[HN Gopher] Airbus A320 - intense solar radiation may corrupt da...
       ___________________________________________________________________
        
       Airbus A320 - intense solar radiation may corrupt data critical for
       flight
        
       Author : pyrophoenix
       Score  : 474 points
       Date   : 2025-11-28 21:40 UTC (1 days ago)
        
 (HTM) web link (www.airbus.com)
 (TXT) w3m dump (www.airbus.com)
        
       | ChrisArchitect wrote:
       | More discussion: https://news.ycombinator.com/item?id=46082296
        
       | jMyles wrote:
       | This is one of the rare cases where, IMO, it makes sense to use a
       | modified title as you've done here.
        
       | op00to wrote:
       | Solar radiation like solar wind, or sunlight? They don't say.
        
         | mr_toad wrote:
         | "Analysis of a recent event"
         | 
         | I presume they mean a Coronal Mass Ejection.
        
           | fwip wrote:
           | I feel like the event was something that happened to a plane.
           | That said, I wouldn't think sunlight would be penetrating to
           | the chips running the plane.
        
             | dtagames wrote:
             | Gamma rays penetrate everything and have definitely been
             | known to disrupt computer circuits.
        
               | fwip wrote:
               | Yes, which is why the solar flare scenario makes more
               | sense.
        
             | awesome_dude wrote:
             | > The grounding of Airbus A320neo aircraft around the world
             | can be traced back to an incident on a JetBlue flight
             | operating a Cancun to New Jersey service on 30 October.
             | 
             | > At least 15 passengers were injured and taken to the
             | hospital after a sudden drop in altitude on the flight from
             | Mexico was forced to make an emergency landing in Florida,
             | US aviation officials said at the time.
             | 
             | > The Thursday flight from Cancun was headed to Newark, New
             | Jersey, when the altitude dropped, leading to the diversion
             | to Tampa International Airport, the US Federal Aviation
             | Administration said in a statement.
             | 
             | > Pilots reported "a flight control issue" and described
             | injuries including a possible "laceration in the head,"
             | according to air traffic audio recorded by LiveATC.net.
             | 
             | > Medical personnel met the passengers and crew on the
             | ground at the airport. Between 15 and 20 people were taken
             | to hospitals with non-life-threatening injuries, said
             | Vivian Shedd, a spokesperson for Tampa Fire Rescue.
             | 
             | > Pablo Rojas, a Miami-based attorney who specialises in
             | aviation law, said a "flight control issue" indicated that
             | the aircraft wasn't responding to the pilots.
             | 
             | https://www.stuff.co.nz/travel/360903363/what-happened-
             | fligh...
        
               | lostlogin wrote:
               | > At least 15 passengers were injured and taken to the
               | hospital after a sudden drop in altitude on the flight
               | from Mexico was forced to make an emergency landing in
               | Florida, US aviation officials said at the time.
               | 
               | I'm surprised passengers are allowed to unbuckle for so
               | much of each flight. You can get injured while buckled
               | it, but that seems less common.
        
               | MaxfordAndSons wrote:
               | The flight attendants/safety card will tell you to stay
               | buckled whenever seated, even if the seat belt sign is
               | off, but many (most?) people will ignore that guidance
               | and stay unbuckled for as long as they are technically
               | allowed.
               | 
               | Only aviation professionals or recovering flight phobics
               | like me who have watched every episode of Air Crash
               | Investigation will take proactive safety measure of their
               | own accord. To normies it's all just a pointless hassle.
        
               | sailfast wrote:
               | I stay buckled and I'm just a "normie" not afraid of
               | flying that understands turbulence doesn't always happen
               | in a bell curve with some notice. Not sure if that makes
               | you feel any better? :)
        
               | MaxfordAndSons wrote:
               | Having an understanding of the bell curve of turbulence
               | makes you a bit more advanced than a normie on the
               | aviation knowledge bell curve imo :)
        
               | baq wrote:
               | People have different priors for bad things that can
               | happen on a plane. If you've experienced turbulence
               | you'll probably buckle up.
        
               | danmaz74 wrote:
               | I'm not flight phobic but I still stay buckled all the
               | time when I don't need to move. It's a very little
               | nuisance.
        
               | seg_lol wrote:
               | No reason to not buckle, I keep the belt a little looser,
               | but buckled the entire time. Esp on Boeing planes, I want
               | to get sucked out with the seat.
        
               | rainsford wrote:
               | I'm amazed how many grown ass adults on airplanes act
               | like little kids when it comes to seat belts and
               | basically everything else.
               | 
               | Not just ignoring flight crew advice and common sense to
               | generally stay buckled in order to gain maybe a minor
               | amount of comfort and convenience being unbuckled, but
               | unbuckling even when the seat belt sign is on and again
               | common sense says being buckled in is the smart move. On
               | my most recent flight I heard quite a few people
               | unbuckling their seat belts while the plane was still
               | rolling down the runway after landing. You couldn't wait
               | 5 more minutes until the plane is at the gate?
        
               | MaxfordAndSons wrote:
               | lol yep. It's like they have the same mentality as being
               | a schoolbus (which, it's similarly wild to me that kids
               | are just implicitly allowed to not wear their seatbelts
               | on them but I guess thats an even more intractable
               | enforcement problem).
               | 
               | Also: people clapping the second the back wheels touch on
               | landing is particularly hilarious to me because it
               | implies an acknowledgement of the precariousness of
               | flying, but a complete ignorance of the fact that you're
               | just entering the second most dangerous 30 seconds of the
               | entire flight.
        
           | bparsons wrote:
           | There was a very large CME ten days ago. The NOAA scale had
           | predicted a high likelihood of disruptions, and had
           | specifically suggested that spacecraft and high altitude
           | aircraft could be impacted.
           | 
           | https://www.swpc.noaa.gov/noaa-scales-explanation
           | 
           | https://kauai.ccmc.gsfc.nasa.gov/CMEscoreboard/prediction/de.
           | ..
        
             | glaucon wrote:
             | FWIW the "industry sources say" line on the incident is
             | that it occurred on 30 October[1], so further back than ten
             | days ago but of course there may have been other CME
             | incidents at that time.
             | 
             | The European Agency Aviation Safety Agency [2] instruction
             | describes the characteristics of the incident but not the
             | date.
             | 
             | [1]
             | https://www.theguardian.com/business/2025/nov/28/airbus-
             | issu...
             | 
             | [2] https://ad.easa.europa.eu/ad/2025-0268-E
        
         | tyingq wrote:
         | Would guess "cosmic rays". Sun Microsystems had a batch of
         | UltraSparc servers that were very sensitive to it, and it was a
         | big issue.
         | 
         | https://docs.oracle.com/cd/E19095-01/sf4810.srvr/816-5053-10...
         | 
         | https://en.wikipedia.org/wiki/Cosmic_ray
        
       | addaon wrote:
       | I'd really, really like to know what microcontroller family this
       | was found on. Assuming that this is a safety processor (lockstep,
       | ECC, etc) it suggests that ECC was insufficient for the level of
       | bit flips they're seeing -- and if the concern is data
       | corruption, not unintended restart, it means it's enough flips in
       | one word to be undetectable. The environment they're operating in
       | isn't that different from everyone else, so unless they ate some
       | margin elsewhere (bad voltage corner or something), this can
       | definitely be relevant to others. Also would be interesting to
       | know if it's NVM or SRAM that's effected.
        
         | jayanmn wrote:
         | I am worried about a software fix for what looks like hardware
         | problem.
        
           | afavour wrote:
           | It could be as simple as storing multiple copies of the
           | relevant data and adding a checksum, something like that.
           | 
           | Hardware fix is the ultimate solution but it might be
           | possible to paper over with software.
        
           | kachapopopow wrote:
           | software fixes are totally fine since the chance of two
           | redundant pairs failing within the time it takes to correct
           | these errors is more zero's than there are atoms in the
           | universe. (each pilot has a redundant computer and because
           | there's two pilots there's two redundant pairs)
        
           | themerone wrote:
           | Gracefully handling hardware faults is a software problem.
           | The Air France Flight 447 crash was the result of bad
           | software and bad hardware.
        
             | vel0city wrote:
             | I'm reminded of the Apollo moon landing where the computer
             | was rapidly rebooting and being in an OK-ish state to
             | continue to be useful almost immediately
        
               | CrossVR wrote:
               | It wasn't rebooting, it ran out of memory and started
               | aborting lower priority tasks. It was a excellent example
               | of robust programming in the face of unexpected usage
               | scenarios.
        
               | f1shy wrote:
               | Of topic for the thread, but on for the comment: I was
               | working in an automotive project 3 years ago. It was all
               | about safety, and one hypothesis was the processor could
               | get overloaded. I was astonished no one in a grouo of 20
               | "senior sw architecs" had any idea about the concept of
               | load shedding. The proposed solution was "in that case,
               | reboot".
               | 
               | Mind you whatever came out of that project is rolling on
               | the street today.
        
               | concinds wrote:
               | We really should mandate all that stuff to be open-
               | source, so we can be aware of how defective everything
               | is.
        
               | K0balt wrote:
               | Fail safe/fail soft
               | 
               | I still design this into many of the things I work on,
               | especially if I'm working close to the metal on
               | controller systems. At some point it becomes ridiculous /
               | impossible but I'm often thinking about how a system
               | would handle memory corruption, bit flips, invalid sensor
               | data, etc. These days, somebody should design a triple
               | redundant microcontroller that runs quorum on the gpio at
               | the hardware level. It could be a 0.30 part instead of
               | 0.10 one, but I would specify it just about everywhere.
               | Add $3 to BOM cost to categorically eliminate an entire
               | class of failure would be ramrodded by legal into just
               | about every medical device, PLC, critical automotive
               | system, etc one would think. Seems like a good gambit for
               | a riscV startup, but what do I know.
        
             | f1shy wrote:
             | And bad pilot training, if I recall correctly.
        
               | amelius wrote:
               | I suppose because they were not instructed to work around
               | the software and hardware flaws.
        
               | janeric1 wrote:
               | Because they kept pitching up in a stall
        
               | f1shy wrote:
               | And two pilots were trying to fly the plane without
               | talking to each other. One learned "if something happens
               | just pull back, this plane cannot stall". No pilot
               | learned to say "my plane" when flying. Way too many
               | errors.
        
               | f1shy wrote:
               | No. The behavior was wrong, no matter what you are
               | flying. Same problem with proper training would have
               | result in a simple report.
        
             | foldr wrote:
             | Crashes caused by pilots failing to execute proper stall
             | recovery procedures are surprisingly common, and similar
             | accidents have happened before in aircraft with traditional
             | control schemes, so I'm skeptical that there are any
             | hardware changes that would have made much difference. The
             | official report doesn't identify the hardware or software
             | as significant factors.
             | 
             | The moment to avoid the accident was probably the very
             | first moment when Bonin entered a steep climb when the
             | plane was already at 35,000 feet, only 2000 feet below the
             | maximum altitude for its configuration. This was already a
             | sufficiently insane thing to do that the other less senior
             | pilot should have taken control, had CRM been functioning
             | effectively. What actually happened is that both of the
             | pilots in the cockpit at the start of the incident failed
             | to identify that the plane was stalled despite the fact
             | that (i) several stall warnings had sounded and (ii) the
             | plane had climbed above its maximum altitude (where it
             | would inevitably either stall or overspeed) and was now
             | descending. It's never very satisfying to blame pilots, but
             | this was a monumental fuck up.
             | 
             | If the pilots genuinely disagree about control inputs there
             | is not much that hardware or software can do to help. Even
             | on aircraft with traditional mechanically linked control
             | columns like the 737, the linkage will break if enough
             | pressure is applied in opposite directions by each pilot (a
             | protection against jamming).
        
               | julik wrote:
               | True. I would say, however, that every "concept" of
               | airliner flight deck has its own gimmicks that can kill.
               | The Airbus "dual input" is such a gimmick. Even though
               | there was, for example, an AF accident with a 777 where
               | there was hardware linkage between yokes and the two
               | pilots were fighting... each other. Physically.
        
               | foldr wrote:
               | The official report doesn't identify the lack of
               | sidestick linkage as a factor in the accident. Neither of
               | the two pilots who were at the controls had any idea what
               | was happening. Both pulled back on their sticks
               | repeatedly right up to the moment of impact. The captain,
               | who eventually realized (too late) that the plane was
               | stalled, was standing behind them, and so would not have
               | benefited from linked sticks.
               | 
               | There's a detailed breakdown here:
               | https://admiralcloudberg.medium.com/the-long-way-down-
               | the-cr...
        
           | willis936 wrote:
           | It's a system problem. The system is being fixed.
        
         | TehCorwiz wrote:
         | An early revision of the Raspberry Pi 2 would crash if you hit
         | it with a bright light like a camera flash. Specifically a
         | xenon flash.
         | 
         | https://forums.raspberrypi.com/viewtopic.php?t=99167
         | 
         | https://forums.raspberrypi.com/viewtopic.php?f=28&t=99042
         | 
         | https://www.raspberrypi.com/news/xenon-death-flash-a-free-ph...
         | 
         | https://www.youtube.com/watch?v=wyptwlzRqaI
        
           | mlyle wrote:
           | Yah, but that's a case of the package not being opaque
           | enough.
        
           | russdill wrote:
           | Completely unrelated and due to a design failure by the rpi
           | folks.
        
             | hughw wrote:
             | Is it really so unrelated? Isn't it a case where a similar
             | phenomenon -- radiation impacting a computer calculation --
             | happened and it's one we can all relate to more easily, and
             | reproduce if we cared to, than high altitude avionics? Not
             | necessarily disputing but it just seems like a relatable
             | case that helps me understand the issue better. If it's a
             | radically different case somehow I'm interested to learn.
        
               | russdill wrote:
               | No, because it's a completely different kind of
               | radiation.
        
               | hughw wrote:
               | Different band, sure. Same principle, right?
        
               | russdill wrote:
               | The difference between ionizing and non-ionizing
               | radiation is quite different. But for much of the
               | radiation effecting electronics at high altitudes it's
               | largely subatomic particles.
               | 
               | And of course you can block the type radiation that
               | caused problems for the rpi with a good piece of paper.
        
               | hughw wrote:
               | Got it. Ty.
        
         | anonymousiam wrote:
         | proper SEU mitigation goes far beyond ECC. Satellites fly
         | higher than the A320, and they (at least the ones I know about)
         | use Triple Modular Redundancy:
         | https://en.wikipedia.org/wiki/Triple_modular_redundancy
         | 
         | https://en.wikipedia.org/wiki/Single-event_upset
         | 
         | For manned spaceflight, NASA ups N from 3 to 5.
         | 
         | Other mitigations include completely disabling all CPU caches
         | (with a big performance hit), and continuously refreshing the
         | ECC RAM in background.
         | 
         | There are also a bunch of hardware mitigations to prevent
         | "latch up" of the digital circuits.
        
           | rkagerer wrote:
           | In redundant systems like these, how do you avoid the voting
           | circuit becoming a single point of failure?
           | 
           | Eg. I could understand if each subsystem had its own
           | actuators and they were designed so any 3 could
           | aerodynamically override the other 2, but I don't think
           | that's how it works in practice.
        
             | AlphaSite wrote:
             | Voting can be coordinated between the N cpus rather than an
             | external arbiter (even making that redundant eventually
             | required the CPUs to decide what to do if they disagree so
             | may as well handle it internally).
        
             | exe34 wrote:
             | if the issue is radiation bit flipping, you could make that
             | part overly shielded?
        
               | baq wrote:
               | Define 'overly'. You can submerge it in a sphere of
               | water, but that's going to be expensive to launch.
        
               | exe34 wrote:
               | I suspect a couple millimeters of lead in the right place
               | would do it. cheaper to shield the voting mechanism than
               | the whole thing.
        
             | jasonwatkinspdx wrote:
             | My understanding is you're roughly right: the actuators
             | will have their own microcontroller. It receives commands
             | from the say 3 flight computers, then decides locally how
             | respond if they mismatch. Ie for 2 out of 3 matching it may
             | continue as commanded, but with only 1 out of 3 it may
             | shift into a fail safe strategy for whatever that actuator
             | is doing.
        
             | V__ wrote:
             | Can't this be solved by having a "high refresh-rate"? Even
             | if the voting circuit gets hit, if it updates 60 times a
             | second it won't really affect any mechanical parts since
             | the next signal will quickly override the error?
        
             | simne wrote:
             | > how do you avoid the voting circuit becoming a single
             | point of failure
             | 
             | They do not. Just make voting circuit much more reliable
             | than computing blocks.
             | 
             | As example, computing block could be CMOS, but voting
             | circuit made from discrete components, which are just too
             | large to be sensitive to particles.
             | 
             | Unfortunately, discrete components are sensitive to overall
             | exposure (more than nm scale transistors), because large
             | square gather more events and suffered by diffusion.
             | 
             | Other example from aviation world - many planes still have
             | mechanic connection of steering wheel to control surfaces,
             | because mechanic connection considered ideally reliable.
             | Unfortunately, at least one catastrophe happen because one
             | pilot blocked his wheel and other cannot overcome this
             | block.
             | 
             | BTW weird fact, modern planes don't have rod physically
             | connected to engine, because engine have it's own computer,
             | which emulate behavior of old piston carburetor, and on
             | Boeing emulating stick have electronic actuator, so it
             | automatically placed in position, corresponding to actual
             | engine mode, but Airbus don't have such actuator.
             | 
             | I want to say - especially big planes (and planes overall),
             | are weird mix of very conservative inherited mechanisms and
             | new technologies.
        
               | anonymousiam wrote:
               | Electronics in high-radiation environments benefit from a
               | large feature size with regard to SEU reduction, but
               | you're correct that the larger parts degrade faster in
               | such environments, so they've created "rad-hard"
               | components to mitigate that issue.
               | 
               | https://en.wikipedia.org/wiki/Radiation_hardening
               | 
               | It's interesting to me that triple-voting wasn't as
               | necessary on the older (rad-hard) processors. Every
               | foundry in the world is steering toward CPUs with smaller
               | and smaller feature sizes, because they are faster and
               | consume less power, but the (very small) market for
               | space-based processors wants large feature sizes. Because
               | those aren't available anymore, TMR is the work-around.
               | 
               | https://en.wikipedia.org/wiki/IBM_RAD6000
               | 
               | https://en.wikipedia.org/wiki/RAD750
               | 
               | Most modern space processing systems use a combination of
               | rad-hard CPUs and TMR.
        
             | cpgxiii wrote:
             | In some cases, it is exactly the case of multiple
             | independent actuators, such that the "voting" is
             | effectively performed by the physical mechanism of the
             | control surface.
             | 
             | In other cases all of the subsystems implement the
             | comparison logic and "vote themselves out" if their outputs
             | diverge from the others. A lot of aircraft control systems
             | are structured more as primary/secondary/backup where there
             | is a defined order of reversion in case of disagreement,
             | rather than voting between equals.
             | 
             | But, more generally, it is very hard to eliminate all
             | possible single points of failure in complex control
             | systems, and there are many cases of previously unknown
             | failure points appearing years or decades into service. Any
             | sort of multi-drop shared data bus is very vulnerable to
             | common failures, and this is a big part of the switch to
             | ethernet-derived switched avionics systems (e.g. Afdx) from
             | older multi-drop serial busses.
        
           | aborsy wrote:
           | TMR and co are basically repetition codes, simplest
           | performant least efficient ECC.
        
         | RealityVoid wrote:
         | See my other comments in the other threads. This does not have
         | EDAC. I was as surprised as you but it doesn't seems to be an
         | MCU but a composition of several distinct chips. That flight
         | computer was designed in the 90's and updated in 2002 with a
         | new hw variant that does have edac. So yes, for this kind of
         | thing, I can buy that a bit flip happened.
         | 
         | You can see much more data in the report:
         | 
         | https://www.atsb.gov.au/sites/default/files/media/3532398/ao...
        
           | Reason077 wrote:
           | The recalled aircraft include the latest A320neo model, some
           | of which are basically brand new. Why would they be using
           | flight computers from before 2002? Why is an old report from
           | 2008, relating to a completely different aircraft type
           | (A330), relevant to the A320 issue today?
        
             | RealityVoid wrote:
             | Because the problem isn't just this. It's that the flight
             | controller did not properly decide what to do when the data
             | spiked because of this issue as well.
        
             | Havoc wrote:
             | > Why would they be using flight computers from before
             | 2002?
             | 
             | Guessing that using previously certified stuff is an
             | advantage
        
             | LiamPowell wrote:
             | > Why would they be using flight computers from before
             | 2002?
             | 
             | Why would you assume they're not? I don't know about
             | aircraft specifically, but there's plenty of hardware that
             | uses components older than that. Microchip still makes 8051
             | clones 45 years after the 8051 was released.
        
               | K0balt wrote:
               | That's just wild to think about. We should all strive to
               | build solutions that plague our descendants with their
               | persistent utility.
        
               | hylaride wrote:
               | From a pure safety point of view, it's easier to deal
               | with older, but well-understood products, only updating
               | them if it's an actual safety issue. The alternative is
               | having to deal with many generations of tech, as well as
               | permutations with other components, that could get
               | infinitely complicated. On top of that, it's extremely
               | time consuming and expensive to certify new components.
               | 
               | There's a reason the airlines and manufacturers hem and
               | haw about new models until the economics overwhelmingly
               | make it worthwhile, and even then it can still be a
               | shitshow. The MCAS issue is case in point of how
               | introducing new tech can cause unexpected issues (made
               | worse by Boeing's internal culture).
               | 
               | The 787 dreamliner is also a good example of how hard it
               | is. By all accounts is a success, but it had some serious
               | teething problems and still has some concerns about the
               | long term wear and tear of the composite materials
               | (though a lot of it's problems wasn't necessarily the
               | application of new tech, but Boeing's simultaneous desire
               | to overcomplicate the manufacturing pipeline via
               | outsourcing and spreading out manufacturing).
        
             | 4ndrewl wrote:
             | The neo is not brand new - it's an incremental update to
             | the 320. neo refers to New Engine Option
        
               | rkomorn wrote:
               | They wrote "some of which are basically brand new", which
               | is technically correct.
               | 
               | They didn't say the design was brand new.
        
             | t0mas88 wrote:
             | > Why would they be using flight computers from before
             | 2002?
             | 
             | Because getting a new one certified is extremely expensive.
             | And designing an aircraft with a new type certificate is
             | unpopular with the airlines. Since pilots are locked into a
             | single type at a time, a mixed fleet is less efficient.
             | 
             | Having a pilot switch type is very expensive, in the
             | 50-100k per pilot range. And it comes with operational
             | restrictions, you can't pair a newly trained (on type)
             | captain with a newly trained first officer, so you need to
             | manage all of this.
        
               | Reason077 wrote:
               | I think you're confusing a type _certificate_ (certifying
               | the airworthiness of the aircraft type) with a type
               | _rating_ , which certifies the pilot is qualified to
               | operate that type.
               | 
               | Significant internal hardware changes might indeed
               | require re-certification, but it generally wouldn't mean
               | that pilots need to re-qualify or get a new type rating.
        
               | t0mas88 wrote:
               | No I meant designing a new aircraft with a new type
               | certificate instead of creating the A320neo generation on
               | the same type certificate. The parent comment wondered
               | why Airbus would keep the old computers around, I tried
               | to explain why they keep a lot of things the same and
               | only incrementally add variants. Adding a variant allows
               | them to be flown with the same type rating or with only
               | differences training (that's what EASA calls it, not sure
               | about the US term) which is much less costly.
        
               | darkwater wrote:
               | Asking from ignorance: shouldn't the computer design be
               | an implementation detail to the captain, while the
               | interface used by who pilots stays the same for that type
               | of airplane? I understand physical changes in the design
               | need a retraining but the computer?
        
               | t0mas88 wrote:
               | Ideally you would not change the computer at all so your
               | type certificate doesn't change. If you have to (or for
               | commercial reasons really want to) make a change you
               | would try very hard to keep that the same type
               | certificate or at most a variant of the same type
               | certificate. If you can do that then it will be flown
               | with the same type rating and you avoid all the crew
               | training cost issues.
               | 
               | But to do that you'll still have to prove that the
               | changes don't change any of the aircraft characteristics.
               | And that's not just the normal handling but also any
               | failure modes. Which is an expensive thing to do, so
               | Airbus would normally not do this unless there is a
               | strong reason to do it.
               | 
               | The crew is also trained on a lot of knowledge about the
               | systems behind the interface, so they can figure out what
               | might be wrong in case of problems. That doesn't include
               | the software architecture itself but it does include a
               | lot of information on how redundancy between the systems
               | work and what happens in case one system output is
               | invalid. For example how the fail over logic works in
               | case of a flight control computer failure, or how it
               | responds to loosing certain inputs. And how that affects
               | automation capabilities, like: no autoland when X fails,
               | no autopilot and degradation to alternate contol law when
               | Y fails, further degradation if X and Z fail at the same
               | time. Sometimes also per "side", not all computers are
               | connected to all sensors.
               | 
               | The computer change can't change any of that without
               | requiring retraining.
        
               | mlyle wrote:
               | 1. I don't think adding robustness necessarily requires
               | changing how systems are presented to the flight crew.
               | 
               | 2. Bigger changes than this are made _all the time_ under
               | the same type certificate. Many planes went from steam
               | gauges to glass cockpits. A320 added a new fuel tank with
               | transfer valves and transfer logic and new failure modes,
               | and has completely changed control law over the type.
               | etc.
        
               | RealityVoid wrote:
               | Since the new versions of the same ADIRU have EDAC, they
               | have been using it on planes since 2002 and they have
               | been putting the EDAC variant in whenever an old one was
               | being returned for repairs, I don't think this is the
               | reason. I think the reason is that they had 3 ADIRU's and
               | even if one got wonky, the algorithm on the ELAC flight
               | computer would have to take the correct decision. It did
               | not take the correct decision. The ELAC is the one being
               | updated in this case.
        
             | RealityVoid wrote:
             | The issue detailed in the linked report details why the
             | spike happened in the first place on the ADIRU (produced by
             | Northrop Gruman). The recalled controller is the ELAC that
             | comes from Thales. The problem chain was that despite the
             | ADIRU spiking up, the ELAC should not have taken the
             | reactions it took. So they are fixing it in the ELAC.
        
           | lxgr wrote:
           | > This does not have EDAC. I was as surprised as you but it
           | doesn't seems to be an MCU but a composition of several
           | distinct chips.
           | 
           | Wasn't the philosophy back then to run multiple independent
           | (and often even designed and manufactured by different teams)
           | computers and run a quorum algorithm at a very high level?
           | 
           | Maybe ECC was seen as redundant in that model?
        
             | JorgeGT wrote:
             | I don't know about the A320 but this was certainly the
             | model for the Eurofighter. One of my university professors
             | was in one of the teams, they were given the specs and not
             | allowed to communicate with the other teams in any way
             | during the hw and sw development.
        
               | RealityVoid wrote:
               | > they were given the specs and not allowed to
               | communicate with the other teams in any way during the hw
               | and sw development.
               | 
               | Jeez, it would drive me _up the wall_. Let's say I could
               | somewhat justify the security concerns, but this seems
               | like it severely hampers the ability to design the
               | system. And it seems like a safety concern.
        
               | K0balt wrote:
               | The idea was to build three completely different systems
               | to produce the same data, so that an error or problem in
               | one could not be reasonably replicated in the others. In
               | a case such as this, even ideas about algorithms could
               | result in undesirable similarities that could end up
               | propagating an attack surface, a logic error, or a
               | hardware weakness or vulnerability. The desired result is
               | that the teas solve the problem separately using distinct
               | approaches and resources.
        
               | Filligree wrote:
               | And did they?
               | 
               | Sometimes the solution is obvious, such that if you ask
               | three engineers to solve it you'll get three copies of
               | the same solution, whereas that might not happen if
               | they're able to communicate.
               | 
               | I'm sure they knew what they were doing, but I wonder how
               | they avoided that scenario.
        
               | cmckn wrote:
               | Even with the same approach, I imagine the implementation
               | could differ enough to still meet the goal. But I'm also
               | curious if the differences were actually quantified after
               | the fact, it seems an important step.
        
               | addaon wrote:
               | I can (and have in past) written a long explanation on my
               | experience with this, but...
               | 
               | Redundancy is a tool for reducing the probability of
               | encountering statistical errors, which come from things
               | like SEUs.
               | 
               | Dissimilarity is a tool for reducing the "probability" of
               | encountering non-statistical errors -- aka defects, bugs
               | -- but it's a bit of a category error to discuss the
               | probability of a non-probabilistic event; either the bug
               | exists or it does not, at best you can talk about the
               | state coverage that corresponds to its observability, but
               | we don't sample state space uniformly.
               | 
               | There has been a trend in the past few decades, somewhat
               | informed by NASA studies, to favor redundancy as the
               | (only, effective) tool for mitigating statistical errors,
               | but to lean against heavy use of dissimilarity for
               | software development in particular. This is because of a
               | belief that (a) independent software teams implement the
               | same bugs anyway and (b) an hour spent on duplication is
               | better spent on testing. But at the absolute highest
               | level of safety, where development hours are a relatively
               | low cost compared to verification hours, I know it's
               | still used; and I don't know how the hardware folks'
               | philosophy has evolved.
        
               | sandworm101 wrote:
               | Not at airbus. Ask a german, french and british engineer
               | the same question and you will _never, ever_ get the same
               | answer from each.
        
               | lambdaone wrote:
               | What you are trying to minimize here is the error rate of
               | the composite system, not the error rate of the
               | individual modules. You take it as a given that all the
               | teams are doing their human best to eliminate mistakes
               | from their design. The idea of this is to make it likely
               | that the mistakes that remain are _different_ mistakes
               | from those made by the other teams.
               | 
               |  _Providing errors are independent_ , it's better to have
               | three subsystems with 99% reliability in a voting
               | arrangement than one system with 99.9% reliability.
        
               | saltcured wrote:
               | This seems like it would need some referees who watch
               | over the teams and intrude with, "no, that method is
               | already claimed by the other team, do something else"!
               | 
               | Otherwise, I can easily see teams doing parallel
               | construction of the same techniques. So many developments
               | seem to happen like this, due to everyone being primed by
               | the same socio-technical environment...
        
               | lxgr wrote:
               | How so? It's a safety measure at least as much as a
               | security one.
               | 
               | It's essentially a very intentional trade-off between
               | groupthink and the wisdom of crowds, but it lands on a
               | very different point on that scale than most other
               | systems.
               | 
               | Arguably the track record of Airbus's fly-by-wire does
               | them some justice for that decision.
        
             | RealityVoid wrote:
             | > Wasn't the philosophy back then to run multiple
             | independent (and often even designed and manufactured by
             | different teams) computers and run a quorum algorithm at a
             | very high level?
             | 
             | It was, and they did (well, same design, but they were
             | independent). I quote from the report:
             | 
             | "To provide redundancy, the ADIRS included three air data
             | inertial reference units (ADIRU 1, ADIRU 2, and ADIRU 3).
             | Each was of the same design, provided the same information,
             | and operated independently of the other two"
             | 
             | > Maybe ECC was seen as redundant in that model?
             | 
             | I personally would not eschew any level of redundancy when
             | it can improve safety, even in remote cases. It seems at
             | the moment of the module's creation, EDAC was not required,
             | and it probably was quite more expensive. The new variant
             | apparently has EDAC. They retrofitted all units with the
             | newer variants whenever one broke down. Overall, ECC is an
             | extra layer of protection. The _presumably_ bit flip would
             | be plausible to blame for data spikes. But even so, the
             | data spikes should not have caused the controls issue. The
             | controls issue is a separate problem, and it's highly
             | likely THAT is what they are going to address, in another
             | compute unit.
             | 
             | "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]"
             | 
             | This is most likely what they will address. The other
             | reports confirm that the fix will be in the ELAC produced
             | by Thales and the issue with the spikes detailed in the
             | report was in an ADIRU module produced by Northrop Gruman.
        
           | Liftyee wrote:
           | What does EDAC mean here? I wasn't able to find a definition.
           | My guess is "error detection and correction"?
           | 
           | Difference between it and ECC?
        
             | RealityVoid wrote:
             | That was my initial confusion as well. It means exactly
             | what you guessed, "Error detection and correction". The
             | term is also spelled out in the report. I asked Claude
             | about it (caveat emptor) and it said EDAC is the correct
             | name for the circuitry and implementation itself whereas
             | ECC is the algorithm. Gemini said that EDAC is the general
             | technique and ECC is one implementation variant. So, at
             | this point, I'm not sure. They are used interchangeably
             | (maybe wrongly so), and in this case, we're referring to,
             | essentially, the same thing, with maybe some small
             | differences in the details. In my professional life, almost
             | always I referred to ECC. In the report, they were only
             | using EDAC. I thought I'd maintain consistency with the
             | report so I tried using EDAC as well.
        
               | Yokolos wrote:
               | EDAC is a general term for an error detection and
               | correction system. It can encompass ECC memory or other
               | solutions.
               | 
               | https://www.sciencedirect.com/science/article/abs/pii/S01
               | 419...
        
               | Normal_gaussian wrote:
               | Large portions of this comment provides zero to negative
               | value. You've quoted two LLMs and couched it in "caveat
               | emptor" and "so I'm not sure". The rest of your comment
               | has then mused over this data you do not trust using
               | generalities ("my profession" are you a JS S/W eng? A
               | chip design specialist at ARM? A security researcher?).
               | 
               | All of the value of your comment comes from the first
               | sentence and the last two.
        
               | RealityVoid wrote:
               | Sheesh, tough crowd.
        
               | ImPostingOnHN wrote:
               | Feel free to consult LLMs, with all their downsides (like
               | _you_ needing to verify what they say, because it could
               | be totally wrong).
               | 
               | What you're doing here is half the job: consulting an LLM
               | and sharing the output without verifying whether it is
               | true. You're then saying _' okay everyone else, finish my
               | job for me, specifically the hard part of it (the
               | verification), while I did the easy part (asking a magic
               | 8 ball)'_.
               | 
               | From this perspective, your comment could be viewed as
               | disrespectful of others by asking them to finish _your_
               | job, and of negative value because it could be totally
               | hallucinated and false, and you didn 't care enough about
               | others to find out before posting it.
               | 
               | tl;dr: _' I asked an LLM and it said X'_ will likely, for
               | the near future, be downvoted just like _' I flipped a
               | coin and it said X'_. You should be pretty confident that
               | what you post is not false before posting it, regardless
               | of how you came up with it.
        
               | dgacmu wrote:
               | The more correct and general answer is that:
               | 
               | - EDAC is a term that encompasses anything used to detect
               | and correct errors. While this almost always involves
               | redundancy of some sort, _how_ it is done is unspecified.
               | 
               | - The term ECC used stand-alone refers specifically to
               | adding redundancy to data in the form of an error
               | correcting code. But it is not a single algorithm - there
               | are many ECC / FEC codes, from hamming codes used on
               | small chunks of data such as data stored in RAM, to block
               | codes like reed-solomon more commonly used on file
               | storage data.
               | 
               | - The term ECC memory could really just mean "EDAC"
               | memory, but in practice, error correcting codes are _the_
               | way you'd do this from a cost perspective, so it works
               | out. I don't think most systems would do triple
               | redundancy on just the RAM -- at that point you'd run an
               | independent microcontroller with the RAM to get higher-
               | level TMR.
        
             | K0balt wrote:
             | EDAC is the concept, ECC is a family of algorithmic
             | solutions in the service of the concept. Specific
             | implementations of ECC are the engineering solution that
             | implement the specific form of ECC in specific devices at
             | the hardware or software level.
             | 
             | It's confusing because EDAC and ECC seem to mean the same
             | thing, but ECC is a term primarily used in memory
             | integrity, where EDAC is a system level concept.
        
       | qaq wrote:
       | Has BoFesc vibes "It's friday, so I get into work early, before
       | lunch even. The phone rings. Shit!
       | 
       | I turn the page on the excuse sheet. "SOLAR FLARES" stares out at
       | me. I'd better read up on that..."
        
         | suprjami wrote:
         | Solar Flares was always my favourite result on the BoFH Excuse
         | Generator.
         | 
         | http://jefflane.org/bofh/bofh.pl
        
         | ezconnect wrote:
         | Solar flares are the best excuse. We just have to wait it out.
        
       | owenthejumper wrote:
       | A friend works at Jetblue. They are scrambling hard to do the
       | updates.
        
       | viiralvx wrote:
       | I was traveling during this entire ordeal. My flight got delayed
       | by 7 hours. Insane day, just now boarding my flight. American
       | Airlines was in shambles today.
        
       | jfoster wrote:
       | I've noticed that some carriers seem to be suggesting that there
       | might be no impact to flights, but isn't this an immediate
       | grounding for each aircraft until the update is made?
       | 
       | How is it possible that this wouldn't impact upon flight
       | schedules?
        
         | arrel wrote:
         | N of 1, but I'm stuck in phoenix overnight because our flight
         | was delayed an hour and a half by airbus maintenance and we
         | missed our connection.
        
         | icegreentea2 wrote:
         | The grounding is for 6000 of 11000 A320 series. I believe it's
         | some combination of software and hardware configuration that is
         | at risk.
        
           | jfoster wrote:
           | Thank you; that makes sense. I had the impression it was the
           | entire fleet.
        
             | julik wrote:
             | It depends on whether the ELAC is an LRU (line-replaceable
             | unit, i.e. a box with ports that can be swapped at an
             | airport) and whether a software update can be uploaded into
             | a unit that is installed (not all aircraft have a "firmware
             | update via cable or floppy", so to speak)
        
         | simne wrote:
         | If possible for exact this plane, could make software update
         | just as routine procedure.
         | 
         | But as I hear, air transporters could buy planes in different
         | configurations, so for example, Emirates airlines, or Lufthansa
         | always buy planes with all features included, but small Asian
         | airlines could buy limited configuration (even without some
         | safety indicators).
         | 
         | So for Emirates or Lufthansa, will need one empty flight to
         | home airport, but for small airline will need to flight to some
         | large maintenance base (or to factory base) and wait in queue
         | there (you could find in internet images of Boeing factory base
         | with lot of grounded 737-MAXes few years ago).
         | 
         | So for Emirates or Lufthansa will be minimal impact to flights
         | (just like replacement of bus), but for small airlines things
         | could be much worse.
        
       | kappi wrote:
       | Following the Airbus A320 emergency airworthiness action,
       | everyone will be talking about the ELAC (Elevator Aileron
       | Computer) manufactured by Thales, which caused a sudden pitch-
       | down without pilot input on JetBlue 1230 back in October.
       | 
       | So here's everything you need to know about ELAC.
       | 
       | The ELAC System in the Airbus A320: The Brains Behind Pitch and
       | Roll Control
       | https://x.com/Turbinetraveler/status/1994498724513345637
        
         | ThePowerOfFuet wrote:
         | https://xcancel.com/Turbinetraveler/status/19944987245133456...
        
       | minitoar wrote:
       | We flew too close to the sun
        
       | joelthelion wrote:
       | Do they really need to ground the entire fleet for that? One
       | incident for ten thousand planes in the air for years. I'd think
       | that giving airlines two months to fix it would be sufficient.
        
         | mrpippy wrote:
         | I don't believe it's been years, only the latest firmware
         | version for the ELAC is affected. The fix is to downgrade (or
         | replace hardware with a unit running earlier firmware)
        
         | kijin wrote:
         | I imagine it could help with Airbus marketing.
         | 
         | "We take proactive measures, whereas our competitor only takes
         | action after multiple fatal crashes!"
        
           | brabel wrote:
           | Imagine an airplane crashed in these 2 months. I bet you
           | would join the chorus and blame them for gross negligence.
        
             | kijin wrote:
             | There's a huge difference between "manufacturer recommended
             | updates, but airline waited until the last week to apply
             | them" and "manufacturer didn't even acknowledge the issue"
             | in terms of who the chorus is going to blame.
        
           | probably_wrong wrote:
           | I know someone who is stranded in another continent thanks to
           | this. Trust me, all the understanding I could have as a
           | technical user has been offset by the MASSIVE pain in the ass
           | that is rebooking an international flight. And non-technical
           | users have heard "the plane will not travel because it
           | requires a software update", which does not inspire
           | confidence.
           | 
           | As far as I'm concerned it has not helped with their
           | marketing.
        
         | Bud wrote:
         | From their viewpoint, you have to think about what happens if,
         | after they became aware of this vulnerability, there was then a
         | crash because they weren't prompt and aggressive enough in
         | addressing it. That's the kind of thing that ruins your entire
         | company forever.
        
           | Esophagus4 wrote:
           | Yep - Boeing is still dealing with it years later.
           | 
           | (As they should - I'm still very mad at them.)
        
         | jfoster wrote:
         | I wonder who eats the cost of this? I presume it's the
         | airlines.
         | 
         | So the immediate cost to Airbus of grounding the fleet is quite
         | low, whilst the downside of not grounding the fleet (risk of
         | incident, lawsuits, reputation, etc.) could be substantial.
        
           | Havoc wrote:
           | Yeah should be airlines
           | 
           | It sounds like the fix is fairly quick so probably not as
           | expensive as the max multi month groundings
           | 
           | I doubt anyone is going to sue. Repairs etc are a part of
           | life when owning aircraft. So as long as Airbus makes this
           | happen fast and smooth they're probably ok
        
         | f1shy wrote:
         | I would personally not want to seat in those planes in those 2
         | months.
        
           | upcoming-sesame wrote:
           | nothing worse than rushing a fix in production - only to find
           | out the fix has caused more damage than the original bug
        
         | miyuru wrote:
         | this is Airbus, not Boeing
        
         | pyb wrote:
         | I get the feeling that they are doing this partly for marketing
         | purposes.
        
         | refulgentis wrote:
         | Yeah, because the alternative is knowing you might kill people
         | due to a mundane engineering known issue.
        
       | 65a wrote:
       | There's a great postmortem here about what might have been a
       | similar SEU (single event upset--bitflip) here:
       | https://www.atsb.gov.au/sites/default/files/media/3532398/ao...
        
       | pyb wrote:
       | The aerospace industry has had countermeasures in place against
       | bit-flips for a long time, oftentimes thanks to redudancy
       | 
       | Airbus/Thales's fix in this case appears to add more error
       | checking, and to restart the misbehaving component.
       | https://bea.aero/fileadmin/user_upload/BEA2024-0404-BEA2025-...
       | 
       | ("une supervision interne du composant a l'origine de la
       | defaillance ; - un mecanisme de redemarrage automatique de ce
       | composant des lors que la defaillance est detectee)
        
         | nolist_policy wrote:
         | The linked document is not related to this incident.
        
       | raverbashing wrote:
       | Apparently the fix is reverting to a previous version of the SW
       | (see https://avherald.com/h?article=52f1ffc3&opt=0 )
       | 
       | Curious what a sw change might have done in terms of resiliency.
       | Maybe an incorrect memory setting or some code path that is not
       | calculating things redundantly maybe?
        
         | rootusrootus wrote:
         | So it's not just Boeing that can screw up software on an
         | airplane. I guess now I have to be a little afraid of _all_ the
         | airliners.
        
       | rene_d wrote:
       | The Aviation Herald has more technical details:
       | 
       | https://avherald.com/h?article=52f1ffc3&opt=0
        
         | loxodrome wrote:
         | Thanks for the link. This line in particular is concerning.
         | 
         | "This identified vulnerability could lead in the worst case
         | scenario to an uncommanded elevator movement that may result in
         | exceeding the aircraft structural capability."
        
           | isodev wrote:
           | Well, I think in the grand scheme of things (including on the
           | ground), the range of safety faults that can be triggered by
           | a simple bitflip at the wrong moment range from inconvenient
           | to absolute disaster. So in that sense, I'm very happy that
           | Airbus has managed to identify opportunities to improve their
           | design to be even more resilient.
        
       | nickdothutton wrote:
       | I'd just like to point out that if you are in the computing
       | industry long enough, you will get to see a few such incidents
       | under different circumstances, not only in industries like
       | aerospace. Mostly things like ECC save your a*, sometimes your
       | software will be able to recognise a temporary spurious reading
       | and disregard it because you had enough alternative checking
       | logic, or in the case of realtime and safety critical maybe even
       | your systems can take a vote between them. Got caught out by (cpu
       | cache line) bit flips in the 90s, months of pain trying to track
       | it down. Some of your will know :-)
        
         | LadyCailin wrote:
         | We noticed this in our logs once! We service a huge amount of
         | traffic, and as part of that, we log what is effectively an
         | enum. We did a summarization of this field once, and noticed
         | that there were a couple of "impossible" values being logged.
         | One of my coworkers realized that the string that actually got
         | logged was exactly one bit off from a valid string, and we came
         | to the conclusion that we were probably seeing cosmic rays in
         | action, either in our service, or in the logging service.
        
           | tuetuopay wrote:
           | I had a similar story on my NAS that got one btrfs path
           | corrupt. Plopped in on the btrfs IRC, one of the devs noticed
           | the inconsistency was one bitflip away from the right value.
           | Incredibly they were able to give me the right commands to
           | fix it! Got to give credit where it is due, btrfs took the
           | safe path and refused to touch the affected directory until
           | fixed, and has enough tooling to fix this.
           | 
           | I won't blame cosmic rays but more likely dying RAM. The NAS
           | now runs ECC memory.
        
           | Philip-J-Fry wrote:
           | I also saw a similar thing. I also naively pointed at "cosmic
           | rays". It wasn't until someone found the actual bug that I
           | realised how unlikely that was.
           | 
           | The actual bug was unsafe code somewhere else in the
           | application corrupting the memory. The application worked
           | fine, but the log message strings were being slightly
           | corrupted. Just a random letter here and there being
           | something it shouldn't be.
           | 
           | The question really should have been, if this was truly
           | cosmic interference, why only this service and why was the
           | problem appearing more than once over multiple versions of
           | the application?
           | 
           | Cosmic rays are a great excuse to problems you don't yet
           | understand. But the reality of them is extremely rare and
           | it's like 99% a memory corruption bug caused by application
           | code.
        
         | Theodores wrote:
         | Is that you, Julian?
         | 
         | I jest, but, once upon a time I worked with an infallible
         | developer. When my projects crashed and burned, I would assume
         | that it was my lack of competence and take that as my starting
         | point. However, my colleague would assume that it was a stray
         | neutrino that had flipped a bit to trigger the failure, even if
         | it was a reproducible error.
         | 
         | He would then work backwards from 93 million miles away to
         | blame the client, blame the linux kernel, blame the device
         | drivers and finally, once all of that and the 'three letter
         | agencies' were eliminated, perhaps consider the problem was
         | between his keyboard and his chair.
         | 
         | In all fairness, he was a genius, and, regarding the A320
         | situation, he would have been spot on!
        
       | supernova87a wrote:
       | I wonder how the incident was diagnosed? Does the FDR record low
       | level errors that might've contributed to this? I thought that it
       | only recorded certain input parameters and high-level flight
       | metrics but I'm no expert.
       | 
       | If a radiation event caused some bit-flip, how would you realize
       | that's what triggered an error? Or maybe the FDR does record when
       | certain things go wrong? I'm thinking like, voting errors of the
       | main flight computers?
       | 
       | Anyway, would be very interested to know!
        
         | yread wrote:
         | From a comment on avherald:
         | 
         | "Had the same problem with low power CMOS 3 transistor memory
         | cells used in implantable defibrillators in the 1990s. Needed
         | software detection and correction upgrade for implanted
         | devices, and radiation hardening for new devices. Issue was
         | confirmed to be caused by solar radiation by flying devices
         | between Sydney and Buenos Aires over the south pole multiple
         | times, accumulating a statistically significant different error
         | rate to control sample in Sydney."
        
       | jakub_g wrote:
       | From newspaper reporting on this, they are rolling back a
       | software update. I wonder what was the original cause or the
       | update? How often are flight computers software updated and why?
        
         | julik wrote:
         | This ELAC version is 100-something, and the A320 first flew
         | around 1988. Why the updates - for example, there are updates
         | to flight control law transitions, like after 1991 where the
         | aircraft would limit flight control inputs during landing,
         | thinking it would be preventing a stall - because it would not
         | go into the flare law appropriately. See
         | https://en.wikipedia.org/wiki/Iberia_Flight_1456
         | 
         | The cause could have also been an extra check introduced in one
         | of the routines - which backfired in this particular failure
         | scenario.
        
       | 1970-01-01 wrote:
       | They said the same thing at Toyota when the unintended accel
       | problem was in the news, but never found a real world example.
       | There are a lot more old Toyotas still on the road than Airbuses
       | in the air, so distance to the sun makes all the difference here?
       | I wonder if they only see issues when flying near the north pole?
        
       | nubinetwork wrote:
       | Why would a CME disrupt a single brand and model of aircraft,
       | when the entire planet is covered in computers that almost never
       | have bitflip issues when a CME rolls through every few months?
        
         | 1970-01-01 wrote:
         | I'm guessing EM shielding flaw or something electronic. See my
         | comment on the Toyotas. It doesn't make sense from a raw
         | probability perspective.
        
         | squarefoot wrote:
         | I would guess barely enough cable shielding paired with long
         | enough paths along the aircraft so that the signals there would
         | be more likely affected by EM induced currents.
        
       | jpollock wrote:
       | The design of the system is very interesting, particularly how it
       | expects to handle errors.
       | 
       | In 90's Telco, you used to have a pair of systems and if they
       | disagreed, they would decide which side was bad and disable it.
       | 
       | In modern cloud, you accept there are errors. There's another
       | request in ~10+ms. You only look when the error rate becomes
       | commercially important.
       | 
       | My understanding of spacecraft is that there would be 3
       | independent implementations and they would vote.
       | 
       | The plane has a matrix of sensors and systems, allowing faults to
       | be bubbled up and bad elements disabled independently.
       | 
       | The ADIRU does compare values to detect failures (median of 3
       | sensors), but they could only detect errors that last >1s. The
       | flight computer used the raw data - because the sensors aren't
       | interchangeable (they won't have consistent readings in all
       | flight modes)!
       | 
       | Very nifty.
       | 
       | One thing, they say "memorisation period", I don't think it's a
       | memorisation period? From my reading of the algorithm, it should
       | be more "last value retention period"? Or "sensor spurious fault
       | reading delay"?
       | 
       | Section 2.1 A330/A340 flight control system design "AOA
       | computation logic"
       | 
       | https://www.atsb.gov.au/sites/default/files/media/3532398/ao...
        
         | jpollock wrote:
         | For example....
         | 
         | "Preliminary A330/A340 FCPC algorithm"
         | 
         | "The algorithm did not effectively manage a specific situation
         | where AOA 2 and AOA 3 on one side of the aircraft were
         | temporarily incorrect and AOA 1 on the other side of the
         | aircraft was correct, resulting in ADR 1 being rejected."
         | 
         | So, you've got a system where _two_ of the three sensors are
         | bad, and you need to deal with it.
        
           | Loudergood wrote:
           | I'm in awe of the fact that two sensors can be wrong AND
           | agree with each other.
        
             | Nextgrid wrote:
             | Those being analog sensors measuring analog, physical
             | things, they will _never_ exactly agree with each other; so
             | there 's a plausibility window. As long as the fault causes
             | the sensors to remain within said window they will be
             | considered as valid.
        
             | UltraSane wrote:
             | It is just like having range of values considered to be
             | equal for floating point numbers.
        
         | rubatuga wrote:
         | Space computers are generally in 3 with a hot spare
        
           | sllabres wrote:
           | Space shuttle had five.
           | 
           | Four of them operating in a redundant set and the fifth
           | performing non critical task, as descripted in [1]. The fifth
           | is also programmed by a different contractor in a different
           | programming language: #1-4 running the Primary Avionics
           | Software System (PASS) programmed by IBM in HAL/S and #5
           | programmed by a different team of Rockwell International in
           | assembly. [2]
           | 
           | [1] https://people.cs.rutgers.edu/~uli/cs673/papers/Redundanc
           | yMa...
           | 
           | [2] https://ntrs.nasa.gov/api/citations/20110014946/downloads
           | /20...
        
       | rishabhaiover wrote:
       | I hope Airbus only uses Honeywell or Collins in their newer
       | planes.
        
       | skx001 wrote:
       | This video shows the the A320 computer and how the computer
       | cooling system works
       | 
       | https://www.youtube.com/watch?v=HQuc_HhW6VA
        
       | oofbey wrote:
       | This is in response to JetBlue flight 1230 from Cancun to Newark
       | on October 30, 2025, where a cosmic ray of some kind flipped a
       | bit and caused a dangerous situation. At the time there was a
       | minor (G1) geomagnetic storm - meaning more cosmic rays than
       | normal. The Planetary K-index was at 5. These are somewhat
       | elevated numbers - enough to produce a visible Aurora in Canada,
       | but probably not even the northernmost US. But also this level of
       | space weather is also very common. We hit G1 or higher about once
       | a week. That's the really damning part. If it had happened in a
       | G4 or G5 storm, then the engineers might have responded "we can't
       | fix everything", but this level of reliability is clearly
       | unacceptable.
        
       | rossjudson wrote:
       | My armchair guess is that they had a new control pathway not
       | properly participating in their integrity hand-off protocols,
       | doing some kind of transformation _outside_ of that protection.
       | 
       | I once saw some HW engineers go nuts trying to find out why a
       | storage device had an error rate several orders of magnitude
       | higher than the extremely low error rate they expected (and
       | triggering data corruption errors). It turns out to be one
       | extremely deep VHDL-based control area for an FPGA that didn't
       | properly do integrity. You'd have to flip a bit at an incredibly
       | precise point in time for error to occur, but that's what was
       | happening. When all the math was said and done, that FPGA control
       | path integrity miss _exactly_ accounted for the the higher error
       | rate.
        
       | albert_e wrote:
       | What if future aircraft had "OTA" updates to software... using
       | this as an example of avoidable downtime.
       | 
       | OTA updates to cars makes me feel uneasy -- not knowing what new
       | bugs it might introduce.
        
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