NAVIGATION AND
COMMUNICATION
AIRPLANE
OPERATIONS
MANUAL
2-18-24
Page
2
Code
02
JANUARY 21, 2002
The CMU functions as a router, with growth capacity as a gateway and
an end system for hosting data link applications. As a gateway, the
CMU can implement future protocols and provide the appropriate
protocol conversions to support airborne systems whose architectures
do not allow updates to future communication protocols but host the
data link applications.
Currently, the CMU is compliant with ARINC 758 level 0, which means
that the CMU is able to perform ACARS functions. The other ARINC
758 levels will be available in the equipment as soon as the software
upgrades are released by the manufacturer.
The CMU is powered by the Avionic Switched DC Bus 1B.
The CMU interfaces with other airplane systems and equipment
through the following equipments:
− FMS The pilot → CMU interface is
accomplished through the Honeywell FMS
(NZ-2000) Control and Display Units
(CDU). It may be utilized with single or
dual FMS installation.
− VHF #3 Transmit and receive data with ground
bases.
− Printer Provides a hard copy data printout.
− Portable Data Loader Used to upload and to download
information, customized configurations
and messages.
− CMC Sends maintenance information to the
ACARS.
− OOOI Used to inform if the airplane is in one of
the following situations: OUT - parking
brake released and doors closed;
OFF - airplane lift-off (Weight Off Wheels);
ON - airplane has landed (Weight On
Wheels); IN - parking brake applied and
doors opened.
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