Pan Pan or Mayday depending on the circumstances. By some poster's logic pilots of single engine aircraft should include Mayday in their taxi call. The definitions are in Annex (10?) to the Chicago Convention.
The radiotelephone distress signal to indicate grave and/or imminent danger requiring immediate assistance is
MAYDAY, MAYDAY, MAYDAY.
The radiotelephone urgency signal to indicate a condition concerning the safety of an aircraft, vehicle or of some person on board which does not require immediate assistance is
PAN PAN, PAN PAN, PAN PAN.
To anyone with a grasp of English either might be appropriate depending on the nature of the failure and performance.
Both are acceptable means of declaring an emergency. And, contrary to what many will tell you, all ICAO countries have a similar radio licence syllabus and Pan/Mayday calls are an easy mark, right after the phonetic alphabet! Ask any Air Trafficker from Lagos to Tokyo. Even my wife knows that after doing a day boating course.
HOWEVER; a generation of simulator instructors seem to have succumbed to the view that perceived conservatism equals increased safety. Perhaps some were indoctrinated by previous companies SOPs, or by that habit in aviation of adding margins to margins, or simply by peers strong opinions.
Whatever the cause, just like any language changes over the years, so has aviation language. Particularly in Asian countries; when you are doing a check Mayday has become the default call for engine fail on a twin. You won't get a 5 if you use PAN.
I don't like to see aviation phraseology diminished by 'ghost' procedures but this is the reality. The PAN call is slowly being eroded out of use.
Last edited by HPSOV L; 14th December 2014 at 15:41.
Reason: Clarity