[ah88]

It's common practice to change procedures instead of certification.

I flew an airplane that was getting ready to be retired after it's been in service for ~30 years and we had a lot of emergency procedures and memory items (items that pilots have to memorize) that were add over the years after various incidents.

The 737 MAX wasn't necessarily an unsafe airplane, it's pilots were not made aware of how everything worked, which led to the two crashes.

[cmurf]

It was both an unsafe airplane and pilots were not made aware of how everything worked.

A human pilot properly informed in advance could paper over an act of sabotage by a flight control system, but that does not make the airplane safe.

A single sensor reporting bogus data was used by a system to automatically take dangerous action. Both are dangerous. But in particular the latter, because it permits an excessive reaction to what is supposed to be merely stall avoidance, not recovery. Even stall recovery does not require anywhere near the kind of nose down amount MCAS was permitted to induce. That behavior is sabotage. If a human pilot did the same thing, with the same available bogus information, it would be incompetency. And if it lead to death, it would be manslaughter.

[vkou]

Is it common for commercial airliners to nose-up when approaching stall conditions, thus making them easier to stall? (Or something else, that sounds similarly dire to a layman?)

I understand that aircraft are complex systems, and they need to be used by experts, and that those experts are aware of, and have to work to mitigate a lot of catastrophic failure scenarios. Is the unstable flight caused by the forward-mounted engines a particular example of a 'typical' quirk of a commercial airliner?