a large chunk of it likely boils down to "digital signal processing would have been a top-of-the-line military capability in 1970 when the aircraft were designe

a large chunk of it likely boils down to "digital signal processing would have been a top-of-the-line military capability in 1970 when the aircraft were designed, and the onerous recertification process ensures that the cheapest outcome is always to just re-use the system and never mess with it". There's no incentive to mess with a working system, and a huge cost. do remember we're talking about commercial aircraft where software updates are still deployed on 3.5" floppies. it's difficult because obviously this is not a domain where "move fast and break things" is an option, I certainly see the benefits of a conservative engineering culture. But the 737 MAX situation already happened as a clever end-run around not being able to touch anything, and not being able to touch anything is more broadly killing general aviation (small aircraft). Extremely few aircraft have been certified since the 80s when the new regulations went into effect, it is very expensive and difficult. And at some point that boils down to encouraging "the wrong fix" or simply ignoring problems. these aircraft have defective radar altimeters, they are unable to function properly with a guard band over twice the size of the original design spec. The other problem here is regulatory capture - these aircraft shouldn't be in the air at all with a radar altimeter that is so dangerously defective. The right fix isn't "just let aircraft manufacturers ignore certification requirements when it's convenient", it's to come up with a level of certification that promotes a culture of engineering safety, but basically the FAA is just letting boeing keep dangerous planes in the air because it would be a mess if they didn't.