Regarding the 737 MAX story, the New York Times writes:
"Boeing’s software update would require the system to rely on two sensors, rather than just one, and would not be triggered if the sensors disagreed by a certain amount, according to the three people. Given that the 737 Max has had both sensors already, many pilots and safety officials have questioned why the system was designed to rely on a single sensor, creating, in effect, one point of failure [emphasis mine]"
Now I understand that this avoids a False Positive, when one erroneous sensor triggers the MCAS.
But, considering the opposite situation, doesn't this update introduce a new single point of failure, a False Negative, when a stall should be counteracted with MCAS but it isn't, because only one sensor detects it?
(Or if not, what am I missing here? Is it that a faulty sensor fails in a certain way and will not read normal AOA erroneously?)