Mayday (distress signal)

Mayday is an emergency code word used internationally as a distress signal in voice procedure radio communications. It derives from the French venez m'aider, meaning 'come to my aid'/"come [to] help me." It is used to signal a life-threatening emergency by many groups, such as police forces, pilots, the fire brigade, and transportation organizations. The call is always given three times in a row ("Mayday Mayday Mayday") to prevent mistaking it for some similar-sounding phrase under noisy conditions, and to distinguish an actual mayday call from a message about a mayday call. ''

Mayday calls
A Mayday situation is one in which a vessel, aircraft, vehicle, or person is in grave and imminent danger and requires immediate assistance. Examples of "grave and imminent danger" in which a mayday call would be appropriate include fire, explosion or sinking.

Mayday calls can be made on any frequency, and when a mayday call is made no other radio traffic is permitted except to assist in the emergency. A mayday call may only be made when life or craft is in imminent danger of death or destruction.

'Mayday' calls are made by radio, such as a ship or aircraft's VHF radio. Although a Mayday call will be understood regardless of the radio frequency on which it is broadcast, first-line response organisations, such as the coastguard and air traffic control, monitor designated channels: marine MF on 2182 kHz; marine VHF radio channel 16 (156.8 MHz); and airband frequencies of 121.5 MHz and 243.0 MHz. A Mayday call is roughly equivalent of a morse code SOS, or a telephone call to the emergency services.



When they receive a Mayday call the coastguard may launch lifeboats and helicopters to assist the ship that is in trouble. Other ships that are nearby may divert course to assist the vessel broadcasting the Mayday.

Making a hoax Mayday call is a criminal act in many countries because of the danger to the rescuers' lives that a search-and-rescue operation can create, as well as the very high costs of such rescue efforts. For example, making a false distress call in the U.S. is a federal crime carrying sanctions of up to six years imprisonment, and a fine of $250,000.

The coastguard can be contacted in situations that are not emergencies (out of fuel, etc.) by calling 'Coastguard, Coastguard, Coastguard, this is (name of vessel)', on VHF channel 16. In many countries special training and a licence are required to use a mobile radio transmitter legally, although anyone may legally use one to summon help in a real emergency.

The recommended distress call format includes the word MAYDAY repeated three times, followed by the vessel's name or callsign, also repeated three times, then MAYDAY and the name or callsign again. Vital information, including the position, nature of the emergency, assistance required and the number of people on board, should follow. A typical message might be:


 * "MAYDAY, MAYDAY, MAYDAY, this is NONSUCH, NONSUCH, NONSUCH. MAYDAY, NONSUCH. Position 54 25 North 016 33 West. My boat is on fire and sinking. I require immediate assistance. 4 people on board, are taking a lifeboat. OVER."

If a Mayday call cannot be sent because a radio is not available a variety of other distress signals and calls for help can be used. A Mayday can be sent on behalf of one vessel by another, using a convention called a Mayday Relay (see below).

History
The Mayday callsign was originated in 1923 by Frederick Stanley Mockford (1897-1962). A senior radio officer at Croydon Airport in London, Mockford was 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 traffic at the time was between Croydon and Le Bourget Airport in Paris, he proposed the word "Mayday" from the French m'aider.

The French "m'aider" translates as "to help me".

Other urgent calls
Mayday is one of a number of words used internationally as radio code words to signal important information. Senders of urgency calls are entitled to interrupt messages of lower priority. As with Mayday the use of these terms without proper cause could render the user liable to civil and/or criminal charges.

Each of these urgency calls is usually repeated three times (eg "Pan-pan, Pan-pan, Pan-pan").

Mayday relay

 * A Mayday relay call is made by one vessel on behalf of a different vessel which is in distress. If a vessel makes a Mayday call and it is not acknowledged by the coastguard after a single repetition and a two-minute wait a vessel receiving the Mayday call should attempt to contact the coastguard on behalf of the Mayday vessel by broadcasting a Mayday Relay on their behalf.


 * A Mayday Relay call should use the callsign of the transmitting vessel but give the name and position of the Mayday vessel.


 * Mayday Relay calls can be used to summon help for a vessel which is either too far offshore to contact the coastguard directly or without radio capabilities (though most vessels above a certain size or crew complement are legally required to carry two-way radio equipment, such equipment can potentially be damaged or destroyed).

Pan-pan

 * Pan-pan (from the French: panne - a breakdown) indicates an urgent situation of a lower order than a "grave and imminent threat requiring immediate assistance", such as a mechanical breakdown or a medical problem. The suffix medico used to be added by vessels in UK waters to indicate a medical problem (Pan-Pan medico, repeated three times), but has never applied in aviation.

Securite

 * Securite (, from French sécurité) indicates a message about safety, such as a hazard to navigation or weather information.

Silence
The following calls may be made only by the vessel in distress or the responding authority:


 * Seelonce Mayday or Seelonce Distress means that the channel may only be used by the vessel in distress and the coastguard (and any other vessels they ask for assistance in handling the emergency). The channel may not be used for normal working traffic until 'seelonce feenee' is broadcast.


 * The expressions Stop Transmitting - Distress and Stop Transmitting - Mayday are the aeronautical equivalents of Seelonce Mayday.


 * Seelonce Feenee (French: silence fini - silence finished) means that the emergency situation has been concluded and the channel may now be used normally. The word prudonce (prudence caution) can also be used to allow restricted working to resume on that channel.


 * Distress Traffic Ended is the aeronautical equivalent of seelonce feenee.