Williamson, Anderson and Scharnow turns
1The lesson in plain words
Larger, faster vessels use set turns to get back to a person. Each fits a different situation: seen falling, at night, or discovered missing later.
Why set turns
A ship or fast motor yacht covers a long distance before it can turn back. A rehearsed turn gets it back to the person, or along its wake, the disturbed water behind it, without guesswork. The IAMSAR Manual Volume III, carried by ships, describes three. These are teaching angles; use your vessel’s practised procedure and safe speed, as handling varies.
Williamson turn
Put the rudder hard over, fully towards the side the person fell. After the heading has changed about 60°, put it hard over the other way. When the heading is about 20° short of the reciprocal, the opposite course, put the rudder midships (centred) and steady on the reciprocal. The ship returns towards its previous track. It helps at night or in poor visibility, but is slow; drift may move the casualty away from the return track.
Anderson turn
Also called the single turn. Put the rudder hard over to the casualty’s side and keep turning. After about 250° of heading change, put the rudder midships and begin your vessel’s practised stopping manoeuvre, allowing for headway. It is the fastest turn and suits ships that turn tightly when the person is in sight. Straight-line approach is harder to judge.
Scharnow turn
Rudder hard over; after about 240° of change, hard over the other way; about 20° short of the reciprocal, midships. It brings the ship back into her wake in less distance than the Williamson, but not for immediate action: use it after a delay when the elapsed time since the fall is known and the casualty is well astern.
Boutakow in Spain
Spanish PER and Patrón de Yate courses teach the curva de Boutakow, the same idea as the Williamson: rudder hard over to the casualty’s side, then hard over the other way after about 70°, until on the reciprocal. Exam questions use that figure.
2Key data
- Williamson
- Hard over; at 60° reverse; 20° short of reciprocal, midships
- Anderson
- At ~250°: rudder midships; begin planned stopping manoeuvre
- Scharnow
- Hard over; at 240° reverse; 20° short of reciprocal, midships
- Boutakow (Spanish PER)
- Like Williamson, reversing the helm after about 70°
3Key points
- 1
For a witnessed fall, turn towards that side; for delayed discovery, choose the safe turning side.
- 2
Williamson: return along your previous track; useful at night or in fog; slow.
- 3
Anderson: single turn, fastest, person in sight, tight-turning ship.
- 4
Scharnow: delayed action with elapsed time known and casualty well astern; never immediate action.
- 5
Spanish exams: Boutakow, helm reversed at about 70°.
4Frequent mistakes
Wrong: The Scharnow turn is best when you see the person fall.
Right: Use Scharnow after a delay only when the elapsed time since the fall is known and the casualty is well astern. Seen at once: Anderson or Williamson.
Wrong: The Williamson turn is the quickest way back.
Right: It is the most reliable for finding the wake at night, but it is slow. The Anderson is faster.
5Practice case & exam keys
On a 25 m motor yacht at 18 knots on a dark night, a guest goes over the port side. The watch sees the splash but loses sight of the person at once. Which turn do you use?
Show the answer
A Williamson turn: rudder hard to port, at about 60° of heading change hard to starboard, then midships about 20° short of the reciprocal. It returns towards your previous track; keep searching because the person may have drifted. Maintain lookouts with a searchlight.
Exam keys
- Williamson: hard over to casualty side, reverse at 60°, steady on reciprocal; night and poor visibility.
- Anderson: single turn of about 250°; fastest; person in sight.
- Scharnow: delayed action with elapsed time known and casualty well astern; never immediate action.
- Boutakow (Spanish PER): reverse helm at about 70°.
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