Originally Posted by
Speed of Sound
Well in the case of the MAX it certainly was down to savings.
Quite simply, Boeing tried to make the 737 more fuel efficient by fitting a 2.5 metre diameter engine to an airframe originally designed for, and fitted with a 1.25 metre diameter engine. MCAS came about to avoid redesign/recertification and huge savings in training costs to their clients allowing Boeing to knock $1 million off the list price of each aircraft. Once the MCAS route was decided upon, further savings were made by including virtually no redundancy, altering trim logic and setting up a massive ‘gotcha’ which claimed 346 lives.
This was very much about making savings, as the technology and skills existed for a better solution but were simply not chosen.
How much would it have cost them to perform some kind of sanity check on the AoA input (assuming single sensor input)? Zero.
How much would it have cost them to design MCAS so that it stopped trimming down at a position short of the max stab trim position? Zero.
How much would it have cost them to design MCAS so that it stopped activating if it was repeatedly interrupted by ANU MET? Zero.
How much would it have cost them to leave the cut-out switch logic the same? Zero. (note: it's far from clear this had anything to do with either accident)
The decision to implement MCAS to solve certification issues was certainly to save costs, but the lousy implementation just looks like a screw up. The bad design decisions (other than perhaps not cross-checking the AoA sensors) didn't save any money.