Question:   In a recent man-overboard situation, the Carnival Destiny was said to have made an abrupt right turn followed by a Williamson Turn.

Can someone diagram or describe (or both) a "Williamson Turn" please. During the past multi-decades I have been a passenger aboard many troopships, and they usually practiced recovery of "man overboard" at least once a voyage. But the term "Williamson Turn" is alien to me. It appeared to me they simply practiced the "classical naval manouver!"

Details?
(courtesy of Robert Ryan)

Answer: Different man-overboard manoeuvres may be required, depending upon the situation prevailing and the type of ship involved.

There are three basic situations:

1. "Immediate action" situation: Casualty is noticed on the bridge and action is initiated immediately;
2. "Delayed action" situation: Casualty is reported to the bridge by an eye witness and action is initiated with some delay;
3. "Person missing" situation: Person is reported to the bridge as "missing".

When a ship makes full speed ahead, the following three standard manoeuvres are used:

1. Single turn (270º manoeuvre): Rudder hard over (in an "immediate action" situation, only to the side of the casualty); after deviation from the original course by 250º, rudder to midship position and stopping manoeuvre to be initiated.
   
2. Williamson turn: rudder hard over (in an "immediate action" situation, only to the side of the casualty); after deviation from the original course by 60º, rudder hard over to the opposite side; when heading 20º short of opposite course, rudder to midship position and ship to be turned to opposite course.
   
3. Scharnow turn (not to be used in an "immediate action" situation.): rudder hard over; after deviation from the original course by 240º, rudder hard over to the opposite side; when heading 20º short of opposite course, rudder to midship position so that ship will turn to opposite course.