muac en route delay absorption capabilities for schiphol

MUAC En Route Delay AbsorptionCapabilities for Schiphol Inbounds

L. M. C. Adriaens

August 9, 2015

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MUAC En Route Delay AbsorptionCapabilities for Schiphol Inbounds

Master of Science Thesis

For obtaining the degree of Master of Science in Aerospace Engineering

at Delft University of Technology

L. M. C. Adriaens

August 9, 2015

Faculty of Aerospace Engineering · Delft University of Technology

Delft University of Technology

Copyright c© L. M. C. AdriaensAll rights reserved.

Delft University Of Technology

Department Of

Control and Operations

The undersigned hereby certify that they have read and recommend to the Faculty ofAerospace Engineering for acceptance a thesis entitled “MUAC En Route Delay Absorp-tion Capabilities for Schiphol Inbounds” by L. M. C. Adriaens in partial fulfillmentof the requirements for the degree of Master of Science.

Dated: August 9, 2015

Readers:prof.dr.ir. J. M. Hoekstra

dr.ir. J. Ellerbroek

ir. E. Westerveld

ir. S. Hartjes

Uiteindelijk lukt het altijd.

- Papa

vi

L. M. C. Adriaens MUAC En Route Delay Absorption Capabilities for Schiphol Inbounds

Acronyms

ACC Area Control CentreAMAN Arrival ManagementANSP Air Navigation Service ProviderAP Arrival PlannerAPP Terminal Manoeuvring Area controlASAS Airborne Separation Assurance SystemATC Air Traffic ControlATCo Air Traffic ControllerATS Air Traffic ServicesBADA Base of Aircraft DataCAPAN ATC Capacity Analyser toolCTA Control AreaCTR Control ZoneDDR2 Demand Data Repository 2DFS Deutsche Flugsicherung (German ANSP)DMAN Departure ManagementDSNA Direction des Services de la Navigation Aerienne (French ANSP)EAT Expected Approach TimeEC European CommissionEHAM Amsterdam Schiphol AirportENMAN En Route ManagementFABEC Functional Airspace Block Europe CentralFABs Functional Airspace BlocksFIR Flight Information RegionFL Flight LevelFMS Flight Management SystemFUA Flexible Use of Airspace

MUAC En Route Delay Absorption Capabilities for Schiphol Inbounds L. M. C. Adriaens

GRM Graphical Route ModificationsIAF Initial Approach FixIATA International Air Transport AssociationLCC Low Cost CarrierLNAV Lateral NavigationLoA Letter of AgreementLRC Long Range Cruise SpeedLVNL Air Traffic Control The NetherlandsMRC Maximum Range Cruise SpeedMUAC Maastricht Upper Area Control CentreNATS National Air Traffic Services (British ANSP)NEST Network Strategic ToolNLR Dutch National Aerospace LaboratoryNM Nautical MilePCP Pilot Common ProjectSAAM System for traffic Assignment and Analysis at a Macroscopic levelSEC Senior Executive ControlSESAR Single European Sky ATM ResearchTAS True AirspeedTCA Terminal Control AreaTMA Terminal Manoeuvring AreaTOD Top of DescentTWR Tower ControlUIR Upper Information RegionVNAV Vertical NavigationXMAN Cross Border Arrival Management

Contents

Acronyms vii

List of Figures xiii

List of Tables xv

Acknowledgements xvii

Summary xix

1 Introduction 1

2 Background Information 3

2-1 Airspace Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2-1-1 Lower Airspace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2-1-2 Upper Airspace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2-1-3 Adjacent Airspace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2-2 Schiphol Inbound Routes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2-3 Arrival Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2-3-1 Current Arrival Management Procedure . . . . . . . . . . . . . . . . . . 11

2-3-2 Future Arrival Management Procedure . . . . . . . . . . . . . . . . . . . 12

2-4 Current Delay Absorption & Sequencing Measures . . . . . . . . . . . . . . . . . 13

2-5 Definition of Delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2-6 Influential Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2-7 Delay Absorption Tactics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15


x Contents

3 Research Design 17

3-1 Research Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3-2 Research Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3-3 Independent Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3-4 Dependent Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4 Simulation Design 23

4-1 BlueSky Open ATM Simulator . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4-1-1 Lateral Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

4-1-2 Vertical Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4-1-3 Airborne Separation Assurance System . . . . . . . . . . . . . . . . . . . 25

4-2 Simulation Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264-3 Required Additions to BlueSky . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

5 Simulation Details 295-1 Planning Conflict Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

5-2 .so6 to .scn Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305-3 Delay Tactics Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

5-3-1 Linear Holding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

5-3-2 Dropping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

5-3-3 Detouring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

5-3-4 Turtling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5-4 Fuel Consumption Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5-5 Workload Estimation Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

6 Simulation Scenarios 436-1 Eurocontrol DDR2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436-2 Data Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

7 Results 477-1 Maximum Delay Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

7-2 Fuel Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

7-2-1 Linear Holding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

7-2-2 Dropping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

7-2-3 Detouring & Turtling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

7-3 Conflicts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527-4 Communication Workload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

7-4-1 Linear Holding & Dropping . . . . . . . . . . . . . . . . . . . . . . . . . 53

7-4-2 Detouring & Turtling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

7-4-3 Communication Workload Forecasting . . . . . . . . . . . . . . . . . . . 56

7-5 Sensitivity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

7-5-1 Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587-5-2 Airline Intent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597-5-3 Route . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597-5-4 Weather . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 607-5-5 Military Airspace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61


Contents xi

8 Discussion 63

9 Conclusions 69

10 Recommendations 71

A .So6 to .scn Conversion 73

B BlueSky Commands 77

C Workload 79

D Conflicts 89

Bibliography 91


xii Contents


List of Figures

2-1 A schematic breakdown of the Amsterdam FIR [Dr. ir. C. Borst and Prof. dr. ir.M. Mulder, 2013] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2-2 Route map of Schiphol arrivals [AIS, 2012] . . . . . . . . . . . . . . . . . . . . . 5

2-3 Overview of the MUAC airspace [Eurocontrol, 2014b] . . . . . . . . . . . . . . . 7

2-4 Brussels routes 1, 2 and 3 [Skyvector, 2015] . . . . . . . . . . . . . . . . . . . . 9

2-5 Brussels routes 4 and 5 [Skyvector, 2015] . . . . . . . . . . . . . . . . . . . . . 10

2-6 Hannover routes 1 through 6 [Skyvector, 2015] . . . . . . . . . . . . . . . . . . 10

2-7 Jever routes 1 through 7 [Skyvector, 2015] . . . . . . . . . . . . . . . . . . . . . 11

4-1 Screenshot of the BlueSky Open ATM Simulator . . . . . . . . . . . . . . . . . 24

5-1 Simulation structure of the conflict detection code . . . . . . . . . . . . . . . . . 30

5-2 Schematic representation of dropping . . . . . . . . . . . . . . . . . . . . . . . . 33

5-3 Plot of inbound EHAM traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

5-4 Maximum range cruise speed vs. altitude [Eurocontrol, 2013] . . . . . . . . . . . 34

5-5 Plot of inbound and outbound EHAM traffic [Eurocontrol, 2014a] . . . . . . . . 35

5-6 Map of Jever sectors with detour routes marked in blue [Skyvector, 2015] . . . . 36

5-7 MUAC SEC input per 100 flights per weekday [R. Ehrmanntraut and I. Sitova, 2013] 39

6-1 Distribution of 2013 EHAM inbounds per hour of day [Schiphol Amsterdam Airport,2014] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

6-2 Distribution of EHAM arrivals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

6-3 Average FIR delay per inbound EHAM flight [NLR, 2013] . . . . . . . . . . . . . 46

6-4 Distribution of EHAM FIR Delay . . . . . . . . . . . . . . . . . . . . . . . . . . 46

7-1 Comparison of fuel consumption at various speeds and altitudes . . . . . . . . . 50


xiv List of Figures

7-2 Comparison of fuel flow during normal scenario, linear holding and dropping . . . 51

7-3 Communications workload - Brussels sectors - February . . . . . . . . . . . . . . 54

7-4 Relative change in communications workload - Brussels sectors - February . . . . 54

7-5 Maximum range cruise speed at FL380 vs. Reference mass factor . . . . . . . . 59

7-6 Linear holding maximum delay absorption per NM vs distance . . . . . . . . . . 60

7-7 Dropping maximum delay absorption per NM vs distance . . . . . . . . . . . . . 61

A-1 Flowchart explaining the process of converting the .so6 data to .scn . . . . . . . 75

C-1 Communications workload - Jever sectors - February . . . . . . . . . . . . . . . 80

C-2 Relative change in communications workload - Jever sectors - February . . . . . 80

C-3 Communications workload - Jever sectors - Detouring/turtling - February . . . . 81

C-4 Relative change in communications workload - Detouring/turtling - Jever sectors- February . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

C-5 Communications workload - Brussels sectors - February . . . . . . . . . . . . . . 82

C-6 Relative change in communications workload - Brussels sectors - February . . . . 82

C-7 Communications workload - Hannover sectors - February . . . . . . . . . . . . . 83

C-8 Relative change in communications workload - Hannover sectors - February . . . 83

C-9 Communications workload - Jever sectors - August . . . . . . . . . . . . . . . . 84

C-10 Relative change in communications workload - Jever sectors - August . . . . . . 84

C-11 Communications workload - Jever sectors - Detouring/turtling - August . . . . . 85

C-12 Relative change in communications workload - Jever sectors - Detouring/turtling- August . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

C-13 Communications workload - Brussels sectors - August . . . . . . . . . . . . . . . 86

C-14 Relative change in communications workload - Brussels sectors - August . . . . . 86

C-15 Communications workload - Hannover sectors - August . . . . . . . . . . . . . . 87

C-16 Relative change in communications workload - Hannover sectors - August . . . . 87

D-1 Total number of conflicts within MUAC airspace - February . . . . . . . . . . . . 90

D-2 Total number of conflicts within MUAC airspace - August . . . . . . . . . . . . 90


List of Tables

2-1 Schiphol inbound routes through MUAC airspace . . . . . . . . . . . . . . . . . 8

2-2 Delay absorption tactics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3-1 Research project stakeholders . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5-1 Inbound peaks at Schiphol Airport [Eurocontrol Experimental Centre, 2003] . . . 30

5-2 Interpretation of hourly workload using CAPAN [Eurocontrol Experimental Centre,2003] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

5-3 Communication workload in seconds per command [R. Ehrmanntraut and I. Sitova,2013] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

5-4 Rules to establish communication workload within MUAC airspace . . . . . . . . 41

5-5 Additional rules to establish workload within MUAC airspace resulting from enroute delay absorption measures . . . . . . . . . . . . . . . . . . . . . . . . . . 41

7-1 Optimum delay absorption within MUAC airspace . . . . . . . . . . . . . . . . . 48

7-2 Average fuel flow during different delay absorption tactics . . . . . . . . . . . . . 49

7-3 Total conflicts within MUAC airspace . . . . . . . . . . . . . . . . . . . . . . . 52

7-4 Average communication workload per sector [seconds per hour] . . . . . . . . . . 53

7-5 Pearson correlation between expected and actual change in workload . . . . . . . 57

7-6 Spearman correlation between expected and actual change in workload . . . . . . 57

7-7 Pearson correlation between workload change and average hourly traffic density . 58

7-8 Spearman correlation between workload change and average hourly traffic density 58

8-1 Fuel efficiency compared to lower airspace holding . . . . . . . . . . . . . . . . . 64

A-1 .so6 data format [DDR2 Developers, 2014] . . . . . . . . . . . . . . . . . . . . . 73

B-1 Fully referenced from the BlueSky Open ATM Simulator Command Reference . . 78


xvi List of Tables


Acknowledgements

Het afgelopen jaar is op meerdere manieren een studie geweest naar het absorberen vanvertraging, en daarom wil ik graag een aantal mensen bedanken voor hun steun en hulp.

Allereerst: Evert Westerveld voor het bedenken en het mij gunnen van deze opdracht.Gedurende het gehele project heeft hij me inhoudelijk geholpen door me met zijn eigen kennisen netwerk te vertrouwen, maar misschien nog wel belangrijker: ondanks alle tegenslag vanhet afgelopen jaar heeft hij altijd vertrouwen gehouden in mij en een goede afloop van ditproject. Daar ben ik hem ongelooflijk dankbaar voor.

Naast Evert wil ik graag Ilona Sitova (MUAC), Jacco Hoekstra en Joost Ellerbroek (beidenTU Delft) bedanken voor hun inhoudelijke hulp. Zonder hun discussies, feedback, gezamen-lijke debugsessies en suggesties had dit verslag er niet gelegen. Daarnaast gaat ook grote dankuit naar Viktor Jagasits (Luchtverkeersleider bij MUAC) voor de tijd die hij vrij heeft gemaaktom me mee te laten lopen tijdens zijn werk en voor zijn onvermoeibare bereidheid mijn vragente beantwoorden. Tot slot ben ik Isabel Metz zeer erkentelijk voor haar fantastische werk aande implementatie van performance modellen in BlueSky. Dankjulliewel!

Dit hele project was een stuk zwaarder geweest als ik niet met zo’n leuke groep mensen inSIM008 had mogen zitten. Ik koester erg warme herinneringen aan mijn tijd in het hok enaan de mensen met wie ik er zo veel tijd heb doorgebracht. Hopelijk zullen er ook na mijnafstuderen nog veel schaakpartijen en borrels volgen.

Echter, de grootste uitdaging van het afgelopen jaar is niet het afstuderen zelf geweest, maarhet (in alle opzichten) gezond blijven. Ik voel me gezegend met een aantal fantastischevrienden die altijd voor me klaarstaan, in het bijzonder Naad, Bing, Joost, Jasper, Matthijs,Tim en Ezra: ik weet niet hoe ik er zonder jullie doorheen was gekomen.

Maar boven alles en iedereen staan natuurlijk mijn ouders en broer. Ik kan niet uitdrukkenhoe belangrijk jullie voor me zijn. Dankjulliewel voor alles wat jullie voor me doen en gedaanhebben.

Tot slot zou ik dit werk graag willen opdragen aan Jelmer Breur en Marianne Bolster, zonderhen was ik niet geweest wie en waar ik nu ben.


xviii Acknowledgements


Summary

Over the duration of the last year research regarding the en route delay absorption capabilitiesof the MUAC airspace for Schiphol inbound flights has been performed. Delay absorptioncurrently takes place in the lower airspace, where as a result air traffic controllers and pilotsexperience increased workloads during one of the most critical periods of a flight. This incombination with the expected fuel inefficiency of delay absorption in the lower airspaceresulted in this research to investigate the options of moving delay absorption away from thelower airspace, into the en route airspace.

The MUAC airspace is all airspace above FL245 over The Netherlands, Belgium, Luxembourgand West-Germany, encompassing Schiphol inbound flights entering the LVNL airspace (allairspace over The Netherlands up to FL245) from the South, East and North. Traffic datafrom two sample days was selected (one in high season and one in low season) to reflect thedifferent traffic patterns occuring throughout the year, based on which the planning conflictswere determined. From these planning conflicts the amount of required delay absorption hasbeen obtained, and used as an input to determine which way of en route delay absorptionshould be used.

A range of delay absorption measures has been defined and evaluated: linear holding anddropping for all routes, and detouring and turtling for selected Northern routes. Linearholding means only slowing an aircraft down to the Maximum Range Cruise speed at most,and dropping represents both slowing an aircraft down while lowering its altitude by 2000 ftacross its trajectory within the MUAC airspace. Detouring and turtling are the equivalentof linear holding and dropping, respectively, however executed on an extended trajectory.Changing the trajectory of an aircraft may result in conflicts with other traffic, hence it wasdecided only to use these measures for the Northern routes. This part of the MUAC airspacehas a lower traffic density in general, and was the only airspace that could reasonably beprovided with detours.

The changes were implemented in the scenarios, which were run in the BlueSky Open SourceATM Simulator to gather data on fuel consumption (using Eurocontrol’s Base of AircraftData), air traffic controller communications workload, and the number of conflicts with othertraffic. The data obtained from the delayed scenarios has been compared to the originalscenario to see how the variables were affected by the delay absorption.

The delay absorption within the MUAC airspace was found to be 0.4 s/NM for linear hold-ing and 0.7 s/NM for dropping. For the three routes through the Jever sector that were


xx Summary

found eligible for detouring and turtling, an additional 8 seconds should be counted for eachadditionally flown nautical mile.

Fuel consumption has been compared to the fuel consumption in the original scenario, fromwhich a slightly reduced fuel consumption was found for linear holding (-0.1%), but a signifi-cantly lower fuel consumption for dropping and turtling (-45% and -50%, respectively). Thisstrong reduction in fuel consumption is caused by the earlier initiated descent, during whichthe aircraft can throttle back to idle thrust. Detouring was found unfavourable in termsof fuel (due to the additional path length), but is nevertheless an effective means of delayabsorption.

The communication workload was generally found to strongly increase during MUAC peakloadings. Adding more work when a controller is already at his/her busiest is not very desir-able, which is why it is unlikely that delay absorption during peak loading can be implementedin the way it was simulated. However, off-peak workloads were sometimes found to be evenlower than in the original scenario. This can be explained by the reduction of the number ofconflicts, due to which some of the workload assigned for resolving conflicts could be elimi-nated. During these times of day en route delay absorption would be more than just feasible;it would be very desirable. The ability to predict the change in communication workloadhas been assessed by computing the correlation between expected and actual change in com-munication workload, as well as between traffic density and actual change in communicationworkload, but no relation was found to be strong enough to give a representative indicationof the actual change in workload.

Overall, the total number of conflicts during linear holding and dropping runs for the lowseason day were found to lower by 1.1% and 0.4% respectively. The high season saw anoverall increase of 0.7% of the total number of conflicts. It is thus expected to be favourablefor other traffic if en route delay absorption is performed during low season days, but mostlyunfavourable during high season. The Jever sector was the only sector to be equipped withdetouring and turtling options, and during all scenarios except for the August linear holdingand dropping scenarios a reduction of the total number of conflicts was observed.

It can be concluded that when care is taken in when and how en route delay absorption isimplemented, it most definitely shows potential to (partially) replace delay methods in thelower airspace.


Chapter 1

Introduction

When driving a car, you will often find yourself optimising the trajectory of your car usinginformation on the current and near future traffic situation: maybe there is a blocked junctionahead, perhaps there is a shortcut, or maybe the traffic news on the radio informs you thatthere is a traffic jam right near your destination.

Imagine the latter of the examples, where in addition you have reliable information about theduration of this traffic jam. Would you rather rush to the congested area, only to be drivingat a foot pace once you get there, or would you try to avoid the jam by holding back on yourgas and giving the jam some time to dissolve? This last option would be a clear winner: youprobably save on gas and the annoyance of being in a traffic jam, and you are likely to get toyour destination around the same time as planned.

Leaving the obvious differences between the performance of a car and an aircraft aside, thisoptimisation process has some interesting similarities with trajectory optimisation takingplace in the air. In current air traffic operations it often happens that air traffic arrives atan airport in bunches, resulting in traffic jams in the airspace around the destination airport.Pilots get information and support from air traffic control, together with whom they willpursue an optimal flight profile.

When air traffic control of a certain part of airspace is too busy to receive and handle ad-ditional traffic it will assign a delay to incoming flights: a flight is given a certain time atwhich it is allowed to enter the airspace. The delayed aircraft must now work together withair traffic control to take care of getting to this point at the designated time. Taking mea-sures to delay an aircraft to meet this new time is called delay absorption. There are severalways in which this delay absorption can take place; think of speed reductions and flight pathextensions.

In the current operations it is known relatively shortly before landing (approximately 14minutes) whether the airspace around the destination airport is congested, and if there is aneed to absorb delay. Despite this ‘short notice’, delays can still build up to four minutes forSchiphol airport during inbound peaks due to the bunches that occur in the arriving trafficpattern. [NLR, 2013] Absorbing this delay on a nominal remaining flight duration of only


2 Introduction

14 minutes is a complex task for the air traffic controller, who aims to turn the bunches ofincoming traffic into an efficient traffic sequence. This is complicated by various factors suchas the aircraft’s performance characteristics, the presence of other traffic, the airspace design,strict environmental regulations concerning noise and emissions, the airlines’ desire to avoidpath extensions, and air traffic controller workload. These factors make the optimisation ofa flight profile of an arriving aircraft can be regarded as more complex than the optimisationof your car’s trajectory.

Despite the challenges and complexities of the topic, Air Traffic Control The Netherlands(LVNL) and the Dutch National Aerospace Laboratory (NLR) saw opportunity in improvingthe arrival management process at Schiphol Airport. To put their ideas to the test, theydeveloped and ran the AIRE-II trials together. During these trials the estimated time ofarrival at Schiphol Airport was managed already from 60 minutes before landing, enablingcontrollers to anticipate on possible bunches of incoming traffic. The main conclusions werethat improvements to the arrival management process could result in significant fuel savings(and consequently a reduction of the environmental impact of a flight), and smoother oper-ations for the air traffic controllers at LVNL. In a business where many commercial airlinesstruggle to remain profitable, striving for a lower fuel consumption makes sense not only froman environmental, but also from a financial point of view.

The AIRE-II trials showed potential for (en route) delay absorption, but how and how muchdelay can be absorbed remained unclear. A majority of Schiphol inbounds is fed to LVNL’scontrol by the Maastricht Upper Area Control Centre (MUAC). The success of a possiblepermanent solution is in the hands of en-route control centres, like MUAC, for without theirconsent and cooperation it becomes impossible to absorb delays in the cruise phase of a flight.

This thesis was preceded by a preliminary thesis, which explored the general potential ofen route delay absorption. [Lisanne M. C. Adriaens, 2014] During this research, sufficientgrounds were found to continue exploration of this topic with a MSc thesis, of which theresult lies in front of you right now. Where the preliminary thesis was meant to explore andmap the possibilities of en route delay absorption for Schiphol inbounds, this thesis aims toprovide a quantitative answer to the main research question posed in the preliminary thesis:

How much delay can be absorbed by MUAC for Schiphol airport inbound flights?

To answer this question, first a short recap of the preliminary thesis is given. This consistsof a theoretical part, which can be found in Chapter 2, and the most important parts ofthe research plan, stated in Chapter 3. Readers that are familiar with the material coveredin the preliminary research may prefer to cut right to the chase, and start at Chapter 4.This chapter discusses the basic working principles of the BlueSky Open ATM Simulator(the principal tool used during this research), and what additions are required to have itperform the desired simulations. The details of the required additions to BlueSky will bediscussed in Chapter 5, followed by an explanation of the scenarios that have been selected,in Chapter 6. Finally, after all this background information, it is time for the results whichare presented in Chapter 7 and more elaborately discussed in Chapter 8. The conclusionsresulting from this research are drawn in Chapter 9. Chapter 10 concludes this report, withsome recommendations on how to move forward with this topic of research.


Chapter 2

Background Information

During the preliminary phase of the research the initial information required to set up a modelwas explored. The findings of this research has been reported in a preliminary thesis. However,to get the reader of this thesis up to speed on the subject of en route delay absorption,an overview of the necessary knowledge for the remainder of this thesis. For a more indepth review of the topics discussed in this chapter, the associated preliminary thesis can beconsidered.

2-1 Airspace Structure

Air Traffic Control (ATC) can be divided into five different control tasks, which rely on thestructure of the airspace. These parts of airspace are shown schematically in Figure 2-1(excluding the military airspace).

Figure 2-1: A schematic breakdown of the Amsterdam FIR [Dr. ir. C. Borst and Prof. dr. ir.M. Mulder, 2013]

The first distinction that can be made based on Figure 2-1 is between the lower and the upperairspace at FL 245. These two parts of Dutch airspace have different types of ATC providedby different organisations. Let’s evaluate both separately.


4 Background Information

2-1-1 Lower Airspace

In The Netherlands, Amsterdam Schiphol Airport (International Air Transport Association(IATA): Amsterdam Schiphol Airport (EHAM)) is the busiest airport, which results in anairspace design that is focussed around the routes to and from Schiphol. Consistent withFigure 2-1, the four types of controlled airspace that can be distinguished in the lower airspaceare:

Control Zone (CTR)/Aerodrome The area within a radius of 8 Nautical Mile (NM) of anairport, from 1200 ft up to an altitude of 3000 ft, is called the Control Zone (CTR) or theaerodrome. It is controlled by approach/tower (APP/TWR) controllers in the ATC Towerat the airport, which ensures safe landing and take-off operations. For Schiphol Airport thiscircular area is called CTR1, and has one rectangular extension to the North (CTR2) andone to the South (CTR3). These extensions are based on the orientation of the runways andallow for sufficient time and space to handle in- and outbound flights. For example, withthe Polderbaan being positioned more northerly than the other runways, an extension of theCTR is required to provide Tower Control (TWR) with the necessary time to handle a flight.

Terminal Manoeuvring Area The Terminal Manoeuvring Area (TMA) extends around andabove the CTR from a level of 1000 ft up to 10500 ft, in a more or less circular area aroundSchiphol Airport. This part of the airspace is controlled by Terminal Manoeuvring Areacontrol (APP)/TWR controllers who guide departing and arriving traffic between the ControlArea (CTA) and CTR. The TMA can be entered through one of three entry points, or InitialApproach Fix (IAF): SUGOL, ARTIP and RIVER. Their positions within the AmsterdamFIR can be seen in Figure 2-2. In American literature the TMA is often referred to as theTerminal Control Area (TCA).

Control Area Flights operating in the Amsterdam Flight Information Region (FIR), outsideof the CTR and TMA, but beneath Flight Level (FL) 245 are in the lower airspace. Thisairspace is controlled by Amsterdam Radar, also known as the Area Control Centre (ACC)ATC.

ACC controllers are also responsible for the stacks, designated holding areas right on theborder of the CTA with the TMA that are intended to handle a temporary surplus of arrivingtraffic. These stacks keep the aircraft close to the airport, such that flights can be handledquickly once there is an available landing slot.

Military Airspace The military airspace in The Netherlands consists out of three areas: onein the North over the Wadden Sea, one in the East bordering Germany, and one in the Southbordering Belgium and Germany. These areas are under the control of the Military ATC,despite the containment of airports that are also used for civil aviation such as EindhovenAirport and Maastricht-Beek Airport. The military airspace is subjected to the Flexible Useof Airspace (FUA) principle, where military airspace can be used for civil aviation if notrequired by the military.


2-1

Airsp

ace

Stru

ctu

re5

070°1 min

176°1 min

1 min

294°

1 min

250°

21

226°

39

17

176°

27

288°34

306°13

338°

11

359°

29

15

015°

27

060°

40

077°

21

7

356°

12

308°35

274°

17

171°

39

175°

11

FL200

ATC discretion

IAF

IAF

16

13

309°11

23

120°

101°

18

17

13

121°

114°

SEE INSTRUMENT APPROACH CHARTS

3

MOLIX 2A

TOPPA 2A

LAMSO 1A

REDFA 1A

DENUT 1A

HELEN 1A

PESER 2A

EELDE 1A EELDE 1B

REKKEN 2B

REKKEN 2A

NORKU 2BNORKU 2A

PUTTY 1A

28320°

See EHEH, EHBDand EHBK SIDs

FL 100* FL 070

MAX 250 KT IAS

FL 100* FL 070

MAX 250 KT IAS

IAF

FL 100* FL 070

MAX 250 KTIAS

43

042°

222°

06°

(U)N125

UZ701

(U)N

872

(U)P

999

(U)P

174

UP

603

MAASTRICHTVOR / DME

2000

060°

1 min

ATC

BRUSSELS FIR

AMSTERDAM FIR

AM

STE

RD

AM

FIR

LO

ND

ON

FIR

FIR

AM

STE

RD

AM

BR

EM

EN

AM

ST

ER

DA

MF

IR

FIR

BREMEN FIR

LA

NG

EN

FIR

LANGEN FIR

15 SPL

SCHIPHOL108.400

52°19’56’’N/ CH21X

/ SPL

004°45’00’’E/ ATIS

0

L52°13’14’’N

/ CH- 388.5004°33’27’’E

L52°19’34’’N

/ WP- 376005°01’59’’E

PAMPUS117.800

52°20’05’’N/ CH125X

/ PAM

005°05’32’’E0

L52°09’05’’N

/ NV- 332004°45’53’’E

ROTTERDAM110.400

51°58’25’’N/ CH41X

/ RTM

004°28’51’’E0

STAD51°44’29’’N

/ STD- 386004°14’37’’E

HAAMSTEDE114.150

51°43’22’’N

/ HSD

003°51’29’’E

COSTA110.050

51°20’53’’N/ CH37Y/ COA

003°21’19’’E0

EINDHOVEN(117.200)

51°26’53’’N/ CH119X

/ EHV

005°22’30’’E100

EINDHOVEN51°28’04’’N

/ EHN- 397005°23’42’’E

REKKEN116.800

52°08’00’’N/ CH115X

/ RKN

006°45’50’’E100

EELDE112.400

53°09’50’’N/ CH71X/ EEL

006°40’00’’E0

SPIJKERBOOR113.300

52°32’25’’N/ CH80X

/ SPY

004°51’14’’E0

DEN HELDER115.550

52°54’25’’N/ CH102Y

/ HDR

004°45’57’’E0

TOPPA136.4 NIK 350.8

MOLIX

LAMSO

LUTEX

PEPEL

MONIL

SULUT56.3 HDR 241.3

REDFA90.8 SPY 253.796.1 HDR 240.4

ROBVI41.3 HDR 241.385.9 NIK

SUGOL31.0 SPL 292.4

RIVER34.0 SPL 222.2

DENUT90.1 SPY 209.9

HELEN86.5 SPY 205.3

PUTTY

ROBIS58.5 SPY 093.6

SONSA11.6 RKN 356.1

NORKU34.6 HMM 308.8

OSKUR43.0 SPY 093.434.7 RKN 308.7

NARSO35.0 RKN 356.127.0 EEEL 176.1

NOVEN39.0 EEL 226.5

DEN HELDER115.550

52°54’25’’N/ CH102Y

/ HDR

004°45’57’’E0

36C

06

24

09

27

36R

18L

04

22

18R 18C

L52°28’13’’N

/ OA- 395004°45’12’’E

OLGAX

PEVOS

LANSU

PESER33.3 EHV / HSD 104.3

BEDUMKUBAT

LUGUM

SOMPOTEMLU

DOBAK

SOPVI

OSGOS

32.0 SPL 070.4ARTIP

26.3 SPY 093.9

GND

360FLEHR3-3D

EHFL

D05541E

MSL

41FEHFL

D055

MSL

EHFLD

660

MSL

41A-D

2AEHFL

R195

GND

2°E 3° 4° 5° 6° 7° E

53°N

52°

51°N

1700

354°

311°

2300

MSA BASED ON

SPL VOR/DME

0

0

km 105

2 5 10 20

20 30

SCALE 1 : 1 500 000

NM

40

15

SID ROUTE AS DESCRIBED

ATS ROUTE

DISTANCES IN NM

DIRECTIONS ARE MAGNETIC

ALTITUDES IN FEET

STAR

CDR

Detailed information concerning ATS-routessee ENR 6-3.1

ATIS

ACC 134.375

130.950120.550118.800

AmsterdamRadar

NARSO

RIVER

ArrivalSPL VOR

Information

SUGOLARTIP

HOLDING

121.500 General Emergency

(TAR)

APP

131.150

118.400

119.050

121.200

Schiphol

Schiphol

Arrival

Approach / Departure

TWR

118.100

119.225 Primary

132.975108.400

118.275

Schiphol Tower

ICAO STAR DESIGNATORS AND

CORRESPONDING ARINC 424 CODES

DENUT 1A [DENU1A]

EELDE 1A [EEL1A]

EELDE 1B [EEL1B]HELEN 1A [HELE1A]

LAMSO 1A [LAMS1A]

MOLIX 2A [MOLI2A]NORKU 2A [NORK2A]

NORKU 2B [NORK2B]

PESER 2A [PESE2A]

[REDF1A]

[RKN2A]

[RKN2B]

TOPPA 2A [TOPA2A]

REDFA 1A

REKKEN 2A

REKKEN 2B

[PUTY1A]PUTTY 1A

DME SPY 23.1 NM

VOR SPY RADIAL 304.2

HOLDING PROCEDURES :

Entry Standard ICAO

COMMUNICATION FAILURE :

NOTES :

MAX Holding Speed : 250 KT IAS

SPEED AND LEVEL RESTRICTIONS :

see EHAM AD 2.22.

1.

2.

3. Only the main landing RWYs equipped withan ILS approach procedure are indicatedon this chart.

MNM Holding Level : FL 070(EXC NARSO : FL 200)

Final approach information: consult therelevant instrument approach chart.

Act in accordance with EHAM AD 2.22 §2.9and the information given on the relevantinstrument approach chart in EHAM AD 2.24.

4. Mandatory carriage of B-RNAV equipmenton all STARs EHAM.

Cross 15 SPL at 220 KT IAS* (unless otherwise instructed)

Navigation in the initial and intermediateapproach is primarely based on radarvectors provided by ATC.

Cross IAF at MAX 250 KT IAS

AIR

AC

AM

DT

06/1

2

AIP

NE

TH

ER

LA

ND

SS

CH

IPH

OL

ST

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DA

RD

AR

RIV

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RT

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TR

UM

EN

TA

D 2

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AM

-ST

AR

.1TRANSITION LEVEL BY ATCTRANSITION ALTITUDE : 3000 AMSL

23.1 SPY 304.2

AVERAGE VAR 0°E (2010)

31 M

AY

12

CHANGE : EHR 41E renamed 41F and 41D renamed 41E vertical limits, EHR 3 vertical limit, EHR 2A added, editorial.

Fig

ure

2-2

:R

oute

map

of

Sch

iphol

arrivals[A

IS,

2012]

MU

AC

En

Route

Dela

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bso

rptio

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apabilitie

sfo

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chip

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Inb

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L.

M.

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In order to increase the capacity of the airspace, the TMA and CTA are subdivided intosectors. There are significant differences in traffic load per time of day: at night one controllermight be able to handle all traffic in i.e. the entire CTA, but during daytime the amount oftraffic flying in and out of Schiphol Airport may be far bigger, making it impossible for onecontroller to control all traffic in the airspace. In order to make full use of the capacity of theairspace, it is desirable to deploy multiple controllers. This is done by dividing the differentparts of airspace into sectors (i.e. dividing the CTA into CTA South 1, CTA South 2, etc.).When traffic is expected to exceed the controller’s maximum capacity, the airspace will besplit into sectors. These sectors are based on the main routes and way points in the airspace.Once the amount of traffic is reduced to below the point where there is no real need for thesmaller sectors, the sectors will be merged again.

2-1-2 Upper Airspace

The upper airspace (or Amsterdam Upper Information Region (UIR)) has fewer different typesof airspace than the lower airspace. This is due to the fact that it mostly accommodates enroute traffic, and is thus not bothered with ascending and descending traffic as much as thelower airspace. In the upper airspace two types of airspace can be distinguished:

Military Airspace Similar to the military airspace in the lower airspace, also in the upperairspace the military airspace is under control of military ATC. Again, this airspace is usedflexibly, and is available to civil aviation if not needed for military purposes.

Upper Control Area For the Amsterdam FIR all airspace above FL 245 is considered tobe upper airspace (also referred to as Amsterdam UIR), which is controlled by MaastrichtUpper Area Control Centre (MUAC). MUAC’s influence is not restricted just to the upperairspace of the Amsterdam FIR: the upper airspace of Belgium, Luxembourg and north-westGermany also fall under its reigns. MUAC serves one of the busiest parts of the Europeanairspace, with peaks of up to 5000 flights a day. Although MUAC does deliver inboundtraffic to five major airports (London Heathrow, Amsterdam Schiphol, Brussels, Frankfurtand Munich) it currently is not directly involved in the arrival management process of anyof these airports. In contrast to the ACC controllers - who work with a set time to delivertheir traffic to APP - MUAC does not work with a certain time of delivery to Area Control,but delivers an aircraft around a predetermined flight level (generally FL260) and speed atone of the ACC entry points.

In the upper airspace that is managed by MUAC there are three main sector groups, againbased on the main traffic flows: Hannover, Brussels and Delta/Coastal. All divided in alower and higher airspace: lower airspace takes care of all flights between FL 245 and FL330, higher airspace minds all air traffic above FL 330. Similar to the Air Traffic Control TheNetherlands (LVNL) managed airspace, sector groups can be divided into sectors to makemore optimal use of the available airspace.

MUAC’s executive control differs considerably from the Air Traffic Services (ATS) providedby LVNL. MUAC only controls the traffic above FL 245 and does so for a larger area thanLVNL.


2-1 Airspace Structure 7

Figure 2-3: Overview of the MUAC airspace [Eurocontrol, 2014b]

2-1-3 Adjacent Airspace

The airspace structure and organisation of adjacent airspace is comparable to that of TheNetherlands. Depending on the origin of a flight, an inbound flight to Schiphol Airport is notnecessarily only served by the combination of MUAC and LVNL. Schiphol inbounds comingfrom the west will generally be delivered by National Air Traffic Services (British ANSP)(NATS) straight to LVNL without intervention from MUAC. Similarly, traffic from the southcan occasionally be controlled by Belgocontrol and some traffic from the east might directlybe transferred from Deutsche Flugsicherung (German ANSP) (DFS) to LVNL.

One other significant factor in the airspace management is the presence of military airspace.Military operations prevent significant blocks of airspace from being available for use by civilaviation. Whenever possible the military ATC will give (part of) their airspace back to theconcerned Air Navigation Service Provider (ANSP) for civil use.



2-2 Schiphol Inbound Routes

There are many routes through MUAC airspace to lead traffic to Schiphol airport, all indicatedin Figures 2-4, 2-5, 2-6, and 2-7. Table 2-1 gives an overview of the length of each route andimportant coordination points of each route. Routes that are indicated with an asterisk areroutes that cross military airspace.

Table 2-1: Schiphol inbound routes through MUAC airspace

Route Length [NM] Coordination point

Brussels

1 36 BELOB - DENUT

2 46 ADUTO - FERDI - DENUT

3 54 MEDIL - FERDI - DENUT

4 120 DIK - REMBA - HELEN

53 DIK - TERLA5 130 + SOGRI - HELEN

Hannover

1 80 IBRAM - MOBSA - NORKU

2 141 HLZ - MOBSA - NORKU

3 163 EMBOX - DLE - MOBSA - NORKU

4 115 PEXAM - LUGAX - NORKU

5 76 BIGGE - NORKU

6 82 BADGO - ADEMI - HAMM - NORKU

Jever

1* 114 GREFI - EEL

2 118 TUSKA - EEL

3 134 DEGUL - EEL

4 154 KESUR - GASTU - EEL

5 117 ABANO - EEL

6 112 LBE - WSR - EEL

7* 77 EDDW - EEL

Interestingly enough, although all routes go through MUAC airspace before connecting tothe LVNL’s lower airspace, for some routes executive control is not with MUAC at the co-ordination point where the control of the flight is given to LVNL. For all Brussels routes itis common practice to start descending early and transfer executive control to Belgocontrol,who will in turn hand the flight over to LVNL. This may complicate delay absorption in prac-tice, as it requires additional communication between LVNL and Belgocontrol, and reducesthe amount of time a flight spends within MUAC airspace. Also, flights with destinationSchiphol departing from within the MUAC airspace, or from an airport close to the MUACborders, may not be able to reach the higher flight levels within the MUAC airspace duringtheir flight time. For these flights, it can be decided to not let MUAC have executive controlat any point during the flight, even though the flight technically is within MUAC airspace.This is also reflected in the Letter of Agreement (LoA) between LVNL and MUAC, which de-scribes the flight handover procedure between MUAC and LVNL. For all routes coming overcoordination points DENUT or HELEN (Figure 2-2), no handover procedure between the


2-2 Schiphol Inbound Routes 9

two ANSPs is described, meaning that the flight will either never have been under executivecontrol of MUAC, or it has been transferred from MUAC to Belgocontrol or DFS at an earlierpoint of the flight. [Luchtverkeersleiding Nederland and Maastricht Upper Area Control]

1

2

3

Figure 2-4: Brussels routes 1, 2 and 3 [Skyvector, 2015]



4

5

Figure 2-5: Brussels routes 4 and 5 [Skyvector, 2015]

1 2

3

45

6

Figure 2-6: Hannover routes 1 through 6 [Skyvector, 2015]


2-3 Arrival Management 11

1

3

2

4

5

6

Figure 2-7: Jever routes 1 through 7 [Skyvector, 2015]

2-3 Arrival Management

Air traffic with destination Schiphol Airport can enter the lower airspace from many direc-tions. Especially during inbound rushes it is important for ATC to be able to think andplan ahead. Air Traffic Controller (ATCo)s are supported in this by the arrival managementprocedure, which will be described in this section. After the current procedure has been de-scribed, some attention is given to the future of arrival management, and how en route delayabsorption can potentially tie into arrival management procedures.

2-3-1 Current Arrival Management Procedure

When an aircraft is flying towards its destination airport the Arrival Management processalready starts some time before touch-down. In the current situation the inbound planningstarts about 80 NM away from the airport, which is equivalent to about fourteen minutesbefore entry of the TMA. At this point the aircraft will be assigned to a landing slot by theArrival Planner (AP). The AP has an overview of all the traffic coming in, and plans landingslots for traffic coming from all different directions. The landing slot results in a time atwhich the flight is required to be over the IAF: the Expected Approach Time (EAT). TheACC controllers aim to deliver the aircraft to the TMA entry point within a margin of twominutes of the EAT. [Renee Pauptit, 2014]

It happens very frequently that two or more aircraft enter the planning horizon of fourteenminutes before TMA around the same time. In this scenario one or more of these aircraftwill have to absorb a delay in order to comply with the set airborne and runway separationstandards. Absorbing several minutes of delay in this short amount of time, however, is quitechallenging. If delays become too big they can not be resolved merely by vectoring (pathextensions) and/or speed adjustments, and ATC will generally need to resort to the holding



stacks just outside the TMA. An explanation of the current delay absorption measures usedin the CTA and TMA can be found in the preliminary thesis. [Renee Pauptit, 2014] [LisanneM. C. Adriaens, 2014]

Once an aircraft enters the TMA, the APP controllers have to merge the traffic coming fromthe three IAFs in a sequence for landing. Depending on the number of available runwaysthey will create one or two sequences of properly spaced aircraft. The sequence is establishedby evaluating the relative positions of the incoming traffic, and usually goes on the basis offirst-come, first-served. Depending on how strictly ACC ATC has delivered their flights tothe IAFs at their designated EATs, changes might or might not still be made to the sequence.[Renee Pauptit, 2014]

A graphical representation of the standard arrival routes to Schiphol airport can be seen inFigure 2-2.

2-3-2 Future Arrival Management Procedure

As part of Single European Sky ATM Research (SESAR), the Pilot Common Project (PCP)regulation has been implemented by the European Commission (EC), which focusses on sixATM functionalities that should be deployed across all SESAR member states. ‘ExtendedArrival Management and Performance Based Navigation in the High Density TMAs’ is definedas one of these six functionalities. Of this functionality “it is expected to improve the precisionof approach trajectories as well as to facilitate traffic sequencing at an earlier stage, thusallowing reducing fuel consumption and environmental impact in descent/arrival phases.”[European Commission, 2014]

This regulation sets a clear goal to implement extended arrival management with planninghorizons out to a minimum of 180-200 NM. Since LVNL is not responsible for the upperairspace it will have to resort to cooperation with MUAC and NATS (British ANSP) mainly,and Belgocontrol (Belgian ANSP) and DFS (German ANSP) complementarily. Luckily, theSingle European Sky initiative has lead to the creation of Functional Airspace Blocks (FABs).LVNL falls under the FAB Europe Central (FABEC)1, a ‘work group’ of ANSPs that works to-wards achievement of the goals that were set at a European level for the ATM sector. [FABEC,2008] As part of the intention is to implement Arrival Management (AMAN) in the FABECairspace, an extended arrival management project called ‘Cross Border Arrival Management(XMAN)’ is currently running. This cross-border arrival management project involves EnRoute Management (ENMAN) and Departure Management (DMAN), alongside AMAN.

As stated before, the planning horizon of 80 NM (the equivalent of 14 minutes before IAF) istoo short to incorporate the en route phase in the arrival management procedure. ThereforeFunctional Airspace Block Europe Central (FABEC) is aiming with its XMAN project toextend the planning horizon from 80 NM to 180-200 NM for a selected group of airports2.The PCP has more extensive plans, aiming to implement extended arrival management op-erations for 24 European airports by 2030, of which 13 are in the FABEC region. [EuropeanCommission, 2014]

1FABEC consists of Belgocontrol, DFS, Direction des Services de la Navigation Aerienne (French ANSP)(DSNA) (French ANSP), ANA (Luxembourgish ANSP), Skyguide (Swiss ANSP), and MUAC.

2London Heathrow, Munich Franz Josef Strauss Airport, Frankfurt International Airport, Paris Charles deGaulle Airport and Amsterdam Schiphol Airport


2-4 Current Delay Absorption & Sequencing Measures 13

2-4 Current Delay Absorption & Sequencing Measures

For en route control, a clear distinction must be made between delay absorption and sequenc-ing measures. Delay absorption measures are regarded as measures directly intended to takeaway time from a flight being placed in a stack, whereas sequencing - although it can resultin delay absorption - is meant to serve separation and safety standards only. En route AT-Cos will try to sequence the traffic for sub- or adjacent centres, as far as this is practicable.This means that it is not mandatory for en route control to deliver sequenced traffic to theirneighbouring ANSPs.

Although en route control has the power to change routes and trajectories, it does not do sowithout specific requests from adjacent ANSPs (i.e. due to weather conditions, flow controlmeasures, etc.). Even these specific requests from other ANSPs to absorb delay do not requireen route control to absorb (part of) the entire delay. In this case, similar to the sequencingissue, en route control only complies so far as is practicable.

Within MUAC airspace there is currently only one trial that actively works on delay absorp-tion in the en route airspace, which is the London Heathrow XMAN trial. As described inthe preliminary thesis, en route control at MUAC gives a standard 0.03M speed reductioncommand to traffic inbound to LHR when holding times are exceeding 8 minutes. [LisanneM. C. Adriaens, 2014] No additional or other measures are taken to absorb more delay. Whena delay is requested by neighbouring ANSPs, MUAC controllers try to meet these requestsfor as far as they are practicable. Unlike the XMAN trial, in this situation the ATCo willgenerally communicate a different ‘time over’ the coordination point the affected flight, ratherthan giving a speed command.

For safe operations the separation standards of 5 NM lateral separation and 1000 ft verticalseparation are used. If an ATCo can not establish these separations solely by using speedreduction, he or she will resort to path extensions and/or flight level reductions. Dependingon the state of the flight and the interactions of a flight with other traffic, the ATCo will decidewhat changes need to be made to the flight’s trajectory. For example, if an aircraft is alreadyclose to its destination, it can be more favourable to reduce the flight level rather than toreduce the speed. A flight that has just departed will preferably be kept at its optimal cruisealtitude, as lowering the flight level in an early stage of the cruise can result in significant fuellosses over the entire flight. In this last case it might be more favourable to give an aircrafta slight path extension to avoid traffic conflicts. An ATCo tries to keep these considerationsin mind when managing his or her traffic, since after safety, efficiency is an important factorin ATC.

The measures that will be described in the remainder of this chapter are all measures thaten route controllers at MUAC are familiar with. However, in the case of en route delayabsorption it can be requested from en route control to use these measures outside of theirusual scope of establishing sufficient separation between aircraft.

2-5 Definition of Delay

As described in 2-3, an aircraft is assigned the next available landing slot when it comes withinplanning range. For Schiphol Airport inbounds this is when a flight enters the Amsterdam



FIR. ATC works with the ‘First come, first served’-principle, so any previously amounteddelay (i.e. ground holding or en route delay) does not matter for the assignment of a slot.The only delay relevant for this research is the delay that is accumulated during the time aflight is under control of ACC and APP controllers: the FIR delay, which is the differencebetween the unimpeded time from FIR entrance to touchdown, and time from FIR entranceto actual touchdown at EHAM. The initially planned time of arrival that has been set before

departure is thus of no relevance to the amount of delay that is to be absorbed in the upper

airspace.

2-6 Influential Factors

Several factors that affect the amount of delay that can be absorbed have been identifiedduring the preliminary research. These are:

• Airline intent Every airline has its own strategy when it comes to optimising itsoperations. Low cost carriers and charter airlines are generally less concerned with on-time performance and more focussed on low fuel and operational costs, whereas on timeperformance is of importance to airlines operating with a hub-and-spoke network. Thiswill be reflected in the cost index the airline uses, a value which can vary per flight. Thecloser the cost index is to zero, the more important fuel cost is to them. If an aircraftis given a speed adjustment by the ATCo, the pilot can indicate whether he/she is ableto meet the demanded adjustment. Generally, it is to be expected that airlines will notwant to operate at a speed lower than the Maximum Range Cruise Speed (MRC), themost fuel efficient speed of an aircraft. This makes it possible for some flights to havea bigger margin to reduce speed than others.

• Traffic mix The mix of aircraft that an ATCo has to deal with influences the workloadof the controller. If aircraft with large differences in speed are on the same route, it islikely that the controller will have to intervene to preserve separation standards. If aflight is holding back other flights, the controller will clear it to a lower flight level suchthat other flights can pass by. [Skybrary, 2014]

• Traffic pattern & density The amount of traffic in the air varies over time. Loads aregenerally lower at night than during the day, which creates some room in the airspaceto absorb delays without obstructing other flights. Also, as some airports close duringthe night, or because of natural peaks and troughs in the directionality of the air trafficthere might be better opportunity to absorb delays in one situation than in another.

• Weather conditions As Schiphol come from all directions, weather conditions can beexpected to be different at the various inbound routes. Headwinds can cause trafficon some routes to have a significantly lower ground speed than an aircraft flying atthe same True Airspeed (TAS) with significant tailwinds. Not only between routes,but also between flight levels, winds can change substantially. In extreme weathersituations, such as thunderstorms, traffic may even have to be diverted, resulting inhigher workload for ATC and thus lower potential for delay absorption.


2-7 Delay Absorption Tactics 15

• Aircraft type Each aircraft has different performance characteristics, making that alsothe ability of each aircraft to absorb delay will differ. By using aircraft performancemodels accurate analyses can be made of how much delay can be absorbed while keepingindividual aircraft’s performance characteristics in mind.

• Route There are several routes leading aircraft from various directions through theMUAC airspace into the LVNL airspace. All these routes have different characteristics,not only in length but also in the flight levels at which is flown, the limitations infreedom because of proximity of military airspace or oncoming routes. The design of aroute might make a difference in the delay absorption tactic that can be used and in itseffectiveness.

• Weight Depending on the weight of an aircraft, the range of speeds it can operate willvary. The heavier an aircraft, the more lift and thus a higher TAS is required to keepthe aircraft in the air.

• Availability of military airspace Access to military airspace provides (mostly) enroute controllers with a bigger playing field and thus with the option to put aircraft onmore direct routes.

2-7 Delay Absorption Tactics

During the preliminary phase of this research, four delay absorption tactics have been estab-lished. A description of these tactics can be found in Table 2-2.

Table 2-2: Delay absorption tactics

Name Speed reduction Path extension Altitude reduction

Linear Holding Yes No NoDetouring Yes Yes NoDropping Yes No YesTurtling Yes Yes Yes

To let the flights absorb delays in the simulation, the respective changes in speed, altitude andheading should be implemented as well. Rather than testing one delay absorption tactic perrun for all to be delayed flights, a more dynamic approach was decided upon. This dynamicapproach means that each aircraft will be delayed using a tactic that is appropriate to thesize of the delay that is to be absorbed. Small delays can be managed by using linear holding,where the biggest delays will probably have to rely on turtling. Ideally, the speed reductionwould not go lower than the MRC, but it can be decided to go to minimum operating speed.


Chapter 3

Research Design

Now the relevant background information is known, it is time to further explore the structureof the research. The questions this research aims to answer and which variables will be takeninto account are considered in this Chapter.

3-1 Research Questions

From the preliminary research the notion has arisen that there is potential in the idea ofen route delay absorption. The way FIR delay is currently absorbed in the lower airspaceresults in disadvantages that could potentially be reduced, or maybe even resolved, by enroute delay absorption. An extension of the arrival planning to the en route phase might thusbe a possible solution to optimise the current arrival management process. However, there isno data available whether en route delay absorption is feasible, and if it is, how it should bedone. These considerations have resulted in the following research questions:

“How much delay can be absorbed by MUAC for Schiphol airport inbound flights?”

1. How much delay could be absorbed by MUAC under optimal conditions?

2. What is the most effective way to absorb FIR delays en route?

3. How much more fuel efficient is en route delay absorption than delay absorption inthe lower airspace?

4. Which factors (independent variables) have the biggest impact on MUAC’s delayabsorption capabilities?

5. What are the effects on air traffic flying towards other destinations than Schipholairport?

6. Are the found delay absorption rates workload feasible for ATCos?


18 Research Design

3-2 Research Objectives

To work towards the answers of the research questions stated in Section 3-1 and to clarify themain goals of the thesis research, the following list of research objectives has been made.

1. Listen to and consider all involved stakeholders’ needs. The main stakeholders and theirinterests are listed in Table 3-1.

2. Equip BlueSky with means to plan arriving traffic, and to actively optimise the use ofdelay absorption tactics with respect to fuel absorption and controller workload.

3. Provide a simulation that accurately represents the traffic situation in the MUACairspace.

4. Analyse the effects on en route traffic situations caused by en route delay absorption.

5. Provide a list of the impact of the independent variables on delay absorption capabilities.

6. Deliver a report that explains and summarises the main conclusions that can be drawnfrom the results.

3-3 Independent Variables

The influential factors found during the preliminary thesis research, also listed in Section 2-6,have been divided into simulation variables and independent variables. Because of the ratherlarge number of influential factors it is impossible to investigate the effects on delay absorptioncapabilities of every single one of them during this research. Hence the decision was madeto select two factors that will be used as drivers for the scenario selection. The two selectedfactors are:

• Traffic density & pattern

• Traffic mix

This decision was made based on the assumption that these factors have the biggest influ-ence on delay absorption capabilities and would thus be the most important contributors torepresentative results. The remaining factors are:

• Airline intent

• Weather conditions

• Aircraft type

• Route

• Aircraft weight


3-3 Independent Variables 19

• Availability of military airspace

Although no active scenario selection will be performed to ensure an exhaustive range of theother influential factors, this does not mean the effects of the remaining influential factorscould not be apparent in the results. Depending on the data that will be used for the creationof the scenarios, some of the other factors may be represented well enough to draw conclusionson their influence as well. A more in depth review of which other factors will be evaluated isgiven in Chapter 6, alongside a more elaborate discussion on the scenario selection.


20 Research Design

Table 3-1: Research project stakeholders

Thesis research stakeholders Interest

LVNL

• ATCo acceptability

• Possible reduction of controller workload

• Efficient operations

• Effects on quality of service

• Airspace capacity

MUAC

• ATCo acceptability

• Aware of potential increase of controller workload-/decrease in controller productivity

• Effects on quality of service

• Airspace capacity

• Obtain insight in influence of airspace character-istics on delay absorption

Other ANSPs

• Implementation of en route delay absorption forother airports

• More optimal use of airspace

• Providing more fuel efficient operations

Scientific community/DUT

• Expansion of the BlueSky ATM Simulator

• Analytical approach to a practical problem

Airlines

• Potential of reducing fuel cost due to optimisedarrival management process

General public

• Less nuisance due to low altitude delay absorption

• Environmentally friendlier operations


3-4 Dependent Measures 21

3-4 Dependent Measures

The goal is to find answers to the research questions posed in Section 3-1. To find the answersthe following dependent measures should be evaluated:


• Maximum delay absorption for each delay tactic, per flight, per route

2. What is the most effective way to absorb FIR delays en route?

• Maximum delay absorption for each delay tactic, per flight, per route

• Total additional time spent by all flights within MUAC airspace

3. How much more fuel efficient is en route delay absorption than delay absorption inthe lower airspace?

• Amount of additional fuel consumption


• Amount of additional workload

5. Which independent variables have the biggest impact on MUAC’s delay absorptioncapabilities?

• Amount of additional workload

6. What are the effects on air traffic flying towards other destinations than Schipholairport?

• Number of conflicts with non-EHAM flights


22 Research Design


Chapter 4

Simulation Design

Throughout this research, the BlueSky Open ATM Simulator (further: BlueSky) is used tosimulate and analyse the traffic. As not much detail has yet been given on the workings ofBlueSky, this chapter will provide a more elaborate review of BlueSky’s capabilities, followedby the additions that are required to get the answers to the research questions.

4-1 BlueSky Open ATM Simulator

BlueSky is an open ATM simulator that has been developed by Prof. dr. ir. J. M.Hoekstra at Delft University of Technology. The simulator is based on the Python pro-gramming language (version 2.7), and is freely available through its designated Github page(www.github.com/ProfHoekstra/bluesky). To enhance runtime performance, the simulatoris written in a vectorised way.

The simulator consists of five main modules that are being called from the main BlueSky file(bluesky.py) to display the traffic in the simulation. A screenshot of BlueSky with no trafficin it can be seen in Figure 4-1. Let’s discuss what each of the modules does to generate thesimulation:

• Simulation The simulation class updates the different times that are used in the sim-ulation and provides the start, pause and stop functionalities of the simulation.

• Stack Commands can be given to the simulator through the command window andthrough a scenario file. The stack class is able to interpret the commands given to thesimulator, which can range from creating (CRE) or deleting (DEL) flights to alteringthe speed (SPD), altitude (ALT), heading (HDG), or even the route (ADDWPT) of aflight. An exhaustive list of BlueSky commands can be found in Appendix B.

• Traffic The traffic class makes up the behaviour of the aircraft. Its main attributes arethe route and performance classes.


24 Simulation Design

• Tools The tools class is built up by a range of functionalities that do not directlyfit under any of the other denominators. Think of atmospheric calculations (i.a. airdensity, temperature as a function of altitude) but also performance definitions for i.e.minimum speeds and performance limits.

• User Interface The structure behind the user interface makes sure the user is sup-ported throughout the use of BlueSky. This is through a menu to select the scenario filethat should be simulated, but also by means of a menu (top left corner of Figure 4-1)through which alterations can be made to the display and traffic.

Figure 4-1: Screenshot of the BlueSky Open ATM Simulator

The most important features of BlueSky for this research is the possibility to put in prede-termined routes through scenario files. An example of what a typical scenario input for thisresearch looks like can be found in Appendix A. Routes are set out by means of waypointsand the associated altitude and speed an aircraft should have at this waypoint. The LateralNavigation (LNAV) and Vertical Navigation (VNAV) modes are switched on for each flightin the research to make sure the flights meet the altitude and speed requirements. Becauseof their crucial role in obtaining realistic flight profiles, the detailed workings and effects ofusing these modes will be explained in some more detail.

Another crucial feature is the Airborne Separation Assurance System (ASAS) functionality.ASAS reports and resolves conflicts, and can thus be of great importance in analysing thesnowball effects of en route delay absorption of EHAM inbounds on non-EHAM inbounds.

4-1-1 Lateral Navigation

Lateral navigation is triggered by including the ‘LNAV ON’ statement in the scenario, as canbe seen in Appendix A. When an LNAV activated flight passes a waypoint and commences itsroute onto its next waypoint, a different heading may be required. This difference is computedsimply by taking the current aircraft heading and comparing it to the heading between the


4-1 BlueSky Open ATM Simulator 25

aircraft’s current position, and the waypoint it should be moving towards. Based on theaircraft type and flight phase, a default bank angle (φ) will be assigned, which can be usedto establish the turn radius as through Equation 4-1.

rturn =TAS2

φ(4-1)

With the turn radius known, the minimum distance required to make the turn to the nextwaypoint through Equation 4-2.

dturn = |rturn · tan (0.5 · (ψac − ψwp)| (4-2)

If the distance between the aircraft and the next waypoint is bigger than dturn, the turnwill be initiated right away. In case the turn is not feasible within the distance to the nextwaypoint, the ‘active’ waypoint is transitioned to the next available waypoint in the route,for which rturn and dturn will be computed until the next closest waypoint is found wheredturn is smaller than the distance to the next waypoint.

4-1-2 Vertical Navigation

Similar to the LNAV mode, VNAV can be triggered by introducing the ‘VNAV ON’ statementin the scenario file. Although the vertical navigation during descent is most important for thisthesis, naturally, also the climb is taken care of by the VNAV mode implemented in BlueSky.

For the descent, a standard descent rate of 3000 ft per 10 NM is assumed. ATCos reported thatdifferent airlines have different descent strategies; some opting for lower rates with presumedhigher passenger comfort, others preferring steep descents to fully benefit from the fuel efficientflying at high altitudes. Based on this rate, the Top of Descent (TOD) is computed. As soonas the aircraft passes the TOD, the descent is initiated with the afore mentioned standarddescent rate. Typically, each airline has its own tactic on when to start the descent and atwhich vertical speed to do so. Some airlines will value passenger comfort over fuel efficiency,and therefore prefer to have a slightly lower vertical speed during descent, whereas othersmay prefer a higher descent rate to fully benefit from the fuel efficient flying at high altitudes.Making the assumption of a standard descent rate thus slightly affects how well the outcomewill match the real traffic situation.

The climb logic is slightly different: rather than assuming a standard rate, the requiredvertical speed to meet the altitude constraint at the next waypoint is computed. Naturally,this value is bounded by the maximum vertical speed.

4-1-3 Airborne Separation Assurance System

The built-in ASAS provides conflict identification and resolution within BlueSky. A conflict isdefined as two aircraft coming within a radius of 2.5 NM and 1000 ft lateral from each other.Conflicts are resolved following the method described by Martin S. Eby, which boils down toresolving conflicts by giving the smallest possible lateral detour. [Martin S. Eby, 1994]



This way may be the most efficient way to resolve a conflict, it is, however, not necessarilyrepresentative of what an ATCo would do. Research into ATCo conflict resolution, performedby Rantanen, shows a significant preference of controllers to resolve conflicts by means ofvertical trajectory changes, rather than lateral changes. [Esa M. Rantanen and ChristopherD. Wickens, 2012] [Esa M. Rantanen, Jiazhong Yang and Shanqing Yin, 2006] Apart fromthis preference, there are also other factors that an ATCo will take into account, that arenot considered by the automated conflict resolution in Eby’s method. Think of distanceto destination, planned cruise level, and the effects on the evolution of the traffic, also foradjacent sectors. Since these effects are not apparent through Eby’s method, also the conflictresolution will not be representative of a solution a controller will come up with. It wasconsidered to build in a new logic to more accurately represent conflict resolution, but thisidea has ultimately been rejected. To properly develop such logic would require a lot of timeand research, which is unfortunately beyond the scope of this thesis. Because of this decision,only the conflict detection, and no conflict resolution, will be used during the simulations.

4-2 Simulation Structure

The simulation process can be simplified into three phases: taking in the input, processingthe input, and generating the output.

There are two ways of providing traffic input to BlueSky: either through a scenario (.scn)file containing all the required data, or through manual keyboard inputs that can be giventhrough the command window (bottom left of Figure 4-1. It is always possible to commandchanges to the traffic in the simulation through the command window, even if the data is fedto the simulator with a scenario file. However, in general the command window is only usedduring scenario simulation for basic screen related changes (zoom in, zoom out, show flightplan of a flight), rather than to alter the trajectory of a flight.

During the actual simulation, the traffic is flying according to the trajectories specified.

The main output is the visualisation of the traffic on the screen. Of course the raw data usedto compute this visualisation can be extracted from the simulator, but there is no standardisedway of doing this. If output data is required, a separate module should be written to ensureextraction of the right data in the right format.

4-3 Required Additions to BlueSky

Although BlueSky already supports the general simulation of air traffic, for this research someadditional tools/functionalities are required. Part of this is required before the simulation isstarted, some additions are needed for when the simulation is running, and finally someprocessing tools are required to process the output.

To avoid manually having to change all flights that are up for delay absorption during thesimulation, it would be nice to either incorporate the application of delay absorption tacticsby the simulator, or by changing the scenarios that are fed to the BlueSky. It was decided towork with the latter option, simply because it is the easiest to make. Changing the scenarios


4-3 Required Additions to BlueSky 27

requires information on the size of the planning conflicts and how to apply which delay tactic.How this is incorporated in the scenario creation will be explained in Chapter 5

During the simulation the data that is required to assess the workload, fuel consumption andconflicts needs to be stored. This is done by adding a module to the simulator that storeswhat happens at each second of the simulation. Based on this data, additional python scriptsshould be written to convert this raw data to sensible graphs and numbers, fit for presentationin Chapter 7


Chapter 5

Simulation Details

The additions that are required for this research have been introduced in Chapter 4. Thischapter gives a more in depth review of what these additions do and how they are made tofit the BlueSky simulator.

5-1 Planning Conflict Detection

In order to determine the amount of delay that a flight should ideally absorb, an indication ofthe planning conflicts that occur is required. The delay that is to be absorbed is determinedusing a separate Python script that uses the last filed flight plans from the Eurocontrol DDR2Database. This file contains all required route information. The flowchart in Figure 5-1 showsthe procedure the script takes to determine the size of the planning conflicts.

The assumptions that are made are:

• All flights are operated exactly as planned in Eurocontrol’s Demand Data Repository 2(DDR2)

• All planning conflicts are resolved by slowing aircraft down. Speeding up of aircraft isnot considered.

• Two runways are planned for during the inbound peaks as indicated in Table 5-1.

• Landing intervals are always a minimum of 90 seconds.

To reflect the so-called ‘sixty flight rule’ in the runway planning, the double runway configu-ration is assumed to start ten minutes before the official inbound peak times as referenced inTable 5-1. This rule states that LVNL is allowed to have four runways operational outside ofpeak times to accommodate a total of 60 flights per day. [Evert, klopt 60? Bron?]

Whether an aircraft is flying through MUAC airspace is not taken into consideration whenassigning the delays, so all flights get the delay assigned to them that is representative of thetraffic situation. Delays have not been transferred from non-MUAC to MUAC flights as thiswould inflict the principle that traffic from all directions should be treated equally.


30 Simulation Details

Start Conf ict

Detect on

Eurocontrol

.so6-f le

Filter EHAM inbounds

on ARTIP, SUGOL,

RIVER

1 or 2

runways?

Set: �t � 90s

Delay = �t - 90

Set: �t � 45s

Delay = �t - 45

Store f ight number +

delay in dict

End Conf ict

Detect on

Figure 5-1: Simulation structure of the conflict detection code

Table 5-1: Inbound peaks at Schiphol Airport [Eurocontrol Experimental Centre, 2003]

Inbound peak times [UTC]

06.00 - 08.0010.00 - 10.4012.00 - 12.4014.00 - 15.0017.20 - 19.00

5-2 .so6 to .scn Conversion

The BlueSky simulator works on scenario files (.scn) rather than on Eurocontrol’s .so6-files. Asthis concerns a mere conversion from one data format to another, this will not be expandedupon in the main body of this thesis. More detailed information on the structure of thisconversion procedure can be found in Appendix A.

5-3 Delay Tactics Implementation

The .so6 to .scn conversion has resulted in the scenario for the ‘dry’ run, that will be used toobtain data on the unimpeded, original trajectories of the traffic. However, the delay tacticsshould be implemented in these scenario files as well. This section elaborates on the reasoningbehind and implementation of the four delay absorption tactics.


5-3 Delay Tactics Implementation 31

5-3-1 Linear Holding

Linear holding means that the delay will be absorbed by means of a speed reduction on theoriginally planned route through the MUAC airspace only.

To get to the right amount of delay absorption, there are two options:

• Have a standard speed instruction, i.e. reduce speed by 0.02M, with a variable point atwhich this command should be given to get the right distance required to absorb thedelay.

• Have a variable speed instruction that should be given upon entry of the MUAC airspace.The size of the speed reduction would be based on the full distance still to cover withinMUAC airspace and BADA aircraft performance estimates.

In MUAC’s current operations, when an aircraft is requested at another time over the coor-dination point than planned, the ATCo will communicate this change in time with the pilot.The pilot can then change this in the Flight Management System (FMS), and the aircraftcan determine its new optimal trajectory to this point. This is slightly different through theXMAN trial, where no ‘time over’ command, but a command to reduce speed by 0.03M, isgiven. If a flight is already flying slow, and a speed reduction of 0.03M is not feasible, speedwill be reduced by whichever amount is feasible. It is important to note that speed instruc-tions at MUAC are given in Mach, up to two decimal points. This means that, even thoughit might be desirable to have an aircraft reduce its speed by 0.023M, a speed instruction of0.02 or 0.03M will be given by the ATCo.

The maximum range cruise speed is not the lowest speed an aircraft can fly at, which wouldbe the minimum cruise speed Vmin. ATCos do not know the MRC or Vmin exactly for anyaircraft, making it hard to estimate the effects of a speed command given to an aircraft.The differences between various airlines’ speed strategies (some decide to fly closer to MRCthan others) only adds to the difficulty of estimating the effects of speed reduction to MRC.Generally, when ATC requires an aircraft to reduce its speed, they ask for a standard reductionof i.e. 0.02M. The pilot of the affected aircraft can then indicate whether this is feasible or ifthis speed reduction would push him below Vmin.

However, for the sake of the research it was decided not to work with standard speed reduc-tions, but rather use speed reduction to an aircraft specific value like the MRC. The goal isto investigate the delay absorption capacities of the MUAC airspace, and using a standardspeed reduction would not solicit the full range of speed reduction measures. Hence speedalterations will be made in knots, not in Mach.

The maximum amount of delay that can be absorbed efficiently through linear holding is byreducing the speed to the MRC. This speed can be found using Equation 5-1.

Speeds in original flight plans are quite variable, for the delay absorption part it was decidedto only let aircraft slow down further, rather than having the possibility to speed up in themeantime.

MRC = max(

√CL

CD) (5-1)



The maximum amount of delay TMaxLinHoldthat can be absorbed can then be found through

Equation 5-2.

TMaxLinHold=DistanceMUAC

MRC− DistanceMUAC

VCAS(5-2)

If the amount of delay that is to be absorbed TDelay is smaller than TMaxLinHold, the speed

will only be reduced to the value required to absorb the delay, according to Equation 5-3.

VCASLinHold= MRC +

TDelay

TMaxLinHold

· (VCAS −MRC) (5-3)

5-3-2 Dropping

As explained in the preliminary thesis, and shown in Figure 5-4, the flight envelope opensup at lower altitudes, and with it the MRCT AS lowers.[Lisanne M. C. Adriaens, 2014] Theamount of delay that can be absorbed is thus variable by the number of flight levels that anaircraft is lowered, and the resulting margin between the current speed and the MRC at thechosen flight level.

To get to the right amount of delay absorption, there are two options:

• Have a variable change in flight level, such that a flight level can be selected at whichreduction to MRC means the delay absorption requirements are met.

• Have a standardised change in flight level, i.e. always drop to FL300 or always dropby 2000ft, and get to the required delay absorption by a variable speed reduction to aspeed somewhere between current speed and MRC.

Discussion with ATCos resulted in the decision to work with a standard flight level reduction,as depicted in Figure 5-2. Some consistency is required in order for ATCos to be able tocoordinate the traffic in their sectors. It is already difficult for an ATCo to estimate Vmin

at cruise level, it would be all the more complicated to do so for many different aircraft alldescending to different flight levels.

As can be seen in Figure 5-3, most EHAM inbound traffic in the MUAC airspace have a flightplan that is filed for the even flight levels. It is common practice to reserve even levels for onedirection of flight and uneven levels for flights in opposite directions. Having the flights atthe high flight levels descend an odd number of flight levels can thus result in head on conflictsituations. Also, descending through many flight levels might cause conflicts with ascendingtraffic coming from other airports and traffic flying at lower levels. As a result the decisionwas made to start off with the realistically smallest possible, fixed amount of 2000ft.

In the simulation, flights will not drop below the agreed upon flight level of 260. In prac-tice, it may be desirable to have the aircraft continue their descent through subjacent airspacebefore entering the LVNL airspace, rather than adding a level segment at the end of the trajec-tory within MUAC airspace. However, allowing aircraft to descend through another ANSP’sairspace is an assumption that alters the amount of time spent within MUAC airspace, andcomplicates drawing conclusions on the delay absorption and number of conflicts occurringbecause of delay absorption measures. Hence it was decided to work with a level hand-oversegment rather than a descending hand-over.



Figure 5-2: Schematic representation of dropping

49.5 50 50.5 51 51.5 52 52.5 53 53.5 54 54.5 550

100

200

300

400

EHAM Inbound Descents

Longitude [Degrees]

Flig

ht L

evel

[−]

2.5 3 3.5 4 4.5 5 5.5 6 6.5 70

100

200

300

400

Longitude [Degrees]

Flig

ht L

evel

[−]

Figure 5-3: Plot of inbound EHAM traffic

5-3-3 Detouring

Detouring, more commonly referred to as dog-legging or vectoring, is typically used in theupper airspace for technical sequencing. Detouring has two factors that affect delay absorp-tion: the size of the path extension and the size of the speed reduction. Again, this results intwo options to absorb the right amount of delay using detouring:

• Have a variable change in flight path, whilst always reducing speed to MRC.

• Have a standardised change in flight path for each route, and get to the required delayabsorption by a variable speed reduction to a speed somewhere between current speedand MRC.

In the current operations, MUAC controllers can use doglogging or vectoring as a means tocreate safe separation. Controllers are free in their selection of alternative routings, but thereare general standards between path extensions for different routes. These common practices



0 5000 10000 15000 20000 25000 30000 35000 40000Altitude [ft]

200

250

300

350

400

450

500

550Maximum range cruise speed [Knts TAS]

Narrow bodyWide body

Figure 5-4: Maximum range cruise speed vs. altitude [Eurocontrol, 2013]

are often indirectly dictated by the structure of the airspace, i.e. the availability of militaryairspace, the airspace available between inbound and outbound routes and the predominantdirection traffic is travelling in.

During interviews with ATCos of all MUAC sectors, controllers expressed their concerns withregards to the feasibility of detouring for some of the routes. As some routes are relativelyshort, controllers would have a scarce amount of time to provide a flight with the appropriateinstructions for a detour. For other routes, the concern was regarding the airspace structure,where inbound and outbound routes are sometimes so intertwined that there is simply almostno space for detouring operations. This can be seen for the EHAM inbound and outboundroutes through MUAC airspace in Figure 5-5.

Because of these concerns, the feasibility of detouring for all routes has been evaluated, takingconcerns raised by the ATCos into account. From this evaluation it was decided that noneof the routes within the Brussels sector are up for detouring. For the short routes (shorterthan 50 NM) there is simply not enough time to get an airplane to deviate from its trajectoryand back on track in time before control is transferred to LVNL. An additional difficulty withthe southern routes is that control is often transferred to Belgocontrol, who in turn transfercontrol in due time to LVNL. This additional transfer of control makes it even more difficultto plan and execute a detour, which results in the long southern routes to also be disregardedfor detouring.

For the Hannover sectors, the objections to detouring lay in the structure of the airspace. Thetwo longest routes within within these sectors (HLZ-MOBSA-NORKU and EMBOX-DLE-MOBSA-NORKU) would seem most suitable to detouring, simply because of their length.However, both routes are ‘trapped’ between military airspace to their North, and an East to



3 4 5 6 7 8 9 10 1149.5

50

50.5

51

51.5

52

52.5

53

53.5

54

54.5

55

Longitude [Degrees]

Latit

ude

[Deg

rees

]

EHAM Traffic

InboundOutbound

Figure 5-5: Plot of inbound and outbound EHAM traffic [Eurocontrol, 2014a]

West route to their South. Hence, detours for traffic on one of these routes is not realistic.

The other three routes entering the MUAC airspace from the South-East may be slightlyshorter, but still spend plenty of time within the sector to be given vectoring commands. Here,the obstruction to detouring is again in the potential detour trajectories and their interactionwith other routes. For all routes the logical diversion would be over the HMM navigationalaid, but this point is also a junction for routes in all different directions. Diverting an aircraftover this point would mean crossing several other routes, and - if traffic is present - complexsituations for the ATCo to resolve. Finally, another important notion is the proximity of theairports in Dusseldorf and Frankfurt, which feed significant flows of ascending and descendingtraffic through the Hannover sectors. The combination of the complexity this adds to thetraffic situation and the structure of the airspace itself make that no detours will be consideredfor LVNL inbound routes through the Hannover sectors.

This leaves the routes through the Jever sectors as the only routes that are still up forevaluation of potential route extensions. Luckily, these routes show somewhat more potentialfor extension: there are no busy airports in the vicinity, and the airspace is less crowded withroutes in other directions. The routes through military airspace (GREFI-EEL and EDDW-EEL) are not considered, as it is assumed that military airspace is not available. This leavesfive routes, of which two routes enter from an almost identical direction (DEGUL-EEL andKESUR-EEL). Where the DEGUL-route goes directly to EEL, the KESUR-route makes useof a slightly bent trajectory via GASTU. Rerouting the DEGUL-route through the GASTUwaypoint does not result in the crossing of other routes, and extends the route with 2.1 NM.

The ABANO-EEL route has two possible extensions: flights can be redirected to the KESUR-GASTU or the DEGUL-EEL route. Because the KESUR-GASTU route is a relatively quieterroute than the DEGUL-EEL route, and because it is closer to the ABANO-EEL route than theDEGUL-EEL route, using the KESUR-GASTU detour prevents ABANO flights from crossingthrough too many other routes. Added benefit of this option is that it will see flights continue



their original flight plan from GASTU onwards. The variation to the ABANO detour via theDEGUL-EEL route extends the route by 5.2 NM, whereas the KESUR-GASTU detour wouldresult in an additional path length of 2.7 NM. For this research it was decided to work with theKESUR-GASTU extension, as it crosses less other routes than the DEGUL-EEL extension,and because the KESUR route is more quiet with EHAM traffic than the DEGUL-EEL route.

The LBE-WSR-EEL route will not be considered for detouring, as there is very little trafficcoming through this route. Any traffic inbound to EHAM using this route would be flightsfrom Hamburg Airport. Because of their short duration these flights have a cruise level ofFL260, which makes it likely for these flights to not even be handled by MUAC, but ratherby DFS.

From the north there is also the TUSKA-EEL route, which is encapsulated by militaryairspace on both sides. The advantage of this corridor is that there is no traffic in dif-ferent directions, hence no consideration of interference with other traffic is required. Themargin for manoeuvering, however, is limited, with a largest possible deviation of 1.0 NM.This path extension would be established by vectoring a flight to the East until it interceptsthe bottom left corner of the military airspace (as indicated in Figure 5-6), before giving itdirections to fly towards NIRDU and continue the originally planned flight from then on.

Because typically the additional path length is inserted when the aircraft are still at cruiselevel, the new waypoints are added to the flight plan at the same flight level and speed as theJever sector entry flight level. The required additional delay absorption by means of speedreduction is computed in the same way as for linear holding, only now taking the slightlylonger path into consideration. A graphical representation of all three detour routes aredepicted in Figure 5-6.

Figure 5-6: Map of Jever sectors with detour routes marked in blue [Skyvector, 2015]


5-4 Fuel Consumption Estimation 37

5-3-4 Turtling

Turtling was defined as a combination of speed reduction, altitude reduction and detouring.Because a detour is required, only the three routes (DEGUL-EEL, ABANO-EEL and TUSKA-EEL) that were found to have realistic detouring options can be considered for turtling.Additionally, as it is a combination of detouring and dropping, it was decided to work with astandard flight level reduction of 2000 ft.

Yet again, the way in which the required speed reduction is computed is the same as it is fordropping, the only difference being the elongated path length that is used in the calculations.

5-4 Fuel Consumption Estimation

The feasibility of implementation of en route delay absorption depends to a great extend onthe willingness of airlines to cooperate in new procedures. As fuel cost is one of the maincost drivers in airlines, it will be crucial to them to know what the effects of en route delayabsorption are on their fuel bill.

To estimate the amount of fuel that will be consumed through each of the scenarios, Euro-control’s Base of Aircraft Data (BADA) is used. This model describes the performance ofa large selection of civil aircraft. Implementation and validation of the BADA performancemodel into BlueSky has largely been the work of Isabel Metz, who also wrote in more detailabout the implementation of fuel consumption estimations from this performance model inher thesis. [Isabel C. Metz, 2015] It is important to know what situations are and are nottaken into consideration while establishing the fuel consumption, especially with regards tothe various manoeuvres that will be performed to enhance delay absorption. The computa-tion of the fuel flow is, with only two equations, fairly simple. Let’s have a look at how thefuel flow is obtained for the relevant flight phases. [Eurocontrol, 2013]

First, the TAS [knts] must be known to compute the thrust specific fuel consumption (µ[ kg(min·kN) ]) through Equation 5-4:

µ = Cf1 · (1 +VT AS

Cf2) (5-4)

Cf1 and Cf2 are dimensionless coefficients that are provided by the aircraft manufacturers,VT AS is an input that comes from the simulator. To obtain the nominal fuel flow [kg/min],the thrust specific fuel consumption should be inserted in Equation 5-5:

fcruise = µ · T (5-5)

Here, T is the thrust provided by the aircraft [kN]. The nominal fuel flow, however, is notvalid through idle descent and cruise. For the cruise phase Equation 5-6 should be used:

fcruise = µ · T · Cfcr (5-6)

Again, there is a dimensionless factor provided by the aircraft manufacturers: the cruise fuelflow factor Cfcr. If no data is available on this factor, a value of 1 is assumed. As can be seen,



this factor is also the only thing that differentiates the cruise fuel flow computation from thenominal fuel flow.

During an idle thrust descent the fuel flow is at a minimum, and dependent on Hp, thegeopotential pressure altitude [ft], which can be seen from Equation 5-7.

fmin = Cf3 · (1 − Hp

Cf4) (5-7)

Turboprop and piston type engines are also covered, but are less common in current civiltraffic, which is why they will not be discussed here. For more details on the differencesbetween fuel flow calculations of jet and turboprop engines, please refer to Eurocontrol’sBADA Manual. [Eurocontrol, 2013]

5-5 Workload Estimation Model

Good estimations of en route controller workload are hard to come by. Because of vary-ing route structures, sector dimensions and traffic patterns, each sectors will have differentcharacteristics that would best represent workload. For ANSPs it is important to have an indi-cation of the expected workload, as it helps to pre-determine when which sector configurationis needed, and how much staff would be required for that particular airspace configuration.

To get an indication of workload and airspace capacity, a large range of complexity metricshas been developed by many different parties. These metrics should indicate how easy ordifficult it is to handle a certain traffic situation. Some of the most well known metrics areNASA’s Dynamic Density metrics, and Eurocontrol’s ATC Capacity Analyser tool (CAPAN)metric. [I.V. Laudeman, S.G. Shielden, R. Branstrom, and C.L. Brasil, 1998] [EurocontrolExperimental Centre, 2003] CAPAN interprets the intensity of the workload based on thepercentage of an hour that is spent on control tasks, as shown in Table 5-2.

Table 5-2: Interpretation of hourly workload using CAPAN [Eurocontrol Experimental Centre,2003]

Threshold Recorded Hourly Working Time Interpretation

0 - 17 % 0 - 10 minutes Very light load18 - 29 % 11 - 17 minutes Light load30 - 53 % 18 - 31 minutes Medium load54 - 69 % 32 - 41 minutes Heavy load

70 % or above 42 minutes + Overload

Because this research investigates the feasibility of en route delay absorption, an estimationof controller workload is needed to check if the delay absorption measures do not result intoo much additional work.

Controller workload can typically be broken down into two types of workload: mental andcommunication workload. The mental workload is the amount of time a controller spendsto resolve (potential) conflicts, generate a mental picture of the traffic situation and decidewhich commands need to be given. The communication workload is the amount of time acontrol spends on communicating the commands to the pilots.


5-5 Workload Estimation Model 39

Because traffic within MUAC typically travels at high speeds, the time spent within a sector(especially when the airspace is subdivided into many different sectors during busy times) isvery short. This leaves little room for ‘strategic’ flight planning, and results in a relatively highcommunications workload rather than a high mental workload. Because of this predominanceof communications workload, the classic complexity metrics tend not to represent the workloadof en route controllers well (not even Eurocontrol’s own CAPAN metric). This is why furtherresearch has been performed at Eurocontrol into how controllers spend their time. Reportson this research have been used as a basis to develop a simplified workload model to estimatecontrol workload within this thesis research. [R. Ehrmanntraut and I. Sitova, 2013]

In Figure 5-7 the ten most often used controller inputs for all MUAC airspace are given.This figure is based on the number of clicks used in the system for each command. It is veryapparent that the majority of the workload is caused by a minority of the available commands.An explanation of the meaning of each of the commands stated in Figure 5-7 can be foundin Table 5-3. Although according to Figure 5-7 speed commands are not typically given,this command is crucial for en route delay absorption. Hence the communication workloadassociated to this command has also been stated in Table 5-3.

Figure 5-7: MUAC SEC input per 100 flights per weekday [R. Ehrmanntraut and I. Sitova, 2013]

As is apparent from Table 5-3, the ‘Delegate’ and ‘ECL’ commands are done by the planners,not by Senior Executive Control (SEC). A control station is usually occupied by a plan-ner and an executive controller. The planner supports the executive controller in the moreadministrative tasks, the executive controller is the one directly in contact with the air traffic.

For the workload analysis, only the communications workload of the SEC will be taken intoaccount. In Table 5-4 the rules that are used to establish this workload can be found. It maybe surprising to see only five out of ten of the most commonly used commands being reflectedin the communications workload metric.

The most common, unconsidered command is the ‘Direct Input’. This command is given



Table 5-3: Communication workload in seconds per command [R. Ehrmanntraut and I. Sitova,2013]

Command Purpose Estimated DifficultyWorkload [s] [1-6:low-high]

XASM To counter-assume/transfer controlover a flight

10 2

ASM To assume/accept a flight 10 2

CFL To set a cleared flight level 8 2-6

Graphical RouteModifications(GRM)

To graphically modify the route of aflight

8 3-5

To resolve a conflict 10 4

Direct To proceed direct to a point on thetrajectory

8 2-5

MTCD To create/delete a manual conflict 3 2

Heading To set a heading input 8 4-6

XLeg To cancel a segment leg 1 1

ECL To change the entry flight level forthe sectorTo change the expected time overthe entrycoordination point 6 (Planner) 4

Delegate To skip OPS sector in the executivecontrol list, replacing it by the up-stream OPS sector

- (Planner) -

Speed To change the speed of a flight 8 4

when an ATCo clears a flight to fly directly to a certain waypoint, rather than following theoriginally planned route. It is a very effective way to reduce the time a flight spends withina sector. It does, however, require an ATCo’s experience to decide whether a flight can begranted a direct or not. Because this knowledge and insight is not readily available during thesimulations, and it can not (yet) be realistically implemented in a simulated environment, itis impossible to include the effects of ‘directs’. Similar reasons apply to the XLeg and speedcommands, which are both dependent on the ATCo’s insight as well.

An MTCD command is not a command that is given to a flight, but an operation an ATCocan perform on his/her radar screen to see the predicted trajectories of several manuallyselected flights, and if these flights will be in conflict with each other in the foreseeable future.As this does not concern a true communications operation, it will not be considered in theworkload.

The ECL and Delegate commands are typically processed by the planner position, and thusnot directly contribute to the executive controller’s workload. This, together with it beingvery difficult to obtain realistic values for these measures in a simulated environment, makesthat neither of the commands will be reflected in the workload.

For flights subject to en route delay absorption, some additional rules will apply. These rules


5-5 Workload Estimation Model 41

can be found in Table 5-5 and are based on the workload intensity as stated in Table 5-3.

Table 5-4: Rules to establish communication workload within MUAC airspace

Command Rule

XASM Each flight leaving relevant MUAC airspace results in a penalty of 10 seconds

ASM Each flight entering relevant MUAC airspace results in a penalty of 10 sec-onds

CFL If the difference between entry and exit flight level is larger than 2000ft apenalty of 8 seconds will be applied

GRM Each unique conflict occurring within MUAC airspace will result in a penaltyof 8 seconds

Heading If the heading difference between the minimum and maximum heading of aflight is larger than 5 degrees, a penalty of 8 seconds will be applied

Table 5-5: Additional rules to establish workload within MUAC airspace resulting from en routedelay absorption measures

Command Rule

Linear holding If an EHAM inbound flight is under the influence of linear holding, anadditional penalty of 8 seconds will be applied upon entry of the MUACairspace.

Dropping If an EHAM inbound flight is under the influence of dropping, an ad-ditional penalty of 16 seconds will be applied upon entry of the MUACairspace.

Detouring If an EHAM inbound flight is under the influence of detouring, an ad-ditional penalty of 24 seconds will be applied upon entry of the MUACairspace.

Turtling If an EHAM inbound flight is under the influence of turtling, an additionalpenalty of 32 seconds will be applied upon entry of the MUAC airspace.


Chapter 6

Simulation Scenarios

In order to get results out, naturally, some input has to be fed into the simulation. Severaloptions are possible: scenarios can be handmade, deduced from actual flight data or fromflight plans. Because of the large amount of variables

6-1 Eurocontrol DDR2

The Eurocontrol Demand Data Repository 2 is an online database in which all historical andforecasted flight data of flights to and from Europe are stored. The traffic samples in theDDR2 also make use of the airlines flight intentions, airport capacity thresholds, and theairspace structure (sectors and routings). All this information is collected and stored in oneplace to facilitate the downloading and analysis of historical and forecasted traffic by (other)ANSPs. Alongside the DDR2, Eurocontrol also provides free analysis tools in the form ofSystem for traffic Assignment and Analysis at a Macroscopic level (SAAM) and NetworkStrategic Tool (NEST), the latter being the most advanced tool of the two. Capabilities ofNEST vary from sector counts and airport demand to workload and cost estimations.

Eurocontrol provides the historical data in three different formats: .exp2, .so6, and ALL FL+.The .exp2-format contains only the planned airport pair (origin and destination) for eachflight. The other two formats are equipped with 4D trajectories, the only difference betweenthe two being that the ALL FL+-format is provided with additional information of sectorcrossings. Within the .so6-format a difference can be noted between the model1 (m1) andmodel3 (m3) versions. Here, the difference is that the m3-files are updated with actual radardata, and will thus more accurately represent the actual flown trajectory than the m1-files,which only contain the flight plan data. [Eurocontrol, 2014a]

When taking a closer look at the flight count within each of the formats, it can be foundthat the .exp2-files may contain more flights than the other two formats. This is due to theway the 4D trajectories are created. In 85% of the flights, the flight plans are ‘stuffed’ byhistorical trajectories, while around 10% can not obtain enough data for a full 4D trajectory,and is thus completed by using the cheapest or shortest routes consering the latest applicable


44 Simulation Scenarios

airspace structure. For the remaining 5% of flights it is not possible to create a completetrajectory, which is why those flights are discarded from the .so6 and the .ALL FT+-format.

It may seem tempting to go for the most accurate trajectories, however, there is a importantdisadvantage to the m1-format: it may contain direct routings. Although this would bea better representation of the actual traffic, it does make it very difficult to find uniformand consistent routing. For linear holding and dropping this would not cause any problems,however, for detouring and turtling it would be difficult to implement suitable reroutings, aseach flight may have a different trajectory. This was ultimately also the reason to proceedwith the .so6 model3 file format, and not with the .so6 model1 or the ALL FL+-format.

6-2 Data Selection

It has already been mentioned in Chapter 3 that this thesis aims to explore a variety ofdifferent traffic patterns and densities. To facilitate this in the scenarios, two full days ofdata have been selected: one in the low season (February 4, 2015) and one in the high season(August 6, 2014). EHAM facilitated 539 arrivals on the selected date in February 2015, and699 arrivals on the sixth of August 2014.

To see how the selected dates compare to the average ‘real’ situation, plots have been made ofthe distribution of the inbounds and the amount of FIR delay. Figures 6-1 and 6-2 show thatthe general trend of inbound peaks seem to match quite well, and thus it can be concludedthat the selected dates are representative of the arrival pattern at Schiphol airport.

The graphs depicting the average delay per hour of day (Figure 6-3 and 6-4) show somesignificant differences between the distribution of the delays in the selected days in Februaryand August. With almost 50% more traffic during the selected high season date, it is nosurprise that the observed average delay per hour on August 6, 2014 far exceeds the averagehourly delays on February 4, 2015. The delay peaks for the August date can be explained bythe excessive number of inbound flights around 13.00 and 17.00 EHAM LT, and the possiblebulkiness in the original .so6-file. Off-peak, the selected days match the findings from theNLR research results depicted in Figure 6-3 rather well. Having higher peaks does not makemuch difference for the simulation, as there is a threshold at the maximum delay absorptionper absorption tactic, anyway.


6-2 Data Selection 45

Figure 6-1: Distribution of 2013 EHAM inbounds per hour of day [Schiphol Amsterdam Airport,2014]

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23Planned Arrival Time at EHAM [LT]

0

10

20

30

40

50

60

70

80

Num

ber of Arriv

als [-]

EHAM Arrival Pattern

04-02-201506-08-2014

Figure 6-2: Distribution of EHAM arrivals


46 Simulation Scenarios

Figure 6-3: Average FIR delay per inbound EHAM flight [NLR, 2013]

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23Time of Day at EHAM [LT]

0

5

10

15

20

25

Average FIR Delay [minutes]

EHAM Delay Pattern

04-02-201506-08-2014

Figure 6-4: Distribution of EHAM FIR Delay


Chapter 7

Results

The outcomes of the simulation runs are presented and explained in this chapter, with thegoal to provide all data required to answer the research questions. First, the results of theoptimal delay absorption calculations are provided to set up the boundaries of what is feasiblewith the four delay absorption measures. This is followed by an evaluation of the effects ofdelay absorption on the fuel consumption. Moving towards the effects on the ATCos, thechange in number of conflicts and communication workload will be examined next, afterwhich the chapter will be concluded by a sensitivity analysis of the simulation variables. Theinterpretation of the data in light of the research questions can be found in Chapter 8.

7-1 Maximum Delay Absorption

First, let’s have a look at the maximum amount of delay that can be absorbed through thefour tactics. Since all routes are of different length, the absolute maximum delay absorptionis taken per NM, to take out the effect distance has on the total amount of delay that canbe absorbed. Table 7-1 shows the maximum, median and average delay absorption per NM,based on a total sample size of 426 flights (all affected flights from the sample date in August2014 and February 2015).

These values have been computed by determining the distance between waypoints given inthe flight plan, and the speed at which it is planned to be flown. From this the time requiredfor each segment is determined. Also, the MRC is calculated for each segment, based on thealtitude and aircraft type. This MRC is then used to determine how long it would maximallytake to cover the segment. The difference between these two times is added for all segmentswithin MUAC airspace, ultimately resulting in the maximum delay absorption value. Thechanges in speed are assumed to be instantaneous, hence the time required to reach the MRCis not taken into account in this figure.

Since detouring and turtling can be regarded as variations to linear holding and dropping,only on a longer trajectory, the amount of delay absorbed per NM does not significantly varyfrom the values found for linear holding and dropping. However, since the route itself has


48 Results

Table 7-1: Optimum delay absorption within MUAC airspace

Minimum Maximum Average MedianMeasure [s/NM] [s/NM] [s/NM] [s/NM]

Linear Holding 0.01 2.4 0.4 0.2Dropping 0.02 3.7 1.1 0.9

been extended, it will inherently take longer for the flight to complete its trajectory throughMUAC airspace, even if no further speed reductions are issued. Over the three routes thatare up for detouring/turtling, the same average delay absorption per NM was found, being 8seconds per additionally flown NM. This number is equivalent to a speed of around 0.8M/450kts TAS/240 kts EAS.

This data is theoretical, and merely stipulates what would be possible in optimal situations.Dropping here shows a potential of being almost three times as effective a means of delayabsorption than linear holding. However, this result is skewed, due to the assumption that aflight will instantly take on the required reduced speed, rather than allowing for the aircraftto slow down gradually.

For linear holding these effects can be assumed to be negligible because the speed reductionsare small and thus the deceleration will not take long. Unfortunately, it is a different storyfor dropping flights. When lowering the flight level, potential energy is converted into kineticenergy, which results in an acceleration rather than the desired deceleration. The gap betweenthe actual speed and the desired speed becomes bigger, resulting in a longer timespan beingrequired to reach the lower speed.

With the data obtained during the simulations, it was found that even though it is possibleto slow down a descending aircraft, it will not be as effective as computed in the theoreticalresults displayed in Table 7-1. Rather than being on average a factor 2.8 more effective,dropping was found to be ‘only’ 1.7 times more effective than linear holding.

7-2 Fuel Consumption

To assess the difference in fuel consumption due to delay absorption, all tactics have beenevaluated separately. For each tactic, the average fuel flow is computed by dividing the totalfuel consumption within MUAC airspace of all delayed flights and dividing it by the amountof time these flights have spent within the airspace. Please note that this only considers thedifference in fuel consumption within the MUAC airspace, the effects of flying at lower speedswithin the LVNL airspace is thus not taken into account in these figures.

In Table 7-2, a second dry run (Dry2) is introduced. In this run only the flights that areeligible for detouring/turtling are evaluated. These flights are on trajectories with longercruise phases within MUAC airspace than flights coming in from i.e. the Brussels sector, andwill thus, on average, have a higher fuel flow. Comparing the fuel efficiency of detouring andturtling with the general averages would not be fair.

[Additional fuel savings may be due to consequent deceleration, where in the flight planchanges in speed constantly occur]


7-2 Fuel Consumption 49

Table 7-2: Average fuel flow during different delay absorption tactics

Total February August

Dry 0.801 0.746 0.832Linear holding 0.786 (-1.9%) 0.733 (-1.7%) 0.816 (-1.9%)

Dropping 0.428 (-46.6%) 0.370 (-50.4%) 0.461 (-44.6%)

Dry2 1.047 - -Detouring 1.048 (+0.1%) - -

Turtling 0.520 (-50.3%) - -

The total fuel consumption of all flights together has also been noted. With 0.1% totalfuel savings, the effects of linear holding on the total fuel consumption is marginal. Droppingperforms far better with fuel savings of 45% with respect to the total fuel consumption duringthe dry run, but is still outperformed by turtling (-50%). Detouring performs worse than thedry run, with an additional 5.1% fuel burned.

As a rule of thumb, generally a fuel flow of 1 kg/s is used. It is clear that, even during thedry run, the found average fuel flow is lower than this value of 1 kg/s. This difference can beexplained by the presence of descent segments in all trajectories. During descent, the aircraftcan throttle back to idle thrust, resulting in lower average fuel flow figures. This explanationis supported by the dry run data from the detouring and turtling scenarios. With the longertrajectories these flights are on, the ratio cruise/descent is bigger than that of the EHAMinbounds with a short MUAC trajectory, which results in a higher average fuel flow.

Figure 7-1 shows fuel consumption in relation to altitude, and is included to reference howfuel consumption during en route delay absorption compares to that of delays induced in thelower airspace. From this graph it can be seen that fuel consumption increases significantlyat lower altitudes. Although the fuel consumption is lower across the entire range in terms offuel used per second. Especially at the higher altitudes it can be seen that the graphs for theM0.6 and M0.8 operating speeds start to converge (the M0.4 is not considered for the higheraltitudes, as it is impossible for an aircraft to fly at this speed at these altitudes). Althoughper second an aircraft may use less fuel flying at M0.6, if looked at per unit distance it willbe more fuel efficient to fly at M0.8.

What is interesting about this graph is that the fuel consumption while flying at M0.4 at lowaltitudes is the same or even lower, as flying at M0.8 at high altitudes. From this it can beconcluded that there is no significant additional fuel saving due to delay absorption in theupper airspace instead of in the lower airspace.

7-2-1 Linear Holding

The total reduction of fuel consumption of 0.1% during linear holding with respect to the dryrun seems like a small but plausible value. Literature refers to airlines generally operating aspeed regime somewhere between the MRC and Long Range Cruise Speed (LRC), the latterbeing the speed at which operations are 1% less fuel efficient than operations at the MRC.

The slight discrepancy between the fuel flow reduction of around 2% and total fuel savings of0.1% can be explained by the additional time spent within the MUAC airspace. Although the


50 Results

10000 15000 20000 25000 30000 35000 40000Altitude [ft]

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Fuel consumption [kg/s]

Fuel consumption vs altitude

M0.4M0.6M0.8

Wide-bodyNarrow-bodyWide-bodyNarrow-body

Figure 7-1: Comparison of fuel consumption at various speeds and altitudes

reduced fuel flow means an aircraft is flying slightly more efficiently, the lowered speed resultsin the aircraft being in the air longer. Depending on how long the trajectory within MUACis, and how much more fuel efficient a flight is, the net fuel consumption will be positiveor negative compared to the original dry scenario. The resulting ‘break-even’ point in fuelconsumption can be described with Equation 7-1:

mnormal · tnormal = mdelay · (tnormal + tdelay) (7-1)

Where m presents the fuel flow in kg/s, and tnormal is the time within the MUAC airspacein seconds. This relation can be transformed to a relationship between ratios, as stated inEquation 7-2:

tnormal + tdelay

tnormal

=mnormal

mdelay

(7-2)

7-2-2 Dropping

From Table 7-2 it can be seen that the average fuel flow is reduced by more than half whendropping. Because such a dramatic reduction in fuel consumption was not anticipated, Fig-ure 7-2 has been drawn up to illustrate where this difference finds its origin.

Figure 7-2 shows the altitude, speed and fuel flow throughout time. The graph has beenobtained by simulating a short sample flight that performs an ‘untouched’ part of the scenario,


7-2 Fuel Consumption 51

followed by a linear holding segment, and finalised by a dropping segment. At the verticallines at t=20 and t=80, the flight switches from its normal operation to linear holding mode,and from linear holding to dropping mode, respectively.

It can be seen that as soon as the aircraft starts to descent, the fuel flow reduces to the valueequivalent to idle thrust. Also, the speed starts to increase due to potential energy beingconverted to kinetic energy. After reaching the 2000 ft lower flight level, a small spike in fuelflow occurs, likely due to the switch from idle mode back to cruise mode. Following this spikethe fuel consumption decreases again, as the aircraft slows down similarly to it did duringlinear holding mode. The overall result is the flight ending up at a fuel flow that is almostthe same as the fuel flow at the higher flight level, but at a lower speed. Because there is nosignificant change in fuel flow after the flight level change, the idle thrust portion has such asignificant effect on the total fuel consumption.

33000

34000

35000

36000

37000

Altitude [ft]

Fuel flow vs speed and altitude for different delay absorption measures

0.0

0.5

1.0

1.5

2.0

2.5

Fuel flow [kg/s]

0 50 100 150 200Time [s]

0.74

0.75

0.76

0.77

0.78

0.79

0.80

0.81

Speed [M]

Figure 7-2: Comparison of fuel flow during normal scenario, linear holding and dropping

7-2-3 Detouring & Turtling

For both detouring and turtling it should be noted that very few flights were eligible to bedelayed using either of these methods. Although trends may be identified, care must betaken not to jump to conclusions based on these figures alone. Because the limited amountof available data, no difference is made between the data from February and August.

The total fuel consumption during the dry runs was 8967 kg, while during detouring thishad increased to a value of 9421 kg, and during turtling decreased to 4209 kg. An incrementof about 5% for detouring seems rather substantial, but is not inexplicable. For the routes


52 Results

that were selected for detouring, the original trajectories had lengths of around 120-130 NM.Taking into account that around half of this trajectory is used for descent during which theaircraft will operate on idle thrust, the cruise path extension will be somewhere around 5%.

The reduction in fuel consumption found for turtling is in line with the savings found fordropping flights. Again, the explanation to the strongly reduced fuel flow can be found in theearlier initiation of the descent.

7-3 Conflicts

The number of conflicts per hour within the MUAC airspace under normal circumstancesand with linear holding and dropping included have been included in Appendix D. The totalscan be found in Table 7-3. Rather than an increase in conflicts, the low season day shows anoverall decrease in conflicts. This is not the case for August, which shows an overall increasein the number of conflicts. It is impossible to trace back exactly why in some scenarios moreconflicts occur and in others less, as it depends on the amount of traffic that is present, theirtrajectories and speeds.

Interestingly, the detouring and turtling scenarios show very strong conflict reductions. Thiscan be explained by ‘clusters’ of conflicts that sometimes occur. In this situation, one aircraftis involved in several conflicts simultaneously. Merely reducing the speed or dropping flightlevels might not be enough to resolve these clusters, but a change in trajectory can be. Becauseof the carefully selected detouring options, potential conflicts with traffic on other routes havebeen eliminated as much as possible, resulting in an overall decline in conflicts.

Table 7-3: Total conflicts within MUAC airspace

Total Jever Brussels Hannover

February Dry 2718 450 1556 712Linear holding 2684 (-1.1%) 416 (-7.6%) 1559 (+0.2%) 709 (-0.4%)

Dropping 2702 (-0.4%) 421 (-6.4%) 1569 (+0.8%) 712 (0%)

Dry2 401 401Detouring 384 (-4.2%) 384 (-4.2%)

Turtling 385 (-4.0%) 385 (-4.0%)

August Dry 5534 633 3723 1178Linear holding 5573 (+0.7%) 661 (+4.4%) 3828 (+2.8%) 1084 (-8.0%)

Dropping 5572 (+0.7%) 659 (+4.1%) 3805 (+2.2%) 1101 (-5.9%)

Dry2 452 452Detouring 407 (-10.0%) 407 (-10.0%)

Turtling 408 (-9.7%) 408 (-9.7%)

7-4 Communication Workload

This section is intended to give some insight in the development of additional workload dueto delay absorption. Analyses done here are meant to give an indication of how the generalperformance of the different delay absorption measures is with respect to workload. To


7-4 Communication Workload 53

enhance the readability of the report, and to avoid repetition, only the workload distributionand change in workload for the Brussels sector in February will be elaborately discussed inthis section. The other graphs of the communication workload distribution for the differentsectors during the two test days, as well as the change in communication workload across theday, can be found in Appendix C.

Table 7-4: Average communication workload per sector [seconds per hour]

Measure Total Jever Brussels Hannover

February Dry 6038 1315 2948 1775Linear holding 6063 (+0.4%) 1300 (-1.1%) 2969 (+0.7%) 1794 (+1.1%)

Dropping 6101 (+1.0%) 1307 (-0.6%) 2986 (+1.3%) 1808 (+1.9%)

Dry2 1094 1094 - -Detouring 1087 (-0.6%) 1087 (-0.6%) - -

Turtling 1087 (-0.6%) 1087 (-0.6%) - -

August Dry 8641 1498 4988 2155Linear holding 8750 (+1.3%) 1512 (+0.9%) 5079 (+1.8%) 2159 (+0.2%)

Dropping 8799 (+1.8%) 1525 (+1.8%) 5086 (+2.0%) 2188 (+1.5%)

Dry2 1191 1191 - -Detouring 1158 (-2.8%) 1158 (-2.8%) - -

Turtling 1156 (-2.9%) 1156 (-2.9%) - -

Table 7-4 shows the average communications workload per hour per sector, as computedusing the rules set in Section 5-5. These averages show how in almost all scenarios a highercommunications workload is registered than during the dry runs. Except for the Jever sectorfor all February scenarios, and the Jever detouring and turtling scenarios in August. Thiscan be related to the observed reduction in conflicts in the Jever sector for these scenarios,as shown in Table 7-3.

7-4-1 Linear Holding & Dropping

From Figure 7-3 it can be observed that across the day, the workload graphs stay rather closetogether, never deviating much. To make it easier to observe differences between the workloadduring the dry run and the linear holding and dropping runs, the change in communicationworkload has been depicted in Figure 7-4. Here it can be seen that the behaviour is rathererratic, the workload sometimes being lower than the dry run, at other times being higher.

First, observe how during the first and last hours of the day, no changes in workload arenoted. This was to be expected, as there is hardly any traffic during these hours, and thusalso no delay to be absorbed by the en route airspace. The first trough seems to be ratherbig for the time of day. However, putting this in perspective with Figure C-5, it can be seenthat the workload around the first trough is around 500 seconds per hour, so a change of 2%is the equivalent of 10 seconds work.

In that regard the workload changes between 6AM and 8PM are more interesting, as theaverage workload is a lot higher at around 4000 seconds per hour. Looking a bit closer to thefirst peak, it can be seen that it occurs at 7AM, during the morning inbound rush. Delayswere found to be substantial around this time of day, as can be seen in Figure 6-4. Focussing


54 Results

0 5 10 15 20Time of day [EHAM LT]

0

1000

2000

3000

4000

5000

6000

Communications workload [s/h]

Communications workload - Brussels sector - 04-02-2015

DryLinear HoldingDropping

Figure 7-3: Communications workload - Brussels sectors - February


−2

−1

0

1

2

3

4

5

6

Change in w

ork

load [

%]

Change in communications workload relative to dry run - Brussels sector - 04-02-2015

Linear HoldingDropping

Figure 7-4: Relative change in communications workload - Brussels sectors - February



on what happens during the remainder of the day, it can be seen that at times the graphs forlinear holding and dropping are almost identical. The dropping scenario consists not only ofdropping flights, but also of flights that are put under linear holding. If possible, the leastinvasive method is used for delay absorption. If the changes in workload graphs are (almost)identical, this means that during this hour the operations in the linear holding scenario andthe dropping scenario were (almost) identical as well.

At times also large differences between the change in workload can be seen between linearholding and dropping. These differences can have two origins: either during that hour moredropping operations were performed (which are penalised with 16 seconds additional work-load, compared to 8 seconds for linear holding), or because more or less conflicts with othertraffic have been resolved or created because of the delay absorption. For the spike aroundnoon, this can be explained by the latter of the two. In Figure D-1 it can be seen how linearholding experiences less conflicts, while dropping experiences more conflicts. Typically, twotypes of conflicts can be distinguished: conflicts with traffic on the same route, and conflictswith traffic on other routes travelling in other directions. Unfortunately, it is not possible tocompletely trace back which of the two types of conflict has been resolved or caused by thedelayed flights.

Because the other graphs depicted in Appendix C show similar trends as the one discussedhere, no in depth review of all graphs will be performed here. Rather, the Pearson andSpearman correlations will be interpreted sector by sector. But a first overall notion is thatit is striking that the values across the tables do not differ much, implying that are aboutequally monotonic as they are linear.

First, Jever should be considered. With negative correlations across the board for linearholding and dropping, it is the only sector showing negative correlation. This can be explainedby the reduction in workload, rather than the expected increase in workload. The reductionin workload only shows medium negative correlation during linear holding on the low seasonday, all other values indicate there is no correlation between the expected workload and theactual change in workload.

Brussels and Hannover, however, seem to be more susceptible to the correlations, especially onthe test day in February. On this day both sectors show high to very high positive correlationsfor both Pearson and Spearman correlations. This seems logical, as the number of conflictson this day has remained almost the same for these sectors, and the additional workload dueto delay absorption has thus not been significantly reduced by a change in conflicts.

The change in number of conflicts would also explain the lower correlation for both sectorson the high season day. Brussels still manages to obtain a medium positive correlation, butonly a medium correlation for dropping in Hannover was found.

7-4-2 Detouring & Turtling

Before diving into some observations concerning the communications workload during detour-ing and turtling in the Jever sector, it is important to explain why the original dry run couldnot be used as reference for the detouring and turtling scenarios.

Because only three routes were found fit for detouring operations, and all these routes laywithin the Jever sectors, it was decided to crop the scenarios to only contain flights flying


56 Results

through the Jever sector. This decreases the time required to complete a simulation, andcuts out irrelevant data. However, the workload was found to be significantly lower for thesescenarios. The explanation why this is the case is twofold.

Firstly, the way in which the scenarios are created requires flights to have at least one waypointwithin the airspace that is under investigation. Flights that fly through the Jever sector donot necessarily have their routes planned through a waypoint within Jever. As a result, theseflights will not be incorporated in the final scenario, as no route can be made up for theseflights. This reduces the amount of traffic and also the workload, as less flights have to beaccepted and transferred from/to other ANSPs.

Secondly, flights are initiated at the last waypoint before entry of the investigated airspace,in this case the Jever sectors. In the original dry run, aircraft may have flown through theHannover, or even the Brussels sectors before reaching Jever. Although the flight plans areliterally translated into scenarios, the simulation of the scenarios in BlueSky takes the aircraftperformance into account, which can result in small differences between the flight plan and thescenario. Flights may enter the Jever sectors later than they would have done in the originaldry run. The difference this causes is expected to be in the range of seconds, which doesnot seem to invasive. However, because the workload is calculated per hour, a few secondscould shift a flight from one hour to the other, which may contaminate the results. This,together with the first reason, is why additional dry runs were performed for the detouringand turtling scenarios.

Rather against the original expectations, the average workload was found to be reduced,albeit marginally compared to the number of conflicts that have been resolved because ofthe delay absorption. The correlations presented in Tables 7-5 and 7-6 show no significantcorrelation for detouring and turtling in August. For the February scenario, only mediumpositive correlation was found.

7-4-3 Communication Workload Forecasting

In order to assess the predictability of additional workload, correlation between the numberof delay absorption measures per hour and the change in workload per hour was investigatedusing both Pearson’s (Table 7-5) and Spearman’s methods (Table 7-6). Pearson’s methodis meant to investigate linear correlation, where Spearman’s method is intended to discovermonotonic relations.

Both methods have the same interpretation scale. Correlations can range between -1 and1, where -1 means a very strong negative correlation, and 1 indicates a very strong positivecorrelation. Values between 0 and 0.3 mean there is no or a very low correlation, between 0.3and 0.5 there is a low correlation, 0.5 to 0.7 means there is a medium correlation, 0.7 to 0.9indicates a high correlation, and finally any correlation between 0.9 and 1 indicates a veryhigh correlation. Of course these thresholds apply to both the positive and negative side ofzero. All medium to very high correlations in Tables 7-5 through 7-8 are put in italics tomake it easier to set them apart.

From Tables 7-5 and 7-6 it can be seen that the Brussels and Hannover sectors show highpositive correlations for the low season day, and medium to high positive correlations forthe high season day. However, the Jever sector shows low negative correlation for almost all



scenarios. It can be concluded from these values that for the Brussels and Hannover sector,the expected change in communication workload can be regarded as a reasonable predictionof the actual change in workload, but for the Jever sector this metric will not suffice.

Table 7-5: Pearson correlation between expected and actual change in workload


February Linear holding 0.703 -0.620 0.741 0.805

Dropping 0.873 -0.095 0.815 0.904

Detouring 0.345 0.345Turtling 0.528 0.528

August Linear holding 0.403 -0.083 0.477 0.187Dropping 0.506 -0.063 0.513 0.6

Detouring -0.153 -0.153Turtling -0.215 -0.215

Table 7-6: Spearman correlation between expected and actual change in workload


February Linear holding 0.478 -0.376 0.722 0.810

Dropping 0.736 -0.039 0.649 0.881

Detouring 0.207 0.207Turtling 0.325 0.325

August Linear holding 0.387 -0.362 0.529 0.234Dropping 0.572 -0.103 0.711 0.629

Detouring -0.159 -0.159Turtling -0.147 -0.147

In addition to the correlation between the observed additional workload and expected ad-ditional workload, the correlation between observed additional workload and traffic densityhas been investigated as well. This again with the hopes of finding a means to predict howthe workload will be affected by the delay absorption measures. Similar to the previouscorrelation analysis, the Pearson and Spearman correlations have been used.

As can be seen from Tables 7-7 and 7-8, the most significant positive correlations were foundfor the Brussels sector in February and to a lesser extent in August as well. For this sector thecorrelations are medium positive at best. The Jever sector and Hannover sector consistentlyshow no to very low correlation, and thus neither the expected workload nor the traffic densityseem to be suitable to use as a means to predict the change in communications workload.


58 Results

Table 7-7: Pearson correlation between workload change and average hourly traffic density

Measure Jever Brussels Hannover

February Linear holding -0.182 0.382 0.196Dropping -0.069 0.330 0.249

Detouring -0.287Turtling -0.270

August Linear holding 0.252 0.337 0.151Dropping 0.228 0.192 0.296


Table 7-8: Spearman correlation between workload change and average hourly traffic density

Measure Jever Brussels Hannover

February Linear holding -0.283 0.563 -0.008Dropping -0.301 0.500 0.086


August Linear holding -0.019 0.393 0.166Dropping -0.120 0.204 0.312


7-5 Sensitivity Analysis

There are a number of simulation variables on which assumptions have been made. Tounderstand the full effect of these assumptions, a sensitivity analysis has been performed toget an indication of how delay absorption and fuel consumption vary with these parameters.Due to time constraints, it was decided not to further explore a possible relation betweenaircraft type and delay absorption capabilities.

All graphs containing information on narrow body and wide body performance are based onthe averages of five different aircraft types for each category, and are meant to give a generalindication of performance. Averages are taken in order to work around the confidentiality ofdata in the BADA.

7-5-1 Mass

The aircraft influences both fuel consumption and the maximum range cruise speed. Duringthe simulation the weight has been taken as the reference weight as given in the BADA, whichis roughly around 70% between the minimum and maximum mass defined in the BADA. InFigure 7-5 the MRC has been plotted against the (reference) mass factor. A factor of 1.0means the mass is equal to the reference mass. Assuming the maximum weight to be twotimes the minimum weight, a mass factor of 0.6 is the equivalent of around 1.2 (≅ 1.7 · 0.6)times the minimum mass of the aircraft, and a factor of 1.2 is the equivalent of around 2.0(≅ 1.7 · 1.2).


7-5 Sensitivity Analysis 59

0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3Reference mass factor [-]

350

400

450

500

550

600Maximum range cruise speed [Knts TAS]

Narrow bodyWide body

Figure 7-5: Maximum range cruise speed at FL380 vs. Reference mass factor

From Figure 7-5 it is irrefutable that the higher the mass, the higher the MRC. Both graphsbehave similarly (approximately linear), but the narrow bodies have on offset in MRC between7-8% relative to wide bodies. Assuming a linear relation between mass and MRC, an under-or overestimation of 10% results in a difference in MRC of 25 knts TAS, which at an altitudeof 38000ft is the equivalent of around 0.04M.

7-5-2 Airline Intent

Within the two selected days, a selection of flights executed by a ‘traditional’ carrier (KLM)and several Low Cost Carriers (LCCs) (Transavia, EasyJet, HOP) has been made. Thisresulted in a dataset of 189 KLM flights and 41 LCC flights, of which the average maximumdelay absorption capacity was found to be 0.365 s/NM for the legacy carrier, and 0.368 s/NMfor the LCCs. With a difference of less than 1% between these values, it can be concludedthat within the datasets provided by Eurocontrol’s DDR2 no significant difference betweenthe operating practices of the different airlines can be found.

7-5-3 Route

In Section 7-1 the maximum theoretical delay absorption has already been discussed. Adistribution of all the data points (delayed flights) considered there can be found in Figures 7-6and 7-7. In these box plots the amount of potential delay absorption in s/NM is plotted perroute. Since not all routes had sufficient traffic on them to justify a box plot, only the routeswith 20 or more delayed flights are considered.


60 Results

From these graphs it can be seen that there is quite a wide range of values covered for allroutes, and that there does not seem to be a predominant relation between the length ofthe trajectory within MUAC airspace and the delay absorption. However, it is striking howthe routes through the Brussels sector seem to perform so much stronger than the flightscoming in from the other sectors. A possible explanation could be the ratio between cruiseand descent within MUAC airspace. Because for these flights the descent portion is generallylonger than the cruise portion, these routes will ‘naturally’ inherit some of the advantages offurther speed reductions that are possible when flying at a lower altitude, similar to dropping.This idea is supported by comparing the box plots from Figures 7-6 and 7-7. In Figure 7-7it can be seen that the delay absorption in seconds per NM has increased more for the morecruise oriented routes (3-6) than the descent dominated routes (1 and 2).

The outliers can be explained by the use of the performance characteristics of the defaultaircraft type. In absence of BADA performance data for a particular type of aircraft, theperformance data of a default aircraft (B747-400) is used. Using this default aircraft canresult in bigger differences between the current operating speed and the MRC, and thus inbigger maximum delay absorption values.

Brussels2 Brussels4 Hannover2 Hannover4 Hannover5 Jever2Route [-]

0.0

0.5

1.0

1.5

2.0

2.5

Maximum delay absorption [s/NM]

Maximum delay absorption per NM - Linear Holding

Figure 7-6: Linear holding maximum delay absorption per NM vs distance

7-5-4 Weather

Weather has a big effect on the day to day operations of air traffic. Thunderstorms may shutdown big parts of airspace, while head- or tailwind may affect the speed at which aircraft fly.It is difficult to assess the exact effects of wind and bad weather without (simulation) data,which is why only a review of the expected effects is given here.

The effects of thunderstorms will be similar for all airspace: the part of the airspace wherethe thunderstorm is located will be closed. Closing part of the airspace results in traffic


7-5 Sensitivity Analysis 61

Brussels2 Brussels4 Hannover2 Hannover4 Hannover5 Jever2Route [-]

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Maxim

um

dela

y a

bso

rption [s/

NM

]

Maximum delay absorption per NM - Dropping

Figure 7-7: Dropping maximum delay absorption per NM vs distance

flows having to be redirected around the closed area. It would be natural for controllers toexperience higher workloads in such situations. When controllers are preoccupied with gettingall traffic safely from A to B, absorbing additional delay for EHAM inbounds will likely beat the bottom of their priorities.

With winds it is a slightly different story, as it is always present and is thus an influence tobe reckoned with. The amount of delay that can be absorbed through linear holding anddropping will generally be less affected by wind than detouring and turtling. This is due tothe fact that it is trickier to foresee what effects turning into or away from headwinds will haveon the amount of absorbed delay. Of course, different routes may experience different windconditions, resulting in some routes at times being better fit for delay absorption than others.Without an accurate wind model, however, no conclusions can be drawn on the dominanceof certain wind directions and their effects on delay absorption.

7-5-5 Military Airspace

The availability of military airspace affects which routes are open and the amount of directroutings that can be used in the upper airspace. The average amount of seconds delayabsorbed per NM will remain unchanged, but due to the shortened routes the potential foren route delay absorption is likely to reduce.

No simulations have been performed that evaluate traffic scenarios where traffic is flyingthrough military airspace, but based on the airspace maps some reasoning can be done as towhich routes will be affected most.

All sectors are in a way connected to military airspace. In the Jever sector this has alreadybeen explored, as the TUSKA-EEL route is bounded on both sides by military airspace. Two


62 Results

effects should be taken into account when considering the effects of open military airspace:routing changes for EHAM inbounds and changes in routings of other traffic.

The first of these may initially be expected to be small, however, having the military airspaceavailable may result in flights entering MUAC airspace at other points than the designatedwaypoints, i.e. anywhere between TUSKA and KESUR or GREFI and TUSKA. In orderto have a predictable amount of delay absorption, the detouring options should already beknown. If aircraft that would originally have been on the TUSKA route enter at anotherpoint, there is no standard detouring procedure available for this flight.

Additionally, traffic travelling on other directions used to be clearly separated from theTUSKA-EEL traffic, but may now be given directs that cause new conflicts, or could re-solve other conflicts.

In the Brussels and Hannover sections the effects of military airspace are likely to be smallerthan for the Jever sector, as in these sectors no detouring or turtling is performed. Linearholding and dropping can still be applied in these sectors, even if military airspace is available.The directs may in these sectors result in shorter trajectories, which will reduce the totalamount of delay that can be absorbed on a route. Although it will still affect the predictabilityof the delay absorption capacity, the implications would be expected to be less severe thanfor the Jever sector.


Chapter 8

Discussion

The results that are presented in Chapter 7 should still be interpreted in light of the researchquestions stated in Chapter 3. This is done in this chapter by first answering the six sub-questions before considering the main research question: “How much delay can be absorbedby MUAC for Schiphol airport inbound flights?”.


and2. What is the most effective way to absorb FIR delays en route?

From theoretical values presented in Chapter 7, an average delay absorption capacity of 0.4s/NM was found for linear holding and 1.1 s/NM for dropping. For detouring and turtling,essentially the same as linear holding and dropping performed over an extended trajectory,were found to have the same average absorption capacity per NM. However, for each addi-tionally flown nautical mile, eight seconds should be added to the total amount of delay thatcan be absorbed.

An interesting notion is the increased expected effectiveness of delay absorption using drop-ping for the longer routes that have a bigger portion of cruise still within the MUAC airspace.It was shown in Section 7-5-3 that these routes may have a lower maximum delay absorptioncapacity than the shorter routes, but benefit more from dropping to lower flight levels.

Taking the aircraft performance into account during simulation runs revealed that the averagevalue for linear holding was accurate, but the value for dropping was too optimistic. Ratherthan being 2.8 times more effective, dropping proved on average to be 1.7 times more effectivethan linear holding. The discrepancy between theory and simulation lies in disregarding thetime it takes to obtain the reduced speed, and the speeding up of the aircraft during descent.For each delay absorption measure, the average delay absorption capacity can simply becalculated using Equations 8-1 through 8-4.

The most effective way to absorb delays would clearly be turtling, as it combines the ‘bonus’of extra mileage in the upper airspace with the effectiveness of dropping. Since this method


64 Discussion

is not feasible for all routes, in general the most effective means of delay absorption would bedropping.

Lin = 0.4 ·DMUAC (8-1)

Drop = 0.7 ·DMUAC (8-2)

Detour = 8 ·DExtra + 0.4 · (DMUAC +DExtra) (8-3)

Turtle = 8 ·DExtra + 0.7 · (DMUAC +DExtra) (8-4)

3. How much more fuel efficient is en route delay absorption than delay absorption in the

lower airspace?

The four delay absorption measures all have a different effect on fuel consumption comparedto the normal operations. Fuel savings of 0.1% within MUAC airspace were found for linearholding, 45% for dropping, and 50% for turtling. Detouring was the only one to be un-favourable, with an additional fuel consumption of 5.1%. An overview of these numbers andthe fuel flow can be found in Table 8-1.

An explanation for the very significant reduction of fuel consumption during dropping andturtling lies in initiating the descent at an earlier stage. During this portion of the flight,throttle is set back to idle, resulting in a considerably lower fuel flow and a lower total fuelconsumption. However, even taking this into account, savings of up to 50% seem to berather optimistic. Hence it is advisable to further investigate the effects on fuel consumptionusing different performance models or by further verification and validation of the currentimplementation of the BADA model.

Table 8-1: Fuel efficiency compared to lower airspace holding

Measure Fuel Flow [kg/s] Total fuel savings [%]

Dry 0.801 -Linear holding 0.786 -0.1

Dropping 0.428 -45Detouring 1.048 +5.1

Turtling 0.520 -50

Contrary to initial expectations, fuel consumption per second in the typical speed regimes inthe lower airspace is very similar to the fuel consumption per second in the en route airspace,as shown in Figure 7-1. Hence en route delay absorption is not inherently more fuel efficientthan delay absorption measures taken in the lower airspace.


65

4. Which independent variables have the biggest impact on MUAC’s delay absorption

capabilities?

Mass was found to have a large effect on the MRC of an aircraft. In the simulations, all flightswere assumed to have the reference mass (which lies at 70% of the minimum and maximummass of the aircraft), and it was found that all flights were originally planned to fly fasterthan the MRC at their respective altitudes and masses. But from the .so6-files it is unclearwhat Eurocontrol’s assumptions on aircraft mass have been.

Had a lower mass been assumed, then the amount of delay that could potentially be absorbedwould be larger, and vice versa. Any deviation between the mass used by Eurocontrol andthe mass used to compute the delayed flight profile affects the accuracy of the results. If themass has been overestimated by 10%, this means that the speed could have been reducedby 25 knts TAS more, which, especially over longer trajectories, could make a considerabledifference.

The average delay absorption capacity of 0.4 s/NM during linear holding is a conservativefigure of delay absorption compared to the rule of thumb used by en route controllers thatstates that per 100 NM, one minute of delay can be absorbed. This may imply that thereference mass used for the simulations in this research work are a bit too high.

Moving on to the airline intent, no significant difference was found in the delay absorptioncapacity of legacy carriers and LCC. Although this is contradicting the assumption thatdifferent airlines use different fuel strategies, it does not mean that there are no differencesin practice. A possible explanation could again lie in the way in which the flight plan data iscreated in the .so6 M1 format by Eurocontrol. It is likely that these flight plans are estimates,based on the most common combination of routes and speeds that are typically flown betweentwo airports. If this is the case, any airline specific data would be filtered out, and it is obviousthat no significant airline intent can be found from the so6-files. Both for the mass and airlineintent a more thorough analysis of real flown data and data from the airline would be required.

The option of being able to absorb more delay on some routes than others has been explored,but all routes seemed to show a similar range in terms of maximum delay absorption capacity.However, the maximum delay absorption is a theoretical value. In practice, there is of coursea difference between different routes and their delay absorption capacity. Take for examplethe possibility of some routes to extend trajectories by means of detours.

Also, on a sector level differences can be found in the delay absorption capacities. Routesgoing through the Brussels sector would be expected to have a lower effective delay absorptioncapacity. Not because of any aircraft related issues, but purely because it is the busiest partof the MUAC airspace, and delay absorption measures were found to result in an increase inconflicts and communications workload.

Weather, winds especially, are a known disturbing factor in air traffic control. It is difficultto assess the exact effects of wind on delay absorption without an actual wind model, butintuitively the detouring and turtling operations would likely be affected most. Turning anaircraft away from its route may turn it more into headwinds, resulting in a lower ground speedand thus a bigger delay absorption. Dropping is also likely to experience some effects fromwind, as winds may vary across different flight levels. Because of the relatively small flight levelreduction, the winds are expected not to change as dramatically as during detouring/turtling.


66 Discussion

Although it sounds nice to have this potential additional delay absorption, it is difficult tocompute and account for these effects beforehand. When it comes to a possible implementa-tion, it is important for LVNL and MUAC to be on the same page as to how much they wantto and are able to delay which aircraft.

Then finally, there is the concern of the availability of military airspace. No simulations havebeen run, as different datasets would be needed. But analysing the route maps traffic comingfrom the North/North-East would be most affected. For the Jever sectors it would meanthat more directs would be given, and traffic would be less structured. For detouring andturtling this could result in additional conflicts and thus in higher (communication) workloadfor the ATCos. The effects on linear holding and dropping would be expected to be smaller,since the most prominent change would be the potential change in trajectory length, whichmight reduce the amount of delay that can be absorbed. Changes to the number of conflictscan not be estimated without a simulation, and thus no conclusive effect on (communication)workload can be formulated.

Concluding, within the simulation the mass assumption is expected to be the most influentialon delay absorption. In practice, this effect may be amplified by the airline intent, but nodata was found to prove this. The route is also a very important factor in the amount ofdelay that can be absorbed, as its length and orientation partially determine whether moreintense delay absorption measures such as detouring and turtling can be implemented.

The availability of military airspace is expected to have a limited effect on linear holdingand dropping operations, but could potentially have bigger effects on detouring and turtlingoperations. Bad weather and wind are known to have a big effect on operations, but the sizeof the effects on delay absorption could not yet be quantified and requires more research.

5. What are the effects on air traffic flying towards other destinations than Schiphol airport?

Due to the absence of a realistic conflict resolution algorithm in BlueSky, it is not possible tosay what would happen to i.e. the average amount of time spent within the MUAC airspace.Having this figure would be beneficial as it can be used to estimate the effects of en routedelay absorption on airspace capacity.

In the absence of this value, an indication of the effects on other traffic can be made from thenumber of conflicts. It was found that the number of conflicts in the Brussels and Hannoversectors in February would hardly be affected by en route delay absorption measures. But it isquite the opposite for the high season day: where Brussels experiences around 100 additionalconflicts due to linear holding and dropping, whereas Hannover sees a decline of roughly thesame size in the total number of conflicts. The Jever sector experiences 4 to 10% less conflictsduring all delay scenarios, except for the linear holding and dropping scenarios in August,where around 4% more conflicts occur.

It is difficult, if not impossible, to explain why at some occasions the number of conflictsdeclines while in other cases it rises. Of course, if more traffic is present in the airspace itwould generally be more likely for flights to get in conflict with each other. But because thenumber of conflicts depends not only on the amount of traffic, but also how they are positionedin and moving through the airspace determines whether or not conflicts will occur, it is likelythat the size of the selected traffic samples plays a role in this. If more and/or longer traffic


67

samples are to be selected, a more conclusive answer could be given on the overall effects ofdelay absorption in the en route airspace on the amount of conflicts. These bigger sampleswould average out the potential outliers that may have been selected for research in this work.

Returning to the effects on other traffic: in total the effects of linear holding and dropping forEHAM on other traffic will be positive for the low season operations, and potentially slightlynegative during the high season day due to the additional conflicts. Detouring and turtlingwould in both scenarios result in less conflicts and thus less required interventions with othertraffic for ATCos.


Because of the difficulty in accurately assessing the mental workload, the decision was madeto only evaluate the workload associated to the communication between ATCos and pilots.For the two researched days a slight overall increase in workload was found during linearholding and dropping (+0.4% and +1.0% in February, and +1.3% and +1.8% in August,for linear holding and detouring respectively), and a small decrease in total workload fordetouring and turtling (-0.6% for both detouring and turtling in February, and -2.8% and -2.9% for detouring and turtling in August). Although assessing the communications workloadis rather straightforward, it is still difficult to establish a value of what an acceptable additionalworkload would be, and at what times this additional workload would be manageable for theATCos. For now, the assumption is made that any change in workload lower than +3.0%percent is workload feasible for a controller, no matter what the reference base workload is.

Even though these average changes in communication workload are promising, it is importantto evaluate how these differences occur during the day. When looking more closely it is foundthat in most cases, a peak in workload is also associated with a peak in the change in workload.In the previous chapter the workload graphs of the Brussels sector on the February test dayhave been considered, and the same tendency that peaks in absolute workload are connectedto peaks in the change of workload can be found across the graphs of the other sectors. Thisphenomenon arises predominantly, but not exclusively, during the low season test case, wherepeaks of 5% to 10% additional workload are observed.

Especially during the low season test day, the peaks in delay absorption demand seems tomatch up with the peaks in traffic at the three evaluated MUAC sectors. This makes thatduring these times it is not workload feasible for MUAC to absorb all (or as much as possible)delay as they can. Rather, if a form of delay absorption is to be implemented also duringthese times of day, it might be worthwhile to investigate if specific flights can be selected,rather than trying to delay all flights.

Outside of these peaks, the change in workload generally lingers between -2 and +2% forlinear holding and dropping for all sectors. Anything reducing the workload is of course veryworkload feasible for controllers. The 2% increase would be considered to be an acceptablelevel if the assumption of a maximum workload increase of 3% is maintained, since even withthis additional work no peak workload levels are obtained.


68 Discussion

How much delay can be absorbed by MUAC for Schiphol airport inbound flights?

In general, the average delay absorption values found and discussed under the first of the re-search sub-questions can be used as a reference to how much delay can be absorbed by MUACfor Schiphol inbound flights. However, before completely settling on this, it is important totry and include the insights on workload and airspace structure into these figures as well.

The evaluation of delay absorption in the Brussels sector showed increased communicationsworkload throughout the two test days. In addition, it should be noted that the transfer ofexecutive control from MUAC to Belgocontrol before control is ultimately handed to LVNLinduces additional work and complexity for the controllers. Although it is technically possibleto implement delay absorption for these routes, in practice the implementation might proveto be difficult.

The Hannover sector’s low and high season day show similar workload patterns throughoutthe day. Workload changes due to delay absorption are also very similar between the twodays, with values mostly swinging between -3 and +3 percent difference from the dry runworkload. In the morning some significant peaks (up to 15%) are seen during which delayabsorption may not be desirable to the extent it was implemented now.

Finally, there is the most northerly located sector: the Jever sector. This was the only sectorthat had the option of detouring and turtling as well as linear holding and dropping. Duringall scenarios except the high season linear holding and dropping scenarios, an overall decreasein workload was found. This mostly positive effect on workload, in combination with its longroutes and relatively little traffic ideal for en route delay absorption. Of course, even with thispositive outlook, care must still be taken in deciding when and how delay will be absorbed inthis sector, as excessive increases in communications workload are equally undesirable hereas they are in any of the other sectors. A disadvantage of this sector is that the change inworkload does not seem to be easily predicted. Neither the expected change in workload orthe traffic density showed strong correlations with the actual change in workload for the Jeversector.


Chapter 9

Conclusions

This work reported in this thesis was centered around finding the answer to the question ‘Howmuch delay can be absorbed by MUAC for Schiphol airport inbound flights?’. By breaking thequestion down into several smaller research questions, the effects of en route delay absorptionon fuel consumption, en route controller communication workload, and other traffic have beenexplored.

To start off with the main research question first: delay absorption within the MUAC airspacewas found to be 0.4 s/NM for linear holding and 0.7 s/NM for dropping, with distances rangingbetween 35 and 160 NM. For the three routes through the Jever sector that were found eligiblefor detouring and turtling, an additional 8 seconds should be counted for each additionallyflown nautical mile.

The fuel consumption has been compared to the fuel consumption in the original scenario.From this only a slightly lower fuel consumption was found for linear holding (-0.1%), but asignificantly lower fuel consumption for dropping and turtling (-45% and -50%, respectively).This strong reduction in fuel consumption can partially be explained by the earlier initiateddescent, during which the aircraft can throttle back to idle thrust, but more research isrequired to fully understand and support these large drops in fuel consumption for droppingand turtling. Detouring was found unfavourable in terms of fuel (due to the additional pathlength), but is nevertheless an effective means of delay absorption.

An important aspect for the possible implementation of en route delay absorption is thecontroller workload. In order to keep results as tangible as possible, a simplistic workloadmodel was developed to assess the communication workload for ATCos. Using this model,it was found that the communication workload generally strongly increases during MUACpeak loadings. Adding more work when a controller is already at his/her busiest is notvery desirable, which is why it is unlikely that delay absorption during peak loading can beimplemented in the way it was simulated.

However, off-peak, workloads were sometimes found to be even lower than in the originalscenario. This can be explained by the reduction of the number of conflicts, due to which


70 Conclusions

some of the workload assigned for resolving conflicts could be eliminated. During these timesof day en route delay absorption would be more than just feasible.

Effects on traffic other than EHAM inbounds are positive for the Hannover sectors, where onboth test days a reduction of the total number of conflicts was found. Traffic flying throughthe Brussels sectors are less fortunate, with a small number of additional conflicts on theFebruary test day, and a large increase of around 100 conflicts per day during the high seasonscenarios. The Jever sector was the only sector to be equipped with detouring and turtlingoptions, and during all scenarios except for the August linear holding and dropping scenarios areduction of the total number of conflicts was observed. Overall, the total number of conflictsduring linear holding and dropping runs for the low season day were found to lower by 1.1%and 0.4% respectively. The high season saw an overall increase of 0.7% of the total numberof conflicts. It is thus expected to be favourable for other traffic if en route delay absorptionis performed during low season days, but mostly unfavourable during high season.

Overall, the Jever sector was found to be most suitable for en route delay absorption, followedby the Hannover sector. The Brussels sector would be least favourable due to the additionalworkload en route delay absorption would induce in combination with the already difficulttraffic situation where Schiphol inbounds are transferred from MUAC to Belgocontrol, beforebeing transferred to the control of LVNL.

In addition to these bigger topics, also some smaller analyses have been performed to giveguidance to the effects of certain factors that are expected to influence the delay absorptioncapacities. From this it was found that within this research, the assumption on the mass of theaircraft is critical for the delay absorption capacity. Also, further research was recommendedto get a quantitative indication of the effects of wind and the availability of military airspace.Although expected otherwise, no significant difference was found between the delay absorptioncapacity of LCCs compared to legacy carriers.

When care is taken in when, how and where en route delay absorption is implemented, itmost definitely shows potential to (partially) replace delay methods in the lower airspace.


Chapter 10

Recommendations

Now the results and conclusions from this research have been drawn up, it is time to reviewwhat can still be done to further improve these results, and what fields of further researchhave opened up as a result of it.

One of the main points of improvement would be to work based on actual flown data, ratherthan Eurocontrol’s DDR2 Model 1 flight plans. This would allow for a more realistic repre-sentation of traffic flows through MUAC airspace, and for evaluation of the effects of directs,whether facilitated by the availability of military airspace or not. Added benefit of usingflown data is that it would circumvent the current assumption of a standard rate of descent of1500 ft/m, and could potentially provide more insight in the cost index strategies of differentairlines. The latter is only possible if the actual aircraft weights are known as well, whichcan be used to more accurately determine the MRC. As mentioned in Chapter 8, additionalverification and validation on the fuel consumption values produced by the aircraft perfor-mance model are required to give further insight in the origin of the big reductions in fuelconsumption during dropping and turtling.

Another possible addition to improve the realism of the results would be the implementationof a wind model. Especially for detouring and turtling, the effects of wind could be quitesignificant. But also dropping could be affected by different winds at lower altitudes. Ulti-mately, it would be ideal if the effects of wind could be incorporated in the computation ofthe amount of delay that can be absorbed.

A hiatus in this research is the absence of a representative conflict resolution algorithm. Thisabsence has hindered the evaluation of the effects of en route delay absorption on other traffic.Only the first order of conflicts have been noted, but potential knock-on effects of conflictresolution on fuel consumption and workload have not been considered. Having more insightin the effects of delay absorption on EHAM inbound flights on non-EHAM inbound trafficcould also potentially be valuable if en route delay absorption is ultimately implemented forseveral big European airports simultaneously.

Evaluation of the effects on the mental workload controllers would experience due to delayabsorption measures would also be a valuable asset in future research, as in this research onlythe ‘practical’ communication workload has been considered.


72 Recommendations

Focussing more on the creation of the scenarios, several more improvements could be made infuture research. Firstly, the possibility of speeding an aircraft up to resolve planning conflictshas not been considered. In some traffic situations it may be preferable for MUAC ATCosto speed up a flight, rather than slowing it down. This option has not been considered yet.Secondly, in this research all flights that demand en route delay absorption are slowed down.It should be interesting to explore if it is possible to further optimise the total amount ofdelay that can be absorbed, by applying delay absorption measures based on the amount ofdelay that can be absorbed, rather than on what should be absorbed. Severely penalising oneflight may result in several other flights to continue uninterruptedly, but this is somethingthat requires further investigation and would completely change the ways the currently usedarrival planner works.

During the research it was found that although theoretically dropping should be almost threetimes more effective to absorb delay than linear holding, in practice dropping was only 1.7times more effective. Because the speed reduction is implemented in the scenarios based onthe assumption that the speed change is instantaneous, a factor could be applied to get moreout of the potential of dropping.

Apart from the changes and additions that have been suggested to further enhance results onthis particular topic, new interesting fields for research have opened up. Where this researchhas focussed completely on the en route effects of delay absorption, the lower airspace alsodemands some attention to properly implement delay absorption. What are the effects of thelower entry speed on the workload of ACC controllers? How accurately and how long beforeentering LVNL airspace can LVNL determine the size of the required delay absorption? Howand what should LVNL and MUAC communicate delay absorption requests?


Appendix A

.So6 to .scn Conversion

Table A-1: .so6 data format [DDR2 Developers, 2014]

No. Field Type Comment

1 Segment identifier Char First point name “ ” last point name

2 Origin of flight Char ICAO Code

3 Destination of flight Char ICAO Code

4 Aircraft type Char

5 Time segment entry Num HHMMSS padded with zeros

6 Time segment exit Num HHMMSS padded with zeros

7 Flight level segment entry Num

8 Flight level segment exit Num

9 Status Char 0: climb, 1: descent, 2: cruise

10 Callsign Char

11 Date segment entry Num YYMMDD padded with zeros

12 Date segment exit Num YYMMDD padded with zeros

13 Latitude segment entry Float In minute decimale

14 Longitude segment entry Float In minute decimale

15 Latitude segment exit Float In minute decimale

16 Longitude segment exit Float In minute decimale

17 Flight identifier Num Same as the one provided in expandfile

18 Sequence Num Start at 1 for every new flight, incre-mented by one for each segment

19 Segment length Float In NM

20 Segment parity Num


74 .So6 to .scn Conversion

Example of a .scn input:00:01:00.00>CRE BCS2582,B734,50.0575,1.00805555,126,23500,449.529507692

00:01:00.00>ORIG BCS2582,EGNX

00:01:00.00>DEST BCS2582,LFPG

00:01:00.00>LNAV BCS2582 ON

00:01:00.00>VNAV BCS2582 ON

00:01:00.00>ADDWPT BCS2582,50.03305555,1.02611111667,23000,303.192978975

00:01:00.00>BCS2582 DIRECT BCS2582000

00:01:00.00>ADDWPT BCS2582,49.7152777833,1.26222221667,23000,265.971891915

00:01:00.00>ADDWPT BCS2582,49.6747222167,1.29222221667,22000,302.805485008


75


76 .So6 to .scn Conversion


Appendix B

BlueSky Commands


78 BlueSky Commands

Table B-1: Fully referenced from the BlueSky Open ATM Simulator Command Reference

Command Purpose

? Use ? as (only) in-line argument to read helptext and argu-ment list or type command without arguments

ESC Quit programF3-key Recall last typed command on edit lineF11-key Toggle full-screen modeplus/minus Zoom in/outarrows Pan left/right/up/downCRE Create an aircraft at specified position (use mouse)DEL Delete an aircraftMOVE Move an aircraft (use mouse)POS Retrieves position and info on aircraftHDG Provide an aircraft with headingLEFT/RIGHT Relative heading commandSPD (IAS/Mach) Speed commandALT Altitude commandVS Vertical speedDEST Destination for navigation purposesORIG Origin for bookkeeping purposesLNAV ON Switch LNAV mode onVNAV ON Switch LNAV mode onDT Sets time step to the value dt for FIXDT, shows current DT

without argumentFIXDT ON/OFF Forces the Traffic and Experiment Manager to use a fixed

time stepIC Initialize condition/scenario, just IC with no arguments

opens the Dialog BoxOP/START/RUN/CONTINUE Start or continue runningHOLD/PAUSE Pause or hold simulationEXIT/QUIT/Q/STOP/END Exit programSAVEIC Save current situation as ICADDWPT Add new waypoint to planned routeLISTRTE Display planned routeDELWPT Delete waypointASAS ON/OFF Switch ASAS on/off


Appendix C

Workload

In this appendix all workload plots can be found, first for the test day in February, wherethe absolute communications workload and the relative change in communications workloadis plotted for the Jever, Brussels and Hannover sectors respectively. Next, these plots arepresented, but for the August test day.


80 Workload


0

500

1000

1500

2000

2500

3000

3500


Communications workload - Jever sector - 04-02-2015


Figure C-1: Communications workload - Jever sectors - February


−5

−4

−3

−2

−1

0

1

2

3

4

Change in w

ork

load [

%]

Change in communications workload relative to dry run - Jever sector - 04-02-2015


Figure C-2: Relative change in communications workload - Jever sectors - February


81


0

500

1000

1500

2000

2500

3000



DryDetouringTurtling

Figure C-3: Communications workload - Jever sectors - Detouring/turtling - February


−6

−4

−2

0

2

4

6

Change in w

ork

load [

%]


DetouringTurtling

Figure C-4: Relative change in communications workload - Detouring/turtling - Jever sectors -February


82 Workload


0

1000

2000

3000

4000

5000

6000




Figure C-5: Communications workload - Brussels sectors - February


−2

−1

0

1

2

3

4

5

6

Change in w

ork

load [

%]



Figure C-6: Relative change in communications workload - Brussels sectors - February


83


0

500

1000

1500

2000

2500

3000

3500

4000


Communications workload - Hannover sector - 04-02-2015


Figure C-7: Communications workload - Hannover sectors - February


−5

0

5

10

15

20

Change in w

ork

load [

%]

Change in communications workload relative to dry run - Hannover sector - 04-02-2015


Figure C-8: Relative change in communications workload - Hannover sectors - February


84 Workload


0

500

1000

1500

2000

2500

3000




Figure C-9: Communications workload - Jever sectors - August


−6

−4

−2

0

2

4

6

8

10

12

Change in w

ork

load [

%]



Figure C-10: Relative change in communications workload - Jever sectors - August


85


0

500

1000

1500

2000

2500



DryDetouringTurtling

Figure C-11: Communications workload - Jever sectors - Detouring/turtling - August


−15

−10

−5

0

5

10

Change in w

ork

load [

%]


DetouringTurtling

Figure C-12: Relative change in communications workload - Jever sectors - Detouring/turtling- August


86 Workload


0

1000

2000

3000

4000

5000

6000

7000

8000

9000




Figure C-13: Communications workload - Brussels sectors - August


−4

−2

0

2

4

6

8

10

12

Change in w

ork

load [

%]



Figure C-14: Relative change in communications workload - Brussels sectors - August


87


0

500

1000

1500

2000

2500

3000

3500

4000


Communications workload - Hannover sector - 06-08-2014


Figure C-15: Communications workload - Hannover sectors - August


−10

−5

0

5

10

15

Change in w

ork

load [

%]

Change in communications workload relative to dry run - Hannover sector - 06-08-2014


Figure C-16: Relative change in communications workload - Hannover sectors - August


88 Workload


Appendix D

Conflicts

This appendix shows the distribution of the conflicts across the two sample days.


90 Conflicts0:00

1:00

2:00

3:00

4:00

5:00

6:00

7:00

8:00

9:00

10:00

11:00

12:00

13:00

14:00

15:00

16:00

17:00

18:00

19:00

20:00

21:00

22:00

23:00

Time of day [EHAM LT Hours]

0

50

100

150

200

250

300

350

Number of Conflicts [-]

Conflicts in MUAC airspace - 1 hour intervals - 04-02-2015


Figure D-1: Total number of conflicts within MUAC airspace - February

0:00

1:00

2:00

3:00

4:00

5:00

6:00

7:00

8:00

9:00

10:00

11:00

12:00

13:00

14:00

15:00

16:00

17:00

18:00

19:00

20:00

21:00

22:00

23:00

Time of day [EHAM LT Hours]

0

100

200

300

400

500

Number of Conflicts [-]

Conflicts in MUAC airspace - 1 hour intervals - 06-08-2014


Figure D-2: Total number of conflicts within MUAC airspace - August


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