TB 55-6605-262-24
(b) Secure all effective magnetic gear in normal sea going position prior to making adjustments.
(c) When using a gyro compass, swing from heading to heading slowly and check gyro error by sun's
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).
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