About A-CDM Round the Coffee Table – Trajectory, Processes, Services and other Bits and Pieces for the Stout-hearted Only

On 16-08-2016, in CDM, by steve

This is the third part of the A-CDM high level series in which we dwell into some surprising detail and new interpretations of old things. You can find the first article here and the second here.

In the previous two articles we had a look at the history and overall principles of Airport Collaborative Decision Making (A-CDM), a new way of working being introduced at airports world-wide. Now we will take a deep breath and dig a bit deeper into the intricacies of this concept and working method.

Please, do not stop reading here… I promise you this article is going to be interesting, even enjoyable, reading and quite possibly even bring a few new insights into the aviation world we all like to think we know so well.

I guess nobody will argue about the fact that as an airport or an airline we all work in order to facilitate the journey of the passengers who use our facilities and services. We are also businesses, meaning that we need to generate revenue and a decent profit, as the case may be. We have all kinds of business tools we use to achieve  this and perhaps the most spectacular and visible of these are the airport terminals and the aircraft around it. We tend to think that airlines are in the business flying aircraft, a perception that is of course true, but it is only a part of the whole picture.

If we take a helicopter view of an airline’s operations, we will discover that they are in fact running a carefully balanced network of flights which was constructed to make sure that passengers get the service they require… or something very close to it anyway. As long as aircraft in the network fly as planned, the service to the passengers is being delivered and the business is running smoothly. Disrupt the network and things go haywire in a very short time. Weather, mechanical problems, airport capacity, you name it, are all factors that can result in network disruption. This in turn means financial losses, poor passenger experience and a lot of extra workload to get things back to normal.

Of course the airports and the airlines are in this together and a network disruption at a given airline will quickly impact the airport also since the airport’s resources are used by several clients and the planning of those resources is as finely tuned as the airline network itself.

Let me introduce here something we call the aircraft trajectory.

The trajectory is the line an aircraft will trace on the ground and in the air as it performs a flight. For the sake of simplicity, let’s say that the trajectory of a given aircraft for a given day starts with its first flight of the day. The aircraft is at the gate being readied for its first flight. A given aircraft is of course assigned to several flights a day and it is easy to see that there will be a continuous trajectory of this aircraft from gate to take off, flight, landing, taxi in, at gate, out to take-off, in flight, landing, at the gate and so on. The line is unbroken and we give “names” to each section of that trajectory which is… of course the flight number. So, the first section might be called AC123, the next AC345 and so on. I can almost hear you ask: if the trajectory is a line, what happens when the aircraft is at the gate? When the aircraft is at the gate, the line is not progressing is space at all, but its time-dimension is still evolving. It is costing money, consuming resources even if during that time it is only a “point…” But why do we bother with this whole trajectory thing in the first place?

Well, the plan, the network is in fact a projection of the trajectories into the future. The position of the trajectory in space and time expresses the business intentions of the airline and the airport. Air traffic control and others are engaged in making sure that the actual trajectory of the flight is as near as possible to the plan. If the trajectory is distorted in any way (for instance there is a delay, which is a distortion of the time dimension of the trajectory), the airline business intentions are no longer being fully met. The same is true for the airport’s business intentions, since a delayed flight might very well result in a sub-optimal use of the airport resources. So, we need to protect the trajectory….

Are you with me still?

To protect the trajectory, we have to know and understand the processes that have an influence on the trajectory. I will not bore you with all the processes that we could think of. Instead we will focus on one process we all know well and may be even part of in our daily work. The aircraft turnaround. You know, that period of time the aircraft is at the gate, rounding off one flight and getting ready for the next.

With our new-found knowledge about the trajectory, we now know that the trajectory is idle during the turnaround while its name is changing from one flight number to the next…

The turnaround process is composed of a defined number of sub-processes, each of which has an allocated time to be completed in and the whole thing being driven by the planned start and end-times of the turnaround process itself. Fueling, cleaning, baggage unloading and loading, catering… these are the sub-processes which need to be completed if the turnaround process is to be successful. Meaning, completed on time, without distorting the trajectory.

If something is late, the time dimension of the trajectory is distorted… it might start to creep away from the plan and beyond a certain distortion even impact the network. You know… a delay is a distortion of the time dimension.

So you see, it is really true that no matter how small or big role you may have in a PROCESS like the aircraft turnaround, your performance is essential to keep the TRAJECTORY, the business intentions of the airline and the airport, undistorted.

Of course it is inevitable that things sometimes go wrong. With such a complex operation, involving so many partners and players, it is not easy to recognize that something is about to distort the trajectory and to determine the best way of mitigating the consequences. It would also be nice to be able to see in plenty of time that an intervention will be necessary.

This is where A-CDM comes in. In Airport Collaborative Decision Making we share all available information and also establish so called Milestones, markers inside processes like the aircraft turnaround, which show where the readiness of the trajectory should be at a given, pre-planned time. A-CDM Services, clever little bits of software, watch things as we pass the milestones and they raise an alarm if three is a danger that the next or subsequent milestones are likely to be missed. This is done not to allocate blame but to enable timely and coordinated action with the involvement of all partners to avoid an impending trajectory distortion or at the very least, mitigate its effects. The magic word here is predictability.

With timely intervention, the network will run smoothly, passengers will be happy and our work in general will be less stressful. A-CDM is not a magic bullet. It will not solve problems, only let us know in good time that there is a problem to be solved somewhere down the line.

But of course, this is all we need!



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