Sailed4seas的部落格

Ex 06-04

Ownship speed is 21.0 Knots and course is 065.3 degrees at beginning. 
The situational awareness is:
•    With three minutes vector length in 21.0 Knots, this vector is about 10 cables distance as above. (skill by knowing  three minutes run)
•    Ownship has three crossing vessels at starboard side, situation unknown. (sighted)
•     Three crossing vessels at starboard side, distance unknown. (sighted)

• One overtaken vessel at starboard side has slower speed. (skill by comparing vector length)
• One overtaken vessel at port side has slower speed. (skill by comparing vector length)

By change speed vector length to 6 minutes, the situation awareness is

•   Two crossing vessels at starboard side have collision risk with ownship. (sighted)
•   Collision with green vector vessel first then red vector one. (sighted)

• Collision point is almost coincided. (sighted)
• One crossing vessels at starboard side have no collision risk with ownship. (one minute later)

After 2 minutes 31 seconds exercise time lapsed:
Ownship speed is 18.5 knots which decreased from 21.0 kts with engine output reduced to 65% from beginning and 30 seconds ago to 43%. 
Ownship course had altered 4.4 degrees starboard side to 069.7 degrees from 065.3 degrees with starboard rudder ” in beginning and further port side rudder. 
The situational awareness in 3 minutes speed vector is:
•    Ownship had not reduced speed immediately. (sighted)
•    Speed reduces 2.5 knots over 2.5 minute’s time. (sighted)

• Speed reduction rate is 1.0 knot per minute, not enough. (sighted)
• Ownship speed vector is 9.3 cables long now. (known by 18.5 knots speed)

• One crossing vessels at starboard side seems OK. (sighted: passing after 1.5 minutes)

• One overtaken vessel at starboard side has slower speed. (skill by comparing vector length)
• One overtaken vessel at port side is about same speed. (skill by comparing vector length)

By change speed vector length to 6 minutes, the situation awareness is

•   One crossing vessels at starboard side (red circle) have collision risk with ownship after 5 minutes. (sighted)

• This vessel had altered course to port side. (sighted)

• One crossing vessels at starboard side will pass ownship bow after 3 minutes. (sighted)
• Ownship will arrive collision point after 4.0 minutes. (sighted)
• Ownship will arrive one minute later than crossing vessel with yellow circle. (sighted)
• Ownship alter course 4.4 degrees starboard side to 069.7 degrees is moving collision point to starboard side along target vessel’s speed vector. (sighted with collision point change)
• Course change is to shift collision point. (Statement)
• Speed reduction is to arrive collision point later. (statement)

After 3 minutes 30 seconds exercise time lapsed:
Ownship speed is 16.7 knots which decreased from 18.5, 21.0 kts with engine output reduced to 65% from beginning and 1.5 minutes ago to 43%. 
Ownship course had altered 6.1 degrees starboard side to 075.8 degrees from 069.7, 065.3 degrees with starboard rudder ” mostly. 
The situational awareness in 3 minutes speed vector is:
•    Ownship had not reduced speed immediately. (sighted)
•    Speed reduces 2.5 knots over 2.5 minute’s time. (sighted)

• Speed reduction rate is 1.8 knot per last minute, not enough. (sighted)
• Ownship speed vector is 8.3 cables long now. (known by 16.7 knots speed)

• One crossing vessels at starboard side is about to pass. (sighted)

• One overtaken vessel at starboard side has slower speed. (skill by comparing vector length)
• One overtaken vessel at port side is faster. (skill by comparing vector length)

By change speed vector length to 6 minutes, the situation awareness is

• One crossing vessels at starboard side had altered course to pass ownship stern. (sighted)

• One crossing vessels at starboard side will pass ownship bow after 1.5 minutes. (sighted)
• Ownship will arrive collision point after 4.0 minutes. (sighted)
• Ownship will arrive 2.5 minute later than crossing vessel. (sighted)

The 2.5 minutes delay consisted of two parts:

1. Ownship alter course 10.5 degrees starboard side to 075.8 degrees over last 3 minutes is not only factor to enough to change our situation. (sighted) With collision point shifted to starboard side(yellow leg), ownship can measure it length is about one third of three minutes target vessel speed vector ( one minute).
2. Ownship reduces speed 4.3 Knots in last 3.5 minutes.(sighted) With collision point shifted to our astern (light blue leg), ownship can measure it length is about half length of three minutes( 1.5 minutes).

• Course change is effective to shift collision point, not so effective in delaying collision time. (Statement)
• Speed reduction is effective in delaying collision time, not so effective to shift collision point. (statement)

While in restrict area, understanding why ownship needs decisive speed reduction in collision avoidance is utmost important.

After 4 minutes 30 seconds exercise time lapsed:
Ownship speed is 18.2 knots which increased from16.7 18.5, 21.0 kts with engine output increased to 100%. 
Ownship course had altered 16 degrees starboard side to 091.5 degrees from 075.8, 069.7, 065.3 degrees with “Hard Starboard” rudder. 
The situational awareness in 3 minutes speed vector is:
•    Ownship had increased speed immediately. (sighted)
•    Speed increase 1.5 knots over last minute is to stop the turning rate to starboard side. (sighted)

• Every rudder order is bold and abrupt which is a sure sign ownship don’t know how to control the vessel. (sighted)
• Engine output increased reckless is a sure sign of lack necessary knowledge. (sighted).

• All vessels are clear as no collision line crossed. (sighted)

After 5 minutes 48 seconds exercise time lapsed:
Ownship speed is 22.1knots which increased from18.2, 16.7 18.5, 21.0 kts with engine output increased to 100% over two minutes. 
Ownship course had altered 11.5 degrees port side to 080.0 degrees from 091.5, 075.8, 069.7, 065.3 degrees with “Hard Port” rudder. 
The situational awareness in 3 minutes speed vector is:
•    Ownship had increased speed quickly. (Sighted)
•    Speed increase 1.5 knots over last minute is to stop the turning rate to starboard side. (sighted)

• Ownship had conducted a starboard side turn of 26 degrees from 065 to 091 degrees. (sighted)
• Ownship maneuvering look ugly in this area. (Statement).

• All vessels are clear as one crossing vessel turning to ownship astern. (sighted)
• It is not its obligation to give way. Things could be worse otherwise.(statement)
•  

The moral of this exercise it

“Always beware of your turning rate and knowing what rate of turn could lead to no control of ownship”.

End of Ex 06-04