Distress signal

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"Call for help" redirects here. For the TV show, see Call for Help.

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

A distress signal indicates that a person or group of people, 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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[edit] 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:

In addition, distress can be signalled using automated radio signals, such as from an Emergency Position-Indicating Radio Beacon (EPIRB).

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

[edit] Flags

Inverted national flags are no longer commonly used as distress signals. It is difficult or impossible to determine when the flags of many countries (such as  the United Kingdom or  Argentina or  Italy) are inverted, or the viewer may not be familiar with the flag and may not realise it is not upright. If a national flag is all that is available, distress may be indicated by tying a knot in it, making it into a wheft.[1]

[edit] Aviation distress signals

The civilian aircraft emergency frequency is 121.5 MHz. Military aircraft use 243 MHz (which is a harmonic of 121.5 MHz, and therefore civilian beacons transmit on this frequency as well). Aircraft can also signal an emergency by setting one of several special transponder codes, such as 7700.

A "triangular distress pattern" is a rarely-used flight pattern flown by aircraft in distress but without radio communications. The standard pattern is a series of 120° turns.

[edit] Mountain distress signals

The recognised mountain distress signals are based on groups of three (six in the UK). A distress signal can be 3 fires or piles of rocks in a triangle, three blasts on a whistle, or three flashes of a light, in succession followed by a one minute pause and repeated until a response is received. Three blasts or flashes is the appropriate response.

In the Alps, the recommended way to signal distress is the Alpine distress signal: give six signals within a minute, then pause for a minute, repeating this until rescue arrives. A signal may be anything visual (waving clothes or lights, use of a signal mirror) or audible (shouts, whistles, etc.). The rescuers acknowledge with three signals per minute. To communicate with a helicopter in sight, raise both arms (forming the letter Y) to indicate "Yes" or "I need help" and stretch one arm up and one down (imitating the letter N) for "No" or "I do not need help". If semaphore flags are available, they can possibly be used to communicate with rescuers.

[edit] As a plot device

In works of fiction false distress calls from a ship are a common plot hook, usually used by pirates or other antagonists to lure would-be rescuers into a trap. This is a clichéd device in space-faring science fiction, notably the various incarnations of Star Trek, in which Starfleet vessels (among others) are required by law, and most independent ship captains tend to feel morally obligated, to render any assistance they can to a vessel in distress.

[edit] See also

[edit] References

  1. ^ Flying flags upside down

[edit] External links

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International Morse code
Transmission methods
Notable signals
Other writing systems
in Morse code