Originally Posted by
Lead Balloon
Just rejuvenating this thread and won't mention 'the other' event.
Contrary to my earlier surmising that any sensor measuring ‘in the air’ versus ‘on the ground’ could drive both TCMAs on the 787 to the ‘on the ground’ state, a ‘whole of aircraft’ ‘decision’ is made that the aircraft in ‘in the air’ or ‘on the ground’, taking in consideration all of the sensors and, in the case of 'disagreement', disregarding whichever of them is most likely to be erroneous. The probabilities of the 'aircraft' 'choosing' the wrong state are, consequently, extraordinarily remote.
We can be sure that a single sensor can not be certified when it comes to catastrofic failure, for example that both engines quit in flight (IFSD).
From CS25, there’s a link from the engine installation paragraf to this:
§ 25.1309 Equipment, systems, and installations.
The airplane systems and associated components, evaluated separately and in
relation to other systems, must be designed and installed so that they meet all of the
following requirements:
(1) Each catastrophic failure condition—
(i) Must be extremely improbable; and
(ii) Must not result from a single failure.