This document outlines methods and procedures for three situations involving altering course and/or speed of a ship to avoid collision with another ship detected on radar. It provides instructions on how to calculate range to closest point of approach (RCPA), time to closest point of approach (TCPA), target speed (TS), motion (MRM, DRM, SRM) and changing aspects. Examples are given of plotting vectors to determine a new course that maintains a 3 mile CPA when either reducing speed, maintaining course and speed, or altering both course and increasing speed. The document teaches how to analyze radar contacts and calculate new courses and speeds needed to avoid collisions.

1. Enav222 midterm lessons

2. METHOD I (PROCEDURES)ALTER COURSE AND MAINTAIN SPEED

3. SITUATION:Our ship is on Course 0000 T speed 11 knots. Our radar is set on 12 mile scale. A contact is observed as follows:TIME BEARING RANGE0603 0600 11 miles0609 0590 9.5 miles0615 0580 8.0 milesCHANGE OF COURSE

4. Find:RCPA TCTCPA TSMCPA Target AspectMRMDRMSRMPART 1- PLOTTING THE 1ST VECTOR (e-r-m)

5. Oc=0000OS=11knotsXM1/0603M2/0609M3/0615RMLRSpd=11kts.Tdiff.= 12 minDist= 2.2miles

6. 2.2

7. Find:RCPA TCTCPA TSMCPA Target AspectMRMDRMSRMEND of PART 1- PLOTTING THE 1ST VECTOR (e-r-m)

8. PART 2-Plotting the 2nd Vector (e-r1-m)

9. MXBMXTMXRMXNDRMNSRMNTCPANBCPANRCPAFind and Plot the ff:

10. rm6milesNRML3mileseMXNDRM2.2WHAT WILL BE OWN SHIP’S NEW COURSE?

11. rNRM & RLmNRMLr1eMXNDRM2.2

12. NCorNRM & RLmNRMLr1eMXNDRM

13. Nco=054orNRM & RLmNRMLr1eMXNDRMRMLRDRM

14. MXBMXTMXRMXNDRMNSRMNTCPANBCPANRCPAFind and Plot the ff:

15. Of change course problemsEND

16. METHOD II (PROCEDURES)MAINTAIN COURSE AND ALTER SPEED

17. Own ship’s course could be changed to either 054o or 294o . However, there is a reef to starboard and three ships to port that prevent either course changes.Required: What other course of action could be taken?Answer: Reduce speed = 5.2knotsCHANGE SPEED PROBLEMS

18. rNRM & RLmr1NRMLeMXSpd.reduce to 5.2kts.NDRMRMLRDRM

19. METHOD III (PROCEDURES)ALTER COURSE AND ALTER SPEED

20. Instead of continuing own ship at the speed of 11 knots and instead of changing course to either 054o or 294o we decide to increase speed to 15 knots.Required: What course change will have to be made so that at 15 knots, the CPA will continue to be 3 miles?Answer: 065oTCHANGE OF SPEED AND COURSE PROBLEM

21. rMXmeTdiff.= 12 minDist= 3.0milesSpd=15kts.

22. NRM & RLr1e3miles

23. NCO=065OrmNRM & RLMXr1NRMLeNDRM

24. HOW TO PLOT NEW COURSE

25. NCO=065OrmNRM & RLMXr1NRMLeNDRM

26. END