[JorgeGT]

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]

> 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.

[lambdaone]

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.

[K0balt]

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.

[lxgr]

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.