International maritime signal flags

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"Signal flag" redirects here. For other communication systems using flags, see flag signals.
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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.

Contents

[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 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

[edit] References

  1. ^ International Marine Signal Flags
  2. ^ AB Nordbok. "The Lore of Ships", page 138. New York: Crescent Books, 1975.

[edit] External links

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