A4 Pacific wrote:
dr107flyer wrote:.. in answer to the question about how often the system triggered, pretty close to zero other than the well known erroneous occurrences.
Presumably that is why Boeing took the decision not to even inform 737 Max pilots of the existence of MCAS until they were ‘forced’ to?
There are, AIUI, 2 AoA sensors on every Max, on each side of the nose; however, only one was routinely, by default, connected to the MCAS system. ISTR reading an account from a whistleblower who claimed that it would have been possible to connect both, compare the outputs by software, and either disable MCAS if they disagreed or alert the pilots to a disagreement allowing them to disable it (and follow a more constrained set of attitudes), or make it a no-go item if the disagreement existed before takeoff (when taxiing and into wind) or when rolling but well before Vr. But any of the latter would have involved extra training for pilots converting from other 737 variants, and Boeing's principal selling point to the customer airlines was that no such training (and costs thereof) would be necessary. For that reason the option to connect both was readily installable (software almost all that was needed), but was not proactively mentioned to customer airlines.
If that is true, combined with new story alleging poor workmanship which might have led to erroneous indications from 1 of the 2 AoA devices when the other might have been working, the initial decision not to use both seems even more culpable.
But I have no relevant expertise as engineer or ME pilot ..
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