Spunkey Monkey :"Over Western Europe, is there any need for everybody to be on 121.5?
There are so many ground stations etc that the coverage is almost 100%."
We drivers airframe`s large have no choice for a couple of reasons
a. Good Airmanship - someone who is in trouble can rapidly become your problem, a depressurerisation at a level above you? They are going to call on 121.5 that they are on the way down. Remember airspace in Europe is like a cake with sometimes 3 frequencies in the same area at different levels.
b. Legal Requirement - every once in a while we are called on 121.5 to make sure we are monitoring, also happens in US airspace.
c. Airline SOP - nuff said.