Mayday (distress signal)

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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 help me'.[1] It is used to signal a life-threatening emergency by many groups, such as police forces, pilots, firefighters, 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.

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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.

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