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Airbus A320 – intense solar radiation may corrupt data critical for flight

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Re: Airbus A320 – intense solar radiation may corrupt data critical for flight

#121

Post by simne »

rkagerer wrote: post #52
anonymousiam wrote: post #43

Earlier quoted context omitted.

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 refre…

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.

> 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.

Re: Airbus A320 – intense solar radiation may corrupt data critical for flight

#122

Post by dgacmu »

RealityVoid wrote: post #96
Liftyee wrote: post #93

Earlier quoted context omitted.

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?

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…

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.

Re: Airbus A320 – intense solar radiation may corrupt data critical for flight

#123

Post by foldr »

julik wrote: post #111
foldr wrote: post #82

Earlier quoted context omitted.

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 ve…

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.

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...

Re: Airbus A320 – intense solar radiation may corrupt data critical for flight

#124

Post by rainsford »

MaxfordAndSons wrote: post #24
lostlogin wrote: post #14

Earlier quoted context omitted.

> 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.

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…

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?

Re: Airbus A320 – intense solar radiation may corrupt data critical for flight

#125

Post by RealityVoid »

Normal_gaussian wrote: post #101
RealityVoid wrote: post #96

Earlier quoted context omitted.

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…

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.

Sheesh, tough crowd.

Re: Airbus A320 – intense solar radiation may corrupt data critical for flight

#126

Post by Filligree »

K0balt wrote: post #102
RealityVoid wrote: post #98

Earlier quoted context omitted.

> 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.

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…

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.

Re: Airbus A320 – intense solar radiation may corrupt data critical for flight

#127

Post by isodev »

loxodrome wrote: post #71
rene_d wrote: post #63

The Aviation Herald has more technical details: https://avherald.com/h?article=52f1ffc3&opt=0

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."

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.

Re: Airbus A320 – intense solar radiation may corrupt data critical for flight

#128

Post by tuetuopay »

LadyCailin wrote: post #78
nickdothutton wrote: post #76

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 criti…

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 c…

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.

Re: Airbus A320 – intense solar radiation may corrupt data critical for flight

#129

Post by RealityVoid »

t0mas88 wrote: post #70
Reason077 wrote: post #56

Earlier quoted context omitted.

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?

> 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…

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.

Re: Airbus A320 – intense solar radiation may corrupt data critical for flight

#130

Post by hughw »

russdill wrote: post #40
TehCorwiz wrote: post #16

Earlier quoted context omitted.

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

Completely unrelated and due to a design failure by the rpi folks.

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.
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