Module 11 — Distress, urgency and safety procedures
Mayday, Pan-Pan and Sécurité applied across the GMDSS equipment: DSC alert + voice, acknowledgement, relay, distress traffic and cancellation.
This module binds priority theory to the equipment already studied.
Decision tree
Mayday by DSC + voice
Acknowledgement and relay
A coast station acknowledges. If no acknowledgement is heard, any capable station must relay (distress relay) so the alert is not left unmanaged.
Distress traffic
The coordinating station can impose silence (Seelonce Mayday) until lifted (Seelonce Feenee).
Pan-Pan and Sécurité
Same DSC alert pattern (urgency / safety category) plus voice on the associated frequency.
False alert
Immediate cancellation by DSC and voice, identifying the vessel and giving the UTC time of the original alert. Log the event.
Framework: ITU RR Articles 32 and 33
Part 5 of the manual refers explicitly to Article 32 (distress) and Article 33 (urgency and safety) of the ITU Radio Regulations. The operator does not improvise: a regulated sequence combining DSC, radiotelephony and, where applicable, RMSS is followed.
Complete alert sequence (Figure 23 of the manual)
- 1Decide whether the ship is sinking or must be abandoned.
- 2If time allows, transmit DSC alert by HF/MF/VHF or RMSS.
- 3Embark in the survival craft with portable VHF, SART and, if possible, EPIRB.
- 4Activate EPIRB and SART; float-free beacons activate themselves.
- 5Handle distress traffic with RCC and ships by HF/MF/VHF or RMSS. Pressing the button does not close anything: it only starts the chain.
MAYDAY by voice (Article 32)
After the DSC alert the ship moves to voice: 'MAYDAY, MAYDAY, MAYDAY. This is [name, call sign, MMSI, each repeated three times]. MAYDAY [name]. Position [lat/long or bearing and distance from a known point]. Nature of distress [type]. Assistance required. Number of persons on board. Other useful information. OVER'. The triple repetition of identity and of MAYDAY itself is deliberate, to allow recognition in marginal propagation.
Distress relay
If a ship hears an alert and no coast-station acknowledgement follows, it may retransmit it as 'MAYDAY RELAY' after a reasonable time, giving the original vessel's data. The operator must clearly signal that it is a relay and not an own alert.
Cancellation of a false alert (resolution MSC.514(105))
Any alert transmitted in error must be cancelled. VHF: voice on channel 16; MF: voice on 2182 kHz; HF: the corresponding working frequency; Inmarsat: contact the LES. Format: identity, MMSI, position, 'Cancel my distress alert of [UTC time]. No distress, no distress'. Failing to cancel is an operational offence with administrative consequences.
Test discipline
The distress button is never used to test the equipment: there are self-test functions and specific DSC tests with coast stations. MF/HF DSC testing with a coast station is weekly (see module 10).
CRS → RCC chain and traffic control
ITU RR Article 32 assigns control of distress traffic to the vessel in distress or to the RCC that takes over coordination through the coast station (CRS) that first received the alert. The CRS acknowledges, links to the RCC of the relevant SAR region and may transmit a shore-to-ship relay (MAYDAY RELAY) if needed. The RCC runs the rescue and may impose radio silence with SEELONCE MAYDAY on all stations not authorized to operate on the distress frequencies. Silence is lifted with SEELONCE FEENEE (French 'silence fini'). While silence is in force only ships and stations authorized by the RCC or the vessel in distress may transmit.
PAN-PAN, SÉCURITÉ and MEDICO/MEDEVAC
ITU RR Article 33 covers urgency and safety. PAN-PAN is used when a ship or a person has a serious problem that is not an immediate threat to life (engine failure, a stable sick crew member); it is spoken three times, followed by 'all stations' three times and the ship's identity. SÉCURITÉ precedes navigational or meteorological safety messages, also three times. MEDICO is medical advice by radio (MedAdvice) typically routed to a specialist centre (for example CIME in Spain, CIRM internationally); MEDEVAC is medical evacuation coordinated by the RCC when advice alone is not enough. Both travel as urgency traffic (PAN-PAN MEDICO / PAN-PAN MEDEVAC) by voice on the working frequency assigned after the matching DSC alert.
SAR organisation: detailed roles
RCC (Rescue Coordination Centre): shore command responsible for the SAR region declared by the coastal state to IMO; in maritime context it is called the MRCC (Maritime Rescue Coordination Centre). RSC (Rescue Sub-Centre): RCC-dependent sub-centre covering a sub-area when scale or complexity require it. SMC (SAR Mission Coordinator): RCC/MRCC officer assigned to the specific mission; decides search strategy, allocates resources, manages reliefs. OSC (On-Scene Coordinator): SAR asset on scene (normally the first ship or aircraft to arrive with capability) appointed by the SMC to coordinate units in the field, assign search patterns and report to the SMC. ACO (Aircraft Coordinator): when several SAR aircraft are on scene, one takes airborne coordination to prevent conflict. IAMSAR Vol. III is the shipboard pocket manual; Vol. I covers SAR system organisation and Vol. II the RCC's work.
Full MAYDAY script, word by word
After the DSC alert, voice on ch 16 / 2182 kHz / assigned HF frequency: 'MAYDAY, MAYDAY, MAYDAY. THIS IS [ship's name spoken three times], CALL SIGN [call sign], MMSI [nine digits spoken digit by digit]. MAYDAY [ship's name, once]. MY POSITION [latitude and longitude in degrees and minutes] OR [bearing and distance from a known point]. NATURE OF DISTRESS [sinking/fire/collision/listing/flooding/abandoning/piracy/man overboard]. I REQUIRE [immediate assistance/tow/medevac/firefighting]. NUMBER OF PERSONS ON BOARD [N] [+ extra info: abandoning to liferafts / taking to boats / injuries / dangerous cargo / intentions]. OVER'. After the acknowledgement, further traffic is handled under the SMC's control.
Aircraft-ship on-scene communications
Primary international SAR aircraft-ship channel: 121.5 MHz AM (aeronautical emergency) and 123.1 MHz AM (scene-of-action SAR). SAR helicopters normally also carry marine VHF at 156-162 MHz, typically ch 16 and ch 06 (on-scene). For airband reception on board a ship an aeronautical portable VHF (AM) is used when required by the carriage table (passenger ships, specific operations). Direct air-to-ship voice avoids relaying everything through the RCC and speeds up the final pickup.
Received distress alert: what to do (VHF/MF)
On receiving a DSC distress alert on VHF (ch 70) or MF (2187.5 kHz), the operator does not acknowledge immediately by DSC. Procedure
- 1note UTC time, MMSI, position and nature of distress from the alert
- 2switch to the associated voice frequency (ch 16 for VHF, 2182 kHz for MF) and listen for at least 5 minutes
- 3if a coast station or RCC acknowledges, remain on watch and offer assistance only if useful and without blocking coordination
- 4if after 5 minutes no coast acknowledgement is heard and the alert continues or is repeated, acknowledge by voice (never by DSC unless the RCC authorises it) and, if appropriate, send MAYDAY RELAY
- 5avoid unnecessary transmissions on the distress frequency
- 6log everything heard and done.
Received distress alert: what to do (HF)
HF is different: propagation means the alert travels far, where a coast station in the area is more likely to be already acknowledging. Procedure
- 1listen 5 minutes on the HF voice frequency associated with the DSC band on which the alert was received (4125/6215/8291/12290/16420 kHz)
- 2do not acknowledge by DSC or voice unless it is clear that no other station is doing so and the ship can actually help
- 3if there is evidence of coast acknowledgement or shore-to-ship relay, remain on listening watch without transmitting
- 4only send MAYDAY RELAY on HF when the coast station clearly fails to take coordination and the ship is in a position to render real assistance
- 5inform the RCC by whatever means is fastest if additional knowledge is available (visual position, eyewitness). The governing rule: on HF, disciplined silence beats impulsive acknowledgement.
Received all-ships urgency/safety announcements
Ship stations receiving all-ships urgency or safety announcements do not acknowledge. Duties
- 1if the announcement is followed by the full message, listen and note whether it affects the ship
- 2if the announcement states the message will be passed on another working frequency/channel, monitor that frequency for at least 5 minutes; if no message appears in that time, normal operation resumes
- 3do not interfere with related transmissions
- 4log only when there is operational impact (route, weather, SAR).
STCW Bridge Watch Lens
Decide applicability before manoeuvring: Rules 4-10 apply in any visibility, Rules 11-18 only when vessels are in sight, and Rule 19 governs radar-only encounters in restricted visibility.
Build the traffic picture with sight, hearing, radar/ARPA and chart context. Do not let AIS or one isolated bearing replace systematic observation.
After manoeuvring, keep monitoring bearing, range, CPA/TCPA and passing distance until the other vessel is finally past and clear.
Exam Focus
Start every scenario by classifying the encounter: overtaking, head-on, crossing, narrow channel, traffic separation, or restricted visibility.
If two rules seem to conflict, check the order carefully: overtaking duties still apply, and Rule 2 still requires ordinary seamanship.
Key Takeaways
The DSC alert always precedes the voice message.
If nobody acknowledges, another capable station must relay the alert.
Seelonce Mayday / Seelonce Feenee control distress traffic.
Every false alert is cancelled and logged.
ITU RR Articles 32 and 33 govern distress, urgency and safety and form the legal basis of the procedure.
The alert is only the start: DSC is followed by voice MAYDAY, traffic with RCC and, if needed, relay.
MAYDAY RELAY is used when an alert is heard without coast-station acknowledgement; declare it clearly.
False-alert cancellation follows resolution MSC.514(105) and is mandatory.
The RCC coordinates the rescue; the CRS acknowledges, relays and, if needed, sends MAYDAY RELAY (Art. 32 RR).
SEELONCE MAYDAY imposes silence on distress frequencies; SEELONCE FEENEE lifts it.
PAN-PAN (urgency) and SÉCURITÉ (safety) are spoken three times; governed by RR Article 33.
MEDICO = medical advice; MEDEVAC = medical evacuation; both are urgency traffic (PAN-PAN).
RCC/MRCC coordinates; SMC runs the specific mission; OSC coordinates on scene; ACO handles aircraft.
IAMSAR Vol. III is the shipboard pocket manual; Vols. I and II are for RCCs.
SAR aircraft-to-ship: 121.5 MHz AM (emergency) and 123.1 MHz AM (on-scene); helicopters also on marine ch 16/06.
Common Mistakes
Skipping the DSC alert and going straight to voice Mayday.
Failing to identify the vessel clearly in the message.
Omitting number of persons on board or assistance required.
Training only the button press and not the full chain through to cancellation or formal closure.
Confusing MAYDAY RELAY with an own alert and accidentally declaring own ship in distress.
Not cancelling a false alert out of embarrassment; the administrative cost of silence is higher.
Using the distress button as a way of testing the equipment.
Passing routine traffic on a distress frequency during SEELONCE MAYDAY.
Using MAYDAY when PAN-PAN applies (urgency without imminent loss of life).
Handling a MEDEVAC as routine instead of urgency and losing priority in the chain.
Confusing the OSC (on scene) with the SMC (ashore at the RCC): they are different functions.
Speaking to the SAR helicopter on ch 16 when 121.5 / 123.1 MHz or marine ch 06 is the on-scene channel.
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