International maritime signal flags

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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 one system of flag signals representing individual letters of the alphabet in signals to or from ships. It is a component of the International Code of Signals (ICS).[1]

Overview[edit]

Signal flag storage rack on board USS North Carolina (BB-55)
Signal flag rack on board the HMNZS Te Kaha - F77

There are various methods by which the flags can be used as signals:

  • each flag spells 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 and (more importantly) to warn other vessels to keep clear to avoid chopping up the diver(s) with their propellers.
  • 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.

During the allied occupations of Axis countries after World War II, use and display of those nations' national flags were banned.[citation needed] In order to comply with the international legal requirement that a ship identify its registry by displaying the appropriate national ensign, swallow-tailed versions of the C, D, and E signal flags were designated as, respectively, provisional German, Okinawan, and Japanese civil ensigns. Being swallowtails, they are commonly referred to as the "C-Pennant" (C-Doppelstander), "D-Pennant", and "E-Pennant".[citation needed]

Letter flags (with ICS meaning)[edit]

Letter/
Phonetic
Name
Flag/ ICS Meaning as Single Flag Meaning when used with Numeric Complements
A
Alfa
ICS Alpha.svg "I have a diver down; keep well clear at slow speed." Azimuth or bearing
B
Bravo
ICS Bravo.svg "I am taking in or discharging or carrying dangerous goods." (Originally used by the Royal Navy specifically for military explosives.)
C
Charlie
ICS Charlie.svg "Affirmative."[a][b] Course in degrees magnetic
D
Delta
ICS Delta.svg "Keep clear of me; I am maneuvering with difficulty." Date
E
Echo
ICS Echo.svg "I am altering my course to starboard."[b]
F
Foxtrot
ICS Foxtrot.svg "I am disabled; communicate with me."
G
Golf
ICS Golf.svg "I require a pilot."
By fishing vessels near fishing grounds: "I am hauling nets."
Longitude (The first 2 or 3 digits denote minutes; the last 2 denote degrees.)
H
Hotel
ICS Hotel.svg "I have a pilot on board."
I
India
ICS India.svg "I am altering my course to port."[b]
J
Juliet
ICS Juliet.svg "I am on fire and have dangerous cargo on board: keep well clear of me."
or
"I am leaking dangerous cargo."
K
Kilo
ICS Kilo.svg "I wish to communicate with you." "I wish to communicate with you by...":
1) Morse signaling by hand-flags or arms;
2) Loud hailer (megaphone);
3) Morse signaling lamp;
4) Sound signals.
L
Lima
ICS Lima.svg In harbour: "The ship is quarantined."
At sea: "You should stop your vessel instantly."
Latitude (The first 2 digits denote minutes; the last 2 denote degrees.)
M
Mike
ICS Mike.svg "My vessel is stopped and making no way through the water."[b]
N
November
ICS November.svg "Negative."[a]
O
Oscar
ICS Oscar.svg "Man overboard."[b] (often attached to the man overboard pole on boats).
With a sinister hoist, the semaphore flag.
P
Papa
ICS Papa.svg 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
ICS Quebec.svg "My vessel is 'healthy' and I request free pratique."
R
Romeo
ICS Romeo.svg (No ICS meaning as single flag) Distance (range) in nautical miles.
S
Sierra
ICS Sierra.svg "I am operating astern propulsion."[b] Speed (velocity) in knots
T
Tango
ICS Tango.svg "Keep clear of me; I am engaged in pair trawling." Local time. (The first 2 digits denote hours; the last 2 denote minutes.)
U
Uniform
ICS Uniform.svg "You are running into danger."
V
Victor
ICS Victor.svg "I require assistance." Speed in kilometres per hour.
W
Whiskey
ICS Whiskey.svg "I require medical assistance."
X
Xray
ICS X-ray.svg "Stop carrying out your intentions and watch for my signals."
Y
Yankee
ICS Yankee.svg "I am dragging my anchor."
Z
Zulu
ICS Zulu.svg "I require a tug."
By fishing vessels near fishing grounds: "I am shooting nets."[c]
Time (UTC). (The first 2 digits denote hours; the last 2 denote minutes.)
Notes
  1. ^ a b N and C together (No and Yes) is used as a distress signal.
  2. ^ a b c d e f Also signallable on a ship's whistle using Morse code. See International Code of Signals.
  3. ^ The Z flag was also famously hoisted by Adm. Heihachiro Togo at the 1905 Battle of Tsushima as the Japanese fleet prepared to engage the Russian fleet. In Japanese coding at the time, the flag meant, "The Empire's fate depends on the result of this battle, let every man do his utmost duty."

Additional meanings[edit]

Flag NATO Nations Naval Meaning - Replenishment at Sea
Romeo Romeo at Dip: Romeo flag is located 34 way up toward the point of the hoist. On the control ship, it means, "I am steady on course and speed and am prepared to receive you alongside on side indicated." On the approaching ship, it means, "I am ready to come alongside."
Romeo Close Up: Romeo flag is at the top of the hoist, touching the point of the hoist or as high as it will go. On the control ship, it means, "I am ready for your approach.: On the approach ship, it means, "I am commencing my approach."
Romeo Hauled Down: This means the first messenger is in hand for controlling and receiving ship.
Bravo Bravo at Dip: Bravo flag is located 34 way up toward the point of the hoist. On the delivery ship, it means, "I have temporarily stopped supplying." On the receiving ship, it means, "I have temporarily stopped receiving."
Bravo Close Up: Bravo flag is at the top of the hoist, touching the point of the hoist or as high as it will go. On both ships, it means fuel or explosives are being transferred.
Bravo Hauled Down: On both ships, it means delivery is complete.

Number Flags[edit]

Number NATO Flag ICS Flag
0
Zero
ICS Zero.svg ICS Pennant Zero.svg
1
One
ICS One.svg ICS Pennant One.svg
2
Two
ICS Two.svg ICS Pennant Two.svg
3
Three
ICS Three.svg ICS Pennant Three.svg
4
Four
ICS Four.svg ICS Pennant Four.svg
5
Five
ICS Five.svg ICS Pennant Five.svg
6
Six
ICS Six.svg ICS Pennant Six.svg
7
Seven
ICS Seven.svg ICS Pennant Seven.svg
8
Eight
ICS Eight.svg ICS Pennant Eight.svg
9
Niner
ICS Niner.svg ICS Pennant Niner.svg

Substitute[edit]

Substitute or repeater flags allow messages with duplicate characters to be signaled without the need for multiple sets of flags.

The four NATO substitute flags are as follows:

ICS Repeat One.svg ICS Repeat Two.svg ICS Repeat Three.svg ICS Repeat Four.svg
First substitute Second substitute Third substitute Fourth substitute

The International Code of Signals includes only the first three of these substitute flags. To illustrate their use, here are some messages and the way they would be encoded:

"N" ICS November.svg
"O" ICS Oscar.svg
"NO" ICS November.svg ICS Oscar.svg
"NON" ICS November.svg ICS Oscar.svg ICS Repeat One.svg
"NOO" ICS November.svg ICS Oscar.svg ICS Repeat Two.svg
"NOON" ICS November.svg ICS Oscar.svg ICS Repeat Two.svg ICS Repeat One.svg
"NONO" ICS November.svg ICS Oscar.svg ICS Repeat One.svg ICS Repeat Two.svg
"NONON" ICS November.svg ICS Oscar.svg ICS Repeat One.svg ICS Repeat Two.svg ICS Repeat Three.svg
"NONNN" ICS November.svg ICS Oscar.svg ICS Repeat One.svg ICS Repeat Three.svg ICS Repeat Four.svg

See also[edit]

References[edit]

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

External links[edit]