This takes "switching if off and on again" to a new level.

Forums › Transport (cars, bikes and boats) › This takes "switching if off and on again" to a new level.

Aredwood

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Topic # 171895 4-May-2015 21:51

Boeing Dreamliners supposedly have a software fault that causes them to loose power due to the generators going into failsafe mode. After the plane has been run contionusly for 248 days. So the FAA has ordered them to be shutdown for an hour every 3 months.

http://www.nzherald.co.nz/business/news/article.cfm?c_id=3&objectid=11443089

But seriously, you can keep a Windows computer running for over 3 months. (and lots of servers out there that run without restarting for far longer). Yet they cant write code for a plane that can run without needing restarting. Surely they should have done more testing.

alexx

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Reply # 1297945 4-May-2015 21:58

Looks like they can go 248 days before there's a problem, so the three month recommendation appears to be the usual airline industry being cautious and making a conservative recommendation.

http://arstechnica.com/information-technology/2015/05/01/boeing-787-dreamliners-contain-a-potentially-catastrophic-software-bug/

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tardtasticx

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Reply # 1297949 4-May-2015 22:06

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I'm more amazed they leave them powered up for so long! But why is the fact they have to restart them such a big deal, it says it takes about an hour and costs $110. Do they really keep these things on 24/7?

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gzt

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Reply # 1297962 4-May-2015 22:38

nzherald: The United States Federal Aviation Administration said laboratory tests by Boeing had exposed a computer glitch in a 787 that was run continuously for 248 days and could cause it to lose power as generator units simultaneously went into failsafe mode.

Interesting the issue was found in the lab. That implies any of:

a) They upgraded test capability in some way since the original release
b) A lab simulator died unexpectedly and they had to investigate it
c) Conspiracy! the issue was not found in the lab!!

But anyway does the normal maintenance schedule not somehow result in a restart already prior to 248 days?

tripper1000

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Reply # 1297990 5-May-2015 04:03

There wouldn't be many aircraft that have power on for 200 plus days. Most Boeing's require hangaring for an A check every 60 days, for which power is shut down. The Dream-liner is an exception - it has been specifically engineered to reduce the requirement for scheduled maintenance in order to stay in service longer and make more money.

Windows may run for longer than the plane, but your average windows box does not have a fail safe mode in it that kicks in instantly and allows the mission to continue (sure there are exceptions in the server world).

Computers in planes have a hard life, but usually have parallel redundancy built in. Apart from getting jostled about constantly they are exposed to more environmental challenges than your windows box sitting in a server room. Not the least of these is increased levels of cosmic rays due to less atmospheric shielding, because the densest part of the atmosphere is below them not above them. This can cause 1 and 0's to be inverted within RAM, which will confound any computer.

Next time you jump on a fly-by-wire plane, think about single neutrino events talked about in the link below:

http://spacemath.gsfc.nasa.gov/engineering/3Page6.pdf

In response to the single neutrino events, cycling power during flight, of certain failed computers, is a manufacturer recommended procedure. However it is not acceptable to cycle the power on computers that repeatedly fail.

andrewNZ

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Reply # 1297998 5-May-2015 06:57

tardtasticx: I'm more amazed they leave them powered up for so long! But why is the fact they have to restart them such a big deal, it says it takes about an hour and costs $110. Do they really keep these things on 24/7?

Big planes only really get shut down for maintenance. Otherwise they're usually not on the ground for more than an hour or two at a time.

Fly somewhere, unload passengers and crew, load fresh passengers and crew. Rinse and repeat

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frankv

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Reply # 1297999 5-May-2015 07:00

gzt: Interesting the issue was found in the lab. That implies any of:

a) They upgraded test capability in some way since the original release
b) A lab simulator died unexpectedly and they had to investigate it
c) Conspiracy! the issue was not found in the lab!!

d) Was reported in the field, but confirmed in the lab.

Gilco2

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Reply # 1298037 5-May-2015 07:53

It is more common than many think. My brother a pilot for large airline says other planes have same problems and common to shut everything down completely disconnect all power for 5 minutes then connect power and start them up again. Just not common public knowledge it happens

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Dingbatt

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Reply # 1298049 5-May-2015 08:29

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Gee, so the media jumping on a non-story and blowing it up out of all proportion.

Worthy of the front page of the NZHerald (#shabbylittletabloid)? Meh, I don't think so.

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gzt

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Reply # 1298250 5-May-2015 11:41

frankv:
gzt: Interesting the issue was found in the lab. That implies any of:

a) They upgraded test capability in some way since the original release
b) A lab simulator died unexpectedly and they had to investigate it
c) Conspiracy! the issue was not found in the lab!!

d) Was reported in the field, but confirmed in the lab.

That's interesting. I have not seen that in any reports so far.

frankv

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Reply # 1298419 5-May-2015 14:15

gzt:
frankv:
d) Was reported in the field, but confirmed in the lab.

That's interesting. I have not seen that in any reports so far.

Well yeah, because I just made it up. And, if I was Boeing, you wouldn't see it anywhere either. But it is certainly the kind of spin that would happen.

Someone in the field will have noticed that suddenly all the generators stopped on an aircraft, and dutifully reported it. This would have gone through the usual support layers and so on, and eventually landed on the desk of a tech who hunted through the code, ran some simulations, and identified it as a software fault, then gone to some programmers to figure out what happened.

Technically, until a programmer said "Aha!" a bug hadn't been found. Until then, there's just some unexplained symptoms which could have been caused by anything. And it's much more palatable PR-wise to say "A software vulnerability has been identified in a lab" (which has this detached "A rat died after being fed 500 sachets of Big Mac sauce, its nothing to do with real life, but we do this because we care so much about our customers" feel to it) than "An aircraft's electrical power system failed completely at X, and another one in-flight, due to a bug we had no idea about... we don't know how many other bugs are still live".

I guess that (a) is just as likely, and I'll speculate that the "upgraded test capability" consisted of a graduate student doing a thesis on software reliability or testing, or maybe just an undergrad whose summer holiday job at Boeing was to port the generator controller onto an M16C.

No problem, nothing to see here, move along, move along....

Fred99

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Reply # 1300042 7-May-2015 17:17

tripper1000: There wouldn't be many aircraft that have power on for 200 plus days. Most Boeing's require hangaring for an A check every 60 days, for which power is shut down. The Dream-liner is an exception - it has been specifically engineered to reduce the requirement for scheduled maintenance in order to stay in service longer and make more money.

Windows may run for longer than the plane, but your average windows box does not have a fail safe mode in it that kicks in instantly and allows the mission to continue (sure there are exceptions in the server world).

Computers in planes have a hard life, but usually have parallel redundancy built in. Apart from getting jostled about constantly they are exposed to more environmental challenges than your windows box sitting in a server room. Not the least of these is increased levels of cosmic rays due to less atmospheric shielding, because the densest part of the atmosphere is below them not above them. This can cause 1 and 0's to be inverted within RAM, which will confound any computer.

Next time you jump on a fly-by-wire plane, think about single neutrino events talked about in the link below:

http://spacemath.gsfc.nasa.gov/engineering/3Page6.pdf

In response to the single neutrino events, cycling power during flight, of certain failed computers, is a manufacturer recommended procedure. However it is not acceptable to cycle the power on computers that repeatedly fail.

I presume that's a typo - neutrino vs neutron.

It's kind of interesting - and a little bit concerning possibly, as commercial jet liners are routinely flying at higher altitude, we have just had the weakest solar maximum for 100 years - following an extremely low solar minimum (and probably now descending into another very low solar minimum - solar wind deflects cosmic rays) and also composite materials probably offer less shielding than metal.

MikeAqua

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Reply # 1301975 11-May-2015 14:26

A dreamliner has two generators on each propulsion engine and two on the engine. It can fly/land on one engine and one generator. The chances of all three engine being run continuously over the same 248 day cycle are miniscule.

Flight control computers are triple redundant with dissimilar processing.

Mike