SHUT UP ABOUT THE LACK OF RADIO CALLS
Radio calls to ATC are the LAST thing you consider doing when faced with a major problem of any sort concerning the aircraft. People on the ground cannot usually help quickly.
Professionals adhere to a 3 step sequence....Aviate....Navigate....Communicate.
After all, what is the point of wasting essential time talking to people who are not in a position to help you.
(Sorry, ATC, you are essential in crowded and tricky environments, but not to immediately help with tech/weather/terrorist/passenger issues, mostly tech.)
So in a case like this, the CVR and FDR may give all the info needed to solve the questions. Radio calls may not.