Question 1

What is the difference between a Williamson Turn and a Scharnow Turn, and when would each be used?

Accepted Answer

A Williamson Turn returns the vessel to the original track and position where the turn began (e.g. for a man overboard recovery shortly after the event), whereas a Scharnow Turn brings the vessel back along its original track but displaced astern of the position where the turn was initiated, and is more suitable when significant time has elapsed since the person/object went overboard Both are turning manoeuvres used to return a vessel to its previous track, most commonly associated with man overboard recovery, but they suit different circumstances. The Williamson Turn involves an initial turn away followed by a turn in the opposite direction through a larger angle, bringing the vessel back onto its original track heading in the reciprocal direction, arriving close to the position where the turn began — useful when the response is immediate. The Scharnow Turn is similar but uses different turn angles based on the vessel's turning characteristics, resulting in the vessel returning to its original track but at a point well astern of where the turn started — making it more suitable when there has been a delay before initiating recovery, since the person overboard will have been left further astern.

Question 2

You're preparing a passage plan for a coastal leg in a yacht drawing 3.2m. At one point the chart shows a least depth of 3.8m at chart datum. What MUST you check before finalising this leg?

Accepted Answer

The tidal height at the time of transit to confirm sufficient under-keel clearance Charted depths are referenced to chart datum (often LAT), so you must add the predicted tidal height for your transit time to get the actual depth, then compare to your draft plus a safety margin to confirm UKC.

Question 3

During your watch the ECDIS gives a "safety contour crossing" alarm. What is the correct response?

Accepted Answer

Assess the situation against the planned route and charted depths, take action to maintain safe water, and inform the Master if there is any doubt A safety contour alarm indicates the vessel may be approaching water shallower than the set safety contour. It must be investigated against the route and charted information, with avoiding action taken and the Master informed as appropriate — never simply silenced.