Appendix ③−４

Navigator Education - Navigation Questions and Answers
24

Vessel avoidance (question)

23

Vessel C
22

<180>
Co
Sp'd 16.0 kts
CPA 1.0
TCPA 40 mn.
B'g
<003>
Dist 22.6 miles

21

Information as shown in drawing at left obtained

20with ARPA.
Other vessels A and C evaluated as problematic.
(captains standing orders instructed as CPA 1.5

nautical miles or more)

19
18

Vessel B

17Co
<180>
Sp'd 20.0 kts
CPA 5.1
TCPA 24 mn.
B'g
<342>
Dist 16.4 miles

16

This relationship with other vessels occurs
comparatively frequently in the approaches toOsaka Bay, approaches to Tokyo Bay, approaches
to Ise Bay, and the Malacca Straits.
Often in Watch Level 1 sea areas.

151413
12
11
10Question

98

What navigation measures are

7

applicable to the vessel?

6

To the other vessel?

5

What action should the vessel

4take?

3Vessel A
Co<030>
Sp'd 15.6 kts
CPA 0.0
TCPA 60 mn.
B'g
<300>
Dist 9.0 miles<300> 9.'o2

Vessel
Co
Sp'd1

<000>
18 kts0-9

Appendix ③−５-8-7-6-5-4-3-2-1012

3456Navigator Education - Navigation Questions and Answers
25
24

Vessel avoidance (answer)

After 80 minutes

Vessel C

23<207>0.'7

22Answer
Navigation measures of vessel crossing course of Vessel A. Vessel is burdened vessel.
After 20 minutes, while turning to starboard, other vessel is requested to turn behind vessel.

21

After 71 minutes
20

After60 minutes

19

Although wish to turn to port as passing vessel, do not turn to port without communication on
VHF etc. to determine mutual intentions.

18

As shown on the left, the vessel is on a parallel course to the other vessel when Vessel A is

1773°

at 1.5 nautical miles on the port beam after 71 minutes.
The vessel then crosses the course of the other vessel 0.7 nautical miles ahead of it.
The other vessel is still too close at this distance, and the situation is therefore checked after
60 minutes,
and if necessary, another turn to starboard initiated, and the CPA must be expanded (CPA

After 60 minutes
After 20 minutes

16

monitoring the change in direction, crosses ahead of the other vessel.
Even after the vessel travels 3 nautical miles to starboard, the other vessel is eventually seen

<287>3.'1Vessel B

at a distance of 6 nautical miles.
When approximately 1 nautical mile further ahead, it returns to its original course, and while

Port abeam
1.5 nautical miles

After40 minutes

15Co <000>1413<293>6.'067°

12

set as 1 nautical mile or more).

11

After 40 minutes

Contact Vessel A and Vessel B on VHF to mutually determine intentions before turning toport to go behind Vessel A.

10Vessel C crosses ahead, and passes port-to-port. When commencing a starboard turn after

9

After20 minutes

20 minutes,
the distance to Vessel C is still 11 nautical miles. The course of Vessel C is therefore
crossed after 27 minutes.
On the other hand, Vessel A is required to maintain position relative to Vessel B. Since
Vessel B is travelling at 20kts,
it may be advisable to delay a starboard turn to cross ahead of Vessel B.

8Co <030>

60°<300>6.'0

After 27 minutes
76

After 20 minutes

54

Vessel A

When a number of vessels are passing, predict the relative positions after 30 minutes, 60minutes, and 90 minutes,

3<300> 9.'oand prepare a plan to determine which side each vessel will pass on.

210Vessel-9-8− 61 −-7-6-5-4-3-2-1

0123456

Appendix ③−６

Navigator Education - Navigation Questions and Answers
Vessels on opposing and same courses may approach each other in 25 - 30 minutes at adistance of 1 nautical mile under these conditions. Avoiding action is therefore necessary.
What avoiding action should be taken?

Radar and ARPA Information (Question)

Order of priority, and reasons, for paying attention to other vessels when taking avoiding
action.

Vector : 12 min.

21 miles18 miles15 miles12 miles9 miles

6 miles

3 miles

0 miles-3 miles-6 miles4.5miles4.5miles3.0milesＡＢ
CPA 0.2 mile
TCPA 30 min.
Co<087>
Sp'd 17.0 kts
B'g
<266>
Dist. 17.5miles

1.5miles

CPA 1.0 mile
TCPA 28 min.
Co<086>
Sp'd 12.0 kts
B'g
<269>
Dist. 14.0 miles

ＦＣＩ

CPA 4.0 mile
TCPA 15 min.
Co<088>
Sp'd 18.0 kts
B'g
<293>
Dist. 9.7miles

CPA 0.2 mile
TCPA 25 min.
Co
<270>
Sp'd 7.0 kts
B'g
<270>
Dist. 4.5miles

CPA 2.0 mile
TCPA 45 min.
Co
<267>
Sp'd 22.0 kts
B'g
<054>
Dist. 3.7 miles

Vesselspeed
18 Kts<268>

0.0miles3.0miles1.5miles

0.0milesＨ
CPA 0.1 mile
TCPA 35 min.
Co<088>
Sp'd 19.0 kts
B'g
<267>
Dist. 21.0 miles

1.5miles3.0milesＤ
CPA 1.0 mile
TCPA 22 min.
Co<088>
Sp'd 14.0 kts
B'g
<263>
Dist. 12.0miles

1.5miles

ＧCPA 0.3 mile
TCPA 35 min.
Co
<268>
Sp'd 12.0 kts
B'g
<267>
Dist. 3.5miles

Ｅ

CPA ***TCPA - 30 min.
Co
<268>
Sp'd 14.0 kts
B'g
<133>
Dist 2.8miles

3.0miles4.5miles4.5miles21 miles18 miles15 miles12 miles9 miles

6 miles

3 miles

0 miles-3 miles-6 milesUnderway at night in Bay of Bengal, Indian Ocean (between Pu RONDO and Dondra Head) Co<268> Speed 18kts
TCPA for other vessels noted is less than 25 ‒ 30 minutes, with CPA a maximum of 1 nautical mile (vessels noted above by colors).
Vessel Ａ

A, B, C, D lights

Almost dead ahead (slightly to starboard). CPA at 14.0 nautical miles is 1.0 nautical miles. TCPA in 28 minutes. Displaying green
navigation light.

Vessel Ｂ

Port 2Ũ, CPA at 17.5 nautical miles is 0.2 nautical miles. If following ARPA information, pass on port side in 0.2 nautical miles after 30
minutes. Port and starboard navigation lights can be distinguished, however the red light appears slightly stronger.

Vessel Ｃ

Vessel on same course. Speed 7kts. Gradually opening to starboard. Distance 4.5 nautical miles.

Vessel Ｄ

Vessel on same course. 1 ‒ 2Ũ to port, 12kts. Course parallel to your vessel.

Other vessels involved shown in black.
Vessel ＥVessel on opposing course. Parallel at 5Ũ to port. CPA 1.0 nautical mile. TCPA 22 minutes. Co<088> Speed 14kts.

Vessel Ｇ

Vessel on opposing course. Parallel at 25Ũ to starboard. CPA 4.0 nautical miles. TCPA 15 minutes. Co<088> Speed 18kts.

Mast

Vessel Ｆ

Vessel on same course. 2.8 nautical miles astern. Passed to port 30 minutes ago at 1.7 nautical miles.

Vessel Ｈ

Vessel on same course. Starboard astern <054> Distance 4.0 nautical miles. Passing at Co <267> Speed 22kts. CPA 2.0
nautical miles, TCPA 50minutes.

Appendix ③−７Navigator Education - Navigation Questions and Answers

Radar and ARPA Information (answer)

After 15 minutes

Vector : 12 min.
21 miles18 miles15 miles12 miles9 miles

6 miles

3 miles

0 miles-3 miles-6 miles4.5miles4.5milesＦ
3.0miles3.0milesI
1.5milesＡ

1.5milesAvoid to starboard: <293> Position of vessel after 15 minutes

Ｃ

0.0miles

0.0milesH
1.5milesWhen no avoiding action is takenＤＢ

1.5milesEG
Avoid to port: <243> Position of vessel after 15 minutes
3.0miles3.0miles4.5miles4.5miles21 miles18 miles15 miles12 miles9 miles

6 miles

3 miles

0 miles-3 miles-6 milesUnderway in Bay of Bengal, Indian Ocean (between Pu RONDO and Dondra Head)
AnswerTurn to starboard towards Vessel F. Ensure that course is not ahead of Vessel F. Always ensure that heading does not cross stern of Vessel F.
Diagram above shows relative positions of the vessels after 15 minutes. Changed from original course of <268> to <293>.
4.5 nautical miles travelled in 15 minutes. Vessel is therefore 1.9 nautical miles to starboard from original course, and all vessels except Vessel F arevisible to port.
Sin 24° x 4.5 nautical miles = 1.90 nautical miles
Commencing avoiding action after 15 minutes is too late (cannot pass Vessels I and A) => Only solution is to turn hard to starboard.
A 25˚ turn to port moves vessel 1.90 nautical miles from original course, permitting crossing 4.5 nautical miles ahead of Vessel E, however Vessels E
and Ｄ are in opposing directions,and if an attempt is made to pass Vessel G following astern port-to-port there is a considerable possibility of a turn to starboard.
In this case, unless there is a further turn to port to approximately <190>, Vessel E may not be able to pass safely.
This will also result in dangerous positioning of the two vessels. It is also possible to avoid vessels Ｂ and Ｄ by turning to starboard.

PointsOther vessels to be aware of.
1 Vessel I After crossing at a point 2 nautical miles ahead.
2 Vessel A Possibility of turn to port to avoid Vessel C.
3 Vessel C Possibility of turn to starboard to avoid Vessel A.
4 Vessel D Possibility of turn to starboard to avoid Vessel B.

An example of taking cautios
avoiding action in advance

Predict the relative to positions of the vessels after 15 minutes (use the ARPA simulation function if available).
In this case, Vessels A and C follow the rules for vessels in opposing directions, and Vessel C will therefore possibly turn to starboard. Because of its position relative to Vessels D and B it is apparent that
there is a possibly of turning to starboard.
In this case, one possibility is to follow up on Vessel F, and turn further to starboard.
Crossing will occur 2 nautical miles ahead of Vessel I. Communicate by VHF beforehand the intended avoiding action (turn to starboard), and the intention to cross 2 nautical miles ahead of Vessel I.
Avoid causing any unease on the part of Vessel F. The best option is to cross the course of Vessel I if possible and return to the original course after Vessel I passes on your port side.
Without Vessel E present, an early turn to port is possible, however since Vessel G is crossed in all aspects, a wide turn to port while maintaining a safe distance is desirable (to avoid the possibility of collisioneven in the case of the next vessel in the opposing direction).

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