Ethiopean 787 fire at Heathrow
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If there are no "holes", what did ATC spot that made them think "fire"?
Tmperatues sufficient to darken the outside as seen in the photos would also release smoke from the outside surface as it was toasted.
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ELT's are supposed to be watertight, and the Honeywell unit looks to be built like a tank (with I price tag to match I would guess 
)
There are Lithium powered 406's in the tails of King Airs all over the world, sitting on the ramp from Phoenix, to Miami. I doubt the cabin of a 787 is a worse environment.
I don't know quite what to think anymore....
)There are Lithium powered 406's in the tails of King Airs all over the world, sitting on the ramp from Phoenix, to Miami. I doubt the cabin of a 787 is a worse environment.
I don't know quite what to think anymore....
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If there are no "holes", what did ATC spot that made them think "fire"?
Fire fighters equipped with breathing apparatus entered the aircraft at the L2 door and encountered thick smoke
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Boeing 787 probe looks at condensation, wiring
Reuters reports:
...condensation in the plane and a possible pinched wire in an emergency beacon may have sparked the blaze...
...[FAA] said on Friday it will call for inspections of the beacons made by Honeywell on Boeing Co 787 jetliners, but stopped short of requiring airlines to disable or remove the devices...
The FAA said inspections should ensure wires are properly routed, and should look for pinched wires or signs of unusual moisture or heat.
...one source close to the inquiry told Reuters that investigators had found a pinched wire in the casing of the emergency locator transmitter (ELT)...
The unit that was involved in the fire had not been opened, suggesting the pinched wire originated at the Honeywell plant...
Investigators also are trying to determine if condensation on the plane seeped into the ELT, triggering a short circuit in the unit's lithium-manganese battery...
Boeing's chief 787 engineer, Mike Sinnett, told Reuters that the humidity controller on the 787, made by CTT Systems AB of Sweden, is designed to "dry out the crown" or upper fuselage, of the aircraft, and prevent moisture from accumulating. Without the system "we would wind up having that water stay in the insulation."
The AAIB also is looking at the placement of the ELT, which is bolted onto a bracket attached to the frame of the plane - exactly where condensation builds up...
Wet Were fires
back when the Lpckheed Jetstar came out, they had some peculiar fires involving the wiring. The installers were saving time in routing wires through clamps by using a bent set of needle nosed pliers to pull wites though. The teeth damaged the insulation leaving small pinholes.
Iworked at Lockheed New York and we viewed some films the investigators took through microscopes. of similiarly damage wires. The wires were charged to 28V DC and high humidity introduced. Under the microsope you could see, obviously in time lapse photography, a slow growth of copper crystall form between the cinductor, through the damage and work its way to the airframe which was at ground potential. The small current leak, using the moisture as a conductor was forming a thin film heater which in time grew to the point where it caused a fire. Lockheed New York rewired a number of Jetstars including some Air Force VIP aircraft.
The talk here of condensation and humidity coupled with a constant electrcal potential from a battery makes me wonder if the same mechansm might be at play in the 787.
Iworked at Lockheed New York and we viewed some films the investigators took through microscopes. of similiarly damage wires. The wires were charged to 28V DC and high humidity introduced. Under the microsope you could see, obviously in time lapse photography, a slow growth of copper crystall form between the cinductor, through the damage and work its way to the airframe which was at ground potential. The small current leak, using the moisture as a conductor was forming a thin film heater which in time grew to the point where it caused a fire. Lockheed New York rewired a number of Jetstars including some Air Force VIP aircraft.
The talk here of condensation and humidity coupled with a constant electrcal potential from a battery makes me wonder if the same mechansm might be at play in the 787.
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Interesting that Machaca's Reuter link was at 10.16 pm, the one in post 592 was at 6.37 pm and made no mention of pinched wires, clearly additional info led to the edited version. It is all starting to make sense.
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On wires and pinoles and damage
Interesting- not too long ago there was an article ( in a boeing publication as I recall ) about some major cost savings being implemented on the 737 program re wiring. Thge story went like this . At various suppliers tom prewired body and cockpit assemblies, the wire bundles were temporarily held together by plastic zip ties- ties by the hundreds as it turns out. So as they go to final assembly and routing, the ties had to be cut/removed and in some areas replaced after re routing. In the process, wires were sometimes nicked by the snippers used- and thus repairs/rewiring was a small but continuing issue. Someone suggested cost savings- it took about 2 years to implement- to use some form of removeable tape for the wirebundles instead of zip ties. Virtually eliminating the cuts and damage, etc and saving a lot of time.
Wonder if the 787 implemented the same method. ?? IMHO - I doubt it. It takes a long time to coordinate with ALL the suppliers, provide the tape, etc
I'll try to find the article and post it here later
Boeing’s Renton plant bustling despite job cuts elsewhere | Business & Technology | The Seattle Times
... The rate increases are achieved not only through reconfiguring the assembly lines but also through changes, suggested by employees, that can be small but have a dramatic impact.
On a tour of the assembly lines, Nishma Shrestha, lead engineer on 737 wire-installation design, said Boeing cut 15 hours of labor out of final assembly for each 737 with one change: having suppliers bundle wiring together with tape instead of plastic zip ties.
The plastic ties had required assembly mechanics to laboriously snip off the little nubs on more than 5,400 ties around the many wire bundles that go into each plane. The task was time-consuming and frequently led to mishaps with cut wires.
This apparently simple change, prompted by a study in 2010, required complex coordination and was finally implemented on all 737s in January....
Wonder if the 787 implemented the same method. ?? IMHO - I doubt it. It takes a long time to coordinate with ALL the suppliers, provide the tape, etc
I'll try to find the article and post it here later
Boeing’s Renton plant bustling despite job cuts elsewhere | Business & Technology | The Seattle Times
... The rate increases are achieved not only through reconfiguring the assembly lines but also through changes, suggested by employees, that can be small but have a dramatic impact.
On a tour of the assembly lines, Nishma Shrestha, lead engineer on 737 wire-installation design, said Boeing cut 15 hours of labor out of final assembly for each 737 with one change: having suppliers bundle wiring together with tape instead of plastic zip ties.
The plastic ties had required assembly mechanics to laboriously snip off the little nubs on more than 5,400 ties around the many wire bundles that go into each plane. The task was time-consuming and frequently led to mishaps with cut wires.
This apparently simple change, prompted by a study in 2010, required complex coordination and was finally implemented on all 737s in January....
Last edited by Jetdriver; 20th Jul 2013 at 17:48.
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The talk here of condensation and humidity coupled with a constant electrcal potential from a battery makes me wonder if the same mechansm might be at play in the 787
Every piece of equipment is tested for function under high humidity as part of qualification testing.
If the ELT is intended to be sealed - which it would be the case for equipment with an immersion spec - then it will not be expecting to be damp inside and I guess may not work too well if it is! The post above mentioned a 'wire entrapment' I suppose if Dr Murphy's law is working, that could have been the sole cause, wire trapped preventing case closing and sealing correctly plus insulation damage.....just a thought
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Every piece of equipment is tested for function under high humidity as part of qualification testing.
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Wonder if the 787 implemented the same method. ?? IMHO - I doubt it. It takes a long time to coordinate with ALL the suppliers, provide the tape, etc
Would be good for Boeing to become transparent about this whole issue....
Last edited by fenland787; 20th Jul 2013 at 18:23.
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If any wires were to become pinched, and if these wires only had a very thin layer of Teflon insulation, rather than much tougher PVC based coverings....
Last edited by joy ride; 20th Jul 2013 at 19:02.
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I have tried to troll trough all the info but cant see to find if there is any info as to why it set on fire yet?
Any news from Boeing yet or still all PPRUNE guess work?
Any news from Boeing yet or still all PPRUNE guess work?
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I think the assumption is that any wire that got pinched was internal to the ELT, so nothing to do with the airplane wiring. I'm puzzled by this insulation thing, it really didn't look much different from type 44 and the 230V wiring was better (thicker) insulated so no real difference from most airplane wires. I can always be proved wrong of course - it happens a lot! - but as far as this incident is concerned, the ships wiring could be a bit of a red herring.
PVC insulation is not permitted on aircraft, toxic when lit!
rather than much tougher PVC based coverings....
Last edited by fenland787; 20th Jul 2013 at 19:17.
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but as far as this incident is concerned, the ships wiring could be a bit of a red herring.
The only wiring to and from the ELT is control/data wiring which carrys miliamps of current and is not directly connected to the battery.
If any of these wires were incorrectly connected or short circuit it would cause logic problems for the ELT controller chip but it wouldn't catch on fire.
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The only wiring to and from the ELT is control/data wiring which carrys miliamps of current and is not directly connected to the battery.
If any of these wires were incorrectly connected or short circuit it would cause logic problems for the ELT controller chip but it wouldn't catch on fire
If any of these wires were incorrectly connected or short circuit it would cause logic problems for the ELT controller chip but it wouldn't catch on fire
remotely drop a piece of 12 gage or smaller wire across your 12 volt car battery AFTER clearing the area . .
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Hight current?
Sort of depends on what the control-data circuit wiring was shorted TO external to the ELT --for example like a 32 vdc bus bar or any power circuit or sneak circuit.
remotely drop a piece of 12 gage or smaller wire across your 12 volt car battery AFTER clearing the area . .
remotely drop a piece of 12 gage or smaller wire across your 12 volt car battery AFTER clearing the area . .
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Sort of depends on what the control-data circuit wiring was shorted TO external to the ELT --for example like a 32 vdc bus bar or any power circuit or sneak circuit.
An internal short circuit within the battery is a much more likely cause of a high current/high temperature condition.