Modern ships rely on Bridge navigation electronics and the GMDSS (Global Maritime Distress and Safety System) to ensure safe navigation and emergency communication anywhere in the world. Failure of this equipment can stop a vessel from sailing, cause Port State Control detention, or create real safety risks.
This article explains the main bridge, GMDSS equipment and provides practical troubleshooting methods used onboard.
1. Bridge Navigation Equipment – Overview
Typical bridge electronics include:
- Radar (X-band / S-band)
- ECDIS
- Gyrocompass & repeaters
- Autopilot
- Speed log
- Echo sounder
- AIS
- BNWAS
- GPS receivers
- Navtex
- VDR / S-VDR
Most of these systems are interconnected through NMEA 0183 / NMEA 2000 / Ethernet networks and depend on:
- 230V AC bridge supply
- 24V DC emergency supply
- Gyro heading
- GPS position/time
- Ship LAN / serial data
When one fails, several alarms may appear at once.
2. GMDSS Equipment – Overview
The GMDSS radio room normally includes:
Mandatory Equipment
- MF/HF radio - Long-range distress & communication
- VHF DSC radio - Short-range distress
- Inmarsat terminal - Satellite distress & safety
- EPIRB - Automatic distress beacon
- SART / AIS-SART - Survival craft location
- Navtex receiver - Maritime safety info
- Portable VHF radios - Survival craft communication
- GMDSS batteries & charger - Emergency power
All GMDSS equipment must operate from main + emergency power + dedicated batteries.
3. Most Common Failure Causes (Real Ship Experience)
Across fleets, 80% of bridge/GMDSS faults come from:
- Power supply problems
- Antenna / coax cable faults
- Corroded connectors
- Software freezes
- Incorrect configuration after blackout
- Failed backup batteries
- Data network failures (gyro/GPS missing)
Always check the simple things first.
4. Golden Troubleshooting Principle
When bridge equipment fails, always check in this order:
- Power
- Cables
- Sensors / inputs
- Settings / software
- Hardware modules
This prevents wasting hours.
5. Power Supply Troubleshooting
Typical Symptoms
- Equipment dead
- Random rebooting
- Dim display
- Multiple alarms after blackout
Checks
Step 1 — Verify supply sources
Check:
- Main switchboard breaker
- Emergency switchboard breaker
- UPS output
- Local power supply units
Measure:
- 230V AC
- 115V AC (some radars)
- 24V DC bridge supply
Many bridge failures are simply tripped breakers after power blackout.
Step 2 — Check fuses and internal PSUs
Common failures:
- Radar display PSU failure
- ECDIS PC power supply
- VHF internal fuse blown
Always inspect:
- Burn smell
- Overheated PSU
- Fan not running
6. Antenna & RF Problems (Very Common in GMDSS)
Symptoms
- Poor TX/RX range
- High SWR alarm
- DSC test fails
- No GPS signal
- Inmarsat cannot log in
Causes
- Salt corrosion in coax connectors
- Water inside antenna cable
- Broken antenna ground
- Lightning damage
- Loose coax after mast work
How to Check RF System
Visual inspection
Check:
- Antenna base
- Coax connectors
- Deck glands
- Rust / green corrosion
Coax cable test
Measure continuity:
- Inner conductor → OK
- Shield → OK
- No short between them
If short circuit → cable water ingress.
7. GPS & Gyro Data Loss
Bridge equipment heavily depends on:
- GPS position/time
- Gyro heading
If GPS or gyro fails → multiple alarms appear everywhere.
Typical alarms
- Radar: “No heading”
- AIS: “No position”
- ECDIS: “Position lost”
- Autopilot: “Gyro fail”
Troubleshooting
Check NMEA signal distribution:
- Verify GPS receiver working
- Check NMEA splitter / buffer
- Check serial cables
- Restart data distribution unit
One faulty NMEA buffer can stop the entire bridge.
8. Radar Troubleshooting
Radar not transmitting
Check:
- Scanner rotation
- Magnetron warm-up
- Waveguide moisture
- Safety interlock switches
- TX fuse
If scanner rotates but no picture → likely transmitter unit fault.
Radar stops rotating
Possible causes:
- Scanner motor capacitor failure
- Gearbox seized
- Slip ring worn
- Water ingress
9. VHF / MF-HF Radio Troubleshooting
Cannot transmit
Check:
- Antenna tuner (MF/HF)
- VSWR alarm
- PTT handset cable
- Microphone failure
Cannot receive
Check:
- Squelch setting
- RF gain
- Antenna switch
- Speaker failure
10. Inmarsat Terminal Faults
Cannot log into satellite
Check:
- GPS input (mandatory!)
- Ship position entered
- Antenna blocked by crane/mast
- Gyro input (for stabilization)
Very often failure is due to missing GPS signal.
11. EPIRB / SART Issues
Common problems:
- Expired battery
- Hydrostatic release expired
- Self-test fails
- Antenna cracked
Always check expiry dates:
- Battery: every 5 years
- HRU: every 2 years
PSC frequently detains ships for this.
12. GMDSS Battery System Troubleshooting
Typical faults
- Battery not charging
- Low capacity alarm
- Charger failure
- Battery swollen
Checks
Measure:
- Charger output voltage
- Battery voltage under load
- Electrolyte level (lead-acid)
A weak battery may show normal voltage but fail under load test.
13. After Blackout – Common Issues
After ship blackout expect:
- GPS reset to default
- Radar time wrong
- AIS MMSI missing
- Inmarsat requires re-login
- Network switches frozen
Always perform:
- Full power reset of bridge network
- Check date/time sync
14. Preventive Maintenance Tips
- Monthly GMDSS test
- Inspect antennas every 3 months
- Tighten RF connectors yearly
- Test batteries every 6 months
- Keep bridge electronics ventilated
- Backup ECDIS & radio settings
Preventive maintenance saves huge troubleshooting time.
Bridge and GMDSS systems are interconnected networks, not standalone devices. Most failures originate from:
- Power supply issues
- Antenna/cable faults
- Missing GPS/Gyro data
- Battery problems
Systematic troubleshooting — starting from power and working toward equipment — is the key to fast fault finding onboard.
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