FYI: nm = nautical miles, not nanometers.
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Can’t claim to be “mentally well”, whatever that might mean, but I definitely read it as nanometers.
Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
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Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#42If you want to, you can read the final report from the UK Civil Aviation Authority here: https://www.caa.co.uk/publication/download/23340
It's pretty readable and quite interesting.
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#43Good news: the system successfully detected an error and didn't send bad data to air traffic controllers. Bad News: the system can't recover from an error in an individual flight plan, bringing the whole system down with it (along with the backup system since it was running the same code).
> he system can't recover from an error in an individual flight plan, bringing the whole system down with it
From the system's POV maybe this is the right way to resolve the problem. Could masking the failure by obscuring this flight's waypoint problem have resulted in a potentially conflicting flight not being tracked among other flights? If so, maybe it's truly urgent enough to bring down the system and force the humans to resolve the discrepancy.
The systems outside of the scope of this one failed to preserve a uniqueness guarantee that was depended on by this system. Was that dependency correctly identified as one that was the job of System X and not System Y?
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#44Earlier quoted context omitted.
... or there's a software engineer somewhere who simply assumed that three letter navaid identifiers were globally unique, and baked that assumption into the code. I guess we now need a "Falsehoods Programmers Believe About Aviation Data" site :)
Or even more straightforward, just don’t believe anyone 100% knows what they are doing until they exhaustively list every assumption they are making.
Which also means never assume the exhaustive list is 100%.
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#45When there's no global clearing house for those identifiers, maybe namespaces would help?
Related: The editorialized HN title uses nanometers (nm) when they possibly mean nautical miles (nmi). What would a flight control system make of that?
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#46Earlier quoted context omitted.
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Sorry no. One interpretation, especially on this site, is that the problem was some kind of database bug, maybe where the same location was entered twice and a tiny location error ended up creating two locations. I expect that out of any random sample 500 million literate and mentally healthy English speakers, more than 450 million of them are totally unaccustomed to thinking about nautical miles ever. Even people in…
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Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#47You know there's a software engineer somewhere that saw this as a potential problem, brought up a solution, and had that solution rejected because handling it would add 40 hours of work to a project.
... or there's a software engineer somewhere who simply assumed that three letter navaid identifiers were globally unique, and baked that assumption into the code. I guess we now need a "Falsehoods Programmers Believe About Aviation Data" site :)
Did aviation software for 7 years. This is 100% the first assumption about waypoint / navaid when new devs come in.
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#48FYI: nm = nautical miles, not nanometers.
Nanometers would be a very short flight.
Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#49Re: Air traffic failure caused by two locations 3600nm apart sharing 3-letter code
#50FYI: nm = nautical miles, not nanometers.
man, this ruins everything.