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> Suppose they did originally do what the fixed software does now, and disable MCAS if the AoA sensors disagree. The problem Boeing face is that with MCAS disab
by erentz 8y ago
> Suppose they did originally do what the fixed software does now, and disable MCAS if the AoA sensors disagree. The problem Boeing face is that with MCAS disabled when this occurs, the plane no longer flies like an older 737....
But it’s been reported that this was an option you could buy when you bought the planes. And the crashed planes didn’t have this option.
So if that’s correct, then any plane shipped with this optional package would require the recertification. But it appears they don’t either.
If they did it would show up as very suspicious and I’m surprised nobody has reported on it:
Here buy this plane without this optional package and you don’t need new training.
Or buy it with the optional package and you need to learn about these new components we’ve added that may be disabled and undergo new training.
It seems too obvious.
- mhandley 8y agoAn AoA disagree indicator was an option. But it was never an option for this to disable MCAS, as this would have resulted in a change of the flight characteristics that would have required training.
- erentz 8y agoOh! thank you I didn’t make that connection.
- michaelcampbell 8y agoWould a disagree indicator be an option without the second sensor? With what would it disagree?
- mhandley 8y agoAll 737s have two AoA sensors. The left one feeds the left air data computer and the right one feeds the right air data computer. The AoA disagree indicator displays when the two disagree, but is optional and was not fitted on the planes that crashed. The old version of MCAS only uses one AoA sensor as input, even if the AoA disagree indicator was fitted. It does, however, alternate which of the two it uses with each flight.
- ramraj07 8y agoIf that's true (that it alternates between the sensors each flight) then it's extremely obvious that a business decision was made to only use one sensor at a time.
- lagadu 8y agoI fail to understand how is the disagree indicator useful, considering the MCAS system will use the same AoA input regardless of disagreement. Is it useful for some other function?
- erentz 8y agoEdit: to be a bit clearer about what I’m saying: There’s no indication that before these accidents an airline buying the optional AoA disagree package got extra training to tell them about handling MCAS. And therefore it’s not clear that if these planes had this package they would’ve been saved. The pilots would’ve had a new warning light but not known that it means they need to disable MCAS because there was no training to that effect. If anything I assume the pilots being unaware of MCAS would only think an AoA disagree light impacted autopilot, which is separate from MCAS and disabled at these times. They would still have needed to identify the trim and MCAS problem another way. (Now it is a different matter since everyone knows it’s there.)