>Boeing cheaper out on the Angle of Attack detector, by default only one is installed, a second one as an added-cost option.
This is incorrect.
The 737 MAX 8 comes with two AoA vanes.
The paid upgrade package is to wire them both into the flight computer, and to add an AoA disagree notification light.
>To be fault-tolerant, you need a quorum and thus a minimum of 3, as Airbus does. I would also add the 3 need to be made by different manufacturers to avoid systemic issues, if disk array manufacturers can do it, so can Boeing for safety-critical equipment.
This is correct, but not infallible. It's really complicated as the last batches of discussion here have gone into great length on.
Boeing fubar'd by not accurately categorizing MCAS as a safety-critical system, as their original classification was "Hazardous" instead of "Catastrophic".
The original implementation had only +/- .6 degrees authority. After the paperwork was filed, they upped the gain to 2.5 degrees up to maximum trim down over time, without reclassifying the subsystem as safety critical. Therefore no-one ever made sure that subsystem chain was bulletproof.
