Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Fired engineer calls 787's plastic fuselage unsafe

Tech Log The very best in practical technical discussion on the web

Fired engineer calls 787's plastic fuselage unsafe

Old 22nd Sep 2007, 12:44
  #61 (permalink)  
 
Join Date: Mar 2002
Location: Florida
Posts: 5,246
were these 3 pieces the marry up joins?
Mostly....................
lomapaseo is offline  
Old 24th Sep 2007, 00:47
  #62 (permalink)  
 
Join Date: Sep 2005
Location: N/A
Posts: 131
I saw the video. Vince Weldon does not actually claim that the 787 is unsafe. His point is that there are many questions to which Boeing and the FAA do not have the answers to yet, questions that should be looked into a little more than has been done.
An aicraft with so much leading edge technology should have a little more flight testing than the fast track program that was announced to make up for the production delays.
It is also said in the program that Airbus decided to use less composites in the A-350 but is under pressure from it scustomers to use more composites to save weight. There seems to be a reluctance......
One thing is for certain. The 787 will make or break Boeing.
Minorite invisible is offline  
Old 25th Sep 2007, 09:02
  #63 (permalink)  
 
Join Date: May 2006
Location: 2 m South of Radstock VRP
Posts: 2,042
Having established that the 787 is new and that racing cars crash "safely", was my question too difficult to answer or just too stupid to bother with?
GOLF_BRAVO_ZULU is offline  
Old 25th Sep 2007, 11:38
  #64 (permalink)  
 
Join Date: Sep 2005
Location: N/A
Posts: 131
To see the interview video

Has anyone posted the link where the interview can be seen? I dont think so.

Its here:

http://www.hd.net/drr231.html
Minorite invisible is offline  
Old 25th Sep 2007, 19:15
  #65 (permalink)  
 
Join Date: May 2000
Location: Seattle
Posts: 3,134
Having established that the 787 is new and that racing cars crash "safely", was my question too difficult to answer or just too stupid to bother with?
The dynamics of car and airplane crashes are quite different. The regulatory requirements for race cars, passenger cars, transport airplanes, and light GA airplanes are quite different. How can you assume the experience with race cars applies directly to airplane fuselages?
Intruder is offline  
Old 26th Sep 2007, 07:44
  #66 (permalink)  
 
Join Date: May 2006
Location: 2 m South of Radstock VRP
Posts: 2,042
Intruder; personally I don't and I suggest that the entire comparison is a pointless red herring. Please read my earlier and, I believe, pertinent question at Srl 51. How easy/possible is it to detect the effects of seemingly minor damage in composite fabrications?

Taking it to the simplistic, we all know that "used" motor bike crash helmets are supposed to be consigned to the gash bin as they are only likely to protect you the once, even if they look only scratched.
GOLF_BRAVO_ZULU is offline  
Old 26th Sep 2007, 12:35
  #67 (permalink)  
 
Join Date: Mar 2002
Location: Florida
Posts: 5,246
The dynamics of car and airplane crashes are quite different
How so

The regulatory requirements for race cars, passenger cars, transport airplanes, and light GA airplanes are quite different.
What do the regulations have to do with the differences between race cars and comercial aircraft relative to composites?
lomapaseo is offline  
Old 27th Sep 2007, 02:39
  #68 (permalink)  
 
Join Date: May 2000
Location: Seattle
Posts: 3,134
Intruder; personally I don't and I suggest that the entire comparison is a pointless red herring. Please read my earlier and, I believe, pertinent question at Srl 51. How easy/possible is it to detect the effects of seemingly minor damage in composite fabrications?
My experience in composites is limited to building and repairing small boats. Even in that very limited domain, though, I am aware that there is such a significant difference in the behavior of different composites (e.g., glass/polyester, glass/epoxy, Kevlar/epoxy, wood/resin...) that one cannot generalize about their responses to various types of stress and damage. I suspect that even within the context of the single 787 airplane, there will be several different composite layups, each with their individual inspection/repair criteria. I'll leave it to an expert in the specific composites to tell us what some of those criteria may be.

IIRC, the issue with motorcycle helmets has more to do with the foam liner than the composite shell. While the shell may still do what it is supposed to do, the foam liner may be permanently compressed in some places after a significant impact. Since that liner gives the bulk of the actual protection, its failure (or actually, its planned response to the impact) may make it significantly less able to provide the specified protection in a subsequent impact.
Intruder is offline  
Old 27th Sep 2007, 12:55
  #69 (permalink)  
 
Join Date: Sep 2007
Location: Australia
Posts: 105
Re: Damage assessment/detection
I imagine significant events (tail strike) would trigger a thorough Non Destructive Testing programme for surrounding structure to look for delaminations etc. I don't know much about NDT in composites, but as far as I know, acoustic methods are the most effective (there may be others). I know of one method used for quality control in the manufacture of CFRP flight control surfaces that involves passing running water over the part, and then elsewhere on the part monitoring the sound waves generated by the running water - thus irregularities can be detected this way.
In the field I imagine conventional ultrasonic testing would be used. Though this is only one NDT procedure, and it has its limitations. Anyone have some more details about composite NDT?

Re: Carbon fibre ship masts
As far as I know - these are generally constructed with a lot of unidirectional material. I am guessing that unidirectional material would not be used to so great an extent in 787 fuselage primary structure, thus the failure modes can't really be compared.

Last edited by nick2007; 27th Sep 2007 at 12:57. Reason: Anyone have some more details about composite NDT?
nick2007 is offline  
Old 18th Jan 2008, 20:12
  #70 (permalink)  
 
Join Date: Jan 2005
Location: France
Posts: 2,316
Just saw reference to this thread. Will read first, but logged in to get the e-mail updates.
ChristiaanJ is offline  
Old 20th Jan 2008, 10:20
  #71 (permalink)  
BarbiesBoyfriend
Guest
 
Posts: n/a
What happens when a GPU or catering truck knocks a hole in a 787 (or other plastic a/c)?

Is the patch going to have the same longevity as the rest of the fus'?

Also, said patch is going to need curing time and quite a lot of extensive and careful grinding and prep work.

Not sayimg it can't be done or anything, but........
 
Old 21st Jan 2008, 07:23
  #72 (permalink)  
 
Join Date: Jul 2006
Location: Australia
Posts: 135
Quote:
Having established that the 787 is new and that racing cars crash "safely", was my question too difficult to answer or just too stupid to bother with?
The dynamics of car and airplane crashes are quite different. The regulatory requirements for race cars, passenger cars, transport airplanes, and light GA airplanes are quite different. How can you assume the experience with race cars applies directly to airplane fuselages?
A modern formula 1 car's tub is made entirely of carbon fiber.Watch a race where a f1 car has hit a solid retaining wall at high speed and see how well the tub absorbs the impact without breaking and the driver walking away with the only injury concussion.
F1 is a technically highly regulated sport and the tub has to pass stringent crash tests in order for it to be allowed to race.Teams spend millions in order to pass these crash tests.
I agree the dynamics of an airliner and an f1 car are not the same but if a f1 car tub can now be perfected to resist breaking in an accident and absorb the impact I'm sure the same can be done with a new aircraft such as the Boeing 787 dream liner.
satos is offline  
Old 21st Jan 2008, 07:50
  #73 (permalink)  
 
Join Date: Jan 2001
Location: UK
Posts: 2,045
satos... I am afraid you miss the point... Having crashed into the wall, do they now reuse the CF tub? How do they view? assess? repair? the damage, and then certify? the repaired tub?

This is the real worry. Look around on "old" airliner, typically 10+ significant and visible patches rivetted on. Who knows how many unseen or repeated patches have been done....

NoD
NigelOnDraft is offline  
Old 22nd Jan 2008, 04:21
  #74 (permalink)  
 
Join Date: Jul 2006
Location: Australia
Posts: 135
satos... I am afraid you miss the point... Having crashed into the wall, do they now reuse the CF tub? How do they view? assess? repair? the damage, and then certify? the repaired tub?
If the car hit a wall and is damaged they can patch repair the tub which makes it stronger in that area than before but heavier which can be a disadvantage in F1 as lightness is the key objective in this sport.
The tub is also tested regularly by ultrasonic inspection for any imperfections and before and after repairs are carried out to make sure it is structurally sound.
Production and maintenance of these cars is A1 with quality control on par with aviation.
Most of the top teams spend between 300-400 million dollars (USD) a year in research and development of these cars.
satos is offline  
Old 22nd Jan 2008, 06:50
  #75 (permalink)  
 
Join Date: Jan 2001
Location: UK
Posts: 2,045
satos... You still have not answered "see". Let me put it another way - how do they "know" to look for damage? * CF etc. tend to "spring back" when struck, and on the exterior show no damage, yet internally there is delamination etc. - a typical airliner scenario when struck by a servicing vehicle, which is the cause of 90%+ of the patches discussed above.

<<they can patch repair the tub which makes it stronger in that area than before >> This is easy in "basic structures", say boats. Surprised so at F1 where you are presumably using unidirectional fibres, and you have to strip the damaged area back and somehow link in the "repair" fibres into the original long fibres... Remember we are not talking a sport - we are talking a certified passenger vehicle

* The answer cannot be "because the driver of said vehicle says so"
NigelOnDraft is offline  
Old 23rd Jan 2008, 07:08
  #76 (permalink)  
 
Join Date: Jul 2006
Location: Australia
Posts: 135
As I said in my previous post,they ultrasonic test the tub for hidden damage such as delamination etc.
satos is offline  
Old 23rd Jan 2008, 10:55
  #77 (permalink)  
 
Join Date: Oct 2001
Location: Australia.
Posts: 305
A modern formula 1 car's tub is made entirely of carbon fiber.Watch a race where a f1 car has hit a solid retaining wall at high speed and see how well the tub absorbs the impact without breaking and the driver walking away with the only injury concussion.
How can any structure absorb energy if it does not significantly deform?

If they need to
ultrasonic test the tub for hidden damage such as delamination etc.
after an accident well then it was not the carbon fiber structure that absorbed the energy of the crash, it must have been the soft bits of car around it that did.

If you put a raw egg in a tin can and drop it onto the road, the can is hardly going to deform at all, meaning that it absorbs very little. It will simply transfer that sudden deceleration to the poor little egg inside.
Blip is offline  
Old 23rd Jan 2008, 11:02
  #78 (permalink)  
 
Join Date: Jan 2001
Location: UK
Posts: 2,045
As I said in my previous post,they ultrasonic test the tub for hidden damage such as delamination etc.
satos... I ask again, how do they KNOW to do the ultrasound? Presumably because telemetry and the driver and the wreck say "we crashed it".

Translate that to a 787. How does one KNOW to ultrasound it? Unless the structure shows visible damage when it is whacked, which as you say composites do not, yet are damaged internally, then the engineer / pilot does not know... The person causing the (possible) damage will not, in general, say a thing
NigelOnDraft is offline  
Old 23rd Jan 2008, 12:31
  #79 (permalink)  
 
Join Date: Jan 2005
Location: Bristol
Posts: 94
What about work hardening of metals as they become brittle with age and stress imposed on them. Bend a piece of metal enough and it becomes brittle and will fracture easily. Do composites react in the same way and/or have a more "elastic" property giving rise to longer life?

How after an accident on a composite aircraft do you try to find the cause if its structural and not the obvious.If its metal you can detect age hardening of the metal by detailed analysis,( Comet disaster) This physical property I would suspect, may not be present in composites...i dont know??, so when faced with millions of pieces of composite you dont know which let go due to stress and which are a result of the impact during the accident ...do composites show signs of aging etc etc that can be scrutinised in the event of failure?? if the composites have melted away in the ensuing fireball would this leave forensic analysis more difficult..i'd suspect so. I only did metalurgy to OND level as a small module of a general engineering qualification ..and composites werent in abundance then.
Burnt Fishtrousers is offline  
Old 23rd Jan 2008, 13:09
  #80 (permalink)  
 
Join Date: Nov 2006
Location: XUMAT
Age: 57
Posts: 133
I do recall seeing some talk of Boeing using implanted metal fibres both for lightning and electrical conductivity as well as detecting fuselage damage. Any break or distortion in the grid would be detectable by a system that they have cooked up under various patents.

Obviously all top secret and patented but along the lines of an electrical pulse being sent out and any deviation from the norm provides an 'echo' pinpointing the area to be looked at. They can then do something akin to those whizzy Autoglass type repairs where a resin is forced into any crack and it then sets harder than the original.
Whitehatter is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.