A-CDM at Brussels Airport: Roadmap to Implementation

  In the previous episode, we made acquaintance with the stakeholders that were involved in successfully deploying Airport Collaborative Decision Making at Brussels Airport. Let's now dive again into the 6 A-CDM concept elements and discover how a successful implementation can be approached. This is part 1 of 2.

First Initiatives

We need to go way back into time...back to 2000, when A-CDM entered the scene here while the whole project was still pretty much in its conceptional phase. Of course, the fact that the airport is only a 10' drive away from the place where Airport Collaborative Decision making was conceived (Eurocontrol, that is), may have facilitated the decision for initial project set-up.

But it were the big network expansion plans of Belgium's national carrier Sabena that formed the trigger to tackle future airport infrastructure capacity restrictions by means of a daring new concept of sharing turn-around progress data among airport stakeholders and the Network Manager.

Back then, I worked in ground handler operations and I  clearly remember a couple of legendary meetings where the target times concept was explained, and how those totally new elements would eventually have to be integrated in long-standing operational procedures. This was pioneering stuff. Never done before at any European airport and we were all excited, but still: the dreaded A-CDM culture change as opposed to the force of habit; even 15 years later still underestimated by many...

Busy afternoon at the B-concourse (source: Brussels Airport Company via Flickr)


In a proof-of-concept phase, target off-blocks times (TOBT) were generated out of commonly known estimated departure times, and shared 'subliminally' with our ANSP Belgocontrol, along with the data set which we had been sharing historically (I explain the data exchange environment later on). Already then, pre-departure sequence build simulations (TSAT) based on those TOBT's made for significant improvements in taxi-out time duration and runway troughput.

But in the aftermath of '9/11', and especially when Sabena went bankrupt and seized operations on November 7th 2001, we found ourselves working at an airport where capacity was all of a sudden no longer an issue. So why still plunging head-first into this wildly concept, of which nobody could prove until then that it actually worked?

Efforts, progress and project communication became ever more 'subliminal', and the lot balanced on the point of going into hibernation. Although airport capacity enhancement is but one of the reasons why you should implement A-CDM, it explains why it was only 7 years later, in may 2008, that the Memorandum of Understanding was signed by the Brussels Airport community. This time, we were back for good.

Share What You Care For


Airport CDM

The last page of the 2008 Brussels Airport MoU (courtesy of the BRU A-CDM team)

Honestly, that's about it when you come out of the boardroom after signing the MoU and you start making plans to cater for A-CDM's baseline: provide the correct data to the right people at the right time, in order for them make the right decisions. Luckily, we could take advantage of the fairly unique set-up of the airport's Central Data Base to host our ACISP (check here for A-CDM's most common abbreviations).

Operational data from the ground handlers, home carriers, the ANSP and the airport slot coordinator is streamed to a central platform, managed by the airport operator, using system-to-system data links. Works both ways, because partners can retrieve each others data via the platform and get a complete view on airport operations in their respective IT systems.

CDB, Our in-house developed airport operational data base (AODB) concept has been around for 25 years -now that's what we call a legacy system!- and is more than ever proving its relevance. While long-standing data exchange set-ups are being upgraded, new links with airport stakeholders have recently been established, and opportunities lie ahead for sharing airport data in airline operator mobile apps. Data with local ATC is exchanged in AIDX format, and has been closely looked at by experts in the field of System Wide Information Management (SWIM).


The Brussels Airport Central Data Base (courtesy of Brussels Airport Company IT Dept.)

This goes to show that we could skip on a tendering procedure to select new software for the data exchange, and  'immediately' start defining the A-CDM information elements to be developed in the existing architecture as per functional requirements, and display them in the up-and-running interfaces.

But even more important than the tech stuff was the fact that there was a data exchange culture, already present among the stakeholders. Of course, budgets needed to be secured to perform the necessary developments, but backed by the commitment to this point stated in the MoU, the 'usual data exchange suspects' quickly found themselves sitting around the table in one of the recurrent program meetings, and concluded on a development trajectory without much fuss.

'A-CDM is not about systems, it's about procedures'. It's a statement you come across on the internet all too often. I agree. So let's focus on project governance in part 2. On how the milestones were plotted in the turn-around process, how they show up in the common situational awareness tools for the airport community, and how the stakeholders eventually integrated them in their day-to-day operations.

Airport Collaborative Decision Making (A-CDM) Concept Elements: Setting Milestones

Airport Collaborative Decision Making

The Concept Elements of European Airport CDM

This is part 2 of a 6-part series on European Airport Collaborative Decision Making, in which we explore the first 4 out of 6 concept elements that constitute the implementation of an A-CDM project. Part 1 provided an introduction to the history and the scope of collaborative decision making initiatives on the Old Continent.

In this episode, we’ll take a closer look at the project implementation steps every European airport that takes itself and Collaborative Decision Making seriously, implements according to the Eurocontrol A-CDM Implementation Manual , before being declared as an A-CDM airport. I’m deliberately using the word ‘declared’ here, as there is no real certification process involved; sharing airport data by means of departure planning information messages suffices for Eurocontrol to have your airport designator code added to the slowly expanding list of A-CDM practitioners.

Walk in the Park?

Now, one may be tempted to believe that this feat is easily achieved within a couple of months. And indeed, technically speaking, setting up the DPI communications link after agreeing on a data exchange protocol may well lie within this range,  but for your data to be of added value for the Network Manager and his Enhanced Tactical Flow Management System , one better comes to terms with the defined 6 concept elements…

Airport CDM

First Things First: MoU

But before getting started, better to have all noses pointing in the same direction: you start off by signing a Memorandum of Understanding in which every contributing stakeholder commits himself to not only talk the talk, but above all to walk the walk with regards to development and training efforts, costs and agreed timelines. Some prefer to sign this document in the close confines of the boardroom, but others, like Stockholm Arlanda airport, where a Brussels Airport delegation was invited for a brief ‘lessons learnt’ showcase, arrange a charming little ceremony for the airport community to spread the word of exciting times ahead.

Information Sharing: ACISP

I’ve done a lot of reading on A-CDM on the internet the past couple of years, and my impression is that many out there believe that the installment of an A-CDM Communication & Information System Platform (ACISP) is the last step on the way to collaborative decision making.  I have to disappoint those who think it’s the last step; it’s the first, rather. Moreover, the investment aspect not taking into consideration, it may have proven to be the easiest hurdle on the way to implementation for many airports when looking back.

Several options for the airport here: you build extra functionality into legacy systems that already managed to exchange operational data, or plug in a tool or protocol to have legacy systems “talk” to each other, or buy one of the solutions offered by the industry. And believe me, there are MANY providers out there eagerly looking out for opportunities to show off impressive software solutions that will cater to your needs.

So, after perhaps a long and tiresome selection round, you, or rather your software provider, will announce to the world that System X or Suite Y has been successfully deployed at your airport. Wonderful. One more detail, though: let’s now put every stakeholder in charge to fill this data base, and let them share their data with the airport community so that it can be duly interpreted for operational purposes at the airport, and beyond.

I hope you forgive my sarcasm here…

The Milestone Approach + VTT = Collaborative Pre-Departure Sequence

The aim of A-CDM: Raise common situational awareness in order to enhance predictability in airport operations. Keeping track of inbound flights and the progress of the turn-around process once docked at the gate. For that purpose, Eurocontrol prescribes the deployment of 16 milestones, covering a substantial part of a flight’s trajectory  (one of aviation’s latest buzz words) into an airport and back out of it. Time stamps are to be made available by the stakeholders who have confirmed to be the respective source of the data reporting over each milestone.


Key milestones are:

  • Target off-blocks time (known to you as TOBT, as from now on), which advises the airport community on the departure readiness of an aircraft. It can originate from various sources, depending on the stage of the turn-around process and can range from a calculated airport operator value based on estimated arrival and minimum turn-around time (MTT), or manually updated by the airline (AO) or the handling agent (GH) to reflect the operational situation.
  • Target start-up approval time (TSAT), ‘in reply’ to TOBT, which of course considers the TOBT, takes Air Traffic Flow & Capacity Management (ATFCM) restrictions into account and establishes the airport’s pre-departure sequence . TSAT management  is mostly an exclusivity of the Air Navigation Service Provider (ANSP).

If not already the case, by the end of this episode you’ve figured out that we Europeans are in love with acronyms…

This is the core of the A-CDM process. Well mastered, played by the book, strictly adhering to procedures, it’s a transparent and waterproof procedure that allows ATFCM to optimize air traffic capacity, by taking ground movements and turn-around constraints into account.

However, pre-departure sequencing requires another data element to be put in place beforehand: the variable taxi time (VTT). This time interval sort of bridges the ‘gap’ between whatever is happening at the aircraft stand and what is bound to happen in the air (and vice versa), and is produced by a tool called the D-MAN, to make sure that the throughput at the runway runs optimal. For that purpose, the D-MAN looks at fleet mix, instrument departure procedures, runway configuration, aircraft taxi patterns… Meaning: reduced taxi times up to and reduced queuing at the runway holding point. Also meaning: trying to keep an aircraft as long as possible at the gate, but I’ll come back later on this issue

VTT’s are also calculated for inbound taxi rolls in pretty much the same way, thus highly ameliorating the quality of the estimated in-blocks time.

Up to the fourth concept element, and in comes the tricky part… but all about this in the next episode. Do you have questions or comments? Leave them below.

This article is part 2 in a series of 6 on European Airport Collaborative Decision Making.

Additional Resources  European Airport CDM  Photo credit: Y. Ferriere