Emergencies, GMDSS and Search and Rescue

Prerequisites

You should hold, or be studying for, the GMDSS General Operator's Certificate (GOC), which an OOW on a SOLAS ship normally needs alongside the Certificate of Competency. From the RYA and earlier lessons you should know VHF DSC procedure, Mayday, Pan-Pan and Securité calls, man overboard recovery on a small craft, and the basics of fire and flooding. You should also have completed the STCW basic safety training (personal survival techniques, fire prevention and firefighting, elementary first aid, and personal safety and social responsibilities).

This lesson covers what STCW Table A-II/1 expects of the OOW in an emergency: respond to a distress signal at sea, take immediate action in fire, flooding, collision and grounding, carry out the correct man overboard manoeuvre, and take part in a search under the IAMSAR Manual. It finishes with the muster list and drills.

Learning Objectives

• Describe the GMDSS sea areas A1 to A4 and the equipment each requires.
• Explain how DSC, EPIRBs, SARTs, NAVTEX and satellite systems work, and how to send, receive and cancel a distress alert.
• Choose and execute the correct man overboard manoeuvre: Williamson, Anderson or Scharnow.
• State the immediate actions for fire, flooding, collision and grounding.
• Explain the roles of the SAR mission coordinator and on-scene coordinator, and use IAMSAR Vol III search patterns.
• Describe the muster list, emergency signals and drill requirements.

The Global Maritime Distress and Safety System

GMDSS, introduced by SOLAS Chapter IV, replaced the old system of radio officers listening for Morse and voice distress calls. Its principle is simple: shore authorities, as well as ships near by, are alerted rapidly to a distress, so a coordinated search and rescue can begin with minimum delay. It applies to all cargo ships of 300 GT and over and all passenger ships on international voyages.

GMDSS has nine functions that every ship must be able to perform: distress alerting ship to shore, ship to ship and shore to ship; SAR coordinating communications; on-scene communications; locating signals; receiving maritime safety information (MSI); general radio communications; and bridge-to-bridge communications.

Sea areas

The equipment a ship must carry depends on where she trades. The diagram below shows the four sea areas.

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Each Administration declares its own A1 and A2 areas, which are listed in the Admiralty List of Radio Signals Volume 5 (NP285). Since 2020 Iridium has been recognised alongside Inmarsat, and amendments to SOLAS Chapter IV that entered into force on 1 January 2024 modernised the equipment requirements; check the current regulations and your ship's Record of Equipment (Form R to the safety certificate).

Maintenance and duplication

Ships in A3 and A4 must ensure availability by at least two of: duplication of equipment, shore-based maintenance, or at-sea electronic maintenance capability. The ship must also have a reserve source of energy (batteries) to run the GMDSS for a set period if the main and emergency supplies fail. The OOW usually carries out the daily, weekly and monthly GMDSS tests and records them in the GMDSS radio log.

The GMDSS Equipment

Digital Selective Calling (DSC)

DSC sends a short digital message on a dedicated channel. A distress alert contains the ship's MMSI, position, time and (if entered) the nature of distress. The frequencies are:

Sending a distress alert. Lift the cover, select the nature of distress if time allows, and press the distress button for about five seconds. The set repeats the alert automatically until it is acknowledged. Then follow up with a Mayday voice call on the associated voice channel (Channel 16 on VHF).

Receiving a distress alert from another ship. The general rule is that ships do not acknowledge a DSC distress alert by DSC; that is the job of the coast station or RCC. On receiving a VHF or MF DSC alert:

1. Listen on the associated voice channel (Channel 16 or 2182 kHz) for the Mayday call.
2. Inform the master at once, and record the details in the GMDSS log.
3. If the ship in distress is nearby and no coast station acknowledges, acknowledge by voice and inform the nearest RCC by any means.
4. Relay or acknowledge by DSC only if instructed by an RCC or the master, following the IMO flow diagrams for actions on receipt of a distress alert, which should be posted at the GMDSS station.

SOLAS Chapter V, Regulation 33, requires the master of a ship at sea that receives information that persons are in distress to proceed with all speed to their assistance, if possible informing them or the SAR service. If the master decides it is unreasonable or unnecessary to proceed, the reason must be entered in the log.

Cancelling a false alert. False alerts waste SAR resources. If you send one by mistake, reset the equipment at once (switch off if needed) and then broadcast a voice cancellation on the associated channel, for example on Channel 16: "All stations, all stations, all stations, this is [ship name, call sign, MMSI], position [...], cancel my distress alert of [date and time UTC]. Master [name]." Inform the RCC as well.

EPIRB

The 406 MHz EPIRB (emergency position-indicating radio beacon) sends a distress alert to the Cospas-Sarsat satellite system, which passes it to an RCC. Modern EPIRBs include a GNSS receiver so the alert carries the position, and a 121.5 MHz homing signal so SAR aircraft and ships can locate it. The coded identity links to the ship's registration database.

The EPIRB is mounted in a float-free bracket with a hydrostatic release unit (HRU) that frees it at a depth of a few metres if the ship sinks; it then floats to the surface and activates automatically. It can also be activated manually.

OOW checks: the EPIRB is correctly installed and armed, the HRU and battery are in date (disposable HRUs typically have a two-year life), the monthly self-test is done and logged, the registration is current, and the shore-based maintenance (at intervals not exceeding five years) is in date. An annual test is part of the radio survey.

SART

The search and rescue transponder helps rescuers home in on survival craft. There are two types:

• Radar SART. Operates on 9 GHz (X-band). When triggered by a rescuer's X-band radar it transmits a signal that appears on the radar as a line of 12 dots extending outwards from the SART's position along its bearing. As the rescue ship closes to within about 1 nm, the dots become arcs, and at very close range concentric circles. The SART is detectable by a ship at about 5 nm when held 1 m above the sea; hold it as high as possible. S-band (10 cm) radar will not trigger it.
• AIS-SART. Transmits AIS position reports. It appears on AIS displays and ECDIS as a distinctive target (a circle with a cross) labelled SART ACTIVE, with an MMSI beginning 970.

At least one SART is required on ships of 300 to 500 GT and two on ships of 500 GT and over, one on each side.

Maritime safety information: NAVTEX and EGC

NAVTEX is a printed (or screen) broadcast of navigational and meteorological warnings and urgent information, received automatically on 518 kHz in English, typically within about 250 to 400 nm of the transmitter. A second channel, 490 kHz, carries national-language broadcasts in some countries, and 4209.5 kHz is used in some tropical areas.

Each message has a four-character header: transmitter identity letter, subject indicator letter and a two-digit serial number. Some subject indicators:

Messages with subject indicators A, B, D and L cannot be rejected by the receiver. The OOW selects the appropriate transmitters for the voyage and reads every new warning, plotting relevant navigational warnings on the chart or ECDIS.

Enhanced Group Call (EGC) carries MSI by satellite beyond NAVTEX range, through Inmarsat SafetyNET or Iridium SafetyCast, for the ship's NAVAREA and METAREA. The ship must be able to receive MSI throughout her voyage.

Satellite communications

Inmarsat (Inmarsat C and Fleet Safety) and Iridium provide distress alerting with a single button (or menu), distress priority messaging to an RCC, and general communications. Inmarsat's geostationary satellites do not cover the poles; Iridium's low-orbit constellation covers the whole globe.

Man Overboard

A person who falls from a ship is in grave danger: the ship takes minutes to stop or turn, the propeller and the hull are hazards, and a head in the water is lost from sight within a few cables in any sea. The immediate actions, which must be instinctive, are:

1. Shout "man overboard" and the side, and release a lifebuoy with light and smoke signal (the bridge wing lifebuoys are for this).
2. Put the helm hard over towards the person's side to swing the stern and propeller away from them (if the turn is started at once).
3. Press the MOB button on GNSS or ECDIS to mark the position, and note the time.
4. Raise the alarm with the signal in your ship's muster list (many ships use three prolonged blasts), and hoist flag "O" by day (International Code of Signals: man overboard).
5. Post lookouts with binoculars, pointing continuously at the person.
6. Call the master, put the engine on standby, prepare the rescue boat, and send a DSC alert or urgency/distress message as appropriate.

Choosing the turn

The IAMSAR Manual Vol III describes three standard manoeuvres. The diagram below compares them for a person lost on the starboard side.

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Williamson turn. Rudder hard over towards the person. When the heading has changed by 60° from the original course, put the rudder hard over to the other side. When the heading is 20° short of the reciprocal course, put the rudder amidships and steady on the reciprocal.

• Brings the ship back onto her original track, heading in the opposite direction.
• Works for an immediate action, a delayed action and a person missing (for example, discovered missing at muster): following the reciprocal track is the best way to search.
• Good in restricted visibility and at night.
• Takes the ship some distance from the scene and is slow.

Anderson turn (single turn). Rudder hard over towards the person. After a deviation of about 250° from the original course, put the rudder amidships and begin the stopping manoeuvre.

• The fastest recovery method, best for an immediate action when the person is in sight.
• Suits ships with good turning performance and enough engine power (handy ships, twin screw ships).
• Difficult for a large single screw ship, because the approach to the person is not on a straight course.

Scharnow turn. Rudder hard over. After a deviation of 240° from the original course, put the rudder hard over to the other side. When the heading is 20° short of the reciprocal, rudder amidships and steady on the reciprocal course.

• Brings the ship back into her own wake, covering less distance than a Williamson turn and saving time.
• Not effective for an immediate action: it only works if enough time has passed since the person fell for the ship to be some way past them.

The angles given are guidance from IAMSAR; the actual figures for your ship should be found by trial and are often given in the manoeuvring booklet or company procedures.

Recovery

As the ship returns, reduce speed in good time and approach so the person is on the lee side, in the lee of the hull, with the propeller stopped when close. Launch the rescue boat if conditions allow; otherwise use a scrambling net, recovery device or rescue sling. A person who has been in cold water may collapse when lifted vertically; recover in a horizontal position where possible and treat for hypothermia.

Shipboard Emergencies: Immediate Actions

The ship's Safety Management System (SMS) contains emergency checklists for each situation; the OOW must know the first steps by heart, because the first minutes decide the outcome. In every case: raise the alarm, call the master, and inform the engine room.

Fire

1. Sound the fire alarm or general emergency alarm; announce the location over the public address.
2. Call the master and the engine room; muster the fire parties according to the muster list.
3. Reduce speed and, if possible, alter course so the fire is downwind of the rest of the ship, reducing the relative wind over the fire (for example, with a fire forward, bring the wind astern and slow down so the relative wind is light).
4. Stop ventilation fans to the affected space, close fire doors, dampers and openings (fire boundaries).
5. Start boundary cooling of adjacent spaces.
6. Use fixed fire-fighting systems (CO2 flooding, water mist, foam) only on the master's order and after the space has been evacuated and everyone counted; CO2 is lethal.
7. Send an urgency or distress message if the fire is not quickly controlled; keep a log of times and actions.

Flooding

1. Sound the general alarm and call the master and engine room.
2. Close all watertight doors and openings (on ships with powered watertight doors, they should normally be closed at sea anyway).
3. Find the source and extent: sound all tanks and bilges, check the bilge alarms.
4. Start pumping; consider whether the damage is above or below the waterline and whether changing heading or speed will reduce the inflow.
5. Assess the damage stability with the chief officer using the damage control plan and loading computer.
6. Prepare survival craft and send an urgency or distress message if the situation may deteriorate; consider beaching in a safe place as a last resort.

Collision

1. Sound the general alarm; call the master and engine room.
2. Stop the engines. If the other ship's bow is embedded in your hull, do not go astern or pull apart without careful thought; the hole may be partly plugged by the other ship's bow, and separating could let the sea in faster.
3. Close watertight doors; sound all tanks and bilges; check for flooding, fire and pollution.
4. Muster and account for all crew; check for injuries.
5. Show the correct lights or shapes and sound signals (for example, not under command if appropriate).
6. Exchange information with the other ship. Under the Merchant Shipping Act 1995 (section 92), the master must render assistance to the other ship and give her name, port of registry and ports of departure and destination. Inform the coast state, company (DPA) and, for UK ships, the MAIB.
7. Preserve the VDR data (press the save button), the logbooks and charts.

Grounding

1. Stop the engines; sound the general alarm; call the master and engine room.
2. Close watertight doors; sound all tanks and bilges; check for hull breach and pollution.
3. Take soundings all round the ship to find where she is aground and the depth of water.
4. Find the state and time of the tide: falling tide means the ship will settle further; rising tide may lift her off.
5. Exhibit the aground signals: two all-round red lights in a vertical line plus anchor lights by night, or three balls in a vertical line by day (COLREG Rule 30(d)), and sound the aground fog signal if needed (Rule 35).
6. Do not go astern in haste. Refloating before the damage is understood can sink a holed ship in deep water or cause further damage to the hull, rudder and propeller.
7. Consider laying out an anchor to stop the ship being driven further ashore; inform the coast state, company and MAIB.

Search and Rescue: IAMSAR Vol III

The IAMSAR Manual (International Aeronautical and Maritime Search and Rescue Manual) is published jointly by IMO and ICAO in three volumes. Volume III, Mobile Facilities, must be carried on board under SOLAS Chapter V, Regulation 21. It tells ships how to respond to a distress, take part in a search, and act as on-scene coordinator.

The SAR organisation

The first ship to arrive may act as OSC until the SMC designates one. The OSC keeps a communications watch, plots all units, sends regular situation reports (SITREPs) to the SMC, and decides when to change patterns, subject to the SMC.

Search patterns

The search area is based on the datum: the most probable position of the target, adjusted for drift caused by current and wind (leeway) since the time of the incident. The choice of pattern depends on how well the datum is known, the size of the area and the number of searching units. The diagram below shows the three patterns most used by ships.

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Expanding square search (SS). Begins at the datum and spirals outwards in a square pattern, with legs of S, S, 2S, 2S, 3S, 3S and so on, all turns being 90° in the same direction. It is used when the location of the target is known within relatively close limits and with one ship. It needs accurate navigation; IAMSAR advises orienting the first leg into the wind for some targets.

Sector search (VS). Used when the position of the target is accurately known and the search area is small, typically for a man overboard or a person sighted then lost. The ship runs out from the datum a set distance (the radius, often 2 to 5 nm for a ship), turns 120° to starboard, runs the same distance, turns 120° again and passes back through the datum. This is repeated three times. A marker such as a smoke float or lifebuoy may be dropped at the datum. If nothing is found, a second search is made with the pattern rotated 30°.

Parallel track search (PS). Used for a large area when the target's position is uncertain. Ships search along parallel legs at a set track spacing (S), either one ship sweeping back and forth or several ships abreast. Legs normally run parallel to the long side of the area.

Track spacing depends on the target, the visibility, sea state and height of eye; IAMSAR Vol III gives recommended spacings in tables. Searching ships keep a sharp lookout from a good height, with extra lookouts posted, and use radar and AIS. For a person in the water, track spacing is small, often less than a mile.

Being a searching ship

• Plot the datum and the area assigned by the OSC or SMC.
• Brief the lookouts, post them high and in sectors, and rotate them often (a lookout's efficiency falls after about 30 minutes).
• Keep the speed and track ordered so the pattern is accurate.
• Report anything sighted, with position and time, to the OSC at once.
• Prepare to recover survivors: rescue boat, scrambling nets, pilot ladder, lights, medical team, blankets.

Muster List and Drills

The muster list

SOLAS Chapter III, Regulations 8 and 37, require every ship to have a muster list posted in conspicuous places, including the bridge, engine room and crew accommodation. It shows:

• The general emergency alarm signal: seven or more short blasts followed by one long blast on the ship's whistle and the alarm bells.
• The actions each crew member must take on hearing the alarm and the abandon ship order (given by the master by voice).
• Each person's duties in emergencies: closing watertight doors and fire doors, preparing survival craft, fire parties, first aid, passenger handling and communications.
• Who substitutes for key people if they are injured.
• The officers responsible for the maintenance of life-saving and fire-fighting appliances.

Each crew member has an emergency card in their cabin and their duty on the muster list. As OOW, know your own role and, because you may be on watch when an emergency starts, the bridge's role in each.

Drills

Passenger ships have additional requirements, including weekly drills and a passenger muster on or before departure. Check the current SOLAS text and your company SMS for full details. Drills must be realistic, recorded in the official logbook, and followed by a debrief so that lessons are learned.

Worked Example: A Night-Time MOB and Search

You are OOW at 0215 on a 180 m general cargo ship at 14 knots, course 045°, wind northwest force 4, visibility good, sea temperature 12°C. The lookout reports a shout from aft; the bosun on a fire round radios that a crew member has fallen from the poop deck on the port side about a minute ago.

Immediate action. You put the helm hard to port, press the MOB button on the ECDIS, release the port bridge wing lifebuoy with light and smoke, sound the general alarm, and call the master. Since you do not know exactly when the person fell, and it is dark, you choose a Williamson turn: at 60° off course (heading 345°) you order the helm hard to starboard; at 20° short of the reciprocal (heading 205°) you order midships and steady on 225°.

Communications. The master arrives and takes the con. You send a DSC urgency call, then a Pan-Pan on Channel 16 to the coast station and nearby ships, giving the position and time from the MOB mark. The coast station's RCC takes the role of SMC and asks the ship to act as OSC until a SAR helicopter arrives.

Search. On the reciprocal track the lifebuoy light is sighted but no person. With the datum accurately known, the master orders a sector search with a radius of 1 nm, adjusted for drift. On the second leg a lookout sights a light (the crew member's lifejacket light). The rescue boat is launched on the lee side and recovers the person, who is treated for cold shock and hypothermia.

Afterwards. The time, positions, actions and communications are logged; the VDR is saved; the RCC is informed that the person has been recovered so it can stand down the helicopter; the company DPA is informed; and a near-miss and accident report is made under the SMS.

Common Mistakes

• Losing sight of the person. Without a dedicated pointing lookout, a person in the water is lost in seconds. Assign one at once.
• Choosing the Scharnow turn for an immediate action. It only works when the ship is already well past the person.
• Acknowledging a distress alert by DSC without being told to. This can stop the coast station's acknowledgement and confuse the RCC. Listen on the voice channel and follow the IMO flow diagram.
• Not cancelling a false alert. Always reset and send a voice cancellation, and inform the RCC.
• Releasing CO2 before a full head count. Evacuate and count everyone first.
• Going astern straight after a grounding. Assess the damage, tide and stability first.
• Pulling apart after a collision. The other ship's bow may be holding the sea out.
• Treating drills as a formality. Unrealistic drills produce crews who freeze in a real emergency.
• Out-of-date EPIRB, HRU or SART batteries. Check the expiry dates at every monthly test.

Summary

• GMDSS sea areas: A1 VHF DSC coverage, A2 MF DSC coverage, A3 recognised satellite coverage, A4 the remainder (polar). Each area requires more equipment.
• DSC distress: Channel 70 (VHF) and 2187.5 kHz (MF), followed by voice on Channel 16 or 2182 kHz. Ships do not normally acknowledge by DSC.
• 406 MHz EPIRBs alert via Cospas-Sarsat and float free; radar SARTs show 12 dots on X-band radar; AIS-SARTs show as SART ACTIVE targets.
• NAVTEX on 518 kHz; messages A, B, D and L cannot be rejected. EGC covers MSI beyond NAVTEX range.
• MOB: Anderson is fastest for an immediate action; Williamson works in all cases and returns along the track; Scharnow brings the ship back into her wake but not for an immediate action.
• Fire, flooding, collision and grounding: raise the alarm, call the master and engine room, close watertight doors, assess, communicate, and do not take hasty irreversible actions.
• IAMSAR: SMC ashore, OSC on scene; expanding square and sector search when the datum is well known, parallel track for large areas.
• The muster list shows the general alarm (seven or more short and one long blast) and everyone's duties; drills are at least monthly for every crew member.

Check Your Understanding

1. Define GMDSS sea area A2 and state the extra equipment a ship in A2 must carry compared with A1.

Answer: A2 is the area outside A1 but within the coverage of at least one MF coast station providing continuous DSC alerting (typically about 100 to 150 nm). The ship needs an MF radiotelephone with DSC on 2187.5 kHz in addition to the A1 equipment.

1. You receive a VHF DSC distress alert from a ship 8 nm away. No coast station has acknowledged after a few minutes. What do you do?

Answer: Listen on Channel 16 for the Mayday, inform the master, log the details. If the ship is nearby and no coast station acknowledges, acknowledge by voice on Channel 16 and inform the nearest RCC by any means. Do not acknowledge by DSC unless instructed. Under SOLAS V/33 the master must proceed to assist.

1. What does a radar SART look like on the screen, and which radar will trigger it?

Answer: A line of 12 dots extending outwards from the SART's position along its bearing, becoming arcs and then concentric circles as the ship closes within about 1 nm. Only a 9 GHz X-band (3 cm) radar triggers it.

1. Which NAVTEX message types cannot be rejected by the receiver?

Answer: A (navigational warnings), B (meteorological warnings), D (search and rescue information and piracy warnings) and L (additional navigational warnings).

1. A crew member is reported missing at the morning muster, last seen four hours earlier. Which manoeuvre do you use and why?

Answer: The Williamson turn, because it brings the ship back onto her original track on the reciprocal course, so she can search back along the route she has followed. Anderson and Scharnow are unsuitable for a person missing for an unknown time.

1. Describe the Scharnow turn and say when it should not be used.

Answer: Rudder hard over; after a deviation of 240° from the original course, rudder hard over the other way; when 20° short of the reciprocal, rudder amidships and steady on the reciprocal. It brings the ship back into her own wake. It should not be used for an immediate action, because the ship must already be some distance past the person.

1. Your ship has a fire in the forecastle store. What course and speed action should you consider and why?

Answer: Reduce speed and alter course so that the fire is downwind of the rest of the ship, for example bringing the wind astern, so flames and smoke blow away from the accommodation and the relative wind over the fire is reduced.

1. After a collision, the other ship's bow is embedded in your side. Why should you not immediately go astern or pull apart?

Answer: The other ship's bow may be partly plugging the hole. Separating could let the sea in much faster and sink the ship or cause a sudden loss of stability. Assess the damage and prepare first.

1. What is the difference between the SMC and the OSC?

Answer: The SAR Mission Coordinator works in the RCC ashore and plans and coordinates the whole operation. The On-Scene Coordinator is designated by the SMC, often the master of a ship at the scene, and coordinates the search units on scene, reporting by SITREPs to the SMC.

1. When would you use a sector search rather than an expanding square?

Answer: When the position of the target is accurately known and the area is small, such as a man overboard with the position marked. The sector search passes through the datum three times. The expanding square is used when the position is known within close limits but less precisely.

Further Reading

• IAMSAR Manual Volume III, Mobile Facilities (IMO/ICAO)
• SOLAS consolidated edition (IMO), Chapter IV Radiocommunications and Chapter V Safety of Navigation
• IMO Model Course 1.25, GMDSS General Operator's Certificate
• MIN 542 (M+F) Amendment 3, recognised distress signals
• MCA Code of Safe Working Practices for Merchant Seafarers (COSWP)
• ICS Bridge Procedures Guide, 6th edition (International Chamber of Shipping, 2022)
• D.J. House, Seamanship Techniques, 4th edition (Routledge)
• IMO Model Course 7.03, Officer in Charge of a Navigational Watch