Originally Posted by
GordonR_Cape
Very interesting information, but raises more questions than answers!
My first question is why did MCAS not activate, unlike the other two cases?
I would speculate 3 possible answers to that:
1. The flight was in autopilot at the time (inhibiting MCAS), and/or FCC was subsequently turned off by crew, or kept on till flaps down.
2. The AOA fault on captain's side may have been nose down (not nose up), so that stick shaker and MCAS were not triggered.
3. On that flight MCAS was active on the co-pilot's flight computer (not captain's side).
They may have survived purely by these chance factors (or good CRM...)
Edit: A question about what happened to the faulty ADIRU: Was it kept and repaired, sent back to the manufacturer, or perhaps handed over to the Canadian TSB? Was this a reportable event, or purely a maintenance issue?
There is nothing in that report to indicate there was an AOA problem, specifically. The symptoms sound more like a failure of the ADIRU itself. If the air data portion of the ADIRU failed, it would cause a miscompare in altitude or airspeed. If the IRU portion failed, it would cause a miscompare in pitch, roll and heading. Either type of failure would cause an autopilot disconnection.
The weather radar depends on accurate IRU pitch and roll data for stabilization, and IRU data is also used by the TCAS.
Because of the two crashes, now ANY in-flight technical failure on a 737-8 MAX aircraft is going to draw immediate media attention - as we saw just a few days ago with the engine problem on the SWA ferry flight departing MCO.