Международный сигнал бедствия "Мейдей"

Emergency procedure word used internationally as a distress signal
the distress signal

Mayday is an emergency procedure word used internationally as a distress signal in voice procedure radio communications. It is used to signal a life threatening emergency primarily by aviators and mariners, but in some countries local organizations such as firefighters, police forces, and transportation organizations also use the term. Convention requires the word be repeated three times in a row during the initial emergency declaration ("Mayday mayday mayday").

The "mayday" procedure word was conceived as a distress call in the early 1920s by Frederick Stanley Mockford, officer in charge of radio at Croydon Airport, England. He had been asked to think of a word that would indicate distress and would easily be understood by all pilots and ground staff in an emergency. Since much of the air traffic at the time was between Croydon and Le Bourget Airport in Paris, he proposed the term "mayday", the phonetic equivalent of the French m'aidez ("help me") or m'aider (a short form of venez m'aider, "come [and] help me"). The term is unrelated to the holiday May Day. Following tests, the new procedure word was introduced for cross Channel flights in February 1923. The previous distress call had been the Morse code signal SOS, but this was not considered suitable for voice communication, "[o]wing to the difficulty of distinguishing the letter 'S' by telephone".

"Pan pan" (from the French: panne, 'a breakdown') indicates an urgent situation, such as a mechanical failure or a medical problem, of a lower order than a "grave and imminent threat requiring immediate assistance". The suffix "medico" originally was to be added by vessels in British waters to indicate a medical problem ("pan pan medico", repeated three times), or by aircraft declaring a non life threatening medical emergency of a passenger in flight, or those operating as protected medical transport in accordance with the Geneva Conventions. "Pan pan medico" is no longer in official use.

Sometimes the phrase "declaring emergency" is used in aviation, as an alternative to calling "mayday". For example, in 1998 Swissair Flight 111 radioed "Swissair one eleven heavy is declaring emergency" after their situation had worsened, upgrading from the "pan pan" which was declared earlier. However, the International Civil Aviation Organization recommends the use of the standard "pan pan" and "mayday" calls instead of "declaring an emergency". Cases of pilots using phrases other than "pan pan" and "mayday" have caused confusion and errors in aircraft handling.

"Seelonce mayday" (using an approximation of the French pronunciation of silence) is a demand that the channel only be used by the vessel/s and authorities involved with the distress. The channel may not be used for normal working traffic until "seelonce feenee" is broadcast. "Seelonce mayday" and "seelonce feenee" may only be sent by the controlling station in charge of the distress. The expression "stop transmitting – mayday" is an aeronautical equivalent of "seelonce mayday". "Seelonce distress" and "prudonce" are no longer in use since ITU WRC 07. The format for a "seelonce mayday" is MAYDAY, All Stations x3 or [Interfering station] x3, this is [controlling station], SEELONCE MAYDAY. "Seelonce feenee" (from French silence fini, 'silence finished') means that the emergency situation has been concluded and the channel may now be used normally. "Distress traffic ended" is the aeronautical equivalent of "seelonce feenee". The format for the "seelonce feenee" is MAYDAY, All stations x3, this is [controlling station] x3, date and time in UTC, distressed vessels MMSI number, distressed vessels name, distressed vessels call sign, SEELONCE FEENEE.