The Data Link 2000+


Simplified Introduction 

The Data Link is a new ATC tool that aims in replacing much of the controller-to-pilot radio communication by the exchange of electronic messages : say like SMS with mobile phones. There are 2 main reasons that indicated the need for such a Ground-to-Air communication channel : a) frequency congestion and b) safety

a) Frequency congestion is a natural consequence of more and more traffic accepted in the airspace. It is very easy to understand that even a simple 'Good morning' welcoming transmission into a sector becomes an unwanted message if ,say, something like more than 30 aircraft are controlled at this time. Nowadays , capacities of 50 to 60 aircraft per hour become standard practices; there is no time to lose on the radio frequency any more . Additionally , there are a number of non ATC information type messages that could be diverted to an other communication channel type working in parallel and not within the ATC frequency

b) Radio transmissions are always liable to bad reception and human factor errors (perceptions) that distort the information. The route 'mind-to-mouth' and 'radio-to-ears' is delicate and liable to a number of mistakes. 

For the above reasons in the late 60s the SSR link, the only electronic link existing between aircraft-ground on those days was considered as a possible channel for the above purposes. The technology advance , however , allowed near the late 80s to consider the simplest and fastest VHF messages via satellites . Experiments of Eurocontrol under the project PETAL made it possible in the middle 90s.  This link was named : DATA LINK. The next step is to standardise a number of ATC functions that will use specific messages via this channel - this is the aim of another project , the Data Link 2000+ 


Experiences from PETAL were not the end . The Data Link surely holds a prominent place in the future and the Link 2000+ project continues further the tests , to investigate  all aspects of this tool . There is need of course to co-operate with airline partners who provide the 'air part' . AAL was a company keen to co-operate using 4 of its B763s with certified Data Link equipment , with EUROCONTROL , providing the 'ground part' , that is the experimental base ( EEC Bretigny ) and the Control Center (UAC Maastricht) -, data transferred via  ATN ( Aeronautical Telecommunications Network )

The next milestone was a real-time simulation in EEC Bretigny in the airspace of Aix-en-Province and Roma ACCs on February the 8th 2002 . The simulation lasted 3 weeks and the general feeling was that ......IT WORKS !! The important detail to highlight is that both Executive and Planner controllers had an opportunity to access the link thus facilitating the situation in certain cases eventually decreasing the radio occupancy (R/T)

Here we have to stress that it is not only that controllers can uplink data to pilots without using radio but also pilot can 'uplink' data from ground data bases for information of not immediate importance which at present , though , occupy the same ATC radio frequency ( eg : a request for a METAR , a forecast , a SLOT allocation etc.)

Until now some 10.000 air links have taken place after the PETAL-II phase began in May 1998 . It seems that Data Link will be the first equipment to become an 'ATC must' in the very near future

The pictures show a typical human-machine-interface related to Data Link messages. The one above refers to a window indicating the addressed aircraft and instruction passed by a controller to an aircraft (DLH462 , Contact 135.505)


The other ,to the left, is a convenient integration of Data Link smessages into the display system of a Flight Management System. The pilot has entered a request to proceed direct to position RADIS and he is standing-by to receive an answer




ATC 'functions' deemed to be linked via the Data Link


1. Data Link Initiation Capability (DLIC)

 The first ‘contact-and-connect’ from the pilot side to the ATC world . It transmits the following :



2. ATC Communication management (ACM)

 The standard instruction  of “ , next sector on frequency …..” is replaced by the ACM. The interesting part here is that in this signal the sector and aircraft addressed are identified first , so there is no chance to any one else not been the responsible controller to simply intervene in the frequency and instruct any aircraft

 3. Controller Access Parameter (CAP)

 An instruction to Down-Link cockpit data to the controller which then displayed on a specific screen window. It replaces the standard questions to the pilot  like , say : Report heading , speed , crossing an altitude etc. The ground facilities may also be set to ‘monitor’ some of these values, that is trigger and alarm if say the pilot is instructed to start a turn and this is not happening after , say 40 seconds 

 4. ATC Microphone Check (AMC)

 A signal from ATC to all pilots to check for someone blocking a frequency . Marvelous ! Those who remember similar situations would really appreciate this particular Data Link service.

 5. ATC Clearances (ACL)

 Its content is evident. What should be appreciated here is the time spent to deliver ‘long’ clearances with a number of restrictions , a description of a procedure etc. This will no longer occupy the frequency but will be up-linked from the ATC to the cockpit. A ‘roger’ signal triggered from the pilot is expected to be received then , else a warning appears on the controller’s screen

 6. Flight Plan Route Conformance (FLIPCY)

 This is an automatic down-linking of airborne flight plan route data to compare with the ones existing on the ATC Flight Plan Processing System. At times there are differences which may create unexpected hazards. In the past every aircraft had to receive a clearance on first contact. This was later ‘practically’ abandoned as it was becoming very time consuming leading at times to some sad surprises, now it becomes ‘automatic’ !

 7. Departure Clearance

 This is a typical rather ‘long’ type clearance so it is reasonable that it has assigned to the Data Link. It means actually the TWR Delivery information and clearance. It aims at reducing the ‘ground-talk’ , especially on very busy airdromes and/or reduce the workload of the assistant controller charged with this task8.

 8. Digital ATIS (D-ATIS)

 Not a new thing except that is now transmitted via the Data Link. However , you should consider its vast potential as compared to VHF ATIS especially for many compiled data of important volume. It does the present ATIS task with more in less time



For more details please visit the Eurocontrol site :

Return to  the Front (Home)  Page