Carriage requirements and functional elements
Functional elements and carriage
SOLAS IV requires ships to have equipment for six functions: distress alerting, SAR coordination, locating, MSI reception, general radiocommunications and bridge-to-bridge communications. Equipment must be type-approved and surveyed. Carriage depends on sea area and ship type. A1 needs VHF DSC and VHF radiotelephony; A2 adds MF DSC/radiotelephony; A3 adds Inmarsat or HF; A4 requires HF. All areas need MSI reception (NAVTEX or EGC), a 406 MHz EPIRB, radar SART(s), and reserve power. The distress alert must be initiated from the navigation bridge, with a distress panel/alarm and an alarm system.
Power and duplication
There must be a reserve source of energy independent of the main and emergency generator, capable of supplying VHF and at least one other distress alerting radio, plus emergency lighting. Capacity is 1 hour if the emergency generator supplies the GMDSS, otherwise 6 hours; check the ship's certificate and battery log. Duplication is not universal: in A1–A2, duplication may be by a second VHF/MF set, while A3/A4 need additional capability.
Worked example
During an inspection a cargo ship in A2 has a VHF DSC, an MF/HF DSC set, a NAVTEX receiver and a 406 EPIRB, but the reserve battery only feeds the VHF. Reasoning: the reserve source must also feed one other radio capable of distress alerting-here the MF/HF set. The fit is deficient even though the main equipment looks complete.
Traps
An EPIRB does not replace the ship's distress alerting radio. A SART is for locating, not alerting. Do not count a handheld VHF as the required reserve source. Check that the reserve battery is actually connected and tested, not just present.