> Boeing was able to gain FAA approval for the MCAS system with one angle of attack sensor and pilots as backup. Over the years I've designed/ implemented sma

> Boeing was able to gain FAA approval for the MCAS system with one angle of attack sensor and pilots as backup. Over the years I've designed/ implemented small scale industrial systems and whenever there was an important set of data to be read in via sensors, there'd always be a backup, or ideally triple redundancy. Sensors are cheap & using multiple can simplify a whole lot of issues. Even once, I made an uber simple 'level' sensor on a front end loader (using two slightly rotated Mercury switches). It's only time I didn't consider redundancy, because it was not important at all if it failed. What I don't get is how the engineers at Boeing didn't use redundant sensors. Have I misunderstood something? I just assumed that working on aircraft means that something like sensor failure should be baked into all decisions and implementations because of the -ve ramifications of things going wrong: like 2 planes dropping out of the sky!