There has been some arguments posted here about why the pilots of AF447 would not send any mayday when in beginning trouble.
On a.net you can find a description of an event on AF445 between Paris and Rio, where the pilot called mayday upon hitting severe turbulence.
AF445: Mayday Call Due To Severe Turbulence — Civil Aviation Forum | Airliners.net
The handling of CVR and other info by AF after the flight sound strange or sloppy to me. Furhermore, the disk problem with the QAR is also strange. Such things can often be solved (at least partly) by disk-specialists if one is willing to pay.
Nor do we know if any ACARS similar to AF447 were sent.
BEA is very silent about this incident and I had to dig around a lot to find a short comment saying that the incident was being investigated because it might help to shed some light on AF447.
Regards