DLS Newsletter August 2018

Real performance benefits at DFS Deutsche Flugsicherung thanks to Data Link Services

DLS is the basis for future services like 4D-trajectory based operation – as it can hardly to be imagined that a 4D‑route is provided by a controller to a pilot reading a list of geographic coordinates and target-times on a legacy radio-telephony channel.

To pave the way into the more data-driven future, DFS was committed to offer Controller Pilot Data Link (CPDLC) as early as possible. UAC Karlsruhe provides CPDLC in close cooperation with Maastricht as from early 2012 onwards and the German upper airspace became the first in Europe where pilots could use CPDLC from more than a single ACC in daily operation.

Datalink Communication was new to controllers and most of the pilots at that time and expectations ran high. However, the ground infrastructure and avionics in use those days could not cope with expectations, as early users experienced frequent loss of communication. Information and rumours on the issues spread fast in the aviation community and soon many pilots and controllers did no longer supported the new technology, which made it even more difficult to analyse and fix the problems.

Thanks to operators like SAS and easyJet, who continuously encouraged their crews to use CPDLC on their flights through German airspace, it was possible to support the investigations and activities finally resulted in the DLS Recovery plan that SDM lunched in 2016.

One of the main shortcomings identified was that the capacity of the installed VDL Mode 2 communication ground infrastructure could not cope with the demand generated by AOC and ATC services at busy airports in particular.

Following the Recovery plan indications, DFS together with the Communication Service Providers SITA and ARINC invested heavily in improving the capacity of the ground communication infrastructure from the beginning of 2017 by adding more frequencies to move the AOC traffic to dedicated Airport frequencies as much as possible, i.e. leaving more headroom for ATC at the frequencies dedicated to en-route data communication. As a result, datalink capacity is expanded three to five times now when compared to the capacity available at the beginning in busy airports.

Was the result of the DLS SDM coordinated Recovery plan activity worth the effort and money spent?


Let’s check the figures first:

Compared to early 2017 where approx. 5% of the flights crossing Karlsruhe airspace used CPDLC, the usage rate is now at a stable 13 % now,


“Provider Aborts” (loss of Communication) dropped from an average of 4.5% in mid-2017 to an average of 2% in the first half of 2018.



The “Turn Around Time” – i.e. the technical delay until the aircraft system acknowledges a datalink message – does improve from approx. 30 seconds in 2017 to an average of 22 seconds in 2018



The direction of these figures is promising, but the CPDLC usage rate is still not at  the 75% goal required by the EC Regulation n° 29/2009 in terms of flights equipped in 2020 . “Provider Abort” also need further improvements to reach the target value of less than one communication loss per 100 flight hours.

How is CPDLC perceived by the controllers?

ATCO-1:       “We do recognise that CPDLC performance improves in particular when there are high traffic situations. However, data communication with pilots is still not as reliable as we would like it for our busy airspace. It is good to see, that there is more aircraft using the system now and the pilots respond quicker to CPDLC messages than in the past.
CPDLC is an asset in our routine operation that we appreciate and it is worth to improve further.”


ATCO-2:       “Judging the relevance and how helpful datalink communications are is not so easy since users are accepting beneficial tools quickly and forget at the same time about the situation we were faced with before.
Beside all the statistics that show the quick and huge development of datalink, I remember one day in Europe that showed the advantage of CPDLC-operations: it was the ETFMS-failure at the Network Function (remark:
3. April 2018), which was sad for the incident itself and all users, but for a straight comparison it proved useful and showed the added value of datalink. Even as a daily and satisfied user of CPDLC, I was astonished at how often we use it, and meanwhile, how high the automatic logons are and how quick communication can be. Since all flight plans and their corresponding codes were missing during the ETFMS-failure at the Network Function, we were not able to establish any datalink communications at all and step back to basic radio-telephony communication (remark: aircraft 24bit address required to accept a flight at CPDLC was not known due to the ETFMS breakdown).
Not only because of that incident but also through communication of the respective persons and most importantly through the stability and reliability of the network, datalink is applied daily and successfully these days and I would not like to miss it. There are still some things left to do with regard to system evolution, but the focus for me is now to further train the users (esp. pilots) in applying it correctly and to make the most benefit out of the functionality.
After spending so much effort and money, datalink is a story of success that has not yet ended, but which has definitely overcome the problems of our implementation phase. Nowadays for sure it can be said, that datalink has become one of the basic tools for aviation staff, assisting users well and reducing workload significantly. Datalink is one of the key contributing factors to further increasing working efficiency and balancing workload.”


ATCO-3:       “I wonder if a CPDLC awareness campaign will encourage more pilots to use CPDLC in the future. The Datalink Communication system has improved in recent months notably but we still have some shortcomings to be continued to be worked on. In addition, I see possible improvements in the ATS-Systems that can ease the use of CPDLC for an air traffic controller and increase the number of scenarios wherein CPDLC can replace radiotelephony for ground to aircraft communication.”  


Finally, Datalink is on the right track. Karlsruhe Controllers appreciate to use it in their daily routine and would like to see more pilots connecting to the system. Nevertheless, it is also recognised that the system performance is not yet where it should ultimately be, i.e. there is still some way to go to bring the datalink infrastructure to a level where the performance is as required for an unlimited ATC usage. It will then become a challenge to maintain the system at that level, as the continuous growth in demand for datalink bandwidth from both the ground (ATC and AOC) as well as the aircraft (avionic) may erode the achieved improvements again in the future. SESAR Deployment Manager is working with all involved stakeholders on a new architecture to avoid this from happening.


Next steps towards end solution

IP1 & DLS Capacity assessment

On April 5th2018, a multi-stakeholder IP, the so-called IP1 (2017_089_AF6), has been submitted for the 2017 CEF Transport Calls with the aim of solving the open points arisen during the execution of the Path II Project[1]and designing the Common European ATN Ground Network. The IP1 was launched officially on 12thApril 2018 in Madrid and it is divided into three Work Packages:

  • WP1 – Design for a Common European ATN Ground Network: consisting in the design of the ATN Backbone which is the technical Ground ATN infrastructure for the provision of the European DL Services;
  • WP 2 – Further analysis and solving of the technical open points identified in Path II project, regarding the overall target architecture definition and finalisation;
  • WP 3 – Further analysis and solving of the non-technical open points identified in Path II project, regarding the identification of all the needed elements to finalise the Business Case.

Following the KOM held in Madrid, the first plenary meeting of the IP1 was held in Brussels at SDM premises (19th–21st June 2018), aiming at providing an overview of progresses concerning each WP.

In parallel to IP1, a call for Tenders for the VDL Mode 2 Capacity Assessment has been launched on the 4th of May 2018, aimed at supporting the resolution of the open points identified within Path II Project, enabling the completion of the architecture and business case, as well as at assessing the lifespan and performance of VDL Mode 2. Several proposals have been received by 1stJune 2018 and are currently under formal evaluation.



Lufthansa confirms the achievement of performance benefits

Significant performance results have already been achieved through the Path I transitional solution implementation (Multifrequency deployment), notwithstanding the increase of aircraft using Datalink services.

Lufthansa, among other Airspace Users stakeholders, confirmed the achievement of performance benefits, expressing positiveness towards DLS, declaring:

  • “Controller–Pilot Data Link Communications (CPDLC) Provider Abort rate and AOC reject rate was significantly reduced in the 2ndhalf of 2017 which was used to encourage pilots in using CPDLC.”
  • “Datalink performance has been increased over the past years by both major Communication Service Providers (CSPs) with the introduction of multi-frequency VDL.”