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in flight Trajectory optimizAtion through advanCed simulation TechnICs

European Union
Complete with results
Geo-spatial type
Total project cost
€549 848
EU Contribution
€300 221
Project Acronym
STRIA Roadmaps
Vehicle design and manufacturing (VDM)
Transport mode
Airborne icon
Transport policies
Societal/Economic issues,
Environmental/Emissions aspects,
Transport sectors
Passenger transport,
Freight transport


Call for proposal
Link to CORDIS

The Commercial and Airline Pilots are skilled to deal with their aircraft emergencies. On the contrary, when the occurrence of unusual situations, requires trajectory change during IFR navigation, pilot in command, involved in a short time analysis and synthesis, could be not able to consider all those aspects affecting the new flight trajectory negotiation.

In such situations the pilot may have great advantages in using additional capability providing supports and increased awareness in answering to trajectory change requests. A Decision Support System (DSS) can be introduced to allow the pilot to have in every instant the awareness of alternative paths, suggested by the tool, that can decrease trip time, fuel consumption and consequently chemical emissions and noise.

TACTIC project contributed to analyse and solve the problem of characterising the pilot’s behaviour in decision making when unforeseen events force a change in the reference trajectory with or without the help of an on-board Decision Support System.

The main objective of TACTIC was to evaluate such a Decision Support System. The quantification of the advantages of such an interactive tool was the main output of the project. Eventual suggestions for enhancements of the tool as well as new interaction modalities or uses will also be provided.

To reach this objective, a simulation environment that replicated present and future ATC and airborne system configurations were set up. This test bed environment was used to perform a set of simulations to study:

  • the impact of different pilot behaviours in the decision-making process when unforeseen events force a change on the reference trajectory;
  • the impact of the Decision Support System on pilot workload and situation awareness and aircraft/airspace performances (e.g. fuel consumption, airspace capacity and efficiency, noise abatement) in all the phases of flight.


Parent Programmes
Institution Type
Public institution
Institution Name
European Commission
Type of funding
Public (EU)
Specific funding programme
JTI-CS - Joint Technology Initiatives - Clean Sky
Other Programme
JTI-CS-2013-1-SGO-03-023 Simulation of Pilot Behaviour and Clearance Negatiation in Trajectory Changes Management



ACTIC main results may be resumed as follows:

From the analysis of the communication logs between pilots and ATC operator during the negotiation subsequent to the appearance of the risk zone it was deduced that using the DSS requires a trajectory negotiation based on published waypoints requires less phases:

  • The pilot suggests an alternative trajectory and usually the ATCO approves it.
  • After this first phase, usually the ATCO requires a confirmation when the new trajectory begin to converge to the original flight plan.

On the other side, without the DSS:

  • The pilot usually asks for a new heading and the ATCO agrees;
  • While deviating from the flight plan the ATCO requests an estimation of the distance to be covered before resuming the navigation on the filed flight plan. Similar to the DSS case, a confirmation is requested when the flight should converge to the original flight plan.
  • In some cases, the pilots asked for a new corrected heading causing an additional negotiation phase.

Using the DSS also reduced the radio frequency usage in terms of number of calls and total duration of the transmissions.

The simulations highlighted no relevant differences in the average duration of the radio communication nor in the total duration of the negotiation. The ATCO always requested a confirmation when the aircraft is clear of the bad weather zone and about to converge to the original flight plan. So the total duration of the process is almost only related to the bad weather zone extension. This happens even when the pilot asks for a flight plan revision which should completely substitute the old one.

The DSS based negotiation identified the trajectory earlier and more clearly. In the first radio communication session the trajectory is already defined; if the ATCO accepted the first trajectory proposal, the whole negotiation process would terminate in a single ATCO-pilot exchange.

Without the DSS, the trajectory negotiation is composed of three phases, all of them required to determine the geographical form of the deviating path. First the pilot requests a new heading to stay clear of the bad weather zone. Usually, after a while, the ATCO initiates a radio communication asking how long the pilots need to deviate. After covering this distance, the pilots or the ATCO initiate a communication to negotiate the point where the original flight plan will be resumed.

Without the DSS, the whole negotiation process has the following characteristics:

  • The trajectory is not defined until the last phase of the negotiation, when the resume point is identified.
  • Communication follows no predetermined timings. A variable amount of time can pass between the trajectory negotiation steps, according for example to the situation of the surrounding traffic.
  • Communication can be initiated by ATCOs or pilots, without any defined rule.

On the contrary, the DSS suggests a more standardised negotiation which defines the trajectory immediately with more defined roles between pilots and controllers.

From the point of view of the fuel consumption and of the emission of pollutants (CO2, NOx), during the simulation a dedicated module of the CS system computed and collected data that can be resumed in the following table of fuel consumption and emission savings of NOx and CO2 when using the DSS with respect to the simulations without DSS aid. The table averages data for both airline and commercial pilots.

Fuel saving using DSS CO2 saving using DSS NOx saving using DSS:

Case 1 5.62 % (70 Kg) 5.62 % (272 kg) 4.25% (588 g)

Case 2 5.31 % (89 Kg) 5.31 % (281 Kg) 2.11 % (324 g)

Case 3 1.03 % (1.03 Kg) 1.02 % (24 Kg) -0.9% (-152 g)

Average 4 % 4 % 1.82 %

Fuel savings and pollutant emission

The following considerations apply to the results of fuel consumption and pollutant emissions:

  • DSS suggests more direct trajectories generally leading to save fuel and consequently to reduce pollutant emissions.
  • Pilots flying without the aid of a DSS tend to join the scheduled flight plan earlier.

The DSS led to the best results when it was used in a less constrained airspace system. One of the simulation scenarios (Case 3 in the table above) included a Point Merge System which requires more adherence to the flight plan in order to arrive at the merge point and follow the sequencing legs. In this context the fuel saving is considerably reduced because the air traffic Controller will request to resume earlier the previous flight plan.


Lead Organisation
I.d.s. - Ingegneria Dei Sistemi - S.p.a.
Via Enrica Calabresi 24, 56121 Pisa, Italy
EU Contribution
€224 330
Partner Organisations
Deep Blue Srl
Via Ennio Quirino Visconti 8, 193 Roma, Italy
EU Contribution
€75 891


Technology Theme
Aircraft operations and safety
Trajectory Based Flight Operations
Development phase

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