GPS Receiver

Attitude Heading Reference System (AHRS)

Central Air Data Computer (CADC)

Mission Data Loader (MDL)

Two Additional CDU Systems

4.2.3.1.4  Multiple Multifunction CDU Operation

The CDU MIL STD 1553 bus logic can be designed to support an installation of two or

more CDUs.  In multiple CDU operations, one CDU is the bus controller and the

other(s) are remote terminals and backup bus controllers.  If the active bus controller

fails, then another CDU becomes the bus controller and no degradation in system

performance occurs.  The CDU can be designed such that in multi CDU installations,

any CDU can become the "active" CDU and all can have independent control of data

display.

4.2.3.2  Data Loader System

A GPS receiver (and/or multifunction CDU) may have the capability to load relevant

data over a data link from a Data Loader System (DLS).  The primary func tion of the

interface is to provide the ability to input initialization data from an external nonvolatile

memory device. This is almost essential for GPS avionics systems that must be

compatible with civil aviation and use a large International Civil Aviation Organization

(ICAO) standard waypoint and navaid data base.  A data loader may also be useful for

storing navigation, status, or mission data collected during a mission.  The DLS may be

used to store and load the following:

Waypoints and Flight Plans

GPS Satellite Almanac Data

GPS Satellite Health/Status Data

Antenna Lever Arm Data

Instrumentation Port Parameters

SA/A S Data

Sensor Configuration Data

An example data loader system is shown in Figure 4 3.  The system consists of a

memory device and a read/write/interface unit.  The example memory device is a

plug in cartridge that contains solid state memory, memory addressing circuitry,

serial input/output converters, and an alkaline cell to power the memory for data

retention purposes.  Other memory devices such as magnetic tape cassettes and

computer diskettes are also common.  The read/write/interface unit is installed in

the HV and often resembles a small tape deck in size and appearance.  It contains

the appropriate circuitry to read from and write to the memory device, and contains

interface circuitry to send and receive data from the data link (e.g., MIL STD 1553

or ARINC 429).

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