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| Will the plane take off? |
| Yes it will |
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38% |
[ 10 ] |
| No it wont |
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61% |
[ 16 ] |
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| Total Votes : 26 |
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hypnotist
Joined: 04 Dec 2004
Location: I wish I were a sock
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 Posted: Mon Dec 05, 2005 6:04 pm Post subject: |
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| Swiss James wrote: |
well this link
http://www.avweb.com/news/columns/191034-1.html
that poker player posted postures that the plane would be stationary, and it would still take off because the air speed would increase as the thrust from the engines increase.
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No, SJ - that article agrees with me...
At that moment the conveyor is moving at 10 mph to the east and the tires are whirling around at 20 mph because the prop has pulled it to an airspeed, and groundspeed, of 10 mph, westbound. The airplane is moving relative to the still air and the ground at 10 mph, but with regard to the conveyor, which is going the other way at 10 mph, the relative speed is 20 mph. |
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Wangja
Joined: 17 May 2004
Location: Seoul, Yongsan
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| Posted: Mon Dec 05, 2005 6:18 pm Post subject: |
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I am shocked to find such respected people believeing that a plane still (not moving) in the air will fly.
God does indeed move in mysterious ways.
Edit: hey!! where did JG's post just go? |
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JongnoGuru
Joined: 25 May 2004
Location: peeing on your doorstep
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| Posted: Mon Dec 05, 2005 6:24 pm Post subject: |
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| Wangja wrote: |
I am shocked to find such respected people believeing that a plane still (not moving) in the air will fly.
God does indeed move in mysterious ways.
Edit: hey!! where did JG's post just go? |
I just read the linked article and noticed there was a gap of a few minutes when no-one was posting. I thought perhaps everyone was reading that article... but no, that link was posted some time ago, and surely everyone had read it by now.
Anyway, doesn't that article settle this question? Seems rather authoritative. This is where faith takes over and people (such as myself) who don't know or care enough about it will bow to those who prance around and talk as though they do. In other words, I believe it flies. (And I don't want to read anymore about it, as I was like Eamo last night -- equally convinced it could and couldn't fly.)
Last edited by JongnoGuru on Mon Dec 05, 2005 6:30 pm; edited 2 times in total |
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Wangja
Joined: 17 May 2004
Location: Seoul, Yongsan
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| Posted: Mon Dec 05, 2005 6:25 pm Post subject: |
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| Nope: imagine the plane is a jet ...... |
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Swiss James
Joined: 26 Nov 2003
Location: Shanghai
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| Posted: Mon Dec 05, 2005 6:49 pm Post subject: |
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| hypnotist wrote: |
No, SJ - that article agrees with me...
At that moment the conveyor is moving at 10 mph to the east and the tires are whirling around at 20 mph because the prop has pulled it to an airspeed, and groundspeed, of 10 mph, westbound. The airplane is moving relative to the still air and the ground at 10 mph, but with regard to the conveyor, which is going the other way at 10 mph, the relative speed is 20 mph. |
It agrees with you in some places, sure, but...
| hypnotist wrote: |
| My argument is based entirely around my belief that the plane will move forward |
the way I understood, you were saying that if I was stood eye to eye with the pilot, there'd be a tipping point where the friction of the wheels isn't enough to stop the plane from moving. Same as if it was on an icy runway.
That's NOT what the article says.
The article says that I can remain eye-to-eye with the pilot as the propellor turns (or jets jet). The force of the jets makes the air speed of the plane increase, even though I'm still eye-to-eye with the pilot, until the point when it reaches the takeoff air speed.
The planes nose then rises majestically up in the air, and the plane takes off like it's been shot out of a canon, breaking the pilots neck.
Still seems very weird, but I think I'm starting to come round  |
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hypnotist
Joined: 04 Dec 2004
Location: I wish I were a sock
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| Posted: Mon Dec 05, 2005 7:47 pm Post subject: |
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| Swiss James wrote: |
| hypnotist wrote: |
No, SJ - that article agrees with me...
The airplane is moving relative to the still air and the ground at 10 mph |
It agrees with you in some places, sure, but...
| hypnotist wrote: |
| My argument is based entirely around my belief that the plane will move forward |
the way I understood, you were saying that if I was stood eye to eye with the pilot, there'd be a tipping point where the friction of the wheels isn't enough to stop the plane from moving. Same as if it was on an icy runway.
That's NOT what the article says.
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It IS what the article says. Reread the part in bold! It explictly says that shortly after firing up the engine, the plane is moving relative to the still air and the ground at 10mph! Hence you can't remain eye-to-eye with the pilot. Where did you get the idea that the plane suddenly shoots forward from? The article is very clear that throughout the take-off, airspeed is equal to groundspeed, which increases as expected - but with the wheels spinning twice as quickly as usual.
I still don't understand where the objections to the plane flying are coming from. Nobody is saying a stationary plane will fly - not me, not that article. I do understand the concept of lift! What is being said is that the plane does not stay stationary. Thus far, nobody has been able to explain why it would.
| Code: |
Fd <----- [Plane] -----> Ft
Ffric <--
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F = ma. The plane will only remain stationary if F = Ft - ( Fd + Ffric ) = 0.
Fd is constant no matter how fast the conveyor turns. At a set speed, with the plane stationary, those who say the plane does not move claim Ft = ( Fd + Ffric ). As thrust increases, they claim dFt = dFfric.
If the frictional forces are really that great, how the hell do planes ever take off? |
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Wangja
Joined: 17 May 2004
Location: Seoul, Yongsan
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| Posted: Mon Dec 05, 2005 8:02 pm Post subject: |
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The conveyor moves in reverse at the same speed that the plane tries to move forward.
Therefore between the plane and the ground supporting the fixed conveyor, there is no relative movement. With no relative movement there is no flow over the wings and the plane does not lift.
The issue of propellor thrust is a red herring: it is true that as a front-mounted propellor scoops air it sends it back over the plane including some of the wing surface. |
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hypnotist
Joined: 04 Dec 2004
Location: I wish I were a sock
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| Posted: Mon Dec 05, 2005 8:08 pm Post subject: |
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| Wangja wrote: |
The conveyor moves in reverse at the same speed that the plane tries to move forward.
Therefore between the plane and the ground supporting the fixed conveyor, there is no relative movement. With no relative movement there is no flow over the wings and the plane does not lift. |
I don't want this to turn into a CE-forum style "why won't you answer my question" thread, W - both our times are far too valuable for that 
I agree with you entirely about propellor thrust. The issue is about whether the plane moves forward or not. If it does, there is lift and the plane takes off - if not, there isn't and it doesn't. I think we're all agreed about that.
I can follow most of your argument. It's just that little word 'therefore'. Why 'therefore'? Why does the conveyor moving backwards stop the plane moving forward? Remember, the plane is not generating movement by pushing against the ground, as a car would, and the wheels can rotate independently of the plane.
This is the crux of our disagreement. Again, you see this 'therefore' as self-evident but I just can't |
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Pligganease
Joined: 14 Sep 2004
Location: The deep south...
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| Posted: Mon Dec 05, 2005 9:44 pm Post subject: |
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| hypnotist wrote: |
| Why does the conveyor moving backwards stop the plane moving forward? |
Please, tell me you're kidding. |
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Pligganease
Joined: 14 Sep 2004
Location: The deep south...
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| Posted: Mon Dec 05, 2005 9:50 pm Post subject: |
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| Pligganease wrote: |
| hypnotist wrote: |
| Why does the conveyor moving backwards stop the plane moving forward? |
Please, tell me you're kidding. |
Holy crap...
I get it now.
Forgive me everything bad I said. You are correct. The plane would take off. As the engines thrust, the plane pushes forward. The conveyor reverses, but the wheels just spin and the engines still manage to push the plane forward.
Wow. I can't believe it. Good job, Hypnotist. Just took me a little time to grasp the concept that there is no way the conveyor could impede the forward progress of the plane.
*bowing down* |
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JongnoGuru
Joined: 25 May 2004
Location: peeing on your doorstep
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| Posted: Mon Dec 05, 2005 10:02 pm Post subject: |
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I never really bothered looking at the question from a technical perspective. (I'm not properly equipped!) And I didn't bother reading the whole thread. I just kept thinking about how these planes manage their on-water takeoffs.
No wheels. Just floating on the water's surface. How much traction or purchase can there be? Some perhaps, but not nearly enough to get them airborne. It's the thrust of the propellers.
And not just these, but there are the "icebreaker" aircraft that can perform takeoffs on COMPLETELY SLICK and tractionless ice. How? Engine thrust. (okay, I just made that up. but it stands to reason, don't it?) |
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Swiss James
Joined: 26 Nov 2003
Location: Shanghai
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| Posted: Mon Dec 05, 2005 10:24 pm Post subject: |
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OK I think I'm officially on hypnotist's side now. The red herring is not the engine thrust, it's thinking that one revolution of the wheel is the only thing that can move the plane forward one wheel's circumfurence.
I guess if you left the brake on and really ragged the engine, the plane would still eventually overcome the friction of the wheels on the tarmac and slide forward fast enough to take off.
The same concept applies if the wheels are spinning 100mph Eastwards and the conveyor belt is spinning 100 mph Westwards, the plane will still eventually overcome the friction and slide forwards of its own accord.
I'm man enough to admit I was wrong! |
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Wangja
Joined: 17 May 2004
Location: Seoul, Yongsan
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| Posted: Mon Dec 05, 2005 10:31 pm Post subject: |
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Dear Lord
Forgive them for they know not what they do!
Wangja ...
(I'll get back when I have more time!!) |
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Swiss James
Joined: 26 Nov 2003
Location: Shanghai
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| Posted: Mon Dec 05, 2005 10:45 pm Post subject: |
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come wangja!
Come to the dark side!
It's so beautiful here! |
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DirtySanchez
Joined: 26 Mar 2004
Location: Neither here nor there
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| Posted: Mon Dec 05, 2005 11:13 pm Post subject: |
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Wangja, you have to come to the realization that the wheels of a plane produce no thrust whatsoever, and will rotate freely to an infinite speed, much like a car in neutral. Once the propellor or jet engine is fired up, that plane is gonna move forward, and those wheels are just gonna spin faster and faster on into infinity, with no influence on the plane's true airspeed. Thus, the plane will take off, regardless of how fast the conveyor or the wheels are moving.
Search your feelings, Wangja. You know it to be true. |
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