Originally Posted by
FCeng84
Beyond that it is clearly a violation of the FARs for a system to have a failure mode arrived at by (1) any combination of failures whose probability is greater that 1x10E-9 or (2) any single failure that results in a catestrophic hazard level.
While in hindsight it may be found to be otherwise, I am certain that both Boeing and FAA determined that the hazard level associated with an AOA sensor signal failed high on a 737MAX was not catestrophic. As I have mentioned in previous posts I think this all comes down to assumptions regarding pilot actions given this failure and the sum total of its effects. I am not singling out the crew as solely responsible for the Lion Air accident. We need to focus on the assumptions. As for the Ethiopian accident that is the intended focus of this thread, we simply do not yet have the data necessary to determine if any of this MCAS and errant AOA signal discussion actually applies.
No argument with your analysis but;
The so called system safety e.g. "any combination of failures whose probability is greater that 1x10E-9" may not be specified when a more specific rule has been applied via another part of the regulations.
I think it would be best that we confine our discussions around the actual rulings by the FAA that permitted this control logic.