Did ATC tell them to do that? Did they tell ATC they were going to switch to SELCAL?
It would be a hell of lot easier if people knew what they are talking about.
ATC doesn't tell you to. It's just standard procedure. One doesn't swithch to SELCAL, one IS on SELCAL watch unless the test proved negative.
Since the dark age of aviation in this area, radio contact remains flimsy, always have always will. ADS is supposed to be the magic bullet and it is when it's working, which is most of the time.
No radio contact would have prevented the loss of this aircraft and as far as mayday call goes, they had thousands of other things to to do like try to save the aircraft, be afraid and stressed like most of you won't ever be in 3 life times.
I think this thread should be closed until the BEA comes up with something new. It is getting both boring and repetitive.