Magnetic Compass Adjustment
The magnetic compass must be adjusted at least once a year. The process
of adjustment is called "swinging ship." This is required as a safety
precaution; also as the ship steams, its magnetic properties will change.
The process of swinging ship is too detailed and complicated to be
completely taught within this training manual. As the magnetic compass
is considered a piece of equipment, it is covered by the Planned
Maintenance System (PMS). Training on compass adjustment is normally
done by OJT.
The following table lists the basic steps to be followed to adjust a
magnetic compass. It cannot be used solely as a guide for compass
Rule: When performing actual adjustment, you must use the PMS card
and publication 226.
Meet with the navigator to schedule PMS.
Twenty-four hours prior, inform QM gang of intentions.
Four hours prior review MRC; gather all tools.
Four hours prior, calculate the true courses to steer.
Man all stations and begin swinging ship.
Fill out a new magnetic compass deviation table.
Have the new table signed by the commanding officer.
The process of swinging ship is often tedious and very time consuming.
In most cases a minimum of 4 hours should be set aside for this task. It
is not advisable to attempt to adjust a compass in moderate to heavy
weather. Doing so will often render the results inaccurate.
EX 1; 020; 088.5, 091.5; 211.5, 8.5 E; 3.0 W, 7.0 E.
EX 2; 4.0 W, 3.0 E, 2.0 E, 1.5 E.