Starting the Mk 19 Mod 3B Gyrocompass

2. Turn the master switch to the FIL'S position, and

Table 4-1 shows the effect of the four modes of

wait about 30 seconds to allow the tube filaments to

operation on vital compass parameters.

heat.

3. Turn the master switch to the ON position, and

Starting the Mk 19 Mod 3B

wait for the blue ready lamp to light (approximately 11

Gyrocompass

minutes) before proceeding to the next step.

4. When the blue ready lamp comes on, check the

The procedure for starting the compass in the

OWN SHIP COURSE dial to see if the compass is

normal or fast-settle modes of operation is identical to

aligned with the ship's heading. If the dial does not in-

that for the Mk 19 Mod 3A gyrocompass. The procedure

dicate the ship's heading, you need to slew the compass

for starting the compass in the high latitude and DC

until the dial is aligned within 1 or less, if possible.

modes of operation will be discussed in the following

5. Press the RUN button.

paragraphs; refer to figures 4-22 and 4-23 while

performing the steps.

Changes In Operating Modes

HIGH LATITUDE MODE.-- To start the

compass when the ship is between 75 and 86 latitudes,

When the gyrocompass is operating below 75

perform the following steps:

latitude and the ship is planning to navigate above 75

1. Turn the mode selector switch to DC.

latitude, the mode of operation will have to be changed

from the normal mode to the high latitude mode. If the

2. Turn the master switch to the FIL'S position, and

ship plans to continue on and sail above 86, the mode of

wait about 30 seconds to allow the tube filaments to

operation will have to be changed from the high latitude

heat.

mode to the DC mode. The procedure for changing

3. Turn the master switch to the ON position, and

operating modes will be discussed in the following

wait for the blue ready lamp to light (approximately 11

parargraphs.

minutes) before proceeding to the next step.

NORMAL MODE TO HIGH LATITUDE

4. When the blue ready lamp comes on, check the

MODE.-- To change from the normal mode of

OWN SHIP COURSE dial to see if the compass is

operation to the high latitude mode of operation, turn the

aligned with the ship's heading. If the dial does not

mode selector switch to the high latitude mode at about

indicate the ship's heading, you need to slew the

75 latitude.

compass until the dial is aligned within a maximum of

10. The nearer the OWN SHIP COURSE dial is set to

HIGH LATITUDE MODE TO NORMAL

the ship's heading, the quicker the compass will settle

MODE.-- To change from the high latitude mode of

to north when it is switched into the high latitude mode

operation to the normal mode of operation, turn the

in step 7.

mode selector switch to the normal mode at about 75

latitude.

5. Press the RUN button.

HIGH LATITUDE MODE TO DG MODE.-- To

6. Check the LATITUDE COMPUTER dial. If the

latitude setting is more than 1 off the local latitude, you

change from the high latitude mode of operation to the

DC mode of operation, turn the mode selector switch to

must adjust the dial to the correct setting.

the DC mode at about 86 latitude. Record the ship's

7. At the end of 30 minutes, turn the mode selector

longitude at the time the change is made. If the ship has

switch to the HIGH LATITUDE mode. The compass

been maneuvering, you should wait 2 hours after

will now settle to north in 2 hours or less, depending on

completion of the maneuvers before switching to the

how accurately the manual azimuth setting was made in

DC mode. This allows time for the transient error to

step 4.

settle out.

DIRECTIONAL GYRO MODE.-- In the DC

DG MODE TO HIGH LATITUDE MODE.-- To

mode of operation, the compass functions much the same

change from the DC mode of operation to the high

as a simple gyroscope. To start the compass when the

latitude mode of operation, the compass heading must

ship is above 86 latitude, perform the following steps:

be within 10 of true north; otherwise, the compass must

be stopped and restarted.

1. Turn (he mode selector switch to DG.

4-40