Peter H, ‘MCAS was used because it was already there’, and if implemented appropriately it would be a non issue - except.
Considering the CS definitions of stall warning (shake ~ 1.1Vs) and stall ident (push ~ Vs), and assuming that the Max non-MCAS approach to the stall characteristics were adequate, then for any nose-up tendency >1.1Vs the need would be for more stick force (trim down) and should be considered as a stability issue - a smooth change with Alpha, opposed to a step changes from a nudge, i.e. use MCAS.
Alternatively if the <1.1Vs non-MCAS pre stall characteristics were deficient (most likely), the use of the stability improving MCAS as a stall warning would be unusual; convention uses a shaker. I would disagree with Satcom’s views because of the differences between a step nudge and a smooth stability change, and the need to argue equivalence with a shaker.
However the objective was to mimic NG characteristics without a shaker, and the driver for all of the above was to avoid changes / training for the Max vice NG by using a background mechanism, not overtly visible to the crew (and thus not necessary to describe it).
As for cost, even in hindsight, who can tell. Avoiding the potential cost of training - Southwest, $1m / aircraft, could have provided an elegant alternative solution, but there were other drivers - timescale, competition.
Yet the concept of MCAS was an ‘elegant’ solution; the implementation was appalling, and it appears that the latter has to be improved to achieve recertification.
Last edited by safetypee; 1st Nov 2019 at 17:48.