“MAX had a procedure to handle runaway stab trim”
I’m not an expert on piloting or the 737MAX.
Someone told me that with the two planes that crashed, the pilots were going through a step-by-step procedure to handle their situation, but the plane crashed before they got to the step that told them to disable MCAS.
It bothers me that MCAS failed in these two situations because the angle of attack sensor, which is a small airfoil protruding from the fuselage, was damaged, and that these angle of attack sensors are subject to being damaged by something like a bird hitting them.
Particularly bothersome is that Boeing had an extra-cost option to MCAS that would detect a wacky sensor. Very bad PR for this to be an extra cost option.
Here's a link to the preliminary report for the Ethiopian Air accident.
They initially performed the procedure for runaway trim. However, they were slow to identify the problem and by the time they disabled pitch trim, MCAS had put the aircraft into a dive that they could not recover from.
They deviated from the procedure and put pitch trim back on. They were then able to level the aircraft using the trim buttons on the yoke. When they stopped using the trim buttons, MCAS kicked back on and pitched the aircraft back into a dive.
They then tried to recover by pulling back on the column but did not have enough elevator authority to recover.
Particularly bothersome is that Boeing had an extra-cost option to MCAS that would detect a wacky sensor.
The extra cost options were AOA display on the PFDs and "AOA Disagree" warning message. These MAX options were standard on the 737 NG. Why Boeing took them out of the MAX and made them priced options is a huge question, still to be answered.