Caused uncommanded pitch down, could exceed structural integrity of aircraft. There are redundant units - unknown why this can happen given redundancy.
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.
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.
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"
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.
https://dl.acm.org/doi/10.1145/2503210.2503257
Planes are much higher than that in operation so get larger amounts of unfiltered solar flux.
This may be one of the causes of higher cancer rates in pilots, but eliminating other environmental causes may be difficult
https://www.cdc.gov/niosh/aviation/prevention/aircrew-cancer...
[1] https://news.ycombinator.com/item?id=46083560
> 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