AIRPLANE
OPERATIONS
MANUAL
FLIGHT
INSTRUMENTS
REVISION 37
2-17-25
Page
1
Code
01
AOM-145/1114
RADIO ALTIMETER SYSTEM
The Radio Altimeter system is a high-resolution, short-pulse radio
altitude indicator designed for automatic continuous operation,
providing radio altitude, low altitude awareness, and decision height
information on the PFD.
The system consists of a radio altimeter transceiver and two flush-
mounted antennas (RA 1), and is controlled through the Display
Control Panels. Optionally a second Radio Altimeter Subsystem (RA
2) can be installed.
The decision height setting is provided through the decision height
setting knob on the Displays Control Panel. The decision height and
the associated RA label are displayed adjacent to the lower right side
of the attitude sphere.
The Radio Altimeter interfaces with the Aural Warning Unit to provide
an warning audio signal for autopilot disconnection. For further
information, refer to section 2-18, Autopilot.
RADIO ALTIMETER EICAS MESSAGES
TYPE MESSAGE MEANING
ADVISORY
RAD ALT FAIL Indicates the RA has failed
on airplanes equipped with
a single unit, or both RAs
have failed, on airplanes
equipped with two RAs.
RAD ALT 1 (2) FAIL On airplanes equipped
with two RA, the
associated unit has failed.
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