Implementation of TBO

Continuous Descent and Continuous Climb Operations (CDO and CCO) are clear examples of the use of TBO, where optimal flight paths are intended in order to achieve the best economic/environmental benefits (see Figure 2.12). These opera-tions could save from 50 to 200kg of fuel per flight using a single CCO or CDO, compared to a non-optimized profile (Eurocontrol,2017l). Moreover, according to (NASA,2013), data from the 27 busiest airports in the U.S.A. indicates that 188 mil-lion gallons of fuel per year could be saved with continuous climbs, and 218 milmil-lion with continuous descents.

CDO procedures were first evaluated at Louisville-Standiford International Airport, tested at Atlanta/Hartsfield-Jackson International Airport, and demonstrated at the Miami International Airport in May 2008. However CDO interaction with non-CDO flights, pilot adjustments to drag-generating devices (throttle changes, flap settings, landing gear extension), and further studies on the benefits of these operations, have provoked delays in their full implementation.

On the other hand, CCOs are expected to be included as a part of a SID(Standard Instrument Departure), so ATC and flight crews have a fixed procedure defined in advance.

Ideally, CDOs use minimum engine thrust in a low drag configuration prior to land-ing, while CCOs use climb engine thrust and speeds until reaching cruise altitude (faster than step climbs). Both CDOs and CCOs are highly encouraged in Europe. In consequence, their associated ICAO manual have been issued, (ICAO2010), (ICAO 2013), respectively.

In addition to CCO and CDO techniques, 4D operations have been addressed in both SESAR and Next-Gen projects, where the time integration as an extra dimen-sion to a 3D trajectory allows to consider delays as distortions from the reference trajectory.

The 4D concept relies on RBT (Reference Business Trajectory) that airspace users choose to fly, and ANSPs to provide. This 4D (time-based) operations are considered as milestones towards Trajectory-Based Operations due to their level of information sharing between ATC and flight crews, as well as the required avionics, and required levels of on-board automation.

In the SESAR context, 4D trajectory management is divided in two stages, initial 4D (i4D), and Full 4D.

The i4D consists in using airborne computed predictions in ground systems to de-fine a target time of arrival at a merging point to each aircraft converging to this point (e.g. Initial Approach Fix), such that traffic is sequenced. This implies fewer tactical interventions and improved de-confliction situation.

Although Controlled Time of Arrival (CTA) is a functionality available in modern

FIGURE2.12: Concept of CDO (EurocontrolOctober 2011).

Flight Management Systems, its use to improve efficiency in traffic management has been explored only recently. According to (Klooster, Amo, and Manzi, 2009), the wind data available to the FMS, the speed and altitude constraints, and configura-tion for landing, are determinant factors that have a substantial impact on the CTA accuracy. Therefore, higher wind modelling accuracy may considerably improve the accuracy of the CTA operation.

Implementation of the i4D was performed successfully the 10th February of 2012 with an A320 test aircraft flying from Toulouse to Copenhagen, Stockholm, and then back to Toulouse, underlying the datalink interoperability (exchange of trajectory predictions between an advanced aircraft FMS and the ground automation systems) as a key element (Mutuel, Paricaud, and Neri,2013), (SESAR Factsheet2012).

Regarding the Full 4D Trajectory Management concept of SESAR (4D gate-to-gate), it was initially planned to start the implementation between 2017 and 2019, but it was delayed due to its impact on airborne and ground systems, as well as in the existent procedures.

In order to advance towards full 4D trajectories, some requirements for on-board systems and crew procedures need to be accomplished. For example: advanced fea-tures for FMS (improved wind modelling and update in the FMS), improved FMS ability to meet time constraints, improvement of personalized, filtered, information sharing like datalink (CPDLC and ADS-C EPP) for transmission of altitude, time, speed predictions, aircraft gross weight, etc., and introduction of SWIM (System-wide Information Management), just to mention a few.

Moreover, considering that:

• Conflict detection is more complex since trajectories will no longer follow stan-dard airways, making conflicting points moving locations.

• TBO improvement in only a part of the trajectory will limit the benefit.

• Action of controllers will have an impact in the trajectory as a whole, since the reach of control points needs to be done in time and not later or earlier.

cost benefit analysis are being developed to ensure that costs associated with 4D avionics are justified by the potential benefits.

2.3. Conclusion 31

2.3 Conclusion

A summary regarding the current air traffic organization has been provided, describ-ing the main features of the CNS-ATM and MET services. Then, after recognizdescrib-ing the imminent growth of air traffic, the solutions adopted by the European Union and the United States of America were described as a part of a modern air traffic organization.

The advantages of a modern organization of air traffic have been pointed out, and the gradual shift from fixed routes and ATC clearances towards flexible trajectories, higher levels of on-board automation, reduced aviation congestion, and improved safety, has been described.

Moreover, the use of new technologies such as ADS-B/C, Global Navigation Satellite Systems (GNSS), and their interaction with current ATM has also been described.

Taking into account that the main goal of SESAR and Next-Gen projects is focused on enhancing the airspace capacity while maintaining safety, the nearest concept to be implemented is TBO, therefore, the Continuous Climb/Descent Operations and the 4D concept are of great interest. This is expected since the Freeflight concept for high traffic regions will result in an increase of air conflicts, and automatic conflict resolutions may end in a permanent state of routes reconfiguration.

Furthermore, certain similarities between the objectives of this thesis with respect to the expected benefits of TBO are found.

33

Chapter 3