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danjayh | 6 years ago

For those who are outside of the industry, the article is probably not completely accurate. I don't know specifically about the 737 MAX, but for many of their other newer airframes (787, upcoming 777x), Boeing relies on a concept called 'high integrity at the source'. Essentially, two complete copies of the flight computer hardware are put on a single card and they cross-compare their results. If you're looking for a bit of dense reading material on the subject, you might find a related patent application interesting: https://patents.google.com/patent/US9170907

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makomk|6 years ago

As described, that provides zero protection against software bugs. Both of the redundant lanes are carrying out identical computations on identical data using identical code and will make identical errors if there's any bug. On paper it's more powerful than the non-synchronized system Airbus uses in that it can stop erroneous computations from being used at all, rather than detecting them after the fact, but it wouldn't be able to detect problems like the Qantas Flight 72 accident in which erroneous data with a particular timing happens to trip a latent bug.

calaphos|6 years ago

In Airbus case, who have been doing full fly by wire for a while now, there are at least two completly seperate software implementations which run in parallel and cross compare the result. They also run on redundant flight computers with different hardware architectures.

Boeing probably has a similar thing for the fly by wire fighter jets they are involved in but there passenger planes are still mainly directly controlled by the pilot.

Some material: https://www.researchgate.net/publication/26587285_Challenges... https://www.researchgate.net/publication/220845884_Approache...

CriticalCathed|6 years ago

What's the upside of two identical computers computing the same input?

I can understand a backup if the first fails, but why two identical systems contemporaneously computing?