Air traffic control problems in Europe

lournal of Air Transport Management 1994 l(3) 165-177

Air traffk control problems in Europe Their consequences and proposed solutions

Amab Majumdar Centre for Transport Studies, Department London, London SW7 2BU, UK

of Civil Engineering,

hperial

College,

University

of

The air trafftc control (ATC) system over Europe faces increasing pressure every year, leading to frustrating delays, and threatening the potential gains from liberalization of Europe’s skies. This paper initially outlines the limitations of the main elements involved in ATC. The congestion of the aerial corridors over Europe is considered in terms of the factors hampering the effective use of the skies for civil aviation. The solutions and institutional frameworks offered to overcome the problem are discussed, together with the progress made so far. Similar congestion problems in Europe’s airports, and the strategies to improve capacity safely there to integrate with ATC harmonization, are noted. Finally, in considering a totally new approach to European ATC for the future, the use of satellites is considered. Keywords: Europe, air traffic control, harmonization,

The deregulation of the domestic aviation market in the USA, legislated by the Airline Deregulation Act of 1978, brought gains to both consumers and producers in the industry - estimated to be between $13.7 and $19.7 billion since 1990 (Anon, 1993a) as well as causing a great upheaval in the industry, as witnessed by the mergers and concentration in the airline business. These ideas crossed over the Atlantic to Europe in the mid-1980s, despite the differences in demography, economy and politics. The European Community (EC) began the process of liberalization of the airline industry with its First Aviation Package of 1987. A further package of liberalizing measures kept up the momentum in 1989, but the most important breakthroughs came with the Third Aviation Package, in effect since 1 January 1993, giving rise to a Single European Market in air transport. This gave three significant rights to airlines (Anon, 1993b): l l

l

the right to set fares; the right to an operating licence anywhere the EC for any airline meeting common nationality and financial fitness criteria; the right to ‘consecutive cabotage’ airline from one country to operate

0%9-6997/94/0~16~13

0 1994 Butte~orth-Heinemann

within safety, for an limited Ltd

integration, satellites

capacity on onward domestic route sectors in other member countries. Full cabotage - the right of any airline to fly anywhere in the EC becomes effective only from 1 April 1997. Simultaneously, the airline industry in Europe is undergoing dramatic changes. This can be seen both in the attempted mergers between the airlines to gain secure footholds for future global competition, and in their attempts to restructure and reduce costs in the face of a harsh economic climate and reductions in state aid. This much-vaunted liberalization of European air transport faces a huge technical barrier to any benefits that may accrue from the freer market: the adequate provision and allocation of aviation infrastructure in a liberalized market. Demand growth, and the need to cope with it efficiently, was seen by some as the justification for market liberalization. However, it is now the constraints on the supply side that pose the problem, and there is a need to make more efficient use of the infrastructure available and ensure that proper investment occurs in additional facilities to meet future demands. In fact, one argument for a gradual process of deregulation of Europe’s skies has been the need to 165

Air traffic control problems

in Europe: A Majumdar

ensure that the basic infrastructure is adequate to cope with the additional traffic that is the inevitable companion of a more liberal regime. The European Commission in 1989 stated that the capacity of the existing air transport infrastructure, and the way in which it is operated, placed a constraint on the longer-term development of aviation. More recently, the European Commission’s ComitC des Sages - the ‘Wise Men’ who studied the problems facing Europe’s airlines and attempted remedies cited the lack of an integrated air traffic control (ATC) system as one of the main contributors to the high costs faced by the airlines (Anon, 1993~). The major congestion problems that Europe faces were outlined by Norman Jackson of IATA (Wheatcroft and Lipman, 1990): .

. .

some 30 sovereign states with diverse national strategies for airspace management and equipment procurements methods; an inaccurate medium- and long-term forecast; liberalization, creating new demand; a limit to available airspace; multiple user classes of airspace; fragmented and uncoordinated flow control; shortage of ATS (air traffic system) ground facilities, and unreliable equipment; six major runway-limited airports; several airports at or near terminal saturation.

This paper considers, first, the problems affecting Europe’s skies - both the consequences and causes - and then considers the cost of this inefficient ATC system. The proposed solutions, together with the responsible bodies and the institutional arrangements for their implementation, are outlined. The problems of airport congestion are also considered briefly, as are satellite solutions for ATC of the next century.

The problems Consequences Air traffic has doubled in Europe over the last decade, much in excess of the predictions upon which the developments of national ATC systems were based. For example, the average annual growth rate in the period 1985-1990 was 7.1%, while the official document ~Eurocontrol, 1987) intended for policy making had predicted this growth to be just 2.4% annually. A recent study (ATAG, 1992), forecasts that the total number of flights in Western Europe will increase by 54% from 1990 to 2000, and by 110% from 1990 to 2010. This means that there will be more than 11 million flights a year in Western Europe. In 1990, 85% of the flights recorded within Western Europe were internal to the area. This figure rises to 90% when traffic figures from the Central European States, now members of the European Civil Aviation Conference (ECAC), are included: that is, there were 4.8 million flights across 166

or within Europe. This ‘domestic’ traffic is not evenly spread throughout the continent. There exists a core area where the density of traffic is highest, and modelling studies show a considerable expansion of this high traffic-density area in Europe. This will lead to a situation of almost impossible aircraft density where the skies are busiest over Europe. An ever-increasing workload will be placed on the ATC network in Europe, where current traffic levels frequently exceed the ATC capacity as currently organized and equipped. This leads to the use of air traffic flow management (ATFM) techniques, with its accompanying delays and cancellations. While there are several sources of delay data and definitions of delay avaiIable in Europe, it is certain that every air traveller will have experienced the inconvenience of a delayed flight in Europe. Detailed statistics from the CFMU (Central Flow Management Unit) at Eurocontrol about traffic flows inbound to the UK on Fridays in July 1992 indicate that 57% of the flights were delayed by an average of 25 min. Even on relatively quiet winter Fridays (22 and 29 January 1993), 47% of flights were delayed by an average of 17 min (Duytschaever, 1993). Airlines also are not enamoured by the situation. Hume (1990) noted that the introduction of ATFM principles in 1980 was directed at ensuring that temporary or isolated sector overloads could be handled by ATC, with ATFM activated only when broad, prolonged overloads were expected. However, by 1990 the situation had reversed, with ATFM active throughout 16 hours or more each day: a state of affairs that ‘the system as such was never intended or planned to cope with... and the results are seen in a variety of forms, including departure delays’ (Hume, 1990). Causes and costs The main cause of the problem is the fact that Europe lacks a single, integrated ATC system. With the tradition for national control of aviation infrastructure ownership, financing and operation, civil airspace control is by the national civil aviation authorities. While ICAO’s (International Civil Aviation Organisation) European Air Navigation Planning Group, with support from Eurocontrol, attempts to coordinate national plans, there has never been any supranational decision-making role. Governments own and operate ATC facilities, a fact that does not lead to the most market-oriented management methods. Too often, equipment procurement is tied into general public sector capital acquisition programmes. The consequences of this are that: l

* l

modem technology updates are difficult acquire; national suppliers are preferred; system compatibility is by no means assured.

to

Journal of Air Transport ~unageme~t 1994 Volume I Number 3

Air traffic control problems in Europe: A Majumdar

In addition, controllers are treated as civil servants, locked into relatively rigid pay and service conditions, thereby preventing the kind of flexibility required for effective response to daily and seasonal fluctuations in demand and, furthermore, limiting the number of entrants into the profession, with the accompanying staff shortages. The member nations of ECAC, an organization whose objective is to coordinate and harmonize the civil aviation policies of member countries in all aspects of civil aviation where multilateral coordination is useful, have 22 different, often tiny, ATC networks. Each uses its own procedures and its own brand of equipment. Coverage is provided by no fewer than 51 ATC centres, whose boundaries are defined by national, rather than logical, parameters. Added complexity is provided by those centres using some 31 different ATC systems, using computers from 18 different manufacturers with 22 different operating systems and 33 different programming languages. The national divisions mean that not only does Europe carve up its airspace into a patchwork of divisions to be managed by too many ATC centres, but also air routes are drawn to follow designated national airspace divisions. Contrast this with the USA, where airspace nearly twice that of Europe is controlled using a single, integrated system for en-route traffic operated out of 20 centres. Radar data often cannot be shared, owing to either incompatible or non-existent equipment, or to the catch-all phrase of ‘national security concerns’. Some areas, indeed, have no radar coverage at all, forcing planes to fly up to 12 times further apart in some parts of Europe than elsewhere. These gaps in radar coverage create traffic bottlenecks that affect the entire flow of planes over Europe. Even across borders of states with highly developed ATC systems, such as the UK and France, the computers are incompatible, forcing controllers to telephone colleagues across the border to hand over control of a plane to the next ATC centre. This in turn reduces the productivity of the controller. A further major problem that Europe faces is that air routes have to be chosen so as to avoid the

Table 1 Costs of ATC inefficiency

The costs of air traffic control ineffkiency Europe pays a heavy price for this inefficiency. A study by Wilmer, Cutler and Pickering (Lange, 1989) calculated the avoidable cost to Europe of this fragmentation, for the first time, to be over US$5 billion in 1988 alone. This colossal figure breaks down into five principal types of cost, as shown in Table 1. The make-up of these costs is discussed below. It is worth bearing in mind that the calculations are in 1988 US$ prices. Peak period delays tripled between 1986 and 1987, and then again between 1987 and 1988. In 1988 alone, Europe suffered over 330 000 hours of ATC-caused departure delay. For the airlines, the cost was around US$970 million, in the form of

in US$ million

Cost element

User

Delay Inefficient routing Non-optimal flight profiles Lower ATC productivity Macroeconomic costs to the European

540 510

Other

970 1 270 650 600 400

1 050 Lange

Airline

economy

Total Source:

airspace reserved for military uses. Huge tracts of airspace are reserved for military use, forcing planes to fly miles out of their way to get from one airport to another. Because of this, a plane flying from Brussels to Zurich has to follow a routing 45% longer than the minimum. The average European flight is 10% longer than necessary. The European Commission (1989) noted that the inherent deficiencies of the ATC system can be attributed, in the main, to the resistance of the Member States - and the ECAC countries - to ‘relinquish any part of their national sovereignty’, as recognized by the Chicago Convention. These divisions in today’s Europe, both national boundaries and military use, are part of an outdated aeropolitical concept. There should be no ‘military’ or ‘civilian’ airspace; rather there is one European airspace to which various categories of flight - civil and military, commercial and recreational, jumbojet and turbo-prop - need access (Anon, 1993d). The legacy of this past thinking has been to leave Europe with a costly ATC system, which both compromises the traditionally high safety standards in Europe, and puts into jeopardy the gains from liberalization. David Moss, President of ECAC, has noted that ‘full enjoyment of the benefits of liberalization depends upon successful completion of.. ECAC’s strategy for redevelopment of air traffic management in Europe’ (Moss, 1992).

2890

loo0

Total 1500 1800 650 600 400 5000

(1989) p 4

Journal of Air Transport Management 1994 Volume I Number 3

167

Air traffic control problems in Europe: A Majumdar

Eurocontrol

extra fuel, salaries, maintenance, interest and the like. The cost to passengers amounted to US$540 million, obtained by determining the weighted average time value of US$21.50 per hour per passenger, on the basis of estimates of the amount of business and leisure travel and their respective prevailing European values of time, and multiplying this by 330000 hours of excess ATC delay. The combined cost of these ATC delays was about US$1.5 billion. The tortuous air routes caused by following national borders rather than logical routes, coupled with military restrictions, cause the average flight to be 10% longer than it need be. This routing network cost the airlines US$1.27 billion and the travelling public US$510 million, a combined total of US$1.8 billion in unnecessary cost in just one year alone. A flight profile is the vertical path that a plane follows up to its cruising altitude and back down to its landing. The most fuel-efficient profile is to move directly up to a high altitude, level off, and then coast down towards the destination. Unfortunately this is not possible, as the various states of Europe impose different definitions of where upper airspace begins, requiring planes to make frequent changes of flight profile as they pass from one jurisdiction to another. This then adds an extra operational cost to airlines of US$650 million per year. The average European air traffic controller is about 5060% less productive than his American counterpart; this is not due to laziness or lack of training, but because they face the double handicap of lack of automation and lack of system integration. This results in each international flight being handled far more times by far more controllers, with tremendous time cost for coordination, as compared with the USA. The most difficult costs to determine are the macroeconomic costs to the European economy. These are costs that inadequate ATC networks impose in terms of diminished productivity and competitiveness. In addition, there are also costs due to diminished or substituted choices for consumers, and other ‘secondary effects’. The value of US$400 million may well be a gross underestimate of the actual amount. These figures are still reasonably valid in 1994, five years after the study was completed. Much improvement has been made in reducing delays in recent years. Air routes, however, still follow national boundaries, and little real progress has been made in obtaining military airspace for civilian purposes. Only now is there a move towards compatibility of ATC equipment to improve controller efficiency. These costs are transferred back to the passenger, who in addition to the time delays and attendant frustration, finds that the $5 billion delay in flights is equivalent an average increase in ticket prices of 8% (Anon, 1993e).

Eurocontrol - the European Organization for the Safety of Air Navigation - was established in 1960 to integrate European civil ATC. Differences between its constituent states, as well as the limited number of participants, prevented it from fulfilling this role. It served primarily as a charges collection agency, in addition to being a research and training institution. Only its Maastricht Control Centre carries out control functions for the Benelux states. At present, there are 18 Member States, and the organization has six major establishments spread throughout the Benelux countries and France. The deteriorating situation in the European airspace in the second half of the 1980s led ECAC, on 20 October 1988, to ask Eurocontrol to create and operate on their behalf a central flow management unit (CFMU) to undertake ATFM throughout their airspace. By then, the States of the European region of the International Civil Aviation Organization (ICAO) had developed the centralized traffic management organization concept, which proposed a single flow management unit with liaison positions flow management positions - in every ATC centre. The Permanent Commission of Eurocontrol approved a CFMU implementation plan at its meeting of 4 July 1989. This envisaged the creation of the CFMU, a Eurocontrol body, to provide ATFM services throughout the airspace of the ECAC States. Initially, the CFMU plan was to apply to the 23 States of Western Europe that were members of ECAC. The decision by Eurocontrol on 3 December 1991, that the CFMU implementation plan should apply to the airspace of any State that had become an ECAC member since 4 July 1989 and which so requested, has seen requests from exCommunist states to participate in the CFMU. The project now covers 28 ECAC States. It is unreasonable to expect the ICAO concept of a centralized system to be created overnight. Therefore, as a first step, the decision was made in April 1989 to ensure that five of the then twelve flow management units work together to give the appearance to users of a service that is centralized. The coordinating units were those in London, Madrid, Paris, Frankfurt and Rome. These, together with Eurocontrol, constitute the Central Executive Unit (West) (CEU(W)). Ultimately, a single CFMU will evolve, connected through flow management positions to all the area control centres it serves. The number of area control centres in the area is 55. Recent years have seen ATFM forced to become a very specific activity, developing in parallel with, and also in support of, ATC, leading to the use of new techniques, tools and operational skills. ATFM acts both on sets of flights constituting traffic flows, as well as on individual flights.

168

Journal of Air Transport Management 1994 Volume I Number 3

Eurocontrol

and its role

Air trafic contr& problems in Europe: A Majumdar There are two major ways in which ATFM acts: at the strategic level, and at the tactical level. Strategic ATFM, Actions are planned a long time in advance, and activities are directed towards resolving major problems of imbalance between demand and capacity. Months in advance, demand data obtained from planned flight data provided by aircraft operators are assembled in the Data Bank at Eurocontrol. Treatment of this data in the mainframe system provides estimates of traffic loads over any critical navigation point or in any ATC sector in Europe. The results are then discussed with all parties involved in this process - States and aircraft operators -with the consequence that major orientations of traffic flow in the European continent are agreed upon. This process typically begins in October of year N - 1, coming to fruition in February of year ZV,and ends with the application of the resulting traffic orientation scheme published by every State of the region - in the Summer period of year iV. A notable success of this process has been to ameliorate the effect of major political issues on air traffic, such as the crisis in the former Yugoslavia, by the reorientation of air traffic flow around the areas affected. As time progresses, the database is updated by the introduction of additional flight information received from the aircraft operators, such as repetitive flight plans containing information about the route flown, and ‘late change’ messages reporting on the cancellation of flights and planning of additional flights. Pre-tactical ATFM plan. Such a plan is developed on the basis of these improved data, together with the strength of comparative evaluation of traffic situations archived on a similar day some time in the past, and taking into account the latest information about capacity available in the area control centres. The aim of this plan is to define the restrictions to be applied to traffic flows on the following day, and it is established by the five flow management units of the CEU(W) and published around mid-day each day in the form of an ATFM notification message, available to more than 1000 addressees over the world: air traffic services and aircraft operators. It details the tactical ATFM measures that will be in force the next day. Tactical ATFM_ This adapts plans and implements measures to deal with imminent solutions. On the day of operation, air traffic flow controllers apply the measures announced and monitor whether the pre-tactical plan is having the desired effect. This is at present undertaken in a decentralized manner by the five flow management units of the CEU(W), and is based on the application of ‘acceptance rates’: the number of aircraft per unit time that will be allowed to enter from a particular area of origin into fournal

of&r

Thmsport

~unagement

I994 V&me

I Number

3

a specified congested area. Aircraft through a congested area request appropriate flow management unit, issues a slot in the form of a period There are two serious flaws in this l

l

planning to fly a slot from the which normally departure time. process:

underutilization of available capacity - the rates may be set too low, or there may be no demand equivalent to the delegated rate from a particuIar area; serious overload conditions - there may be inefficient cooperation between ATC and ATFM, or rates may be applied by issuing departure slots to aircraft that are sometimes hours away from the congested area, or aircraft operators may behave incorrectly.

The future CFMU system will organize tactical ATFM in a quite different manner, owing to the availability of flight plan information provided by the Initial Flight Plan Processing System (IFPS). The States taking part in the CFMU project have agreed to strict flight plan filing procedures, thereby ensuring that the tactical database contains complete information, at the appropriate time, about all intended movements in the area. The requirement for ATFM slots can then be dropped, and in fact slots based on available flight plan data will if required be issued automatically to those concerned about a couple of hours before estimated off-blocks time by a computer-assisted slot allocation programme: part of the tactical facilities of the CFMU. The Central Flow Management Unit (CFMU) Project The central flow management implementation plan (Eurocontrol, 1989) has led to the construction of new buildings at Haren, near Brussels Airport, housing the CFMU. All operational, technical and administrative functions are co-located. In early 1994 the CFMU moved to this new site. Furthermore, for security reasons, new premises on the site of Eurocontrol’s experimental centre at Bretigny-sur-Orge will house a second IFPS unit. While the IFPS is an essential element in the central flow management concept, it is also a crucial step in creating a harmonized and integrated ATC system within the airspace of the ECAC States. At present, flight plans are filed by aircraft operators and then sent by a dedicated aeronautical fixed telecommunication network to all air traffic services involved with a particular flight. These flight plans often contain errors both in contents and in syntax (an internationally agreed ICAO format must be followed), causing them to be corrected manually before they are introduced into the flight dataprocessing systems of the national ATC systems. This causes a European flight plan to be processed 2.7 times, on average, by local flight plan processing systems: a business involving hundreds of people. 169

Air traffic control problems in Europe: A Majumdar

The IFPS is to be a unique system in which all flight plans of the European environment will be received, corrected and distributed to all systems requiring them. The uniqueness of the system, together with the fact that the flight plans are essential for the operation of ATC, mean that the IFPS is designed as a high-availability system, with nearzero probability of breakdown. This arduous task will be achieved by the following means: The IFPS units will be duplicated. Two geographically separated, identical, high-availability units will be provided, connected by a network that provides fall-back communication paths. Each unit should normally process about half the total number of flight plans in the ECAC area, but should one break down, the other will be in a position to take over. The users of both IFPS units will be connected through the use of a high-availability data communications network.

l

l

The IFPS is being developed on modern workstations. The operating system is UNIX, the application programs are being written in Ada and the database in Oracle. The software production and integration has progressed well, and an acceptance task force is undertaking test sessions. Work is still required to link the IFPS to all national ATC systems, and the planned date operation is 1 March 1994. The provision of data processing systems will provide the tools used in ATFM. They will be kept in a powerful mainframe configuration and in a second workstation environment, identical to the one used for the IFPS. In addition there is the development of software facilities for undertaking ATFM activities, the provision of voice and data communication networks that will link the CFMU with all its partners (flow management positions and aircraft operators), and the build-up of a staff complement. The total investment costs have been estimated at 75.6 million ECU, cumulative from 1989 to 1993, and the annual operating costs will be about 42 million ECU from 1994 onwards. The mainframe houses the strategic database, together with the archives, and provides ATS environment data to all CFMU systems. The workstation environment contains the tactical database - flight plan data for the next 48 hours and houses the CASA program, providing a userfriendly interface for the air traffic flow controller. The plan is for the tactical system to be put into operation through a carefully planned transition process in a series of sequential closures, as follows: Date

Location

1 May 1994 1 October 1994 1 January 1995 1 April 1995 1 October 1995

Paris Frankfurt London Rome Madrid

170

This process is slightly behind target at present. Tactical operations will therefore be transferred from the five flow management units to the CFMU and, under this plan, all other flow management units will become flow management positions. These will be established in each area control centre and will provide the link between ATFM operations in Brussels and the real-life ATC environment as it is experienced in Europe. At present, 53 terminals of the CFMU system have been installed, mostly at future flow management position sites. There will be a need for more as all users are linked to the CFMU through a data communication network. Aircraft operators will supply their own terminals connected mainly via the (SociCtC Internationale SITA des Telecommunications Aeronautiques) network, a proprietary data network for airlines. Eurocontrol has studied the future needs for data communications facilities (between the CFMU and its clients - ATC units, airport reporting offices, other ATS services, and aircraft operators) and contracts have been placed so as to provide the communication means required. Stringent service levels are demanded regarding availability, capacity, performance and security, as appropriate, in critical ATC/ATFM operations. Discussions with the national administrations have led to an agreement to adapt the existing ATS communication systems for CFMU voice communication requirements.

ECAC strategy The ECAC

strategy:

EATCHIP

Against this backdrop, ICAO published its global communication, navigation and surveillance/air traffic management concept in 1988 - endorsed by the ICAO Tenth Air Navigation Conference in September 1991 - whose main item was the recognition that emerging technologies, based on air-ground data communications, had the potential to enhance air traffic management globally. The ICAO European Air Navigation Planning Group undertook a study of a ‘daughter concept’ specifically tailored for the region, known as the Future European Air Traffic Management System (FEATS). Published in 1989, this addressed the required technical and operational developments for Europe through to the year 2005 and beyond. However, while the European air traffic administrations accepted the operational and technical recommendations, the FEATS concept, in common with other ICAO recommendations, relies upon the States’ own initiatives for implementation. Therefore, without the necessary political will to introduce new systems, their implementation will be sporadic, and the advantages to be gained from the envisaged seamless advanced system across the continent will take an unquantifiable time to Journal of Air Transport Management

1994 Volume I Number 3

Air traffic control problems

achieve. Hence the political commitment to a panEuropean air traffic management implementation strategy was sought via ECAC. ECAC, set up in 1956 under the transport ministers of the majority of European States, has the remit to deal with all aspects of civil aviation (administrative, regulatory etc). The collapse of Communism in Eastern Europe increased the number of Member States to 31. It is by harnessing the political will of this ministerial-level body that European States aim to change the current European infrastructure and enhance system capacity to cope with the demands of the next century. The Directors General of Civil Aviation Authorities of the ECAC States, taking the FEATS concept as a basis, developed an ATC strategy for the 1990s which the Ministers of Transport of the then 23 ECAC states adopted in April 1990 (ECAC, 1990). Therefore, the political commitment was provided to harmonize and progressively integrate the patchwork of different ATC systems across Europe: a commitment reaffirmed in March 1992 by the Ministers. The overall objective of this strategy, according to Marten (1993), is to provide increasing airspace and control capacity, while maintaining a high level of safety. ECAC’s role is to provide the required impetus and acceleration to reach, as quickly as is safely feasible, a harmonized level of performance and integration of the 31 States’ national airspace/ATC systems. In order to satisfy this overall objective of increased capacity within the European air traffic management system, ECAC set broad operational objectives, with the latest possible target dates indicated, as outlined in Table 2. It is to achieve these operational objectives that the ECAC strategy sets the following implementation objectives:

Table 2 Operational

in Europe: A Majumdar

to optimize the provision and use of the radar surveillance function by installing new facilities or sharing radar data; to make ATC communications more efficient and extend the exchange of data between ATC computers by applying common specifications and installing new equipment; to improve airspace management by implementing new airspace and route structures, common procedures, and adequate system support; to harmonize the development and implementation of the various technical components of ATC systems by adopting common standards and specifications; to define guidelines for the selection, training and licensing of air traffic services staff in ECAC Member States. ECAC selected Eurocontrol to manage the implementation of the strategy. Eurocontrol was established in 1960, the original intention being to integrate European civil ATC. However, differences between its constituent states, together with the limited number of participants, mean that it served primarily as a charges collection agency as well as a research and training institution. As of June 1994, there were 18 Member States, mainly in Western Europe, though states of Eastern Europe have applied to join in the future. The European ATC Harmonization and Integration Programme (EATCHIP) was established, in late 1990, by Eurocontrol as the means to implement the strategy for the en-route environment. EATCHIP is overseen for ECAC by a project board made up of senior officials from the ECAC States, and encompasses the entire ECAC area. It comprises four overlapping phases (Marten, 1993):

objectives of the ECAC strategy

Objective

Latest completion date

Optimization of the air traffic services route network and airspace structure, supported by a widespread application of area navigation

1993

Completion

1995

of comprehensive

radar coverage throughout

the continental ECAC area

Application of en-route radar separation of 5 nm in high-density areas 10 nm elsewhere

1995

Harmonization of ATC systems in high-density areas elsewhere

1995 1998

Leads to progressive integration Completion

of automatic data communication

Operation of Mode S air-ground

between air traffic control centres

data link in central area

1998 1998

Nore: nm is nautical miles Source: Marten (1993) Journal of Air Transport Management 1994 Volume 1 Number 3

171

Air traffic control problems Phase I: Appraisal systems 1990-1991.

in Europe: A Majumdar

evaluation of national

and

This phase, already complete, procedures, airspace considered equipment, methods, and civil/military design, training coordination methods. A wide range of deficiencies were identified (Eurocontrol, 1991). Phase

II:

Programme

development

1991-l

993.

Completed in 1993, this phase charts the direction taken towards harmonization and integration of the currently diverse ATC systems by drawing together the various national air traffic management development plans into a cohesive European plan. Phase III: 1993-1995.

Acquisition

and

implementation

This phase sees the replacement and upgrading of existing systems to achieve the required interfaces between systems. The UK’s contribution to this phase will be the Civil Aviation Authority’s (CAA) new en-route centre at Swanwick, Hampshire. Phase IV: implementation of the future air traffic management system 199.5-2000 and beyond.

Definition of the needs of the future air traffic management by system is to be done Eurocontrol, and requires the cooperation of the ECAC Member States, European industry and the European Commission. Work on the initial outline of the future European Air Traffic Management System has already begun. Only Phase I had a definite completion date, which was achieved. The other phases have no fixed start and end dates and, indeed, Phases II and III were considered before Phase I, with a number of countries launching individual projects to enhance their ATC systems.’ The navigation aspects of EATCHIP are directly related to future airspace developments (Marten, 1993) with 1998 a significant year as the carriage of area navigation (RNAV) equipment in aircraft will be mandatory in the ECAC states. The era of RNAV after 1998 should bring the following benefits: . l

.

reduced separation between routes; the possibility of some random operations in the en-route phase of flight; systematic offset operations in support of reduced vertical separation above FL 290.

Exploiting the full capability of RNAV will allow the UK and adjacent airspace capacity to be significantly improved without compromising safety. With RNAV being introduced in an evolutionary manner, the maximum benefit to operators can be provided as soon as practicable, without the need for unrealistic re-equipment programmes, and should allow a rationalization of the provision of ground-based navigation aids. ‘Private communication with EATCHIP Planning Division

172

Mr

Robijns,

Principal

Expert,

EATCHIP requires the full commitment and active participation of all the countries within the ECAC area. Each country is individually responsible for all the necessary investments to ensure the implementation of the changes required to their own system. To ensure the timely implementation of each of EATCHIP’s four phases, centralized management is also required, this being provided by Eurocontrol. National administrations are represented at the EATCHIP project board and liaison officer levels. There are two UK members on the project board, and at the liaison level work is coordinated with the CAA and industry. European Air Traffic Management System The ECAC strategy gives a timeframe for imple-

menting the longer-term future air traffic management system, commencing in the 1995-2000 period and stretching into the 21st century. The emphasis is upon extensive automated support for the controller, including enhanced air-ground and ground-ground data communications using Mode S (selective secondary surveillance radar), aeronautical mobile satellite services and, in some areas, VHF (very high frequency), with the aeronautical telecommunications network (ATN) providing the interface system. The fourth phase of EATCHIP has been named the European Air Traffic Management System (EATMS). Its principal objective is to provide the forecast extra capacity required for the turn of the century, and to have the flexibility for further expansion in traffic growth. It is based on the integration of the airborne and ground-based components of the future system, supported by extensive automation and enhanced data communications made available by the ATN. At the beginning of the timeframe (possibly 2000), the following should be in place, due to Phase III: l

l

l

l

l

installation of new enhanced air traffic management and avionics equipment; continued implementation of new route and airspace structures, and development of common procedures and system support functions; implementation of harmonization measures throughout the continental ECAC area and progressive integration of ATS systems; start of implementation of air-ground data-link facilities; development of proposals to ensure that planning for the continental ECAC area is coherent with that of adjoining areas.

The EATMS concept provides a target focal point towards which harmonization will converge, and the concept is based on an infrastructure that will remove current deficiencies, bring the benefits of up-to-date technologies, and allow the rational use of resources (Marten, 1993). Journal of Air Transport Management 1994 Volume I Number 3

Air traffic control problems

Achieving agreement on what the EATMS should be and how it should be implemented will not be easy (Anon, 1993f). There is a growing lobby in favour of a system based entirely upon navigation satellites. There is a belief that a global satellite navigation system based either on an existing or on a new system altogether would solve both air- and ground-based ATC problems simultaneously. Such a solution could also be cheaper in the long run. Whatever system is finally chosen, the pressure for an immediate solution to the ATC problems in Europe led Germany in 1992 to propose that work on a unified system begin now, rather than at the EATCHIP completion date in mid-decade, and to define in detail the nature of the future system as it should develop over the 1995/98-2010 timeframe. The need for a common agreed concept for a future air traffic management system, thereby allowing an upgrade of the existing system and a definition of a modernization plan, is recognized in Europe: in itself enabling an evolutionary change for the next generation of ATC. The ability of the EATMS to handle vastly more air traffic daily than at present has led to a review of the fundamental assumptions underlying the present system, including the delineation of airspace sectors along national boundaries. The need to sectorize according to the flow of traffic, rather than national boundaries, has been recognized (Anon, 1993f). More efficient aircraft-ground communications through the development of more reliable digital (in comparison to analogue techniques) data-link services should lead to another fundamental improvement. The present procedures have reached their limit, and the use of modern flight-management systems and satellite-based global positioning systems - with their global cover providing a medium for air-ground communication, surveillance and navigation - should allow aircrews to predict their position with greater accuracy than with the radars in current use. Therefore the potential exists to reduce the present extensive networks of groundbased en-route navigation aids. If the exact position of an aircraft is known and its future position can be predicted, then its arrival time at any point in the system can be forecast to an accuracy within 1 min. The present 10-20 min accuracy leads to uncertainty within that period that the aircraft will be separated by a certain safe amount. The use of such air-derived information to locate aircraft will allow planning for a huge increase in capacity, as trajectories could be planned much better than they are today. A potential conflict would then be solved several sectors away. This revolutionizes the air traffic controllers’ task and, in the process, reduces the number of potential conflicts, as they will no longer have to deal with every single aircraft as at present, but can concenJournal of Air Transport Management

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in Europe: A Majuma’ar

trate fully upon traffic that is causing problems. The controller will have greater reliance upon automation, the system being outside his mental capability to consider thoroughly with the required safety. Separation criteria will be applied between trajectories rather than between aircraft, and if the trajectories do not conflict then there is no reason for the controllers to be involved. The controllers remain important, and have been involved at every stage in the development of the EATMS, as the move is made from a rule-oriented to a knowledge-oriented system, to offer better resolution strategies (Anon, 1993f). The EATMS therefore can be used to control aircraft accurately in four dimensions, providing conflict-free paths between departure and destination in the form of 4D profiles to be adhered to by the aircraft. All aircraft in the system will be equipped with P-RNAV equipment, which will contain updated flight plan data, and will exchange it with the ground through the communication system. The anticipated accuracy in time of a flight in 4D will be of the order of a few seconds within a timeframe of 30 min. The navigation equipment will also be able to accept and process meteorological data from the ground to refine flight profile calculations (Marten, 1993). The USA is also pursuing the concept of directing an aircraft along the ‘best trajectory’, and the European and US efforts are being coordinated with the Federal Aviation Authority (FAA). In addition, the EATMS work is also being coordinated with the much wider scope of the ICAO’s Future Air Navigation System (FANS), which aims to develop a global ATC system for the next century, providing an optimum mix of satellite technology with the best line-of-sight systems. Eurocontrol illustrate how a flight under the EATMS would be managed, involving a minimum of 28 events from initial planning to the disposal of data at the end of the flight. Most noticeable in this sequence is the level of automation required, which depends on the provision of highly reliable computers and the software to make the system work, to which much research is now directed. Doubts persist about the military’s inclusion in the EATMS as it involves the cooperation of the military and civil authorities, because civil trajectories cannot be made independently of military movements. While Eurocontrol promises to make available appropriate surveillance and flight data to military air-traffic services organizations, even obtaining empty military air space for civil flights at present is no easy task; it involves protracted and high-level negotiations. Preparation is under way for a ‘concept of the flexible use of airspace’, to improve the coordination between civil and military operations. While even this may not be enough, some countries remain resistant to the idea (Anon, 1994a). 173

Air traffic control problems in Europe: A Majumdar

Given that there must be a common design and definition of the system, with possible future provision for contingency aspects for individual nations, or force majeure aspects, the EATMS represents the way forward for ATC in the next century. An energy study done by Eurocontrol considered the additional route lengths that aircraft flew over the past three years, compared with the routes they would fly under the EATMS. The difference is about 7.2%, depending on the country and airline saving about 1.6 million tonnes of fuel in Europe annually. A recent workshop held by Eurocontrol for the EATMS project, including proposed users, has led to Eurocontrol producing drafts of both the context and scope document (CSD) and the user requirements document (URD). Upon comments from the participants to the workshop, Eurocontrol hope to produce the final versions of the CSD and USD in January 1995.2

Airport strategy The steady expansion of air traffic in Europe, with its attendant delays, has produced EATCHIP for the en-route stage as outlined above. This is not enough, as the airport terminals in Europe are in themselves overstretched: a fact that has led to an airports strategy for EATCHIP. In fact, the lack of investment in the early 1980s in this sector is believed by IATA to be costing the national economies US$lO billion a year by 2000 (Anon, 1992). A new airports plan was added to the ECAC transport ministers’ meeting in London in March 1992, with the adoption of the Airports Air Traffic Services Interface (APATSI) report, which details plans for increasing airport capacity - placing particular emphasis on boosting the efficiency of airspace use in terminal manoeuvring areas. The report describes new procedures and equipment to be adopted by 1997, after which the final phase of the strategy will be to integrate the control of airport and en-route traffic - though the hope is that, prior to this integration, the new terminal manoeuvring area procedures will enable a 30% rise in airport capacity. Given the fact that Europe’s airspace is overcrowded, and that the FAA has validated the proposed measures outlined above in the USA, it would seem natural if Europe’s aviation authorities jumped at the chance to implement the proposals. However, the reverse is true; the various national aviation authorities in Europe, especially in the UK, are showing a great deal of caution. One frequently cited reason for this is the greater changeability and unpredictability of the weather in Europe, particularly the UK. The fear is that reducing separations ZPrivate communication with Mr Robijns, EATCHIP Planning Division

174

Principal

Expert,

in such conditions may increase capacity at the expense of safety. Notwithstanding such concerns, the need to increase capacity is unquestionable, and the cooperation of all the protagonists - administrations, airlines and air traffic controllers - will be needed to ensure a safe increase in capacity. The APATSI action programme is closely aligned to EATCHIP to include: l l l

appraisal and evaluation 1992-1993; programme development 1994-1995; implementation 1996-1997 and beyond.

Are satellites the solution to Europe’s ATC problems? There is a belief that satellites will provide the panacea to cure Europe’s aerial congestion. While Eurocontrol envisages a role for satellites, it has not publicly endorsed a totally satellite-based system for the future - partly as it is outside its remit, but also owing to technical and operational questions concerning the use of satellites for precision ATC. Until the end of this century, global positioning satellites (GPS) remain unsuitable for operations in dense air traffic, leading to European reliance on instrument flying rules. The present heavy dependence on ground navigation aid infrastructure, such as VOR (very high frequency omni-directional radar) and DME (distance measuring equipment), has resulted in the bottlenecks in Western Europe and the lack of full utilization of the much greater navigational capability of many aircraft, such as RNAV. A few years ago, the use of US GPS was seen as the solution to long-term ATC problems in Europe. The subsequent changes in the political situation in Eastern Europe have led to a complete revision, with the opening up of new routes and increased traffic movements. The ground navigation equipment situation in Eastern Europe is at present unfavourable, and there is a need to improve it unless space-based navigation is to be the primary navigation system. This, though, will still require the satisfactory resolution of a number of performance and institutional issues. To influence this situation, there has recently been rapid development of the aeronautical mobile services for communications purposes. For surveillance of aircraft, the present civil ATC system in continental airspace is almost entirely radar-based. Secondary surveillance radar (SSR) is the main tool, while primary surveillance radar (PSR) is retained by many administrations for military purposes. However, cost considerations and greater precision and reliability of the data generally available from the monopulse SSRs (M-SSRs) has led some administrations to abandon PSRs and rely exclusively upon M-SSRs, especially for enroute functions. Journal of Air Transport Management

1994 Volume 1 Number 3

Air traffic control problems

Data from the surveillance radar stations is transmitted in a digitized form, but considerable differences exist in both the amount of processing and the performance characteristics of the received data. The surveillance requirements for each point of controlled airspace mean that parts of upper airspace are covered by four or more radars. There are considerable variations in the level of sophistication, between ATC centres, of the radar data processing systems (RDP). Finally, the radar surveillance standards proposed for radars and related RDP systems, when applied to the range of radar stations in current use, show considerable performance differences and efficiencies. EATCHIP outlines measures that will affect surveillance performance, amongst them: definition of standards; optimum utilization of radars, eg a maximum sharing of existing radar facilities; gradual introduction of a standardized RDPS state-of-the-art well-defined and having functionality, level of performance and outputs. A system of this type is under development now ARTAS (ATC radar tracker and server) - which is able to process and perform optimally with positional data from different sources, such as that available from aircraft carrying GPS, together with radar data. It is worth considering the costs associated with radar surveillance, as these are considerable: see Table 3. Therefore to cover European airspace completely with the required redundancy - with no allowances for variations in traffic density - a considerable number of additional radars are needed. Consideration must then be given to various combinations of dependent satellite-assisted and ‘independent’ radar-based surveillance (Cox er al, 1992). Automatic dependent

surveillance

At present, to achieve safe separation, a procedural basis is used (eg North Atlantic operations), leading to much wider route spacings and increased alongtrack separations. ATC monitors the traffic situation in this type of environment by crew position reports via HF (high frequency) radio, the quality of which are affected by various factors, such as erroneous position and/or time information, and communications difficulties. Hence clearances

pertaining on entry to the airspace are often maintained, with little scope for improvements to an aircraft’s operating conditions. There is also the additional risk of a control-loop error. Recent proposals have tried to achieve a more effective means of surveillance and control in the non-radar environment using aeronautical satellites: both as a very reliable relay to transfer timestamped 3-D positional reports from the aircraft to ATC, and as two-way digital communications between pilot and ATC. Such a system is named automatic dependent surveillance (ADS), as it is the aircraft’s navigation system that generates this report. For optimum operation, ADS reports should be: l l

l

Equipment

Replace classical SSR by an M-SSR Install a completely new M-SSR station New PSR with co-mounted M-SSR

of high accuracy; related to the information used to navigate the aircraft when more than one navigation system of comparable performance is carried; received in the ATC centre in a consistent manner and without undue delay.

In principle, ADS reports can also be transferred by VHF in any area having VHF, but no SSR, coverage. Possible combined

surveillance systems

In mixed civil/military high-density traffic areas, radar remains the basis for surveillance. In areas without radar surveillance, dependent surveillance based upon accurate position determination systems, such as GPS, may point the way ahead. In terms of accuracy, GPS (or GLONASS, its Russian equivalent) should give positional data very comparable to that achieved from a multi-radar surveillance system. Even in areas where sufficient radar surveillance capability exists, ADS still has an important role to play, as the following advantages exist when both systems are used together (Cox et al, 1992): l

l

l

l

Table 3 Costs of radar surveillance

in Europe: A Majumdar

ADS can provide supplementary surveillance capability, especially in lower airspace. ADS is a fall-back facility for those parts of airspace with only SSR coverage and where aircraft are temporarily confronted with transponder problems and possible screening of their on-board SSR antenna. Supplementary ADS capability can plug the small gaps in coverage, reducing the number of SSRs needed. Comparisons of the independent radar surveillance and ADS data can ensure the integrity of both data sources.

Total cost in ECU million

Issues concerning global navigation satellite systems

:.5 10

While GPS system performance is undoubtedly high and, in principle, applies globally down to ground level for 24 hours a day, the US Department of

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(GNSS)

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Defense - who own the GPS satellites - can only assure 21 satellites, thereby impairing both integrity monitoring and availability. The problem for Europe is that both GPS and GLONASS were originally devised for military use by their owner countries. Civil users were given access to GPS only in 1991, but since then it has been rapidly adapted to a vast range of civil uses. The major questions now relate to how GNSS services will be controlled to ensure 100% availability for aircraft navigation, along with the provision of infrastructure, and the related services. Reliance upon a system controlled from outside a particular country is an entirely new concept, and Eurocontrol members want to retain control over their air traffic management infrastructure to both regulate traffic and plan ahead. Given the increasing cooperation between European nations, it is inconceivable that control will pass out of European hands (Anon, 1994b). GPS is already under consideration for non-precision approaches, and readily meets the ECAC 1998 requirement for RNAV. However, before it is adopted as a navigational aid for general civil aviation use, there is a need both to develop and to agree international standards for integrity monitoring and to resolve outstanding institutional issues, such as possible cost recovery and safeguarding of a service. continuous The same applies for GLONASS - and indeed a combination of GPS/GLONASS systems will provide additional satellites and may provide an integrity requirement for en-route navigation, once compatibility problems are overcome. Charging for the GNSS services may pose problems, as the system is available to non-aviation users on a different cost structure. One option is a system similar to Eurocontrol’s to collect user fees, with costs allocated to a regional organization, which would then reallocate them according to agreed sharing arrangements (Anon, 1994b). However, the vast range of GPS users should mean that the costs for any individual users should be very small. In fact, the Department of Defense has offered the system to the world at no cost to the user for a period of ten years, while the Russians have offered GLONASS availability free for the next 15 years. Of course, both countries hope that once the systems are used worldwide, the domestic industries in both countries will benefit (Anon, 19938). Nevertheless, doubts remain in Europe as to the military control of both systems - with the associated fear of restricted access in times of crisis and tension - and the fact that the USA, in particular, will have a monopoly on high-accuracy navigation for commercial and military purposes, with concerns over the costs to users after the ten-year ‘honeymoon’. The USA resents doubts over its willingness to make GPS available to the international community, and has promised that any

decision to degrade the signal during a military conflict will be taken at presidential level (Anon, 1994c). In response to claims that Europe is falling behind in GNSS, a tripartite initiative involving Eurocontrol, the EU (European Union) and the European Space Agency has been set up to develop and jointly pursue proposals for a European component of an initial GNSS. This aims to consider the requirements of aviation and take the appropriate action to place Europe in a- position to contribute to the next generation of such systems (Anon, 1994d). But on resolving these issues and on further successful investigations and testing, then GPS and GLONASS could provide a very reliable and precise source of data for aircraft navigation. A prospective sequence for the introduction of GPS in Europe could follow along the following lines (Cox et al, 1992):

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l

l l

GPYADS for specific routes without DMEs or radars by 1995; GPS/ADS extended to radar support; general use for VOR/DME replacement.

ADS operations commencing in the North Atlantic as early as 1995 may be enhanced by GPS, but for en-route navigation in Western Europe GPS was considered as a complete long-term replacement of around-based aids. However. where new routes are ro be developed in areas with little or no ATS infrastructure, GPS-based ADS may provide the best alternative to ground-based systems, the main advantages being: l l l l

route flexibility; ease of implementation; coverage to ground level; costs to ATS related directly to volume of traffic.

In addition, satellite-based systems may complement conventional radar systems, and thereby allow greater use of such systems in the future. Given European reluctance to move to such a system, it may well be ICAO (International Civil Aviation Organization) and the FAA who push Europe to using satellite-based ATC for the next century. One thing is clear: GNSS is here to stay. The USA will see initial implementation, followed by the oceanic and developing parts of the world. While aviation will take the technological lead in developing the system, it will remain one of the smallest users. Conclusions This paper has outlined the need for a harmonized and integrated approach to air traffic control in Europe - a need that has existed for some years, and which is increasing with the predicted traffic growths. But with the liberalization of air traffic in Europe, the urgency is greater as Europe’s airlines

Air trafjk control problems in Europe: A Majumdar

try to survive in a liberalized industry, where the cost of such an inefficient system for ATC is proving a barrier to their improved operations. The EU Wise Men in their final recommendations requested new provisions of the Maastricht Treaty to be activated, releasing funds for a single, unified air traffic management system to replace the present ‘woefully inadequate’ system (Anon, 1994b). What has been impressive with the ECAC (European Civil Aviation Conference) strategy to investigate these problems and result in EATCHIP has been the political commitment. Previous attempts at such an operation, though technically excellent, failed for political reasons. The ECAC strategy adopted in 1990, with the objective of increasing control capacity while maintaining a high level of safety, changed all this. Furthermore, the appropriate institutional arrangements, with their accompanying responsibilities, have been set up: for example, Eurocontrol managing EATCHIP. EATCHIP provides the opportunity for European countries, initially in Western Europe, to work together towards developing a seamless, integrated air traffic management system. The APATSI programme parallels the developments in impro~ng ATC capacity by considering improvements in airport capacity. This interface is of vital importance, as improvements to ATC capacity will be of no consequence should there be inadequate capacity at airports to land and take off. The four-phase EATCHIP allows an evolving, seamless approach to improving ATC, but its last phase - the EATMS - is of particular interest as it is to be based on emerging technologies, and provide the extra capacity forecast by the turn of the century. The concept is based on the integration of the airborne and ground-based components supported by extensive automation - and allows aircraft to adhere accurately to 4D flight profiles. Importantly, it will change the future role of air traffic controllers, allowing them to concentrate on problem traffic, rather than on all traffic as at present, and solve problems quite some way before they develop into conflict situations. In conjunction with the development of the EATMS, the use of satellites is seen by many as a cure for all of Europe’s air traffic ills. Satellites do have a place in the ATC systems of tomorrow, though integrity, availability and institutional problems need to be overcome before they are the sole ATC system, replacing land-based AT%. In the meantime, satellites can complement land-based

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systems, providing a back-up where necessary. As the USA moves towards satellite-based ATC, and with ICAO’s FANS programme also advocating satellites, Europe may well move towards a primarily satellite-based ATC early in the next century: another recommendation by the EU Wise Men.

References Anon (1992) ‘Faster airports’ Flight Intematibnal (15-21 July) 31-33 Anon (1993a) ‘Heavens! Deregulation works’ The Economist (6-13 November) 114 Anon (1993b) ‘Aerospace Survey’ (8 June) Anon (1993~) ‘Wise Men review “old airhne structures” Flight International (17-23 November) 17 Anon (1993d) ‘ATC in Europe’ DATA Review (February) S-8 Anon (1993e) ‘Tangled - a survey of the airline industry’ (12-19 June) 18 Anon (1993f) ‘Controlling the skies’ FZight International (4-10 August) 28-30 Anon (1993g) ‘The 21st century ATC confidence game’ IATA Review (February) 11-16 Anon (1994a) ‘Eurocontrol ATC technology “lags behind” Flight international (7-13 September) 24 Anon (1994b) ‘European dilemma’ Fright International (9-U February) 30-31 Anon (1994~) ‘Fast moves’ Flight Znfernationaf (2-8 March) 41 Anon (1994d) ‘Europe plays catchup satellite navigation’ Znteravia (July) 24-26 ATAG (1992) European Traffic Forecasts ATAG, Geneva Council of Ministers (1989) Air Traffic System Capacity Problems COM (88) 177 Final, Commission of the European Communities, Brussels Cox, M E, Rawlings, R C and van der Kraan, P (1992) ‘GPS: can it contribute to European ATC?’ Journal of Navigation 45 (2) 205-216 Duytschaever, D (1993) ‘The development and implementation of the Eurocontrol Central Air Traffic Management Unit’ Journal of Navigation 46 (3) 343-352 ECAC (1990) ECAC Strategy for the 1990s ECAC, Paris Eurocontrol (1987) Future ATS System Concept Description Eurocontrol, Brussels Eurocontrol (1989) Central Flow Management Unit lmp~ementation Plan Eurocontrol, Brussefs Eurocontrol (1991) European Air Traffic Control Harmonization and Integration Programme (EATCHIP]. Repoti Phase I Eurocontrol, Brussels Hume, C (1990) ‘The airlines’ perception of the ATFM problem’ Journal of Navigation 44 (2) 204-208 Lange, D G F (1989) The Crisis of European Air Traffic Control: Costs and Solutions Wilmer, Cutler & Pickering, London/ Brussels/Washington DC Marten, D (1993) ‘European ATC harmonization and integration programme’ Journal of Navigation 46 (3) 326-335 Moss, D (1992) ‘The ECAC Outlook’, IATA Review (May) lo-14 Wheatcroft, S and Lipman, G (1990) European Liberafization and World Air Trakport - Towar& a Tr~~~tionai indite The Economist Intellinence Unit and Business Intemational. London ”

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