Japanese Probe Finds Miswiring of Boeing 787 Battery 201
NeverVotedBush writes in with the latest installment of the Dreamliner: Boeing 787 saga. "A probe into the overheating of a lithium ion battery in an All Nippon Airways Boeing 787 that made an emergency landing found it was improperly wired, Japan's Transport Ministry said Wednesday. The Transport Safety Board said in a report that the battery for the aircraft's auxiliary power unit was incorrectly connected to the main battery that overheated, although a protective valve would have prevented power from the auxiliary unit from causing damage. Flickering of the plane's tail and wing lights after it landed and the fact the main battery was switched off led the investigators to conclude there was an abnormal current traveling from the auxiliary power unit due to miswiring."
Yay, time for finger pointing (Score:3)
Re:Yay, time for finger pointing (Score:5, Insightful)
Outsourcing contractor.
Re:Yay, time for finger pointing (Score:4, Insightful)
Themselves? [dilbert.com]
Re:Yay, time for finger pointing (Score:5, Insightful)
A big chunk of the blame should go to whoever designed the connectors. For safety critical systems, it should be physically impossible to connect them in an unsafe configuration.
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Murphy strikes again! No, I'm not being sarcastic -that's the origin of the phrase - a cock-up concerning connectors that weren't one-way only.
Re:Yay, time for finger pointing (Score:5, Insightful)
Q: What is worse than a dumb guy?
A: A dumb guy with initiative.
Re:Yay, time for finger pointing (Score:4, Insightful)
Really? I am actually quite impressed. The degree of investigation over lighting failures and back up safety systems and all that is pretty awesome. Putting aside my condemnation of corporations like Boeing, this mess isn't damning, but rather assuring. Any finger pointing should be met with a reminder that the plane landed just fine. Granted, I'd be annoyed if my flight was grounded for this nonsense but degree of blame should reflect the problem caused.
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Those thinking this is "nonsense" should stop for a moment and recall what happened when pilots didn't take smoke warning seriously:
https://en.wikipedia.org/wiki/Swissair_Flight_111 [wikipedia.org]
Re:Yay, time for finger pointing (Score:4, Insightful)
I was just thinking that..the media will now have their blame game but at the end of the day it was a plane mishap that didn't include charred bodies strewn on the countryside. It was a glitch, that was easily fixed. I could have been much worse.
This whole idea of a wiring error sounds fishy and it seems to be based on flimsy evidence. These kind of things are proven by hard inspection of the aircraft, drawings, and designs not by observing flickering lights. Somebody in Japan wants these aircraft in the air really bad, and I'm betting they managed to talk Japan's version of the NTSB into this idea.
I'm waiting for the final report on this... Before I decide to get on one of these.. Because if this flimsy sounding reason is what I think it is, another plane is going to have a battery fire pretty soon and this time we might not be so lucky.
Re:Yay, time for finger pointing (Score:5, Informative)
You do realize that the flickering lights pointed investigators in a particular direction. THEN, after more analysis, they discerned the problem lay in miswiring. The flickering lights are not prima facie evidence of a wiring fault.
A bit more detail would be welcome. As it is, one cannot tell what happened or how many aircraft are affected.
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You do realize that the flickering lights pointed investigators in a particular direction. THEN, after more analysis, they discerned the problem lay in miswiring. The flickering lights are not prima facie evidence of a wiring fault.
A bit more detail would be welcome. As it is, one cannot tell what happened or how many aircraft are affected.
the Japanese government is not big on providing details. the culture is one where you trust your elders, and the government is the ultimate parent. personally, I resent that.
*bows head to dodge trolls*
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Yeah... I'm pretty curious what kind of valves they have on the power system to prevent damage per the TFA.
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A valve is also another term for a diode, which only allows current to flow in one direction.
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Re:Yay, time for finger pointing (Score:4, Insightful)
Re:Yay, time for finger pointing (Score:5, Insightful)
The length of the wires isn't a useful metric - it's the complexity of the wiring that causes miswiring.
Re:Yay, time for finger pointing (Score:4, Insightful)
At a guess, I'd say the total length of wiring might be indicative of complexity. The machines that I have worked on that have only a few hundred feet of wiring are generally less complex than machines with thousands of feet of wiring in them.
For comparison, find an old Farmall or John Deere tractor, and compare the wiring to your modern automobile. An elementary school child can figure out the wiring on an 50 to 80 year old tractor. Good luck with your car - experience mechanics have problems chasing down problems, especially intermittent shorts.
Re:Yay, time for finger pointing (Score:4, Insightful)
Only if you assume the topology is the same. The 747 is likely to be much more of a "star" topology with traditional circuit breakers. The 787 is more of a "bus" topology with solid-state relays.
Re:Yay, time for finger pointing (Score:4, Insightful)
Then compare a "modern" car with a very modern car. The huge mess of wires is being replaced by CAN and LIN buses.
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and older luxury cars are quite complex. not to mention the complexity of vacuum and mechanical linkages in old cadillacs etc..
Re:Yay, time for finger pointing (Score:5, Insightful)
And I don't mean adding stupid spoilers and boost chips and sillyness, I mean stuff like adding an extra pair of high beams that can be operated with the same button as the regular high beams. That will take some serious hacking on a modern car. If car manufacturers were good at making things, this wouldn't be a huge problem, but modern cars do so many things wrong that it's infuriating. Like putting lambertian leds in places where they should have put batwing ones, forcing me to put a diffuser in front of it so that my daughter is able to sleep in her car seat. Or making it a fifteen-minute job to remove the battery for charging it during the winter, when it should take two minutes. Or putting the light that activates when you open the trunk in the far left corner of the trunk, so that it doesn't light up anything if you actually have something in the trunk. I could go on about this for a while...
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I'd mod you up, but I've already commented, and I hate seeing that "undoing mods" bar of shame :-(
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Which makes it even harder - you could use a simple circuit tester in the past, now you need specialized software and a laptop.
Re:Yay, time for finger pointing (Score:5, Funny)
They originally planned to use 60 miles of wiring but then they only ordered 60 kilometers of wires so two thirds of the devices are not connected. It's not that big of a problem though since most things are covered by redundancy.
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ever actually have to trace wires on an aircraft?
i've worked on Huey and Cobras...small helos. And they can be a PITA to track things down.
And yes, i've found things that were caused by miswired connections, usually in the solder terminals of a switch.
so yes, i can easily see something simple like putting the wrong wire into the wrong terminal of a terminal lug/connector as all it was.
wouldnt be the first time, just like it wouldnt be the first time a tech manual drawing was unclear or even incorrect.
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That is important to keep in mind. Because of the things they did right, the thing they did wrong hasn't killed anyone.
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Yes, and how much are you willing to pay for your ticket/s?
Re:Yay, time for finger pointing (Score:4, Interesting)
Who will it be? Maintenance? Boeing?
All of the above!
I'm skeptical of this story. They are basically saying that somehow the wiring got messed up in such a way that everything still worked, but the battery was improperly charged/discharged by the APU. The evidence they have is some lights that flickered. This seems fishy to me.
If something is miswired, then it's going to be possible to PROVE that as fact. Even if the unit was cut from the aircraft, it would be possible to physically inspect and verify what wire went where. Flickering lights are NOT PROOF of anything being incorrectly wired.
If the drawings don't match the design, you can PROVE that by inspecting the drawings. If the aircraft doesn't match the drawings you can PROVE that by inspecting the aircraft. We have NO proof here.
I'm guessing that somebody in Japan wants to get these aircraft back into the air, bad enough to come up with some story with flimsy evidence and managed to get Japan's version of the NTSB to agree.
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Add to that that there were other, less severe but similar problems with the battery on other planes.
Also, I'd say (but nobody listens to me anyway) that if the battery can be misswired like that, it's a design flaw and Boeing should issue a correction. Of course, there is a lot of needed research before stablishing that the battery in fact has this problem, but that'd be the proper action.
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I'm skeptical of this story. They are basically saying that somehow the wiring got messed up in such a way that everything still worked, but the battery was improperly charged/discharged by the APU. The evidence they have is some lights that flickered. This seems fishy to me.
I tend to agree. The summary and TFA are so confusing, its hard to figure where exactly the miss-wiring was. Was it in the APU, or the APU's seperate battery, or the Main Battery, or what? They simply say the APU Battery was "incorrectly connected". Does that mean it was never intended to be connected to the main battery, or was reverse wired, or shorted or operates as a different voltages, or what?
So far Boeing is mum on this particular report.
Instead they are proceeding with insulation between battery [nytimes.com]
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They learned at least two things from this incident, not one. The first lesson is that it was "miswired" (agreed, a fishy statement), but it means they can test some wiring or insulation in existing and future planes to make people think they're doing enough to get the planes back in the air. Second, and more importantly, they learned that the batteries can burn as a group, and that they need to minimize the damage a battery fire can cause by better restricting the ability of the fire to spread. So the next
Re:Yay, time for finger pointing (Score:5, Insightful)
a wiring problem could be as simple as using an incorrect thermistor on a Li-ion pack or not wiring a thermistor in at all. These are often used to alter charge/discharge rates in response to the battery pack temperature. A battery will still work in every other respect, except it won't respond accordingly in response to overheating. This is a fairly simple example of what could go wrong to cause a fire that would not stop the battery from working (until it failed by going on fire). The trouble with Li-ion packs is that if this happens (and it does) then the fire can very easily spread to the surrounding cells. I can see how this could cause short voltage spikes that would overcome resistance in a line to "flicker" a light.
I'd just like to add, I may be totally wrong, but I thought I'd weigh in for the fair minded rather than the conspiracy theorists on this one. Also, before anyone assumes I'm a Boeing employee, I'm not. I'm just a bloke who works with Li-ion batteries and who has seen faults similar to this in the past.
Re:Yay, time for finger pointing (Score:5, Insightful)
During my tenure in aerospace, I had witnessed more and more of a disregard for detail work. What used to be a good thing called "attention to detail" started being regarded negatively as "being a perfectionist".
The devil is in the details. Thousands of things work perfectly. One does not. This is the inevitable result of overlooking just one detail.
Re:Yay, time for finger pointing (Score:5, Insightful)
I agree.
It shouldn't have been possible to "miswire" an aerospace battery, the connectors should have been coded, the wires, and the inspectors should have seen and tested this. Battery failure is still a process failure. Unfortunately, process failures are the most systemic failures possible. Lets hope I'm wrong....
andy
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It wasn't the battery itself that was miswired, it was the backup battery. It sounds like they have a second battery for when the first is unavailable, e.g. during fast charging. Lithium batteries get very upset if you try to charge them too quickly, or overcharge them or charge them while drawing significant current. Furthermore if the backup battery is not isolated correctly from the main battery the charging circuit may not be able to determine the main battery's state correctly and end up overcharging i
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I agree.
It shouldn't have been possible to "miswire" an aerospace battery, the connectors should have been coded, the wires, and the inspectors should have seen and tested this. Battery failure is still a process failure. Unfortunately, process failures are the most systemic failures possible. Lets hope I'm wrong....
andy
One must think about how aircraft are actually assembled. In most cases, wire bundles are installed without the terminating connectors installed on at least one end. This is because the connectors are too bulky to easily pull bundles though the small spaces required and it is difficult to know the exact length necessary to provide the proper clamping and clearances. It is simpler and cheaper to just install the wires and then cut them to length and install the connectors.
Manufacturing processes for aircr
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Boeing should have called the Call Center Help Line. The first question they always ask, is, "Is the device plugged in correctly?"
I find it mildly amusing that the Airbus A-800 also had problems with the wiring. They blamed that on a mismatch in CATIA system between French and German engineers.
It's amazing, all those high-tech doo-hickies, whatchits and gadgets in the plane. . . and in the end a wiring problem causes the system to fail. Maybe in the future, they can just all use one bus, and get rid of
Re:Yay, time for finger pointing (Score:5, Funny)
It wasn't me! I swear it wasn't me! I've never worked on an aircraft in my life!
Sux2bthatguy!!
(Note that Runaway is color vision impaired, and has in fact wired things wrong from time to time.)
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There are many...
User error (Score:5, Interesting)
So basically, the user reached back behind the power supply while fiddling and bumped the 110/220V switch, and it caught fire. Naturally, they didn't say anything to the tech after setting the switch back besides, "It just caught fire! All by itself!"
The user in this case is a giant airline company, and tech support would be Boeing. The FAA, of course, is the QA manager, who reviewed the call, and after reading the ticket closure notes, facepalmed, leaned back into his chair, and took a deep draft of coffee.
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Many power supplies are designed to autoswitch between 110V and 220V for just this reason. Cheap power supplies aren't.
I knew one customer that said: "We didn't know that it was a 220V machine when we connected it to 600V!" That bang was audible.
Re:User error (Score:5, Interesting)
No no, I know. I was just reframing the "black and nebulous art" of airplane maintenance into something easier to digest for slashdotters. It was either that, or a car analogy, and turning a plane into a car just felt wrong. :) The truth is a bit more complicated; But it still boils down to operator error and not a design flaw. Of course, a design that allows someone to plug in one component backwards and have the entire device go up in flames is not a good one, but it's not flawed in the strict sense of the word. It's disappointing that my $500 laptop has a feature that prevents the battery from being plugged in backwards, but a multi-million dollar state of the art aircraft does not.
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You can't use a car analogy because the average slashdotter would cause the same kind of problem if they worked on their car. Auto shops are always seeing cars come in after they tell the customer about a problem with something fixed totally wrong, parts put on upside down and crap like that. Most people know jack diddly about cars. This, frankly, is a positive thing. I look forward to when they're all EVs and we can know even less about cars to keep them maintained.
In any case, this is basically an ideal d
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Actually from my admittedly limited experience, FAA and airplane mfgrs are downright obsessive about making connections idiot proof and failsafe. It's pretty difficult to find places in an airplane where it's possible to plug the wrong things together or backwards. FAA has been dealing with Murphy for a very long time. In this case, if that's what happened, then it's one that slipped through the design and development process. FAA will mark this as a design failure and require Boeing to make it impossibl
Re:User error (Score:4, Informative)
Actually from my admittedly limited experience, FAA and airplane mfgrs are downright obsessive about making connections idiot proof and failsafe. It's pretty difficult to find places in an airplane where it's possible to plug the wrong things together or backwards. FAA has been dealing with Murphy for a very long time. In this case, if that's what happened, then it's one that slipped through the design and development process. FAA will mark this as a design failure and require Boeing to make it impossible to connect wrongly.
Looking at that Japanese powerpoint [mlit.go.jp], it looks like that may be exactly what happened. The battery cells are rectangular with a stud on each side of the top. Not even any prominent markings to indicate polarity, though the two studs seem to be mounted with different colored rivets. You'd think they'd at least have different diameter studs for the positive and negative, and jumpers with holes to match.
Re: the two studs seem to be mounted with differen (Score:2)
.
The other possibility is that the installer was color blind and has been able to get by without that disability showing through. Most items that are color-marked often have a redundant marking that is not dependent on color vision perception (except for resistors and their color banding indicators, http://e [wikipedia.org]
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This reminds me of when I was having a new furnace installed. The installer wiring up the thermostat was having a hell of a time because he was color blind (I helped him out there).
Looking at the pictures here though even a color blind person should be able to easily tell positive from negative on the battery terminals.
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actually at work we are dealing with that exact issue.customer returned an item that "stopped" working. After painfully trying to figure it out, we traced it to the power secondary power supply that converts 120 to 24v for the control systems. We replaced the PS tested the unit.
The customer had it for less than 20 minutes when they called up and said it wasn't working again. A quick check and the new power supply was toast.
They have a short in the box that supplies power to the unit in their shop droppi
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They have a short in the box that supplies power to the unit in their shop dropping 240v into the machine at random.
Most modern, well designed power supplies can handle anything from 95V through 250V because that is what they could expect on their input depending on where in the world they are used.
That's because they are switching power supplies, and instead of using a simple transformer to create the right internal voltage that is then rectified and provided to the powered equipment, they switch the incoming current to maintain the right voltage on the output.
Now, I'd like to know where this "120/240V" stuff regardi
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It was an analogy, bot really what is on the airplane.
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Back somewhere in the late 60's-early 70's, there was a computer that came in for repair in the company I worked for - it was an SDS 930 (lovely old discrete-transistor machine). Someone had plugged a "MagPack" (an early cartridge tape drive) into the wrong slot on the bus, and the connector that was supposed to go there, into the MagPack's bus. The connectors were the same, but the circuits weren't. The circuit plugged into the MagPack's slot got a good healthy dose of one phase of a 440v power supply i
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You gotta love Dell who decided to make their PC power supplies a proprietary pinout but use the standard ATX power supply connector. Many unsuspecting folks tried to replace either the power supply of the motherboard, only to smoke the motherboard because the pinout was non-standard.
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That reminds me of when I was working with an early revision of a new PCIe board. I double checked the auxiliary power connectors and found that they had used the wrong 8-pin connector. Instead of a PCIe power connector they used the motherboard power connector. The 8-pin PCIe power connector and 8-pin motherboard connectors are almost identical except the power and ground is swapped between the two and they're keyed slightly differently.It seems rather stupid to me. As far as I'm concerned they should have
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the old supplies with the 110/220 selector are switchers too -
No, old power supplies with a switch are not switchers. The switches on old supplies actually changed the selection of the primary on the transformer. Most of them had two primary windings. Wired in parallel, they handled 240V. Wired in series, 120V. That produced the right output from the secondary so you'd not over-voltage the regulators or dissipate excessive power dropping too high a voltage. If you didn't care about the dissipation, you could have a linear supply that ran on 120 or 240 without caring,
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SCREAM... PAF! (small mushroom cloud of oily capacitor smoke).
Maybe it was 120V after all...
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the old supplies with the 110/220 selector are switchers too -
No, old power supplies with a switch are not switchers. The switches on old supplies actually changed the selection of the primary on the transformer. Most of them had two primary windings. Wired in parallel, they handled 240V. Wired in series, 120V. That produced the right output from the secondary so you'd not over-voltage the regulators or dissipate excessive power dropping too high a voltage. If you didn't care about the dissipation, you could have a linear supply that ran on 120 or 240 without caring, you'd just have to make sure you rated all the components to handle the higher voltage.
Newer supplies that are switchers may still have a switch, but it really shouldn't be necessary in a well designed supply.
You're describing a simple transformer type of power supply. There are plenty of examples of switching supplies with a 120/240 switch. I've got a whole bunch of PC switching type power supplies with a 120/240 switch. Those supplies have two large caps that get charged to 120volts each. The switch controlled whether they were charged in parallel off the 120, or in series off the 240. Those caps fed the switching transistors.
Happened before (Score:5, Funny)
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A protective valve? (Score:3, Informative)
What is a power diode [slashdot.org]
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Perhaps they're using the term "valve" as a generic term to describe the behaviour, not the components used to implement it.
I wouldn't be surprised if they use transistors instead of diodes, to avoid the inherent voltage drop and subsequent power dissipation.
Re:A protective valve? (Score:5, Informative)
"Valve" is a generic term, slightly archaic for an electronic switch. Some vacuum tubes are called valves.
http://en.wikipedia.org/wiki/Vacuum_tube [wikipedia.org]
Since a transistor is simply a crystal triode, the terminology is reasonable.
http://www.beatriceco.com/bti/porticus/bell/belllabs_transistor.html [beatriceco.com]
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I think it means circuit breaker.
Japanese Probe? (Score:5, Funny)
When you say "Japanese Probe" I had an entirely different idea in my head regarding what this story was about.
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When you say "Japanese Probe" I had an entirely different idea in my head regarding what this story was about.
Weren't you surprised nothing was pixelated?
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I've learned not be surprised by anything I see from Japan.
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I'm still waiting for the tentacles.
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Tentacle porn is a reasonably good approximation of the 787s wiring diagram. And in both, bad things happen when the wires go in the wrong hole.
OK Now we are even (Score:2, Funny)
For the Prius accelerator screwup....
the safe way to do this (Score:2)
You need a blow-out panel.
The M1A2 Abrams tank has one for the shells. If they start to burn, the blow-out panel pops off and the whole mess exits the tank.
Factories that make vinyl have them. When the concoction goes boom, blow-out panels prevent total destruction of the building. Workers may even survive.
Meth labs don't have them. :-)
A reasonable design would have several battery compartments, each with a separate blow-out panel. These should be located so that debris will not enter the engines or get run
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Meth labs don't have them. :-)
Ahem,
Why do you assume just because I make meth, my lab is not set up to conform to AS2343 standards.
For shame sir, for shame.
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Remember that an airliner is a pressure vessel. The maximum pressure differential is on the order of 60 kPa, which is about the pressure of a water column 6m deep. So you want a panel which will absolutely not ever blow out at 60 kPa pressure, but will reliably blow out at (60 kPa + excess pressure caused by fire.) Given that the battery is not in a gas-tight compartment, I can't imagine that excess is very large, even for a significant fire. And all this is without even considering the fact that 60 kPa is
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Clearly not! If the 787 had blow-out panels, batteries could burn and/or explode with little consequence. The news stories would be about the danger to people on the ground, not to the aircraft.
(it goes BOOM, you get a nice neat predetermined circular hole in the bottom, and chunks of flaming battery fall from the aircraft... meanwhile, the aircraft continues operating on the other battery packs)
Lost in translation (Score:3)
I see that the discussion here is based on a sketchy summary from the originally Japanese press conference. More coherent information is available if you could read Japanese but I know it's too much to ask for...
Here is the latest update of the on-going investigation from the JTSB issued 20 Feb, 2013; this mentions the mis-wiring:
http://www.mlit.go.jp/jtsb/flash/JA804A_130116-130220.pdf [mlit.go.jp]
More in-depth information is given at
http://www.aviationwire.jp/archives/16032 [aviationwire.jp]
According to this article, the mis-wiring was in the original specs/design, and the design had been corrected. The aircraft in question was manufactured in accordance to the earlier specs but no modification was made to comply with the new ones. One can infer that the bug was considered insignificant to compromise the safety of the aircraft. The JTSB currently does not think this mis-wiring was the cause of the battery incident although they will keep looking into it as a potential cause of anomalous voltage readings.
Re:What? (Score:5, Funny)
Can't they make an idiot proof power plug?
Because idiots are much more resourceful than ordinary people.
Re:What? (Score:4, Interesting)
Because idiots are much more resourceful than ordinary people.
Behold! [brynmawr.edu]
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Never underestimated the ingenuity of dumb. I gave a guy a hard drive to replace the one in his computer. He 'knew all about it' and I knew he had the knowledge to format and reinstall his OS no problem.
He brought the drive back to me, claiming it didn't work, in fact the power cables would not fit till he took his dremel to them, so it must not have been the right drive for his machine.
He had shaved off the corners of a standard hard drive power connector so he could fit it upside down in a used 512 MB IDE
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They ended up with the safest plug in the world... that causes more foot injuries than any other plug.
Behold the BS1363, [wikipedia.org] bane of the foot.
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I love those plugs. I've lived in many countries and I've frequently had trouble with sockets that don't reliably make contact, wall warts that fall out of sockets and sockets that spark like July 4. The British plug doesn't have these problems. It just works. And you soon learn not to leave them lying about.
No argument here. the 2 pin US and Euro plugs seem to fall out if so much as a slight breeze hits them. A shame these plugs are so prevalent in Asia.
The Australian plug is the same, once it's in you know it'll take force to remove it, but a bit less deadly to tread on.
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Yes, but commercial airliners aren't built with plugs and sockets. For weight savings, everything is directly hardwired. At least, in pretty much every airliner prior to the 787, and I can't imagine Boeing changing that. Military aircraft are built with plug and socket connectors, but both sides of the connection are big bulky heavy metal components. When your plane is a cockpit and wings strapped onto a giant oversized turbine, you basically don't care about weight, but commercial airliners are the exa
Re:What? (Score:5, Insightful)
Yes, but commercial airliners aren't built with plugs and sockets. For weight savings, everything is directly hardwired. At least, in pretty much every airliner prior to the 787, and I can't imagine Boeing changing that. Military aircraft are built with plug and socket connectors, but both sides of the connection are big bulky heavy metal components
Do you have a reference for that? It doesn't make sense that field replaceable parts are hardwired in - you'd have to clip the wires to take it out, and every time you clip the wire it gets shorter, so eventually you'd have to run a new wire back to the source.
Even for parts that aren't replaced often, it seems that hardwiring would just increase the chance of error - if everytime they replace an engine someone has to sit down and manually splice 200 separate wires, that seems a lot more trouble prone than plugging in a dozen connectors that were wired in at the factory and tested on the factory test harness to be sure every wire was connected to where it should be.
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Slightly different, but my friend works for a company that makes in-flight video systems for planes including Lufthansa. While not mission critical, they still have to follow FAA and other regulations... one of which is some of the plugs they use plug in and then are secured in place with 12 to 16 screws even though the signals being passed are just network/video/audio.
I don't see why they couldn't use plugs of the same fashion instead of hard wiring everything
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I'd say in-flight video is mission critical, look at SwissAir 111. The company was so eager to cash in on midair gambling they overloaded the wiring with standalone power supplies rather than putting in a more sensible system. Crash. http://en.wikipedia.org/wiki/Swissair_Flight_111#TSB_findings [wikipedia.org]
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Hmmm -- a quick bing search for "aviation grade connector" shows lots and lots of connectors. There are even magazine articles about them.
http://www.aviationtoday.com/av/issue/feature/Product-Focus-Connectors_18865.html [aviationtoday.com]
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Posting to undo an egregiously stupid mod. #spamapology
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What in the world are you talking about? Very few connections are hardwired, almost everything has a plug, usually, a rotary cam-lock plug from Cannon, etc.
Do you think they solder all the avionics in place?
Re:What? (Score:4)
AFAIK you are completely incorrect. Just using the 787 for example, the entire thing is built in modules including wiring and all, that are built and tested by subcontractors and then plugged and bolted together at the Boeing assembly plant. All commercial aircraft that I am aware of at least since the 1940s has had connectors. The biggest problem with connectors is not the weight but the unreliability. Each connector is a potential point of failure, so aircraft electrical connectors are actually heavier - they have positive scraping between the two parts of each connection, often have moisture resisting / sealing. and have a threaded ring that holds them together. Then (IIRC) there is an additional set of tabs through which a wire is threaded and itself positively bound - used to be twisted, now I think they use a mechanical crimp. The wire assures that the threaded ring can not unscrew itself due to vibrations.
The most expensive cost for a commercial aircraft after fuel is the cost of downtime - time spent fixing things costs thousands of dollars per hour. Therefore everything on an aircraft is designed to be removed and disconnected quickly, efficiently and safely - including things like wings, tail fins, etc. FAA is not going to allow the mechanics to cut wires and fasten them back together, so again the connectors are designed so that each one can only go one way.
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I'm sorry; but, you're wrong. Work for a sensor manufacturer that sells to the aerospace industry and I can tell you, commercial aircraft cabling is full of connectors. Same kind of locking connectors found on military aircraft.
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Yes, but commercial airliners aren't built with plugs and sockets. For weight savings, everything is directly hardwired.
So they've managed to skim off maybe 10 pounds off the design of the aircraft, saving some several thousands in fuel costs over the operating life of the aircraft. A reasonable tradeoff considering the chance of the aircraft catching fire and then exploding when it hits the ground, killing everyone on board. *sips tea* Yeah. Makes sense to me. I mean, what's the cost of settling an accidental death claim for 300 people?
Here comes the math!
The cost of failure:
A product defect typically weighs in at $2.1 mi
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Um, you're off by two orders of magnitude. 171 miles / 100 feet = 9,029 connectors, not 902,880. So the failure rate cutoff (assuming the rest of your calculations are correct) works out to 1 in 3600. Care to re-analyze?
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That kind of math only works if electrical connectors are the sole reason for possible catastrophic failures that can be blamed on the manufacturer.
Since there are also possible hydraulic failures, wiring fires and so on, the manufacturer certainly needs a buffer larger than one in 36.
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Someday, people are going to look back on the outsourcing mania of core competencies by MBAs over the past generation as sheerest idiocy.
I think my grandad said the same thing about transistors. You'll rue the day you ever gave up on valves he'd yell...
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Asymmetrical plug/socket design. It's not that difficult.
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It may be you're right but the requirements might have led Yuasa to believe the battery management would be taken on by other system elements. Requirements writing is not all that easy, especially when you're trying to anticipate problems in equipment no one has had to rely on to such an extent before.
Damn fine work by the Japanese MoT nonetheless, aggregating clues from all over the place.
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Exactly! Wish I had points to mod you up.
Hell, even the lithium battery for my cordless drill has these basic smarts built in. Cutoff on any cell reaching it's upper voltage limit during charging, hitting the lower limit during discharge, or thermal limit during either charge or discharge. It also has cell leveling to keep all cells at a similar state of charge to maximize the overall useable capacity of the battery string.