Index of content

              chapter one : preamble

This chapter discuss the factor affecting the necessary skill which we should acquired for collision avoidance from the human factor engineering aspect. The skill came from practice, practice came from knowledge, knowledge came from case study. When a man under pressure the correct reaction came from long term memory.  The long term memory accumulated from good daily practice which constitute our skill in the emergency case. 

              chapter two : theory of collision

Introducing a useful definition of collision to cover all knowledge that are needed in collision avoidance. Two objects in the same place at the same time is a collision. The same place took some dimension in the space which is two ship's length. The same time is a time period which can get from two ship's length divided by ship's speed.  To avoid meeting other vessel in the same place need close observation of approaching vessel's bearing change. To avoid arriving at the same time with other vessel need reduce the ship's speed which is the speed difference that make the avoidance possible. Use this theory to prepare our voyage planning and review all the charts currently being used have any hot spot as the collision can be predicted. 

            chapter three : spatial awareness

Collision avoidance actions required by colreg is divided by three stage. Prepare ourselves for the last stage of collision risk. Spatial awareness give the reader the real ship we are handling, not just a point in radar plotting sheet or some symbol in the arpa screen. Three stage of turning process have its different usage when conducting the vessel to different purpose. The first stage is numb and blind-folded in ship's bow, but ship stern can have some side kick. Serpent swing need 4 ship's length to maneuver or should call double side-kicking. Imo visibility requirement is two ship's length or 500 meters whichever is less. Does this blind area imply the ship's incapability to react the target ahead ? The second stage of turning is used mostly in course changing which is 0.5 nautical mile ahead from the turning point. This 0.5 n.m. Distance is also known as point of no return which means once the vessel is getting closer than this distance, there are no way to turn back to open sea when approaching a breakwater entrance or a pilot station. The best way to approach is adjust to the correct course before 0.5 n.m. The final stage of turning is used for clearing the possible area of collision. The possible collision position of own ship is varied as the turning stage. 

            chapter four : timing lapse

The distance in the last stage of collision avoidance actions is 2-3 miles range between two vessel. This general guidance is for end-on and crossing vessel. Dtc/speed = tcpa. Range/relative speed= tcpa. The minimum dtc should be 7 ship's length in all meeting situation. Dtc/reduced speed=timing lapse. How many maneuvering room is allowable to oow by master order ? The effective distance for avoidance action by using rudder alone is 7 ship's length. The special maneuvering needed when dtc less than 7 ship's length is zigzag when ship has high initial speed. The first hard  over rudder used in zigzag has the definite influence on her final resting position. How to stop the vessel when main engine is break down ? When initial speed is low crash astern should be used to create some timing lapse. The knowledge of the vessel's movement when going astern. Stand by the bow thruster whenever the astern engine is using. Using the astern engine when ship's speed is high will not cant the bow away. Different initial speed need different techniques to create the timing lapse. 

           chapter five : risk of collision

This chapter challenge the myth of arpa and establish the skill of visual lookout. Visualizing the target bearing is by changing the true bearing of a target into a visual reference point on deck. By checking the target moving along the reference point will tell us the risk of collision of this target. The smallest dtc target is the first target we will collide with. For any vessel in the same range has the collision risk with own ship. 1: the faster ship has more wide range of collision risk. 2: the lesser rb to us, the shorter dtc (more dangerous). The concept of no care sector is hard to understand by merely wording in this paragraph. However, if you are not wise enough, better not to use it. The main ability to judge the target's range is composed of several signs of ship's movement, bow wave, splash, wake current in daytime and reflection of lights, lighting space, light glowing on the window in the night time. The most tricky part of lookout is in the night time. We need to know the limitations of human eyes and the proper use of arpa/radar setting to help us handle the situation. We summarized the ability of visual lookout should consist of 1. knowing the priority of target in question. 2. verify the distance of the target. 
3. make sure the risk of collision by rb. The last paragraph should be used when taking over the watch from relieved oow.

           chapter six : the art of ship handling

Last chapter we discuss about the proper setting of two different wave length radar for acquiring the dangerous target in the first sight. However, it is only useful when ship is sailing at steady course. When the ship's course is changing, the arpa data become unrealistic due to the swing momentum of own ship. Arpa data is useful only when the target is positive identified. This is the main weakness of the equipment when we need it most in emergency case. Cutting out the unnecessary swing as much as possible to steady the vessel's heading is vital for assessing of the risk of collision. The art of turning course and care of using the rudder should be the basic training of any oow. How to handle a full rudder turning ? What precaution should be bear in mind ? In the close range crossing situation, the angle of blow need take into consideration in avoidance actions which is different from the usual action we take when two vessel still have ample distance away. It is in the stage (ship turning in a steady rate in 1.5 to 2 sl advance) the rudder should reduce to midship to check the turning rate of the vessel. Like the area of collision, the collision course is not only one heading we steered. It's a sector.  Create one ship's length sea room to avoid the last minute drastic maneuvering. 

          chapter seven : stand-on vessel's measure

The distance appropriate for stand-on vessel taking the best aid to avoid the collision is 3 miles by mca recommendation and 2 miles by dailan maritime college's study. The effectiveness of our avoid action is largely depend on the dtc that is how many maneuvering room we have. For the same range vessel, different meeting situation will create different maneuvering requirement. The success of an avoidance actions can  be described as follow : the amount of true bearing change  should be more than the first observed rb. At close range, the bearing change can not take as the only standard for access the risk of collision, watch out the distance change is more important than the bearing change. It is the stage of our turning that will make the big difference in the angle of blow. The true bearing increase of give way vessel have to more than the rb to cross our bow. For those give way vessel have to pass our stern, it's rb should be more than 180 degree. When two ship meet each other, the fast ship have more effective means to avoid the collision. The possible area of collision is two sl.  For clearing the possible area of collision  
the target's tb have to change over 5 degree before 4 n.m. Range.  
The target's tb have to change over 7 degree before 3 n.m. Range. 
The target's tb have to change over 10 degree before 2 n.m. Range. 
The target's tb have to change over 20 degree before 1 n.m. Range. 

The effectiveness of the give way vessel's avoidance actions have to wait for the give way vessel's course or speed have steadied. Then we could check the true bearing change is enough or not in the specific distance away. If the give-way vessel cannot clear our bow, own ship have to take some action. The best aid will be take the same/reciprocal course as give-way vessel. The confidence of stand-on vessel to take avoidance action is coming from the suitable distance away. The suitable distance is enough maneuvering space for stand-on vessel which is at least 6 sl to the poc. If the give-way vessel's bow is going to hit stand-on vessel's midship or stern section, the stand-on vessel should alter course to port side to swing out the aft part of vessel. The correct timing for the stand-on vessel to alter course to port side is 2-3 sl to the collision point. In another word, the dtc is 2-3 sl.

         chapter eight : actions to take

Give-way vessel's measure is consisted of course change, speed reducing or both. Course change to where ? Speed reducing by what means ? What to do in a canal ? When dangerous target come out from one mile range ? The distance judgment in short range ? What about the rb or tb change means in turning ? What kinds of danger involved in a avoidance action ?

                     summary

 refuse to change is the first mantle sign of aging. As always, the learning obstacle for senior seaman is complacency which i should quote as below :

When anyone asks me about how i can best describe my experience of nearly forty years at sea, i merely say uneventful. Of course there have been winter gales and storms and fog and the like, but in all my experience, i have never been in an accident of any sort worth speaking about. I have seen but one vessel in distress in all my years at sea...... I never saw a wreck and have never been wrecked, nor was i ever in any predicament that threatened to end in disaster of any sort.

The presentation of captain e. J. Smith made by 1907. five years later, captain loss his and other 1500 lives together with the unsinkable vessel " titanic". 

Complacency come from many aspect including the knowledge, experience, skill you already have. I have not retired from the sea post as any reader about to sea. Hope all these articles will not reduce our vigilance.