Ship Manoeuvring

 

Manoeuvres for rescue of person overboard

 

Ship Manoeuvres for a Man Overboard

The Round or Anderson Turn is a maneuver used to bring a ship or boat back to a point it previously passed through, often for the purpose of recovering a man overboard.

This turn is most appropriate when the point to be reached remains clearly visible. Both will require more time before returning to the point in question.

1. If the turn is in response to a man overboard, stop the engines.

2. Put the rudder over full. If in response to a man overboard, put the rudder toward the person (e.g., if the person fell over the starboard side, put the rudder over full to starboard).

3. When clear of the person, go all ahead full, still using full rudder.

4. After deviating from the original course by about 240 degrees (about 2/3 of a complete circle), back the engines 2/3 or full.

5. Stop the engines when the target point is 15 degrees off the bow. Ease the rudder and back the engines as required.

If dealing with a man overboard, always bring the vessel upwind of the person. Stop the vessel in the water with the person well forward of the propellers.

The Williamson Turn

John A. Williamson entered the US Navy as a seaman and later became the Commanding Officer of the USS England. As an instructor ashore, Williamson developed a series of turns used to bring a ship back on its own wake after a man fell overboard.Williamson recommended they teach the turn as a maneuver for man overboard recoveries during night and low visibility conditions.

Williamson after retirement wrote, ďIíve gotten letters and seen articles where people have been picked up using (the turn). I donít have a clue as to how many. I donít know whether itís ten or 5,000. I donít feel that thereís any glory to me though. Itís just something I came up with that turned out to be worthwhile. I donít think Iím due any glory for it, or any fame or anything like that.Ē


The principle behind the ďWilliamson TurnĒ is to return a ship to the exact location where a seaman fell overboard by using the shipís wake as a reference point. This requires that a ship first turn to starboard, followed by a turn to port that is concluded when the ship crosses its own wake.


This is the most efficient of all the turns till date.

The manoeuvre basically comprises of the following helm movements:

A wheel over of hard over on any side suitable

To maintain the helm until the course has altered by 60 degrees.

Once this is achieved the wheel is put hard over on the opposite side

The wheel is kept at hard over until about 20 degrees remain to bring the vessel to the reverse of original course, when the helm is put to amidships

Helm is used to ease the ship on to the reverse course. (It helps if the original wake of the ship can be seen)

 

 

 

This is the most efficient since without any navigational aid the ship would retrace her path and go up the course line.

Small deviations are to be allowed for the tide and current and wind effects. But overall is the best method to recover or to at least go over the path of the ship.

The above plot is an actual done on board a medium sized tanker and as can be seen there is very small deviation. Of course the positions were plotted by GPS fixes. But the position fixing was superfluous. (MOB position: Lat. 16˚36.2íN, Long. 082˚47.65íE)

Regarding which side to put the wheel over the first time, a lot has been said about putting the wheel over on the same side as the man overboard.

Actually the amount of time it takes for a man floating to pass the stern and the time it takes to raise the alarm and actually to put the helm over is so vastly different that the man overboard is very far behind the ship by the time the ship starts turning.

Please note in the case of any turning of the ship to recover a man overboard Ė it is assumed that the vessel is at sea speed. Since at a anchorage/ harbour the lowering of the lifeboat is much more convenient.

The Scharnow Turn

The Scharnow Turn is a maneuver used to bring a ship back to a point it previously passed through, often for the purpose of recovering a man overboard.

The Scharnow Turn is most appropriate when the point to be reached is significantly further astern than the vesselís turning radius. For other situations, an Anderson turn or a Williamson turn might be more appropriate.

 

Put the rudder over hard. If in response to a man overboard, put the rudder toward the person (e.g., if the person fell over the starboard side, put the rudder over hard to starboard).

After deviating from the original course by about 240 degrees, shift the rudder hard to the opposite side.

When heading about 20 degrees short of the reciprocal course, put the rudder amidships so that vessel will turn onto the reciprocal course.

If dealing with a man overboard, always bring the vessel upwind of the person. Stop the vessel in the water with the person well forward of the propellers.

NOTE: All of the above turns to rescue a person fallen overboard, the point to keep in mind is that the turns of every ship differs from the theory. Together with the current and wind the ship may not be actually over the position as required. As such a good look out Ė enough commonsense as to the drift and that a small head in a vast ocean with waves is very difficult to see. Even with the ship having retraced the path it may not always be possible to see a small head in the waters. The MOB marker may drift not always at the same rate as that of the person. SO good look out is very essential and good common seamanship.

Sequence of actions to take when a person is seen to fall overboard

Throw a Life Buoy with a self-igniting light towards the person in the water.

Send a lookout aft.

Rush to the manual call button and ring the alarm bell.

If a telephone or hand held radio is accessible then inform the Bridge watch-keeping officer

If above not available then go up on the bridge and inform the watch-keeping officer. Information should be as to which side the person fell and his identity.

Actions to take when a man-overboard report is received on the bridge

Assume that you are the watch keeper:

Put the helm on the same side to the person in the water

Throw down the Man overboard marker

Post a look out astern with binoculars

Note down the position of the ship by all possible means

Ring standby to the engine

Inform the Master

Ring the alarm bell for Emergency

Inform on the PA system that this is not a drill and that a person has fallen overboard.

Note down the wind direction and study the current direction

Ask for the rescue boat to be prepared

Depending on the instructions as laid down by the Master commence the Williamson turn

Once you see the MOB marker astern or if the original wake is noticeable, bring the vessel back on course

Inform all ships in the vicinity of the incident and send out a distress message

Once the vessel is on reciprocal course and the engines are ready for manoeuvring

Slow down and if the marker is visible head for it.

When very close to the MOB, stop engines and lower the RB.