Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

airbus.com

Post reply on HN
Print view View original

141–150 of 184 posts

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

#141

Post by hylaride »

K0balt wrote: post #107
LiamPowell wrote: post #62

Earlier quoted context omitted.

> 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.

That’s just wild to think about. We should all strive to build solutions that plague our descendants with their persistent utility.

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).

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

#142

Post by refulgentis »

joelthelion wrote: post #34

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.

Yeah, because the alternative is knowing you might kill people due to a mundane engineering known issue.

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

#143

Post by mlyle »

t0mas88 wrote: post #95
darkwater wrote: post #89

Earlier quoted context omitted.

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?

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…

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.

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

#144

Post by addaon »

Filligree wrote: post #126
K0balt wrote: post #102

Earlier quoted context omitted.

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.

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.

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

#145

Post by russdill »

hughw wrote: post #130
russdill wrote: post #40

Earlier quoted context omitted.

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.

No, because it's a completely different kind of radiation.

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

#146

Post by jpollock »

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...

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

#147

Post by sandworm101 »

Filligree wrote: post #126
K0balt wrote: post #102

Earlier quoted context omitted.

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.

Not at airbus. Ask a german, french and british engineer the same question and you will never, ever get the same answer from each.

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

#148

Post by jpollock »

jpollock wrote: post #146

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…

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.

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

#149

Post by rubatuga »

jpollock wrote: post #146

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…

Space computers are generally in 3 with a hot spare

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

#150

Post by hughw »

russdill wrote: post #145
hughw wrote: post #130

Earlier quoted context omitted.

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.

No, because it's a completely different kind of radiation.

Different band, sure. Same principle, right?
Post reply on HN