Originally Posted by
MickG0105
That statement neatly sidesteps the fact that on the B737, AOA data had never previously been used to directly inform 'the pitch trim system'.
Mmm, might want to check with respect to the NG. Maintenance manual (don't have FCOM but be interested to know what is in it on this) says:
Near stall, the speed trim function trims the stabilizer to a nose down condition to allow for trim above the stickshaker AOA and idle thrust. The trim continues until the stabilizer gets to its limits or the aft column cutout position is exceeded
Note: FCC / speed trim functional diagram labels this function "stall detection circuit".
MCAS is different in several ways (not least that various folk are saying earlier in the thread that MCAS is
not about stall or stall detection). I doubt that this NG "stall detection" (and action) is still part of speed trim function in the MAX, I suspect that MCAS has replaced it (and probably evolved from it). One or more of the MCAS differences must account for the fact that Boeing and the FAA both appear to believe that JT610 cannot happen on an NG, and that may also be the key to understanding it, but I'm not convinced we even understand all the differences yet.