-Cannot obtain meaningful voting on the validity of the data source, it is either OP or INOP.
-Cannot achieve failure rate (typ 10^-9) for critical flight control components and thus probability vs severity wrt stalling and departure from controlled flight.
-Without it aircraft is still uncertifiable wrt to 25.203 and it is still very shady wrt 25.1309 and single source failure.
-Ah and also, lets discuss bit a windsheer scenario, full power on application and pitch up.....
Here's the text of 25.672.
§ 25.672 Stability augmentation and automatic and power-operated systems.
If the functioning of stability augmentation or other automatic or power-operated systems is necessary to show compliance with the flight characteristics requirements of this part, such systems must comply with § 25.671 and the following:
(a) A warning which is clearly distinguishable to the pilot under expected flight conditions without requiring his attention must be provided for any failure in the stability augmentation system or in any other automatic or power-operated system which could result in an unsafe condition if the pilot were not aware of the failure. Warning systems must not activate the control systems.
(b) The design of the stability augmentation system or of any other automatic or power-operated system must permit initial counteraction of failures of the type specified in § 25.671(c) without requiring exceptional pilot skill or strength, by either the deactivation of the system, or a failed portion thereof, or by overriding the failure by movement of the flight controls in the normal sense.(c) It must be shown that after any single failure of the stability augmentation system or any other automatic or power-operated system -
(1) The airplane is safely controllable when the failure or malfunction occurs at any speed or altitude within the approved operating limitations that is critical for the type of failure being considered;
(2) The controllability and maneuverability requirements of this part are met within a practical operational flight envelope (for example, speed, altitude, normal acceleration, and airplane configurations) which is described in the Airplane Flight Manual; and
(3) The trim, stability, and stall characteristics are not impaired below a level needed to permit continued safe flight and landing.
[Amdt. 25-23, 35 FR 5675 Apr. 8, 1970]
I've bolded the relevant text. Paragraph (c) allows for single failures of MCAS sensors.
Note that (c)(1) requires that the airplane be safely controllable with the approved operating envelope. Operations near stall are not considered to be within the normal operating envelope.
As MCAS 2.0 will only normally activate outside the normal operating envelope, its failure to function after a single failure (eg a single AoA sensor with a subsequent MCAS shutdown) will not violate the requirements for (c)(3). MCAS 2.0 shutdown annunciation will provided by the "AoA Disagree" Alert
If two sensors fail to the same high AoA level, then MCAS could have one stabilizer cycle in the normal operating envelope. The single stabilizer cycle can be countered using the elevator and then trimmed out using stabilizer trim so full elevator functionality is regained.
25.1309 is not applicable as 25.672 allows for a single failure as long as continued safe flight and landing can be shown within the normal operating envelope.