Salute!
Concourse has raised a very important legal point for this discussion on the main thread, and I agree 100%, but my personal preference here is to keep the legal aspects "legal" and concentrate on understanding what happened and identifying whatever it takes to keep this from happening again or another incident that could have been prevented.
Some here may even be flying the type and could use some "education".
++++++++++++++++++++++++++++++++++++++++++++++=
Being a pilot on my accident boards, I mostly look for causal and contributing factors that were out of human control at the time or prevented the human from overcoming the problem. So my interest in sfwe and hdwe is a large part of my personal investigation. I have seen out-and-out pilot judgement/skill crashes, basic smoking holes, but also one serious loss that involved "little understood" aspects of our autopilot implementation. So this MCAS brings back some sad memories.
+++++++++++++++++++++++++++++++++++++++++++++++
The trim gearbox is of more interest to me now than my poor opinion of the decision to move large control surfaces to "help" the pilot and not tell the pilot That gearbox is the last mechanical connection in the chain, right? And the control surface it moves has more pitch authority than the elevators. So I start there and work back to the first input to the doofer, whether from a human input or Hal input or combination.
How did the STS logic fail to provide up trim cmds as speed increased when I only see down cmds to the gearbox. Maybe the AoA prevented that, but I did not see a direct input to STS from AoA. Seems like STS uses speed data from the ADIRU and not raw "q" from the probes. So if the ADIRU logic asserts airspeed is FUBAR due to AoA problems, then what does the STS do? Inquiring minds want to know before my next flight.
A poster not so far back thot we may have seen the result of a cascade of events that had deliterious effects not allowed for or imagined. i.e. a single point failure that by itself should have only been an irritant, but other systems that used the output of that "module" reacted as designed and the chain of events created control surface movement that was not required and, indeed, was unsafe and could not be mitigated by the crew. In other words, the crew did not recognize what the problem was and kept trimming because every time they trimmed, the plane seemed to return to "normal".
The crew actions, even without knowing about MCAS, are an important part of this tragedy, but if things didn't break, they would not have had the opportunity to diagnose a new malfunction. So second to last flight did not identify the real problem because the "runaway trim" procedure seemed to have allowed a successful flight and a writeup. The accident flight would have been the same, and maybe next hop would be the tragedy.
Gotta go, and forgive my sermons.
Gums....