3-17. ATTITUDE AND HEADING REFERENCE SYSTEM (AHS-3000).
The dual Attitude and Heading Reference System (AHRS) consists of the following Line Replacement Units (LRUs),
2 each: AHC-3000, FDU-3000, ECU-3000, and MMT-3010.
a. The AHC-3000 measures angular rates and linear accelerations about the body axes of the aircraft and
digitally processes this data to obtain 3-axis angle, rate and acceleration information.
b. The Flux Detector Unit (FDU-3000) is a gimbaled 2-axis magnetic sensor that detects the horizontal compo-
nent of the earth s magnetic ield. Magnetic heading is derived and used to slave the computed heading angle in the
AHC-3000. The FDU-3000, along with its compensation data, provides an accurate long-term heading reference.
The FDU compensation data is used to reduce the effect of hard iron errors and lux detector misalignment.
c. The compensation data is aircraft speciic and stored in the External Compensation Unit (ECU-3000). When
operated in the FDU compensation mode, the AHC-3000 determines and stores the hard iron compensation data
as the aircraft is positioned at eight heading steps. If an index correction is required, the AHC-3000 determines
and stores the correction during the last step of the compensation procedure while the aircraft is aligned to a known
d. The AHC-3000 is designed to be rack mounted in an MMT-3010 mounting tray. The mounting tray is de-
signed to allow repeatable high accuracy installations. A precise alignment of the mount surface is required for the
AHC-3000 to provide accurate attitude information. The ECU-3000 contains two EEPROM chips that are designed
to stay with the MMT-3010 during replacement of the AHC-3000.
3-18. AIR DATA SYSTEM (ADZ-800).
The air data system consists of two digital air data computers (AZ-800) and the altitude preselector (AL-801). The
digital air data computer is a microprocessor-based digital computer which accepts both analog and digital inputs,
performs digital computations, and supplies both digital and analog outputs. It receives both pitot and static pressure
for computing standard air data functions. Altitude preselect data is input from the altitude preselector. Information
from the digital air data computer is sent to the FMS Data Concentrator Unit (DCU), transponder, light director/au-
topilot computer, INS, and GPS.
3-19. ELECTRONIC STANDBY INSTRUMENT SYSTEM (GH-3100).
The Model GH-3100 Electronic Standby Instrument System (ESIS) provides backup pitch, roll, slip/skid information,
and backup Air Data information (airspeed, altitude, and vertical speed) using internal sensor systems. The system
also contains interface capabilities to display Heading and Navigation information. See the vendor s operator manual
for detailed description and operation.