SESAR concept - Recent Questions Answered

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 SESAR concept - System Definition and Assessment (SDA)
EUROCONTROL's Experimental Centre (EEC) conducts research and development (R&D) in support of the Single European Sky ATM Research (SESAR) Programme.

EEC's Mid-Term Validation (MTV) Programme is aligned with activities for the SESAR Development Phase (2008-2013). The System Definition and Assessment (SDA) function supports the wider MTV Programme research areas at the EEC to ensure validation of the SESAR 2020 concept.

The SESAR concept presented in the ConOps is at a relatively high level. In preparation for validation activities, the Episode 3 partners are refining the ConOps through Detailed Operational Descriptions (DODs). In the course of this work, the EP3 stakeholders have raised a number of questions.

SESAR concept - Recent Questions Answered

Questions about the SESAR concept should be sent to Ros Eveleigh via the email link (see footer). Note: questioners remain anonymous.

Where specific Questions are discussed further, corresponding Answers are refined and updated as necessary [in square brackets].

Selected recently answered questions (in italics) are listed below.

10 July, 2008

Are the TMR on the RBT fixed for the duration of a flight?

No. The TMR will vary according to the needs of the ATM system for a given time or location and could be defaults carried by the airspace or the trajectory. The TMR could be expressed in terms of time, climb rate or lateral/vertical position. The TMR may be tight for a portion of the trajectory where the traffic is dense, and looser elsewhere. Also, the TMR could be loose for a long lookahead time and tight where the lookahead is short, for example the TMR for the time at the FAF could be 5 minutes when the aircraft is 3 hours from the airport, but reduce to 30 seconds when it is 45 minutes away.

30 June, 2008

How will CDM processes support SBT refinement?

When there is an over-demand that cannot be satisfied by redeployment of any available capacity, the problem is presented to the Users. The Users then balance their business needs to the new situation and submit new SBTs, possibly with the aid of a "what-if" tool. The input that will be provided by the ATM system to the CDM process that will solve the problem has not been detailed by SESAR, but could include: hypothetical delays that would be applied if no action were to be taken; probability of occurrence (less certain the longer the lookahead) and other factors to be defined that would support the User decision making.

27 June, 2008

Is the RBT conflict free?

The RBT is not [necessarily] "conflict free". The rationale of the RBT is that it is agreed before take-off. The quality of data on aircraft position (along-track error) is therefore insufficient for separation assurance purposes.

[The RBT is agreed prior to departure on the basis of being the best balance between the needs of the airspace user and constraints of the ATM system, but not necessarily conflict free. When the RBT is executed, the authorised segments should be conflict free.]

When does the SBT become the RBT?

The SBT is the published business trajectory that is available for collaborative ATM planning purposes, whereas the RBT represents the trajectory that the User agrees to fly and the ANSP and Airports agree to facilitate. The SESAR concept does not specify a time or external trigger when the SBT changes to an RBT. When airports and ATM have agreed on the trajectory to be flown, the data will be loaded into the aircraft’s avionics. This final pre-flight trajectory generated by the on-board avionics is the RBT.

25 June, 2008

What is the difference between 4-D Trajectory Management and a 4-D contract?

4-D Trajectory Management is a fundamental principle of SESAR: it is the process that captures the overall traffic situation in the NOP and controls the development of the business or mission trajectories (BDT to SBT to RBT) in 4 dimensions (latitute, longitude, flight-level and time). Specifically, 4-D Trajectory Management is the process by which the Business Trajectory of the aircraft is established, agreed, updated and revised. This is achieved through Collaborative Decision Making processes between the aircraft operator, ATM and Airports (where applicable) except in time-critical situations when only Flight Crew and Controller are involved.

A 4-D contract is an ATC clearance that prescribes the containment of the trajectory in all 4 dimensions for the period of the contract during which the uncertainty associated with the future predicted position does not increase with the prediction horizon. 4D contracts are foreseen as an en-route control technique, and will not be issued pre-departure or in lower airspace.

23 June, 2008

How will Arrival Management change in SESAR?

Arrival management in the future (a significant evolution from today's AMAN) will consider traffic much earlier for the preparation of the sequence and required spacing to enable an optimal approach to be flown. The aim is to ensure an efficient descent portion of the RBT, undisturbed by tactical actions that might jeopardise the lateral or vertical efficiency of the arrival.

In the future scenario the airport will be served by a set of optimised arrival routes. The arrival manager function will be able to allocate arrival routes and set constraints such as Controlled Time of Arrival (CTA) on merging points with the objective of building an optimum sequence. The CTA technique fits well with Time Based Spacing (TBS) which would follow on after passing the CTA point.

The arrival manager could work as follows:
  1. As aircraft arrive at the arrival manager horizon, the RBT is reviewed and an alternative trajectory may be considered along with a CTA for a merge point.
  2. If aircraft take-off within the arrival manager horizon, their agreed RBT will be influenced by the arrival manager function, which might apply a constraint on a point in the vicinity of destination (such as a target time) with the aim of preparing the arrival sequence. When the aircraft becomes airborne, a CTA is applied.
  3. Aircraft may be required to fly trajectories that are laterally or vertically separated to avoid having to apply in-trail speed control, which might prevent the CTA being respected - a good reason for the deployment of closely spaced PRNAV routes.
  4. As the aircraft approach the CTA point, they will make the transition to TBS and follow the aircraft ahead with the required spacing.
  5. The lateral and vertical trajectory is therefore respected throughout the process enabling the most efficient arrival trajectory in all but speed, which is used to optimise the sequence and achieve the ideal spacing.
The use of improved trajectory data allows the arrival management process start earlier to deliver traffic efficiently into the structured arrival route system at the optimal place and time, which will enable all of the above to happen with minimum tactical intervention. Therefore, the preparation of the arriving traffic sequence is expected to be completed by around 20 mins prior to touchdown, and should start only as early as necessary to achieve the stated objectives. It is thought that at least 1 hour will be needed to smooth out ripples in the traffic delivery, which will be the result of RBT, which is expected to be +/- 2 or 3 minutes.

For information, the UPS hub operation in the USA starts to do arrival management 1000 NM out and is now addressing the problem of integrating departures from airports within this range.

19 June, 2008

In 2020, will the Tower Runway Controller change the sequence of aircraft presented by the DMAN?

It is anticipated that the DMAN will generate an optimal sequence (including spacing) taking into account all constraints, e.g., RBT constraints, wake vortex categories, etc., and the routine task of Tower Runway Controller will be to respect that sequence.

The highly dynamic nature of airport operations means that the system will allow the Tower Runway Controller to make changes to that sequence when required.

The AMAN will work with shared data that enables the automatic consideration of the output of UDPP. That is, the arrival management process envisaged by SESAR will take into account user preferences by access to the outputs of the UDPP.

1-12 June, 2008

Are Tower and TMA Controllers aware of the Network Operations Plan (NOP)?

Yes, the NOP is instantiated through the RBT, which will be available for each flight, much as the flight plan information is available now. The proportion of RBT information available to particular users of the system has not been decided.

Do tactical controllers have responsibility for delivery of this plan, subject to the main priority of safety?

Yes, the RBT in the plan is the trajectory that the ANSP has agreed to facilitate, so delivery-to-plan must be a responsibility of the tactical controller.

Or is it the responsibility of the aircraft operator to keep to the plan?

Yes, it is the RBT that the aircraft operator has agreed to fly; however, the concept recognises that circumstances may occur that prevent an operator from keeping to that plan. In these cases, the RBT will need to be renegotiated, possibly causing the UDPP to be invoked or other collaborative planning actions deployed.

Will an aircraft receive an inferior service if it arrives before or behind plan?

If the aircraft arrives before or after the tolerances of its RBT the service providers cannot guarantee the service received.

Or will the operator be penalised the next day?

The SESAR concept does not describe the application of penalties on the operator (or service provider) for not following the RBT. A penalty the next day might be one of a number of options for managing inappropriate use of the RBT (these would need to be developed if they proved necessary).

18 April, 2008

What is the difference between Dynamic DCB and Complexity Management?

The actions of Dynamic DCB and Complexity Management both react to traffic loading prior to its entry into a sector.

Dynamic DCB can have impacts at local and network levels. As the look-ahead for decisions is up to 2 hours, these will be based on less-certain data as a proportion of aircraft involved may be on the ground at the time of forecast.

Complexity Management decisions apply actions at ATC local-level based on forecasts of aircraft already in flight, which therefore use more precise data, with look-ahead of around 40 minutes prior to sector-entry and could result in minor adjustments to flight profiles.

Dynamic DCB solutions will be more adapted to solve traffic demand/capacity imbalances.

Complexity Management is only expected to be necessary in specific regions of very high traffic density and is therefore an optional layer of the ATM process to be deployed only when fully justified. Unless deployment of Complexity Management can be justified Dynamic DCB alone will ensure acceptable traffic levels whilst maximising performance.
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Last validation: 18/07/2008