Hi all,
this is my first post, I´m just working through the forum... lots to read....
Just a european point of view:
When we (military SAR) are on a training sortie and then get tasked for a medevac from an island, a ship, etc, we would let ATC know that our callsign has just changed (from the RCC and thereby operating authority) to Medevac or even Rescue if appropriate.
When someone on board gets a medical emergency then this in my eyes would be a PAN or a MAYDAY. Only primary or secondary SAR assets can use the callsign MEDEVAC or RESCUE.
Regards,
Thomas