CDM @ Airports - Myths and Truths

For the last ten years, CDM has consolidated itself, as a trend topic in air traffic management and airport operation. And, as with every trend topic, much is said but little is actually understood.

One of the main obstacles to a perfect understanding of what the introduction of Collaborative Decision Making (CDM) concept represents in air the transport, is the result of a historical separation between the aeronautical and airport worlds.

Traditionally, great competences were developed, both in the aeronautical environment (air traffic services) and in the airport world (processes related to the embarkation and disembarkation of passengers and cargo). CDM introduction in air transport, arises precisely from the need to unite these two universes, in order to optimize air transport as a whole, seeking an efficient gate-to-gate operation.

Let's go back a few years in time to the first events of airspace congestion, as the traffic grew. At some point in time - and this moment was not the same in different regions, it became clear that flights were taking off towards airspace congestion - holding patterns, inflight deviations, etc., which made operations longer, more expensive and ecologically damaging (unnecessary fuel consumption and CO2 emissions).

The so-called strategic slots, defined per season, could no longer withstand real operation, where weather events, delays, mechanical failures, etc., led to unavoidable traffic jams. The only possible alternative was to ensure that each flight only started operation, when airspace capacity allowed for uninterrupted gate-to-gate operation. And so was done, with the advent of the Ground Delay Program which, as the name implies, ensured that any delays required for balancing airspace capacity and demand, took place with aircraft on the ground and engines off.

Therein lies the first potential conflict, between past and present paradigms, poorly understood and often ignored in CDM projects. If, on behalf of more efficient and ecologically responsible operation, flights were to be held on the ground, awaiting airspace availability, how could we reasonably continue to measure airlines′ punctuality, via “door closed” times? Should we expect airlines to board passengers and close doors, awaiting airspace availability at the gate? Or would it be reasonable to change the way of measuring punctuality?

This is a complex and controversial subject (historically ignored), which involves passengers' flight experience. After all, which time is actually relevant for passengers, interrupting their activities (business or leisure) at the origin, to further resume them, at the destination?

If we acknowledge the fact that, regardless of flight motivation, a passenger will only be able to resume his activities, when he disembarks at the destination, the flight itself becomes nothing but a hiatus in his availability. The “door closed” time at the origin then becomes irrelevant and the arrival time, at the destination is what really makes a difference in his life.

That is all about the real goal of CDM introduction in air transport – the concept of ensuring uninterrupted operations, whereas inevitable delays be identified in advance, providing two fundamental benefits for passengers:

·????????agile operation, from origin to destination

·????????predictability of their arrival time at destination.

Having understood this first moment of introduction of the CDM concept in air transport, we can now move on to the moment when the aforementioned Ground Delay Program and the restrictions imposed to the take-off times of flights expected to exceed airspace capacity, resulted in a side effect, in airlines′ surface management.

Well, if different restrictions could be imposed to a given flight, on daily basis, then airlines lost the prerogative to start each operation as soon as their processes were concluded - the so-called “first called, first served” concept. It was as if the antibiotic - Ground Delay Program, extremely efficient in combating the original infection - the congestion of the airspace, were now attacking "the liver" - regularity of airlines′ surface operations.

It was in this context that, in regions with greater traffic volume, where the Ground Delay Program drastically affected airlines ground operations, the idea of changing the interaction protocol between Air Traffic Control and Airlines, for the formation of the takeoff sequence, was born.

In summary, the introduction of CDM at airports, corresponded, in fact, to the integration of airport environment to the efforts towards uninterrupted gate-to-gate operations, initiated with the Ground Delay Program. It is important to emphasize that the two entities directly involved in this new paradigm were Air Traffic Control and Airlines. A new interaction protocol between these two entities - the so-called “Best planned, Best served” mode, was based on two intrinsically related assumptions:

·????????Airlines would now estimate, in advance and with maximum accuracy, the time when each flight would be 100% ready to start operation, with all its processes completed. The so-called Target Off-Block Time (TOBT).

·????????The Air Traffic control, considering all variables involved in ensuring uninterrupted gate-to-gate operation, should allocate, for each flight, a 10-minute time window, as close to flight′s TOBT as possible, as the time interval allowed for the pilot to request engine start and taxi. That′s when the concept of TSAT (Target Star-up Approval Time) and its (-5/+ 5 minutes) tolerance window were created.

Perhaps it′s now time to propose an important reflection: if the integration of airport environment into CDM efforts, actually corresponds to a change in the interaction protocol between Air Traffic Control and Airlines, would the Airport Operator really be the natural protagonist of this process? At this point, such assumption sounds questionable, doesn't it?

It is essential to understand that CDM introduction in the air transport, all the way from the Ground Delay Program to its expansion into CDM@Airport (TOBT & TSAT), calls for a reduction in Airlines′ individual flexibility, for requesting start-up and pushback, as a means to promote an improvement in the global availability of airport resources. All for the pursuit of the uninterrupted operations, as recommended by CDM. Therefore, the adoption of CDM@Airport must be the result of a careful study of its operational and economic impact, on airlines′ operation, at the risk of incurring two possible risks:

?????????Taking medication to “the liver” - regularity of surface airline operation, without having taken “the antibiotic” for the original infection - airspace congestion. One can′t fight an infection with medication for the liver! There is a risk of planning a takeoff sequence, not validated by airspace managers - flights will continue to takeoff towards enroute congestions/disruptions.

??????????Taking medication disproportionate to the magnitude of the illness. It should be stressed that traffic congestion in Latin America, corresponds to a fraction of that in regions as United States and Europe. There is the risk of unnecessarily reducing airlines′ individual flexibility, especially outside peak times.

Unfortunately, what we witness in Latin America, is that CDM@Airport is being treated as a panacea, imported from other regions, to cure all the ills of air transport - many of which we do not even suffer. in the region.

What is more serious is that those, who should supposedly be the main beneficiaries of CDM miracle - the Airlines, are precisely the main potential victims of premature imported projects, which have not gone through the necessary gestation period, which characterized its introduction, at busiest airspaces.

The growing resumption of post-Covid air transport activity, offers the ideal opportunity to separate Myths from Truths, in CDM implementation at airport environment. Past offers important lessons, which must be considered, under the light of the operational, economic and cultural environment where early initiatives took place. Future holds challenges, which are to be faced, under the perspective of the regional scenario, in its most varied aspects.?