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Author Topic: Maximum size aircraft?  (Read 3766 times)

Offline DaveBB

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Re: Maximum size aircraft?
« Reply #15 on: January 01, 2015, 11:37:15 AM »
Quote from: PR3D4TOR on January 01, 2015, 10:42:44 AM
A flexible structure is safer than a rigid one, not the other way around.

You cant generalize it that easily.  Depending on the type of material (metal), some have endurance limits while others do not.  Some metals will even crack and fail regardless of how low the stress and vibrations, while others have to reach a certain 'endurance limit' (stress X cycles) before they will even began to start initiating fatigue cracks.
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Offline PR3D4TOR

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Re: Maximum size aircraft?
« Reply #16 on: January 01, 2015, 03:13:33 PM »
I though it was safe to assume aircraft designers use suitable materials...
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Offline DaveBB

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Re: Maximum size aircraft?
« Reply #17 on: January 01, 2015, 04:23:32 PM »
Almost the entire inventory of U.S. F-16s and B-1bs have cracks.  The material of construction is the limiting factor.  Aluminum cracks, steel is heavy, carbon fiber delaminates, etc.  There is no 'super material' out there.
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Offline earl1937

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Re: Maximum size aircraft?
« Reply #18 on: January 02, 2015, 04:29:46 AM »
 :airplane:
Quote from: PR3D4TOR on January 01, 2015, 10:42:44 AM
A flexible structure is safer than a rigid one, not the other way around.
:airplane: Not sure if you thought though your post, but with flex, comes a lot of problems and that is what i am trying to point out! At what point, or in other words, how many times can a metal object "flex" before fatigue cause the metal to fail?
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Offline PR3D4TOR

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Re: Maximum size aircraft?
« Reply #19 on: January 02, 2015, 05:41:34 AM »
All metal wings flex. It's just a matter of how much. Even back in WWII. How many people here are aeronautical egineers anyway? I sure am not...


Here's a venerable old 747. Plently of wing flexing. This is a non-issue.

https://www.youtube.com/watch?v=WFEs-DatuHs
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Offline colmbo

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Re: Maximum size aircraft?
« Reply #20 on: January 02, 2015, 08:13:58 AM »
Quote from: PR3D4TOR on January 02, 2015, 05:41:34 AM
All metal wings flex. It's just a matter of how much. Even back in WWII. How many people here are aeronautical egineers anyway? I sure am not...


Here's a venerable old 747. Plently of wing flexing. This is a non-issue.

https://www.youtube.com/watch?v=WFEs-DatuHs

On the ground you can't see the wingtiip of the B-24 from the pilot seat.  Once in the air the wing flexes a small amount and you can see the wingtip.
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Offline PR3D4TOR

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Re: Maximum size aircraft?
« Reply #21 on: January 02, 2015, 10:13:51 AM »
Yes, it is nigh impossible to construct a metal structure that doesn't flex under load. Skyscrapers flex in windy conditions. Even the Eiffel Tower bends and twists in wind and from sun heating.
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Offline BaldEagl

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Re: Maximum size aircraft?
« Reply #22 on: January 02, 2015, 10:35:57 AM »
Quote from: PR3D4TOR on January 02, 2015, 10:13:51 AM
Yes, it is nigh impossible to construct a metal structure that doesn't flex under load. Skyscrapers flex in windy conditions. Even the Eiffel Tower bends and twists in wind and from sun heating.

Yep.  You could really feel it in the old World Trade Center buildings.
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Offline Krupinski

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Re: Maximum size aircraft?
« Reply #23 on: January 02, 2015, 11:47:21 AM »
Quote from: PR3D4TOR on January 02, 2015, 05:41:34 AM
All metal wings flex. It's just a matter of how much. Even back in WWII. How many people here are aeronautical egineers anyway? I sure am not...


Here's a venerable old 747. Plently of wing flexing. This is a non-issue.

https://www.youtube.com/watch?v=WFEs-DatuHs

I was reading one of the comments, is it true that when the wing flex limit is reached, the outer engines are designed to break off?
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Offline PR3D4TOR

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Re: Maximum size aircraft?
« Reply #24 on: January 02, 2015, 04:20:58 PM »
I have no idea. Sorry.
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Offline earl1937

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Re: Maximum size aircraft?
« Reply #25 on: January 03, 2015, 07:18:34 AM »
Quote from: PR3D4TOR on January 01, 2015, 10:42:44 AM
A flexible structure is safer than a rigid one, not the other way around.
:airplane: "Ah, finally a response from an "aircraft engineer"!
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Offline PR3D4TOR

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Re: Maximum size aircraft?
« Reply #26 on: January 03, 2015, 07:31:02 AM »
That's my point. Why are we even discussing it? I'm pretty sure the guys who actually are aeronautical engineers know what they're doing when they design these aircraft. By comparison we're like 8 year olds arguing over how best to screw a hooker in Bangkok...
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Offline kvuo75

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Re: Maximum size aircraft?
« Reply #27 on: January 03, 2015, 08:47:19 AM »
why bring up wing flex anyway.. are wings falling off planes?

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Offline FTJR

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Re: Maximum size aircraft?
« Reply #28 on: January 04, 2015, 05:01:20 AM »
Quote from: Mister Fork on December 31, 2014, 11:31:31 AM
Very good point - especially in light of the recent AirAsia - it seems that the flex is probably what killed the aircraft.  .........I'm sure that a tired bird (like the A320 that had over 13'000 flights) tolerances were also part of the problem of the break-up.

Far, far to early to assume the above.

Just saying
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Offline Oldman731

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Re: Maximum size aircraft?
« Reply #29 on: January 04, 2015, 09:07:30 AM »
Quote from: FTJR on January 04, 2015, 05:01:20 AM
Far, far to early to assume the above.


Agreed.  Latest I heard suggested that ice was the culprit.

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