Hello,
I have just been re-reading airlaw to remind me of everything I forgot at the start of my PPL course and came across the reasons for setting 7700 on the transponder.
7700 - to indicate an emergency condition (except that, if the aircraft is already transmitting a code and receiving an air traffic service, that code will normally be retained)
However I have always been told to set 7700 regardless of whether you are with an ATC unit or not. Therefore from an ATCO's perspective would you want me setting 7700 or retaining the squawk I had been given earlier?
Thanks.