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from the have-you-tried-turning-it-off-and-back-on-again? dept.
Submitted via IRC for Bytram
Airbus A350 software bug forces airlines to turn planes off and on every 149 hours
Some models of Airbus A350 airliners still need to be hard rebooted after exactly 149 hours, despite warnings from the EU Aviation Safety Agency (EASA) first issued two years ago.
In a mandatory airworthiness directive (AD) reissued earlier this week, EASA urged operators to turn their A350s off and on again to prevent "partial or total loss of some avionics systems or functions".
The revised AD, effective from tomorrow (26 July), exempts only those new A350-941s which have had modified software pre-loaded on the production line. For all other A350-941s, operators need to completely power the airliner down before it reaches 149 hours of continuous power-on time.
Concerningly, the original 2017 AD was brought about by "in-service events where a loss of communication occurred between some avionics systems and avionics network" (sic). The impact of the failures ranged from "redundancy loss" to "complete loss on a specific function hosted on common remote data concentrator and core processing input/output modules".
In layman's English, this means that prior to 2017, at least some A350s flying passengers were suffering unexplained failures of potentially flight-critical digital systems.
Not a power of two. I wonder why 149 hours?
(Score: 0) by Anonymous Coward on Friday July 26 2019, @09:50PM
Ok. That makes more sense. I was thinking of a tick rate of one per some standard or base 10 unit of time. Any other rate didn't occur to me. But yes 2^32 events divided by 8000 events per second is equal to 149 hours, 7 minutes, 50 seconds, and 114/125ths (7296 events).
Given that, the explanation given makes sense, something counts up somewhere and then divides by zero after rolling over. Although I could have sworn C had a way to detect overflows (or maybe C++ or C#? Don't know, am a mostly-Python guy), I always do a check on ctypes to make sure that the greater than or less than relationship I'm expecting holds. The same holds with the languages I know that do check that anyway. So, I can't believe they would miss something so obvious; but, then again, I've seen people cause all sorts of problems by not understanding the basics (/ returns a float, // returns floored integer, but the code uses both (usually verbatim copies from the internet)).