Thoughts on Seattle Times article published Sunday morning Seattle time
This article is generally well written and seems quite accurate. One point of clarification is that early on in the 737MAX development it was thought that MCAS would only be needed at particularly high Mach numbers. For those conditions the prediction was that the original 0.6 degrees of MCAS stabilizer authority would be sufficient. That proved to be pretty close to the case during flight testing and the final MCAS increment size for cruise and higher Mach numbers is very close to 0.6 deg. Later on it was determined that MCAS would also be needed at lower Mach numbers. With that extension of MCAS came the MCAS authority vs. Mach number schedule that is in the current design. The high Mach end of that schedule is approximately 0.6 degrees. Only with Mach Number less than 0.4 is the MCAS authority 2.5 degrees. The larger authority at lower Mach numbers is needed as the effectiveness of the horizontal stabilizer is less at lower speed. It is quite common that flight control functions are given higher authority at lower airspeed and less authority at airspeed increases.
A second point that did not come through particularly clearly in the Seattle Times article is that the pending MCAS software update has been in the works at Boeing since shortly after the Lion Air accident. As the data for the Ethiopian accident is not yet available (or maybe just came available) nothing that Boeing would be getting out the 737MAX fleet over the next couple of weeks could possibly be based on the most recent event. I'm sure that the team at Boeing will be evaluating the ET accident data as soon as they are able to see (1) if MCAS played any role in this accident, and (2) if MCAS did play a role, how would MCAS have behaved differently had the proposed updates been in place.