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|  MIL-S-85018A(AS)
3.5.4.6 Selector Switch Functions - A Mode Selector switch
shall
be
provided for selecting any of the following modes of operation:
1. SLAVED:
In the SLAVED mode, the system shall operate as a gyro
stabilized magnetic compass system.
2. DG: In the free directional gyro mode the system shall provide
gyro stabilized heading (manually set) and shall be operated independently of
the remote compass transmitter. The directional gyroscope shall be corrected
for earth rate effects as a function of latitude.
3. EMERGENCY:
In the EMERGENCY mode the system shall be operated
only as an undamped magnetic compass slaved to the Compass Transmitter. Use of
this mode shall be limited to flight emergencies only and it shall not be used
to accomplish aircraft mission requirements.
3.5.4.7 Synchronizer and Heading Set - Push-to-sync automatic control shall
be provided to effect the fast synchronization and the heading set. When in the
DG mode, the SET HEADING control markings shall indicate in which direction the
control is to be turned to provide a decreasing or increasing heading. The
mechanism shall, via operator control, provide a continuously variable drive
rate in either direction. The drive rate shall be so damped as to permit
accurate selection of the desired heading in a minimun period of time. The
control shall be of the push-to-turn, spring-to-center type.
3.5.4.7.1 Push-to-Sync - When in the SLAVED mode and when the SET HEADING
control is pushed, the appropriate push-to-sync circuits in the Electronic
Control Amplifier shall be activated.
3.5.4.8 Latitude Correction Control - A manually set control shall be
provided to correct the system for the apparent drift of the gyro due to the
earth's rotation. The latitude selected shall be indicated by a presentation
graduated from O to 90 degrees with a major division for each 10 degrees and a
minor division for each two degrees. The correction shall be applied in both DG
end SLAVED modes of operation, and in First or Second Order operation.
3.5.4.8.1 North and South Hemisphere Selection - The selection of the
Northern or Southern Hemisphere shall be made by a manual selector switch and
the selection shall be indicated by the display of letters N or S on the
Controller panel.
3.5.4.8.2 Latitude Readout - The design shall eliminate a parallax error
when the latitude is read from an angle above or below the readout. The lati-
tude correction shall be applied in both DG and SLAVED modes of operation.
3.5.4.9 Synchronizing Indicator - A synchronizing meter shall be provided
to indicate synchronization to within plus or minus 1/2 degree between compass
system output and the Compass Transmitter, or electrical equivalent, when in the
SLAVED mode of operation. When the system is not synchronized, the synchrorliz-
ing meter shall indicate in which direction the system must be corrected in
order to avoid ambiguity. The synchronizing indicator lighting and markings
shall afford ease of viewing under all operational conditions. the
synchronizing indicator needle shall be capable of setting to a synchronized
null within 3 seconds or less after the SET HEADING button is depressed when the
compass system output and the detector are 180 degrees out of phase. The sync
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