NAVIGATION AND
COMMUNICATION
AIRPLANE
OPERATIONS
MANUAL
2-18-30
Page
4
Code
01
DECEMBER 20, 2002
AH-800 AHRS VERSION
Each AH-800 AHRS consists of an Attitude and Heading Computer
(AHC), a Magnetic Flux Detector Unit (MFDU), a Memory Module and
an AHRS Control Panel.
Each AHC uses two 28 VDC power inputs, one for normal power
(primary source) and other for backup power (airplane batteries). The
AHC 1 primary power source is the Essential DC Bus 1 and its backup
power source is the Backup Essential Bus. The AHC 2 primary power
source is the DC Bus 2 and its backup power source is the Backup
Bus 2. If the AHC loses the primary power, it automatically transfers to
backup power.
When the AHC operates solely on backup power, it will operate for 40
minutes.
ATTITUDE AND HEADING COMPUTER (AHC)
The major component of the AHRS is the AHC. The AHC contains
three single axis interferometer fiber optic gyros (IFOG) mounted along
the principal axis of the unit to measure the airplane angular motion.
The signals processed and generated by the IFOGs as well as the
information of attitude, heading and airplane axis accelerations are
transmitted by the AHC in digital format to the airplane systems and
equipment interfaced with the AHRS. In addition, the AHC provides
excitation, current feedback control and signal demodulation interfaces
to the flux detector.
MAGNETIC FLUX DETECTOR UNIT (MFDU)
The AHRS uses the wing tip mounted MFDU as long term magnetic
reference. The flux detector senses the horizontal component of the
earth magnetic field and provides continuous magnetic heading
reference to the AHC. The heading reference is processed by the AHC
to compute an inertial stabilized magnetic heading output.
MEMORY MODULE
The memory module is used to store the AHC mounting tray alignment
coefficients, flux valve compensation coefficients and discrete data
(orientation, source/destination identifier and interface digital buses).
AHRS CONTROL PANEL
The AHRS control panel allows canceling the magnetic field distortion
as well as selecting the Directional Gyro (DG) or Slaved (SLVD)
Modes.
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