Annex IV — Distress signals
Rule 37 requires a vessel in distress and requiring assistance to use or exhibit the signals in Annex IV. The annex is short: the signals, a ban on misusing them, and further signals it draws attention to. Every signal in the annex's own order, how to tell them apart from signals that are not distress, and how the list comes up in an MCA oral.
The list of distress signals, in three sections. Section 1 lists the signals that indicate 'distress and need of assistance' — fifteen of them, lettered (a) to (o). Section 2 prohibits misusing them. Section 3 draws attention to further guidance and to two more signals.
Rule 37 is what makes the list binding: a vessel in distress and requiring assistance must use or exhibit the signals described in Annex IV.
No. Section 1 says the signals may be used or exhibited 'either together or separately'. Any one of them indicates distress and need of assistance.
(a) Gunfire or other explosive signals, fired at intervals of about a minute.
(b) Any fog-signalling apparatus, sounded continuously.
(c) Red stars thrown by rockets or shells, 'fired one at a time at short intervals'.
(d) SOS in Morse code — the group …---… — sent by any signalling method.
(e) The spoken word 'MAYDAY', sent by radiotelephony.
(f) N.C., the International Code Signal of distress.
(g) A ball, or something that looks like one, shown above or below a square flag.
(h) Flames on the vessel, such as from a burning tar or oil barrel.
(i) A red light from a rocket parachute flare or a hand-flare.
(j) Orange-coloured smoke from a smoke signal.
(k) Arms outstretched to each side, raised and lowered slowly and repeatedly.
(l) A distress alert by digital selective calling (DSC), on VHF channel 70, or on MF/HF on 2 187.5 kHz, 4 207.5 kHz, 6 312 kHz, 8 414.5 kHz, 12 577 kHz or 16 804.5 kHz.
(m) A distress alert sent ship-to-shore through the ship's satellite ship earth station — Inmarsat, or another mobile satellite service provider.
(n) Signals from emergency position-indicating radio beacons (EPIRBs).
(o) Approved signals sent by radiocommunications systems — survival craft radar transponders among them.
In practice, the ones you meet directly from the bridge or deck are the sound, light, smoke, flag and arm signals: a fog signal sounding continuously, gunfire at about one-minute intervals, red stars, a red parachute flare or hand-flare, orange smoke, flames, SOS by lamp or by sound, N.C. or the square flag and ball, and the arm signal. MAYDAY reaches you by radiotelephony, a DSC alert through your own DSC equipment, and a survival craft radar transponder on your radar. Treat any of them as distress until you know otherwise.
No. Section 2 prohibits using or exhibiting any of the section 1 signals except to indicate distress and need of assistance, and prohibits using other signals which may be confused with any of them.
To attract another vessel's attention without being in distress, Rule 36 allows light or sound signals that cannot be mistaken for any signal authorised elsewhere in the rules, or a searchlight directed towards the danger.
The relevant sections of the International Code of Signals and of the International Aeronautical and Maritime Search and Rescue Manual, Volume III, and two signals: a piece of orange-coloured canvas with either a black square and circle or another appropriate symbol, 'for identification from the air'; and a dye marker.
Those two are not among the fifteen in section 1. Section 3 draws attention to them; it does not list them as distress signals.
Not on that signal alone. Rule 27(h) says the signals in Rule 27 — for vessels not under command or restricted in their ability to manoeuvre — 'are not signals of vessels in distress and requiring assistance', and points to Annex IV for those. Two all-round red lights in a vertical line say she is not under command — under Rule 3(f), unable through some exceptional circumstance to manoeuvre as the rules require — not that she needs help.
It may come up as a list to give in full, or as a signal to recognise. Examples of the kind of question to be ready for:
“Give me the distress signals in Annex IV.”
“Which distress signal uses a square flag?”
“On which VHF channel is a DSC distress alert sent?”
“A vessel shows two all-round red lights in a vertical line. Is she in distress?”
“What is an orange canvas with a black square and circle for?”
“Can you fire a red hand-flare to wake up a vessel that hasn't seen you?”
The common slips: stopping after the flares and forgetting the radio and electronic signals; describing the arm signal as a wave; counting the orange canvas and dye marker among the section 1 signals; reading the not-under-command lights as distress; and offering a distress signal as a way to attract attention. The Rule 37 page groups the same fifteen by type, which may be easier to learn.
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