121.5 is the “guard frequency” or more formally, the international air distress frequency. Airline pilots will monitor this frequency whilst flying, as well as air traffic controllers and flight and emergency services. In addition, emergency locator beacons attached to aircraft will also transmit on this frequency, which sound like a high pitched siren when they do go off.
You would have never thought that your pilot at the front may be burping or farting down the mic on the international air distress frequency did you?
Keeping in mind the serious nature of having this frequency clear of interruptions, what I do find amazing is how often it is filled with childish noises and silly requests! Some of the drivel I’ve heard: burps, farts, cat “meows”, some random bloke shouting “FRANCCCOOOO!”, requests for sports scores, snoring, passenger addresses (these are meant to be given to passengers in the cabin) and of course the odd fellow policing the channel and shouting “YOU’RE ON GUARD!” in an aggressive (albeit probably justified) tone. You would have never thought that your pilot at the front may be burping or farting down the mic on the international air distress frequency did you?
I have of course never resorted to such childish behaviour (unless I’m at home annoying my family for entertainment).
Pilots asking for or chatting about the football scores on guard annoys me a little. We get requests from passengers to ask for them as well, and though I am all for customer satisfaction, I really do not want to piss off London control and everyone else on the frequency with this strange request. Especially so, considering the frequency is congested as it is!
Over the years of flying the most common use of 121.5 I’ve heard is for aircraft that have lost radio contact with the air traffic controller. This could be for a variety of reasons – maybe the pilots have forgotten to establish initial communications with the controller on handover, or pilots have not been listening to the controller, or maybe the controller has forgotten about the aircraft and not handed them over to the next controller and lost radio contact. This is formally known as “Prolonged Loss of Communications” or PLOC. This can be a security and a safety issue, and airliners can be potentially intercepted by military aircraft. The last thing a Captain would want to see is a military aircraft on the left side of their airplane…