@jimjim & safetypee RE: AOA DISAGREE alert NG not MAX
Many thx.
My point is that if for years and years one has been flying and in particular training for non-normal situations on the NG, the subsequent "unexpected" absence of an AOA DISAGREE alert on the MAX could leave one with an important cue less than expected if things go AWOL, as they did, in the sense that "undesired MCAS activation due to a single AOA sensor failure that could lead to a flight crew to perform a non-normal procedure".
Reason why I found the FAA observations in the Final Rule/AD of this week on the "error" by "the manufacturer" not to install an AOA DISAGREE alert on every MAX quite pedestrian.
It is therefore good to read now (and already in fact since the August 2020 FAA NPRM release) that amongst the new requirement for the MAX, the flight control laws would be changed in so far that MCAS activation requires inputs from two AOA sensors in stead of one. The updated MDS software is also to implement an AOA DISAGREE alert function on all 737 MAX airplanes (as is the case on all NG). While the lack of an AOA DISAGREE alert is not an unsafe condition itself, the FAA now mandates this software update to restore compliance with 14 CFR 25.1301 and because the flight crew procedures mandated by this AD now rely on this alert to guide flight crew action. As a result, differences between the two AOA sensors greater than a certain threshold would cause an AOA DISAGREE alert on the PFDs.
Last edited by D Bru; 22nd Nov 2020 at 16:21.