EDWARD MC DONALD: You are conveniently forgetting one critical thing: the stupid design team at Boeing implemented a wrong design practice: the active SINGLE Angle of Attack Sensor IS ALTERNATED from one side to the other at every following flight!. Now, the stupid thing with that design is that it is only advantageous in those cases where a more distributed wear is desired to extend the time between required maintenance or replacement of a component, like for example, alternating the use of an Spare Pump with the normally used pump to distribute wear… That makes the wear to be distributed among the two pieces of equipment. BUT, that engineering practice is NOT PROPER on critical systems, where there is the RISK OF HIDING an INCIPIENT FAULT being developed, as it tends to occult the failure by using the other side, still good component.
What is more, that WRONGLY APPLIED practice accumulates the components wear, so that it increases the probability of having a SIMULTANEOUS Failure At BOTH SIDES, at the same time.
Thus, the engineering team that designed that critical system at Boeing should be sent to both Engineering School (to UNDERSTAND WHY THEY DID A WRONG DESIGN), and to Jail, because you don’t play with others lives in an unprofessional way. Why and How it was so badly designed tell a lot about the state of matters at Boeing nowadays.