distribution to the ship's equipment and is sent to the
outputs. Automatic calibration requires 24 hours to
A/D multiplexer for use by the processor.
complete but will continue as long as the mode switch
is in this position.
The digital display indicator provides for local
display of the quantities shown in table 4-3. Data for
Setting the MODE switch to AUTO CAL at anytime
display is selected by the DSPL SEL switch.
after completion of the leveling sequence places the
equipment in the AUTO CAL mode. This mode starts
an automatic recalibration sequence to determine new
The NAV mode, the primary operating mode, is
corrections. These new values are automatically
mechanized the same as the AUTO CAL mode. In the
averaged with old values to accomplish equipment
NAV mode, the heading is not slewed and the alpha
angle is held at zero; thus, the equipment becomes a
All gyro functions and outputs are maintained in the
AUTO CAL mode. The outputs from the IMU resolvers,
The NAV mode is the normal mode of operation and
representing pitch and roll angles, are applied directly
is used between latitudes 85° north or south. If the NAV
to the synchro signal amplifier. The synchro signal
mode is initially selected as the mode of operation, the
amplifier amplifies the resolver input information and
alignment sequence must be completed before the
transmits dual-speed synchro information to the ship's
gyrocompass is capable of providing full accuracy
equipment. Roll and pitch angle information is also sent
outputs. This sequence takes approximately 4 hours.
The alignment sequence is completed when the MODE
to the A/D multiplexer.
ALIGN indicator goes off and the MODE NAV
In the AUTO CAL mode, heading is continuously
indicator comes on.
slewed, completing 360° every 24 hours. The IMU
heading signals are sent to the true heading converters.
Also applied to the true heading converters is the alpha
angle. In AUTO CAL it is set to a value representing 15°
The DG mode is used at latitudes above 85° north
per hour. These two signals are combined in the true
or south. When the gyrocompass is operating in the DG
heading converter to develop true heading information.
mode, the stable element is dampened by velocity
The output of the true heading converter is sent to the
signals and allowed to wander in azimuth. Earth rate
correction is made by torquing the stable element in
synchro signal amplifier for amplification and
Table 4-3.--Data Display Parameters