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SOURDINE–II: SOME ASPECTS OF THE ASSESSMENT OF NOISE ABATEMENT PROCEDURES

Ruud den Boer, Collin Beers, Hans Huisman, Mariska Roerdink, Jelmer Scholte,

rgboer@nlr.nl, csbeers@nlr.nl, huisman@nlr.nl, mroerdin@nlr.nl, scholte@nlr.nl,

National Aerospace Laboratory, Amsterdam, The Netherlands

Keywords: ATM, Noise Abatement Procedure (NAP),Environment, Real-Time Simulation,Safety, Human Factors

AbstractThe Sourdine-II (Study of optimisation

procedures for decreasing the impact of noise) projectis a 5th framework RTD project of the EuropeanUnion focusing on the development and assessmentof Noise Abatement Procedures (NAPs). It startedNovember 2001 and will be finished August 2005.Four parts can be distinguished in the study:

1. Procedure definition (approach and departure)

2. Further development of assessment tools

3. Procedure assessment

4. Procedure implementation

In this paper, the project organization and appliedmethodology, as well as the first two topicsmentioned above, are discussed very briefly.However, the main emphasis in this paper is on partsof the procedure assessment work.

In the Sourdine-II project a selection of approach anddeparture procedure is assessed with respect to safety,environmental impact (noise and emissions),capacity, Costs/Benefits, and acceptance by end-users(pilots and air-traffic controllers). This paper presentsan overview of the initial results of the assessmentwork, with emphasis on the real-time simulationswhich were executed to determine the acceptance byend-users. Also, a brief overview of a part of thesafety study is presented.

The work on the procedures implementation plan hasjust started and is not included in this paper.

Both in the real-time simulations as well as in thesafety analysis bottlenecks for the implementation ofthe concept are identified. These bottlenecks will helpthe operational concept developers to findimprovements for the operation before a successiveassessment is done.

1. IntroductionWith the continuing growth of air-traffic as well

as the ever increasing level of urbanisation aroundmost airports, the impact of aircraft noise andemissions on the quality of life for the surroundingcommunities has become a serious issue to be dealtwith. Many airports already face the conflictingproblems of increasing their airport capacity to meetthe amount of traffic, and the increasing pressurefrom the general public to reduce environmentalimpact, particularly noise and emissions, of theincreased traffic volume. This has already resulted inspecific local constraints to the operation of aircraft,not only around major airports such as Amsterdam(Schiphol), London (Gatwick) and Frankfurt, but alsomore regional airports are already experiencing thepressure to impose constraints to aircraft movements.Therefore, reduced nuisance to the community is aserious issue for the air-transport industry if theprojected sustained growth is to be pursued. Work inthree main areas can be identified to improve thesituation:

1. Source noise reduction2. Regulation and land-use planning3. Noise Abatement Procedures.Many efforts are already being undertaken (and

are still continuing) to reduce the source noise itselfby the introduction of more silent aircraft andengines. Also, regulations are nowadays applied atmany airports in the form of restrictions to olderairframe/engines, curfews and noise charges. At theplanning of new urban areas it is pursued more andmore to avoid areas which will be affected by aircraftnoise. A third way of improving the situation is thedevelopment and implementation of new approachand departures procedures to provide increased air-transport capacity while maintaining a high level ofsafety and complying with ever-stricterenvironmental constraints.

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This topic is adressed in the Sourdine-II project.The main objectives of the project are:• Definition of new noise abatement procedures

(both approach & departure)• Further development of assessment tools• Assessment of a selected set of procedures

with respect to the following parameters:• Environmental impact• Safety• Capacity• Acceptance by end-users (pilots & air-

traffic controllers)• Cost /Benefit

• Define implementation plan for selectedprocedures and define requirements for toolsneeded by pilot and air-traffic controllers.

2. Overview of SOURDINE-II

2.1 OrganizationThe topic adressed in Sourdine-II requires a

multidisciplinary approach. Therefore a consortium isformed with partners who can contribute in differentexpertise areas. The consortium consists of:

AENAAirbus – FranceEurocontrol Experimental CentreINECOIsdefeNLR (Co-ordinator)Sicta.

ActivitiesActivities• Validation Methodology

• Definition New Procedures

• Validation New Procedures on Safety, Efficiency, Environment and Finances

• Simulations• Calculations• Analysis

• Produce Implementation Plan for New Procedures

Sourdine IISourdine II Expert panelExpert panel• Airlines• ATS Providers• Airports• CAAs• FAA• Industry

– Aircraft– Engines– Avionics– ATM components

Main PartnersMain Partners

• R & D• ATS providers• Airline• Aircraft Manufacturer• Engineering/Consulting

Figure 1: Organization of SOURDINE-II

Although many expertise areas are covered byconsortium, also an expert panel is formed to coveradditional expertise areas (for instance expertise ofengines, small business jets, airport management,regulation issues) needed for the proceduredefinition. For the development and acceptance ofan implementation plan for the new procedures, thesupport of many different type of organizations(Airlines, ATS – service providers, airports, CAAs,Industry etc.) is required. Both aspects were coveredby the Sourdine-II expert panel at the same time:coverage of additional expertise areas andcommitment to the implementation plan. Figure 1presents the involvement of the expert panel in theproject.

2.2 MethodologyIn Sourdine-II, many (dozens) approach and

departure procedures have been defined (seereference 1). For all these procedures, single eventsimulations have been performed for the A320 andA340 aircraft (see reference 2 and section 4). Basedon these simulations and the inputs of sessions with

Figure2: Working methodology

the expert panel, 4 approach and 2 departureprocedures have been selected, as well as anapproach reference procedure and a departurereference procedure (see reference 3 and section 5).

So far, the procedures are defined in a genericway, i.e. a vertical profile, speed, thrust andconfiguration development. For (most of) theassessment with respect to the parameters mentioned

Implementation Plan

A/P noise

acceptance

A/P emiss.

procedure design

noise(s.e.s.)

procedureselection

4 approach2 departure

cost/benefit

safety

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capacity

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in section 1 (see also figure 2), the procedures have tobe embedded in an operational concept. Safetyassessments have been done partly based on a Madrid(Barajas) based concept and on a Amsterdam(Schiphol) – based concept (see section 6). The sameAmsterdam (Schiphol) concept was used during real-time simulations to assess the acceptance by pilotsand air-traffic controllers. Airport noise andEmissions, as well as Capacity and Cost benefitassessments, have been done for Madrid (Barajas),Paris (Charles de Gaulle), Naples (Capodichino) andAmsterdam (Schiphol).

The next step after all the assessments, is thefeed back to the procedure designers and therefinement of the procedures. After some iteration,the procedure will be fixed and an implementationplan will be made.

3. Scope of this paperThis paper only presents a small part of the

Sourdine-II work. For the procedure definition andthe Single Event Simulations, the reader is referred tothe Sourdine-II website: www.sourdine.org. Thestudy of the CBA and the implementation plan are atthe very end of the project and were not finalised atthe paper submission date. The further developmentof the INM – tool for the airport noise calculationsand the use of multi-configuration and multi-speedNPD-curves will be presented in 2005 at anotherconference (paper has been submitted. Results of thecapacity assessment and the Airpoirt noise andemissions study will be presented at theAIAA/AAAF Aircraft Noise and EmissionsReduction Sympoium (see reference 4). The mainfocus of this paper is on the assessment of theacceptance of the noise abatement procedures byPilot and Air traffic controller (section 8). Also, abrief overview of a part of the safety study ispresented (section 7).

4. Single event simulation (example)The objective of the single event noise

calculations was to identify approach and landingprocedures that are efficient in terms of noiseexposure reduction. All procedures defined in the“procedure design”- work package were evaluated inthis way. Note that the single event simulations weredone on basis of manufacturers performance toolsand resulting trajectories reflect performancecharacteristics of the aircraft. However, otheroperational, regulatory and pilot perception aspectswere NOT subject of the single event simulations

study. The single event simulations produced resultsin the form of graphs of the vertical, speed and thrustprofile. As an example, for some of the selectedprocedures (see section 5), the vertical path andmaximum noise profile is presented in figure 3.

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Figure 3: Vertical profile and maximum noise levelfor the procedure I (reference approach,blue),

procedure III (green),procedure IV (red) and V (yellow).

5. Selected proceduresBased on the results of the Single Event

Simulations and the results of the expert panelmeetings, the following procedures were selected forfurther, detailed assessment:

Approach Procedures (4+1 reference)• Procedure I: Reference with level deceleration at

3000ft• Procedure II: Basic CDA with 2° initial FPA• Procedure III: CDA with 2° initial FPA and

increased final glide slope (4º)• Procedure IV: CDA with constant speed,

variable FPA segment at landing configuration• Procedure V: CDA with constant speed, variable

FPA segment at intermediate configuration

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Departure Procedures (2+1 reference)• Procedure 1: ICAO A• Procedure 2: SII Optimised Close-in• Procedure 3: SII Optimised Distant

For the evaluation with respect to safety and useracceptance, first all six selected procedures wereevaluated on an intermediate level. Next, twoprocedures (II and V) were selected for detailedanalysis with respect to safety and user-acceptance.In the user acceptance study, also the effect of addingspeed constraints to procedure II was investigated.The procedure II with speed constraints is notified asprocedure II-A.

6. Concept of OperationThe Sourdine-II operational concept for the

Schiphol related assessment work is based on thecurrent night transition procedures. Only the positionof some of the waypoints has been slightly changedand therefore some of the according names werechanged as well. The runway combination used isbased on the Mode 2 configuration (wind comingfrom the South): inbound runway 18C and 18R,outbound runway 24 and 18L. Figure 4 shows thefixed arrival routes from the initial approach fixes(IAFs) River and Sugol to runway 18R and fromARTIP to 18C. Traffic from River and Sugol will bemerged between Micol and Narsi. If required,controllers can instruct directs to Narsi for aircraftflying between Sugol and Micol. These so-calledRNAV shortcuts can be used to optimise the trafficsequence.

Figure 4: Operational concept

7. Safety risk assessment The approach adopted for the safety risk

assessment is the stepwise, iterative approach of theTOPAZ methodology [Ref. 5]. This approach allowsfor the use of Monte Carlo simulations for selectedsafety aspects [Ref. 6].

First the exact objective and scope of the safetyrisk assessment was identified, includingdetermination of an initial target level of safety. Aspart of the scoping, an operational identification ofthe safety issues of the 6 procedures (four approachand two departure) was made from a pilot’s point ofview. The safety issues identified during this processare given in short.

For approach procedures II and especially III itwas identified that possible excess speed at glideslope intercept may cause an unstabilised approach.Furthermore, the steep final glide slope of procedureIII potentially increases workload, and this non-standard operation requires special analysis ofacceptance and of obstacle clearance surfaces. Toovercome some of these issues, the operationalconcept developers decided to define a variant ofprocedure II, named procedure II-A, in which speedconstraints are of force.

In procedure IV a possibly steep intermediateapproach segment could result in glideslopeinterception from above, with the potentialconsequences of glide slope undershoot andunstabilised approach. Also, potential flight pathcontrol problems could occur, which could lead toincreased workload and an unstabilised approach incase the path is too shallow. For procedure V thesame issues are identified, though all less severe.

The main issue identified for the departureprocedures was speed control problems at lowpowersetting at the OEI climb thrust. This is expectedto be more severe for procedure 2 than for 3.

Because of constraints, it was unrealistic toperform an in-depth safety risk assessment for allprocedures. Based on the operational safety issuesabove and other arguments (on capacity, cost-benefit,acceptability, etc.), the ‘most promising’ procedureswere selected for the scope of the safety riskassessment: approach procedures II-A and V anddeparture procedure 2.

In the following we illustrate the safety riskassessment cycle performed for approach procedureII-A. For this procedure an operation on Schipholairport was determined by the operational conceptdevelopers. Safety experts verified this oncompleteness and consistence regarding the systems,

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human roles, procedures, and environment, and allinteractions.

As many and as diverse hazards as possiblewere identified for this operation. This was done bymeans of hazard brainstorms with operational expertsaiming to identify ‘functionally unimaginable’hazards [Ref. 7], and by means of search in theTOPAZ hazard database. The hazards werestructured into five conflict scenarios, describing allplausible ways in which they can lead to or affect aconflict situation:

1. Conflict between merging aircraft2. Conflict between aircraft flying in trail3. Conflict between aircraft on parallel localizers4. Conflict at localizer intercept5. Wake vortex encounter

The location of the conflict scenarios in the contextof the operation is illustrated in figure 5:

Figure 5: Locations of the conflict scenarios.

For each conflict scenario it was assessed howoften the conflict occurs and how often it ends in aspecific severity class. For conflict scenarios 1, 2, 3,and 5, an argumentation-based approach was used,and for conflict scenario 4 a simulation-basedapproach. Both these approaches rely on structuringof inputs retrieved from experts and statistics. In theargumentation-based approach this information isevaluated directly via argumentations. In thesimulation-based approach this information is used todevelop a Monte Carlo simulation model, to assessthe accident risk for this model, and to assess biasand uncertainty [ref. 8]. This way, an expectedaccident risk value and a 95% uncertainty area forrealistic accident risk is retrieved.

The risks were classified by combining severityand frequency estimates and comparing to the targetlevel of safety. For conflict scenarios 1 and 3, the riskwas assessed to be better than the initial target risk.

For conflict scenarios 2, 4, and 5 it could not be ruledout that the risk was worse than the initial target. Forthese conflict scenarios safety bottlenecks wereidentified, which can help operational conceptdevelopers to find improvements for the operation. Itis considered most logical to do a new cycle of thesafety risk assessment once the operation has beenimproved. It is recommended that then also asimulation-based approach is adopted for conflictscenarios 2 and 5. It is also recommended to improvethe derivation of the target level of safety.

8. Acceptance by pilot and air-traffic controller

8.1 RTS experiment set-upThe real-time simulations (RTS) were

performed at the NLR and were divided in aprototyping part and an experiment part. Thesesimulations mainly focus on the usability and theacceptance by the users of the proposed proceduresand tools.

The prototyping was performed with APERO(Advanced Prototyping & Evaluation for Research &Operations) and NARSIM (the NLR Air TrafficControl Research Simulator). APERO (figure 6) is aneasy to configure single pilot cockpit. APERO is usedfor prototyping of the new cockpit displays and toolsused by designers in combination with test pilots ortechnical pilots.

Figure 6: APERO

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Conflict scenario 1Conflict scenario 2Conflict scenario 3Conflict scenario 4Conflict scenario 5

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NARSIM (figure 7) is a high fidelity ATCsimulator, which is used for prototyping and finalsimulations. NARSIM is used to get initial feedbackon tools and procedures as well as to evaluatecontroller workload and acceptance.

Figure 7: NARSIM

For the experiments both NARSIM and theGRACE (Generic Research Aircraft CockpitEnvironment) flight simulator were used. GRACE(figure 8) is used to evaluate crew interaction andworkload as well as to gain feedback on acceptabilityof new displays, tools and SII procedures.

Figure 8: GRACE

8.2 RTS Prototyping resultsFrom the prototyping sessions it can be first of

all concluded that these sessions are very helpful in

getting early controller and pilot feedback concerningthe developed procedures and tools as well as theverification of the simulation set-up. The result ofthese prototyping sessions is a technically validatedsimulation environment, which provides thecontrollers and pilots with an optimal workingenvironment for the operational validation of theSourdine-II procedures.

For the ATC part of the prototyping thecontroller provided feedback on the Sourdine-IIprocedures, proposed tools, human machine interface(HMI) and the content of the Digital – AutomaticTerminal Information Service (D-ATIS) and RadioTelephony (R/T).

Several adaptations to the controller workingposition (CWP) were prototyped during thesesessions. These adaptations consisted of a ghostingand a monitoring tool, Short Term Conflict Alert(SCTA) functionality within the TMA and changes tothe radar display. Especially the ghostingfunctionality was considered very helpful in assistingthe controller with the merging of two traffic streams.

A ghost plot of an aircraft provides position-information of that aircraft on a different route, calledghost-route (figure 9). In the Sourdine-II case, ghostplots are created for the aircraft from the SUGOLIAF and are projected on the RIVER approach route.This ghost plot gives the controller information aboutthe position of an aircraft from SUGOL, relative tothe stream of aircraft from RIVER, in which it shouldmerge. There are two ways of presenting a ghostplotto the controller: based on distance to go, or on timeto go (figure 9).

Figure 9: Ghosting algorithm options

In the distance-to-go algorithm, the distance of theaircraft until the merging point is determined. Thenthis distance is backtracked along the ghost route, inorder to find the position of the ghost plot. Thedistance to fly is the same for the aircraft itself, as foran aircraft flying at the location of the ghost plot. Theghost plot will fly at the same speed as the aircraftitself.

V w

V 1V 2 M ergin g P o in t

C asper ghosting a lgo rithm options

G G

V 2 V 2 + V w

M ethod 1 M eth od 2

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In the time-to-go algorithm, the flying-time to themerging point is the same for the aircraft, as it is foran aircraft flying at the location of the ghost plot. Theghost plot will fly at a speed the aircraft would fly ifit would be using this route.

The main difference between the two methods is howthe effect of wind is taken into account. For instance:an aircraft is flying at a speed of V2, at an distance tomerging point d[nm], and facing a headwind of Vwkts. Using the distance-to-go algorithm, its ghost plotwould fly at a speed of V2 kts at a distance d fromthe merging point. Using the time-to-go algorithm,the ghost would be flying at a speed of V2 + Vw at adistance d+x, where x is the additional distancecovered due to the higher speed (figure 9).

Other functionalities that were added to assistthe approach (APP) controllers in their tasks were:

− Introduction of STCA in the TMA

− 10 NM tick marks before the merging point andother small adaptations to the radar display.

− Monitoring functionality that warns thecontroller by deviations from the expected lateraland vertical profile.

For the pilot point of view two importanttools were introduced on the navigation display: avertical view and a flap/gear deployment cue on theND.

8.3 Results of the real-time flight simulationThe general aim of the real-time simulation for

the airborne side was:− To present pilots with the new noise abatement

procedures (NAPs) and pilot tools,− To investigate flyability of the proposed NAPs,− To investigate the usability and acceptance of the

proposed pilot tools, and− To assess the impact of the proposed NAPs and

pilot tools on noise, perceived safety, andefficiency as well as the impact on pilotworkload and situational awareness.

Five crews of each two airline pilots participated inthe experiment and conducted several experimentalruns. In these runs, three NAPs (procedure I, II andV, see section 5) were flown under differentexperimental conditions (for example, with differentwind conditions, with and without the use of pilottools, etc.). Subjective data were collected by meansof questionnaires. The participants completed a post-run questionnaire after each experimental run, which

asked for the participants’ experiences during thatspecific run.

A debriefing questionnaire after the experiment askedfor participants’ overall opinion on the procedures,the tools used, and the experiment.

Pilots were asked, by means of a rating scale, to ratethe flight efficiency, noise friendliness and safety. Itshould be noted that these are subjective ratings andshould be seen as expert judgement feedback of theexperiment and not as objective results.

Figure 10: ND with flap/gear deployment cues andvertical view

EfficiencyEfficiency ratings by the participants (see figure 11)showed that procedure I (baseline) was rated lessefficient than procedure II (p <.005 for the post-run,this was a tendency of p<.10 for the debriefing) andalso rated less efficient than procedure V (p < .01 forthe post-run, and a tendency of p < .10 for thedebriefing). Altogether, that the proposed noise-

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abatement procedures II and V are rated to be moreefficient than the current approach procedure.

Figure 11: Efficiency ratings for NAPs

Perceived safetySafety ratings were made by the participants andpresented in figure 12.

Figure 12: Safety ratings for NAPs

Ratings from the debriefing questionnaire showedtendency that procedure I is rated safer thanprocedure V (p< .10) and a significant effect that II israted safer than procedure V (p < .05). Procedure V israted less safe because of the smaller room for error.

Additional findingsIn addition to efficiency and perceived safety, alsosome pilot-related measurements were performed.First, workload measurements (measured by NASA-TLX and RSME) were performed. Thesemeasurements showed no significant differences inworkload ratings for procedures I, II, and V.

Secondly regarding the Sourdine-II specific tools onthe flight deck it was found that the configuration

change points are clear and that these are evaluated asvery helpful for the pilots. This is especially true forthe initial points CD (CDA initiation point) and 1(flaps 1) and 2 (flaps 2) and the GS point (glide slopeintercept) to enhance situation awareness and managetheir energy level. The latter points, 3 (flaps 3) andFULL (full flaps), etc. were considered as currentpractice and therefore less beneficial. The verticalnavigation display in the lay-out as presented infigure 10 is useful, but it is not required. If moreinformation could be included in the vertical displayit will be much more attractive to use according to theparticipating pilots. This additional information couldbe:− Extra information about (speed) constraints− Vertical speed− Vertical trend of aircraft− TCAS warning− Significant weather information

And finally, situational awareness – especially theaspects “navigational awareness” and “energyawareness” – was investigated. The ratings for bothaspects of awareness show to be always between highand very high.

8.4 Results of the real-time ATC simulationThe general aim of the real-time simulation for

the ground side was:− To present controllers with the new noise

abatement procedures (NAPs) and controllertools,

− To investigate the feasibility and acceptance ofthe proposed NAPs,

− To investigate the usability and acceptance of theproposed controller tools, and

− To assess the impact of the proposed NAPs andcontroller tools on noise, perceived safety,capacity, airline costs as well as on controllerworkload and situational awareness.

Two trials with duration of two days have beenexecuted at this moment. At least one and probablytwo more trails are foreseen before the end of theproject. During the trials two controller roles in theSchiphol TMA (figure 4) were realised:• The Feeder/Departure Controller (FDR/DCO)

for the TMA West, and• The Arrival Controller (ARR).

Like the flight trials, subjective data was collected bymeans of questionnaires. The participants completeda post-run questionnaire after each two runs of aspecific procedure, which asked for the controllers’experiences during that procedure acting both as a

This procedure is efficient

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Procedure I Procedure II Procedure V

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FDR/DCO and an ARR controller. A general debriefwas held at the end of the two-day experiment.

Perceived safetyIn general, participants considered the impressionthat Sourdine-II procedures are safe. This holdsespecially for procedure II and II-A. Mostimportantly, the use of fixed lateral routes wasexperienced as safer than radar vectoring.

In my opinion, the level of safety was high throughout thecompletely disagree (1) ... completely agree (6)

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I II II-A V

ARRIVAL

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Figure 13: Safety ratings by controllers

The only procedure that was assessed less safe thanthe baseline procedure was procedure V. Here,participants indicated that they ‘did not experiencethe situation as fully under control’, and that theseparation on final approach was in some cases lessthan 3 NM.

WorkloadControllers reported that there was less R/T load inthe Sourdine-II procedures than in the baselineprocedure (figure 14 and 15, in these figures “PP”indicates the corresponding pseudo-pilot R/T load).R/T is often taken as an indicator of task load (i.e.,the objective task demands), which would indicatethat the task demands were less with the Sourdine-IIprocedure than the baseline procedure.However, participants also indicated that there was ashift from active control tasks (such as issuinginstructions) to monitoring tasks. This was especiallytrue for procedures II-A and V, and for the role of theARR.These monitoring tasks, although not accompaniedby other behaviour such as R/T, were oftenexperienced as demanding and stressful. One reasonis that if the ARR controller actively builds thesequence (by turning the aircraft at a specific time onfinal approach, by issuing a speed instruction, etc), heor she can predict the resulting position of an aircraft,and only needs to watch the aircraft as part of the

standard monitoring process.

Percentage of time spent on R/T

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Figure 14: Time spent on R/T

With procedures II and V, in which the developmentof the traffic situation bears more uncertainty, themonitoring process becomes more intense (i.e., thecontroller spends more time observing the aircraft).

Number of R/T calls per hour

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Figure 15: R/T calls per hour

For the role of the FDR/DCO, participants stated thatin all of the three Sourdine-II procedures (II, II-A andV) the FDR plays a more central role in building ofthe sequence.

I experienced my workload during the simulation asvery low (1) ... very high (6)

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Figure 16: Workload ratings

The reason is that the instruments for building thesequence (i.e. short-cuts and extensions of the lateralroute) are available to the FDR/DCO, but not to theARR.

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Thus, there is a shift from ARR tasks to theFDR/DCO. In line with this, the rated level ofworkload (measured on the basis of the post-runquestionnaire) shows a numerical decrease for therole of the ARR and a numerical increase for theFDR/DCO.However, the Sourdine-II procedures do not justimply a shift in task components from one controllerrole to the other. Rather, some task componentschange. These task components, for instance, refer toradar vectoring of aircraft or to the issuing of altitudeinstructions that is used for building the sequence /merging inbound streams in current procedures.

Controller tools

GhostingGhosting was experienced as very helpful. Itfacilitates the merging of inbound streams fromRIVER and SUGOL, which is done by theFDR/DCO. Some of the participants considered itwould be advantageous to display the ghost plot onthe basis of time rather than distance (as it iscurrently done). If ghosting was based on time, theinformation could also be provided to ACC. Theadvantage of displaying ghost plots based on distanceis the easy correlation between the actual plot and theghost plot.

Monitoring AidsParticipants appreciated the general idea of providingmonitoring aids to the controller. Nevertheless, theywere not fully satisfied with the chosenimplementation. It was indicated that if the ARR andFDR/DCO’s tasks primarily consist in monitoring,then there would be a broader set of monitoringalerts. For instance, controllers could be warned incase of insufficient separation between a heavy andthe subsequent aircraft.

Conclusions on real-time ATC simulationsProcedure II is seen as an efficient and noise-

friendly approach. Pilots indicated that procedure IIcould have been made steeper than the 2 degreesdescent path. Noisewise it was rated as improvedcompared to the baseline. It was regarded havingmore margins for error (energy corrections) thanprocedure V and therefore safer.

According to the controllers both procedure IIand II-A could be used in real operation, given thatthe following requirements are met:− Pilots need to strictly follow the procedure

− ATCos need to accept the procedure: they needto understand why it is important to apply theprocedure (because it yields a substantialreduction in noise)

− Very good planning of flights: Aircraft need toenter the TMA at a specific time and altitude.

− Controllers should be able to overrule the speedconstraints in the procedure (II-A). This ofcourse should still be within the performanceenvelope of the aircraft flying a continuousdescent procedure.

Procedure V is seen as very noise friendly andfuel efficient, but there is not much room for error forthe pilots. There is an increased risk of being too highand/or too fast in order to perform a stabilisedapproach.

The controllers experienced procedure V as adrastic change from current working procedure: “thisprocedure is really taking it to the extremes”.Nevertheless it was stated that some of the feltuncertainty involved in the procedure might decreasewith practice: “the different speeds are a question ofgetting used to: after a while you know how fastaircraft are flying.”

As mentioned in the results the developedcontroller tools (ghosting and monitoringfunctionality) and pilot flap/gear deployment cue andvertical navigation display were well appreciated.Though the functionality of the monitoring tools andthe vertical navigation display should be furtherextended to optimally support the users in their tasks.

9. ConclusionsPotentially, noise abatement procedures can

contribute to a large noise reduction around airports.However, implementation is only possible when thenew procedures satisfy the requirements with respectto safety, capacity, emissions, cost/benefit andacceptance by the pilot and the air traffic controller.In this paper, results of a part of the Sourdine-IIsafety study and user-acceptance study have beenpresented.

From the safety study, it could not be ruled outthat the risk was worse than the initial target for threeconflict scenarios. For these conflict scenarios safetybottlenecks were identified, which can helpoperational concept developers to find improvementsfor the operation.

The results of the study on user acceptance ofthe Sourdine-II procedures is presented in section 8.Both from a pilot viewpoint as well as from the air

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traffic controllers’ viewpoint, there are somebottlenecks identified. It was identified thatintroduction of the procedures could be facilitated by:• For the pilot:

• The ND should display the CDA initiationpoint and configuration change points

• For the air traffic controller:• provide early sequencing of the aircraft• provide extended monitoring tool (speed

deviations and required wake vortexseparation) for APP, or even replace byASAS Spacing functionality on baseleg andfinal.

For airports which use two parallel runways forarriving aircraft, a continuous descent of two aircraftcould cause a violation of the separation minima(1000ft/3nm). Additional research is required toinvestigate further technical or a procedural solutions(e.g., flying curved approaches using GPS or MLS)to use continuous descent approaches on parallelrunways.

For more information: see www.sourdine.org

10. References[1] Sourdine-II D3-1-1, Definition of New Noise

Abatement Procedures, v1.0, 10/03/2002,INECO

[2] Sourdine-II, D5-3, Single event noisecalculations, v1.0, 23/06/2003, Airbus-France

[3] Sourdine-II D3-1-2, Definition of New NoiseAbatement Procedures, update report, v2.5,02/04/2004, INECO

[4] Change in Airport Noise and Emissions due toNoise Abatement Procedures, R.G. den Boer,Aircraft Noise and Emissions ReductionSymposium, may 2005

[5] FAA/Eurocontrol Safety Action Plan 15, ATMsafety techniques and toolbox, Final version forcomments, December 2004 (final versionavailable at ATM2005)

[6] H.A.P. Blom, G.J. Bakker, P.J.G. Blanker, J.Daams, M.H.C. Everdij and M.B. Klompstra,Accident risk assessment for advanced air trafficmanagement, Eds: G. Donohue and A.Zellweger, Air transportation systemsengineering, AIAA, 2001, pp. 463-480

[7] H.H. de Jong, Guidelines for the identification ofhazards, How to make unimaginable hazardsimaginable, NLR-CR-2004-094, March 2004.

Also released as EUROCONTROL EATMP SAM,Guidance Material B2:http://www.eurocontrol.int/safety/downloads/sam/Level2/FHA V2.0/FHA V2-0 Chapter 3Guidance B2.doc.

[8] M.H.C. Everdij, and H.A.P. Blom, Bias anduncertainty in accident risk assessment, NLR-TR-2002-137, 2002.

11. AbbreviationsA/P Airport

APP Approach

ARR Arrival

CBA Cost Benefit Analysis

CWP Controller Working Position

DCO Departure Controller

FDR Feeder

FPA Flight Path Angle

GRACE Generic Research Aircraft CockpitEnvironment

GS Glide Slope

HMI Human Machine Interface

IAF Initial Approach Fix

INM Integrated Noise Model

NAP Noise Abatement Procedure

NARSIM NLR ATM Research SIMulator

ND Navigation Display

NPD Noise Power Distance

OEI One Engine Inoperative

RSME Rating Scale Mental Effort

R/T Radio/Telephony

RTD Reasearch Technology and Demonstration

RTS Real-Time Simulation

SES Single Event Simulation

Sourdine Study of optimisation procedures for decreasing the impact of noise

STCA Short Term Conflict Alert

TLX Task Load Index

TMA Terminal Manoeuvering Area

12

TOPAZ Traffic Organization and

Perturbation AnalyZer

12. Authors’ biographiesRuud den Boer received his M.Sc. in AerospaceEngineering at the TU Delft in 1981. From 1981 to1996 he worked at the Aero-elasticity department ofNLR. He was the leader of several projects executedby NLR for General Dynamics/Lockheed and washeading the experimental unsteady aerodynamicsgroup. In 1996 he joined the ATM department atNLR, he headed the ATM – real-time simulationsgroup (NARSIM) from 1999-2002 and currently he isthe co-ordinator of the Sourdine-II consortium.

Collin Beers received his M.Sc. in AerospaceEngineering at the TU Delft in 1998. Since then he isworking as an aerospace engineer at the ATMdepartment of the National Aerospace Laboratory(NLR) the Netherlands. He was previously involvedin MTCD related projects such as the MTCD shadowmode trials at Malmö and Rome ATCC and theevaluation of MTCD at Riga ACC contracted byEurocontrol. Currently he is involved in theSourdine-II project and Dutch government projects.These latter projects are focusing on airspace

capacity and the development of concept ofoperations for the future.

Hans Huisman started working for the NLR in 1991in the avionics group. After specialising in userinterface aspects of flight deck design a.o. for Fokkeraircraft and european projects and gaining experiencein running human in the loop experiments with theflight simulators of the NLR he moved to the Humanfactors department in 1993. Currently he is seniorR&D manager within the Training, Human Factors

Mariska Roerdink has a degree in cognitivepsychology and specialised in Human factors. Shestarted working for the NLR in 2002 in the Humanfactors department. Currently she is R&D engineerwithin the Training, Human Factors and CockpitOperations department. She has been involved inpreparing and running human in the loopexperiments, for example Sourdine-II.

Jelmer Scholte has worked as R&D engineer in airtransport safety at NLR since 2000. He received hisM.Sc. degree in Applied Mathematics from TwenteUniversity. His current research interests includesafety risk asessment and safety risk criteria. He hasperformed many qualitative and quantitative safetyrisk assessments for various customers.