Mayday is an international radio call for help, which usually meets the highest life-threatening emergency call in navigation and aviation. The pilot needs to repeat "Mayday" three times, followed by information such as call signal, danger characteristics and pilot's intention. Once someone hears the call sign of "Mayday", it means something bad has happened. For example, a ship is sinking, being robbed, having a fire or exploding; Or because of bird strike, mechanical failure, sudden loss of pressure, engine failure and other reasons, the aircraft is in an emergency situation that is enough to expand and endanger flight.

The allusions are as follows:

1923, when the Englishman Frederick Stanley Mokford (1897- 1962) worked as a senior radio correspondent at Croydon Airport, he requested that all pilots and ground crew should be used as emergency distress signals.

At that time, most of the flights at the airport departed from Paris-Lebourt Day Airport, so the English word "Mayday" similar to the French word "m'aider" was chosen. When signaling, you must shout "help, help, help" three times in a row. "Mayday" has the characteristics of concise and vivid English pronunciation, which can effectively avoid confusion or interference in noisy environment.

Extended data

Before the Mayday call sign appeared, SOS was a universal rescue Morse code. 1927 Washington international radiotelegraph convention clearly stipulates that "Mayday" is a distress signal. At present, the emergency frequency of aircraft is generally maintained at 12 1.5MHz (civil) and 243.0MHz (military). The transmission frequency of the early emergency positioning transmitter (ELT) was 406 MHz.

For example, in Britain, the frequency of 12 1.5MHz is determined by the RAF's distress and transfer D&(D&: D) nationwide monitoring. If the plane "disappears" or "the position cannot be determined", the center personnel can use triangulation to determine the exact position of the pilot.

In addition, the lower-level emergency rescue signal is "general", indicating that a secondary emergency has occurred. You also need to call three times "Panpan, Panpan, Panpan".