Originally Posted by
tdracer
The problem is, those smaller spikes can mimic a the wave form of a valid digital electrical input - and the LRU can't tell the difference. The fix was to change the software so it could differentiate between actual digital inputs and the lighting induced inputs.
That sounds like a data integrity problem. And it should have been considered in any FMEA long before the lightning struck. Lots of things can produce waveforms resembling an input, but with invalid data. Could be a sending LRU going brain-dead, some idiot who forgot to put a phone in airplane mode or other electrical interference including lightning. All communication buses should have checksums or parity bits. And a failure of one system (or injected bad signals) should not result in the failure of others. Having to land and reboot (or even cycle a breaker) should be considered to be a failure of the second system, the displays in this case.