Originally Posted by
auv-ee
It seems that an alternative air speed measurement is needed to augment the pitot tubes, something that would be affected differently by environmental effects and other failure modes.
Already exists - BUSS. Not fitted on AF airbuses. There seem to be some widely varying opinions of how well it works. AF rationale for not fitting it is here:
Air France - Corporate : The BUSS or "Backup Speed Scale"
I believe BUSS is standard on A380, where it was optional on earlier models.