TB 55-6605-262-24
(5) Index error is to be no more than 1 degree. If more than 1 degree proceed with steps (5) thru
(8) below.
(6) Align vessel to 000-degree heading and record reading of indicator.
(7) Draw a straight line with a ball point pen on side and mounting plate of transmitter case, refer to
figure 1. (This is a reference line only.)
(8) Remove all magnetic material (rings, pens, watches) from person who is to be adjusting the
transmitter case. Loosen the three nuts that secure the transmitter case to the mast support. Rotate
transmitter case so that the new heading on the indicator is equal to heading recorded in step (4) plus or minus
the index error ( number) calculated in step (3).
(9) Secure transmitter case with the three mounting nuts, insuring that the position of transmitter case
does not change.
b. Part B - Single Cycle Compensation.
(1) With the vessel aligned to 000-degree reference heading, compare reading of indicator and adjust
N-S adjustment screw to obtain 000-degree reading indicator.
(2) Align vessel to 090-degree reference heading, compare reading of indicator and adjust screw to
obtain 090-degree reading on indicator.
(3) Align vessel to 180-degree reference heading, compare reading of indicator and adjust N-S
adjustment screw to remove one-half (1/2) of error of indicator reading.
(4) Align vessel to 270-degree reference heading, compare reading of indicator and adjust E-W
adjustment screw to remove one-half (1/2) of error of indicator reading.
c. Part C - Two Cycle Compensation.
(1) With vessel aligned to 000-degree reference heading, compare reading of indicator and adjust 0-
degree adjustment screw to obtain 000-degree reading on indicator.
(2) Align vessel to 180-degree reference heading, compare reading on indicator and adjust O-degree
adjustment screw to remove one-half (1/2) of error of indicator reading.
(3) Align vessel to 045-degree reference heading, compare reading of indicator and adjust 045-degree
adjustment screw to obtain 045-degree reading on indicator.
(4) Align vessel to 225-degree reference heading, compare reading of indicator and adjust 045-degree
adjustment screw to remove one-half (1/2) of error of indicator reading.
d. Part D - Eight (8) Point Heading Swing to Determine Final Error.
(1) Align vessel to 000-degree reference heading. Compare reading of indicator with reference
heading. Record heading of the indicator and its error (1) from the reference heading.
(2) Repeat step (1) for 045-degree, 090-degree, 135-degree, 180-degree, 225-degree, 270-degree
and 315-degree headings.
(3) Final error is to be no more than 3-degrees at any of the 8 headings.
(4) If final error is more than 3-degrees at any of the 8 headings, center the 4 adjustment screws at
rear of indicator by turning each in 25 turns and then back 12 1/2 turns. Repeat entire calibration procedures.
(5) Record errors at 8 headings on compass deviation card and enter into ship's log, in accordance
with AR 56-9.
5. Calibration Instructions for Gyrocompass MK 27, Mod 1, Mod 0.
NAVSEA 0924-LP-038-1010.
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