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Comment by sxp | Hacker News Reader

The title sounds like speculative clickbait.

From https://www.airbus.com/en/newsroom/press-releases/2025-11-ai...:

  Analysis of a recent event involving an A320 Family aircraft has revealed that intense solar radiation may corrupt data critical to the functioning of flight controls.

This is different from the core claim that the incident was caused by radiation. What are the prior probabilities that the system was exposed to "intense radiation"? Vs some other mundane cause such as a faulty wire or mechanical issues? And what is the evidence supporting the former hypothesis?

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> What are the prior probabilities

100% for electronics operating at altitude. Also on the ground, but we mostly act like it doesn't happen and are usually ignorant of the root cause when it does.

100% of what? Those things have ECC and redundancy to the hilt. The data corruption odds are real and higher than one would expect but still not very high.

Look at pag 138...and correlation with altitude...: https://www.atsb.gov.au/sites/default/files/media/3532398/ao...

Yes, look at page 135 as well. They don't know, they have educated guesses. It could be SW, it could be hw.

EMI causing bugs is the equivalent of "bad juju".

My take was initially similar to yours but I have just updated it considering the affected units did not in fact have EDAC on them. With ECC, I would say the odds of having such an error decrease dramatically. But without it... yeah, I can believe it.

Where did you see that it didn't have ECC?

"As noted in section 3.5.2, the CPU module on units 4167 and 4122 did not incorporate EDAC, nor was it required by the aircraft manufacturer’s specification"

It was apparently added in a later HW revision

"The LTN-101 ADIRU’s CPU module was later redesigned to reduce costs and to include error detection and correction (EDAC). EDAC is used for detecting and correcting single-bit errors in RAM chips to give protection from single event effects (SEEs, see section 3.6.6). This change was a significant redesign and resulted in a new CPU module part number (466871-01). The EDAC was performed by a new ASIC, and all of the RAM chips used on the CPU module were replaced with a different chip.13"

https://www.atsb.gov.au/sites/default/files/media/3532398/ao...

Thanks; hmm but that means the version with EDAC has been in use since 2002, so is less likely related to todays update? (hth did they design stuff without protection back upto that point?)

It's not _only_ that, it's also the fact that the failure mitigation was not catching it, so even if they "fix" the random spikes issue, they still need to consider the "what if" issue if the thing _still_ happens. My money is that they will mitigate this:

"There was a limitation in the algorithm used by the A330/A340 flight control primary computers for processing angle of attack (AOA) data. This limitation meant that, in a very specific situation, multiple AOA spikes from only one of the three air data inertial reference units could result in a nose-down elevator command. [Significant safety issue]"

It's the only one marked "Significant safety issue" so my money is on that.

That's applicable for one specific model of ADIRU (basically determines where the aircraft is in 3d space in terms of position, rotation, velocities, and accelerations) from a single manufacturer (Litton). These aircraft have dozens of computers for different functions, many of them with multiple manufacturer options. There are at least 4 different ADIRU makers that airlines have been able to specify at different times including the Litton.

The ELACs (controlling the elevator and aileron actuators according to the demands computed by other functions) are made by Thales specifically for this aircraft type and probably have a quite different design.

The airworthiness directive replaces ELAC B L104 with ELAC B L103+, without giving a reason. Unless L103+ happens to have better shielding, it looks like another issue.

> What are the prior probabilities that the system was exposed to "intense radiation"?

I suggest trying to fly with a Geiger counter. At the cruise altitude you have something like 15-20x the normal background level, when flying over the pole it can rise to 30x.

It's actually not caused by the solar radiation, it's too weak to reach the flight level. It is caused by cosmic rays, and the solar activity modulates how much of the cosmic radiation reaches the lower levels of the atmosphere.

How can a ~bit flip can cause something that bad? It would mean everything else like you mention would also be that bad. Bad ram, bad hard disk, loose wire, bird hits the plane, everyone jumps at once, leaking military jamming.

Radiation should be covered under normal safety, along with they already shield for it.

People often wrongly blame things on radiation, bit flips etc. when they don't know the real cause. A well known pattern.

There is a Hacker News item that was on high repeat where they eventually they solved the ~'cosmic radiation bug' as they first called it. Cannot remember the link.

It will not be true no matter what the, I know 'interesting' facts, 'I have a wiki link', crowd tell you. Real life is boring (and amazing). See Heisenbug's - https://en.wikipedia.org/wiki/Heisenbug

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