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http://www.theregister.co.uk/2015/05/01/787_software_bug_can_shut_down_planes_generators/
The US Federal Aviation Administration (FAA) has issued a new airworthiness directive (PDF) for Boeing's 787 because a software bug shuts down the plane's electricity generators every 248 days.
“We have been advised by Boeing of an issue identified during laboratory testing,” the directive says. That issue sees “The software counter internal to the generator control units (GCUs) will overflow after 248 days of continuous power, causing that GCU to go into failsafe mode.”
When the GCU is in failsafe mode it isn't making any power. That'll be bad news if all four of the GCUs aboard a 787 were powered up at the same time, because all will then shut down, “resulting in a loss of all AC electrical power regardless of flight phase.”
And presumably also turning the 787 into a brick with no power for its fly-by-wire systems, lighting, climate control or in-flight movies. The fix outlined in the directive is pretty simple: make sure you turn the GCUs off before 248 days elapse. Boeing is working on a fix and the FAA says “Once this software is developed, approved, and available, we might consider additional rulemaking.”
For now, before you board a 787 it's probably worth asking the pilot if he can turn it off and turn it on again.
(Score: 2) by darkfeline on Monday May 04 2015, @08:28AM
Centiseconds? That's not a very common way of expressing time. The only reason I can think of for using centiseconds instead of, say, milliseconds is that they were really tight on space on whatever embedded system this was on, but if that were true, why would they be using a signed int?
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(Score: 2) by maxwell demon on Monday May 04 2015, @05:46PM
Maybe because an unsigned short would already overflow after less than 11 minutes. I'm pretty sure that most flights take longer than that.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by darkfeline on Tuesday May 05 2015, @01:50PM
And an unsigned int would last twice as long as a signed int. I have no idea why you thought bringing up shorts was relevant.
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(Score: 2) by maxwell demon on Tuesday May 05 2015, @06:19PM
And an unsigned int is an invitation to introduce bugs due to signed/unsigned issues. Thanks to integer promotion, those are no issue for unsigned short.
Also, an unsigned int would not have saved a single byte compared to a signed int, and as already stated in another post, reaching the current limit is only a theoretical issue anyway.
Let me quote again from your post I had replied to (it was your own post, so one would think you knew what you wrote, and additionally I had quoted that part directly in my reply, but well …):
So what would you prefer to int when being tight on space: A type that uses less space than int, or a type that uses the exact same space as int?
The Tao of math: The numbers you can count are not the real numbers.