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Long Uptime Makes Boeing 787 Lose Electrical Power
jones_supa writes: A dangerous software glitch has been found in the Boeing 787 Dreamliner. If the plane is left turned on for 248 days, it will enter a failsafe mode that will lead to the plane losing all of its power, according to a new directive from the US Federal Aviation Administration. If the bug is triggered, all the Generator Control Units will shut off, leaving the plane without power, and the control of the plane will be lost. Boeing is working on a software upgrade that will address the problems, the FAA says. The company is said to have found the problem during laboratory testing of the plane, and thankfully there are no reports of it being triggered on the field.
Finally!
IT support advice that's useful!
"have you tried turning it off and then back on?"
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I guess this might be due to a 32-bit signed integer being incremented at 100 Hz: 2^31 / 24 / 3600 / 100 = 248.5 days.
karma police: arrest this man, he talks in maths; he buzzes like a fridge, he's like a detuned radio. [radiohead]
A commercial plane will most probably undergo through several maintenance events and checks during that sort of time frame, where cycling the power is part of the procedure.
It's very reassuring to know that it probably won't happen.
It could be the overflow of a counter of 10ms intervals. There are 86400 seconds per day, so 8640000 10ms intervals per day ...
2147483648 / 8640000 = 248.55
The company is said to have found the problem during laboratory testing of the plane, and thankfully there are no reports of it being triggered on the field.
The spokesman continued, "The battery would have caught fire long before that integer overflow."
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
If it ever happened on a plane, then it means that the maintenance was intentionally skipped. If they reach 248 days of continuous operation then a number of significant maintenance cycles have been skipped (some 23-25 inspection / maintenance cycles that generally require shutting down the electrical system). The generators in question are attached to the engines. The engines have a overhaul schedule that is shorter than 248 days of continuous operation. If they managed to reach this point, then the major maintenance cycles have been skipped and the engines are long overdue for a tear down inspection and overhaul. Any plane which could reach this point, 248 days of continuous operation missing all of the required maintenance; this is not a plane (or an airline for that matter) which anyone should be flying on.
The reason for the three shifts was that we were using actual PFC computers connected to hardware that could simulate all the inputs and read all the outputs.
That hardware was a big complicated rack of electronics and there were maybe 8 or 10 such units in a lab.
As such, to optimize use of the facilities it was necessary to have three shifts 24 hours per day. This went on for a year or more.
Very good planning in fact.
Now I could tell you stories of the real corners cut to meet the schedule. But that's a complicated story.
Which is apparently what Windows does:
https://www.ctm-it.com/it-supp...
You'd think they would have learned since Windows 95/98 did the same thing.
https://support.microsoft.com/...
But hey, at least it goes 10 times as long now.
As a sidenote, there exists a somewhat famous bug in Windows 95 and 98 (later patched) that caused these operating systems to stop functioning after 49.7 days of uptime.
This story is being way overblown. Yes, it's a bug. Yes, it should be fixed. However...
248 days of continuous operation is well past the scheduled major maintenance for the aircraft. By this point, a 787 would have to go through many minor maintenance cycles which would have required shutting down the electrical system. In addition, loss of all 4 generators would not result in a loss of vehicle because there are batteries, an APU (a backup generator) and Ram Air Turbines (RATs), generators that deploy from the wing if the APU won't start. To have to rely on any of these would not make for a good day for the pilots; but, they would certainly provide the necessary power to safely land the aircraft at the nearest airport. They might even be able to continue on and finish their flight if they successfully reset the generators.
This is not the OMG Planes Are Going to Fall From The Sky! event the media is making it out to be.
In C, overflowing a signed integer type is undefined behaviour; unsigned type wrap around to zero in a defined manner.
Of course, either is often undesired, but the latter at least doesn't allow basically anything to happen.
CLI paste? paste.pr0.tips!
Only theoretical, though. Windows 9x would crash long before reaching this uptime.
"It's such a fine line between stupid and clever" -- David St. Hubbins, Spinal Tap
QC isn't just a department or a step in the release process, it is built into the full life cycle of the software. Safety is the goal, and the requirement for good practice starts at the beginning of the process, with the requirement documents.
For example, there are five levels of error severity defined from A to E. E has no impact on safety and A is catastrophic, where a crash could occur. The level of software test and validation depends on the severity level.
Your inability to find a "QC" position is because you don't know the structure of aerospace software development and have no idea of the job titles or terminology used to describe the standards used. You are projecting your lack of knowledge into a inconceivable lapse of competence on the part of Boeing and the FAA. In what universe would there be no software safety requirements for the civilian aircraft industry? All you have shown is that you are ignorant and have a basic lack of common sense.
Why is Snark Required?
And this is why C should never be used for mission critical software.
"It's such a fine line between stupid and clever" -- David St. Hubbins, Spinal Tap