a tailwind; because that's essentially all they did.

As you can see the plane is still moving past the stationary pilons; at about the ~30 mph or whatever they said was takeoff air speed. Seeing as we know the winds were calm (as the tarp was blowing in the slightest breaze), basically they were testing if the plane could take off with a higher relative ground speed.

Yeah, and that is the whole point of the myth.
People that think it won't take off are under the impression that the plane will remain stationary with respect to the ground, and that is why it won't take off.
This simply isn't true. The sticking point of the myth is that the plane will always be able to take off, because it will always be able produce thrust and the wheels have nothing to do with this.

The only way for the plane to remain statinary is if the static coefficient of friction of the wheels to the converyer belt is higher or equal to the thrust to weight ratio of the plane.
This is because the maximum value of friction on the wheels is equal to the static coefficeint of friction (we'll call this Cs) * weight of the plane, so for the plane to remain in place:
ie if thrust <= Cs*W

And for this to happen the friction in the wheel bearings has to be high enough that the wheels are just about to break loose from the conveyer belt and start to skid, and in a working plane this is never going to happen (barring of course some ludicrous speed on the treadmill).

So yeah, the tested the myth and bused it. The myth isn't really about if the plane can or can't take off, it is if the plane will remain stationary with respect to the ground (and in the case of no wind, have zero airspeed).
That's what they tested, and that's what they proved, that yes, the plane will take off, because the treadmill will never be able to keep it stationary.

[Russic]

youtubed

Sorry, I don't know how to embed.

[photon]

Originally Posted by ken0042

In my mind they did the test "wrong"; or at least not what I thought they were going to test. They may have well been testing to see if you can have an airplane takeoff with a tailwind; because that's essentially all they did.

As you can see the plane is still moving past the stationary pilons; at about the ~30 mph or whatever they said was takeoff air speed. Seeing as we know the winds were calm (as the tarp was blowing in the slightest breaze), basically they were testing if the plane could take off with a higher relative ground speed.

I don't see what you mean when they tested to see if the plane could take off with a tailwind. Ground speed means nothing to an airplane.

[ken0042]

Pho- in the "control" test they had the plane take off @ 30 mph. Because there was no wind, the air speed and ground speed were the same. All they did to test the "myth" was start with a negative ground speed of the same 30 mph, and let the plane get up to a ground speed of 60 mph (relative to the treadmill); giving it the nessesary 30 mph needed to get enough lift to take off. So to answer the question, does the ground speed affect the ability for a plane to take off? No, of course not. I could have told you that.

The bottom line is a plane takes off when there's enough air speed to generate lift. Doesn't matter what the gound speed, wind speed, or anything else is. Once that plane hits an air speed of 30 mph it will take off.

Just seemed a little pointless to me.