continuous roll, pitch, and heading signals. These
signals go to the aircraft attitude indicator and
other avionics equipment. Error signals develop
in the displacement gyroscope as a result of
displacement of synchro sensing devices from their
null position. A remote compass transmitter
supplies additional heading information to the
s y s t e m . For detailed information on the
A N / A S N - 5 0 system, you should refer to
Reference Altitude Heading, N A V A I R
05-35LAA-1.
In the attitude heading reference system, roll
and pitch information goes directly from the
vertical gyroscope to the attitude indicator. The
system supplies azimuth information in one of
three modes selected on the compass controller--
COMP (compass), SLAVE (slaved), or FREE
Figure 7-21.-Displacement gyroscope.
(free).
The compass mode is an emergency mode
used when the displacement gyroscope is mal-
erection voltages during turns of 15 degrees per
functioning. When operating in the compass
minute or greater.
mode, the magnetic heading signal from the flux
valve integrates with a compensating signal. This
Displacement Gyroscope
integration corrects for magnetic field distortion
around the aircraft.
The displacement gyroscope (fig. 7-21) is a
The free mode is used at latitudes greater than
hermetically sealed, two-gyroscope platform
700. You can also use it in areas where the earth's
providing pitch, roll, and azimuth signals to the
magnetic field has appreciable distortion, and
system indicating instruments. The vertical
when the flux valve fails. When operating in the
gyroscope provides a source of pitch and roll
free mode, you manually set the initial heading
information, while the directional gyroscope
reference, using the compass controller PUSH TO
provides azimuth (yaw, heading) information.
TURN control. After establishing the initial
Control transmitters (synchros) convert attitude
reference, heading information accuracy depends
changes into electrical signals that represent pitch,
on the directional gyroscope's ability to maintain
roll, and yaw. (The AN/ASN-50 displacement
its position relative to earth.
gyro is similar to the one discussed earlier in this
The slaved mode is the normal operating
chapter.)
mode. This mode uses both the flux valve and
Erection circuits maintain the spin axis of the
directional gyroscope signals. The directional
vertical gyroscope in a gravity vertical position.
gyroscope signal acts as a stabilizer for the flux
These circuits consist of a roll electrolytic switch,
valve data. Automatic fast synchronization to the
with associated roll torquer, and a pitch
magnetic heading occurs during the start cycle and
electrolytic switch, with associated pitch torquer.
upon switching to the slaved mode. A SYNC IND
A servo loop maintains the spin axis of the
meter on the compass controller shows when a
directional gyroscope level. The loop consists of
loss of synchronization occurs. The loss of
a leveling pickoff, an external leveling amplifier,
synchronization occurs between the azimuth
and a leveling torquer.
heading output and the flux valve. When such a
The vertical gyroscope spin motor mounts in
condition exists, you may accomplish fast
the inner roll gimbal, which is free to move in a
synchronization by momentarily pressing the
roll direction. The freedom of movement in the
compass controller PUSH TO SYNC switch.
roll direction is limited to 82 by mechanical
stops to prevent gyroscope gimbal lock. Gimbal
Autopilot decoupling occurs whenever manual
lock would occur if the vertical gyroscope spin
or automatic synchronization occurs. Circuitry
axis were to become aligned with the vertical
compensates for apparent drift of the gyroscope
gyroscope pitch gimbal. The directional spin
resulting from rotation of the earth. Other
motor mounts in the directional gyroscope
circuitry provides means to interrupt slaving and
