COMMUNICATIONS, ACARS
Description
Aircraft Operations Manual
4/5.1
PAGE
1
Apr 01/15
1.
GENERAL
ACARS is an abbreviation for ARINC communica-
tion and reporting system. The system is designed
to reduce the requirement of voice communications
by reporting automatically the arrival and departure
times of the aircraft and other operational flight
data. The system uses an assigned VHF airborne
frequency to transmit and receive data from a
ground station that is similarly equipped.
The system provides current up
−
to
−
date informa-
tion to the aircrew without increasing the workload
of voice communication systems. The ACARS al-
lows the aircrew to send information such as depar-
ture time, arrival time, fuel status, and flight delay
information to the airline command center. In es-
sence, the ACARS system provides an information
service to the aircrew and the airline command
while still maintaining a manageable workload for
the aircrew. Other benefits of ACARS include
ground monitoring of aircraft engines and other pa-
rameters, more efficient exchange of information
concerning arrival and connecting flights, reduction
of multiple frequency changes in the aircraft, and a
more reliable aircraft selective calling system.
2.
MAIN COMPONENTS AND SUBSYSTEMS
2.1
ACARS system
The ACARS system consists of an airborne subsys-
tem and a ground station network. The airborne
ACARS consists of a Management unit, Control
display panel, VHF com transceiver and a VHF an-
tenna. The ground station network consists of a
VHF com ground station controlled by a central pro-
cessing computer, and a switching network con-
nected to individual airline computer systems, see
Fig. 2.
2.2
Management unit
The Management unit contains the circuits required
to control sampling of data from aircraft systems
and sensors through the FDAU. The Management
unit receives the ground
−
to
−
air digital messages
from the VHF com transceiver and controls the
transmission of air
−
to
−
ground messages through
the VHF com transceiver, see Fig. 1.
2.3
Control display panel
The Control display panel provides the aircrew in-
terface with ACARS. The touch sensitive display
screen provides Keypads, Alphabetic and Numeric
Keyboards to allow entering of the text portions of
the departure/arrival reports, ETA reports, company
messages etc. The display screen is covered with
an infrared touch
−
matrix for data input. The touch is
detected as a breach in the infrared matrix and is
activated until the breach (finger, pen etc.) is no
longer present.
The infrared touch technology always permits op-
eration even in direct sunlight and at all touch
angles.
The display supplies both bit mapped graphics and
text with a text range from 14 lines with 24 columns,
to 24 lines with 40 columns.
2.4
Printer
The printer provides a hard copy printout of data,
collected by the Management unit. Data that will be
printed includes upbrushed printer messages and
data entered into the Control display panel not
queued for transmission. Upbrushed messages
could include weather reports, dispatch information
etc.