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Page Title: Operating the Mk 19 Mod 3A Gyrocompass
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which is identified as the normal mode while the ship
a true level position and the meridian gyro to settle on
sails in latitudes (north or south) between the equator
the true meridian.
and 75.
This system is actuated by placing the mode selector
switch, located on the front of the compass control panel
Auxiliary operating modes are described later for
(fig. 4-22) to the FAST-SETTLE position. This switch
compass (chiefly submarine) uses between latitudes 75
completes the energizing circuit to the fast-settle relay,
and 90 near the poles. Operation in the normal mode is
located in the computer control assembly.
generally undesirable in these latitudes because
horizontal earth rate (proportional to the cosine of the
When the fast-settle switch is closed, it energizes
the 4-pole, double-throw, fast-settle relay. The
latitudes) results in the compass period becoming very
operated fast-settle relay alters the resistance
high, causing slow settling and consequent poor azimuth
connections in the meridian gyro gravity reference
system, which increases the damping signal output. It
EMERGENCY OPERATION.-- If the ship's ac
also allows the primary voltage of the meridian
control step-up transformer to be taken directly
power line fails or drops below 105 volts, undervoltage
from the cathode follower instead of from a
relays open their normal contacts and switch to
potentiometer, thereby increasing the meridian
battery power that is applied to the dc generator so it
control output signal. When operated, the relay's
serves as a motor. Speed of this dc temporary motor is
contacts short a potentiometer in the slave gyro gravity
controlled by a centrifugally operated speed regulating
reference system, increasing the slave gyro leveling
device. The ac section then operates as a synchronous
generator (driven by the dc section) and, for a period of
The fast-settle switch also disconnects the alarm
15 minutes produces 0.75 kW, without excessive
circuit from the delay relay, rendering the compass
temperature rise.
failure alarms inoperative when the fast-settling system
is in operation. A fast-settle lamp is lighted when the
When the ship's power line is restored above 112
switch is closed, giving visual indication of fast-settle
volts ac, the relay automatically returns both units
(motor and generator) to their normal functions. The dc
section is then generating current and charging the
Operating the Mk 19 Mod 3A
storage batteries.
The Mk 19 Mod 3A gyro system maybe started by
settle mode is auxiliary to the normal mode. It is used
setting the fast-settle switch to either the OFF or the ON
on all Mk 19 compass models for starting.
position. The settling time is much longer when the
Two additional auxiliary modes are available on the
system is started in the OFF position. Therefore, it is
recommended to always start it in the FAST-SETTLE
Mod 3B, identified as high latitude mode and directional
mode. Some converted Mod 3A gyros also have them.
These two modes of operation will be explained later in
Because the alarm system is NOT in operation while
this chapter when we discuss the starting procedures for
it is in the FAST-SETTLE position, the switch should
the Mod 3B compass.
be reset to ON as soon as practical. The amount of time
to settle is least when a ship is sailing at the equator and
is greatest at the poles (90 latitude).
Securing the Gyrocompass
Two hours (120 minutes) is the normal period
of oscillation at 40 latitude. With the fast-settle
When your ship returns to port after an underway
switch in the ON position, the period of oscillation
period, you must obtain permission before securing the
is reduced to 50 minutes. These approximate periods
compass. Permission to secure the compass is normally
are characteristic of all mods of the Mk 19 com-
granted by the engineer officer.
To secure the gyrocompass, turn the master switch
NORMAL OPERATION.-- Normal operation of
(fig. 4-22) to the OFF position. After the compass is
the Mk 19 Mod 3A compass is obtained after the
secured, notify the engineer officer.
fast-settle switch is moved to the OFF position,

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