Soldato
Just to discuss some points you raised -
Yes it does, the "sensor reliability" software is an output cross-check which is installed when they added the extra AOA display to the PFD and shows "AOA DISAGREE" on the PFD if both AOA's show a different result. This already available software is installed as part of an AOA upgrade being added by US firms like Southwestern (link here) and NOT the new patch stuff which is due later and works in a different, less effective way.
Not right, see above. The patch looks like it changes limits within the Control Laws to make the MCAS pitch down demand less forceful but over a longer duration (demand vs time) and it looks to have no additional "sensor reliability" addition over what it already has, which is - if the sensor is broke then MCAS doesn't work - and therefore not the same as being cross-checked between two sensors in the available software mentioned above.
The biggest 737 MAX US carrier is Southwestern with 34 which is only just adding it now after complaints post the Lion crash, the other two US carriers have less aircraft (9 United and 24 AA) and only AA have said they already have the extra AOA displays, United haven't said anything.
True but I'd say it would have shown the crew immediately after take-off that there was an AOA discrepancy via the "AOA DISAGREE" on the PFD. The crew would then know immediately that the left AOA probe was bad as they could cross-check between Pilot and F/O displays, helping the crew diagnose the MCAS problem much quicker, especially after the post Lion crash brief regarding MCAS/AOA. However, even with all that extra info, the extra brief about AOA/MCAS post the Lion Crash etc I honestly don't know if it would have changed anything but I'd like to think it would.
The 'additional AOA/MCAS software and extra "sensor reliability" checking software' does not yet exist on current fleets
Yes it does, the "sensor reliability" software is an output cross-check which is installed when they added the extra AOA display to the PFD and shows "AOA DISAGREE" on the PFD if both AOA's show a different result. This already available software is installed as part of an AOA upgrade being added by US firms like Southwestern (link here) and NOT the new patch stuff which is due later and works in a different, less effective way.
it will form the basis of the software patch yet to be implemented
Not right, see above. The patch looks like it changes limits within the Control Laws to make the MCAS pitch down demand less forceful but over a longer duration (demand vs time) and it looks to have no additional "sensor reliability" addition over what it already has, which is - if the sensor is broke then MCAS doesn't work - and therefore not the same as being cross-checked between two sensors in the available software mentioned above.
Most of the US fleet of Max's do have an addition AoA readout however - this is a standard option for Boeing aircraft, but you have to pay for it.
The biggest 737 MAX US carrier is Southwestern with 34 which is only just adding it now after complaints post the Lion crash, the other two US carriers have less aircraft (9 United and 24 AA) and only AA have said they already have the extra AOA displays, United haven't said anything.
And it's debatable whether or not this readout would have prevented the crashes.
True but I'd say it would have shown the crew immediately after take-off that there was an AOA discrepancy via the "AOA DISAGREE" on the PFD. The crew would then know immediately that the left AOA probe was bad as they could cross-check between Pilot and F/O displays, helping the crew diagnose the MCAS problem much quicker, especially after the post Lion crash brief regarding MCAS/AOA. However, even with all that extra info, the extra brief about AOA/MCAS post the Lion Crash etc I honestly don't know if it would have changed anything but I'd like to think it would.