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According to Bloomberg:
Boeing Co. told U.S regulators on Friday that it didn't see the need to undertake a potentially costly fix for a wiring issue on the company's grounded 737 Max, according to two people familiar with the briefing.
The planemaker found in an audit last year of the 737 Max that wires were bundled improperly in a way that could trigger a failure similar to what happened in two crashes of the plane in which a total of 346 people died.
U.S. law requires wiring that could cause a hazardous condition in a failure to be separated from other wires. [...]
The wiring issues have been found in more than a dozen locations on the 737 Max.
From The Seattle Times [May require that Ad-Blockers be switched off, or at least disable style sheets]:
During the original design and certification of Boeing's 737 MAX, company engineers didn't notice that the electrical wiring doesn't meet federal aviation regulations for safe wire separation. And the Federal Aviation Administration (FAA) failed to detect Boeing's miss.
The wiring vulnerability creates the theoretical potential for an electrical short to move the jet's horizontal tail uncommanded by the pilot, which could be catastrophic. If that were to happen, it could lead to a flight control emergency similar to the one that brought down two MAX jets, causing 346 deaths and the grounding of the aircraft.
Because this danger is extremely remote, the FAA faces a dilemma over what to do about it. The issue has complicated the return of the MAX to service after a grounding that is edging close to one year. [...]
"There are 205 million flight hours in the 737 fleet with this wiring type," a Boeing official said. "There have been 16 failures in service, none of which were applicable to this scenario. We've had no hot shorts."
In addition, Boeing says pulling out and rerouting wires on the almost 800 MAXs already built would pose a potentially higher risk of causing an electrical short, because insulation could chafe or crack in the process of moving the wires.
However, an FAA safety engineer familiar with the issue, who asked not to be identified because he spoke without agency permission, said agency technical staff have been clear that the wiring doesn't comply with regulations and have told their Boeing counterparts it has to be fixed.
(Score: 4, Interesting) by Runaway1956 on Sunday February 16 2020, @08:34AM (17 children)
Allow me to shed a little light on that? During manufacture of anything - cars, trucks, trains, ships, and aircraft, the thing is open, and it's easy to reach inside to put things like wires into their proper places. After manufacture, you can't just open the whole thing up with a can opener to gain access again.
Replacing wire looms will require pulling wires out, then pulling new wires in. Pulling wires, whether through conduit, or not, involves chafing against the corners in the conduit. Or, if not inside of conduits, then chafing against - whatever. Struts, inner surfaces of wings, debris left from the manufacturing process. (Some separate article a few months ago addressed debris left inside of aircraft - filings from drilling holes being the worst mentioned.)
I believe that Boeing's stance in this particular instance is almost certainly correct. The best solution at this point would be to open or create access panels in key locations to enable workers to install brackets to control how the wiring harnesses might be abraided.
A nice mental exercise - or even a real life physical exercise if you're really bored - get yourself a roll of wire, and thread it the length of your own car, make a U-turn, and thread it back the other way. That is, maybe an entry point at one headlight, exit through a tail light, re-enter at the other tail light, and exit at the opposite headlight. If there are any shorts when you finish, then you have failed the exercise. Hangers or other aids which would enable you to route the wire externally to the vehicle are prohibited, of course, all routing must be internal.
(Score: 5, Insightful) by sjames on Sunday February 16 2020, @09:18AM (11 children)
That's why a properly designed conduit has access points anywhere you might need to make a turn and at mid poinys for long runs.
Part of me can't help snickering just a little. For once it's the manufacturer of something that experiences the pain of repairing something that wasn't designed to be repaired.
(Score: 2) by Runaway1956 on Sunday February 16 2020, @09:50AM (1 child)
Just two weeks ago, I left a note for my boss, with a sentence to that effect. "Call the manufacturer, and tell them that we want their engineers to come out here and DEMONSTRATE how this is done!"
Odd that I didn't make that connection here. ;^)
(Score: 4, Insightful) by sjames on Sunday February 16 2020, @10:11PM
I would love to see more of that sort of thing.
Perhaps even as a reality TV sort of challenge. The engineering teams from the major auto manufacturers are forced to perform routine maintenance and common repairs on the car they designed live in prime time. They each get a set of standard tools that a well equipped shade tree mechanic might have.
If they have to call for a specialty tool, they lose points. If the tool is restricted by licensing or only available from the manufacturer, they get paddled with a shop manual by a select group of angry mechanics.
(Score: 0) by Anonymous Coward on Sunday February 16 2020, @02:26PM (1 child)
conduit weight reduces payload weight.
Incidentally the wiring spec isn't for how the wire performs when new. It is there because of how the wire performs after 20 years of chafe.
(Score: 2) by sjames on Sunday February 16 2020, @09:13PM
Where there isn't a conduit, access points are far more important.
And yes, the danger is that you might badly damage the insulation on installation such that at some future point it will fail due to further vibration and chafing while in service.
(Score: 2) by RS3 on Sunday February 16 2020, @08:54PM (6 children)
Absolutely agree. I've installed a few feet of conduit here and there. I'm a freak for deburring things, especially conduit ends. It only takes 2 seconds per end. Wires pull much easier, and without chafing.
NEC rules (not airplane obviously) limit a conduit run to a total of 360 degrees of curves, bends, elbows, etc., before you have to put in a "pull box" or some kind of access box.
I keep hearing about wiring problems in planes and I don't understand why they don't use conduit for all wiring.
(Score: 3, Interesting) by anubi on Monday February 17 2020, @12:50AM (5 children)
If anything, like a length of wire, is loose, it will vibrate and chafe. I had that problem show up on some oil tankers. Premium Teflon wire, too. Did not last a year. Failed by chafing against anything else by relentless vibration.
We had to rewire the whole engine circuits of those tankers. And this time, using lots of anti chafing and anti vibration measures.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 2) by sjames on Monday February 17 2020, @01:54AM
I remember something from years ago that a U.S. fighter plane frequently had that same problem (also with teflon wireing) but I don't remember which model.
(Score: 2) by RS3 on Monday February 17 2020, @03:02AM (3 children)
Good points. How about multi-conductor cables? I know some are designed for lots of flexing and vibration.
(Score: 1) by anubi on Monday February 17 2020, @08:21PM (2 children)
I did not see this in multiconductor cables, where the cable jacket secured the internal wires from rubbing against each other.
What got us was several individual wires, say 12 Gauge, stranded, in a half inch steel conduit They bounced around in there and the insulation began failing.
We replaced the wiring with some sort of neoprene armored ship rated cabling, and I never heard of any more problems. Sure taught me a lesson. After seeing what an expensive mess was made, I paid a lot more attention to detail from then on.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 2) by RS3 on Monday February 17 2020, @11:44PM (1 child)
Thank you, good to know!
Interesting about the wire (THHN?) in steel conduit problem. Again, possibly sharp edges?
I'm very particular about sharp edges- I hate them and remove them generally, and conduit is no exception- fitting, boxes, connectors, conduit itself. I notice people being lazy / negligent about using plastic bushings on fitting threads.
I've noticed many multi-conductor cables often have some kind of white powder everywhere inside. It seems to be a little slippery. I doubt it's talcum, but maybe something similar.
Anyway, maybe Boeing / other aircraft mfgrs. should plan harness design / layout based on multi-conductor cables which might be much more reliable.
(Score: 1) by anubi on Thursday February 20 2020, @02:39AM
You nailed it on the sharp edges. On disassembly and inspection of the failing wiring, it seemed every sharp edge and bend had left damage in the insulation.
I was a green engineer fresh out of college, working for Chevron at the time, and I was with a far more experienced engineer. I hold Chevron responsible for training me to be so perfectionist, by showing me what huge expensive messes we make when we ignore little details.
Seems like everyone learns this lesson the same way I did, and by that time, we are considered to be too set in our ways to be an obedient employee under some leadership type that has never experienced a good screwup. Types that emphasize shortcuts to maximize a bonus. If one thinks experience and education are expensive, try ignorance.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 5, Interesting) by TheGratefulNet on Sunday February 16 2020, @03:42PM
wiring harness systems are parts of the vehicle, these days.
I work at a car company, chinese owned, bay area located. the main office sent us cars built in china (for the china market), for us to work on and do tests on, write code for, do local test drives, etc.
on some early cars they shipped us, it had 'too old' of a harness installed and it was not compatible with the ecu's that the car had installed (or the ones that we were going to put on, as updates). it was close, but not close enough - and we could not flash upgrade all the ecu's on the harness system that was installed on *those* chassis.
I asked how much of a problem it would be to just swap out the old and put in a new. we work for the same company, we can order the harness as a whole and do the work. they laughed when I suggested that. it would be a whole car tear-down, re-do, we would not be sure *we* didn't nick a wire or make some mistake somewhere and it might be days or weeks of effort, without any reward. (our goal is not to get a customer car back to them, but to design brand new ones and test it all out, long before its even on a sales sheet anywhere).
in the end, we scrapped the whole set of cars. they were *flown* in from china to the bay area, for r/d work and yet had to be *thrown away* since the changes needed to make them useful is not worth the time it would take. time IS money.
I've also heard that it could be as much as 1/3 the cost of the car, in manuf cost of parts (BOM) - for the hand made wire loom harness that is laid in each car that is built, these days. lots of wires, lots of weight, connectors, plastic snap housings (expensive ones, has to be 'car grade') - there's often 1 or 2 people in design groups that do *just* harness mechanical and logistical design.
csb: I tried to convince our guys to try using fiber optics for networking. try and consider glass and plastic. see if any will meet our needs. so far, I could not convince anyone, but I still do think fiber is the better way for networks than copper, in a car. sadly, no one is doing it yet.
"It is now safe to switch off your computer."
(Score: 2) by Grishnakh on Sunday February 16 2020, @04:44PM
Replacing wire looms will require pulling wires out, then pulling new wires in. Pulling wires, whether through conduit, or not, involves chafing against the corners in the conduit. Or, if not inside of conduits, then chafing against - whatever. Struts, inner surfaces of wings, debris left from the manufacturing process. (Some separate article a few months ago addressed debris left inside of aircraft - filings from drilling holes being the worst mentioned.)
I believe that Boeing's stance in this particular instance is almost certainly correct. The best solution at this point would be to open or create access panels in key locations to enable workers to install brackets to control how the wiring harnesses might be abraided.
I completely disagree. You might be right: replacing them could indeed cause chafing problems because this is retrofitting. The BEST solution is this: scrap all the 737MAX airplanes and force them to start over and do it right this time. If this means Boeing goes bankrupt, then great! Let some other company buy up their assets for pennies on the dollar so we can have someone trustworthy building passenger aircraft instead. Maybe COMAC would like to buy up what's left of Boeing.
(Score: 2) by Coward, Anonymous on Sunday February 16 2020, @05:11PM
That would mean this kind of oversight (possibly intentional) will be tolerated. Bad incentive. I can just see Boeing deciding back in the day while upgrading the 737 NG to MAX and being fully aware of the compliance issue: Redesigning this harness is a PIA. We'll just keep the old wiring setup, and if anyone calls us on it, we'll lie and say we missed that detail.
Now they need the FAA to cover for them internationally, but with everyone hating on the US, it's a tough sell. Maybe Boeing engineers are tearing down an Airbus plane in some secret hangar, looking for a design flaw that can be use as a quid-pro-quo.
(Score: 3, Insightful) by edIII on Monday February 17 2020, @01:10AM (1 child)
You make very good, intelligent, and reasonable points. They make no fucking difference. The wires were not installed to required spec in the first place, because those hell-bound bastards know the FAA is weak and they're going to do what they think is reasonable. These are extremely reasonable safety factors that we're demanding be in place for consumer safety. If NASA were run private from the beginning, we'd have a shit ton of more dead astronauts, because they would be treated like Amazon/Walmart/Turn-of-the-century-toxic-industry workers. NASA prioritizes the safety of the crew above else, and airlines should be forced by law to design to the same standards.
If humanity survives and evolves, this type of comment from c-suite scum will be used to teach people the catastrophic results of letting sociopathic people to have power. It will then furthermore be used an example of how toxic Capitalism (unrestrained greed and heavy rewards for sociopathic behavior) results in great harm to the consumer, society, and our planet.
That being said, I'm from Las Vegas. If that greedy bitch is willing to bet no hot shorts for the next 5 billion flight hours, I'll play. He wins, he keeps his cock. Anybody dies from a hot short, and we publicly "clean & sweep" his ass like a Chinese Eunuch in the Imperial Court.
He wants to bet on my fucking life, we can all bet on his cock. Now let's see how adamant he is about not replacing all the wires, regardless of difficulty to get right. Guess what? If it can't be done..... then there are some big ass scrap yards in Tuscon I think.
There are no excuses for letting in defective products to our markets. We're not in the situation in which we have to settle for that bullshit. If that company goes under we will all be just fine. The IP will be distributed, and the market will rise to the occasion with a new manufacturer that can follow the fucking directions and work with regulators.
This Too-Big-To-Follow-The-Rules bullshit has to stop eventually, or will have to accept that regulations mean nothing because we have no way to enforce them. No way to punish the c-suites and clawback their wealth.
Technically, lunchtime is at any moment. It's just a wave function.
(Score: 2) by Knowledge Troll on Monday February 17 2020, @03:44PM
I read that and immediately laughed out loud. Above all else? On what planet? The Space Shuttle earned itself the award of being the most deadly space craft ever made. The original official estimate by NASA was one failure in never gonna happen so don't even worry about it. The Feinman analysis of the Challenger disaster back in the mid 80s came up with a failure estimate around 1 out of every 30 or 40 flights which wound up being very close to the actual vehicle failure rate observed in usage. The reason Challenger exploded was because of the booster design. The boosters were designed the way they were to ease transport after manufacturing. And the manufacturing requirements were set so the manufacturing was lucrative to some specific congressional districts. The boosters were designed with a priority on politics and not the safety of the crew.
Columbia exploded because NASA adopted a stance of "if it didn't cause a problem before, even though we know it's going wrong, then it won't cause a problem in the future." This was the same approach they took with the Challenger booster and launching in environments that are out of tolerance according to the manufactured spec. Here we have NASA prioritizing not being embarrassed over the safety of the human crew.
Finally the same boosters that were designed for politics have returned to use on the SLS so we again have design with priority on politics and not learning from their own visible and painful mistakes. I think NASA is cool too but they are fucking reckless at times.