Advanced Scenario Check: Electronics

A fictional yacht is approaching a narrow entrance at night. GNSS and the copied route are suspect; one AIS target has stale manual dimensions; radar shows a second unlabelled echo; depth is trending shallower; and the route's cross-track alarm is set wider than the safe corridor. The safe decision cannot be found by choosing one preferred screen.

Start by closing the route whose position and alarm assumptions are no longer valid. Keep the yacht in the pre-briefed sea-room or holding area, maintain safe speed and lookout, and separate collision assessment from route troubleshooting. AIS remains supplementary; radar and visual or auditory evidence still require their own systematic assessment.

Rebuild position from the last accepted fix and checked observations with different failure modes. Recalculate the clearance and contour settings from the vessel and current assumptions, then inspect every route leg and turn at useful scales. If the entrance cannot be reopened with a coherent picture and usable margin, divert or wait rather than forcing the original plan.

This written scenario rehearses reasoning, not practical competence. A real decision depends on the fitted equipment, vessel manoeuvrability, tide, charted dangers, traffic, visibility, crew and skipper judgement.