A320 Reversible Alpha Floor

[safetypee]

Gentle questions seeking understanding: a non AB operator, no technical knowledge of this system.

From the descriptions so far;-
Does the word ‘reversible’ indicate the computational method, the reversal of the process which displays AoA as speed on the speed tape (used in alerting and control functions related to airspeed, alpha floor): i.e. reversible - use AoA to compute speed in the event of speed failure.
Does the SMF (RSF) fill-in a weakness in cross monitoring in aircraft with three identical sensors (or combined sensor computation - air data).

In ‘older’ aircraft with identical dual input, and a different standby instrument as the third system, the cross-monitoring of primary systems is a simple difference comparison, which alerts the crew to check the standby, and then they (the human) decide which main system is ‘probably’ more accurate (two out of three voting).
If both primary systems were simultaneously in error, then although the standby might be accurate the crew would not know, but at least might have an indication of which system was at fault via alerting, e.g. altitude or airspeed, etc, independently.

In other aircraft with combined Air Data this may not be as easy, but most certification requirements assume that multiple failures will be of short duration - temporary (probability).

Modern aircraft may use three identical sensors and airdata computers. Although the likelihood of failed inputs is as above, the crew may not have any indication of which system is in error or which component of airdata is incorrect, not knowing if it is the sensor, computation, or airdata subsystem; there are multiple alerts, e.g, airdata and speed, etc, simultaneously. Also, because of very high system integration many other aircraft systems can be affected and alerted.

So, the question is if a purpose of the SMF is to clarify, simplify ambiguous failures and maintain speed protections. Technology is used to aid the human with assessment;- instead of the man aiding the digital machine (dual + stby), the machine aids the man, a combined system of man and machine together (enhanced triple-mix)

Is this an extension of the ideas behind BUSS (speed), but including the suite of sensors in ‘triple’ airdata comparison; not a specific certification requirement, but acknowledging increasing system complexity and rarity of malfunction.
If so, then BZ to the design in taking the initiative in recognising the limitations of human performance and the challenges arising from the widespread use of computational technology (Vilas; not automation replacing the human, but technology aiding the human).