Henk J. Hof, Head of ICAO and Concept Unit, Eurocontrol explains Trajectory Based Operation (TBO) with Flight and Flow Information for a Collaborative Environment (FF-ICE)

One year ago, in the May-June 2017 issue of Aircraft IT Operations, I introduced the concept of Trajectory based Operations (TBO). This article will go into more details about what changes it will bring about and how some of those changes will work. But first, I’ll give you a quick summary of why we need TBO. Managing the skies is becoming increasingly challenging, and, in the case of an already crowded Continent such as Europe, that is a present challenge requiring positive action. In that context, the aviation industry, through ICAO (International Civil Aviation Organization) has committed to a major change in the area of air traffic management. Eurocontrol supports and is a main contributor to Trajectory Based Operations (TBO), the exchange, maintenance and use of consistent aircraft trajectory and flight information for collaborative decision-making on the flight (‘collaborative’ here means the involvement of the aircraft operator and all parties that have an interest in a flight). This is sometimes referred to as the paradigm change because it represents such a radical departure from current processes.

In fact, there are a number of trends and developments that contribute to the future challenge of air traffic management (figure 1).

First of all, air traffic volumes are predicted to continue to rise into the foreseeable future at an even faster rate than was the case for past increases. I’ve taken an example (top left, figure 1) of actual growth from 1974 to 2014 with future projections, from one source, looking to the future; but there are many sources available. The bottom line is that air traffic has been increasing for decades and is forecast to continue to increase at an even faster rate. However, an increase in traditional air traffic volumes is not the only thing to consider; there are new entrants to the system that must also be considered. The table, bottom left in figure 1, shows expected growth in the use of remotely piloted and autonomous air vehicles, drones, in various forms and applications. This is an enormous market and these aircraft are airspace users that will require even more access as the sector grows. Top right represents sub-orbital or space flights above flight level 600 and then there are the Googles and Facebooks with projects such as Google Project Loon, using high altitude balloons to provide Internet services to even the most remotes spots on Earth. These are all airspace users; they have to cross airspace with commercial air traffic.

The question is, can the air traffic management we have today deal with these developments, can it cope with such a situation as I’ve just outlined? The answer, we are all agreed, is ‘No’. Let’s start by looking at how air traffic management works today (figure 2).

As readers will be well aware, there are a number of actors in air traffic management and they need to exchange information… the Flight Operating Center (FOC), Air Traffic Flow Management (ATFM), the crew on the flight deck and Air Traffic Control (ATC). They all use automation that supports their decision making and, to a certain extent in some cases, those automated systems are connected but, in many cases, it’s still on voice link, especially between air traffic control and the flight deck.

There is limited co-ordination between the various actors when an aircraft is in flight; the air traffic control process. The Operator submits a flight plan to the ATFM (Air Traffic Flow Management) or, in Europe, the Network Manager; the flight takes off and then things happen and the plan is no longer valid, it is not maintained. The link between the flight crew and ATC is something that happens to take account of various factors such as weather to be avoided, i.e. all tactical interventions. But there’s no link between the two automated systems (ATC and flight deck), another reason why the flight plan is not maintained or followed.

That leads to uncertainties in the system and uncertainties make it very difficult to plan without including wide margins in traffic planning. There’s also imprecise execution. So, if one looks at a flight as phases from flight planning to execution, it is one trajectory which is looked at by air traffic control, by the aircraft operator and by the flight deck crew; but, in practice, those different actors don’t use the same sets of information.

A new approach had to be devised to bring together all the different elements in air traffic management and that is where Trajectory Based Operations (TBO) comes in. It looks complicated at first sight (figure 3) but I will endeavor to explain it.

Trajectory Based Operations brings everything together to ensure that all the actors in the system share the same information and maintain the same information. Only then can uncertainty be reduced to establish a basis for automation. Near the top of figure 3, are the processes followed by the Airspace User (AU) from scheduling (a more commercial activity that is of less interest from an air traffic management point of view except for capacity planning reasons) to flight planning, dispatch and execution of the mission. On the next level down is Capacity Management (how to organize the airspace, how to do the rostering, how many sectors need to be opened, etc.) which then goes to Flow Management where traffic flows are considered to ensure that the system is not overloaded, in which case there will need to be further optimizations and, if needed, regulations. From an airport perspective, there is departure and arrival management: and of course, that information can only be looked at during the flight planning mode. Then, Air Traffic Control will be involved in the final stage of tactical planning with Traffic Synchronization and Separation Management.

These are the process being considered as part of the new approach, bringing it all together; from an airport perspective, from an airspace user perspective and from an air traffic control perspective; so that all of these processes should interact with each other using the same information; namely, the trajectory of the aircraft. That is the essence of trajectory management and Trajectory Based Operation: to take processes and actors who are loosely coupled today with the objective to make them all better coupled and synchronized.

Today, the Airspace User submits a flight plan which is filed and ‘forgotten’, and the flight is executed. The plan for TBO is to have consistent flight information available before the departure. The next step will be to submit that flight information, which will be more than today’s flight plan with more fields in a richer format that can include more information such as 4D trajectory information. The airspace user will then be able to submit its optimal flight profile to start a negotiation/optimization, knowing the constraints in the system which are made available. The next step for TBO is to support negotiation/optimization of the flight trajectory when the flight is active i.e. during the execution phase. That really establishes a link in the triangle between the flight deck, the flight operations center and air traffic control who all need to exchange information. If that can be achieved then it is possible to increase the accuracy or reduce the uncertainty of the trajectory.

Today, the flight plan is submitted including the type of aircraft. Air Traffic Control uses static models to assess the trajectory of that aircraft based on static performance data. It is well known that different aircraft within different airlines are not the same; they don’t have the same envelope in terms of optimum and flight profiles. In the pre-departure negotiation, the first step with TBO, that information can be exchanged so that these parameters can be shared to make the trajectory more accurate.

In the post-departure phase, this can all happen in flight so that things can be optimized, an even better option. With more accurate trajectories, it will be possible to give better and more accurate clearances to aircraft. Today, a lot happens by voice plus there is some controller-pilot datalink communication which will, in future, be further used to increase the precision of the instructions given to the aircraft. And, in the final phase, there will be much more precise clearances between the different automated systems. Of course, there will still be a human in the loop to execute. But, overall, this will lead to a much better integration of all the air traffic management components to integrate all the processes.

Just as figure 4 shows the evolution of TBO, the concepts that are being developed in ICAO and which are subject to validation in programs such as SESAR and NextGen, Figure 5 shows the changes that will come about with the new system.

To start by focusing on the first phase, the pre-departure phase will be supported, as are all the phases, by more and richer exchanges of information, Flight and Flow Information for a Collaborative Environment (FF-ICE). The first phase is the planning phase which is already quite advanced, i.e. past concept stage, with a deployment program running in the European Network Manager to implement this with flight plan providers and some airlines. It will replace the current flight plan with a much more dynamic and richer format, is more flexible and, using current technology, more scalable to allow it to grow and for information to be added. It’s also based on system-wide information management (SWIM) and is the foundation for Trajectory Based Operations.

There will be some new services as part of this first implementation; a planning service and a trial service. For example, using the trial service, airspace users will be able to submit a flight plan with FF-ICE that will be called eFPL and see how the system reacts to it. There will be a more intense and more detailed interaction between the aircraft operator and air traffic management.

The transition to FF-ICE will not be the same as the previous flight plan change, the flight plan 2012; it’s a performance based deployment. It’s not a big bang transition, so it will be possible to carry on with the current flight plan for some time; but if an airline wishes to make use of these new services, to make use of more information, then it will be necessary to make the transition to this new process.

One part of the information will be flight prioritization; so, within the fleet, it will be possible to identify the relative priority of flights, which will then be available to air traffic management and, if the automation is there, that can be taken into account. Some existing services such as filing service to file the flight plan will remain.

In terms of progress, the ICAO provisions, the standards and recommended practices, are ready at a high level: they had not been published at the time of writing but publication is pending. ICAO is also working on detailed implementation guidance.

FF-ICE is supported by an exchange model FIXM (Flight Information eXchange Model) at a technical level. This is all in full progress; there are implementations for Version 4 available and being tested. It’s something that is developed by the industry in the US, Europe, Australia and other parts of the world. The first implementations will be in Europe around 2020-2021 and in the USA.

To look briefly at the next phase, in the flight execution phase it will be possible to negotiate the flight trajectory while the aircraft is in flight. That is a very difficult step to take because it requires a full integration of the ground environment. So, today, the various Air Navigation Service providers have various data processing systems of different brands and types and these flight data processing systems need to interact, need to share the same trajectory and need to maintain a consistent trajectory; that is a challenge.

Here are a few examples to explain what TBO will look like in action. For instance, while the aircraft is in flight there might be a need or a wish to negotiate for downstream changes to the trajectory for a variety of reasons. Perhaps better routes will become available, military airspace will be deactivated, weather changes, flight optimization… readers will know the reasons. With TBO, this negotiation can be done from the flight operating center or the flight deck and the information environment will enable this to be supported by automation. It can also be done the other way, from an ANSP (Air Traffic Service Provider) to the flight deck. Such negotiations will not be concerned with the current airspace within which the aircraft is flying because that is within the authority of Air Traffic Control that is then controlling the aircraft. That co-ordination also takes place with the ground because, if there’s a change to the flight trajectory, it will need to be synchronized with the ground so that everyone has the same view. The outcome of that negotiation will always be a delivered through a clearance; so that part of the process is not going to change. A clearance from Air Traffic Control to the flight deck will always be given before any change in the trajectory can be executed.

Another example of what this means is the continuous notification ‘ground to ground’ of changes to flight trajectory. It isn’t yet happening at the level of detail to which it should happen. For example, if there is some deviation from the previously established trajectory, this is something that, on the ground, needs to be coordinated and updated so that all the ANSPs have the same information on the trajectory. And only then, there is the sharing of the same information on which automation can be based. What this will deliver is greatly increased flexibility for aircraft operators.

Another example (figure 6) shows a situation when the aircraft is in flight over Italy and a Hotspot occurs in Zurich with some saturation from too much traffic which needs to be resolved. So, while the aircraft is in flight, from the airline or operator’s FOC or, if there is no FOC, it can be done from the flight deck using the electronic flight bag, a re-routing can be negotiated and the trajectory changed.

In short, Trajectory Based operations will deliver increased flexibility, higher efficiency and less uncertainty.

In summing up, Trajectory Based Operation represents a paradigm change which, while it is a little while off, is coming towards us, and the industry is actively preparing for it with a good level of industry participation on the ICAO panel that I chair. Also IATA is actively involved and sees this as the future. That future will not happen simply by switching a switch but is a stepped process. TBO supports collaboration, especially in the triangle between flight deck, flight operations center and air traffic management, leading to enhanced performance; and it should support all airspace users.

Deployment will be a step-by-step process with the first phase being FF-ICE/planning replacing the current FPL. The second phase will be execution which, when we talk about full TBO, will require eventually the integration of the aircraft.

In ICAO, we are working on this with the first implementations to take place by 2020. The TBO concept will be presented to the Air Navigation Conference in 2018 and the ICAO General Assembly in 2019 for TBO to be fully integrated in the ICAO Global Air Navigation Plan.

Transformation of air traffic management is a natural process but it’s something that has to be done because simply extending past practices will not be an option. We must transform the air traffic management system and Trajectory Based Operation is the way to go.

Henk J. Hof started his professional carrier in 1985 as policy advisor on Communication, Navigation and Surveillance matters for the Dutch ATC authorities. He was member of the ICAO FANS I and II committees and member of a number of ICAO Panels. In 1991 he joined EUROCONTROL as Project Manager responsible for the standardisation and implementation of the Aeronautical Telecommunication Network (ATN). As Head of the Master Plan Maintenance Unit and Leader of the SESAR Master Plan Work Package, he was responsible for the development and maintenance of the European ATM Master Plan. In his current position, Mr. Hof is responsible for the contribution of the EUROCONTROL Agency to ICAO and for strategic initiation and facilitation on Concept development.

The European Organisation for the Safety of Air Navigation, commonly known as Eurocontrol, is an international organization working to achieve safe and seamless air traffic management across Europe. Founded in 1960, Eurocontrol currently has 41 member states and is headquartered in Brussels, Belgium. Eurocontrol is committed to building, together with partners, a Single European Sky that will deliver the air traffic management (ATM) performance required for the twenty-first century and beyond. The organization has expertise covering both operational and technical elements; advising on both civil and military aspects of ATM; having experience at bringing States with different needs together for a common goal.