Flags - Signal Code Message Definitions

Signal flags are used at sea for communication between ships. Individual flags and combinations of flags can spell short messages, and some of them have special meanings as well.

Signal Code Flag Definitions - PDF

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Signal Flag Definitions

Letter/Number	Signal Flags	Signal Flag Meanings	Yacht / Dinghy Racing Signal Meanings
A		Diver below (when stationary); I am undergoing a speed trial
B		I am taking on or discharging explosives	Protest
C		Yes (affirmative)	Position of next mark has been changed
D		Keep clear of me, I am manoevering with difficulty	Don't launch/follow this rib
E		I am altering my course to starboard
F		I am disabled, communicate with me
G		I require a pilot
H		I have a pilot on board
I		I am altering my course to port	Round the ends
J		I am going to send a message by semaphore
K		You should stop your vessel instantly
L		You should stop, I have something important to communicate	Change to SIs or other amendment
M		I have a doctor on board	There is a mark missing
N		No (negative)	Abandon
O		Man overboard	Rule 42 is waived
P		The Blue Peter - all aboard, vessel is about to proceed sea. (At sea) your lights are out or burning badly	Preparatory
Q		My vessel is healthy and I request free practique
R		The way is off my ship. You may feel you way past me	Rule 42 is restored
S		My engines are going full speed astern	shortened course
T		Do not pass ahead of me
U		You are standing into danger	One step less stringent than a black flag, allows boats back in after a general recall or abandonment
V		I require assistance (not distress)
W		I require medical assistance
X		Stop carrying out your intentions and watch for my signals	Individual recall
Y		I am carrying mail	Lifejackets must be worn
Z		To be used to address or call shore stations	20% scoring penalty
		1st Subsititute
		2nd Subsititute
		3rd Subsititute
		Answer	Postponement
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