MAYDAY will usually get attention, everything else is beneficial.
My first 'MAYDAY' came over 243.0 when I was doing Approach at RAF Strubby in 1965/66, a few months out of Shawbury. It was a simple call, from a TF-100 pilot who had ejected somewhere east of Linconshire over the wet stuff. What he actually said, on his PLB on 243.0 in a deep Southern US drawl as he drifted down in his parachute, was "This is Wiggins, is anybody there?" Those words were engraved on my brain to this day!
I had just had a Dominie depart up the east-bound climbing lane, so I just vectored him down the CADF trace I had received from 'Wiggins', liaised with D&D, and let the experts get on with it. Wiggins was saved by a helicopter, sadly his colleague wasn't.*
But I did use his example as a lead-in to using proper Emergency calls, instead of saying "Err, Eastern, err, we have a problem, err, looking for recovery" when I was a visiting lecturer from Eastern Radar at their Instrument School. I spent a lot of time trying to explain there was no charge for emergency services, and Pan or Mayday (with details) makes things run much more smoothly and safely.
So, in essence, on either 121.5 or 243.0, just give ATC as much info as you can, ideally in the right format, but WTF ... we will sort it out! That's what we were paid for.
* Some years later, Capt. Wiggins was serving at Lakenheath on F-111s when I was at Eastern. Sadly I never got to meet him.
Last edited by MPN11; 2nd May 2017 at 17:06.