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The horizontal axis shows progressing time. 6 categories of actions make a line on the vertical axis. Marks are placed at the time. when the action in that category was done. ● shows action for the own ship, ◆ shows actions for the ship behind the own ship, ▲ shows action for the fishing boat in front of the own ship, and * shows action for the ship from opposite direction. × shows Communication with VTS. ○ shows Maneuvering on engine. These show actions over a 10 minutes period between 10 minutes before trouble and 10 minutes after trouble.
In case A from behaviour pattern I the operator carried out Lookout about fishing boat and the ship behind the own ship sufficiently. And he had Communication with the ship behind the own ship in early time to keep backward safety, and then also did Maneuvering to avoid the fishing boat in early time. After these early actions, the operator kept doing Lookout about backward and fishing boat, and Positioning.
Because of these ordinary actions, safety was kept. As a result, case A realized the safety with spare distance and time by not many Maneuvering. Therefore the wake of own ship and positional relationship with 2 other ship were natural shown as Fig.7. ● is own ship, ◆ is back ship, ▲ is fish boat.
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Fig.7
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Positional relation about case A from Behaviour pattern 1
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case A: -10min to 3min
In case C from behaviour pattern 2 the operator carried out Lookout about fishing boat and the ship behind the own ship insufficiently, compared with case A, though situation was similar with case A. As a result a lot of Maneuvering was needed to avoid fishing boat and to force backward ship's way in just after the Communication. This is an unsuitable situation.
Therefore when the operator did not have much capacity to react toward fishing boat due to a lot of Maneuvering, trouble happened. This unsuitable situation is shown as Fig.8.
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Fig.8
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Positional relation about case C from Behaviour pattern 2
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case C: -10min to 3min
In case E from behaviour pattern 3 the backward ship navigated from about 3 cables behind own ship, moreover, the operator carried out Lookout about fishing boat and the ship behind the own ship more insufficiently than case C.
And after trouble, the operator carried out Maneuvering for Engine-Stop without Communication, though it was very close with backward ship. And the operator did not the necessary procedure for rudder trouble.
As a result, the operator did not only the necessary procedure for rudder trouble but also no actions to keep safety before speed reduction and so on shown as Fig.9.
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Fig.9
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Positional relation about case E from Behaviour pattern 3
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case E: -10min to 3min
The worse achievement level is, the more unsuitable situation come.
Fig.10 Expanded Fault Tree
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