Like everything else, they were maintaining certification. The original avionics worked that way. The same reason that the LCD screens display simulations of the original avionics hardware such as the artificial horizon.
I suspect combined reliability of a simple switch and two independent systems is likely higher than one composite system and pilots or software trying to estimate and select which combinations of computers & sensors are "good" in the middle of an emergency.
And on the surface this looks like a reasonable comment, but it is exactly why there is a whole branch of engineering dedicated to understanding how to build safer systems. Counter-intuitive results abound.
So many issues - a simple switch usually has poor diagnostics, at least in one mode of failure, so you dont know it has failed until it is too late. A continuous measurement device connected to a computer/s will have a vast array of available diagnostics, 'most probably leading to less "dangerous undetected failures" than a simple switch, or combination of.
And "independent systems", sounds easy, but in practice full independence is almost impossible to achieve, and messy unpredictable humans dominate the common cause failures that overlap these systems.
There is more, much more, but this is why it is hard to right readable articles about these things, so much devil is in the detail that is hard to explain in bite sized portions.
nutjob2|6 years ago
digikata|6 years ago
airbreather|6 years ago
So many issues - a simple switch usually has poor diagnostics, at least in one mode of failure, so you dont know it has failed until it is too late. A continuous measurement device connected to a computer/s will have a vast array of available diagnostics, 'most probably leading to less "dangerous undetected failures" than a simple switch, or combination of.
And "independent systems", sounds easy, but in practice full independence is almost impossible to achieve, and messy unpredictable humans dominate the common cause failures that overlap these systems.
There is more, much more, but this is why it is hard to right readable articles about these things, so much devil is in the detail that is hard to explain in bite sized portions.