International maritime signal flags

The set of signal flags on the bridge of the Liberty ship SS Jeremiah O'Brien

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^[2]; 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.

[edit] Letter flags (with ICS meaning)

A (Alfa) "I have a diver down; keep well clear at slow speed." With three numerals, azimuth or bearing.	B (Bravo) "I am taking in, or discharging, or carrying dangerous goods." (Originally used by the Royal Navy specifically for military explosives.)	C (Charlie) "Affirmative." * ** With three numerals, course in degrees magnetic.	D (Delta) "Keep clear of me; I am manoeuvering with difficulty." With two, four, or six numerals, date.
E (Echo) "I am altering my course to starboard."** Crew at meals	F (Foxtrot) "I am disabled; communicate with me." (When flown from an aircraft carrier; "Warning; flight operations underway.")	G (Golf) "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 (Hotel) "I have a pilot on board."
I (India) "I am altering my course to port."**	J (Juliet) "I am on fire and have dangerous cargo on board: keep well clear of me," or "I am leaking dangerous cargo."	K (Kilo) "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 (Lima) In harbour: "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 (Mike) "My vessel is stopped and making no way through the water."**	N (November) "Negative."*	O (Oscar) "Man overboard."** (often attached to the man overboard pole on boats). With a sinister hoist, the semaphore flag.	P (Papa) The Blue Peter. In harbour: 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 (Quebec) "My vessel is 'healthy' and I request free pratique."	R (Romeo) "The way is off my ship." With one or more numerals, distance (range) in nautical miles.	S (Sierra) "I am operating astern propulsion." ** With one or more numerals, speed in knots.	T (Tango) "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 (Uniform) "You are running into danger."	V (Victor) "I require assistance." With one or more numerals, speed in kilometres per hour.	W (Whiskey) "I require medical assistance."	X (Xray) "Stop carrying out your intentions and watch for my signals."
Y (Yankee) "I am dragging my anchor."	Z (Zulu) "I require a tug." When made by fishing vessels operating in close proximity on the fishing grounds it means: "I am shooting nets." With one or more numerals, time (UTC). (The first two denote hours and the rest minutes.)

* ^ N and C together (No and Yes) is used as a distress signal.

** Also signallable on a ship's whistle using Morse code. See International Code of Signals.

[edit] See also

• Character encoding
• Day shapes
• Diver down flag
• England expects that every man will do his duty
• Flag of Germany after World War II (C-Pennant)
• Flag semaphore
• Flag signals
• Heliograph
• International Code of Signals
• List of international common standards
• NATO phonetic alphabet
• Signal lamp
• Substitute flag

[edit] References

[edit] External links

Wikimedia Commons has media related to: International Code of Signals

• John Savard's flag page. Collection of different flag systems.
• Freeware to aid memorizing the flags
• La flag-alfabeto - signal flags used for the Esperanto language - 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.