Comprehensive Guide to GMDSS Tests and Procedures

Daily, Weekly And Monthly Tests of GMDSS Equipment on board.

The development of GMDSS (Global Maritime Distress And Safety System) for the shipping industry has come a long way. The GMDSS system was established with an objective to improve distress and safety radio communications and procedures at sea.

The greatest benefit of the GMDSS equipment is that it vastly reduces the chances of ships disappearing without a trace, and enables search and rescue (SAR) operations to be launched without delay and directed to the exact site of a maritime disaster.

With the implementation of GMDSS, every deck officer with a General Operator Certificate (GOC) and the license is entitled to use the GMDSS equipment and make radio communications when needed.

For the GMDSS equipment to function properly and effectively in the event of an emergency, it is critical that officers must understand its purpose and do the required maintenance on board the vessel to keep it in a working condition and make the best use.

The daily, weekly and monthly tests of the equipment should be done by every navigating officer responsible for it without any compromise.

Vessel must be capable of performing the nine functional GMDSS requirements, here are they:

- Ship-to-shore distress alerting;

- Shore-to-ship distress alerting;

- Ship-to-ship distress alerting;

- SAR coordination;

- On-scene communications;

- Transmission and receipt of emergency locating signals;

- Transmission and receipt of MSI;

- General radio communications;

- Bridge-to-bridge communications.

This can be ensured by testing the GMDSS equipment at regular intervals. The GMDSS equipment and systems include the VHF DSC/RT, MF/HF DSC/RT, INMARSAT, SART, EPIRB, NAVTEX, and SURVIVAL CRAFT TWO WAY VHF.

Daily Tests on GMDSS Equipment.

The proper functioning of the Digital Selective Calling (DSC) facilities shall be tested at least once each day, without radiation of signals, by the use of the equipment’s Internal test facility (VHF and MF/HF). The daily test checks the internal connection, transmitting output power and the display. The process can differ from equipment to equipment based on the maker.

Weekly tests on GMDSS Equipment.

The proper functioning of the Digital Selective Calling (DSC) facilities with sending a test call to Shore station and obtaining an acknowledgement. Often happens that the deck officer does not receive any acknowledgement from the shore station. In such cases, we must take it for granted that the shore station is not sending the acknowledgement. However, this might not be the case.

The problem could be with our equipment too. To make sure that the MF/HF equipment is in order, it is better we try sending the test call using other frequencies and to other stations. Even if then we fail to receive any acknowledgement, a test call can be sent to a passing vessel if possible. Instead of keying the coast ID, key in the MMSI of the passing vessel. It is better to call the ship and confirm if they have received the test call. Also we can request them to send us a test call to ensure that the equipment receiving facility is functioning properly.

Monthly Tests on GMDSS Equipment.


The Emergency Position Indicating Radio Beacon or EPIRB should be examined by carrying out a self-test function without using the satellite system. No emergency signal is transmitted during the self-test, test the battery voltage, output power and frequency are checked. The EPIRB should also be checked for any physical damage. The expiry date of the battery unit and that of the hydrostatic release unit should be checked. Also, check that the safety clip is properly attached and in place.

A successful test will consist of a series of blinks on the LED test-indicator, followed by a continuous light and a strobe flash after approximately 15 seconds. The last green led indicates a successful test. After the successful completion of the test, the switch is released and the EPIRB is put back into the bracket.


The Search and Rescue Transponder or SART is also equipped with a self-test mechanism to test the operational function of the beacon. The SART is tested using vessel's X band radar. The test should preferably be done in open seas to avoid interference on the radar display.

Survival Craft Two Way Portable VHF Equipment:

Each survival craft two way VHF equipment should be tested at least once a month to ensure proper operation in case of a distress situation. It should be tested on a frequency other than VHF channel 16 (156.8 MHz). The expiry date of the battery needs to be checked and changed when required.


The Navtex is an equally important GMDSS equipment and is the source of maritime safety information. It is also equipped with a test function that can test the battery, keyboard, LCD, ROM and RAM. It is a good practice to test the Navtex and detect an error if any. If the test is successful the results show OK otherwise it will show NG meaning – No Good.


The INMARSAT is also equipped with a diagnostic test which checks it for proper operation. A PV test or Performance Verification test can be performed every month. This test consists of receiving a test message from an LES (Local Earth Station), transmitting a message to an LES and a distress alert test.

GMDSS Battery:

The battery connections and compartment should also be checked. The level of the electrolyte and the specific gravity of each cell should be checked and recorded. Sulfation can reduce the specific gravity thereby reducing the battery capacity. Maintenance free batteries on board, however, do not require any such checks.

Recommended every month visually check all antennas for the security of mounting and visible damage to the cables. Any deposit of dirt and salt should be removed. It is also important to check the condition of the aerials and insulators along with the help of an electrical officer. Ensure that the equipment is switched off and isolated before carrying out any work on the antenna.

GMDSS enables a ship in distress to send an alert using various radio systems. It is therefore important that all the GMDSS equipment are maintained in a state of readiness and working condition. To achieve this it is mandatory to perform the daily, weekly and monthly tests. Only then can we ensure the safety of the ship and its crew.


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