Ethiopean 787 fire at Heathrow
Maybe the only way to answer these questions on flamability is to take a number of aircraft from the world's 2 principal manufacturers and ignite them simultaneously to see which produces the most toxic smoke and which burns longest.
Airbus - A320 and A330
Boeing - 777 and 787
Airbus - A320 and A330
Boeing - 777 and 787
Boeing release their Q2 earnings today and have the earnings call at 1530 UK time. Why not call investor relations and ask the question of the executives on the call today?
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i wonder if the coeff of thermal expansion (CTE) of the composite is much greater than aluminium and may allow more aircraft growth and contraction
However, a wound fibre fuselage barrel may increase its diameter (fibre direction) in the cold air at altitude, while increasing additionally due to the pressurisation loop stress, so overall diameter increase may be more than the one of an aluminum fuselage. But I seriously doubt that this is a challange for the wiring, it should be designed to withstand airframe deformation.
And, prior to getting to my final points regarding thermal insulative and conductivity properties of aluminum alloys and CFRP's as I promised that the outset of this overly long input, let me give some relevant metallic vs. CFRP cross plied properties for others to mull over. CF is widely touted, and oft over-touted, regarding its strength, but let us be very careful here. A decent CFRP will have a tensile composite strength, if a UD material at 60 % fiber volume, of around 280- 320 KSI,( note that is the sigma 1-1 equivalent to metallics).
A quasi-isotropic composite in the same CFRP will have a tensile value of around 90-120 KSI. Now, let us look a couple of weaknesses without boring you all with the hygroscopic nature of that nasty epoxy.
The shear strength of metallics is typically 60% of the tensile, so for a decent steel, for example, say in the 240 ksi range we will have a shear strength of around 145 KSI. Now look at composites and up pops that nasty epoxy again. Whereas Steel will have a SBS or ILSS strength of 144 KSI, a quasi-isotropic composite will have an ILSS of 8-10 KSI static on a good day and, if we allow for fatigue et al, we are down in the 4 ksi area. And finally another key nasty is the short transverse tensile strength ( equivalent to metallic sigma 3-3), which is entirely epoxy dependent and no CF failure is involved, there we find on a good day around 3-4 KSI with fatigue knocking that down to around 1-1.5 kSI wihich is close enough to zero in this composite engineer's mind.
A quasi-isotropic composite in the same CFRP will have a tensile value of around 90-120 KSI. Now, let us look a couple of weaknesses without boring you all with the hygroscopic nature of that nasty epoxy.
The shear strength of metallics is typically 60% of the tensile, so for a decent steel, for example, say in the 240 ksi range we will have a shear strength of around 145 KSI. Now look at composites and up pops that nasty epoxy again. Whereas Steel will have a SBS or ILSS strength of 144 KSI, a quasi-isotropic composite will have an ILSS of 8-10 KSI static on a good day and, if we allow for fatigue et al, we are down in the 4 ksi area. And finally another key nasty is the short transverse tensile strength ( equivalent to metallic sigma 3-3), which is entirely epoxy dependent and no CF failure is involved, there we find on a good day around 3-4 KSI with fatigue knocking that down to around 1-1.5 kSI wihich is close enough to zero in this composite engineer's mind.
Having designed, build, tested to destruction, certified and repaired a CFRP glider wing, I often wonder what those "metal guys" are trying to build from CFRP...
Last edited by Volume; 24th Jul 2013 at 09:44.
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Shirley I'm not the only reader of this thread to have ever burnt a fibreglass moulding on a bonfire?
A bath, a caravan roof , a dinghy and part of a vehicle body all exhibit the same characteristics,as regards burning.
Like any other plastics, lots of thick, black smoke is emitted and the flame front spreads rapidly across the surface, accompanied by a typical "sizzling" as the plastic in the heat-path of the flame-front bursts into tiny, popping bubbles which rapidly burst, releasing their inflammable gases and thus progressing the flame-front.
The plastic (resin) burns away completely, leaving a perfect armature of the original moulding....It is, however, more fragile than an eggshell and will often collapse under it's own weight.
Glass fibre /Carbon-fibre/ Kevlar....it doesn't really matter............................of itself, the fibre is soft and pliable, the resin impregnation gives the strength and rigidity...burn the resin and you've little more than a starched textile.
Many a fibreglass/Composite boat has been burnt to the waterline, I would not like to be in a burning Composite aircraft.
I'd take my chance in something like a Cirrus, but not in a commercial airliner with the mass of attendant electricals, water heaters,pax attempting a crafty puff etc. no, IMO there is a good case for composites in aircraft, but the Pax deserve a more robust survival-cell.
Self-extinguishing resins are readily available,their suitability in this application is another issue and if the flames or loss of strength don't get you, the fumes surely will!
Thanks, Amicus for your highly technical treatise. It leads one to believe the public have been hoodwinked by the vested interests.
The "screamliner" *could* have had a huge economic advantage over a conventional aircraft, albeit with a compromised level of safety.
We all take our chances weighing risk and gain in our daily lives.
Generation 2 of the "Plastic -Fantastics" may well bring the much-vaunted benefits, but I fear the 787 was too many steps too far, too soon.
A bath, a caravan roof , a dinghy and part of a vehicle body all exhibit the same characteristics,as regards burning.
Like any other plastics, lots of thick, black smoke is emitted and the flame front spreads rapidly across the surface, accompanied by a typical "sizzling" as the plastic in the heat-path of the flame-front bursts into tiny, popping bubbles which rapidly burst, releasing their inflammable gases and thus progressing the flame-front.
The plastic (resin) burns away completely, leaving a perfect armature of the original moulding....It is, however, more fragile than an eggshell and will often collapse under it's own weight.
Glass fibre /Carbon-fibre/ Kevlar....it doesn't really matter............................of itself, the fibre is soft and pliable, the resin impregnation gives the strength and rigidity...burn the resin and you've little more than a starched textile.
Many a fibreglass/Composite boat has been burnt to the waterline, I would not like to be in a burning Composite aircraft.
I'd take my chance in something like a Cirrus, but not in a commercial airliner with the mass of attendant electricals, water heaters,pax attempting a crafty puff etc. no, IMO there is a good case for composites in aircraft, but the Pax deserve a more robust survival-cell.
Self-extinguishing resins are readily available,their suitability in this application is another issue and if the flames or loss of strength don't get you, the fumes surely will!
Thanks, Amicus for your highly technical treatise. It leads one to believe the public have been hoodwinked by the vested interests.
The "screamliner" *could* have had a huge economic advantage over a conventional aircraft, albeit with a compromised level of safety.
We all take our chances weighing risk and gain in our daily lives.
Generation 2 of the "Plastic -Fantastics" may well bring the much-vaunted benefits, but I fear the 787 was too many steps too far, too soon.
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On the cause ??
787 fire investigation looks at pinched battery wiring | Business & Technology | The Seattle Times
787 fire investigation looks at pinched battery wiring
Investigators believe the July 12 fire on a 787 Dreamliner at Heathrow was likely caused by incorrect installation of a battery that pinched some wires and caused a short circuit.
Boeing and government investigators now believe the July 12 fire on a 787 Dreamliner at Heathrow Airport in London was likely caused by the incorrect installation of a small lithium ion battery inside an electronic device.
If that’s confirmed, the fire was due to human error, not a Boeing design flaw.
U.K. investigators who examined the device, called an Emergency Locator Transmitter (ELT) and made by Honeywell, found that the internal wires connecting the battery to the ELT had been trapped and pinched when the cover was reattached as the batteries were inserted, according to two sources with knowledge of the matter, one inside Boeing and one outside.
In photos of what was left of the device, “You can clearly see the two wires crossed over each other. It’s quite evident the wires show evidence of being smashed,” one source said.
Installing the battery package entails unscrewing the cover of the relatively small device, dropping the battery pack of five cells into a slot and connecting the two wires that protrude from the battery pack to a receptacle in the ELT.
goes on ...
The two sources suggested that Honeywell might have replaced the batteries at some stage before delivery of the jet because the devices sat on the shelf during the years-long 787 program delays.
If this were correct, it could explain why the accident happened to the 787 in particular.
Investigators are also looking at whether overheating of the batteries as they sat parked in the sun during the four-month grounding of the 787 fleet earlier this year could have led to internal damage that contributed to the failure.
There’s no evidence of moisture damaging the batteries, which had been another theory put forward in the press.
787 fire investigation looks at pinched battery wiring
Investigators believe the July 12 fire on a 787 Dreamliner at Heathrow was likely caused by incorrect installation of a battery that pinched some wires and caused a short circuit.
Boeing and government investigators now believe the July 12 fire on a 787 Dreamliner at Heathrow Airport in London was likely caused by the incorrect installation of a small lithium ion battery inside an electronic device.
If that’s confirmed, the fire was due to human error, not a Boeing design flaw.
U.K. investigators who examined the device, called an Emergency Locator Transmitter (ELT) and made by Honeywell, found that the internal wires connecting the battery to the ELT had been trapped and pinched when the cover was reattached as the batteries were inserted, according to two sources with knowledge of the matter, one inside Boeing and one outside.
In photos of what was left of the device, “You can clearly see the two wires crossed over each other. It’s quite evident the wires show evidence of being smashed,” one source said.
Installing the battery package entails unscrewing the cover of the relatively small device, dropping the battery pack of five cells into a slot and connecting the two wires that protrude from the battery pack to a receptacle in the ELT.
goes on ...
The two sources suggested that Honeywell might have replaced the batteries at some stage before delivery of the jet because the devices sat on the shelf during the years-long 787 program delays.
If this were correct, it could explain why the accident happened to the 787 in particular.
Investigators are also looking at whether overheating of the batteries as they sat parked in the sun during the four-month grounding of the 787 fleet earlier this year could have led to internal damage that contributed to the failure.
There’s no evidence of moisture damaging the batteries, which had been another theory put forward in the press.
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"Self-extinguishing" certainly shouldn't be confused with "fire proof". Self extinguishing materials may stop the spread of fire, but certainly should be replaced at first opportunity. Also, isn't a 777 an aluminum bird? Seems like some think it's a composite.
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I can't help but think that equipment designed such that it allows the wires to be crushed when reassembled suffers more from "design flaw" than "human error". There are billions of devices out there that manage perfectly well to have replaceable batteries that cannot suffer from this problem. SOme of them are probably in safety critical applications, too.
Regardless, Boeing can point the finger at Honeywell if blaming the maintainer doesn't stick.
Regardless, Boeing can point the finger at Honeywell if blaming the maintainer doesn't stick.
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Regardless, Boeing can point the finger at Honeywell if blaming the maintainer doesn't stick.
Last edited by HeavyMetallist; 24th Jul 2013 at 14:19.
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I can't help but think that equipment designed such that it allows the wires to be crushed when reassembled suffers more from "design flaw" than "human error".
From an electronic design point of view, some cables are longer than they need to be so that parts can be removed without having to unplug/disconnect one thing from another.
Making a cable short enough to not become trapped in a reassembled casing, can mean having to disconnect it to remove another part of the circuit which may lead to other problems or puts tension on the wire which could lead to a break.
Much better to have a looser wire which allows greater accessibility and an SOP which involves making sure the wire isn't trapped when the device is manufactured.
Remember these beacons have a battery life of 10 years and once installed should need very little or no attention.
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Originally Posted by funfly
I know I posted this before but relevant to the current comments, this was my all glass fibre aircraft following a crash land (after I sold it luckily)
Are you saying CFRP planes burn more or burn the same and Aluminium alloy aircraft?
I've seen plenty burn out hulks of more traditionally constructed aircraft, large and small.
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Sorry mate, not making a point. Just though it might be interesting to see what a burnt out glass fibre aircraft hull looked like as there had been a lot of comment about glass fibre burning.
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I see your burnt-out fiberglass light-sport aircraft and raise you three burnt-out aluminum Cessnas and Pipers.
Of course none of these fires have any relevance to the case at hand, as they are uncertified aircraft (your case) and CAR3 / FAR 23 certified aircraft (my case) which have no requirement to be tested or certified to prevent burn through as FAR 25 aircraft have to be.
This entire argument regarding the autoignition temperature of aluminum and CFRP is bogus from the beginning as it ignores thermal mass. Place a 2" thick paper textbook and an empty aluminum beer can in front of a lit propane torch, and let me know which one burns through first.
Of course none of these fires have any relevance to the case at hand, as they are uncertified aircraft (your case) and CAR3 / FAR 23 certified aircraft (my case) which have no requirement to be tested or certified to prevent burn through as FAR 25 aircraft have to be.
This entire argument regarding the autoignition temperature of aluminum and CFRP is bogus from the beginning as it ignores thermal mass. Place a 2" thick paper textbook and an empty aluminum beer can in front of a lit propane torch, and let me know which one burns through first.
Re this quote in the Seattle Times article above: "It’s quite evident the wires show evidence of being smashed,” one source said.
How do you 'smash' a wire? With a brick or a rock or a hammer? Is this just bad English, or a typo? Are we supposed to 'correct' the word into another such as 'mash' or 'crush' or 'pinch' or anything that might make some sense, or is that taking liberties and are we expected to take this word at face value?
How do you 'smash' a wire? With a brick or a rock or a hammer? Is this just bad English, or a typo? Are we supposed to 'correct' the word into another such as 'mash' or 'crush' or 'pinch' or anything that might make some sense, or is that taking liberties and are we expected to take this word at face value?
Last edited by jolihokistix; 24th Jul 2013 at 15:58.
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Shirley???????????
Who is "Shirley"?
Shirley I'm not the only reader of this thread to have ever burnt a fibreglass moulding on a bonfire?
Sorry could not resist, see the "airplane" movie series for the reference if new to you.
Last edited by MurphyWasRight; 24th Jul 2013 at 16:47. Reason: Fixed nested qoutes that scrambled meaning.
Amicus,
Thanks for the lengthy explanation, though not being a materials engineer,
am having a bit of trouble decoding the acronyms and values as to their
relevance. Would be gratefull if you could provide a bit more background in
terms of the basics...
Thanks for the lengthy explanation, though not being a materials engineer,
am having a bit of trouble decoding the acronyms and values as to their
relevance. Would be gratefull if you could provide a bit more background in
terms of the basics...