Hi,
"lack of signal" condition
The sub systems "interact in a completely safe way" (protocols, CRC, etc.)
A (HARD) failure as mentioned strongly motivates me to go deeper in the issue.
NAV TCAS FAULT (2 h 10): ... it could be the consequence of an electrical power supply problem or of an external failure.
F/CTL PRIM 1 FAULT (2 h 13): ...or be the result of a failure.
F/CTL SEC 1 FAULT (2 h 13)...or be the result of a failure.
1.16.2.4.3. Interruption of the messages:
... loss of one or more system(s) essential for the generation and routing of messages in the aircraft: ATSU / SDU / antenna... or loss of electrical power supply: this would imply the simultaneous loss of the two main sources of electrical power generation.
Intriguing: A redundant System
possibly hit by multiple failures.
Question: What kind of "external stimuli" (to a redundant "electric/electronic" System) has the ability to make it (possibly) fail in that way?
Note: BEA analysis on above msgs. show first other possible reasons and is not conclusive (by lack of further info.; ACARS is for other purpose).