Module 19 - Electronic Navigation
Failure Planning and Redundancy
What you will learn
Design and rehearse a black-screen fallback by independent failure domains rather than by counting spare displays.
A backup is useful only when it survives the intended failure, is current and accessible, and the crew can operate it before the primary system is lost.
A Yachtmaster passage plan should include what happens if the plotter, GNSS, radar, AIS, depth sounder, log, or charging system fails. The answer may be paper chartwork, backup handheld GPS, visual pilotage, heaving-to, anchoring, diverting, or waiting for daylight.
Power management matters. Many electronic failures are actually electrical failures: flat batteries, poor charging, corroded connections, blown fuses, or water ingress. Know where the breakers are, keep handheld backups charged, and make sure essential navigation can continue if the main plotter goes dark.
Test the black-screen plan
The main plotter, AIS overlay and autopilot route all disappear when one navigation breaker trips at night.
1. Name the failure
Identify which power, antenna, sensor, network, chart and route dependencies have been lost.
2. Protect the vessel
Move to the briefed safe heading, speed, sea room or holding plan before diagnosis.
3. Take over
Use a current charting method and independent position, heading, depth and power paths.
4. Demonstrate
Have the crew perform the changeover and state the next fixing and call-the-skipper limits.
Sense check: A charged tablet is not an independent position backup if it still receives the failed or suspect GNSS data and copied route.
Common mistake or limitation
- A second display on the same power, sensor or network may fail with the primary display.
- A backup chart or device that is out of date, inaccessible or unfamiliar is not ready for immediate use.
- Restoring power does not prove that the original navigation data are trustworthy.
- A written failure plan is weaker than a demonstrated crew changeover.
Recap
- Plan redundancy by sensor, power, network, chart and human-operation failure domains.
- Protect the vessel before diagnosing the electronics.
- Keep backup data current, accessible and ready for immediate use.
- Rehearse the black-screen takeover with the actual crew and fitted equipment.
Optional quick check
Section 10 of 18
Which evidence best shows that the electronic-navigation backup is ready?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
Continue studying Electronic Navigation
This public lesson is part of Revision Module 19. Full revision access adds the guided Learn, Practise and Test flow, flashcards and revision progress.