Calibration Instructions

TB 55-6605-262-24

(b) Secure all effective magnetic gear in normal sea going position prior to making adjustments.

azimuth by range on each heading before using it as a reference. Be sure gyro is set for the average speed

and latitude of the vessel.

b. Calibration Procedure For Magnetic Compass.

NOTE

These adjustments are made with the vessel underway, on an even keel, and

after steadying on each heading. Refer to Mechanics of Magnetic Compass

Adjustment (Fig. 2).

(1) Adjust the heeling magnet so as to remove oscillations of compass card, with vessel under rolling

conditions on a north and south heading.

(2) Come to a cardinal magnetic heading, e.g. east (090 ). Insert fore-and-aft B magnets, or raise or

lower the existing B magnets, in such a manner as to remove all deviation.

(3) Come to a south (180° magnet heading. Insert athwartship C magnets if required, or raise or

lower the existing C magnets, in such a manner as to remove all deviation.

(4) Come to a west (270° magnetic heading. Correct half of any observed deviation by raising or

)

lowering the B magnets.

(5) Come to a north (000° magnetic heading. Correct half of any observed deviation by raising or

)

lowering the C magnets.

NOTE

The cardinal heading adjustments should now be complete.

(6) Come to any intercardinal magnetic heading, northeast (045 ). Correct any observed deviation by

moving the spheres in or out.

(7) Come to the next intercardinal magnetic heading, e.g. southeast (135). Correct any observed

error by moving the spheres in or out.

NOTE

The intercardinal heading adjustments should now be complete.

(8) Secure all correctors before swinging for

residual deviations.

(9) Swing vessel through the eight cardinal and intercardinal headings. to determine deviations at the

eight headings.

(10) Recalibrate if the final error is more than +5° at any of the eight cardinal and intercardinal

headings.

(11) Record deviations of eight headings and details of corrector positions on compass deviation card

and in the ship's log in accordance with AR 56-9.

NOTE

Frequent, careful observations should be made to determine the constancy of

deviations and results should be recorded in ship's log. Significant changes in

deviation will indicate the need for readjustment.

NOTE

The calibration procedures listed above are extracted from the Hand- book of

Magnetic Compass Adjust-ment Publication No. 226 Defense Mapping Agency

Hydraphia Center.

4. Calibration Instructions for RMHS. Refer to procedures contained in Sperry Publication No. 19-3151-05-

00, June 20, 1975.

NOTE

Readings shown on the RMHS are relative to the magnetic north

pole.

a. Part A - Eight (8) Point Heading Swing of Vessels to Determine Index Error.

(1) Center the two single-cycle correction and the two two-cycle correction adjustment screws at the

rear of the RMHS indicator (refer to fig. 3) by turning each screw 25 turns one way and then turn back 12 1/2

turns.

(2) Align vessel to 000-degree magnetic reference heading, Compare reading of indicator with the

reading of the reference heading. Record reading of the indicator and its error (+) from the reading of the

reference heading.

(3) Repeat step (1) for 045, 090, 135, 180, 225, 270, and 315-degree headings.

(4) Algebraically add sums from the 8 heading readings and divide by 8. Record the quotient

(index error).