The radiotelephone distress signal to indicate serious and/or imminent danger requiring immediate assistance is
Why this is the answer
Per the TC AIM and radiotelephony procedures, the distress signal for serious and/or imminent danger needing immediate assistance is “MAYDAY, MAYDAY, MAYDAY,” spoken three times. PAN PAN is for urgency, a lower level.
Reference
TC AIM-COM – Emergency Communications TC AIM-SAR – Declaring an Emergency RTORC – Distress Communications
Question reproduced verbatim from Transport Canada’s PSTAR Study and Reference Guide (TP 11919E). The answer key is Transport Canada’s; the explanation is ours.
A study aid — not a substitute for the official guide, the CARs, or your instructor.