Magnetic compass: The coefficients are the mathematical ... - Rajnav

When the new vessel has just been delivered from the yard
After one voyage of the new vessel where the magnetic characteristics have settled down
When in an old vessel the deviations begin to be large and unsymmetrical etc
At least once every two a year to check the total deviation on all headings
When the vessel has been laid upon one heading for a long time
When considerable alteration has been done to the ships steel work
When the vessel has suffered severe force by way of collision or contact with structures or the vessel was on
fire or struck by lightening
When the ship has loaded magnetic cargo
14.
The Coefficient B has to be adjusted since it has not been split correctly.
15.
Large yaw appearing on North/south course is due to Heeling error. Correct it with the heeling error bucket.
(Latitude correction)
16.
The larger of the two should be corrected first
17.
At the lowest position farthest from the Compass needle
18.
The Flinder bars are offset to eliminate the Ci deviation due to unsymmetrical VSI on one side.
19.
Head the vessel in East or west heading. Check the deviation. Invert the compass and wait for a while. The
deviation should come back to the same value if it does not then the Flinder bars is exhibiting hard iron
properties and needs to be annealed to bring back its soft iron properties.
20.
Head on quadrantal course and check the deviation. Then Slew the spheres through 90 degrees and 180 degrees
and wait for some time after which recheck the deviation if not same then the spheres have lost their soft iron
properties and needs to be annealed.
21.
The process of annealing removes the permanent magnetism and returns them to their original state of soft iron
(ensure to cool them slowly in air)