Signal Code Flags

Signal Code Flags

For centuries, admirals have used flags as signals to communicate a single message to other members of a fleet. As tactics began to require more and more signals, a more complex code of signals was needed. In 1738, a French naval officer named Mahé de la Bourdonnais purportedly devised the first numerical flag code, assigning a different flag to each number, 0 through 9. With three sets of flags, a ship could make 1,000 different combinations of three-flag signals. Then, in 1790, the British Royal Navy introduced the use of substitute or repeater pennants so that only one set of flags was needed, and the first alphabetic flag signal system in 1800. Also during this period, the United States Navy was working to develop its own marine signaling system, focusing largely on numeric signal flags hoisted inverted or in specific combinations. It wasn’t until 1857 that the British Board of Trade developed a code that had not only the previous numeric flags but also flags for alphabetic letters as well, although only 18 of them. The number of signals that could be constructed jumped to more than 20,000 in three-flag combinations, and in 1870 this system was renamed the International Code of Signals. The ICS is currently maintained by the International Maritime Organization, which published a new print edition in 2005.

Today, signal flags unique to the Navy are used when communicating among allied forces, while the ICS is used with all other vessels. The code/answer pennant precedes all signals using the ICS. Navy signalmen transmit messages while maintaining radio silence by hoisting a flag or series of flags on a halyard. One-flag signals are urgent or very common meanings as seen below:

Signal Code Flags

Flag Name Navy Meaning International Meaning
Alpha Signal Code Flag Alfa I have a diver down; keep well clear at slow speed. ---
Bravo Signal Code Flag Bravo I am taking in, discharging, or carrying dangerous cargo. ---
Charlie Signal Code Flag Charlie "Yes" or "affirmative". ---
Delta Signal Code Flag Delta I am maneuvering with difficulty; keep clear. ---
Echo Signal Code Flag Echo I am directing my course to starboard. ---
Foxtrot Signal Code Flag Foxtrot I am disabled; communicate with me.
On aircraft carriers:  Flight Operations underway
Golf Signal Code Flag Golf I require a pilot. ---
Hotel Signal Code Flag Hotel I have a pilot on board. ---
India Signal Code Flag India Coming alongside. I am directing my course to port.
Juliet Signal Code Flag Juliet I am on fire and have dangerous cargo; keep clear. ---
Kilo Signal Code Flag Kilo I wish to communicate with you. ---
Lima Signal Code Flag Lima You should stop your vessel immediately. ---
Mike Signal Code Flag Mike My vessel is stopped; making no way. ---
November Signal Code Flag November No or negative. ---
Oscar Signal Code Flag Oscar Man overboard. ---
Papa Signal Code Flag Papa All personnel return to ship; proceeding to sea (Inport). ---
Quebec Signal Code Flag Quebec Boat recall; all boats return to ship. Ship meets health regs; request clearance into port.
Romeo Signal Code Flag Romeo Preparing to replenish (At sea).  Ready duty ship (Inport). None.
Sierra Signal Code Flag Sierra Conducting flag hoist drill. Moving astern.
Tango Signal Code Flag Tango Do not pass ahead of me. Keep clear; engaged in trawling.
Uniform Signal Code Flag Uniform You are running into danger. ---
Victor Signal Code Flag Victor I require assistance. ---
Whiskey Signal Code Flag Whiskey I require medical assistance. ---
Xray Signal Code Flag Xray Stop carrying out your intentions and watch for my signals. ---
Yankee Signal Code Flag Yankee Ship has visual communications duty. I am dragging anchor.
Zulu Signal Code Flag Zulu I require a tug. ---
Code Answer Signal Code Flag Code/Answer Flag that follows is from the International Code of Signals. Message is understood. Also, numeric decimal point.
First Substitute Signal Code Flag First Substitute Absence of flag officer or unit commander (Inport). Substitute for the first flag in this hoist.
Second Substitute Signal Code Flag Second Substitute Absence of chief of staff (Inport). Substitute for the second flag in this hoist.
Third Substitute Signal Code Flag Third Substitute Absence of commanding officer (Inport). Substitute for the third flag in this hoist.
Fourth Substitute Signal Code Flag Fourth Substitute Absence of civil or military official whose flag is flying on this ship. Substitute for the fourth flag in this hoist.
Numeral One Signal Code Flag One Numeral one. None.
Numeral Two Signal Code Flag Two Numeral two. None.
Numeral Three Signal Code Flag Three Numeral three. None.
Numeral Four Signal Code Flag Four Numeral four. None.
Numeral Five Signal Code Flag Five Numeral five. None.
Numeral Six Signal Code Flag Six Numeral six. None.
Numeral Seven Signal Code Flag Seven Numeral seven. None.
Numeral Eight Signal Code Flag Eight Numeral eight. None.
Numeral Nine Signal Code Flag Nine Numeral nine. None.
Numeral Zero Signal Code Flag Zero Numeral zero. None.
Pennant One Signal Code Flag Pennant One Pennant one. Numeral one.
Pennant Two Signal Code Flag Pennant Two Pennant two. Numeral two.
Pennant Three Signal Code Flag Pennant Three Pennant three. Numeral three.
Pennant Four Signal Code Flag Pennant Four Pennant four. Numeral four.
Pennant Five Signal Code Flag Pennant Five Pennant five. Numeral five.
Pennant Six Signal Code Flag Pennant Six Pennant six. Numeral six.
Pennant Seven Signal Code Flag Pennant Seven Pennant seven. Numeral seven.
Pennant Eight Signal Code Flag Pennant Eight Pennant eight. Numeral eight.
Pennant Nine Signal Code Flag Pennant Nine Pennant nine. Numeral nine.
Pennant Zero Signal Code Flag Pennant Zero Pennant zero. Numeral zero.

In some instances, two-flag combinations are used for common situations.  A selection of those two-flag code meanings is found below:

AE Code Signal Flag Message

A + E = I must abandon my vessel

CJ Code Signal Flag Message

C + J = Do you require assistance?

CN Signal Code Flag Message

C + N = I am unable to give assistance

JI Signal Code Flag Message

J + I = Are you aground?

JL Signal Code Flag Message

J + L = You are running the risk of going aground

JW Signal Code Flag Message

J + W = I have sprung a leak

KN Signal Code Flag Message

K + N = I cannot take you in tow

NC Signal Code Flag Message

N + C = I am in distress

NF Signal Code Flag Message

N + F = You are running into danger

NG Signal Code Flag Message

N + G = You are in a dangerous position

NF Signal Code Flag Message


By Chad Creech, All Star Flags