Without additional explanation, the installation of an AoA Disagree alert as standard appears to offer little benefit.
IAS and Alt disagree alerts should trigger the need to cross check and compare values with a third system - St By ASI / Alt. However, without a third, independent source of AoA no such comparison can be made, although there may be some value in knowing about an AoA issue.
What is the procedure associate with ‘AoA disagree’; the issue being addressed is MCAS malfunction, and of prime importance to the crew - ‘TRIM’; where are the alerts for these.
The crew would have to deduce whether ‘AOA disagree’ is associated with stick-shake or air-data (IAS / Alt), perhaps adversely biased by the attention getting display of low speed awareness - speed and stick-shake agree.
Such a modification might result is increased workload, possibly confusion, supposedly adding awareness but without a direct course of action. Thus system modifications must focus on the system design and operation, and if engineered appropriately, then the use of additional alerts or displays might be best avoided, reducing workload, or distraction from the primary task of flying the aircraft.
Similarly the ‘additional’ option of an AoA display, without underlying systems improvements this may be of little value - again a distraction. This and the ‘disagree’ alerts appear to be a sop to public views and ill-informed media.
WHBM, #
Ethiopian airliner down in Africa 