The system of international maritime signal flags is a way of representing individual letters of the alphabet in signals to or from ships. It is a component of the International Code of Signals(INTERCO). [1]
There are various methods that the flags can be used as signals:
- each flag spells out an alphabetic message, letter by letter.
- individual flags have specific and standard meanings; for example, diving support vessels raise the "A flag" indicating their inability to move from their current location because they have a diver underwater.
- one or more flags form a code word whose meaning can be looked up in a code book held by both parties. An example is the Popham numeric code used at the Battle of Trafalgar.
- in yacht racing and dinghy racing, flags have other meanings; for example, the P flag is used as the "preparatory" flag to indicate an imminent start, and the S flag means "shortened course" (for more details see Race Signals).
NATO uses the same flags, with a few unique to warships, alone or in short sets to communicate various unclassified messages. The NATO usage generally differs from the International meanings, and therefore warships will fly the Code/Answer flag above the signal to indicate it should be read using the International meaning.
Contents |
Letters
 A
I have a diver down; keep well clear at slow speed. With three numerals, azimuth or bearing. |
 B
I am taking in, or discharging, or carrying dangerous goods. (Originally used by the Royal Navy specifically for military explosives.) |
 C
Affirmative. With three numerals, course in degrees magnetic. |
 D
Keep clear of me; I am maneuvering with difficulty. With two, four, or six numerals, date. |
 E
I am altering my course to starboard. |
 F
I am disabled; communicate with me. |
 G
I require a pilot. When made by fishing vessels operating in close proximity on the fishing grounds it means: "I am hauling nets". With four or five numerals, longitude. (The last two numerals denote minutes and the rest degrees.) |
 H
I have a pilot on board. |
 I
I am altering my course to port. |
 J
I am on fire and have dangerous cargo on board: keep well clear of me, or I am leaking dangerous cargo. |
 K
I wish to communicate with you. With one numeral, I wish to communicate with you by; 1) Morse signalling by hand-flags or arms; 2) Loud hailer (megaphone); 3) Morse signalling lamp; 4) Sound signals. |
 L
In harbor: The ship is under Quarantine.At sea: You should stop your vessel instantly. With four numerals, latitude. (The first two denote degrees and the rest minutes.) |
 M
My vessel is stopped and making no way through the water. |
 N
Negative. |
 O
Man overboard. (often attached to the man overboard pole on boats). With a sinister hoist, the semaphore flag. |
 P
The Blue Peter.In harbor: All persons should report on board as the vessel is about to proceed to sea. At sea: It may be used by fishing vessels to mean: "My nets have come fast upon an obstruction". |
 Q
My vessel is "healthy" and I request free pratique. |
 R
The way is off my ship. With one or more numerals, distance in nautical miles. |
 S
I am operating astern propulsion. With one or more numerals, speed in knots. |
 T
Keep clear of me; I am engaged in pair trawling. With four numerals, local time. (The first two denote hours and the rest minutes.) |
 U
You are running into danger. |
 V
I require assistance. With one or more numerals, speed in kilometres per hour. |
 W
I require medical assistance. |
 X
Stop carrying out your intentions and watch for my signals. |
 Y
I am dragging my anchor. |
* ^ N and C together (No and Yes) is used as a distress signal.
Numbers
| Type of flag | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| Allied flags (outdated) |  |
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| Pennants (modern) |  |
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Other flags
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| Prompt | First substitute | Second substitute | Third substitute | Fourth substitute |
Allied signals |
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| Code/answer (ANS) | Preparative (PREP) | Question (INT) | Negation (NEGAT) | Designation (DESIG) |
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| Course Pennant (CORPEN) | Turn (TURN) | Screen (SCREEN) | Speed (SPEED) | Station (STATION) |
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| Port (PORT) | Starboard (STBD) | Formation (FORM) | Division (DIV) | Squadron (SQUAD) |
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| Group (FLOT) | Subdivision (SUBDIV) | Emergency (EMERG) | ||
See also
- England expects that every man will do his duty
- Flag signals
- NATO phonetic alphabet
- Character encoding
- Flag semaphore
- Aldis lamp
- Heliograph
- Signal lamp
References
(1995) International Code of Signals. International Maritime Organisation.
External links
- Freeware to aid memorizing the flags from The Navy Patuxent Sailing Club
- La flag-alfabeto - signal flags used for the Esperanto language. Description: the flags for the esperanto letters with diacritical marks have the lighter color in the normal flag replaced with light green, which is not used in any normal flag.
- Signalman manual
- brief history of naval signals
