European Wake Vortex Mitigation Benefits Study. Work Package 3 Deliverable: High Level Benefits Analysis & Systemic Analysis

Transcription

1 European Wake Vortex Mitigation Benefits Study Work Package 3 Deliverable: High Level Benefits Analysis & Systemic Analysis D Galpin (NATS) C Pugh (NATS) D Cobo (ISDEFE) L Vinagre (ISDEFE)

2 EUROPEAN WAKE VORTEX MITIGATION BENEFITS STUDY WP3: High Level Benefits Analysis (PART A) & High Level Systemic Analysis (PART B) D Galpin (NATS) C Pugh (NATS) D Cobo (ISDEFE) L Vinagre (ISDEFE) SUMMARY PART A: This technical contribution to Work Package 3 consists of a high level benefits study conducted for the airports brought forward from Work Package 1. Benefits (in terms of extra movements) were estimated for 3 concepts ATC-Wake, CREDOS, and Time-Based Spacing and took advantage of the meteorological profiles produced in Work Package 2. PART B: This technical contribution to Work Package 3 consists of a high level systems analysis describing the required modifications for the implementation of the WV mitigation concepts considered in this study on a generic ATM system. This analysis intends to serve as an input to develop the costs assessment required to obtain the Cost Benefit Analysis for the different target airports identified in Work Package 1. Ingeniería de Sistemas para la Defensa de España (ISDEFE), November 2005 National Air Traffic Services Ltd, Corporate Technical Centre, November 2005 FINAL Page i

3 Ingeniería de Sistemas para la Defensa de España (ISDEFE), 2005 National Air Traffic Services Limited 2005 FINAL Page ii

4 Distribution List Andrew Harvey Debi Turp Lluis Vinagre Daniel Cobo Martyn Richards Owen Davies John Greenwood Eurocontrol UK Met Office ISDEFE ISDEFE NATS NATS NATS Amendment History Issue Issue Date Author Reason for Issue Draft 1 28/10/05 Draft 2 4/11/05 Final 17/11/05 NATS & ISDEFE NATS & ISDEFE NATS & ISDEFE 1 st Draft for Review Incorporating comments from 1 st draft Comments included FINAL Page iii

5 Executive Summary PART A: For the airports brought forward from Work Package 1, a benefits study was conducted for 3 wake vortex mitigation concepts currently under development; ATC- Wake, CREDOS (Crosswind Reduced Separations for Departure Operations), and Time-Based Spacing (TBS). The study incorporated traffic data (volume and composition), extracted from the CFMU as part of Work Package 1, and surface wind statistics generated from analysis of METARs (Meteorological Aerodrome Reports) in Work Package 2. Data on winds aloft was not available for this study, and as a result the wind conditions under which the concepts could be employed had to be simplified to be compatible with the surface wind data. Therefore, for ATC-Wake and CREDOS to be employed a surface crosswind component of 6 knots had to be present for at least 2 consecutive METARs and the visibility had to be at least 1km. For TBS to be beneficial a surface headwind component of at least 10 knots was required. The method of determining the potential benefit these concepts could produce (in terms of extra movements) is summarised below: ATC-Wake Firstly, hours of the day (for each season) where there appeared to be a real and present demand for extra capacity were identified. For these hours the capacity was calculated under current operations (that is, the maximum number of arrivals that can be accommodated for the traffic mix in that hour). Next, the capacity was calculated if, when the required meteorological conditions existed, all pairs were separated by the ATC-Wake Separation. Two estimates were analysed for the ATC-Wake separation: 2.5Nm, and 3Nm. The benefit was said to be the difference between the theoretical capacity under current operations and the theoretical capacity when ATC- Wake was employed whenever possible. CREDOS The method for calculating benefit from ATC-Wake described above was adopted for use with CREDOS as well. The CREDOS separation requirements tested were: 90 seconds separation for WV pairs, and no WV separation requirement (i.e. WV pairs were subject to the same separation requirements as non-wv pairs). TBS Analysis of wind delay, wind statistics and traffic counts could not yield an empirical relationship between headwinds and throughput. Therefore, a more theoretical approach had to be used. Using traffic figures extracted from the CFMU (Central Flow Management Unit), the effect of different strengths of headwind was predicted by assuming that the headwind caused the aircraft to decelerate as if they were maintaining a constant airspeed (i.e. in a 10 knot headwind, aircraft will lose 10 knots of ground speed). This was then used in conjunction with surface wind conditions to give an idea of what the actual loss of capacity could be over a typical year. The results of the analyses are summarised in the following table: FINAL Page iv

6 Table 1: Estimated Benefit in terms of Movements per year (extra movements in the case of ATC-Wake and CREDOS, recovered movements in the case of TBS) for each of the Mitigation Concepts ATC-Wake CREDOS TBS Airport 3Nm 2.5Nm 80s 90s EGLL 10,858 26,280 9,490 6,843 1,788 EDDF 3,923 11, ,801 EHAM 1,277 5, LFPG 638 1, LEMD 547 4, EDDM LIRF LSZH LEBL EGKK EGCC For ATC-Wake and CREDOS, where the aim is to increase throughput, the single biggest factor in whether or not a benefit was predicted was whether or not there was enough traffic for the runways to qualify as being queued. At current traffic levels, EGKK, EGCC, LSZH, EDDM, and LEBL, rarely (if at all) meet the criterion for the runway to be queued. As a result, under the method used in this study, these airports were not deemed to have the traffic to take advantage of any benefits that a wake vortex mitigation concept could provide. Airports where there was a particularly high estimation of benefit were EGLL, EDDF (for ATC-Wake only), EHAM, LEMD and LFPG (for ATC-Wake only). In general, benefit was less for departures due to the smaller number of aircraft pairs that are subject to wake vortex separation requirements. Likewise for TBS, for a number of the candidate airports unused capacity mean that headwinds are not expected to have a detrimental effect on the throughput. As a result, throughput was not expected to be compromised due to headwinds at EGKK, EGCC, LSZH, LEBL, EDDM, and LFPG. For the airports where there is very little leeway in terms of spare capacity, a headwind can result in the loss of a significant number of movements over a year. The consideration of traffic growth and changes to runway operating procedures or airport layout is out of the scope of the project. However, some work was carried out to predict benefit in the case where there was a demand for extra capacity throughout the day. The results highlighted the rarity of suitable crosswind conditions at EDDM and LSZH, and the low percentage of Heavy aircraft at LIRF and LEBL, which limit FINAL Page v

7 the suitability of ATC-Wake and CREDOS at those airports. Other airports, such as EGCC, show potential to be highly beneficial candidates once the traffic levels can warrant it. The results summarised in the paragraphs above highlight the differences in suitability for the concepts between the candidate airports. However, the figures generated in this study should be taken only as indications. There were a number of significant limitations that any high-level benefit study like this will suffer from, and as a result the figures produced should be seen only in the context of the assumptions made. In particular, the meteorological criteria for reduced separations (ATC-Wake and CREDOS) or lost capacity (TBS) were over-simplified. In addition, insufficient airport data required assumptions to be made about the runway configuration in use and how aircraft are sequenced. The validity of these assumptions could affect the results. PART B: The first section of part B (section 7.1) is an overview of a generic CNS/ATM System, the architecture of which is presented as a high level functional decomposition into a logical set of functional blocks. This high level overview provides a basis on which to discuss the impact of implementation and operation of the wake vortex mitigation concepts (WVMC) might have on such blocks. The second section (7.2) presents a brief description of the state-of-the-art regarding the available (COTS) and under development (R&D) technologies applicable for measuring weather and wake vortex parameters required or recommended for the operation of the WVMC. Based on the results of a WV detection technology case study (Eurocontrol TRS-C52/2004), three sets of technological solutions are proposed: a short-term optimal operational solution (COTS technologies), a shortterm low cost solution (more cost-effective) and a mid-term solution (enhanced performance but most technologies are still under R&D). The third section (7.3) briefly describes the three WVMC considered in this study, including a functional description and the main system requirements. The section also presents the main high level impact of the implementation and operation of each WVMC might cause on each CNS/ATM System functional block. The impact of each WVMC depends on the level of implementation selected (which depends on the WVMC requirements near or mid/far term concept, the CNS/ATM and service providers enhancements and the technological solutions availability). It is noted that the available information concerning WVMC is still scarce, especially with regard to CREDOS, which is a concept to be developed in the next three years. Nevertheless, this section provides a big picture of the main requirements that the CNS/ATM System shall fulfil to enable each WVMC implementation and operation. The fourth and last section (8) of part B provides some guidelines on the main steps that should be followed to conduct the cost-benefit analysis (CBA) corresponding to the implementation of the suitable WVMC for each targeted airport. However, any detailed CBA is out of the scope of this WP. It must be noted that benefits considered in this study and estimated in Part A of this report refer to runway capacity FINAL Page vi

8 improvement (extra movements in the case of ATC-Wake and CREDOS, recovered movements in the case of TBS) and other possible benefits are not taken into account (e.g. benefits by amount of delay reduction). FINAL Page vii

9 Intentionally Blank FINAL Page viii

10 TABLE OF CONTENTS INTRODUCTION...XIV PART A: HIGH LEVEL BENEFITS ANALYSIS AIRPORT OPERATING PROCEDURES AND WAKE VORTEX MITIGATION PARAMETERS Airport Operating Procedures Parameters for Wake Vortex Mitigation Schemes CALCULATING BENEFIT FROM ATC-WAKE Method Assumptions Results Parameter Sensitivity Limitations CALCULATING BENEFIT FROM CREDOS Method Assumptions Results Parameter Sensitivity Limitations CALCULATING BENEFIT FROM TIME-BASED SPACING Method Assumptions Results Parameter Sensitivity Limitations GROWTH FORECASTS CONCLUSION...51 PART B: HIGH LEVEL SYSTEMIC ANALYSIS CNS/ATM HIGH LEVEL SYSTEMIC ANALYSIS CNS/ATM Functional Blocks description...53 FINAL Page ix

11 7.2 Description of Weather and WV sensor technologies Description of WV Mitigation concepts and their impacts on the CNS/ATM System PROPOSED METHOD FOR A HIGH LEVEL COST BENEFIT ANALYSIS General Guidelines CONCLUSION REFERENCES...89 APPENDIX 1: SEQUENCING...91 APPENDIX 2: REQUIRED MINIMUM SEPARATIONS ON APPROACH...93 APPENDIX 3: REQUIRED MINIMUM SEPARATION FOR WAKE VORTEX ON DEPARTURE...94 APPENDIX 4: TECHNOLOGIES FOR WEATHER AND WV MEASUREMENTS...95 APPENDIX 5: SUMMARY OF WAKE VORTEX MITIGATION CONCEPTS (WVMC) IMPACTS ON THE CNS/ATM SYSTEM...98 APPENDIX 6: SUMMARY OF WVMC TECHNOLOGICAL REQUIREMENTS FOR THE CNS/ATM SYSTEM FINAL Page x

12 Glossary A/A A/G A/C A-SMGCS AAF ABAS ABL ADS (-B) AEP AIS ANM ANSP AO AOC ARC ATC ATCO ATFM ATIS ATM CBA CDTI CFMU CMU CNS CODA COTS CPDLC CREDOS CSPR Air/Air Air/Ground Aircraft Advanced Surface Movement Guidance and Control System ATM added functions Aircraft Based Augmentation System Atmospheric Boundary Layer Automatic Dependant Surveillance (- Broadcast) Aeronautical Environment Processing Aeronautical Information Services Air Traffic Flow Management Notification Message Air Navigation Services Provider Aircraft Operator Aircraft Operator Control Centre Archiving System Air Traffic Control Air Traffic Controller Air Traffic Flow Management Air Traffic Information Service Air Traffic Management Cost-Benefit Analysis Cockpit Display of Traffic Information Central Flow Management Unit Communications Management Unit Communications, Navigation & Surveillance Central Office for Delay Analysis Commercial-Off-The-Shelf Controller-Pilot Data Link Communications Crosswind Reduced Separations for Departure Operations Closely Spaced Parallel Runways FINAL Page xi

13 CWP DEDP EDDF EDDM EGCC EGKK EGLL EHAM EuroBen FAA FALBALA FMS FMP FPL G/G GNLU GNSS HMI IFPP IFPS IFR ILS LEBL LEMD LFPG LIRF LSZH MET MMR MONA MTCD NOTAM Controller Working position Dynamic Environmental Data Processing Frankfurt International Munich Franz Josef Strauss Manchester Ringway London Gatwick London Heathrow Amsterdam Schiphol European Wake Vortex Mitigation Benefits Study Federal Aviation Administration First Assessment of the operational Limitations, Benefits & Applicability for a List of package 1 AS applications Flight Management System Flow Management Position Flight Plan Ground/Ground GNSS Navigation and Landing Unit Global Navigation Satellite System Human-Machine Interface Initial Flight Plan Processing Integrated Initial Flight Plan Processing System Instrument Flight Rules Instrument Landing System Barcelona Le Prat Madrid Barajas Paris Charles de Gaulle Rome Fiumicino Zurich Klöten Meteorological (information) Multi-Mode Receiver Monitoring Aids Medium Term Conflict Detection NOtice To Air Men FINAL Page xii

14 PAR Precision Approach Radar PFD Planned Flight Data PVD Plan View Display RNAV Area Navigation RNP Required Navigation Performance RPL Repetitive Flight Plans RTA Required Time of Arrival RVSM Reduced Vertical Separation Minimum SID Standard Instrument Departure SDO Static Data Operations SDP Surveillance Data Processing SMGCS Surface Movement Guidance and Control System SMP ATC-Wake Separation Mode Planner SNOWTAM NOTAM on SNOW Conditions (containing snow fall information) SSR Secondary Surveillance Radar STCA Short-Term Conflict Alert STD Pair Aircraft pair for which no separation is required for wake vortex purposes alone STRAT Strategic System TACT Tactical System TAF Terminal Area Forecast TBS Time-Based Spacing TKE Turbulent Kinetic Energy TMA Terminal Manoeuvring Area TSA Temporary Segregated Area WV Wake Vortex WV Pair Aircraft pair requiring wake vortex separation WVMC Wake Vortex Mitigation Concept WVV Wake Vortex Vector FINAL Page xiii

15 Introduction The European Wake Vortex Mitigation Benefits Study (EuroBen) aims to identify and categorise European airports which could benefit from the implementation of wake vortex mitigation schemes. This report describes the high-level benefits of each of the three wake vortex mitigation schemes, namely: ATC-Wake: a wake vortex prediction/detection system that will enable airports to operate reduced separations under the appropriate meteorological conditions. CREDOS (Crosswind Reduced Separations for Departure Operations): reduced separations on departure under suitable crosswind conditions. TBS (Time based Spacing): spacing aircraft on approach using time separations. The European airports described in this report are those identified in WP1 (reference [1]), with the data having being obtained and collated in WP2 and WP2A (reference [2]). Additional airport specific information has been obtained from individual contacts whose help is gratefully acknowledged. The benefits have been defined as the number of additional movements that an airport could gain through use of the wake vortex mitigation schemes. CREDOS and ATC- Wake are both concepts where reduced separations, and hence extra movements, could be used in favourable meteorological conditions. These can therefore reduce peak delay and allow extra contingency when conditions permit. TBS has the potential to recover movements which are currently lost during distance spaced operations in headwind conditions. Part A of this report describes in detail the method of calculation for these benefits for each of the wake mitigation schemes in turn. Since the wake vortex mitigation schemes being analysed would need some form of investment, the second part of this report, Part B, gives a high-level analysis of the additional systems required to support the mitigation schemes. It is outside the scope of this WP to perform any detailed cost benefit analysis. It must be noted that this report simply assesses the high level benefits gained and systems affected by the each of the wake vortex mitigation schemes. It does not provide data or information on any safety issues which would be covered by the individual projects themselves. Hence, no consideration has been given to whether the operational procedures and associated number of movements which would result from the wake vortex mitigation schemes would be accepted by safety regulators. FINAL Page xiv

16 PART A: High Level Benefits Analysis 1 Airport Operating Procedures and Wake Vortex Mitigation Parameters 1.1 Airport Operating Procedures In order to ascertain the benefits of any wake vortex mitigation scheme, the general operating procedures of each of the airports being considered needs to be known. For airports which have multiple runways and operating configurations, those most commonly used have been considered. The summary table, Table 2, shows the operating procedures of each airport used within this study. A short description for each airport is also provided within this section, preceded by a brief explanation of the various modes of parallel runway operations. PARALLEL RUNWAY OPERATIONS 1 Whether or not parallel runways can be operated independently or not depends upon the separation between the runways. The various modes of operation possible are briefly considered below: Simultaneous Approaches to Parallel Runways: Broadly speaking, independent parallel approaches are allowed if the separation between the runway centre-lines is greater than 1035m. If the separation is less than 1035m, but greater than 915m then simultaneous approaches to parallel runways require a separation of 2Nm between successive arrivals on adjacent runways ( Dependent Runways ). Simultaneous Departures from Parallel Runways: Independent runway operations require a runway separation of 760m (provided the course divergence after take-off is 15 or more). If the runways are separated by less than 915m for simultaneous approaches, or less than 760m for simultaneous departures, then the runways are operated as if they were a single runway in these circumstances the runways are described as Closely- Spaced. Segregated Operations on Parallel Runways (i.e. arrivals on one runway, departures on the other) If the separation between the runway centre lines is greater than 760m then the two runways can be operated independently, provided that the departure course diverges immediately after take-off by at least 30 from the missed approach track of the adjacent approach. 1 Source: Reference [23] FINAL Page 1

17 If this is not the case, then the runways are Closely-Spaced and independent operations are not possible. However, this differs from the case where a single runway is used in mixed mode (arrivals and departures on the same runway), because departing aircraft do not have to wait for the preceding arrival to vacate the runway, and may take-off once the arrival has touched down. EGLL London Heathrow operates one runway for arrivals and one runway for departures. The preferred runway direction is Westerly (27L and 27R). Easterly operations are employed when the tailwind component exceeds 10 knots. EGCC Manchester International operates a pair of closely-spaced parallel runways, one for arrivals and one for departures (although both runways are only used at peak hours). The preferred runway orientation is 24. The opposite direction is employed when the tailwind component exceeds 5 knots. EGKK London Gatwick operates just one runway in mixed mode. The preferred direction, 26, is used when the tailwind component does not exceed 10 knots. EDDF Frankfurt has 3 runways, 2 parallel and closely-spaced (runways 25L/07R and 25R/07L), and one that is used for departures only (runway 18). The separation between the parallel runways requires that they be treated as a single runway for the purposes of spacing. Typically runway 18 will take 60% of the departures, the remaining 40% will take-off from either of the parallel runways. However, if there is a tailwind component on runway 18 greater than 15 knots, it is closed and all departures use the parallel runways. The preferred direction, 25, is used when the tailwind does not exceed 5 knots. EDDM Munich operates 2 parallel independent mixed mode runways. The preferred direction (08) is used when the tailwind does not exceed 10 knots. EHAM Schiphol has 6 operational runways, but typically will only use 3 at any one time. The airport operates a 2+1/1+2 runway usage concept: i.e. during an arrival peak 2 runways are used for arrivals, and one for departures, whilst during a departure peak 2 runways are used for departures and one for arrivals. The preferred runway configurations are shown in Table 2. There are a number of other contingency configurations that are employed under specific meteorological conditions, but these have not been considered in this report. LIRF Rome Fiumicino has one pair of parallel runways (16L/34R and 16R/34L) and one departure runway (runway 25). The parallel runways are dependent which means FINAL Page 2

18 that there is a diagonal separation requirement in addition to the in-trail separation requirements. The preferred operation is arrivals on both parallel runways and departures on runway R is used very occasionally for departing intercontinental flights. When the tailwind component on the parallel runways exceeds 10 knots, runway 25 is not used and runway 34L is used for departures and 34R for landings. LFPG Paris Charles de Gaulle has 2 pairs of Closely Spaced Parallel Runways, a Northerly pair and a Southerly pair. All 4 parallel runways are oriented East-West, and while each pair is closely spaced, the separation between the pairs is sufficient to allow independent operation of each. Arrivals and Departures are segregated, and for each pair, the inner runway is used for departures, while the outer one is used for arrivals. The preferred runway configuration is Easterly Operations. Westerly operations are employed when the tailwind component exceeds 10 knots. LEMD Madrid Barajas has 4 runways (2 sets of parallel runways), but at present only 2 are in use at any one time 1 for arrivals and 1 for departures. The preferred runway configuration is Northerly Operations. Southerly operations are employed when the tailwind component exceeds 10 knots. LEBL Barcelona has 2 runways, one is used for arrivals (07/25), and one is used for departures (02/20). The preferred approach configuration (25) is used when the tailwind component does not exceed 10 knots. LSZH Zurich Klöten has 3 non-parallel runways. The preferred operation is arrivals on runway 14, and runways 28 and 16 are used for departures, with runway 16 used primarily by Heavy aircraft. If the tailwind component on runway 14 exceeds 10 knots then runway 32 is used. SUMMARY The operating procedures are summarised in Table 2 FINAL Page 3

19 Table 2: Runway Operating Procedures at Candidate Airports (Italicized text signifies that the runway(s) is(are) used in mixed mode) Preferred Landing Runways Preferred Departure Runways Airport Criteria for Alternate Landing Alternate Departure Selection of Runways Runways Alternate Configuration Source 2 EGLL 27L/27R 27R/27L Tailwind > 10Kts 09L 09R Local EGCC 24R 24L Tailwind > 5Kts 06R 06L Local EGKK Tailwind > 10Kts Local EDDF 25L 25R L 25R Tailwind > 5Kts 4 07L 07R 18 07L 07R FALBALA Rpt LSZH Tailwind > 10Kts Questionnaire LEMD 33L 36L Tailwind > 10Kts Local LEBL 25 02/20 Tailwind > 10Kts /20 Local LFPG 08R 09L/09R 08L 09R/09L Tailwind > 10Kts 26L 27L/27R 26L 27R/27L FALBALA Rpt EHAM_Arrival 06 36R 36L Tailwind > 10Kts 8 18R 18C 24 Local EHAM_Departure 06 36L 36C Tailwind > 10Kts 7 18R 24 18L Local EDDM 08L 08R 08L 08R Tailwind > 10Kts 26L 26R 26L 26R Local LIRF 16L 16R 25 Tailwind > 10kts 2 34R 34L Local 2 The primary source of the information listed. Local from direct contact with airport, FALBALA Rpt (Reference: [[4]]), Questionnaire from results of questionnaire sent out under WP2A. 3 Provided the tailwind component doesn t exceed 15 knots. 4 This refers to the tailwind component on the parallel runways. 5 Runway 16 is used primarily for Heavy aircraft. 6 This refers to the tailwind component on runway This refers to the tailwind component on runway This was assumed to be an average of the tailwind components on the runways in use. FINAL Page 4

20 1.2 Parameters for Wake Vortex Mitigation Schemes In addition to the current operating procedures, details on the parameters employed under the wake vortex mitigation schemes and the meteorological conditions under which they would be used are also required. These parameters were obtained from Eurocontrol (source: from Eurocontrol) and reproduced below: ATC-Wake: ATC-Wake uses reduced arrival spacing when it is likely that the wake vortex will be transported out of the flight corridor of a following aircraft. There are no specific weather limits when ATC-Wake would be used as it is based on complicated weather and wake vortex prediction/detection models. For the purposes of this study, it has been assumed that a 6kt cross-wind at surface level would allow the wake to be transported away from the arrival flight corridor and hence ATC-wake spacing could be employed. It is recognised that the wind direction and strength would change with height; however, this further detail does not fall within the scope of this high-level analysis. As the wake is assumed to be transported away from any following aircraft, there is no variation in separations due to wake vortex weight category. Two different arrival spacing scenarios have been considered within this report: Separations of 2.5Nm, and Separations of 3Nm. CREDOS: CREDOS assumes the wake vortex is transported out of the path of the following departure. This has been assumed to be when there is a cross-wind of 6kts at surface level. Under these meteorological conditions, departures currently constrained by wake vortex separations would be reduced. Two scenarios were considered: Separations of 80s, and Separations of 90s FINAL Page 5

21 TBS: Unlike CREDOS and ATC-Wake, the aim of time-based spacing is not to gain extra capacity, but to recover capacity lost under periods of strong headwinds. Because of the present distance-based separation requirements, in periods of strong headwinds the reduction in aircraft ground speed brings about an increase in the time separation, as the aircraft take longer to cover the spacing distance. By switching to a time based spacing system it is hoped that the loss in aircraft ground speed will be compensated by a decreased distance separation, thereby conserving temporal separation regardless of headwind. The time based spacing separation requirements are given in the following table (2 separation schemes were considered, a conservative estimate and an optimistic estimate): Table 3: TBS Separation Requirements TBS Separation Requirements (sec) Distance Separation (Nm) Conservative Optimistic FINAL Page 6

22 2 Calculating Benefit from ATC-Wake Given the limited knowledge of meteorological parameters available for this study, the criteria for ATC-Wake employment had to be based on surface winds. Therefore, the benefit study for ATC-Wake is based on a surface crosswind component criterion for arrivals. It should also be noted that, while reduced separations on departure is also an aim of the ATC-Wake project, this aspect has not been considered in this study. However, since the employment of such a scheme would be similar to what is being proposed under CREDOS, the results shown in Section 3 give an indication of the benefit that this feature of ATC-Wake could provide. 2.1 Method The general method employed for predicting benefits from ATC-Wake was to firstly identify the hours during which the traffic was sufficient to indicate that there would be a demand for extra capacity (hours where this is true are referred to as Queued Hours ). Then for these hours, the number of arrivals that could be accommodated given the average separation requirements for that hour and typical ground speeds at the separation threshold was calculated. Finally, based on a predicted separation under ATC-Wake and the likely fraction of the hour during which time ATC-Wake could be employed, the number of arrivals that could be accommodated under ATC-Wake was calculated. From this the number of extra arrivals was deduced for each hour, and for each season. The following sections explain the process in more detail. It should be noted that the benefit calculated in this study will not equate to an actual number of forecast extra movements. Rather, it illustrates the difference between how many aircraft could be delivered under current operations and how many would be able to be delivered if, when certain surface weather conditions exist, all aircraft pairs were separated by 2.5Nm or 3Nm. It is intended that the figures presented in this study be viewed as a relative indication of benefit, and give nothing more than an order of magnitude of the benefit that could be achieved if ATC-Wake (or any other concept that takes advantage of crosswinds to reduce separations of inbound aircraft) was employed Raw Data Used For each airport: Hourly arrival counts split by aircraft type, for a week in each season (from CFMU): o Winter: 16 th 22 nd February 2004 o Spring: 3 rd 9 th May 2004 o Summer: 2 nd 8 th August 2004 o Autumn: 18 th 24 th October 2004 Seasonal hourly crosswind statistics, specifically; the percentage of that hour for which the crosswind exceeded 6 knots for at least 2 consecutive METARs FINAL Page 7

23 and the visibility was no less than 1km. The data came from 2 years ( ) of METARs, and crosswind components were analysed on each arrival runway Estimating Pair Mix The subsequent calculations require knowledge of the frequency of the various pair permutations (e.g. Heavy-Heavy, Heavy-Medium, etc). Since the data extracted from the CFMU contains only aircraft type frequencies the actual sequence needed to be estimated. A number of different methods of doing this were considered: Optimised sequence: in this case the aircraft are sequenced in ascending order of size, i.e. all the Lights, followed by all the Mediums and finally all the Heavies. Random sequence: in this case the, the probability of delivering a given pair is equal to the product of the probabilities of the two types of aircraft, e.g. %H-H =%H * %H While the Optimised sequence was dismissed as being impossible for controllers to implement, it was decided that there was some level of sequencing being achieved by controllers. Therefore a compromise between the 2 methods was sought. Using runway logs from the UK airports it was possible to test candidate methods against actual figures. The best method tested was a Quasi-random method in which it was assumed that a quarter of Heavy aircraft were able to be sequenced into Heavy-Heavy pairs, and that the rest of the aircraft (including the remaining Heavy aircraft) were randomly sequenced. A comparison between the Quasi-random method s predictions and the actual figures for Heathrow, Gatwick and Manchester is given in Appendix Converting Total Movement Counts into Runway Counts For airports where arrivals are spread over more than one runway, care needs to be taken to adjust the total arrival counts extracted from the CFMU. Referral to Table 2, reveals 4 airports where there are 2 arrival runways: LFPG, EDDM, EHAM, and LIRF (EDDF is not included because the 2 runways are closely-spaced and hence, for the purposes of this study, are treated as one). The details of how the CFMU figures were scaled are given below: LFPG & EDDM: In both cases arrivals were assumed to be randomly and equally spread over the 2 runways. Therefore, the arrival figures were halved to reflect this. This then allows the benefit to be calculated per runway (the overall benefit will be the sum of the benefit available on each runway). EHAM: Arrivals are spread over 1 or 2 runways depending on whether the airport is operating under an arrival peak or a departure peak (see Section 1.1). The FINAL Page 8

24 CFMU data and the METARs for EHAM were examined to determine what the configuration was likely to be for each hour of the day: o Arrival Peak or Departure Peak: If for a given hour of the day, there were more arrivals than departures then that hour was deemed to be an arrival peak, and vice versa. o Preferred or Alternate Configuration: Since arrivals could use the 18/36 parallel runways or the 06/24 runway, it was not sufficient to consider just the tailwind on one of the runways. Instead, the criterion for use of the alternate configuration (Southerly Operations) was that the average of the tailwind component on 36 and 06 was greater than 10 knots. Combining the 2 pieces of information above, it was possible to deduce for each hour of the day, whether or not arrivals were spread over 1 or 2 runways, and for each runway, the probability that the crosswind criterion was met and that that runway was in use at the time (dependent upon whether the preferred or alternate configuration was in use). Samples from each season were analysed to generate results for each season. LIRF: In the preferred mode of operation inbound aircraft land on 2 runways. However, when the Northerly wind component exceeds 10 knots, aircraft can use only one of the runways for landing. Therefore, analysis was performed for both the preferred mode of operation and the alternative mode of operation. For the preferred mode, the arrival figures were halved to reflect the fact that arrivals are spread over 2 runways. The METARs for LIRF were examined to determine which mode of operation was likely to be in use, for a given hour of the day in a given season Determining Hours where there is a Demand for Extra Capacity ( Queued Hours ) In order to establish whether there was a demand for the increased throughput that ATC-Wake could generate, an abstract concept, queuedness, was employed. It is intended that this concept would identify those hours where not only is the airport operating close to its capacity (i.e. aircraft are put in a queue) but that the queued aircraft are necessarily separated close to their minimum separation requirement. To determine whether an hour is queued, the sum of the separation requirements is compared to the separation available in that hour if it exceeds 80% of the separation available then the hour is deemed to be Queued. Since separation requirements for inbound aircraft are distance-based it is necessary to convert an hour into an equivalent distance. To do this, the ground speed of aircraft must be estimated: For UK airports, where separations are enforced until 4Nm to touchdown the ground speed was assumed to be 150 knots. FINAL Page 9

25 For the remaining European airports, where separations are enforced to touchdown, the ground speed was assumed to be 130 knots (typical landing speed of aircraft) Therefore, there is 150 Nm of separation available for UK airports, and 130 Nm of separation available at European airports. It is worth noting that this implies that UK airports can accommodate, for example, 5 more Heavy-Heavy pairs (separated at their minimum separation requirement) an hour than other European airports. When calculating the sum of the separation requirements, some allowance was included for imperfect spacing. Thus a new term was introduced, Attainable Spacing : Attainable Spacing = Spacing Requirement Nm (The separation standards for UK and ICAO schemes is given in Appendix 2) Thus, if, for a given hour: The (estimated) percentage of an aircraft with wake vortex category, i, leading an aircraft with wake vortex, j, is P ij The minimum required separation between an aircraft with wake vortex category, i, leading an aircraft with wake vortex, j, is Sep ij The number of arrivals in that hour (on a given runway), is A Then, Attainable Spacing = Sep ij Nm And, therefore, the sum of the separation requirements, S, is: S = A Pij ij + i, j ( Sep 0.25Nm) Calculating Theoretical Capacity under Current Operations The theoretical capacity under current operations is essentially the number of arrivals the runway can sustain, if the aircraft are separated at their average attainable separation. To calculate this, the following method was used: First, the average separation requirement was calculated based on the traffic mix: Average Separation = P ij Sep ij i, j Therefore the Average Attainable Separation, AAS, is given by the following equation: FINAL Page 10

26 AAS = P Sep i, j ij ij Nm Finally, if the separation available in any one hour (see Paragraph 2.1.4) is S HOUR, then the Theoretical Capacity under Current Ops, TC COPs, is given by: TC COPs = S HOUR /AAS Calculating Theoretical Capacity under ATC-Wake To calculate the maximum number of arrivals that can be accommodated per hour under ATC-Wake, it is assumed that whenever beneficial conditions exist (in this case a crosswind component > 6kts) ATC-Wake is implemented. Therefore the hour is split into the fraction of time where aircraft are separated by the ATC-Wake separation requirement, Sep ATC-Wake, (plus 0.25Nm) and the remainder, when they will be separated at the Average Attainable Separation, AAS, (calculated in Section 2.1.5). If the proportion of a given hour during which the meteorological criteria are satisfied is M, and the separation available in that hour is S HOUR, then: The spacing available for the ATC-Wake period = M*S HOUR For the fraction of the hour where ATC-Wake is employed the number of arrivals that can be accommodated is calculated by the following formula: TC ATC Wake = ( Sep M * S ATC Wake HOUR Nm) For the fraction of the hour when the meteorological criteria are not satisfied, the number of arrivals that can be accommodated is calculated by the following formula: TC COPs (1 M ) * S = ( AAS) HOUR Finally, the total throughput, TC TOTAL, is: TC TOTAL = TC ATC-Wake + TC COPs FINAL Page 11

27 2.1.7 Calculating the Benefit Finally, the benefit is defined as the number of extra movements possible with the introduction of ATC-Wake, and is summarised by Season and by Year, i.e. the Benefit is the difference between and Worked Example Say for a given hour of the day, season, and airport: The Percentage of H-H pairs (P HH ) is 40%, and the percentage of H-M (P HM ) pairs is 25%. The separation requirement for H-H pairs (Sep HH ) is 4Nm, and 5Nm for H-M Pairs (Sep HM ), and 3Nm for everything else (Sep STD ). The separation available in that hour (S HOUR ) is 130Nm The number of arrivals in that hour (A) is 28 The Tolerance (T), is 0.25Nm ATC-Wake Separation requirement is 3Nm The percentage of the hour during which the meteorological criteria are met (M) is 30% Then, the sum of the separation, S, in that hour is given by: S = A*P HH *(Sep HH + T) + A*P HM *(Sep HM + T) + A*(1 - P HH - P HM )*(Sep STD + T) = 28*{0.4*(4+0.25) *(5+0.25) *(3+0.25)} = 116 Nm This represents 116/130 = 89% of the hour. Therefore that hour is defined as being Queued. To calculate the theoretical capacity under current operations, TC COPs, one has to first calculate the Average Separation requirement: Average Separation Requirement = P HH *Sep HH + P HM *Sep HM + (1-P HH -P HM )*Sep SID = 0.4* * *3 = 3.9 Nm Therefore, the Average Attainable Separation (AAS) is : AAS = Average Separation Requirement + Tolerance = = 4.15 Nm The theoretical capacity under current operations is the number of arrivals that can be accommodated if every arrival is spaced at the Average Attainable Spacing and is given by: TC COPs = S HOUR /AAS = 130/4.15 = 31 FINAL Page 12

28 The theoretical capacity under ATC-Wake, TC TOTAL, is given by: TC TOTAL = M*S HOUR /(Sep ATC-Wake + T) + (1-M)* S HOUR /AAS = 0.3*130/(3+0.25) + 0.7*130/(4.15) = 34 Therefore the Benefit possible from that hour is 3 extra movements (TC TOTAL TC COPs ) per hour, or 273 movements over the season. 2.2 Assumptions 1. Pair Mix. It was assumed that 25% of Heavies were sequenced into Heavy- Heavy pairs, and all other aircraft were randomly sequenced. 2. Ground Speeds. It was assumed that the ground speed of aircraft at the separation threshold (the last point on approach at which separations are enforced) is 150 knots at UK airports and130 knots at other European airports. 3. Attainable Separation. It is assumed that controllers can separate aircraft to within 0.25Nm of the minimum separation requirement (spacing below the IFR separation minima is not considered in this study). 4. Queued Hours. It was assumed that benefit would only be realised if the traffic satisfied the criteria to be queued. 5. The (time) spacing distribution at the separation threshold is maintained to touchdown (i.e. catch-up and pull-away have been ignored). 6. ATC-Wake. a. The conditions under which ATC-Wake can be employed are a surface crosswind component of at least 6 knots for at least 2 consecutive METARs and a visibility of at least 1km. b. Whenever the criteria above are met, ATC-Wake is employed. c. Under ATC-Wake, all aircraft have a minimum separation requirement of either 2.5Nm (optimistic estimate) or 3Nm (conservative estimate). FINAL Page 13

29 2.3 Results ATC-Wake = 2.5Nm Table 4: Potential Benefit at Candidate Airports under ATC-Wake (ATC-Wake Separation = 2.5Nm) Extra Movements per Day Possible under ATC-Wake (number of Queued Hours per day) Airport Winter Spring Summer Autumn Annual Total EGLL 73 (16) 83 (16) 64 (16) 68 (16) EDDF 41 (13) 31 (15) 23 (14) 29 (15) EHAM 7 (4) 15 (9) 17 (11) 22 (11) 5565 LEMD 10 (9) 11 (9) 20 (12) 10 (10) 4653 LFPG 0 (0) 14 (2) 3 (1) 4 (1) 1916 LSZH 2 (2) 1 (2) 0 (2) 1 (2) 365 EDDM 0 (0) 0 (0) 0 (0) 0 (0) 0 LIRF 0 (1) 0 (2) 0 (4) 0 (4) 0 LEBL 0 (0) 0 (0) 0 (0) 0 (0) 0 EGKK 0 (0) 0 (0) 0 (0) 0 (0) 0 EGCC 0 (0) 0 (0) 0 (0) 0 (0) 0 FINAL Page 14

30 2.3.2 ATC-Wake = 3Nm Table 5: Potential Benefit at Candidate Airports under ATC-Wake (ATC-Wake Separation = 3Nm) Extra Movements per Day Possible under ATC- Wake (number of Queued Hours per day) Airport Winter Spring Summer Autumn Annual Total EGLL 30 (16) 34 (16) 27 (16) 28 (16) EDDF 14 (13) 11 (15) 8 (14) 10 (15) 3923 EHAM 1 (4) 3 (9) 4 (11) 6 (11) 1277 LFPG 0 (0) 5 (2) 1 (1) 1 (1) 638 LEMD 2 (9) 1 (9) 2 (12) 1 (10) 547 EDDM 0 (0) 0 (0) 0 (0) 0 (0) 0 LIRF 0 (1) 0 (2) 0 (4) 0 (4) 0 LSZH 0 (2) 0 (2) 0 (2) 0 (2) 0 LEBL 0 (0) 0 (0) 0 (0) 0 (0) 0 EGKK 0 (0) 0 (0) 0 (0) 0 (0) 0 EGCC 0 (0) 0 (0) 0 (0) 0 (0) Discussion of Results 1. GENERAL: Whether the ATC-Wake separation is 3Nm or 2.5Nm can make a significant difference in the potential benefit up to 8 times as many movements per year under 2.5Nm compared to 3Nm. This is not surprising since under 2.5Nm, every pair (not just WV pairs) have a smaller separation requirement. 2. EGLL A high frequency of queued hours (approximately 16 hours per day), high percentage of Heavy aircraft and high frequency of crosswind > 6kts (significantly higher than at EDDF) combine to give the highest benefit FINAL Page 15

31 estimation of the candidate airports. 3. EDDF A high frequency of queued hours (approx 14 hours per day), high percentage of Heavy aircraft and fairly high frequency of crosswind > 6kts combine to give the second highest benefit estimation of the candidate airports. 4. EHAM The majority of queued hours occurred during a departure peak (see Section 1.1) where all arrivals land on one runway. During these hours the potential benefits are high. There are a number of queued hours where no benefit arises this is where the runway would have been queued in a certain configuration (for example under a departure peak, in the alternate configuration), but the combined probability of there being a crosswind greater than 6 knots and the alternate configuration being employed is so low that no benefit is expected. 5. LFPG Even with the arrivals spread over 2 runways (it is assumed they are spread equally and randomly i.e. 50% on each) there are still a number of queued hours in the day, resulting in about 2 extra movements possible per day (in the case where ATC-Wake separation is 3Nm), per runway, in spring. In other months queued hours correspond with hours of the day where the crosswind is rarely greater than 6kts, and hence no benefit is predicted. 6. LEMD LEMD has a high frequency of queued hours, but only 1 or 2 extra movements possible (in the case where ATC-Wake separation is 3Nm). This is because the period of the day where the probability of crosswinds exceeding 6kts is the greatest (the afternoon/evening) corresponds to periods of the day where there are only a small percentage of Heavy aircraft. 7. LSZH Queued hours tend to correspond to hours of the day where the crosswind is rarely greater than 6kts. There are in general few occasions where the crosswind component exceeds 6kts at LSZH. 8. LIRF The only occasions where traffic is queued at LIRF, is when the wind is such that the alternate configuration, where all arrivals land on one runway, is employed (for more details see Section 1.1). However, the combined probability of there being a crosswind greater than 6 knots and the alternate configuration being employed is so low that no benefit is expected. 9. EDDM No queued hours were identified. This is due to the arrivals being split over 2 runways which means neither runway sustains enough arrivals for it to be queued. However, if all arrivals landed on 1 runway, there would still be no benefit (despite an average of 8 queued hours per day) because of the rarity with which the crosswind exceeds 6 knots. FINAL Page 16

32 10. LEBL/EGCC/EGKK There were no queued hours identified due to a combination of insufficient traffic volume and small frequency of Heavy aircraft. 2.4 Parameter Sensitivity Sequencing The benefit calculations were repeated for a number of different estimates of the fraction of Heavy aircraft that are believed to be sequenced. 0% is equivalent to a purely random sequence. Table 6 shows the effect of varying this parameter: Table 6: Annual Benefit Estimates for different Sequencing Estimates (red (middle) column refers to the parameter value used in the actual benefit calculation, ATC-Wake Separation = 3Nm) Annual Benefit for different Sequencing estimates Airport 0% 25% 50% EGLL EDDF EHAM LFPG LEMD EDDM LIRF LSZH LEBL EGKK EGCC Clearly, there is little difference in the benefit estimation as different sequencing models are used. There is a small decrease in the benefit as more of the Heavy aircraft FINAL Page 17

33 are sequenced optimally, since this reduces the average separation and therefore the difference between current operations and ATC-Wake operations Queued Criteria The benefit calculations were repeated for a number of different criteria for a runway to be queued. Table 7 shows the effect of varying this parameter: Table 7: Annual Benefit Estimates for different Queued criteria (red column refers to the parameter value used in the actual benefit calculation, ATC-Wake Separation = 3Nm) Annual Benefit for different Queued Criteria Airport 70% 80% 90% EGLL EDDF EHAM LFPG LEMD EDDM LIRF LSZH LEBL EGKK EGCC In this case, for the airports that are often queued at the 80% criteria, varying the criterion level doesn t make much of a difference to the annual benefit estimate, since virtually every peak hour is queued under all the values tested. However, for the airports where only a small portion of the day is defined as queued using 80% as the criterion, upon reducing the criterion more hours become queued and the potential benefit increases quite rapidly. FINAL Page 18

34 2.4.3 Tolerance The benefit calculations were repeated for a number of different criteria of tolerance estimates (i.e. the spacing margins to which controllers can work to). Table 8 shows the effect of varying this parameter: Table 8: Annual Benefit Estimates for different estimates of the Tolerance (red (middle) column refers to the parameter value used in the actual benefit calculation, ATC-Wake Separation = 3Nm) Annual Benefit for different Tolerance Estimates (Nm) Airport EGLL EDDF EHAM LFPG LEMD EDDM LIRF LSZH LEBL EGKK EGCC For the airports for which the runways are almost always queued (EGLL & EDDF), increasing the tolerance causes the benefit to fall as all the aircraft are now being separated by a greater amount, and the absolute difference between the capacity under current operations and ATC-Wake decreases. Whereas at LFPG the increase in tolerance meant that there was now more queued hours from which to gain benefit, and the estimated benefits rise quite sharply. Changing the tolerance estimates has little impact on the benefit estimates at EHAM and LEMD. The tolerance value of 0.25Nm was chosen after analysis of the separation distribution at EGLL revealed that the mode separation was close to 0.25Nm above the minimum separation requirement for pressured traffic. FINAL Page 19

35 2.5 Limitations 1. The meteorological criteria under which ATC-Wake is expected to be activated are a lot more complicated than is able to be analysed given just surface meteorological conditions. ATC-Wake relies on a wake vortex model, which takes into account atmospheric turbulence and other meteorological parameters that were out of the scope of this project. Another major limitation is that ATC-Wake will only be activated when the entire glideslope has appropriate meteorological conditions, rather than just a surface criterion. 2. Many airports operate reduced separation procedures under certain conditions which will allow them to achieve a throughput greater than the TC COPs (Theoretical Capacity under Current Ops) calculated in this study. 3. Controller sequencing may be better than the 25% assumed in this study. The closer to an optimised sequence the controllers can achieve, the smaller the average separation between aircraft and the less benefit that will be achieved under ATC-Wake. 4. This method does not take into account the rich spectrum of aircraft behaviour, in terms of landing speeds, deceleration profiles and conformance to speed instructions. This could impact upon the throughput, by, for example, requiring that certain aircraft pairs be given additional spacing to take into account catch-up over final approach. 3 Calculating Benefit from CREDOS Given the limited knowledge of meteorological parameters available for this study, the criteria for CREDOS employment had to be based on surface winds. Therefore, the benefit study for CREDOS is based on surface crosswind component criteria for departures. 3.1 Method The general method employed for predicting benefits from CREDOS was to firstly identify the hours during which the traffic was sufficient to indicate that there would be a demand for extra capacity (hours where this is true are referred to as Queued Hours ). Then for these hours, the number of departures that could be accommodated given the average separation requirements for that hour was calculated. Finally, based on a predicted separation under CREDOS and the likely fraction of the hour during which time CREDOS could be employed, the number of departures that could be accommodated under CREDOS was calculated. From this, the number of extra FINAL Page 20

36 departures was deduced for each hour, and for each season. The following sections explain the process in more detail. It should be noted that the benefit calculated in this study will not equate to an actual number of forecast extra movements. Rather, it illustrates the difference between how many aircraft could be delivered under current operations and how many would be able to be delivered if, when certain surface weather conditions exist, all aircraft pairs were separated at the reduced separation requirement. It is intended that the figures presented in this study be viewed as a relative indication of benefit, and give nothing more than an order of magnitude of the benefit that could be achieved if CREDOS (or any other concept that takes advantage of crosswinds to reduce separations for outbound aircraft) was employed Raw Data Used Hourly departure counts split by aircraft type, for a week in each season (from CFMU): o Winter: 16 th 22 nd February 2004 o Spring: 3 rd 9 th May 2004 o Summer: 2 nd 8 th August 2004 o Autumn: 18 th 24 th October 2004 Seasonal hourly crosswind statistics, specifically; the percentage of that hour for which the crosswind exceeded 6 knots for at least 2 consecutive METARs and the visibility was no less than 1km. The data came from 2 years ( ) of METARs, and crosswind components were analysed on each departure runway Estimating Pair Mix This was done according to the method described in Paragraph Empirical evidence from the UK airports showed the 25% optimised method to be applicable to departure sequences as well as arrival sequences for more details see Appendix Converting Total Movement Counts into Runway Counts For airports where departures are spread over more than one runway, care needs to be taken to adjust the total departure counts extracted from the CFMU. Referral to Table 2, reveals 4 airports where there are 2 departure runways: LFPG, EDDM, EDDF and EHAM. In addition, at LIRF, departures can use one of 2 different non-parallel runways, and since crosswind statistics will depend on the runway orientation additional work had to be done here. The details of how the CFMU figures were scaled are given below: LFPG & EDDM: FINAL Page 21

37 In both cases departures were assumed to be randomly and equally spread over the 2 runways. Therefore, the departure figures were halved to reflect this. This then allows the benefit to be calculated per runway (the overall benefit will be the sum of the benefit available on each runway). EHAM: Departures are spread over 1 or 2 runways depending on whether the airport is operating under an arrival peak or a departure peak (see Section 1.1). The CFMU data and the METARs for EHAM were examined to determine what the configuration was likely to be for each hour of the day: o Arrival Peak or Departure Peak: If for a given hour of the day, there were more arrivals than departures then that hour was deemed to be an arrival peak, and vice versa. o Preferred or Alternate Configuration: Since departures could use the 18/36 parallel runways or the 06/24 runway, it was not sufficient to consider just the tailwind on one of the runways. Instead, the criterion for use of the alternate configuration (Southerly Operations) was that the average of the tailwind component on 36 and 06 was greater than 10 knots. Combining the 2 pieces of information above, it was possible to deduce for each hour of the day, whether or not departures were spread over 1 or 2 runways, and for each runway, the probability that the crosswind criterion was met and that that runway was in use at the time (dependent upon whether the preferred or alternate configuration was in use). Samples from each season were analysed to generate results for each season. LIRF: In the preferred mode of operation outbound aircraft take off on runway 25. However, when the Northerly wind component exceeds 10 knots, departing aircraft have to use runway 34L. Therefore, analysis was performed for both the preferred mode of operation and the alternative mode of operation. The METARs for LIRF were revisited to determine which mode of operation was likely to be in use, for a given hour of the day in a given season Departure Separation Standards For departing aircraft there are 3 different separation requirements based on the aircraft types and the departure routes: Wake Vortex Separation. The minimum separation requirements for wake vortex purposes are given in Appendix 3. Because Light aircraft rarely feature at the candidate airports, the only pair that require wake vortex separation is a Heavy leading Medium FINAL Page 22

38 (intersection take-offs were not considered in this study). SID Separation. For aircraft departing on the same or similar SID (Standard Instrument Departure), separation is required to ensure that the aircraft are appropriately separated once they leave the Airport Control Zone. This separation can be 60s, 120s, or 180s depending on how similar the departure routes are. Speed Group Separation. Aircraft are classified into Speed Groups that are based on typical speeds on departure. If the leader falls into a slower speed group than the follower aircraft then extra spacing is required. However, this is generally only applicable to occasions when the leading aircraft is Light, and as a result has not been considered in this study. The actual separation requirement is determined according to the following formula: Departure Separation = MAX(WV Sep, SID Sep) + Speed Group Sep For the calculations it is necessary to estimate an Average SID separation i.e. the average separation for a pair of aircraft with no wake vortex separation. No information with which to base this estimate was available for the non-uk airports, but the results from Heathrow indicate that: SID separation is very rarely 180s The Average SID separation is 80s The Average SID separation will depend upon the number of SIDs available to departing aircraft the more SIDs there are the more likely it is that the controller will be able to sequence aircraft so that the SID separations are minimised. All the candidate airports would appear to be big enough to ensure that the average SID separation should not differ drastically from Heathrow and without any further data available at this stage the Heathrow figure of 80s was employed for all airports Determining Hours where there is a Demand for Extra Capacity ( Queued Hours ) The same queued concept that was used for ATC-Wake (see paragraph 2.1.4) was also adopted for CREDOS an hour is defined as being queued if the sum of the separation requirements exceeds 80% of the separation available. Since, on departure, aircraft separation requirements are given in terms of time, this is equivalent to requiring that the sum of the separation requirements in any given hour must exceed 48 minutes. FINAL Page 23

39 When calculating the sum of the separation requirements, some allowance was included for imperfect spacing. Thus a new term was introduced, Attainable Spacing : Attainable Spacing = Spacing Requirement + 10s As discussed in Paragraph the wake vortex pairs (i.e. Heavy-Medium) have an assumed separation requirement of 120s, whilst all other pairs are separated at the Average SID separation (80s). Thus, if, for a given hour: The (estimated) percentage of an aircraft with wake vortex category, i, leading an aircraft with wake vortex, j, is P ij The minimum required separation between an aircraft with wake vortex category, i, leading an aircraft with wake vortex, j, is Sep ij The number of departures in that hour (on a given runway), is D Then, Attainable Spacing = Sep ij + 10s And, therefore, the sum of the separation requirements, S, is: ( Sep 10 s) S = D Pij ij + i, j Calculating Theoretical Capacity under Current Operations The theoretical capacity under current operations is essentially the number of departures the runway can sustain, if the aircraft are separated at their average attainable separation. To calculate this, the following method was used: First, the average separation requirement was calculated based on the traffic mix: Average Separation = P ij Sep ij i, j Therefore the Average Attainable Separation, AAS, is given by the following equation: AAS = P Sep ij ij + 10s i, j Finally, the Theoretical Capacity under Current Ops, TC COPs, is given by: FINAL Page 24

40 TC COPs = (seconds in an hour)/aas = 3600/AAS Calculating Theoretical Capacity under CREDOS To calculate the maximum number of departures that can be accommodated per hour under CREDOS, it is assumed that whenever beneficial conditions exist (in this case a crosswind component > 6kts) CREDOS is implemented. Therefore the hour is split into the fraction of time where CREDOS is employed and aircraft are separated by the CREDOS separation requirement Sep CREDOS, (plus 10 seconds) and the remainder, when they will be separated at the Average Attainable Separation (calculated in Section 3.1.6). If the proportion of a given hour during which the meteorological criteria are satisfied is M, then: the spacing available for the CREDOS period = (M*3600) seconds For the fraction of the hour where CREDOS is employed the number of departures that can be accommodated is calculated by the following formula: M * 3600 TCCREDOS = ( SepCREDOS + 10s) In the case where the wake vortex separation requirement is 60 seconds, Sep CREDOS is equivalent to the Average SID Separation, since the SID separation requirement will always be as big, or bigger, than the WV Separation requirement. i.e.: TC M * 3600 = CREDOS ( AverageSIDSeparation + 10s) For the fraction of the hour when the meteorological criteria are not satisfied, the number of departures that can be accommodated is calculated by the following formula: Finally, the total throughput, TC TOTAL, is: (1 M )*3600 TC COPs = ( AAS) TC TOTAL = TC CREDOS + TC COPs Calculating the Benefit FINAL Page 25

41 Finally, the benefit is defined as the number of extra movements possible with the introduction of CREDOS, and is summarised by season and by year. i.e. the Benefit is the difference between and Worked Example: Say for a given hour of the day, season, and airport: The percentage of H-M pairs (P HM ) is 20% The number of departures in that hour (D) is 35 The separation requirement for H-M pairs (Sep HM ) is 120s, and 80s for all else (Sep SID ) The Tolerance (T), is 10s CREDOS Separation is 80s The percentage of the hour during which the meteorological criteria are met (M) is 30% Then, the sum of the separation, S, in that hour is given by: S = D*P HM *(Sep HM + T) + D*(1-P HM )*(Sep SID + T) = 35*{0.2*(120+10) + 0.8*(80+10)} = 3430 seconds This represents 3430/3600 = 95% of the hour. Therefore that hour is defined as being Queued. To calculate the theoretical capacity under current operations, TC COPs, one has to first calculate the Average Separation requirement: Average Separation Requirement = P HM *Sep HM + (1-P HM )*Sep SID = 0.2* *80 = 88 seconds Therefore, the Average Attainable Separation (AAS) is : AAS = Average Separation Requirement + Tolerance = = 98 seconds The theoretical capacity under current operations is the number of departures that can be accommodated if every departure is spaced at the Average Attainable Spacing and is given by: TC COPs = 3600/AAS = 3600/98 = 37 The theoretical capacity under CREDOS, TC TOTAL, is given by: TC TOTAL = M*3600/(Sep CREDOS + T) + (1-M)*3600/AAS = 0.3*3600/(80+10) + 0.7*3600/(98) = 38 FINAL Page 26

42 Therefore the Benefit possible from that hour is 1 extra movement (TC CREDOS TC COPs ) per hour, or 91 movements over the season. FINAL Page 27

43 3.2 Assumptions 1. Pair Mix. It was assumed that 25% of Heavies were sequenced into Heavy- Heavy pairs, and all other aircraft were randomly sequenced. 2. Separations. It was assumed that all non-wake vortex pairs had a separation requirement of 80 seconds (the assumed average SID separation), and that all wake vortex pairs had a separation requirement of 120 seconds. 3. Attainable Separation. It is assumed that controllers can separate aircraft to within 10 seconds of the minimum separation requirement. 4. Queued Hours. It was assumed that benefit would only be realised if the traffic was such that it satisfied the criteria to be queued. 5. CREDOS. a. The conditions under which CREDOS can be employed are a surface crosswind component of at least 6 knots for at least 2 consecutive METARs and a visibility of at least 1km. b. Whenever the criteria above are met, CREDOS is employed. c. Under CREDOS, all aircraft have a minimum separation requirement of either 80s (optimistic estimate; equivalent to the average SID separation) or 90s (conservative estimate). FINAL Page 28

44 3.3 Results CREDOS Table 9: Potential Benefit at Candidate Airports under CREDOS (CREDOS Separation = Average SID Separation (80s)) Extra Movements per Day Possible under CREDOS (number of Queued Hours per day) Airport Winter Spring Summer Autumn Annual Total EGLL 25 (16) 30 (16) 25 (16) 24 (16) 9490 EHAM 0 (2) 2 (7) 0 (2) 5 (9) 638 LEMD 1 (8) 1 (10) 2 (10) 1 (11) 456 EDDF 0 (1) 0 (0) 0 (0) 1 (1) 91 EDDM 0 (0) 0 (0) 0 (0) 0 (0) 0 LIRF 0 (3) 0 (3) 0 (3) 0 (4) 0 LFPG 0 (0) 0 (0) 0 (0) 0 (0) 0 LSZH 0 (1) 0 (1) 0 (1) 0 (2) 0 LEBL 0 (0) 0 (0) 0 (0) 0 (0) 0 EGKK 0 (0) 0 (0) 0 (0) 0 (0) 0 EGCC 0 (0) 0 (1) 0 (1) 0 (1) 0 FINAL Page 29

45 Table 10: Potential Benefit at Candidate Airports under CREDOS (CREDOS Separation = 90s) Extra Movements per Day Possible under CREDOS (number of Queued Hours per day) Airport Winter Spring Summer Autumn Annual Total EGLL 18 (16) 22 (16) 18 (16) 17 (16) 6843 EHAM 0 (1) 2 (3) 0 (1) 4 (4) 547 LEMD 0 (8) 1 (10) 1 (10) 1 (11) 273 EDDF 0 (1) 0 (0) 0 (0) 0 (1) 0 EDDM 0 (0) 0 (0) 0 (0) 0 (0) 0 LIRF 0 (3) 0 (3) 0 (3) 0 (4) 0 LFPG 0 (0) 0 (0) 0 (0) 0 (0) 0 LSZH 0 (1) 0 (1) 0 (1) 0 (2) 0 LEBL 0 (0) 0 (0) 0 (0) 0 (0) 0 EGKK 0 (0) 0 (0) 0 (0) 0 (0) 0 EGCC 0 (0) 0 (1) 0 (1) 0 (1) 0 FINAL Page 30

46 3.3.2 Discussion of Results 1. GENERAL: There are less queued hours for departures than arrivals. This is because there are fewer wake vortex pairs on departures (H-H pairs do not require WV separation), and the equivalent time separation for 3Nm separated arrivals at 130kts, 83s, is greater than the assumed average departure separation for non- WV pairs (80s). There is little difference between the frequency of queued hours at UK airports because the aircraft are moving faster at the spacing threshold and so the equivalent time separation for non-wv pairs on arrival is lower (~70s). Overall it is more difficult to derive benefit on departure because there is only one WV category pair that is affected: Heavy leading Medium. 2. OPTIMISTIC vs CONSERVATIVE The choice of CREDOS separation requirement will influence the amount of benefit that would result. Clearly, the smaller the difference between the CREDOS separation requirement and the WV separation requirement under current operations, the smaller the benefit will be. While this is reflected in the results presented in the previous section, the difference in benefit estimates is not as noticeable as in ATC-Wake. 3. EGLL A high frequency of queued hours (approx 16 hours per day), high percentage of Heavy aircraft and high frequency of crosswind > 6kts combine to give the highest benefit estimation of the candidate airports. 4. EHAM The majority of queued hours occurred during an arrival peak (see Section 1.1) where all departures take-off from one runway. During these hours the potential benefits are high. There are a number of queued hours where no benefit arises this is where the runway would have been queued in a certain configuration (for example under an arrival peak, in the alternate configuration), but the combined probability of there being a crosswind greater than 6 knots and the alternate configuration being employed is so low that no benefit is expected. 5. LEMD Madrid Barajas has a high frequency of queued hours, but only 1 or 2 extra movements possible. This is because the period of the day where the probability of crosswinds exceeding 6kts is the greatest (the afternoon/evening) corresponds to periods of the day where there are only a small percentage of Heavy aircraft. 6. EDDF The departures are split over 2 runways (~60% use runway 18). As a result, there are very few hours where departures are queued on runway 18. The choice of CREDOS separation is the difference between EDDF expecting 1 extra movement a day in Autumn and no extra movements. FINAL Page 31

47 7. LSZH Zurich effectively segregate their departures on 2 runways, one taking heavy s and the other taking the rest. As a result, there will be very few WV separated departure pairs and so CREDOS was not considered a viable option for the airport 8. LIRF Despite a number of queued hours, there are not enough Heavy aircraft for CREDOS to have anything more than a negligible impact. 9. EGCC Queued hours correspond to periods of low crosswind and low numbers of Heavy aircraft as a result there is no noticeable benefit predicted to result from CREDOS. 10. EDDM No queued hours were identified. This is due to the departures being split over 2 runways which means neither runway sustains enough departures for it to be queued. In any case, the crosswind component rarely exceeds 6 kts at Munich. 11. LFPG/LEBL/EGKK There were no queued hours identified due to a combination of insufficient traffic volume and small frequency of Heavy aircraft. FINAL Page 32

48 3.4 Parameter Sensitivity Sequencing The benefit calculations were repeated for a number of different estimates of the fraction of Heavy aircraft that are believed to be sequenced. 0% is equivalent to a purely random sequence. Table 11 shows the effect of varying this parameter: Table 11: Annual Benefit Estimates for different Sequencing Estimates (red (middle) column refers to the parameter value used in the actual benefit calculation) Annual Benefit for different Sequencing Estimates Airport 0% 25% 50% EGLL EHAM LEMD EDDF EDDM LIRF LFPG LSZH LEBL EGKK EGCC For EHAM, LEMD, and EDDF, where there were a number of hours that only just met the criteria to be queued, altering the sequencing model parameters can produce fairly significant changes in the estimated benefit. If more Heavy aircraft are sequenced, then the average separation decreases and the likelihood of an hour being queued decreases, and vice-versa. For EGLL where the hours that are queued easily satisfy the criteria to be queued, the minor fluctuations caused by altering the sequence estimates have no noticeable impact on the amount of benefit predicted. FINAL Page 33

49 3.4.2 Queued Criteria The benefit calculations were repeated for a number of different criteria for a runway to be queued. Table 12 shows the effect of varying this parameter: Table 12: Annual Benefit Estimates for different Queued criteria (red (middle) column refers to the parameter value used in the actual benefit calculation) Annual Benefit for different Queued Criteria Airport 70% 80% 90% EGLL EHAM LEMD EDDF EDDM LIRF LFPG LSZH LEBL EGKK EGCC In this case, for the airports that are often queued at the 80% criteria, varying the criterion level doesn t make much of a difference to the annual benefit estimate, since virtually every peak hour is queued under all the values tested. However, for the airports where only a small portion of the day is defined as queued using 80% as the criterion, upon reducing the criterion more hours become queued and the potential benefit increases quite rapidly. In fact, if using 70% of the spacing available qualifies a runway as being queued, then, airports where at the 80% level showed no benefit at all now show significant benefit (LIRF, LFPG, EGKK, EGCC). Clearly, for some airports the choice of the queued criterion will make a significant difference to the amount of benefit predicted. The decision on what criterion to use had to be, to some extent, arbitrary since the relationship between traffic quantity and whether or not an aircraft will have to queue to arrive or depart an airport is not known. It is also recognised that this relationship may well be different at different FINAL Page 34

50 airports. Whilst for this study, 80% was chosen as a reasonable criterion, Table 12 serves as a reminder that potential benefit will depend heavily on whether there is the demand to take advantage of the extra movements Tolerance The benefit calculations were repeated for a number of different criteria of tolerance estimates (i.e. the spacing margins to which controllers can work to). Table 13 shows the effect of varying this parameter: Table 13: Annual Benefit Estimates for different estimates of the Tolerance (red (middle) column refers to the parameter value used in the actual benefit calculation) Annual Benefit for different Tolerance estimates (seconds) Airport EGLL EHAM LEMD EDDF EDDM LIRF LFPG LSZH LEBL EGKK EGCC For the airports for which the runways are nearly always queued (EGLL), increasing the tolerance causes the benefit to fall as all the aircraft are now being separated by a greater amount, and the absolute difference between the capacity under current ops and ATC-Wake decreases. Whereas at EDDF, LFPG, LEMD & EHAM the increase in tolerance means that there are more queued hours from which to gain benefit and the estimated benefits rise quite sharply. FINAL Page 35

51 3.4.4 Average SID Separation The benefit calculations were repeated for a number of estimates of the average SID separation. Table 14 shows the effect of varying this parameter: Table 14: Annual Benefit Estimates for different estimates of the Average SID Separation (red (middle) column refers to the parameter value used in the actual benefit calculation) Annual benefits for different estimates of the Average SID Separation (seconds) Airport EGLL EHAM LEMD EDDF EDDM LIRF LFPG LSZH LEBL EGKK EGCC For EGLL, EHAM and LEMD, increasing the average SID separation decreases the benefit, since the time saved from abolishing wake vortex separation requirement decreases. However, at EDDF, the benefit actually increases as the average SID separation increases this is because increasing the SID separation led to more hours being classified as queued and as a result there were more occasions where benefit could be made. FINAL Page 36

52 3.5 Limitations 1. The meteorological criteria under which CREDOS is expected to be activated is a likely to be more complicated than simply surface met conditions. Any requirement for minimum crosswind levels at altitude will reduce the expected benefit. 2. Controller sequencing may be better than the 25% assumed in this study. The closer to an optimised sequence the controllers can achieve, the fewer pairs there will be that require WV Separation, and the less benefit that will be achieved under CREDOS. 3. The assumption that the average SID separation is 80 seconds relies on the other airports in question having a similar variety of SIDs. If this is not the case then the average SID separation is likely to be different and the benefit forecast will be different. FINAL Page 37

53 4 Calculating Benefit from Time-Based Spacing Unlike CREDOS and ATC-Wake, the aim of time-based spacing is not to gain extra capacity, but to recover capacity lost under periods of strong headwinds. Because of the present distance-based separation requirements, in periods of strong headwinds the reduction in aircraft ground speed brings about an increase in the time separation, as the aircraft take longer to cover the spacing distance. By switching to a time based spacing system it is hoped that the loss in aircraft ground speed will be compensated by a decreased distance separation, thereby conserving temporal separation regardless of headwind. 4.1 Method Initially, it was hoped to be able to measure empirically the effect of headwinds on throughput at each of the candidate airports by comparing METAR recorded headwind components with arrival rates. However, it proved impossible to deduce a correlation between the two that would allow the measurement of how many movements are lost due to headwinds. The reasons for the lack of correlation are probably a combination of an inability to resolve falls in arrival rate that were caused by headwinds and fluctuations due to other factors (e.g. lack of demand, delays caused by other factors) and the fact that surface winds are not necessarily representative of conditions aloft. To enable a calculation of benefit to be performed, a more theoretical approach was decided upon. Using traffic figures extracted from the CFMU, the effect of different strengths of headwind was predicted by assuming that the headwind caused the aircraft to decelerate as if they were maintaining a constant airspeed (i.e. in a 10 knot headwind, aircraft will lose 10 knots of ground speed). This was then used in conjunction with surface wind conditions to give an idea of what the actual loss of capacity could be over a typical year Predicting the Number of Lost Movements for a given Headwind As in Section 2.1.5, the Average Attainable Separation (AAS) was calculated for each hour of the day at the candidate airports: AAS = P Sep i, j ij ij Nm With the hourly separation available, S HOUR, as: 150Nm at UK airports, and 130Nm at other European airports FINAL Page 38

54 For a given headwind, H, the separation available in an hour will decrease according to (assuming that the headwind is sustained throughout the hour): S HOUR (H) = S HOUR H The Separation Required, S, is the hourly total separation required to be able to land the observed arrivals (see Paragraph 2.1.4), and is equivalent to the sum of the separation requirements in that hour. If, under a headwind (H), the separation required (S) exceeds the separation available (S HOUR ) then there will be a Spacing Deficiency and, under current rules, this would correspond to lost movements, which is seen as a delay. To calculate the number of lost movements for a given headwind, the spacing deficiency is divided by the average attainable separation, AAS, (see Paragraph 2.1.5): Lost Capacity, LC(H) = S - SHOUR ( H ) S - SHOUR + H = AAS AAS Therefore, LC(H) gives the number of movements that would not be able to accommodated if ICAO separations were applied in a headwind, H. This calculation was performed for a headwind of 15kts, 25kts and 35kts (these were chosen to correspond to the wind bands chosen for the meteorological analysis in WP2) Estimating the Number of Movements Lost in 2004 The figures generated from the method in Paragraph give an idea of the impact a headwind of a given level would be expected to have at each of the airports. The next task is to apply those figures to the weather profiles that were generated from the results of the meteorological analysis in WP2. By doing so, an idea of how many movements would be expected to have been lost in 2004 due to headwinds can be deduced. The relevant information available from WP2 is listed below: Seasonal hourly frequencies of time when the headwind component was between 10 and 20 knots Seasonal hourly frequencies of time when the headwind component was between 20 and 30 knots Seasonal hourly frequencies of time when the headwind component was greater than 30 knots To estimate the capacity lost in 2004 when headwinds were in one of the categories listed above, the number of movements predicted to be lost under a given headwind, FINAL Page 39

55 LC(H), was multiplied by the probability of experiencing that level of headwind, P(H): Capacity lost when Headwind was within H+5 and H-5 = LC(H)*P(H) S - S HOUR (H ) = *P(H) AAS Finally, the total capacity lost at the airport (LC TOTAL ) is the sum of the capacity lost under each of the 3 headwind categories. S-SHOUR ( H ) LC TOTAL = * P( H ) H AAS So, for a given hour of the day, the total number of movements that are estimated to have been in lost in 2004 is given by: LC TOTAL = S - S HOUR (15) *P(15)+ AAS S - S HOUR (25) *P(25)+ AAS S-S HOUR (35) *P(35) AAS Worked Example Say for a given hour of the day, season, and airport: The sum of the separation requirements (S) is 120Nm The separation available in that hour (S HOUR ) is 130Nm The average separation (SEP) is 4Nm o Therefore the Average Attainable Separation (AAS) is: AAS = = 4.25Nm Then, under a headwind of 10 knots or less, all arrivals can be accommodated. However, under a 15 knot headwind, the spacing available becomes: S HOUR (15) = S HOUR H = = 115Nm There is now a Spacing Deficiency, because S HOUR (15) < S: Spacing Deficiency = S S HOUR (15) = = 5Nm Therefore the number of lost movements that would occur in a 15kt headwind is: Spacing Deficiency 5 LC ( 15) = = 1 AAS 4.25 FINAL Page 40

56 There would be approximately 1 arrival lost due to a 15 knot headwind in that hour. This number will increase for the higher headwinds, because the spacing deficiency increases. Next, say for a given hour of the day, season, and airport: The probability of experiencing a headwind of between 10 and 20 knots, P(15), is 0.3 Then, the number of lost movements per hour in that season would be: This is equivalent to a total of: LC(15)*P(15) = 1 * 0.3 = * 365 / 4 27 movements lost over that season 4.2 Assumptions 1. Pair Mix. It was assumed that 25% of Heavies were sequenced into Heavy- Heavy pairs, and all other aircraft were randomly sequenced. 2. Ground Speeds. It was assumed that the ground speed of aircraft at the separation threshold (the last point on approach at which separations are enforced) is 130 knots at European airports and 150 knots at UK airports. 3. Attainable Separation. It is assumed that controllers can separate aircraft to within 0.25Nm of the minimum separation requirement (underspacing is not considered in this study). 4. The (time) spacing distribution at the separation threshold is maintained to touchdown (i.e. catch-up and pull-away have been ignored) 5. TBS. a. The ground speed of aircraft at the separation threshold is equal to 130/150 knots (Europe/UK) less the headwind component. b. The METAR-recorded surface wind speeds are equivalent to the wind speed (and direction) at the spacing threshold. FINAL Page 41

57 4.3 Results Table 15: The number of arrivals, per day, that could not be accommodated if a given headwind was present over that entire day. Number of movements that would be lost under a 15/25/35 knot headwind per day Winter Spring Summer Autumn Airport EDDF EGLL EHAM LEMD LIRF EDDM LFPG LSZH LEBL EGKK EGCC FINAL Page 42

58 Table 16: The number of movements that would be expected to have been lost over 2004, given the (surface) wind conditions. Number of movements lost in 2004 due to 15/25/35 knot headwind conditions Airport All Wind Delay in 2004 (hours) EDDF 2, ,801 3,808 EGLL 1, ,788 4,241 EHAM ,800 LEMD LIRF ,326 EDDM LFPG LSZH LEBL EGKK EGCC Included in Table 16 are the reported wind delays in 2004 (Reference [1]) for comparison purposes. FINAL Page 43

59 4.3.1 Discussion of Results 1. GENERAL: The frequency of surface headwinds exceeding 20 knots for more than one consecutive METAR is rare at virtually all airports (not more than 6-7%). 2. COMPARISON WITH WIND DELAY FIGURES: In general, there is some correlation between the results the airports most susceptible to wind delay (EDDF, EGLL, EHAM, and LIRF) are all highlighted by the method used in this study as likely airports to suffer from lost capacity due to headwind. There are, however, some exceptions; EDDM, LSZH, and LEBL all reported a significant wind delay in 2004, but the calculations made in this report suggested that the runways were not busy enough for the arrival rate to be compromised in the event of strong headwinds. There are a number of reasons that could account for this: Categorisation of delay is done at the airport, and it can not be certain that airports do this in a uniform manner. Wind delay may not always refer to a headwind. Crosswinds can also cause delay, and in airports such as LSZH and LEBL where there are a number of non-parallel runways, a crosswind component can cause one of the runways to be closed. Particularly strong crosswinds can also cause a reduction in aircraft ground speed as they have to adjust their heading to stay on course. Wherever possible, delays where it was clear that the cause was a crosswind were excluded from the figures given in Table 16, but it is expected that crosswinds are still responsible for some of the delay. Challenging winds aloft leading to delay may not be captured by analysis of surface winds. 3. EDDF In peak hours there is often a spacing deficiency even in nil headwind. This is most likely a consequence of reduced/visual separations being employed. As a result it is expected that the figures given in Table 16 offer an exaggeration of the capacity lost at Frankfurt. 4. EHAM & EGLL Both these airports operate close enough to the runway capacity that a headwind can cause a significant reduction in the throughput. In addition, there was a fairly high percentage of occasions where the headwind exceeded 10 knots. 5. LEMD A strong headwind would be expected to have a significant impact on the arrival rate at Madrid Barajas (the predicted impact of a given headwind is comparable to EGLL and EHAM). However, the fact that these conditions are FINAL Page 44

60 rarely seen at Madrid, results in a lower estimation of the capacity lost due to headwinds. 6. LIRF Because, under the preferred runway configuration, the arrivals are split between 2 runways, the runways are only rarely busy enough to be affected by headwinds. As a result, headwinds are only expected to have a minor impact at LIRF. 7. LFPG Even with the arrivals spread (it is assumed they are spread equally and randomly i.e. 50% on each) there are still occasions where there exists a spacing deficiency however, this only occurs under minimum 20 knot headwind and the rarity of these conditions result in a negligible impact on throughput. 8. LSZH, EDDM, LEBL, EGKK, & EGCC There are occasions where there exists a spacing deficiency however, this only occurs under minimum 20 knot headwind and the rarity of these conditions result in a negligible impact on throughput. FINAL Page 45

61 4.4 Parameter Sensitivity Sequencing The calculations were repeated for a number of different estimates of the fraction of Heavy aircraft that are believed to be sequenced. 0% is equivalent to a purely random sequence. Table 17 shows the effect of varying this parameter: Table 17: Annual Lost Movement Estimates for different Sequencing Estimates (red (middle) column refers to the parameter value used in the actual benefit calculation) Annual lost movement estimates for different Sequencing values Airport 0% 25% 50% EDDF EGLL EHAM LEMD LIRF EDDM LFPG LSZH LEBL EGKK EGCC Altering the sequencing parameters made little or no impact on the estimated loss in capacity. FINAL Page 46

62 4.4.2 Tolerance The calculations were repeated for a number of different criteria of tolerance estimates (i.e. the spacing margins to which controllers can work to). Table 18 shows the effect of varying this parameter: Table 18: Annual Lost Movement Estimates for different estimates of the Tolerance (red (middle) column refers to the parameter value used in the actual benefit calculation) Annual lost movement estimates for different Tolerance values (Nm) Airport EDDF EGLL EHAM LEMD LIRF EDDM LFPG LSZH LEBL EGKK EGCC For all airports for which headwind was predicted to have an impact on the maximum possible delivery rate, increasing the tolerance caused the estimated number of lost movements to increase. This is because as the tolerance increases, the average separation of the aircraft increases and there becomes less and less margin between the separation required to land the aircraft and the separation available. FINAL Page 47

63 4.5 Limitations 1. The main problem with this method is that it can not take into effect vertical wind profiles because there is a knot headwind on the surface it can not be assumed that there is a knot headwind aloft. Equally, while the percentage of time where the surface headwind component exceeds 30 knots is very low at all airports, this is unlikely to be true at higher altitudes (since, in general, wind speed increases with height). Unfortunately, since vertical wind profiles are not known this is not something that can be rectified at this stage. 2. In addition, airports like EDDF that often operate reduced separations or visual separations will yield unrealistically high estimates of lost capacities because the sum of the separation requirements will be over-estimated by the model. We know this is true since in many cases EDDF yielded hourly separation requirement totals in excess of 150Nm, which shouldn t be possible. 3. The relationship between headwind and ground speed is not as simple as put forward in this method. 4. It has been assumed that the benefit of time-based spacing is equivalent to recovering the capacity lost in challenging wind conditions. It has not been considered that time-based spacing could either not be able to compensate enough (i.e. not all lost capacity is recovered), or that it could compensate too much (i.e. allow an increase in capacity). However, it is possible to stipulate that if the time equivalent of the current separation standards (converted using 130 knots at European airports and 150 knots at UK airports) was enforced in all conditions then no capacity would be lost. The relevant time separations are given in Table 19 (far right columns): Table 19: Equivalent time separations for aircraft on arrival at UK and European airports TBS Separation Requirements (sec) Equivalent Time Separation (sec) Distance Separation (Nm) Conservative Optimistic UK Europe Both the optimistic and the conservative estimates of the time separation requirements under TBS supplied for this study (displayed in Table 19) are, in the most part, smaller than the separations required to prevent capacity loss. Therefore, it would be expected that if, under TBS, aircraft are consistently separated by these separations then all the capacity lost due to headwinds under current operations would be recovered. FINAL Page 48

64 5 Growth Forecasts Results from the parameter sensitivity studies (in particular Paragraph 3.4.2) illustrate how sensitive the benefit results are to whether or not the runway is deemed to have been queued. Since the criterion for a runway being queued was, to some extent, arbitrary, and in the expectation of increasing traffic, the benefit calculations were repeated for the case where virtually every hour was assumed to be queued (the queued criterion was set to 10% so as to exclude those hours where there is only rarely any traffic at all). What results, is a measure of benefit which is independent of whether there is a demand at current traffic levels, and is purely a function of the traffic mix and local wind conditions. It should be noted that there may be reasons why it would be impossible for the airport to sustain these traffic levels for example, LFPG is limited by the dependencies that exist between the runways, and could not support the number of movements that would be required to yield the kind of benefits displayed in the following tables. ATC-Wake: Table 20: Extra Movements possible under the introduction of ATC-Wake (ATC-Wake = 3Nm, criterion for runway to be queued = 10%) Extra Movements per Day Possible under ATC- Wake Airport Winter Spring Summer Autumn Annual Total LFPG EGLL EHAM EGCC EDDF EGKK LIRF LEMD LSZH EDDM LEBL Clearly, the potential benefits are vast if there is a demand for extra capacity for most of the day. However, LSZH, EDDM, and LEBL can expect only 1-4 extra movements FINAL Page 49

65 a day even in this extreme example. For LSZH and LEBL this is due to the small percentage of Heavy aircraft, while EDDM is limited most by the very small frequency of occasions when the crosswind exceeds 6 knots (over the period only 3-4% of the time was there a crosswind component > 6 knots). LFPG, now that it has 2 queued arrival runways from which to gain benefit from, could expect 1-2 extra movements an hour per runway (2-4 extra movements in total), giving it the highest benefit estimation. CREDOS: Table 21: Extra Movements possible under the introduction of CREDOS (CREDOS Separation = Average SID Separation (80s), criterion for runway to be queued = 10%) Extra Movements per Day Possible under CREDOS Airport Winter Spring Summer Autumn Annual Total EGLL EHAM EGCC LFPG EGKK EDDF LEMD LIRF LSZH EDDM LEBL Like ATC-Wake, the potential benefits are vast if there is a constant demand for extra capacity over the day. Again, low frequencies of strong crosswind components and a small percentage of Heavy aircraft mean that LSZH, EDDM, and LEBL can still only expect 1-4 extra movements a day even in this extreme example. In contrast, EGCC, could potentially (given the wind and traffic mix) yield a substantial benefit if CREDOS (or ATC-Wake) was introduced. FINAL Page 50

66 6 Conclusion Estimates of the benefits that could be generated from the introduction of ATC-Wake, CREDOS and Time Based Spacing were calculated. For ATC-Wake and CREDOS, where the aim is to gain additional capacity, the single biggest factor in whether or not a benefit was predicted was whether or not there was enough traffic for the runways to qualify as being queued. At current traffic levels, EGKK, EGCC, LSZH, EDDM, and LEBL, rarely (if at all) meet the criterion for the runway to be queued. As a result, under the method used in this study, these airports were not deemed to have the traffic to take advantage of any benefits that a wake vortex mitigation concept could provide. For those airports where the runways are queued on a regular basis, the benefits could be significant, provided there is sufficient wind and a significant proportion of Heavy aircraft. Airports where there was a particularly high estimation of benefit were EGLL, EDDF (for ATC-Wake only), EHAM, LEMD and LFPG (for ATC-Wake only). In general, benefit was less for departures due to the smaller number of aircraft pairs that are subject to wake vortex separation requirements. For the TBS benefit calculations, the capacity that was lost due to headwinds was estimated to give an idea of what could be recovered under the introduction to a timebased spacing scheme. As was the case for ATC-Wake and CREDOS, for a number of the candidate airports unused capacity mean that headwinds are not expected to have a detrimental effect on the throughput. As a result, no capacity was predicted to be lost due to headwinds at EGKK, EGCC, LSZH, LEBL, EDDM, and LFPG. For the airports where there is very little leeway in terms of spare capacity, a headwind can result in the loss of a significant amount of capacity over a year. The results summarised in the two paragraphs above highlight the differences in suitability for the concepts between the candidate airports. However, the figures generated in this study should be taken only as indications. There were a number of significant limitations that any high-level benefit study like this will suffer from, and as a result the figures produced should be seen only in the context of the assumptions made. In particular, the meteorological criteria for reduced separations (ATC-Wake and CREDOS) or lost capacity (TBS) were over-simplified. For ATC- Wake and CREDOS it is likely that the wind criteria must be met not just on the surface but at altitude too this far stricter requirement will reduce the amount of time the mitigation concepts can be employed, and less benefit will result. In addition, insufficient airport data required assumptions to be made about the runway configuration in use and how aircraft are sequenced. The validity of these assumptions could affect the results. The sensitivity of the results to the sequencing estimates was tested and it was found that whilst it did have an effect, it did little more than scale the results up or down and did not alter the major conclusions. If, on the other hand, the runway operating procedures were to change or the assumptions made about them were incorrect, it could have a significant impact on the benefit calculations. The consideration of traffic growth and changes to runway operating procedures or airport layout is out of the scope of the project. However, in expectation of traffic growth and in the understanding that the criteria for there to be a demand for extra capacity may not be applicable to all airports, the benefit calculations were repeated in the scenario where (virtually) all hours are queued. This, while not being a realistic scenario, does present an insight into the factors that could limit the potential benefit a FINAL Page 51

67 wake vortex mitigation concept could offer. The results highlighted the rarity of suitable crosswind conditions at EDDM and LSZH, and the low percentage of Heavy aircraft at LIRF and LEBL, which limit the suitability of ATC-Wake and CREDOS at those airports. Other airports, such as EGCC, show potential to be highly beneficial candidates once the traffic levels can warrant it. FINAL Page 52

68 PART B: High Level Systemic Analysis 7 CNS/ATM High Level Systemic Analysis Part B of this work package report details all the ATM systems which could potentially be affected by implementation of the wake vortex mitigation schemes. It does this by considering all the CNS/ATM systems in general (section 7.1), describing the state-of-the-art in terms of wake vortex and meteorological sensing (section 7.2), and then assessing which systems would be impacted upon for each of the Wake Vortex Mitigation Concepts (section 7.3). In order to proceed with a CNS/ATM 9 high level systemic analysis it has been deemed appropriate to include an overview of a generic CNS/ATM System. For the purposes of this study it has been considered that the most suitable way of approaching this overview is presenting the system architecture as a high level functional decomposition into a logical set of functional blocks 10. The main functional blocks of the CNS/ATM System considered in this paper are described below. 7.1 CNS/ATM Functional Blocks description The CNS/ATM functional blocks briefly described in this section are extensively analysed by Eurocontrol in reference [7]. A schematic view of these blocks is shown in Figure 1. Figure 1: Generic CNS/ATM System Functional Blocks 9 CNS/ATM, as defined by ICAO, means Communications, Navigation and Surveillance systems applied in support of a seamless global Air Traffic Management system 10 A functional block is a logical group of system functions performed on a certain input data in order to produce certain results (output). FINAL Page 53

69 The functional blocks of Figure 1 are briefly described in the following sections ATM Blocks The main blocks grouped in the ATM system are the following: Aeronautical Environment Processing (AEP) The Aeronautical Environment Processing functional block comprises the functions: Static Data Operations and Dynamic Environmental Data Processing. A schematic view of this block is shown in Figure 2. Figure 2: AEP Functional Block Both functions are briefly described as follows: Static Data Operations (SDO) provides all static data to the CNS/ATM and AIS functions and all relevant end-users. SDO includes the part of Environment Data Processing and Distribution related to ATS environment static data: airspace structure data and system parameters Dynamic Environmental Data Processing (DEDP) includes the functions: NOTAM operation and MET data processing Air Traffic Flow Management (ATFM) Within the ICAO European Region the ATFM is a service complementary to ATC that aims to ensure an optimum flow of air traffic to or through areas within which traffic demand at times exceeds the available capacity of the ATC system. ATFM in the ICAO EUR region is performed in the three phases: Strategic, Pre- Tactical and Tactical. A schematic view of the ATFM block is shown in Figure 3. FINAL Page 54

70 Figure 3: ATFM Functional Block Functions shown in Figure 3 are briefly described as follows: Strategic System (STRAT) provides a flight database, which represents the best possible picture for the traffic demand concerning the Strategic and Pre-tactical ATFM periods. This database contains Planned Flight Data (PFD), Repetitive Flight Plans (RPL) and last minute changes to the Aircraft Operators (AOs) planning. Tactical System (TACT) provides a tactical database that contains flight data for the next forty-eight hours. Flight Plan Messages and subsequent updates are added to the data available in STRAT in order to present a fully updated picture of air traffic demand. Aircraft Operators (AOs), FMPs and the Flight Data Processing and Distribution (ATS Units) are informed of the tactical measures through the related TACT Messages Out. The Air Traffic Flow Management Notification Message (ANM) tool informs AOs and FMPs of the pre-tactical plan elaborated from the tactical database. Supporting Tools includes Archiving System (ARC) and Delay Analysis. FINAL Page 55

71 Flight Data Processing (FDP) A schematic view of the FDP block is shown in Figure 4. Figure 4: FDP Functional Block Functions shown in Figure 4 are briefly described as follows: Initial Flight Plan Processing (IFPP). It aims to rationalise reception, initial processing and distribution of IFR flight plan data. These services are provided by a (centralised) flight planning system for the States within the CFMU area. The two primary functions are: the Processing of individual flight plan messages (FPLs) and the Processing of repetitive flight plans (RPLs) Flight Data Processing & Distribution (FDPD). The FDPD relates to the realtime phase of the flight life cycle. Considering the FDP implemented at ATC Unit level, the following ones are the main sub-functions: Initial Message Handling. System Flight Plan Processing. Flight Data Handling. Trajectory Prediction. G/G Co-ordination & Transfer. SSR Code Management A/G Co-ordination. Correlation (A/C Identification). FINAL Page 56

72 ATC Tools and Controller Working Position This functional block supports the integrated ATM operations and improves ATC capacity and safety. It alleviates the cognitive workload enabling the ATC operators to focus on the relevant information, and it enhances their appreciation of the current and predicted traffic situation, facilitating the decision making process. A schematic view of the ATC Tools & CWP block is shown in Figure 5 Figure 5: ATC Tools & CWP Block The elements considered in this block are described as follows: ATM added functions (AAF). This group includes: Monitoring Aids (MONA). They help ATCOs in monitoring all the flights under control in order to detect deviations from the system trajectories, checking that the observed position and behaviour conforms to that planned. Medium Term Conflict Detection (MTCD). It assists ATCOs in monitoring the air situation continuously and providing them conflict data through a HMI. Conflicts can be different in nature: aircraft conflicts 11, nominal route overlaps 12, penetrations into special use airspace 13, descent below lowest usable flight level. Safety Nets (SNET). These are intended to alert ATCOs to potential hazardous situations within the observed traffic situation. SNETs are designed to work in the short term, using prediction and warning times of the order of 2 min or less. Sequencing Manager. The purpose of this element is to provide a sequencing and metering capability to ATC for an optimal used of the runways. There are two types of Sequencing Manager, in accordance with the two types of runway operation: the Arrival Manager (AMAN) and the Departure Manager (DMAN). ATC HMI and CWP. ATCOs perform their tasks at the CWP (Controller Working Position) which contains the ATC HMI that constitutes the common interface for the ATC tools and includes: input and display processing and presentation management. 11 Loss of separation between probable positions of two A/C 12 Loss of separation between system trajectories of two A/C 13 Loss of the required distance between probable positions of an A/C and special use airspace FINAL Page 57

73 7.1.2 Communication, Navigation and Surveillance (CNS) The CNS part of the system consists of the following three blocks: Communications (COM) The Communications element of CNS provides the connectivity and information transfer service (linkage) for all functional blocks, both for internal (local area) and remote (wide area network) air and ground flows. Therefore the COM block could be considered as part of the infrastructure for the entire system. A schematic view of the COM block considered in this analysis is shown in Figure 6. Figure 6: COM Block The elements included in this block are: COM Infrastructure. Monitoring & Control (usually included in the CNS/ATM Support functional block) Information Handling. It includes handling of A/G and G/G communications, both via voice and data. COM Support. It includes COM Services and Distribution Services. Transport - Routing. It provides reliable transport of information from identified source to destination points on either the local or wide area networks. Local 14 COM.. It provides local connectivity services within a specific physical location. Both voice and data are distributed. Remote 15 COM. It covers Voice, Data and Telemetry services. It is further subdivided into: Air/Ground COM and Ground/Ground COM 14 In terms of European communications, local means at ATS or Regional/ European Unit level 15 In terms of European communications, remote means at National and Regional/European level. FINAL Page 58

74 Navigation (NAV) The Navigation element of CNS aims to 1) define for the aircraft, the path from a given point to another, and 2) monitor A/C position to identify and correct any deviation from the planned course. The NAV block is actually distributed over several functional blocks 16, but for the purposes of this analysis it will be considered limited to the ground infrastructure component and the functions needed to provide the navigation service (i.e. the provision of accurate and valid data to the airborne navigation system). A schematic view of the NAV block considered in this analysis is shown in Figure 7. Figure 7: NAV Block The elements considered in this block are: Operational Monitoring & Control. It manages the operational data like those useful to the NAV Service users and those required to ensure the accountability for the service provided to the users. Technical Monitoring & Control. It is responsible for monitoring and controlling the operations of those systems dependant on this element. It also ensures the collection of appropriate data. NAV Signals Generation. It provides data needed by the users to perform their navigation task using available means (ground or satellite). It should be noted that both the Operational and Technical Monitoring & Control are usually covered by the CNS/ATM Support functional block (see 7.1.3). 16 Guidance and Positioning functions are distributed in the Airborne CNS/ATM Component and in the ATC functions, the Navigation Infrastructure Monitoring & Control is covered generically in the CNS/ATM Support Functional Block FINAL Page 59

75 Surveillance The Surveillance element of CNS provides data and information of required quality to facilitate the identification of A/C and the representation of their accurate position and kinetic characteristics in accordance with the ATM needs. A schematic view of the Surveillance block considered in this analysis is shown in Figure 8. Figure 8: Surveillance Block The elements considered in this block are described as follows: Data Capture. The process of data capturing for surveillance purposes is performed by Independent Surveillance (IS), Co-operative Independent Surveillance (CIS), Automatic Dependent Surveillance Broadcast (ADS-B) and Automatic Dependent Surveillance (ADS). Surveillance Data Processing (SDP). It combines all data processed (position, state vector and additional attributes of A/C) and presents them to give the users a coherent recognised air situation picture. Surveillance Infrastructure Monitoring. This is usually included in the CNS/ATM Support functional block. FINAL Page 60

76 7.1.3 CNS/ATM Support The CNS/ATM support block provides the management of capabilities that enable the operational system to provide services with the required level of quality. A schematic view of the CNS/ATM support block considered in this analysis is shown in Figure 9. Figure 9: CNS/ATM Support Block The elements considered in this block are described as follows: Operational Monitoring & Control. It allows the operational supervisor to organise the work within the corresponding entity according to the current constraints (traffic load, available resources, etc.). Pre-tactical and tactical information on current and planned traffic load is provided by the Traffic Load Monitoring function 17. Technical Monitoring & Control. This function is responsible for monitoring and controlling the operations of the various systems within the entity (or group of entities) for which the technical supervisor has the responsibility. This includes the reconfiguration and assistance to both hardware and software and the provision of supporting services to manage local and distributed resources. The two main groups of resources that this function monitors and controls are: computer resources and infrastructure resources. Data Management. This function provides both static and dynamic data management services. It covers the data storage and retrieval, data integrity, and data distribution. Recording, Replay & Data reduction. Logistics Support. This function is derived from the concept of Integrated Logistics Support (ILS) and usually includes more elements 18 than those considered for this CNS/ATM system analysis, which are: maintenance, training and documentation. 17 Implemented in the ATFM functional block 18 A typical ILS includes the following areas: manpower & personnel, training & training support, technical documentation, supply support, support equipment, infrastructure, PHST (Packaging, Handling, Storage, Transportation), & software support. FINAL Page 61

77 7.1.4 CNS/ATM Airborne Component The primary airborne functions related to CNS/ATM and provided by the onboard avionics include: lateral and vertical navigation, precision approach, voice and data communications, surveillance, crew interface and common time reference. These functions can be provided by an equipment suite consisting of a Flight Management System (FMS), a Multi-Mode Receiver (MMR) or GNSS Navigation and Landing Unit (GNLU), and a Communications Management Unit (CMU). It is expected that as technology advances the mentioned components will be integrated into a single, modular unit. A schematic view of the Airborne CNS/ATM Component block considered in this analysis is shown in Figure 10. Figure 10: Airborne CNS/ATM Component Block The elements considered in this block are: Navigation, Communications and Surveillance & ATM applications Services Providers This section briefly describes the main service providers for the CNS/ATM System considered in this analysis. It must be noticed that according to ICAO terminology (and also the EATCHIP OCD) these service providers are not considered part of the CNS/ATM system, although they may be located and physically integrated within the CNS/ATM facilities. Meteorological (MET) services providers. They have the responsibility to forecast, observe, provide and collect en-route and airfield weather forecasts (TAFs) and the corresponding METARS for all parties dealing with flight planning and flight operations. The availability of high quality meteorological information for the calculation of flight trajectories, both at pre-flight and during flight (i.e. forecasts and nowcasts) can be considered essential for the flight safety and the overall efficiency of the CNS/ATM System. Aeronautical Information Services (AIS) providers. They are required to collect and disseminate the information/data needed to ensure the safety, regularity and efficiency of air navigation 19. Such data/information includes the availability of air navigation facilities and services and the procedures associated with them, and must be provided to flight operations personnel and services responsible for preflight information. 19 The role and importance of aeronautical information/data has changed significantly with the implementation of area navigation (RNAV), required navigation performance (RNP) and airborne computer-based navigation systems. Corrupt or erroneous aeronautical information/data can potentially affect the safety of air navigation. FINAL Page 62

78 7.2 Description of Weather and WV sensor technologies. Both weather monitoring & prediction and the understanding of wake vortex behaviour are essential to develop and further implement a wake vortex mitigation concept (WVMC). In addition, the capability of WV detection and monitoring is required for advanced concepts like ATC-Wake. Therefore due to the fact that the WVMC level of implementation depends on the weather/wv sensor technologies selected, it is considered advisable to provide an overview of the state of the art of such technologies, as well as a recommendation at high level on some sensor solution packages that would provide different levels of implementation concerning the weather/wv detection and monitoring capabilities. The main sources of information used for the following description are references [8] and [21] Required measurements for enabling separation reduction The WVMC considered in this study aim at reducing the current ICAO separations, and in order to achieve these reductions the parameters listed in Table 22 are required/ recommended. A/C parameters Position (time stamped) of leader A/C Velocity of leader A/C Weight of leader & follower A/C Short-term trajectory of follower A/C Weather and WV Measurements Wind profiles (primary need) Temperature profiles (secondary need) Turbulence: TKE, EDR (secondary need) Position of each WV (primary/ secondary 1 need) Circulation of each WV (primary/ secondary 1 need) 1: For near-term WVMCs (TBS, CREDOS) these measurements are secondary (not required) but for advanced concepts (farterm, e.g. ATC-Wake) these are primary (required) Table 22: Required/recommended measurements for enabling separation reduction. The technologies and procedures for A/C parameters are already implemented at airports. Therefore the description shall focus only on the technologies for weather and WV measurements. As shown in Table 22, measurements corresponding to wind profiles and WV detection (position and circulation) are considered primary needs (required) for WVMC implementation whereas temperature profiles and turbulence may be considered secondary needs (recommended) Technologies for weather and WV measurements The main technologies applicable for weather and WV measurements are briefly described in Appendix 4. Table 23 summarises the main sensor technologies described in the appendix and more extensively in reference [8]. This table shows the most appropriate technologies for each application (primary and secondary needs) as well as the level of maturity (COTS or R&D technologies). Table 31 (Appendix 4) provides estimations about some economical information of candidate technologies that may be useful for the costs estimations to be performed in the CBA. FINAL Page 63

79 WVMC Primary Needs WIND PROFILE RADAR (UHF, TDWR, TEP, S or X band) LIDAR PC CW multi beam SODAR Met Tower SENSOR TECHNOLOGIES WV DETECTION Coherent LIDAR Pulsed 2µm Pulsed 1.5µm CW WVMC Secondary Needs TEMPERATURE PROFILE RASS + SODAR TURBULENCE Met tower + Sonic anemometer Wind-lines RASS +RADAR LIDAR LP2C SODAR RADAR (S or X band) Microphone array Where: COTS Technology R&D Technology Microwave radiometer TEP RADAR Table 23: Summary of sensor technologies for weather and WV measurements (source: reference [8]) Some technological sets for weather and WV measurements Based on the technologies presented in Table 23, the preparatory study of WV Detection Technology Case (reference [8]) produced for the Eurocontrol WAKESEP project proposed three sets of technological solutions for weather and WV measurements, that are presented as follows: Short-Term Optimal Operational Solution A possible short-term solution that achieves most of the WVMC functional and operational requirements is one including a combination of two 2µm PC LIDAR, (at least) two wind-lines, a TDWR (for wind profiles under rain conditions), and a RASS SODAR (for wind and temperature monitoring). This solution is presented in Table 24, which shows that all these sensors are already available (COTS). FINAL Page 64

80 WEATHER CONDITION No rain Fog Heavy Rain AREA WVMC Primary Needs WIND PROFILE SENSOR TECHNOLOGIES WV DETECTION ILS Approach LIDAR PC 2µm & Climb Critical 20 ILS Approach & Climb RASS + SODAR Critical LIDAR PC 2µm ILS Approach & Climb RADAR TDWR Critical Wind-lines + Met Tower (up to 45m) Where: COTS Technology R&D Technology WVMC Secondary Needs TURBULENCE TEMPERATURE PROFILE Table 24: Short-Term Optimal Operational Solution (source: reference [8]). RASS + SODAR Wind-lines + Met Tower (up to 45m) It must be noticed that foggy conditions for upper areas (ILS and Approach / Climb) are not covered by any instrument in this solution. Short-Term Low Cost Solution An alternative more cost-effective solution to the above one includes the same instruments except for the TDWR and RASS SODAR that would be replaced by an UHF profiler equipped with RASS for temperature profiling. This solution would reduce costs but would not be operational under heavy rain. This solution is presented in Table 25, which shows that all sensors considered are COTS. 20 Critical area refers to an area with the highest probability of WV encounter FINAL Page 65

81 WEATHER CONDITION No rain Fog Heavy Rain AREA ILS Approach & Climb Critical ILS Approach & Climb WVMC Primary Needs WIND PROFILE RASS + RADAR UHF SENSOR TECHNOLOGIES WV DETECTION LIDAR PC 2µm Critical LIDAR PC 2µm ILS Approach & Climb Critical Wind-lines + Met Tower (up to 45m) WVMC Secondary Needs TURBULENCE TEMPERATURE PROFILE RASS + RADAR UHF Wind-lines + MET Tower (up to 45m) Where: COTS Technology R&D Technology Table 25: Short-Term Low Cost Solution (source: reference [8]). Mid-Term Solution Reference [8] also proposes a solution that might be available in the mid-term (about five years), considering the new technologies that are under development, with different levels of maturity (see Table 31, Appendix 4). It is envisioned that: new generation of PC LIDAR will replace the current ones reducing cost and size; S-band RADAR will be able to be used for wind and turbulence monitoring even under foggy conditions, and they could also be used for WV detection 21 ; TEP RADAR will be able to be used for wind and turbulence monitoring in approach/climb area and under weather conditions that includes fog and rain. This solution is presented in Table 26 and it shows that most sensors are still under research and development. 21 It requires further assessment. FINAL Page 66

82 WEATHER CONDITION No rain Fog Heavy Rain AREA ILS Approach & Climb Critical ILS Approach & Climb Critical ILS Approach & Climb WVMC Primary Needs WIND PROFILE Long Range LIDAR PC 1.5µm TEP RADAR SENSOR TECHNOLOGIES WV DETECTION Long Range LIDAR PC 1.5µm LP2C SODARS (landing) TEP RADAR LIDAR PC 1.5µm LP2C SODARS (landing) X/S Band RADAR WVMC Secondary Needs TURBULENCE Long Range LIDAR PC 1.5µm TEP RADAR TEP RADAR LIDAR PC 1.5µm Critical Wind-lines + Met Tower (up to 45m) TEMPERATURE PROFILE Microwave Radiometer Wind-lines + Met Tower (up to 45m) Where: COTS Technology R&D Technology Table 26: Mid-Term Solution (source: reference [8]). 7.3 Description of WV Mitigation concepts and their impacts on the CNS/ATM System. The following sub-sections intend to provide an overview of the three WVMC considered in this study, presenting its main requirements and the main impacts of their implementation on the CNS/ATM System. A comparative summary of the three WVMC is provided in Table 33 (Appendix 5). In addition, Table 34 (Appendix 6) presents a summary of WVMC technological requirements according to the implementation level (basic/advanced configuration) Time-Based Spacing (TBS) Introduction The Time Based Separations (TBS) project was launched by Eurocontrol as a research project in The problem it addresses is the following: during the approach phase A/C are separated according to current ICAO standards, which are invariable (for each type of leader-follower pair of A/C), distance-based and conservative (based on worst-case scenario); consequently there is a loss of runway capacity in conditions of significant headwinds (above 10kt), since in these conditions the A/C ground speed decreases (and then the actual time separation increases). The TBS project aims at defining and investigating time-based separations for arrivals. The TBS project is FINAL Page 67

83 proposing methods and tools that will enable TBS operation while maintaining the required level of safety. It should be noted that the objective of TBS implementation is the recovery (total or partial) of the capacity usually lost under these conditions of significant headwinds but it does not intend to increase the normal achievable capacity. The earliest WVMC implementation, based on the results of TBS project, is assumed to be Functional description and requirements of the concept The TBS project proposes ATC procedures and tools to support the TBS operation in the CNS/ATM system. A TBS module can be included in the generic CNS/ATM system as a functional block called TBS Tool that constitutes the core of the TBS system. The following functional blocks complete the TBS system, providing inputs or interacting with the TBS Tool: SDP (Surveillance Data Processing). This function from the Surveillance block (see ) provides the TBS Tool with the required inputs regarding A/C position, state vector and additional attributes of A/C. FDP (Flight Data Processing). This functional block (see ) provides the TBS Tool with the required inputs regarding flight data, especially those related to the Trajectory Prediction function. MET Data. Its inputs are essential for the TBS Tool, since they provide actual and predicted data about the wind (speed, direction, etc.), temperature, visibility, etc. that affect directly the WV characteristics (decay, transport, etc.) and hence the arrival procedures. Therefore these data impact directly on the TBS-Tool performances and the decision making. Monitoring & Maintenance. A functional block is required that will interact with the TBS Tool to ensure a correct functioning of the TBS system through monitoring and maintenance tasks. ATC Tools & CWP. This functional block (see ) is responsible for the interaction with ATCOs (HMI). Therefore, the tools included in the TBS-Tool block are oriented to this functional block. The TBS project proposed the following tools for the HMI, which have been extensively described in reference [9]: Trailing Position (TP): displays the ideal position of the follower A/C from the actual leader position in order that the follower and leader A/C are separated by the exact required time separation. Intelligent Time Vector (ITV): is the equivalent of the current speed vector except that it takes into account the deceleration, the potential turns, and the wind effect. It thus corresponds to the displaying of the forecast position of the follower - based on trajectory prediction - up to a time that corresponds to the time separation between the considered A/C and the one that is in front of it. Figure 11 shows the high level functional overview of the TBS System. FINAL Page 68

84 Figure 11: High level functional overview of the TBS System Impacts on the CNS/ATM System This section briefly describes the impacts that the TBS system implementation may cause on the CNS/ATM functional blocks. ATM Blocks The main ATM functional blocks that will or could be directly affected by the TBS implementation are the following: AEP (Aeronautical Environment Processing, see ). The main impact would be on the DEDP, since TBS requires the adaptation of the existing approach procedures. This includes procedure planning, implementation and communication via AIP/AIC/NOTAM, which need also production and submission (cost increases). FDP (see ). The main functions affected by the implementation are: Flight Data Handling. It provides flight data inputs to the TBS-Tool and therefore an interface is required. Trajectory Prediction. It is important to notice that a good trajectory prediction is essential for the TBS reliability. The TBS project proposes the use of an external trajectory prediction (that should be available in the ATC system) and adapted it so that it takes into account accurate A/C performances, deceleration rates and wind data. In an advance phase of TBS, the adjunction of a trajectory predictor could be the only way not to lose the efficiency of the TBS system. ATC Tools & CWP (see ). There are more changes that would be required to adapt it to the TBS implementation. The main changes are: SNET. Reduced distance separations under strong headwinds conditions may cause an increase in the number of alerts with current STCA systems and therefore these may require adaptation to the new time-based separations, taking into account the wind conditions. Sequence Manager. There is a need of adapting the AMAN to include the TBS procedures and perform the arrival sequence calculations in accordance FINAL Page 69

85 with them. An advance version of the TBS System could integrate the AMAN functions 22. ATCO HMI. In most cases, only minor software adaptations would be required. Mainly: - additional commands to give direct access to ITV or TP; - ITV/TP representation for the radar plot in the suited zone; - category of A/C on the label (if not already available) to allow easy checking of TBS depending of Wake Turbulence category, H, M or L and eventually highlight the Heavy wake turbulence category; - ILS axis on the map; - wind information (at least surface wind data) in a specific window (to be validated); - monitor arrival sequence of A/C (output of AMAN at the ATCO HMI) As with all changes in the presentation of information to controllers, an assessment of the impact on controller workload would need to be made, to ensure that the tools can be implemented without adverse affect in controller workload. CWP. In most cases the TBS software can run on standard (available) equipment but, from the point of view of costs (CBA) the following aspects must be considered: - Since the TBS system will be a safety relevant component of the CNS/ATM system there is a need of redundant equipment in order to comply with the availability, integrity and contingency requirements. - The replacement of the CWP equipment must be taken into account before the lifecycle expires (about 10 years) CNS Communications (see ). There is no primary need of changes in COM due to the TBS implementation. However the introduction of the following technologies may enhance the potential of TBS: CPDLC. It provides a text interface and data link between ATCOs and pilots via digital radio, reducing the need for voice communication of standard messages and clearances. The additional development of message protocols could enable the use of CPDLC to facilitate clearances associated with the TBS procedures. D-ATIS. This system, currently in process of implementation at some major airports, is designed to continuously provide flight crew with broadcast text messages of local weather conditions, current airport runway and taxiway status, etc. It is envisioned that this text messaging system could ultimately be enhanced to provide wind and/or wake prognosis for improved situational awareness. 22 According to reference [7] it was envisioned the implementation of an advanced AMAN (including WV data) within the period However, since reference [18] confirms the slow progress so far in AMAN implementation (most states have no plans to implement it), it is expected a significant delay in the implementation of an advanced AMAN or its integration in the TBS system. FINAL Page 70

86 ADS-B. It is an advanced communication system that sends and receives sets of local aircraft data in real time. The primary purpose of this system is to provide air-to-air surveillance data among suitably equipped aircraft. For the purpose of implementing TBS, the ADS-B downlink (air-to-ground) portion could be defined to include A/C parameters and weather/wv measurements (see Table 22). The uplink (ground-to-air) could include the location of other aircraft in area (i.e. Traffic Information Service, Broadcast mode [TIS-B]) required to perform TBS procedures. Navigation (see ). Although there is no primary need of changes in NAV for the TBS implementation, the introduction of NAV technologies/ procedures (e.g. RNP 23 ) could facilitate the implementation of TBS procedures. Surveillance (see ). This component provides the required inputs regarding position, state vector and additional attributes of A/C. Therefore an interface with the TBS-Tool has to be developed. Although they are not requirements for TBS implementation, the following technologies could improve the TBS system performance: ADS-B. As mentioned above, the implementation of this system would improve the provision of A/C surveillance data and would enable the transmission of other useful data (e.g. on-board measured weather/wv data). Precision surveillance technology can provide accurate measurements with fast-update of A/C position on final approach 24. Any system used would need to meet the more stringent accuracy requirements for reduced (distance) separations which would result from TBS. CNS/ATM Support Logistic Support: Maintenance. It is quite evident that the increase of ATC functionalities together with the need of redundant equipment, both due to the TBS implementation, will have a significant impact on maintenance effort and costs. Training & Simulation. Both ATCO and technicians will require training courses and simulator exercises (especially ATCO) to qualify them in the operation (ATCO) and maintenance (technicians) of the TBS system. Documentation. As any system, the TBS requires the production of (abundant) documentation that helps the CNS/ATM community to implement, manage, operate and maintain the system. Technical and Operational Monitoring & Control. The new functionalities and tools after the TBS implementation will require new interfaces and may need changes on procedures in both the technical and the operational monitoring & control. Recording, Replay & Data Reduction and Data Management. The new software and equipment required for the TBS implementation will imply an 23 RNP combines RNAV operations with navigation containment and monitoring. 24 As well as on the surface and during initial climb. FINAL Page 71

87 increase in data and therefore, some changes may be necessary to perform these tasks. CNS/ATM Airborne Component Communications. As said before regarding the Ground COM component, there is no primary need of changes in COM due to the TBS implementation, but the introduction of data-link could contribute to improve the TBS efficiency. Navigation. As mentioned before, the introduction of NAV technologies/ procedures like RNP/RNAV could facilitate the implementation of TBS procedures. It requires the updating of NAV equipment (data-link, GNSS, etc.) and procedures to meet RNP/RNAV standards. Surveillance and ATM applications. The development and implementation of the following on-board surveillance equipment and ATM applications could improve the efficiency of the TBS system: ADS-B, which, as said above, enables to down-link A/C parameters and onboard measurements of MET and WV parameters (wind/temperature profile and aloft, WV position and intensity etc.). In addition, ADS-B and CDTI are primary enabling technologies for a flight crew-based approach spacing tool. Specific airborne equipment for WV detection (e.g. see I-WAKE 25 and MFLAME 26 projects) Services providers Meteorological (MET) services providers. These providers constitute one of the most critical elements for a successful implementation and operation of the TBS system, since they provide all or most of the MET data on which the performance of the TBS system relies. Therefore, these providers may need some investments in order to ensure the required quality level of the MET data necessary for the functioning of the TBS system, in accordance with the selected/feasible 27 level of implementation. Aeronautical Information Services (AIS) providers. These providers shall publish information on those airports where TBS are applied and the associated procedures Crosswind Reduced Separations for Departure Operations (CREDOS) Introduction Although the CREDOS project is yet to start, it will aim at studying the operational feasibility of reducing current ICAO separations in departure operations under conditions of significant crosswind. More specifically, the project activities will cover two major areas: 25 I-Wake: Project on Instrumentation Systems for onboard Wake-Vortex and other Hazards Detection Warning and Avoidance, co-funded by the European Commission (GRD ) from 2002 to Project on Multi-Function Future Laser Atmospheric Measurement Equipment, co-funded by the European Commission (BRPR-CT96-182) from 1996 to Feasibility may depend on the maturity of sensors technology FINAL Page 72

88 The research necessary to fully understand the WV behaviour in departure configurations. The validation activities necessary to make a thorough investigation of the operational benefits that can be expected from a real-world application of crosswind-reduced departure separations. In addition, the methods and tools developed by the CREDOS project could be later used to cover arrivals and other meteorological conditions. The project will also produce an algorithm for detecting wake vortex encounters from flight recordings and this will be used as part of the validation process. The CREDOS project is not expected to start until 2006 and will have duration of three years. Therefore there will not be enough information up until three or four years to conduct a CBA with the same level of reliability than in the case of the other two mitigation concepts, despite the high level approach of this study. However, some information can be gathered from other projects or initiatives. In particular it must be mentioned that the US have started a number of data collection campaigns (e.g. San Francisco measurement programme to support CSPR procedures and St. Louis data campaign within the WakeNet-USA) to provide information for the understanding of WV behaviour in departure operations, which will enable the development of the necessary assessments to implement reductions in current departure separations. One of the projects to take into consideration is the US project WakeVAS (reference [20]), similar to the European ATC-Wake (see 7.3.3), which provides information about crosswind-dependent departures that may be useful for both CREDOS and ATC-Wake in terms of assessing the system requirements and impacts on CNS/ATM system when implementing and operating those WVMC for departures under conditions of significant crosswind Functional description and requirements of the concept As said before, there is not enough available information regarding the operational concept and the operational & system requirements. However, it is expected the CREDOS concept to be analogous to TBS for arrivals, especially regarding the HMI and safety case developments. Therefore the high level functional overview of the CREDOS system is likely to be similar to the one of TBS. Nevertheless, it must be noted that there are some differences between departures and arrivals that will introduce different procedures and, probably, system requirements than the ones described for TBS. Some of these differences are the following: In departures, the follower aircraft is on the ground so the ATCO always has the possibility to extend the separation without requiring the pilot to make a manoeuvre. Since in departures the leader aircraft is generally faster than the follower, the actual separations tend to increase, whereas in arrivals the slower speed of the leader generally leads to catch up by the follower (compression effect). After take-off the follower aircraft can climb or turn out of an encounter more easily than in the descent phase. It is possible that the jet-blast at take-off will have a significant effect on the rate of WV decay It will be investigated in the FAR-Wake project FINAL Page 73

89 A disadvantage of departure operations in comparison with arrivals is the fact that there is not an equivalent of the standard glide-slope associated with arrivals on a particular runway. In fact, depending on A/C type, piloting preferences and choice of entry taxiway, the rotation point of the take-off may vary considerably and then there is a range of climb angles and departure routes, which makes WV prediction more difficult than for arrivals Impacts on the CNS/ATM System According to what has been said before and for the purposes of this study, it can be considered at high level that the impact of the CREDOS implementation on the CNS/ATM system would be similar to the one described for the TBS case. However, the differences between departure and arrival operations must be kept in mind, as this may introduce different procedures and system requirements than in the TBS case. The following paragraphs present a rough description of the impacts that the CREDOS implementation may cause on the generic CNS/ATM functional blocks. ATM Blocks AEP (see ). As said in the TBS case, the main impact would be on the DEDP, since CREDOS may require the adaptation of the existing departure procedures. This includes procedure planning, implementation and communication via AIP/AIC/NOTAM, which need also production and submission (cost increases). ATFM (see ). The CREDOS implementation may affect the TACT part of ATFM, especially concerning the Air traffic flow Management Notification Message (ANM) tool, since it shall inform the AOs and FMPs about the mode of operation (ICAO/CREDOS). FDP (see ). The main functions affected by the implementation are: Flight Data Handling. It would provide flight data inputs to the CREDOS- Tool (analogous to TBS one), if it is developed, and therefore an interface would be required. Trajectory Prediction. It is less critical in departures than in arrivals. Besides, it would be more difficult to develop or adapt such prediction for departure operations with a high enough level of quality, since, as previously mentioned, there is a range of climb angles and departure routes. ATC Tools & CWP (see ). In case that a CREDOS-Tool were developed the impact on this block would be similar to that caused by the TBS, except that the Sequence Manager to be considered would be the DMAN 29 instead of the AMAN. However it must be noted that a TBS-like HMI may be unnecessary, at least for a basic CREDOS implementation (it would be sufficient with current and planned 30 ATC tools). CNS 29 The interaction between the concepts CREDOS and DMAN will be addressed by the CREDOS project. 30 Planned enhancements (e.g. on-going R&D) apart from the WVMC. FINAL Page 74

90 Communications (see ) and Navigation (see ). As in the case of TBS, there is no primary need of changes in COM or NAV due to the CREDOS implementation, although improvements in the CNS/ATM system due to the introduction of new technologies and procedures may enhance the potential of CREDOS. Surveillance (see ). An interface with the CREDOS-Tool would be required, if such a tool was developed. Although it may not be a requirement for the CREDOS implementation, the introduction of precision surveillance technologies (e.g. ADS-B, A-SMGCS 31 ) would improve the WVMC performance. CNS/ATM Support Logistic Support. The CREDOS implementation is expected to impact on the logistic support aspects considered (maintenance, training & simulation and documentation) in a similar way as the TBS implementation. Technical and Operational Monitoring & Control. These functions are expected to be affected by the CREDOS implementation in a similar way to that in the TBS case if a CREDOS-Tool (analogous to the TBS one) is developed. Otherwise, the impact would be only procedural and therefore, lower than in the TBS case. Recording, Replay & Data Reduction and Data Management. Again, the impact would be dependant on the development of a tool analogous to the TBS one. CNS/ATM Airborne Component There is no primary need of changes in this component due to the CREDOS implementation, but the introduction of any technology that improves CNS/ATM would enhance the CREDOS performance. In particular, data-link (e.g. ADS-B) would provide flight crews, in a more efficient way, information about CREDOS planning (active or not and when), procedures, WV encounter risks, etc. At the same time this technology would enable the down-linking of A/C parameters and on-board measurements of MET and WV parameters. In addition, specific airborne equipment for WV detection (as mentioned in TBS: see e.g. I-WAKE and MFLAME) could be considered for this component. Services providers Meteorological (MET) services providers. As stated in the TBS case, since MET data collected by these providers are essential (and recommended for WV data) for the successful implementation and operation of the CREDOS concept, it may be necessary to make some investments in order to ensure the required quality of the necessary MET data. In addition, the introduction of the capability of monitoring WV during the departure operations 32 could be considered for an advanced implementation of this WVMC. 31 The interaction between the concepts CREDOS and the A-SMGCS will be addressed by the CREDOS project. The A-SMGCS implementation plan is expected to be developed from 2006 on. 32 It must be noted that for a basic implementation, a good knowledge of WV behaviour is required in order to ensure that the level of WV risk encounter during departure operations is within the margins established by the safety requirements. FINAL Page 75

91 Aeronautical Information Services (AIS) providers. These providers shall publish the applicability and planning of the CREDOS procedures. Therefore, an interface may be required (particularly if there is a CREDOS-Tool) ATC-Wake Introduction ATC-WAKE stands for Integrated Air Traffic Control WAKE vortex safety and capacity system and it is an IST 33 Project started in 2002 and funded by the European Commission under 5th Framework Programme. The ATC Wake Project aims at developing and building a WV safety and capacity integrated platform (IP) to: evaluate the interoperability with existing ATC system; assess the possible safety and capacity improvement; evaluate the operational usability & acceptability for ATCOs; draft a Technological Implementation Plan (TIP) and assess the costs for further development, implementation and exploitation of the IP. This platform is an essential step that will lead to installation of an integrated ATC decision support system at airports, enabling air traffic controllers to apply new optimised weather based aircraft spacing. The targeted separations, under favourable WV conditions (WV decay or transport out of the A/C path), are the following: Arrivals: 2.5 NM for both A/C flying on the same final approach path (in particular at runway threshold) and in CSPR (staggered approaches). Departures: 90 s between A/C on the same runway The ATC-Wake system will integrate weather and wake sensors, weather forecasting and now casting systems, wake vortex prediction system, aircraft spacing predictor and ATCO interface. Used with new harmonised safety regulation, this system will provide tactical and strategic benefits, while maintaining safety Functional description and requirements of the concept The ATC-Wake Concept will be based on the results of the ATC-Wake project, integrating in the CNS/ATM system the following components developed for the IP: ATC-Wake Separation Mode Planner (SMP). This component determines the applicable separation mode ICAO mode or ATC-Wake, setting a safe arrival/departure rate in advance 34. It advises of the minimum aircraft separation distance 35, based on the inputs that it receives from: MET Services, which provide weather forecasts 36 ; ATC-Wake Predictors, which provide the actual and short-term WV situation prediction; 33 Information Society Technologies 34 Changes of separation mode have to be decided with a minimum look ahead time of 40 min if a Sequence Manager (AMAN for arrivals) is used, and 20min if not, plus/minus a buffer determined at local implementation 35 Advisory includes expected time for future mode transitions, indication of A/C separation minimum applicable 36 A problem for setting a landing rate in advance is weather persistence FINAL Page 76

92 ATC Supervisor, which selects the minimum required separation between A/C in arrival or departure operations. ATC-Wake Predictor. This component is the whole real-time subsystem used to assess the suitability of the separations provided by the SMP (ICAO or reduced). It predicts for individual A/C the WV behaviour in the predefined arrival or departure area(s). This information is provided to ATC through the ATC-Wake HMI (see below), using the ATC-Wake tool called Wake Vortex Vector (WVV) 37. The main inputs for this component come from: ATC-Wake Detector (WV position and extent) Weather monitoring/now-casting systems Airport surveillance systems (radar, aircraft type, ID, transponder code) A/C Sequencing Manager (AMAN/DMAN sequencing data) Databases describing airport layout (runways) and A/C characteristics (span, weights) Since the quality of WV prediction is directly related to the quality of input data (MET, radar), a safety buffer has to be applied to satisfy accuracy requirements of ATC users. The prediction is updated in short intervals (e.g. 1min) and is evaluated/ assessed by measurements of WV behaviour of preceding A/C. The ATC-Wake Prediction algorithm is based on the main prediction models developed so far, which are: Probabilistic Two-Phase (P2P) 38. Probabilistic WV transport and decay model. Its model equations are derived from the solution of the space-temporal circulation evolution of a decaying potential vortex and are adapted to WV behaviour as observed in experiments. Vortex Forecast System (VFS) 39. Deterministic WV transport and decay model, based on the method of discrete vortices or vortex particles which are used to model the A/C wake vortex ( primary WV) and the WV generated near the ground when IGE ( secondary WV). P-VFS 40. Upper software layer for a probabilistic use of the VFS. It is based on Monte Carlo type simulations, using uncertainties/variations of: the A/C generator parameters, the input weather profiles and the model coefficients. ATC-Wake Detector. This component detects for individual A/C the WV position, extent (vortex vector) and if possible its strength in the pre-defined arrival or departure area(s). The detection is performed using ground-based 41 WV sensors, which scan pre-defined parts of the considered critical area (e.g. ILS glide path) in pre-defined windows. ATC-Wake Monitoring and Alerting. This component alerts the ATCO in case of : 37 The WV Vector indicates the part of the critical area (e.g. ILS Glide Slope) potentially affected by the wake vortex 38 Developed by DLR (Germany) 39 Developed by partners from Russia (SABIGO), Belgium (UCL) and Canada (OTI, Yaras of Carleton) and funded by Transport Canada ( ) 40 Developed by UCL 41 No connection to airborne equipment is assumed but detection may be complemented using airborne equipment FINAL Page 77

93 significant deviation between WV detection and WV prediction information which increases the risk of WV encounter; or failure of one or several WV components This component can be considered as the safety net for ATC-Wake operations. Its design must be kept simple, as it does not assume the existence of a connection to airborne equipment and the use of aircraft behaviour model for WV encounter. ATC-Wake HMI. This component is planned to be integrated in the current ATCO HMI and provide controllers with the required interface with the other components of the ATC-Wake system. In particular, the WVV generated by the Predictor is presented as an enhancement on the Plan View Display (PVD), which shows the information received from the airport radars combined with flight track data (A/C type, height, speed, etc). Figure 12 shows a high level functional overview of the ATC-Wake system including the main components described above. Figure 12: High level functional overview of the ATC-Wake System Impacts on the CNS/ATM System The following paragraphs briefly describe the impacts that the ATC-Wake system implementation may cause on the CNS/ATM functional blocks. ATM Blocks AEP (see ). There will be a need of adaptation of approach/departure procedures and MET data processing. Besides, ATIS shall publish applicability and planning of ATC-Wake separations. FINAL Page 78