Originally Posted by
CurtainTwitcher
In a word: profit.
Doing any sort of AoA comparison, would require a warning to the crew, and any new warning would have reduced the probability of a common type endorsement
without simulator time for the training. This was a key design criteria for the MAX,
no crew training beyond a short iPad course. Southwest included a $1 million per airframe penalty in the contract for the MAX if simulator training was required.
I don't know how much of the MAX threads you have read, the key name you want to search for is Rick Ludtke on this issue (
pprune.org search). He documents internal Boeing design mandate. There hasn't been a denial from Boeing as far as I am aware.
Yes, it is really that simple, to maximise sales and profit, every change had to be viewed through the prism of continued commonality.
The customer drumbeat of "no new training/no new endorsement" was clear.
The Max was supposed to ship with the AoA disagree alert, but it does not appear that it specifically alerts that that's the reason for other systems to be unreliable, nor does it appear to pass that status within the FCC currently in control of the stabilizer trim functions. It's this latter function that is being added to the new software.
https://www.satcom.guru/2018/11/737-...n-command.html description claims that each FCC gets data from both ADIRUs, including AoA data, but that description seems to be about autopilot operations. Other information says that each FCC was dependent on the same-side AoA sensor for handling MCAS when it was their turn. Quite confusing.