The opt-in feature you mention was for a disagree alert for the plane’s angle of attack sensors.
But, MCAS was only ever using a single angle of attack sensor as its source of truth, so if there was a fault in that single sensor, MCAS could activate at normal attitudes.
But the real problem was that Boeing hadn’t documented MCAS, to avoid the requirement for pilots to obtain type certification for the MAX (so any existing 737 pilot could to fly it without additional training - and it wasn’t just Southwest objecting to this training), and to avoid a full FAA certification process for the MAX.
So on an MCAS activation, even if they had had an AoA alert, pilots would not know how to instinctively deal with it. (I don’t doubt an AOA disagree alert would give invaluable information allowing the pilots to rule out most failures, which when only a few thousand feet high would maybe have saved both planes.)
On the previous day to the Lion 610 crash, the incident aircraft suffered an MCAS activation and fortunately a pilot in the jump seat realised what was happening and what was needed to deactivate it.
It seems being sat behind the trim wheels (so he could see they were moving) and not wrestling to keep the plane in the sky at the same time was needed for that to happen. It must have been terrifying.
But, MCAS was only ever using a single angle of attack sensor as its source of truth, so if there was a fault in that single sensor, MCAS could activate at normal attitudes.
But the real problem was that Boeing hadn’t documented MCAS, to avoid the requirement for pilots to obtain type certification for the MAX (so any existing 737 pilot could to fly it without additional training - and it wasn’t just Southwest objecting to this training), and to avoid a full FAA certification process for the MAX.
So on an MCAS activation, even if they had had an AoA alert, pilots would not know how to instinctively deal with it. (I don’t doubt an AOA disagree alert would give invaluable information allowing the pilots to rule out most failures, which when only a few thousand feet high would maybe have saved both planes.)
On the previous day to the Lion 610 crash, the incident aircraft suffered an MCAS activation and fortunately a pilot in the jump seat realised what was happening and what was needed to deactivate it.
It seems being sat behind the trim wheels (so he could see they were moving) and not wrestling to keep the plane in the sky at the same time was needed for that to happen. It must have been terrifying.