Last update Martes, Febrero 03, 2004 06:10:51 p.m.

ACARS (Aircraft Addressing and Reporting System) is a digital data network using aircraft VHF and/or HF radio to
transmit/receive data from/to airline operations. The usage of that system for the airlines is to have contact
with their aircraft around the world and for the pilots to have weather data etc.

Basically ACARS is a replace of HF (for long distance) and VHF operational-company frequencies.
For example here in Athens the LDSs passed to the pilot/aircraft through ACARS. Even a catering request is
given on ACARS and not by voice. The airlines is possible to "track" their aircraft around the world
(with the Q0 messages, see below)

Other capabilities of the system are: logging pilots flights time, maintenance departments observe aircraft status,
movement actual times and more...

All these are the first step of ACARS usage and you can say that it's a test phase of the Future Air Navigation Systems
(FANS). After many years of tests with company messages ACARS are used by ATC in many places around the world.
In many US busy airports clearances for take-off/land passed to the aircraft through ACARS.
Over North Atlantic Ocean every day positions reports (auto) given from aircraft to Shanwick.
Also OCEANIC clearances passed to the aircraft from the ACCs by ACARS.
At North Pacific flights such UA896 Chicago-Hong Kong navigated through FANS from the ground.
Magadan Control is able through FANS to change from the ground the flight level of the UA 744 directly to the FMS...

Spotters @f Greece ACARS equipment

CURRENT : There are two ACARS "monitoring stations" at Greece. The first one (main) is located at Athens and running since 15 October 1994 24H a day. Using a PC 486DX100 with LOWE Air Master 2000 decoder and a SPORTYS-A300 VHF airband conected with an LAB 100-500Mhz antena logging 24H a day the frequency 131.725, covering the area with the red line on the coverage map.

The second ACARS "monitoring station" is located at the Norteast country and the purpose of that station is to monitoring long haul flights between Europe, Middle East and Far East using Turkey/Bulgarian airspace. The coverage of that station can be seen on the coverage map marked with yellow line. 2rd ACARS "monitoring station" is located at Northeast Aegean Sea in Mytilene(LESVOS Island). Using a PC Pentium 4 2.66Mhz with AIRNAV DECODER 1.1 and a KENWOOD TH-F7E handheld VHF connected with an DISCONE SCANMASTER D1300 antenna logging the frequency 131.725Mhz.

When the two additional ACARS links will run we are holping to expand our web site into a movement site covering a lot of airports in Europe and Middle East. Greek Aviation Enthusiasts holping to add Malta and Cyprus to the ACARS coverage map some day.

ACARS Monthly LOG : DECEMBER 2003 (click here to download ZIP XL file 200kb)

****Check out also Greek FIR live ACARS Tracking. Schedule of operating hours can be found on Calendar section of Aviation-Enthusiasts mailing list.****

ACARS components are installed on the aircraft but also on the ground.

1. THE AIRBORN SUBSYSTEM
Onboard the aircraft separated in two categories
a.) Management Unit Receives ground-to-air messages via the VHF radio transceiver, and also controls the replies.
The MU is the controller of the data replied or transmitted from/to network. There are for example installed sensors
in the gear system and when the pilot re-track the gears automatically the MU transmits an airborn report.
Other example is the ON/OFF blocks reports using parking brake status as source.

b.) Control Unit is the air crew interface with the ACARS system (main cockpit console), consisting of a
display screen and printer. The messages are written using the FMS keyboard.

2. THE ARINC GROUND SYSTEM
A network of Ground Links (GL) and SAT links connects the airlines departments with the aircraft.

3. THE AIR CARRIER C2 (Command and Control) & MANAGEMENT SUBSYSTEM
Which is basically all the ground based airline operations such as operations control, maintenance, crew scheduling
and the like, linked up with the ACARS system.


MESSAGE STRACTURE/FORMAT
That is a Q0 message generated by an ACARS software
ACARS mode: C Aircraft reg: .G-BNWC
Message label: Q0 Block id: 9 Msg. no: S68A
Flight id: BA0631
----------------------------------------------------------[03 Dec 2000 01:35]
That is the same Q0 message from aircraft in original format
.G-BNWCQ09
S68ABA0631
DECODE
* .G-BNWC = REGISTRATION
* Q0 = MESSAGE LABEL (varies regarding the subject of message)
* 9 = DOWNLINK BLICK ID
* S68A = MESSAGE SEQUENCE NUMBER (often is 4 digit number,5400, means time 5400=54 minutes 00 seconds
* BA0631 = CARRIER & FLIGHT NUMBER

HOW ALL THAT SYSTEM WORKS
Each Ground Link transmits its ID every 2 minutes (UPLINK).

ACARS mode: a Aircraft reg:
Message label: SQ Block id: [Uplink]
Message content:-
ATH100XS
----------------------------------------------------------[03 Dec 2000 01:47]


Also every aircraft transmits a signal with its ID every 10 minutes (DOWNLINK). That message has label Q0.
ACARS mode: C Aircraft reg: .G-BNWC
Message label: Q0 Block id: 9 Msg. no: S68A
Flight id: BA0631
----------------------------------------------------------[03 Dec 2000 01:35]


Q0 messages "reports" to the server under witch specific Ground Link coverage the aircraft located.
Highlight here that each aircraft has its unique address. That is the registration mark.
That works with a calculation of Ground Link station signal strength h from the aircraft.
That is happens because an aircraft flying at FL390 maybe receiving more than 1 GL.

I.e. when BA633 flying North of Athens when passing SKP at FL280 he is also under cover of THESSALONIKI GL.

ACARS mode: a Aircraft reg:
Message label: SQ Block id: [Uplink]
Message content:-
ATH100XS
----------------------------------------------------------[03 Dec 2000 01:47]
ACARS mode: a Aircraft reg:
Message label: SQ Block id: [Uplink]
Message content:-
SKG100XS
----------------------------------------------------------[03 Dec 2000 01:47]

Here is a list of all messages exchanged between GL and a BA 767 in Athens

Weather request for LIRF & LSZH (the pilot insert through a standard weather request form the id of the required
airport and the system is transmitting the request to a pre-define address. The answer also is automatically send
from a computer through SITA with origin address (.SINGMXS)

ACARS mode: 2 Aircraft reg: .G-BNWC
Message label: C1 Block id: N Msg. no: .SIN
Flight id: GMXS 0
Message content:-
30137
AGM
AN G-BNWC/GL ATH1
- /
FT 19/22:00
LIRF 200624 VRB06KT 5000 BR FEW025 SCT080 FM0900 27014KT 9999 SCT025
SCT090 BECMG 2022 VRB05KT=
FT 19/22:00
LSZH 192200Z 200624 26007KT 9999 SCT040 BKN
----------------------------------------------------------[03 Dec 2000 01:37]


Server is able to remote the aircraft box switch it to other ACARS frequency. FUC letters means "function"
ACARS mode: C Aircraft reg: .G-BNWC
Message label: 10 Block id: 4 Msg. no: M17A
Flight id: BA0631
Message content:-
FUC01
131.725
136.925
131.725
000.000
000.000
000.000
000.000
000.000
----------------------------------------------------------[03 Dec 2000 01:36]


That message is the "electronic" LOGBOOK of BA for pilots. The name of each pilot is a 5 letters length word
(shortcut of the normal name)
ACARS mode: C Aircraft reg: .G-BNWC
Message label: 10 Block id: 5 Msg. no: M10A
Flight id: BA0631
Message content:-
PRE0102300305 ROSNM TROTS
TROTS 2143215500570105032203020081N
----------------------------------------------------------[03 Dec 2000 04:53]


That message generated by MU when the parking brakes sets to OFF position.
ACARS mode: C Aircraft reg: .G-BNWC
Message label: 11 Block id: 6 Msg. no: M12A
Flight id: BA0631
Message content:-
OUT0105050451
----------------------------------------------------------[03 Dec 2000 04:55]

That message generated by MU when the gears were retracted. You can see below that every information of FMS
is possible to transmit via MU to the network. CLOSEDR is doors close message and the source is the doors status
displayed on FMS.
ACARS mode: C Aircraft reg: .G-BNWC
Message label: 12 Block id: 7 Msg. no: M13A
Flight id: BA0631
Message content:-
OFF010521DIA01LGATLHR BA7V042898OFF CLOSEDRLS131725OK N/A NCOMNVD
NVD NVD NVD OK READY
----------------------------------------------------------[03 Dec 2000 04:58]

Another usage of ACARS is weather data collection from several weather ground stations.
The known AMDAR are automatically send messages with weather data from every position around the world.
That function needs except ACARS capability some more sensors installed on the aircraft.
ACARS mode: C Aircraft reg: .G-BNWC
Message label: H1 Block id: 8 Msg. no: D07A
Flight id: BA0000
Message content:-
#DFBAMDAR 2000
LVR BA195 3911N 01951E 0022 F370 MS567 313/029 TB0 S011
/// BA195 3834N 02045E 0029 F370 MS565 326/027 TB/ S111
LVR BA195 3806N 02145E 0036 F330 MS495 341/029 TB0 S011
/// BA195 3
----------------------------------------------------------[20 May 2000 05:35]

That message is an automatic position report over THESSALONIKI.
ACARS mode: A Aircraft reg: .G-BNWC
Message label: 15 Block id: 6 Msg. no: M40A
Flight id: BA0631
Message content:-
FST01LGATEGLLN40274E0225904350 164 214 M56C 15345137140496XS02200530
----------------------------------------------------------[03 Dec 2000 05:32]
Explanation :
FST01 = FLIGHT STATUS
LGATEGLL = Athens-London Heathrow
N40274E0225904 = cordinates of current position
350 = flight level
164 214
M56C = temperature
15345137140496XS0220
0530 = time

Here is a list with aircaft using ACARS and flew over Greece