WPC GMDSS GOC Exam (India) cheat sheet

GMDSS is a global system combining satellite and terrestrial radio so that a distress alert can be initiated automatically and shore authorities can coordinate SAR; carriage requirements depend on the ship's sea area (A1-A4).

Sea area A1: within VHF coverage of a coast station with continuous DSC alerting (about 20-30 nautical miles); A2: within MF coverage (about 100-150 nm); A3: within Inmarsat coverage (roughly 70°N to 70°S); A4: outside A1, A2 and A3 (polar regions).

Functional requirements: distress alerting, distress and safety communications, SAR coordinating communications, on-scene communications, locating signals, MSI reception, and bridge-to-bridge communications (VHF).

Distress alerting is normally initiated by DSC on VHF Ch 70 or MF/HF, or by Inmarsat; the alert carries ship identity (MMSI), position and nature of distress.

The three distress communication levels are: distress (MAYDAY), urgency (PAN PAN) and safety (SECURITE); each uses its own priority on all GMDSS subsystems.

The ship's MMSI is a 9-digit number; the first three digits are the MID (Maritime Identification Digits) identifying the flag state of the ship.

GMDSS equipment must be powered from both the main source and a dedicated reserve (emergency) source - typically a battery able to supply the equipment for a defined period.

The GMDSS radio log must record distress, urgency and safety traffic, equipment tests, and battery checks; entries must be retained and available for inspection.

The Radio Regulations (ITU) and SOLAS Chapter IV are the legal basis; the GMDSS operator holds a GOC certificate, and the ship must carry at least two operators qualified for distress and safety communications.

Distress call and message format: MAYDAY (×3), THIS IS, ship name and call sign (×3), MAYDAY, ship name, position, nature of distress, assistance required, number of persons on board, any other information; end with OVER.

Urgency signal: PAN PAN (×3) followed by the same structure as a distress message; used when a vessel or person is in grave and imminent danger but not requiring immediate assistance.

Safety signal: SECURITE (×3), announced on VHF Ch 16 or the distress/safety channel, followed by the safety message on a working channel.

VHF Ch 16 is the international distress, safety and calling channel; Ch 70 is DSC only - voice on Ch 70 is prohibited.

The distress priority must be announced with the spoken word 'MAYDAY' and, where the equipment allows, by selecting the distress priority in DSC/Inmarsat.

Radiotelephony distress acknowledgement from a coast station or ship is sent in the form of a MAYDAY message with the words 'RECEIVED MAYDAY' followed by the identification of the station in distress.

Silence periods: on MF/HF the radiotelephony distress frequency 2182 kHz is kept silent for 3 minutes after the minute and after the half-minute (i.e., hh:00-03 and hh:30-33).

Spoken alphabet and numerals: use the ITU phonetic alphabet (Alfa, Bravo, Charlie ...) and pronounce numerals digit by digit; use 'OVER', 'OUT', 'ROGER', 'SAY AGAIN' correctly.

Relay of a distress message by a station not itself in distress is permitted only when the station in distress cannot transmit or when assistance is needed; it must be prefixed 'MAYDAY RELAY'.

DSC is a digital calling system used on VHF Ch 70, MF/HF distress and calling frequencies (e.g., 2187.5 kHz, 8414.5 kHz) and HF; it carries the MMSI, priority, nature of distress and position.

DSC priorities: DISTRESS (highest), URGENCY, SAFETY, ROUTINE and SHIP BUSINESS; the priority is transmitted in the DSC message and determines how the receiving station handles it.

A distress alert should be sent on one frequency only; wait for acknowledgement (normally 5 minutes if no acknowledgement is received) before transmitting on another frequency or by another means.

A DSC distress alert must be followed by a distress message on the associated radiotelephony or NBDP channel after acknowledgement.

The DSC distress alert is normally transmitted with position and time updated (from GPS); if no position is available, the equipment sends the default (often 2°S 180° or no position) and the operator must update it manually.

Receipt of a DSC distress alert: the station must not transmit a DSC acknowledgement on HF (acknowledgement is by coast station); ships should listen on the associated voice/NBDP channel and acknowledge by radiotelephony if appropriate.

DSC self-test / test call: routine test transmissions should be made on a non-distress frequency (e.g., VHF Ch 70 test or an MF/HF test frequency) and never on the distress frequency; a test call is addressed to a coast station and confirms the link.

The DSC watch receiver must be kept on continuous watch on the distress and safety frequencies appropriate to the sea area; the watch is normally automatic and alarms on receipt of a distress alert.

MMSI in DSC: ship stations use a 9-digit ship MMSI; coast stations use a 00 prefix; group calls use a 0 prefix; a DSC distress alert is addressed to 'all stations' (distress).

Inmarsat provides global satellite communications in the L-band; the Inmarsat-C system provides store-and-forward messaging, distress alerting and SafetyNET (MSI) reception.

Inmarsat-C distress alert is initiated by pressing the distress button (or selecting distress priority) and is transmitted to the associated Rescue Coordination Centre via the Inmarsat-C LES.

Inmarsat-C uses a directional antenna that must be kept clear of obstructions; the terminal must be able to transmit a distress alert even if the ship's main power fails (reserve battery).

SafetyNET is Inmarsat's enhanced group call (EGC) service for MSI; SafetyNET messages include navigational warnings, meteorological warnings, SAR information and piracy warnings.

Inmarsat-C EGC receiver must be tuned to the correct ocean region satellite and kept on watch; the operator should check the EGC log for incoming messages.

Inmarsat-C position reporting and polling: the terminal can be polled by shore authorities for position; the operator should ensure the position is updated (GPS input) for accurate distress alerting.

Fleet F77 / FleetBroadband and Inmarsat-C differ: FleetBroadband provides voice and data; Inmarsat-C is the primary GMDSS distress and MSI terminal for sea area A3.

Inmarsat ocean regions: Atlantic Ocean Region East (AOR-E), Atlantic Ocean Region West (AOR-W), Indian Ocean Region (IOR) and Pacific Ocean Region (POR); the terminal must be logged into the correct region.

406 MHz EPIRB: transmits a digital distress alert to the COSPAS-SARSAT satellite system, containing the beacon's identity (hex ID or MMSI) and, if GPS-equipped, position; it also transmits a 121.5 MHz homing signal for SAR aircraft.

EPIRB registration: the beacon must be registered with the flag state authority; registration data includes vessel name, MMSI, owner and emergency contacts, and must be updated when details change.

EPIRB activation: manual activation by switching on, or automatic activation when the beacon floats free of a sinking vessel (hydrostatic release); test only using the built-in test function, never by activating the beacon.

EPIRB battery and HRU: the battery has a defined life (typically 5 years) and the hydrostatic release unit (HRU) must be replaced by its expiry date; both must be recorded and checked.

SART (radar transponder): operates in the 9 GHz (X-band) marine radar band; when interrogated by a radar it transmits a series of 12 dots, giving a line of 12 dots on the radar display for identification.

SART range and operation: typical detection range is about 5-10 nautical miles depending on radar height; the SART should be mounted at least 1 m above sea level and switched on only when survival craft is deployed.

SART battery: typically provides at least 96 hours of standby and 8 hours of continuous operation; check the battery expiry date and test using the built-in test function.

AIS-SART: transmits AIS position reports on AIS frequencies, displayed on AIS-equipped vessels and on chart plotters, and is an alternative to radar SART under SOLAS.

EPIRB/SART must be stowed so they are readily accessible and can be carried to the survival craft; their location must be marked and known to all crew.

NAVTEX operates on 518 kHz (international, English) and 490 kHz (national) and 4209.5 kHz (HF); it broadcasts MSI in a narrow-band direct-printing (NBDP) format.

NAVTEX message format: ZCZC (start), station identification (B1), message type (B2), message number (B3B4), then text, ending with NNNN.

NAVTEX message types include navigational warnings (A), meteorological warnings (B), ice reports (C), SAR information (D), meteorological forecasts (E), pilot service messages (F), AIS messages (G), and GNSS messages (H).

NAVTEX receiver must be kept on watch on 518 kHz; the operator should check the message log and ensure the receiver is not muted; stations within range are selected automatically.

NAVTEX coverage is coastal (about 200-400 nautical miles); for ocean passages, MSI is received via Inmarsat SafetyNET or HF NBDP.

NAVTEX message numbering: each station uses a two-digit message number (B3B4) that increments; a repeated message number indicates a re-transmission and may be ignored if already received.

Meteorological warnings (type B) are of high priority; the operator must ensure they are received and acted upon, and must record receipt in the radio log.

MSI includes navigational warnings, meteorological warnings and forecasts, SAR information, and other urgent safety information; it is broadcast on a scheduled basis and on receipt of urgent information.

The ship station licence is issued by the flag state administration; it must be on board and available for inspection, and the ship's radio equipment must be operated in accordance with its terms.

The GMDSS operator certificate (GOC) is required for operators responsible for distress and safety communications; the certificate must be on board and valid.

The Radio Regulations (ITU) define the distress and safety frequencies: 2182 kHz (MF radiotelephony), 2187.5 kHz (MF DSC), 8414.5 kHz (HF DSC), 4125 kHz and 6215 kHz (HF radiotelephony), 518 kHz (NAVTEX), VHF Ch 16 and Ch 70.

Frequency bands: MF (300 kHz-3 MHz), HF (3-30 MHz), VHF (156-174 MHz), and the 406 MHz EPIRB band and 9 GHz SART band are allocated for distress and safety.

Call sign and MMSI: the ship's call sign is assigned by the flag state; the MMSI is used for DSC and AIS and must be programmed into the equipment correctly.

Licence conditions include the requirement to keep a radio log, maintain the equipment, and ensure that only qualified operators use the distress and safety equipment.

The Radio Regulations prohibit unnecessary transmissions, profane language, and the use of distress frequencies for other than distress, urgency and safety purposes.

Frequency management: the operator must select the correct channel/frequency for the intended communication and must not transmit on frequencies allocated to other services.

Distress: a vessel or person is in grave and imminent danger and requires immediate assistance; use MAYDAY and DISTRESS priority on all systems.

Urgency: a vessel or person is in grave and imminent danger but does not require immediate assistance; use PAN PAN and URGENCY priority.

Safety: a message concerning the safety of navigation or giving important meteorological warnings; use SECURITE and SAFETY priority.

Distress alerting sequence: transmit the alert (DSC/Inmarsat), wait for acknowledgement, then transmit the distress message on the associated voice/NBDP channel; if no acknowledgement, repeat or use another means.

On receipt of a distress alert, a ship should acknowledge by radiotelephony (or as appropriate), inform the RCC, and proceed to assist if able; the ship must not transmit a DSC acknowledgement on HF.

The distress message must include the ship's position, nature of distress, assistance required, number of persons on board, and any other useful information; position and time must be accurate.

Silence periods and watchkeeping: maintain a continuous watch on the distress and safety frequencies appropriate to the sea area; do not transmit on the distress frequency except for distress, urgency or safety traffic.

Cancellation of a distress alert: if the distress is resolved, transmit a distress cancellation message (MAYDAY, then 'CANCEL DISTRESS' or the standard cancellation format) on the associated channel and inform the RCC.

False alerts: if a distress alert is transmitted accidentally, immediately cancel it by the appropriate means (DSC cancellation, voice cancellation) and inform the RCC; failure to cancel may result in unnecessary SAR action.

Daily checks: verify the DSC watch receiver is on, the VHF Ch 70 watch is active, the Inmarsat-C terminal is logged in, the NAVTEX receiver is on 518 kHz, and the EPIRB/SART are in place with valid expiry dates.

Weekly tests: test the DSC equipment (test call to a coast station or self-test), test the EPIRB and SART using their built-in test functions, and check the reserve battery voltage.

Monthly checks: check the battery capacity/voltage, inspect antennas and cables for corrosion or damage, and verify the emergency power supply operates the GMDSS equipment.

Battery types: lead-acid (vented or sealed) and NiCd; check electrolyte level (vented), specific gravity, and terminal condition; do not overcharge sealed batteries.

Reserve battery capacity: the GMDSS reserve battery must be able to supply the required equipment for the specified period (typically 1 hour for VHF/MF, 6 hours for MF/HF, and 1 hour for Inmarsat in some administrations); verify against SOLAS requirements.

Fault diagnosis: if a DSC distress alert fails, check power, antenna connection, MMSI programming, and GPS input; if the Inmarsat-C terminal fails, check the antenna, cable, and log-in status.

Antenna maintenance: keep antennas clear of obstructions, check insulators and coaxial connectors, and ensure the VHF antenna is not damaged; a high SWR indicates a cable or antenna fault.

Emergency power: the emergency generator or battery must be tested regularly and must be capable of powering the GMDSS equipment; record tests in the radio log.

Continuous watch: maintain a continuous watch on VHF Ch 16 and Ch 70, MF/HF DSC distress frequencies, and the appropriate satellite/NAVTEX services; the watch may be automatic but must be monitored.

Radio log: record all distress, urgency and safety communications, equipment tests, battery checks, and any faults; entries must be timed and signed.

Watchkeeping at sea: the GOC operator must be on duty or available; the master must ensure that a qualified operator is available for distress and safety communications at all times.

Shift handover: the relieving operator must be briefed on the current status of the equipment, any faults, and any ongoing distress or safety traffic; the handover must be recorded.

Distress traffic handling: when a distress alert is received, the operator must inform the master, acknowledge as appropriate, and maintain a listening watch on the associated channel.

Communications with SAR: use the SAR coordinating frequency (e.g., VHF Ch 16 or the designated on-scene channel) and follow the instructions of the RCC or on-scene coordinator.

Equipment status: before sailing, check that all GMDSS equipment is operational, the EPIRB and SART are on board, the NAVTEX and Inmarsat-C are working, and the batteries are charged.

Records and drills: conduct periodic GMDSS drills, record them in the log, and ensure that all operators are familiar with the equipment and procedures.