I discovered the following document on smart cockpit:
SmartCockpit - Airline training guides, Aviation, Operations, Safety
It is an Airbus presentation about Unreliable Airspeed from 2006.The document does not appear to be complete as some videos are missing but it does show that Airbus offer a backup speed scale rather like a traditional fast slow indicator. to cater for air data problems.
I wonder if the AF aircraft had this mod fitted?Has anybody got any experience of using this Airbus mod?