Originally Posted by
yanrair
ie is the Boeing Ops Manual Bulletin TBC-19 entirely accurate... namely:
In the event of erroneous AOA data, the pitch trim system can trim the stabilizer
nose down in increments lasting up to 10 seconds. The nose down stabilizer trim
movement can be stopped and reversed with the use of the electric stabilizer trim
switches but may restart 5 seconds after the electric stabilizer trim switches are
released.
If this is true then it would be possible (not desirable) to use electric trim to override MCAS without using the cutout switches. MCAS could be interrupted and corrected every time it kicked in. I suspect it is not entirely accurate... I wonder if anyone has an authoritative answer?
MCAS can be interrupted with the electric trim switches on the yoke each time it activates, and trim can be returned to a low/zero column force state each time if the pilot puts in adequate opposite trim inputs. That is what the Lion Air crew did for approximately 2 dozen cycles of MCAS before the final few cycles, where the pilot flying at that point failed to put in an adequate amount of opposite trim in those final cycles, allowing the out of trim condition to increase to the point where they couldn't recover in the altitude available.