Caused uncommanded pitch down, could exceed structural integrity of aircraft. There are redundant units - unknown why this can happen given redundancy.
In my humble opinion, whenever someone dropped the idea... "Maybe it's solar radiation" it never was solar radiation. There was a subtle bug in the system or something. It's just such a cop-out to attribute it to, solar radiation, it's our profession's variant of magic.
I can't find any further information on this intel testing like what altitude they perform the tests at.
AMD has perform testing at data centers of different altitudes and there is some statistical significance in SRAM error rates. And that is typically only around 5000-6000 ft msl.
It's an interesting document, but I am unconvinced that data spikes mean environmental radiation driven data corruption. The fact that they have a certain pattern suggests it's not random.
They certainly do put a chapter with potential triggers down there, and it's a good take, you can't just discard the possibility. But above, they also have SW bugs as a potential trigger, so... Essentially, they don't know for sure yet.
> But above, they also have SW bugs as a potential trigger, so
They also did extensive tests and analyses and came to the conclusion that a bug was highly unlikely (they would never say that something is impossible, but it still is exceedingly improbable).
> Essentially, they don't know for sure yet.
That’s not a really fair assessment. Their conclusion is that they could not estimate the likelihood of a radiation effect, so in that sense they don’t know for sure. But they still eliminated a lot of options. Almost all of them, actually.
I think it's a quite fair assessment. It's not an indictment of their engineering or anything, but they can't say for sure what caused the issue and the analyzed all they could. The conclusion is "we don't know, we have some guesses". Probably it irks me the most because "cosmic rays" are impossible to prove. It's the perfect scapegoat. If I had a penny every time that someone put it out as the possible cause of a bug... I'd still be poor, but... well, I'd have a couple of pennies.
EDIT: On a deeper read, I am inclined to be a bit more charitable to this theory because, to my surprise: "As noted in section 3.5.2, the CPU module on units 4167 and 4122 did not incorporate EDAC"
I did not consider these units were _this_ old, so they did not have error correction on them. Nowadays, most every MCU has ECC on them. So, yes, without ECC the odds are quite larger that they DID get a "bit flip"
CGMthrowaway has an interesting comment on the other thread about this subject, that it's likely not solar radiation. "failing solid state relay or contactor on the shared avionics power bus" [1] Related to the previous 2008 incident on Qantas 72 that had similar characteristics.
> On the Qantas 72 flight (2008), the ATSB report showed the same power spike that upset the ADIRU also left tidy 1-word corruptions in the flight data recorder. Those aligned with the clock cycle, shared the same amplitude and were confined to single ARINC words. That is pretty much exactly the signature of a failing solid state relay or contactor on the shared avionics power bus (upstream of both FDR and fly by wire).
> Radation-driven bit flips would be Poisson distributed in time and energy. So that is one way to find out
I don’t think they did. Their analysis indicates that it could, and this analysis happened as part of an investigation of an incident, but they don’t say that was definitely the cause of that incident.