Operational requirements
General
The GMDSS enables a ship in distress to send an alert using various
radio systems. These systems are designed such that the alert has a
very high probability of being received by either shore rescue
authorities and/or other vessels in the area.
Equipment performing GMDSS functions must be simple to operate and
(wherever appropriate) be designed for unattended operation.
Distress Alerts must be able to be initiated from the position from
which the ship is normally navigated (ie; the bridge).
EPIRBs are required to be installed close to, or capable of remote
activation from the position from which the ship is normally
navigated.
The SOLAS GMDSS regulations are structured such that all GMDSS ships
are required to carry a minimum set of equipment, with basically
more equipment being required the further the ship travels from
land.
The SOLAS GMDSS regulations do not make particularly easy reading -
a simplified version of the equipment required to be carried for
each sea area is detailed below.
Minimum requirements
GMDSS ships are required to carry the following minimum equipment:
A VHF radio installation capable of transmitting
DSC on channel 70, and radiotelephony on channels 16, 13 and 6. (see
Note 1).
One SART if under 500 GRT, 2 SARTs if over 500 GRT.
Two portable VHF transceivers for use in survival
craft if under 500 GRT, three if over 500 GRT.
A NAVTEX receiver, if the ship is engaged on
voyages in any area where a NAVTEX service is provided.
An Inmarsat EGC receiver, if the ship is engaged on
voyages in any area of Inmarsat coverage where MSI services are not
provided by NAVTEX or HF NBDP (see note 2).
A 406 MHz EPIRB
Note 1 - Voice watch is effectively required on channel 16 until
further notice.
Note 2 - in practice, this means that all GMDSS A3 and A4 vessels
are required to carry at least one Inmarsat C system.
Radio equipment - Sea
area Al
Every ship engaged on voyages exclusively in sea area A1 shall be
provided with the minimum equipment specified previously.
Radio equipment - Sea
areas A1 and A2
Every ship engaged on voyages beyond sea area A1, but remaining
within sea area A2, shall be provided with the minimum equipment
specified previously, plus:
An MF radio installation capable of transmitting
and receiving on the frequencies 2187.5 kHz using DSC and 2182 kHz
using radiotelephony; and
a DSC watchkeeping receiver operating on 2187.5
kHz.
The ship shall, in addition, be capable of transmitting and
receiving general radiocommunications using radiotelephony or
direct-printing telegraphy by either:
A HF radio installation operating on working frequencies in the
(marine) bands between 1,605 kHz and 27,500 kHz. (This requirement
is normally fulfilled by the MF equipment referred to earlier - all
GMDSS MF transceivers also cover HF) OR
An Inmarsat ship station.
Typical GMDSS A2 ship station
Radio equipment - Sea
areas A1, A2 and A3
These vessels have two options to satisfy their GMDSS requirements.
The options allow a vessel to choose from the primary method to be
used for ship-shore alerting ;
Every ship engaged on voyages beyond sea areas A1 and A2, but
remaining within sea area A3 shall be provided with the minimum
equipment specified previously, plus either:
An Inmarsat C ship earth station :
An MF radio installation and 2187.5 kHz DSC watchkeeping receiver
(can be the same one as required for A2);
OR
An MF/HF radio installation capable of transmitting and receiving on
all distress and safety frequencies in the (marine) bands between
1,605 kHz and 27,500 kHz using DSC, radiotelephony and NBDP.
An MF/HF DSC watchkeeping receiver capable of maintaining DSC watch
on 2,187.5 kHz, 8,414.5 kHz and on at least one of the distress and
safety DSC frequencies 4,207.5 kHz, 6,312 kHz, 12,577 kHz or
16,804.5 kHz; at any time, it shall be possible to select any of
these DSC distress and safety frequencies
AND
Ships shall be capable of transmitting and receiving general
radiocommunications using radiotelephony or direct-printing
telegraphy by an MF/HF radio installation operating on working
frequencies in the (marine) bands between 1,605 kHz and 27,500 kHz.
This requirement is normally fulfilled by the addition of this
capability in the MF/HF equipment referred to earlier - there is no
MF only equipment made.
Typical GMDSS A3 ship station
Radio equipment - Sea
areas Al, A2, A3 and A4
In addition to carrying the equipment listed previously, every ship
engaged on voyages in all sea areas shall be provided with:
An MF/HF radio installation as described earlier
An MF/HF DSC watchkeeping receiver as described earlier
In addition, ships shall be capable of transmitting and receiving
general radiocommunications using radiotelephony or direct-printing
telegraphy by an MF/HF radio installation as described earlier.
Typical GMDSS A4 ship station
Confused ? Wait, there's more..!
Means of ensuring availability of ship
station equipment
Regulation 15 of the SOLAS GMDSS regulations defines 3 methods to
ensure availability of GMDSS equipment at sea;
At sea electronic maintenance, requiring the
carriage of a qualified radio/electronic officer (holding a GMDSS
First or Second class Radio-Electronics Certificate) and adequate
spares and manuals;
Duplication of certain equipment; or
Shore based maintenance
Ships engaged on voyages in sea areas A1 and A2 are required to use
at least one of the three maintenance methods outlined above, or a
combination as may be approved by their administration. Ships
engaged on voyages in sea areas A3 and A4 are required to use at
least two of the methods outlined above.
And of course what all that means is that 99% of A3 GMDSS ships,
along with probably 100% of A1 and A2 GMDSS ships do not opt for at
sea maintenance - they either duplicate the equipment and use shore
based maintenance (for A3 ships), or use shore based maintenance
only (A1 and A2 ships).
Equipment to be duplicated for area A3
vessels
GMDSS ships operating in A3 areas are required to provide the
following duplicated equipment;
Two complete VHF installations (including DSC), and either;
Two complete Inmarsat C systems and one MF radio system, or;
One complete Inmarsat C system and one complete MF/HF radio system
(including a scanning DSC receiver and NBDP equipment).
Many GMDSS ships opt for the latter option (1 Inmarsat C and one
MF/HF DSC system), on cost grounds. Unfortunately, this has proven
to be one of the underlying causes of the present extremely high
false alerting rate on some GMDSS systems.
Power supply
requirements
GMDSS equipment is required to be powered from three sources of
supply:
ship's normal alternators/generators;
ship's emergency alternator/generator (if fitted); and
a dedicated radio battery supply.
The batteries are required to have a capacity to power the equipment
for 1 hour on ships with an emergency generator, and 6 hours on
ships not fitted with an emergency generator.
The batteries must be charged by an automatic charger, which is also
required to be powered from the main and emergency generators.
Changeover from AC to battery supply must be automatic, and effected
in such a way that any any data held by the equipment is not
corrupted (ie: "no break").
Operator
qualifications
There are a number of different types of GMDSS qualifications, as
follows:
First Class Radio-Electronic Certificate;
Second Class Radio-Electronic Certificate; and
GMDSS General Operator's Certificate
The First and Second Radio-Electronic Certificates are diploma and
associate diploma level technical qualifications. They are designed
for Ship's Radio-Electronic Officers, who sail on GMDSS ships which
use the option of at-sea electronic maintenance.
The GMDSS General Operator's Certificate is a non-technical operator
qualification, designed for Navigating Officers.
The GMDSS General Operator's Certificate is normally awarded after a
ten day course and examination.
Let's have a look at Digital Selective Calling
(DSC)
DUNSTAN AND ASSOCIATES
The GMDSS specialists