I highly recommend finding a cloud chamber (various science museums have them) to visualize just how much radiation is flying around.
Part of my work touches high power switches. I am going to do a bad job relating this story, but one of the power engineers was talking about how electric train switches in EU (Switzerland?) were having triggering issues. These were big MW scale IGBTs, not something you want to false trigger. Anyway, they eventually traced the problem to cosmic rays, and just turned the entire package vertical so the die was end-on to space (the mountains around were shielding the horizontal direction), and the problem went away.
It's important to note that this is just Airbus's best guess as to the cause, as there's no smoking gun: they simply exhausted their troubleshooting and were left scratching their heads so this was the "least unlikely" cause they could come up with given the circumstances.
I thought the same, but in a deeper dive into the postmortem, I think it's not a cop out from their side. The report is actually really well done ( I personally was impressed). The reasons it probably was a bit flip is that the CPU did not have edac on it in this instance so bit flips are expected. The consensus mechanism failed in this case and that is what they are updating, because even though the module gave wrong data because of presumably bit flips, the consensus should have prevented the dive.
My reaction was initially that it was a cop out, but looking a bit in the report and thinking things through, I think that, yes, it's most likely a bit flip.
“ The increasing reliance of computers in fly-by-wire systems in aircraft, which use electronics rather than mechanical systems to control the plane in the air, also mean the risk posed by bit flips when they do occur is higher.”
Bit of an understatement. I don’t think there any active passenger airliners in the first world today that aren’t fly-by-wire. The MD-80 was the last of its kind and it’s been out of passenger operation for what, 10 years now?
Any Boeing other than 777/787 does not use fly-by-wire.
However, that doesn't illuminate the possibility of these errors. Whilst the flight-controls are mechanically linked, the autopilot/trim is electric, so is still suspectable to bit-flips.
Still a lot of software involved in controlling the aircraft. The 737 Max incidents were eventually tracked to software quality issues, IIRC. All those old designs are being upgraded with modern avionics, so even if the airframe and linkages are old-school, the inputs are being driven by digital computers. At least that’s my understanding. I confess to not being a “plane guy,” though I have spent a lot of time traveling in planes, and I have stayed at a few Holiday Inn Express hotels.
Boeing 717 is still in service and it's essentially an MD-80. Many 737s are in service and flight controls are hydraulic-boosted cable-and-pulley operated; the type design dates to the 1960s.
Not to mention, the system affected by the bit flips were designed in the 90's AND newer designed systems have EDAC so they are not susceptible to the same kind of issue. Honestly, if you look into the thing, the press coverage of the event is atrocious.
I feel like using "Cosmic Rays" as a reason is equivalent to "Aliens". It makes for good clickbait so everyone is fast to point at it as the reason even if there is no reason to actually believe that the bitflip was due to cosmic rays.
> even if there is no reason to actually believe that the bitflip was due to cosmic rays.
What if there is reason to consider it as it is actually a known, proven, observable phenomenon, especially one with greater likelihood/intensity as you climb in altitude, like planes do, and that likelihood/intensity also scales with solar cycle intensity, which we are currently experiencing the peak of?
Or perhaps you think the Aurora Borealis are because of Aliens too?
When you do Raman spectroscopy in a lab the software literally has an automatic cosmic ray rejection mode because for autonomy you are very likely to get cosmic ray initiated return signals over the course of a couple of hours.
"If the signal looks amazingly strong but unexpected and sharp, it's probably a cosmic ray" was what I was trained for.
In practice such an event is rare, and I would expect there to be enough shielding to avoid it from interfering with the electronics. The fact that there is no hard evidence is why it's hard to argue against this clickbait claim, since technically they could be right.
The cosmic radiation that reaches Earth's surface consists mainly of particles that cannot be stopped by thin shields (e.g. muons or other particles with very high energies), otherwise they would not have passed through the atmosphere.
So shielding is not a solution that can be applied in a vehicle. You need something like an underground bunker to be sure that no cosmic radiation can penetrate it.
The only reason that makes rare the events caused by cosmic radiation is that if those particles can pass through shields that means that in most cases they will also pass through the electronic devices without being absorbed and causing malfunction.
I thought planes had insane redundancy exactly so stuff like that don´t happen. How can a bit flip cause the system that controls altitude to malfunction like that?
From what I've heard (FWIW), Airbus released a version of the software for one of the flight computers that removed SEU protections (hence grounding affected models until they could be downgraded to the previous version).
There was still hardware redundancy though. Operation of the plane's elevator switched to a secondary computer. Presumably it was also running the same vulnerable software, but they diverted and landed early in part to minimize this risk.
Why would you ever expect one bit flip? You have a flip rate and you design your system to tolerate a certain bit flip rate. Assumptions made during requirements establishment were wrong and nature eventually let them know they had negative margin.
What if in the time between initialization of cosmic_ray to False, and the time this if statement executes, a legitimate cosmic ray flips the bool bit representing cosmic_ray?
This is a really good point and a common error in bit flip detection code. To avoid this kind of look-before-you-leap hazard the following is recommended:
This is silly. Rapidly refreshing the data that was (presumably) flipped by a cosmic ray last time won't do anything to prevent an error in whatever it hits next time. Unless the theory is that cosmic rays are somehow more likely to hit these particular bits compared to all the millions (billions?) of others in the system...in which case I have a different objection.
What is silly is media coverage of this. The error was in the ADIRU. They are updating the ELAC. The ELAC takes the decision based on multiple data streams from 3 ADIRU units and the issue being fixed is that it took the wrong decision. The ADIRU will probably continue having SEU but it will be fine.
Not all circuits are equally sensitive. The parts that are known to be sensitive or critical are protected by redundancies and error checking, which are probabilistic protection. You haven't completely eliminated the possibility of corruption, just made it incredibly unlikely. Refreshing your inputs is another form of probabilistic protection focused on mitigating the consequences.
we had a "historic bad solarweather" a bunch of years ago and i talked with a cyber cafe operator that "you could have more computers bluescreen on this week than usual".
to me it got really weird when he said later he really did, but honestly its 50/50 that could had been just incidental.
in another note there are some "rather intense" discussions when someone speedrunning a game gets a "unreproducible glitch" in their favor, some claim its a flaw from ageing dram hardware, but some always point that it could be a cosmic ray bitfliping the right bit. (https://tildes.net/~games/1eqq/the_biggest_myth_in_speedrunn...)
I thought some combination of error correction and redundant systems was already widespread in airplanes to prevent cosmic-ray induced errors. (GPT agrees.) What am I missing? I've read multiple articles on this, and none of them address the fact that the problem, at the level of detail described in the article, should have been prevented by technology available and widely deployed for decades.
You're missing that the systems were designed in the 90's and they had no edac on them but instead relied on redundancy and a consensus system. The fact bit flips happened is not why they grounded the things and updated sw, they grounded them to address the consensus algorithm in the other CPU that did not get the bit flips.
What do you think this adds? These things are sycophant confident idiots; they will agree and agree they're incorrect at the slightest challenge in the same interaction.
I highly recommend finding a cloud chamber (various science museums have them) to visualize just how much radiation is flying around.
Part of my work touches high power switches. I am going to do a bad job relating this story, but one of the power engineers was talking about how electric train switches in EU (Switzerland?) were having triggering issues. These were big MW scale IGBTs, not something you want to false trigger. Anyway, they eventually traced the problem to cosmic rays, and just turned the entire package vertical so the die was end-on to space (the mountains around were shielding the horizontal direction), and the problem went away.
Always good to support the IGBT community
LMAO!
That's very P. K. Dick. Or maybe more Heinlein.
It's important to note that this is just Airbus's best guess as to the cause, as there's no smoking gun: they simply exhausted their troubleshooting and were left scratching their heads so this was the "least unlikely" cause they could come up with given the circumstances.
I thought the same, but in a deeper dive into the postmortem, I think it's not a cop out from their side. The report is actually really well done ( I personally was impressed). The reasons it probably was a bit flip is that the CPU did not have edac on it in this instance so bit flips are expected. The consensus mechanism failed in this case and that is what they are updating, because even though the module gave wrong data because of presumably bit flips, the consensus should have prevented the dive.
I would argue that designing avionics without EDAC is negligent design by Airbus.
Most modern servers at least implement ECC on their RAM. I would expect flight electronics to be designed to a higher standard.
Multi-module consensus is a form of EDAC - it's exceptionally unlikely that multiple units will fail identically simultaneously.
Do you happen to have a link to that report?
Sure.
https://www.atsb.gov.au/sites/default/files/media/3532398/ao...
My reaction was initially that it was a cop out, but looking a bit in the report and thinking things through, I think that, yes, it's most likely a bit flip.
This is for a similar incident that happened in 2008, not the Jetblue incident from October of this year.
Oh my god, you are correct. I read the technical details and did not bother to check it's the same issue. I am mortified. Apologies.
Just like that Mario 64 speedrunner! People say it's like it's gospel, but it's really just a bunch of peoples best guess. No proof.
…but if I respond with this to a user’s bug report, I’m “not taking this seriously”…
“ The increasing reliance of computers in fly-by-wire systems in aircraft, which use electronics rather than mechanical systems to control the plane in the air, also mean the risk posed by bit flips when they do occur is higher.”
Bit of an understatement. I don’t think there any active passenger airliners in the first world today that aren’t fly-by-wire. The MD-80 was the last of its kind and it’s been out of passenger operation for what, 10 years now?
Any Boeing other than 777/787 does not use fly-by-wire.
However, that doesn't illuminate the possibility of these errors. Whilst the flight-controls are mechanically linked, the autopilot/trim is electric, so is still suspectable to bit-flips.
Still a lot of software involved in controlling the aircraft. The 737 Max incidents were eventually tracked to software quality issues, IIRC. All those old designs are being upgraded with modern avionics, so even if the airframe and linkages are old-school, the inputs are being driven by digital computers. At least that’s my understanding. I confess to not being a “plane guy,” though I have spent a lot of time traveling in planes, and I have stayed at a few Holiday Inn Express hotels.
The MAX issues are not software.
The plane is fundamentally unstable because of the huge engines (which they have to improve fuel efficiency).
The only way to correct that is software with an angle of attack sensor.
They only installed one sensor though.
Does that sound like a software error or a fundamental physical design flaw?
Boeing 717 is still in service and it's essentially an MD-80. Many 737s are in service and flight controls are hydraulic-boosted cable-and-pulley operated; the type design dates to the 1960s.
Don't passenger aircrafts have redundant systems, so if one computer flips, the backup takes over?
Not to mention, the system affected by the bit flips were designed in the 90's AND newer designed systems have EDAC so they are not susceptible to the same kind of issue. Honestly, if you look into the thing, the press coverage of the event is atrocious.
I swear to god I've been got by cosmic rays modifying a bit before when my boot order changes for random reasons
The Universe is Hostile to Computers - https://www.youtube.com/watch?v=AaZ_RSt0KP8
I feel like using "Cosmic Rays" as a reason is equivalent to "Aliens". It makes for good clickbait so everyone is fast to point at it as the reason even if there is no reason to actually believe that the bitflip was due to cosmic rays.
> even if there is no reason to actually believe that the bitflip was due to cosmic rays.
What if there is reason to consider it as it is actually a known, proven, observable phenomenon, especially one with greater likelihood/intensity as you climb in altitude, like planes do, and that likelihood/intensity also scales with solar cycle intensity, which we are currently experiencing the peak of?
Or perhaps you think the Aurora Borealis are because of Aliens too?
>also scales with solar cycle intensity
The article rebuked that claim, saying that day was average. There other things that can cause bitflips ti be more likely like heat.
When you do Raman spectroscopy in a lab the software literally has an automatic cosmic ray rejection mode because for autonomy you are very likely to get cosmic ray initiated return signals over the course of a couple of hours.
"If the signal looks amazingly strong but unexpected and sharp, it's probably a cosmic ray" was what I was trained for.
I should have clarified that I was talking about software bugs.
What evidence do you have that this wasn’t due to solar radiation?
In practice such an event is rare, and I would expect there to be enough shielding to avoid it from interfering with the electronics. The fact that there is no hard evidence is why it's hard to argue against this clickbait claim, since technically they could be right.
The cosmic radiation that reaches Earth's surface consists mainly of particles that cannot be stopped by thin shields (e.g. muons or other particles with very high energies), otherwise they would not have passed through the atmosphere.
So shielding is not a solution that can be applied in a vehicle. You need something like an underground bunker to be sure that no cosmic radiation can penetrate it.
The only reason that makes rare the events caused by cosmic radiation is that if those particles can pass through shields that means that in most cases they will also pass through the electronic devices without being absorbed and causing malfunction.
I thought planes had insane redundancy exactly so stuff like that don´t happen. How can a bit flip cause the system that controls altitude to malfunction like that?
From what I've heard (FWIW), Airbus released a version of the software for one of the flight computers that removed SEU protections (hence grounding affected models until they could be downgraded to the previous version).
There was still hardware redundancy though. Operation of the plane's elevator switched to a secondary computer. Presumably it was also running the same vulnerable software, but they diverted and landed early in part to minimize this risk.
So not just redundancy but layers of redundancy.
Why would you ever expect one bit flip? You have a flip rate and you design your system to tolerate a certain bit flip rate. Assumptions made during requirements establishment were wrong and nature eventually let them know they had negative margin.
Possibility of bit flips from cosmic radiation only really came to fore in 1990s, and some aircraft and parts predate that.
Smaller semiconductor feature size greatly increases the likelihood of these types of errors.
What if in the time between initialization of cosmic_ray to False, and the time this if statement executes, a legitimate cosmic ray flips the bool bit representing cosmic_ray?
Simple! Make it an int.
This is a really good point and a common error in bit flip detection code. To avoid this kind of look-before-you-leap hazard the following is recommended:
Ask-for-forgiveness as an error detection pattern avoids these kinds of errors entirely.ah, a classic TORTOF bug (time-of-ray, time-of-flip)
This is silly. Rapidly refreshing the data that was (presumably) flipped by a cosmic ray last time won't do anything to prevent an error in whatever it hits next time. Unless the theory is that cosmic rays are somehow more likely to hit these particular bits compared to all the millions (billions?) of others in the system...in which case I have a different objection.
What is silly is media coverage of this. The error was in the ADIRU. They are updating the ELAC. The ELAC takes the decision based on multiple data streams from 3 ADIRU units and the issue being fixed is that it took the wrong decision. The ADIRU will probably continue having SEU but it will be fine.
Not all circuits are equally sensitive. The parts that are known to be sensitive or critical are protected by redundancies and error checking, which are probabilistic protection. You haven't completely eliminated the possibility of corruption, just made it incredibly unlikely. Refreshing your inputs is another form of probabilistic protection focused on mitigating the consequences.
Why not ECC though? Unless this is a latched output of a robust system being held for use by another robust system I guess?
In another HN thread it was said that since several years there is in production a new model of the affected module that has ECC.
Despite that, most of the existing planes have an older model, which has not been upgraded.
ECC is one of the probabilistic protections I was talking about.
I had no idea this was a real thing - I always thought that xkcd comic[0] was just a random joke.
[0]https://xkcd.com/378/
It's literally one of the reasons ECC RAM exists.
To dial up the weirdness, sometimes the solar flare activity has spikes (https://www.spaceweatherlive.com/en/solar-activity/solar-fla...) and these have a mild relationship with the odds of having "bitflips" in that timeframe.
we had a "historic bad solarweather" a bunch of years ago and i talked with a cyber cafe operator that "you could have more computers bluescreen on this week than usual".
to me it got really weird when he said later he really did, but honestly its 50/50 that could had been just incidental.
in another note there are some "rather intense" discussions when someone speedrunning a game gets a "unreproducible glitch" in their favor, some claim its a flaw from ageing dram hardware, but some always point that it could be a cosmic ray bitfliping the right bit. (https://tildes.net/~games/1eqq/the_biggest_myth_in_speedrunn...)
I had no idea this was a real thing
Oooh, in that case I have another xkcd you might like, involving mint candies and soft drinks…
I thought some combination of error correction and redundant systems was already widespread in airplanes to prevent cosmic-ray induced errors. (GPT agrees.) What am I missing? I've read multiple articles on this, and none of them address the fact that the problem, at the level of detail described in the article, should have been prevented by technology available and widely deployed for decades.
You're missing that the systems were designed in the 90's and they had no edac on them but instead relied on redundancy and a consensus system. The fact bit flips happened is not why they grounded the things and updated sw, they grounded them to address the consensus algorithm in the other CPU that did not get the bit flips.
> GPT agrees
What do you think this adds? These things are sycophant confident idiots; they will agree and agree they're incorrect at the slightest challenge in the same interaction.