Sailed4seas的部落格

FOR A VESSEL TURNING TOO FAST, THE COUNTER MEASURES WILL BE :

• REDUCING THE RUDDER ANGLE BEEN USED.
• MISHIP THE RUDDER TO NEUTRALIZE THE RUDDER EFFECT
• USING THE COUNTER RUDDER TO STOP OR SLOW THE SWING.
• USING FULL COUNTER RUDDER TO INCREASING THE CHECKING.
• USING THE RESERVED ENGINE SPEED TO MAXIMUM THE CHEKING.

IT SHOULD BE CLEAR NOW THAT THE RUDDER ANGLE SHOULD BE USED FIRST TO SLOW DOWN THE TURNING. IN THIS TURNING TOO FAST SITUATION, WE HAVE MORE WIDE RUDDER ANGLE RANGE FROM EASE THE HELM TO MIDSHIP TO COUNTER RUUDER. THESE MEASURES ARE ALSO USED WHEN VESSEL HAVE FINISHED THE TURN BUT STILL CAN NOT STEADY ON THE NEW COURSE. WHEN WE USE THESE COUNTER MEASURES TO SLOW DOWN THE TURNING RATE, THE VESSEL IS STILL MOVING ALONG THE WATERWAY. AT THE CORRECT WOP, WE WILL HAVE TO CONTINUE THE TURN TO APPLY THE RUDDER EFFECT AGAIN. SO, THE TURNING IS A SERIES OF MANEUVERING TO AQUIRE THE SUCCESS TURN.

   THE COUNTER MEASURE FOR A VESSEL TURNING TOO SLOW WILL BE

WE CAN DERIVE SOME BASIC CONCEPT FROM THE FACTS ABOVE.

PREAMBLE

Second collision

If the collision risks exist in more than one vessel or the avoidance actions may lead to another close quarter situation, all the vessels have or about to have the collision risk should treat as one big vessel. Give-way vessel should take the actions to avoid all vessels at the same time well before all the risks become imminent. This is a prudent navigator practice.

Course change for multi targets in open water

In the heavy traffic waterway, the give-way vessel's large heading change may lead to another collision risk. The give-way vessel's action should be very cautious. In this situation, the collision risk may not involve in only one vessel. The action taken by the give-way vessel should clear all the collision risk once for all. The useful technical will regard all the vessels involved in the collision risk as one big vessel. The one has the shortest TCPA should regard as the big ship's bow and the one has more RB as the big vessel's stern. When the avoidance action been taken, the action should clear all the vessels at one single move. 

COLREG Rule 7 Risk of Collision (a) Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist. (b) Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plotting or equivalent systematic observation of detected objects. (c) Assumptions shall not be made on the basis of scanty information, especially scanty radar information. (d) In determining if risk of collision exists the following considerations shall be among those taken into account: (I) such risk shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change; (ii) such risk may sometimes exist even when an appreciable bearing change is evident, particularly when approaching a very large vessel or a tow or when approaching a vessel at close range.  

In 7(a) If there is any doubt such risk shall be deemed to exist. The point is mainly aimed to encourage the give-way vessel to take proper action to avoid the collision when other vessel’s bearing change is not obvious. It is interest to note that in a study from the aviation industrial of the so called mid air collision. There is a phenomenon called blossom effect. If the image of a target getting bigger and bigger, it means the risk of the collision is imminent. When the image augment is more than the bearing change, the OOW will confuse of the risk of collision. This is the time the rule 7(a) apply.   

 AFTERMYTH OF A COLLISION CASE