will it fly?? - Alfa Romeo Bulletin Board & Forums

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post #1 of 58 (permalink) Old 04-16-2017, 12:31 AM Thread Starter
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will it fly??

Not Alfa related. Not sorry. I pay my dues so allow me some leeway. If a 747 is on a treadmill and the wheels can be brought up to say 180 kts, will the plane fly?

I say no since there is no forward airspeed to generate lift from the wings.

Another group I'm part of has been arguing this and I figger I'd ask cause frankly, you guys are alot smarter than this other group of hooligans. Ciao, chris

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post #2 of 58 (permalink) Old 04-16-2017, 05:38 AM
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I had to look up kts, so I shouldn't answer.

With that said, your logic appears to be sound. Don't know if there is some trick to the question.

John
1991 Alfa Romeo 164L, 1993 Ford 5.0L Mustang
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post #3 of 58 (permalink) Old 04-16-2017, 06:46 AM
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Chris:

Seriously?

Can you post a picture?

Sorry, couldn't resist.



PS: how fast is the treadmill moving?
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post #4 of 58 (permalink) Old 04-16-2017, 09:19 AM
Del
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Sheesh, what kind of friends do you have, lol? I don't think I would listen to them for the time of day.

No, of course the airplane won't fly, duh. (it's being held down by cables to prevent it from going downstream on the treadmill, wink, wink).

Del

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post #5 of 58 (permalink) Old 04-16-2017, 09:22 AM
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It all depends on the velocity of the treadmill, eh?

If the treadmill hits V2, it will fly.

(Added to clarify: If the treadmill accelerates down the runway and achieves the 747's V2 with the 747 still on board, the 747 will fly, at least briefly)

Last edited by RexCars; 04-16-2017 at 09:58 AM.
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post #6 of 58 (permalink) Old 04-16-2017, 10:05 AM
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This is an oldie. I remember arguing this on the Internet 15 years ago!

The answer is simple and obvious. The plane isn't going anywhere unless it achieves a certain AIR speed. Ground speed is completely irrelevant. As the original problem states (and any sort of reasonable assumptions contained therein) the airspeed is zero so the plane just sits there.

I have seen arguments like Rex's that somehow the entire contraption - treadmill with plane installed on it - is itself propelled through space but there is nothing in the original question to support as assumption like that.
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post #7 of 58 (permalink) Old 04-16-2017, 10:12 AM
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I think, Chris, your hanging out with the wrong crowd....
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post #8 of 58 (permalink) Old 04-16-2017, 10:16 AM Thread Starter
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Not the wrong crowd, just a diverse group of aircraft maintainers for the most part. Mainly AF but a few Naval types. Can't look at pics or post them AFIK. Manage attachments button below is non existant. Can't see avatars either. Anyway, Like I said I just wanna see the smart folks thoughts!! ciao, chris

Maintaining my tenuous strain on reality.
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Recently added: an 89 75 (Milano) 1.6 litre w/44K on the klok.

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An 88 Graduate. Not really love but interesting nonetheless.

A 68 BMW 1602 - man do I regret letting that one go!

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post #9 of 58 (permalink) Old 04-16-2017, 11:49 AM
Del
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"just a diverse group of aircraft maintainers"

Oof! That's actually a little scary what they don't know.

I think you are pulling our collective legs, lol.

Del

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previously owned since 1964:

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post #10 of 58 (permalink) Old 04-16-2017, 01:17 PM
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So if you put your treadmill in the back yard, plugged it in and then placed your lawn mower on the moving treadmill how much grass can you get cut?

If My Alfa sat on a treadmill and it was orbiting in space will it still rust?

If you put a treadmill backwards on a treadmill will they cancel each other and leave you standing there?

I think I am going to the shop and unplugging my treadmill it is starting to worry me.
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post #11 of 58 (permalink) Old 04-16-2017, 01:30 PM
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I had to move my lawnmower to get to my 164 struts and mid-muffler for Non-BB4.

Neither one flew.

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post #12 of 58 (permalink) Old 04-16-2017, 01:48 PM
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The answer is obvious. If you are running on a treadmill at 6 miles an hour will your momentum create a breeze to cool you off? The plane needs the breeze.
This calls for a beer.
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post #13 of 58 (permalink) Old 04-16-2017, 03:56 PM
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I don't think you worded the question quite right. When this originally came up a few years ago the scenario was that as the jet engines apply thrust could a treadmill running in the opposite direction prevent the airplane from moving forward and the answer is no it could not so yes, the airplane would fly. The reason is because the thrust of the engines, unlike the driven wheels of an automobile, is not in any way connected to nor dependent on the ground (treadmill). The thrust is exerted on the air which the treadmill has no effect on.

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post #14 of 58 (permalink) Old 04-16-2017, 05:16 PM
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"The thrust is exerted on the air which the treadmill has no effect on"

Yes, the treadmill has no effect on the air, but no, the thrust is not exerting (reacting) on the air. The thrust is just a force in one direction, reaction in the opposite. Just like rockets don't. That's how rockets work as well in space where there is no air.

The airplane is definitely going to fly.

Now, as along as they don't overbook...

Del

Seattle

89 Milano (wife's daily driver since 1989, Shankle Sport)
91 164S (my daily driver since 1994)
94 164LS (~Q) (trip Alfa since 2000)
72 Morgan 27 (water time since 1976)

previously owned since 1964:

62 Morris MiniMinor 850, 67 Austin 1275 Cooper S (Downton 3/4 race), 64 Giulia Sprint GT (1st red one made), 72 Fiat 128 Sedan, 75 Alfetta Sedan, 78 Alfetta Sedan, 78 GTV, 81 GTV6, 86 GTV6

Last edited by Del; 04-16-2017 at 05:34 PM.
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post #15 of 58 (permalink) Old 04-16-2017, 05:20 PM
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Quote:
Originally Posted by kcabpilot View Post
I don't think you worded the question quite right. When this originally came up a few years ago the scenario was that as the jet engines apply thrust could a treadmill running in the opposite direction prevent the airplane from moving forward and the answer is no it could not so yes, the airplane would fly. The reason is because the thrust of the engines, unlike the driven wheels of an automobile, is not in any way connected to nor dependent on the ground (treadmill). The thrust is exerted on the air which the treadmill has no effect on.
That's right, that's right. I knew there was something missing here but I couldn't remember what. That makes for a much more interesting thought experiment (and an airborne plane).
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