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1 GENERAL DESCRIPTION
1.1 Introduction
This manual presents mechanical and electrical installation requirements for installing the GRA 5500
Radar Altimeter as part of a Garmin Integrated Flight Deck and in retrofit/stand-alone applications. The
GRA 5500 can be integrated into a variety of airframes under an appropriate TC or STC. Each airframe
installation may vary. Use only approved (type or supplemental type) data for specific installation
instructions in a particular aircraft.
1.2
Equipment Description
The GRA 5500 is a digitally-based airborne low-range radar altimeter designed to calculate and provide
precise Above Ground Level (AGL) altitude information for both Garmin Integrated Flight Deck and
retrofit/stand-alone radar altimeter applications. The GRA 5500 features a standard two-antenna
architecture utilizing low-power "gated" FMCW operation, digitally-based transmitter operation,
advanced digital signal processing (DSP) based receiver altitude detection algorithms, operation from
ground to 2500 ft AGL, accuracy of +/- 1.5 ft (0 – 100 ft AGL), +/- 2 % (>100 – 2500 ft AGL), full-
featured self-test operation (BITE) and fault logging functionality (including patent-pending automated
self-testing and fault detection of the entire internal TX, RX, and processing circuitry), a patent-pending
on-ground automated installation calibration procedure to essentially eliminate the traditional requirement
for a minimum RF antenna cable length, 14 Volt and 28 Volt operation, two configurable ARINC 429 data
outputs, two proprietary Garmin HSDB over RS-422 data interfaces, and a standard USB full-speed
interface for convenient unit configuration, calibration, diagnostics, and software updates in retrofit/stand-
alone applications.
1.3
Interface Summary
The GRA 5500 provides the following interfaces via circular connector:
•
Two "diode ORed" aircraft power inputs (for redundant power systems)
•
Two ARINC 429 data outputs (configurable for output data formats and data rates)
•
Two Garmin High-Speed Data Bus (HSDB) over RS-422 data interfaces (used in lieu of ARINC
429 data outputs in Garmin Integrated Flight Deck installations)
•
Two active-low annunciator outputs used for optional "altitude alert" indications (altitudes are
installation configurable)
•
Four active-low discrete inputs used as configuration straps in dual and triple installations and for
optional manually-initiated self-test and self-test inhibit operation in retrofit/stand-alone
applications.
•
One standard Universal Serial Bus (USB) full-speed interface for unit configuration, calibration,
diagnostics, and software updates in retrofit/stand-alone applications.
•
One Garmin configuration module interface (configuration module usage is not required in
Garmin Integrated Flight Deck installations and is optional in retrofit/stand-alone applications in
order to retain unit configuration parameters external of the installed LRU)
The GRA 5500 also provides RF connections from the transmitter and receiver to the respective radar
altimeter antennas via standard TNC (threaded Neill-Concelman) connectors.
See
Section 4
for connection details.
190-01277-00
Rev. A
GRA 5500 Installation Manual
Page 1-1
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