Distress signal
Encyclopedia
A distress signal is an internationally recognized means for obtaining help
. Distress signals take the form of or are commonly made by using radio
signals, displaying a visually detected item or illumination, or making an audible sound, 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
.
In order for distress signalling to be the most effective, two parameters must be communicated:
For example, a single aerial flare alerts observers to the existence of a vessel in distress somewhere in the general direction of the flare sighting on the horizon but extinguishes within one minute or less. A hand held flare burns for 3 minutes and can be used to localize or pinpoint more precisely the exact location or position of the party in trouble. An EPIRB both notifies or alerts authorities and at the same time provides position indication information.
and in the International Code of Signals
. Mayday signals must only be used where there is grave and imminent danger to life. Otherwise, urgent signals such as pan-pan
can be sent. Most jurisdictions have large penalties for false, unwarranted or prank distress signals.
Distress can be indicated by any of the following officially sanctioned methods:
In addition, a distress can be signaled using automated radio signals such as a Search and Rescue Transponder (SART) which responds to 9GHz radar signal, or a Emergency Position-Indicating Radio Beacon (EPIRB) which operates in the 406 MHz radio frequency. EPIRB signals are received and processed by a constellation of satellites known as COSPAS-SARSAT
.
A GPIRB is an EPIRB that is equipped with a global positioning system (GPS) sensor which enables the distress signal to incorporate the latitude and longitude position of the party in distress.
A DSC radio distress signal can include the position if the lat/long are manually keyed into the radio or if a GPS-derived position is passed electronically directly into the radio.
A Mayday message consists of the word "mayday" spoken three times in succession, which is the distress signal, followed by the distress message, which should include:
In North America, marine search and rescue agencies in Canada and the United States also recognize certain other distress signals:
A floating man-overboard pole or dan buoy can be used to indicate that a person is in distress in the water and is ordinarily equipped with a yellow and red flag (international code of signals flag "O") and a flashing lamp or strobe light.
When none of the above-described officially-sanctioned signals are available, attention for assistance can be attracted by anything that appears unusual or out of the ordinary, such as a jib sail
hoisted upside down.
During daylight hours when the sun is visible, a heliograph
mirror can be used to flash bright, intense sunlight. Battery-powered laser lights the size of small flashlights (electric torches) are available for use in emergency signalling.
s were commonly used as distress signals. However, some countries' flags are difficult (e.g. Spain
, South Korea
, the UK
) or impossible (e.g. Japan
) to determine whether they are inverted. Other countries have flags that are inverses of each other: the Polish
flag is white on the top half and red on the bottom, while Indonesia
's is just the opposite--which would again make it difficult to determine if the flag is being flown upside-down as a distress signal.
If a flag is available, distress may be indicated by tying a knot in it and then flying it upside-down, making it into a wheft.
Expired flares should not be set off, as this indicates distress. Rather, most port authorities offer disposal facilities for expired distress pyrotechnics. In some areas special training events are organised, where the flares can be used safely.
for voice distress alerting 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.
The COSPAS/SARSAT signal can be transmitted by an Electronic Locator Transmitter or ELT, which is similar to a marine EPIRB on the 406 MHz radio frequency. (Marine EPIRBS are constructed so as to float while aviation an ELT is constructed so as to be activated by a sharp deceleration and is sometimes referred to as a Crash Position Indicator/CPI).
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.
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.
In practice either signal pattern is likely to be recognised in most popular mountainous areas as nearby climbing teams are likely to include Europeans or North Americans.
To communicate with a helicopter in sight, raise both arms (forming the letter Y) to indicate "Yes" or "I need help," or 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.
, trekkers, mountaineer
s and other ground-based remote adventure seekers and personnel working in isolated backcountry areas using a small, portable Personal Locator Beacon or PLB.
Helpfulness
In social psychology, the everyday concept of helpfulness is really technically defined as the property of providing useful assistance, and friendliness evidenced by a kindly and helpful disposition [syn: kindliness]....
. Distress signals take the form of or are commonly made by using radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
signals, displaying a visually detected item or illumination, or making an audible sound, from a distance.
A distress signal indicates that a person or group of people, ship
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...
, aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
, 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
International law
Public international law concerns the structure and conduct of sovereign states; analogous entities, such as the Holy See; and intergovernmental organizations. To a lesser degree, international law also may affect multinational corporations and individuals, an impact increasingly evolving beyond...
.
In order for distress signalling to be the most effective, two parameters must be communicated:
- Alert or notification of a distressEmergencyAn emergency is a situation that poses an immediate risk to health, life, property or environment. Most emergencies require urgent intervention to prevent a worsening of the situation, although in some situations, mitigation may not be possible and agencies may only be able to offer palliative...
in progress - Position or location (or localization or pinpointing) of the party in distress.
For example, a single aerial flare alerts observers to the existence of a vessel in distress somewhere in the general direction of the flare sighting on the horizon but extinguishes within one minute or less. A hand held flare burns for 3 minutes and can be used to localize or pinpoint more precisely the exact location or position of the party in trouble. An EPIRB both notifies or alerts authorities and at the same time provides position indication information.
Maritime distress signals
Distress signals at sea are defined in the International Regulations for Preventing Collisions at SeaInternational Regulations for Preventing Collisions at Sea
The International Regulations for Preventing Collisions at Sea 1972 are published by the International Maritime Organization , and set out, inter alia, the "rules of the road" or navigation rules to be followed by ships and other vessels at sea in order to prevent collisions between two or more...
and in the International Code of Signals
International Code of Signals
The International Code of Signals is an international system of signals and codes for use by vessels to communicate important messages regarding safety of navigation and related matters. Signals can be sent by flaghoist, signal lamp , flag semaphore, radiotelegraphy, and radiotelephony...
. Mayday signals must only be used where there is grave and imminent danger to life. Otherwise, urgent signals such as pan-pan
Pan-pan
In radiotelephone communications, a call of three repetitions of pan-pan is used to signify that there is an urgency on board a boat, ship, aircraft or other vehicle but that, for the time being at least, there is no immediate danger to anyone's life or to the vessel itself. This is referred to as...
can be sent. Most jurisdictions have large penalties for false, unwarranted or prank distress signals.
Distress can be indicated by any of the following officially sanctioned methods:
- Transmitting a spoken voice Pan-panPan-panIn radiotelephone communications, a call of three repetitions of pan-pan is used to signify that there is an urgency on board a boat, ship, aircraft or other vehicle but that, for the time being at least, there is no immediate danger to anyone's life or to the vessel itself. This is referred to as...
, or a MaydayMayday (distress signal)Mayday is an emergency procedure word used internationally as a distress signal in voice procedure radio communications. It derives from the French venez m'aider, meaning "come help me"....
message by radio over very high frequencyVery high frequencyVery high frequency is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency , and the next higher frequencies are known as Ultra high frequency...
(shorter range VHF) channel 16Marine VHF radioMarine VHF radio is installed on all large ships and most seagoing small craft. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbours, locks, bridges and marinas, and operates in the VHF frequency range, between 156 to 174 MHz...
(156.8 MHzHertzThe hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
) and/or high frequencyHigh frequencyHigh frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...
(longer range HF) on 2182 kHz2182 kHzThe radio frequency of 2182 kHz is the international calling and distress frequency for maritime radiotelephone communications on the marine MF bands.- Transmission modes :... - Transmitting a digital distress signal by activating (or pressing) the distress button (or key) on a marine radio equipped with Digital Selective Calling (DSC) over the VHF (channel 70) and/or HF frequency bands.
- Transmitting a digital distress signal by activating (or pressing) the distress button (or key) on a Inmarsat-CInmarsat-CInmarsat-C is a two-way, packet data service operated by the telecommunications company Inmarsat. The service is approved for use under the Global Maritime Distress and Safety System , meets the requirements for Ship Security Alert Systems defined by the International Maritime Organization and is...
satellite internet device - Sending the Morse codeMorse codeMorse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...
group SOSSOSSOS is the commonly used description for the international Morse code distress signal...
by light flashes or sounds - Burning a red flareFlare (pyrotechnic)A flare, also sometimes called a fusee, is a type of pyrotechnic that produces a brilliant light or intense heat without an explosion. Flares are used for signalling, illumination, or defensive countermeasures in civilian and military applications...
(either hand-held or aerial parachute flare) - Emitting orange smoke from a canister
- Showing flames on the vessel (as from a burning tar barrel, oil barrel, etc.)
- Raising and lowering slowly and repeatedly both arms outstretched to each side
- Making a continuous sound with any fog-signalling apparatusFoghornA foghorn or fog signal or fog bell is a device that uses sound to warn vehicles of hazards or boats of the presence of other vehicles in foggy conditions. The term is most often used in relation to marine transport...
- Firing a gun or other explosive signal at intervals of about a minute
- Flying the international maritime signal flagsInternational maritime signal flagsThe system of international maritime signal flags is one system of flag signals representing individual letters of the alphabet in signals to or from ships...
NC
- Displaying a visual signal consisting of a square flag having above or below it a ball or anything resembling a ball (round or circular in appearance)
- Launching distress rockets
In addition, a distress can be signaled using automated radio signals such as a Search and Rescue Transponder (SART) which responds to 9GHz radar signal, or a Emergency Position-Indicating Radio Beacon (EPIRB) which operates in the 406 MHz radio frequency. EPIRB signals are received and processed by a constellation of satellites known as COSPAS-SARSAT
Cospas-Sarsat
Cospas-Sarsat is an international satellite-based search and rescue distress alert detection and information distribution system, established by Canada, France, the United States, and the former Soviet Union in 1979. It is best known as the system that detects and locates emergency beacons...
.
A GPIRB is an EPIRB that is equipped with a global positioning system (GPS) sensor which enables the distress signal to incorporate the latitude and longitude position of the party in distress.
A DSC radio distress signal can include the position if the lat/long are manually keyed into the radio or if a GPS-derived position is passed electronically directly into the radio.
A Mayday message consists of the word "mayday" spoken three times in succession, which is the distress signal, followed by the distress message, which should include:
- Name of the vessel or ship in distress
- Her position (actual, last known or estimated expressed in lat./long. or in distance/bearing from a specific location)
- Nature of the vessel distress condition or situation (e.g. on fire, sinking, aground, taking on water, adrift in hazardous waters)
- Number of persons at risk or to be rescued; grave injuries
- Type of assistance needed or being sought
- Any other details to facilitate resolution of the emergency such as actions being taken (e.g. abandoning ship, pumping flood water), estimated available time remaining afloat
In North America, marine search and rescue agencies in Canada and the United States also recognize certain other distress signals:
- Sea marker dye
- White high intensity strobe light flashing at 60 times per minute
A floating man-overboard pole or dan buoy can be used to indicate that a person is in distress in the water and is ordinarily equipped with a yellow and red flag (international code of signals flag "O") and a flashing lamp or strobe light.
Unusual or extraordinary appearance
Jib
A jib is a triangular staysail set ahead of the foremast of a sailing vessel. Its tack is fixed to the bowsprit, to the bow, or to the deck between the bowsprit and the foremost mast...
hoisted upside down.
During daylight hours when the sun is visible, a heliograph
Heliograph
A heliograph is a wireless solar telegraph that signals by flashes of sunlight reflected by a mirror. The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shutter...
mirror can be used to flash bright, intense sunlight. Battery-powered laser lights the size of small flashlights (electric torches) are available for use in emergency signalling.
Flags
For hundreds of years inverted national flagNational flag
A national flag is a flag that symbolizes a country. The flag is flown by the government, but usually can also be flown by citizens of the country.Both public and private buildings such as schools and courthouses may fly the national flag...
s were commonly used as distress signals. However, some countries' flags are difficult (e.g. Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
, South Korea
South Korea
The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...
, the UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
) or impossible (e.g. Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
) to determine whether they are inverted. Other countries have flags that are inverses of each other: the Polish
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
flag is white on the top half and red on the bottom, while Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
's is just the opposite--which would again make it difficult to determine if the flag is being flown upside-down as a distress signal.
If a flag is available, distress may be indicated by tying a knot in it and then flying it upside-down, making it into a wheft.
Device loss and disposal
To avoid pointless searches some devices must be reported when lost. This particularly applies to EPIRBs, life buoys, rafts and devices marked with the vessel's name and port.Expired flares should not be set off, as this indicates distress. Rather, most port authorities offer disposal facilities for expired distress pyrotechnics. In some areas special training events are organised, where the flares can be used safely.
Aviation distress signals
The civilian aircraft emergency frequencyAircraft emergency frequency
The aircraft emergency frequency is a frequency used on the aircraft radio band reserved for emergency communications for aircraft in distress. The frequencies are 121.5 MHz for civilian, also known as International Air Distress and 243.0 MHz for military use, also known as Military Air...
for voice distress alerting is 121.5 MHz. Military aircraft use 243 MHz (which is a harmonic
Harmonic
A harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency, i.e. if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f, . . . etc. The harmonics have the property that they are all periodic at the fundamental...
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.
The COSPAS/SARSAT signal can be transmitted by an Electronic Locator Transmitter or ELT, which is similar to a marine EPIRB on the 406 MHz radio frequency. (Marine EPIRBS are constructed so as to float while aviation an ELT is constructed so as to be activated by a sharp deceleration and is sometimes referred to as a Crash Position Indicator/CPI).
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.
Mountain distress signals
The recognised mountain distress signals are based on groups of three, or six in the UK and the European Alps. 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
Alps
The Alps is one of the great mountain range systems of Europe, stretching from Austria and Slovenia in the east through Italy, Switzerland, Liechtenstein and Germany to France in the west....
, the recommended way to signal distress is the Alpine distress signal
Alpine distress signal
The Alpine distress signal is a distress signal in the case of mountain emergency, an emergency in alpine areas. There are also special emergency call numbers, for use with the telephone service by which the emergency services can be contacted....
: 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
Heliograph
A heliograph is a wireless solar telegraph that signals by flashes of sunlight reflected by a mirror. The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shutter...
) or audible (shouts, whistles, etc.). The rescuers acknowledge with three signals per minute.
In practice either signal pattern is likely to be recognised in most popular mountainous areas as nearby climbing teams are likely to include Europeans or North Americans.
To communicate with a helicopter in sight, raise both arms (forming the letter Y) to indicate "Yes" or "I need help," or 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.
Ground distress beacons
The COSPAS-SARSAT 406 MHz radio frequency distress signal can be transmitted by hikers, backpackersBackpacking (wilderness)
Backpacking combines the activities of hiking and camping for an overnight stay in backcountry wilderness...
, trekkers, mountaineer
Mountaineer
-Sports:*Mountaineering, the sport, hobby or profession of walking, hiking, trekking and climbing up mountains, also known as alpinism-University athletic teams and mascots:*Appalachian State Mountaineers, the athletic teams of Appalachian State University...
s and other ground-based remote adventure seekers and personnel working in isolated backcountry areas using a small, portable Personal Locator Beacon or PLB.
See also
- 500 kHz
- COSPAS-SARSATCospas-SarsatCospas-Sarsat is an international satellite-based search and rescue distress alert detection and information distribution system, established by Canada, France, the United States, and the former Soviet Union in 1979. It is best known as the system that detects and locates emergency beacons...
Search And Rescue Satellite Aided Tracking - Search and Rescue Transponder
- Digital Selective CallingDigital Selective CallingDigital Selective Calling or DSC is a standard for sending pre-defined digital messages via the medium frequency , high frequency and very high frequency maritime radio systems. It is a core part of the Global Maritime Distress Safety System .-Workings:DSC was developed to replace a call in older...
DSC - Emergency Alert SystemEmergency Alert SystemThe Emergency Alert System is a national warning system in the United States put into place on January 1, 1997, when it superseded the Emergency Broadcast System , which itself had superseded the CONELRAD System...
- Emergency telephone numberEmergency telephone numberMany countries' public telephone networks have a single emergency telephone number, sometimes known as the universal emergency telephone number or occasionally the emergency services number, that allows a caller to contact local emergency services for assistance. The emergency telephone number may...
- Global Maritime Distress Safety SystemGlobal Maritime Distress Safety SystemThe Global Maritime Distress and Safety System is an internationally agreed-upon set of safety procedures, types of equipment, and communication protocols used to increase safety and make it easier to rescue distressed ships, boats and aircraft....
GMDSS - International distress frequencyInternational distress frequencySince early in the 20th century, the radio frequency of 500 kilohertz has been an international calling and distress frequency for Morse code maritime communication. The unit kilohertz was not introduced until 1960...
- Maritime mobile amateur radioMaritime mobile amateur radioMost countries' amateur radio licences allow licensed operators to install and use radio transmission equipment while at sea. Such operation is known as maritime mobile amateur radio...
- Mountain rescueMountain rescueMountain rescue refers to search and rescue activities that occur in a mountainous environment, although the term is sometimes also used to apply to search and rescue in other wilderness environments. The difficult and remote nature of the terrain in which mountain rescue often occurs has resulted...
- Vessel emergency codesVessel emergency codesIn addition to distress signals like Mayday and pan-pan, most vessels, especially passenger ships, use some emergency signals to internally alert the crew on board, and in some cases also the passengers. These can be in form of blasts on alarm bells, sounding the ship's whistle or code names paged...