Distress signal

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A distress signal is an internationally recognized means of obtaining help by using a radio, displaying a visual object or making noise from a distance.

A distress signal indicates that a ship, aircraft, or other vehicle is threatened by grave and imminent danger and requests immediate assistance. Use of distress signals in other circumstances may be against local or international law.


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Maritime Distress Signals

Distress Signals at sea are defined in the International Regulations for Preventing Collisions at Sea and in the International Code of Signals. They must only be used where there is grave and imminent danger to life. Other urgent signals should be sent using a pan-pan message.

Distress can be signalled by any of the following means:

  • sending a Mayday message by radio - VHF channel 16 (156.8 MHz) or HF on 2182 kHz
  • sending the Morse code group SOS
  • using red flares (either hand-held or parachute flares)
  • emitting orange smoke from a canister
  • showing flames on the vessel (as from a burning tar barrel, oil barrel, etc)
  • slowly and repeatedly raising and lowering arms outstretched to each side
  • a continuous sounding with any fog-signalling apparatus
  • a gun or other explosive signal fired at intervals of about a minute
  • the International maritime signal flags NC
  • a signal consisting of a square flag having above or below it a ball or anything resembling a ball

In addition, distress can be signalled using automated radio signals, eg from an EPIRB.

If none of the above are available, attention can be drawn by anything unusual - eg a jib sail hoisted upside down.


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Aviation Distress Signals

The civilian aircraft emergency calling frequency is 121.5 MHz. Military aircraft use 243 MHz. Aircraft can also signal an emergency by setting one of several special transponder codes, such as 7700.

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Mountain Distress Signals

The recognised mountain distress signal is six blasts on a whistle, or six flashes of a light, in succession followed by a one minute pause and repeated until you get a response (three blasts or flashes is the appropriate response).

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See also

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External links