Sailed4seas的部落格

Ex 06-03

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 00 seconds exercise time lapsed:
  Ownship speed is 19.3 knots which decreased from 21.0 kts with engine output reduced from one minute before to 50%. 
  Ownship course had altered 4.0 degrees starboard side to 069.3 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 1.7 knots over 1 minute’s time. (sighted)
  • Ownship speed vector is 9.6 cables long now. (known by 19.3 knots speed)
• One crossing vessels at starboard side seems OK(yellow square). (sighted: passing after three 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 vector) have collision risk with ownship after 5 minutes. (sighted)

• One crossing vessels at starboard side (yellow vector) will pass ownship bow after 4 minutes. (sighted)
• Ownship will arrive collision point after 5 minutes. (sighted)
• Ownship will arrive one minute later than crossing vessel with yellow vector. (sighted)
• Ownship alter course 4.0 degrees starboard side to 069.3 degrees is moving collision point to starboard side along target vessel’s speed vector. (sighted with first picture)
• Course change is to shift collision point. (Statement)
• Speed reduction is to arrive collision point later. (statement)
• One crossing vessels at starboard side will pass ownship bow after 2 minutes. (sighted)
   

• After 3 minutes 00 seconds exercise time lapsed:
  Ownship speed is 16.0 knots which decreased from 19.3, 21.0 kts with engine output reduced from one minute before to 50%. 
  Ownship course had altered 2.0 degrees port side to 067.2 degrees from 069.3, 065.3 degrees with Port side rudder cycling in last 2 minutes. 
  The situational awareness in 3 minutes speed vector is:
  •    Ownship had not reduced speed immediately. (sighted)
  •    Speed reduces 3.3 knots over last minute. (sighted )
  • Ownship engine output had not further reduced but speed dropped sharply. (sighted)
  • Speed reduction rate is double than one minute before due to rudder cycling. (sighted)
  • Speed reducing rate of 3.3 knots per minute is very good for collision avoidance. (skill by knowledge)
  • Ownship speed vector is 8 cables long now. (known by 16.0 knots speed)
  • Speed vector lengths shorten 1.6 cables per minutes due to speed reduction. (sighted)
  • 1.6 cables is 296.3 meters or about 300 meter. This 300 meters is about one ship’s length. (truth)
  • Ownship create this 300 meters per minute is decisive inside collision square to avoid target vessel one ship length. ( Statement)
  • Ownship had calculated all these exercise to find proper digital value to guide us in collision avoidance. (statement)
  • Ownship had seen speed reduction rate about 1.5 - 2 knots per minute by reducing engine output only which is not enough. (statement)
  • Speed reduction rate 2 knots per minute can create 185 meters only. (Statement)
  • 185 meters is enough for a small vessel but not enough for a large vessel in collision square.(statement)) 
• 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 faster. (skill by comparing vector length)

Change speed vector length to 6 minutes is not necessary, the situation awareness is

•   One crossing vessels at starboard side will pass ownship bow after 3 minutes at very close range. (sighted)

• One crossing vessels at starboard side had altered course to port side to pass ownship stern. (sighted)
• Ownship alter course 2.0 degrees port side to 067.2 degrees is the effect of rudder cycling. (sighted)

After 4 minutes 00 seconds exercise time lapsed:
Ownship speed is 14.3 knots which decreased from 16.0, 19.3, 21.0 kts with engine output reduced from one minute before to 50%. 
Ownship course had altered 2.0 degrees port side to 065.8 degrees from 067.2, 069.3, 065.3 degrees with Port side rudder cycling in last 3 minutes. 
The situational awareness in 3 minutes speed vector is:
•    Speed reduces 1.7 knots over last minute. (sighted)

• Ownship engine output had not further reduced but speed dropped slowly by rudder cycling. (sighted)
• Rudder cycling is not medicine for all. Speed reduction by rudder cycling has it bottom line which decided by engine output. (statement) 
• Speed reducing rate of 1.7 knots per minute is no good for collision avoidance. (skill by knowledge)
• Ownship speed vector is 7.1 cables long now. (known by 14.3 knots speed)
• Speed vector lengths shorten 0.9 cables per minutes due to speed reduction. (sighted)
• 0.9 cables is 167 meters. (truth)
• Ownship create this 167 meters per minute is not decisive inside collision square. ( Statement)
• Ownship had not further reducing engine output only playing with hard rudder angle is not enough. (statement)
• 185 meters is enough for a small vessel but this one is big.(statement)) 

• One crossing vessels at starboard side is about to pass ownship bow. (sighted: passing after 0.5 minutes)

• 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)
• One crossing vessels at starboard side will pass ownship bow after 2 minutes at very close range. (sighted)
• One crossing vessels at starboard side had altered course to port side to pass ownship stern. (sighted)
• Ownship had used “Hard Starboard” 30 seconds to start the starboard Turning with no effect.(sighted)

After 5 minutes 15 seconds exercise time lapsed:
Ownship speed is 14.3 knots over last minutes, no further reduced. 
Ownship course had altered 10.0 degrees starboard side to 075.6 degrees from 065.8, 067.2, 069.3, 065.3 degrees with bold rudder angle. 
The situational awareness in 3 minutes speed vector is:
•    Speed reduces had stopped in last minute. (sighted)

• Ownship engine output had not further reduced but speed did not dropped by hard over rudder. (sighted)
• Speed reducing rate of 0 knots per minute is no good for collision avoidance. (skill by knowledge)
• Ownship had not further reducing engine output only playing with hard rudder angle is not enough. (statement)

• One crossing vessels at starboard side had passed ownship bow. (sighted)

• One overtaken vessel at starboard side is about same speed. (skill by comparing vector length)
• One overtaken vessel at port side is faster. (skill by comparing vector length)
• One crossing vessels at starboard side is dead ahead and ownship will arrive three minutes later. (sighted)
• One crossing vessels at starboard side had altered course to port side not to enter traffic lane. (sighted)
• Ownship course had altered 10.0 degrees starboard side to 075.6 degrees had shifted original collision point(yellow square) to target vessel’s astern(orange square) smoothly. (sighted)

The moral of this exercise is

1. “To allow each vessel of three minutes passing time lapse for safety allowance”.
2. Speed reducing rate of 3.3 knots per minute is very good for collision avoidance.
3. Speed reduction by rudder cycling has it bottom line which decided by engine output.

End of Ex 06-03