Earlier papers, based on a computer model of European air traffic, deal with the probability of conflicts arising between pairs of aircraft operating under free-flight rules. This paper discusses the problems of resolving these conflicts. When a potential collision takes place in the neighbourhood of other intruding aircraft, these must be taken into account when choosing an escape manoeuvre. A suggestion is made that may ease the problem.

In an earlier study, the author attempted to give some quantitative estimates of the problems that free flow might face in Europe. The study was based on a traffic sample from the Eurocontrol Route Charges Office for a busy day in 1991. More recently, they generously made available a similar sample for a day in 1997. Using this new data, the study has been extended to cover wider aspects of the free flow problem. The central problem is that of ensuring safety. This will require a mechanism to detect collision threats and safely to resolve the problems. Possible tools are ground-based surveillance and/or airborne systems. This paper will use computer modelling to predict the loads that these detection and resolution systems must face.

The achievement of the goals of the International Civil Aviation Organization (ICAO) Future Air Navigation System (FANS) is essential for the continued development of the airline industry. A recently completed movement study for the North Atlantic Track area forecast that the previously anticipated aircraft movements for 2010 would now be achieved by 1999. Peak time capacity growth for the region is now reliant on the introduction of Reduced Vertical Separation Minima (RVSM) scheduled for January 1997. Similarly, Europe had an all-too-evident capacity problem though some alleviation should follow from the introduction of precision area navigation (PRNAV) routeings in early 1998. However, despite the introduction of these developments, the restrictions on flow rates imposed by capacity variations in adjacent areas will remain. Quite obviously, an enhanced and fully capable Air Traffic Management (ATM) environment is required to solve many of the problems that commonly exist today. Nevertheless, more could be achieved through the application and exploitation of advanced navigation equipment such as the aircraft Flight Management Computer System (FMS) that is in widespread use today – a theme that will be returned to later in the paper.

A realistic runway capacity study for two major airports, namely Frankfurt (EDDF) and Chicago O'Hare (ORD) is presented, assessing the effect of optimal scheduling on the runway capacity and air traffic delays. The maximum position shift (MPS) runway scheduling algorithm, used in the study, was developed by Trivizas at the Massachusetts Institute of Technology (1987).

EDDF is studied in the context of 160 major European airports, with a real traffic sample from 6 July, 1990. ORD is studied in the context of 26 major US airports using a large traffic sample from 1 March, 1989. Secondary airport traffic has been assigned to the geographically nearest major hub and time compression has been used to extrapolate to an artificially denser scenario.

The results show that optimal scheduling can bring about capacity improvements of the order of 20 percent, which in turn reduce delays up to 70 percent. These results are the product of a dynamic traffic management process which has been visually validated by observing animated runway operations and monitor functions.

The study has been conducted with TMSIM, a comprehensive, object-oriented simulation tool that allows one to build an understanding of the structure and functionality of the air traffic control system, by modelling its components, their functionality and interactions, and measuring component and system performance. It features interactive route network editing (using menu/mouse techniques), complete route and airport structure modelling, independent flight and ATC objects, 3-D animation, advanced algorithms for scheduling, routeing, flow management, airspace restructuring (sectorization) and performance (capacity and communications workload) analysis.

Europe is moving towards a more closely integrated air traffic management system through the European ATC Harmonization and Integration Programme (EATCHIP). This paper explains the need for such an approach and how it was brought about by capacity limitations in the current European air traffic system. It describes the key strategy of progressive harmonization and integration by the various States, examines the roles of the European Civil Aviation Conference (ECAC), the International Civil Aviation Organization (ICAO), EUROCONTROL and the European Commission in the management of the Air Traffic Management (ATM) development programmes. It also reviews the longer-term planning of a future system with an enhanced relationship between the air and the ground, and addresses the navigation aspects of ATM systems.

Civil aviation authorities have a requirement for the application of devices which are capable of determining the geometric height of aircraft above flight level 290 with a high degree of precision. These devices, called height monitoring units (HMUS), should pave the way for a safe and expeditious introduction of reduced vertical separation of 1000 ft above flight level 290.

In this paper the design philosophy as well as the prototype development of such a device, which is called the dual-synchronized autonomous monitoring system (DAMS), are outlined. This device operates fully independently of any airborne equipment such as secondary surveillance radar transponders.

The configuration basically consists of two standard marine radars with both axes of revolution situated in a horizontal plane. With this configuration it is possible to determine the trajectory of an aircraft and, in particular, the geometrical height above ground level within typical radar slant range coverage of some 18 km. The basic application of this equipment will be in the field of height monitoring of aircraft targets in environments with reduced vertical separation standards of 1000 ft above flight level 290, but a wider application of this concept is foreseen for local precision tracking of aircraft targets.

For the travelling public in the late eighties and early nineties, the most disturbing characteristic of air travel must be delays. In Europe, this is certainly the case. These delays not only cause much inconvenience to the air travellers but also generate high costs for the aircraft operators. To a large extent, these delays are due to an imbalance between the air traffic demand and the capacity of the present Air Traffic Control (ATC) system in Europe.

Since the advent of large-scale commercial aviation in the mid 1940s, a system of routes has been developed between airports serving the major conurbations of the world. To prevent collision between aircraft using these routes and off-route traffic, protection is provided to the routes and to the vicinity of airports by means of controlled airspace, airways (AWYS), control areas (CTAS) and control zones (CTRS). Zones commence at ground level and the base an area is at a defined altitude. Inside this controlled airspace certain rules apply which are more stringent than those applied outside, and all movements are subject to Air Traffic Control (ATC).

This is the concluding part of a series of three papers for this Journal, documenting the European studies into the feasibility of 1000 ft vertical separation minima above FL290. This paper outlines the results from European data collections other than the main precision radar data collection and expands upon the factors affecting height-keeping performance. The development of a Minimum Altimetry System Performance Specification (MASPS), necessary for a reduced vertical separation minimum above FL29O, is presented. A number of implementation issues, in particular monitoring, are also discussed.

The contents of this paper reflect the views of the authors; they do not necessarily reflect the official views or policy of the NLR, CAA or EUROCONTROL.

This paper commences by outlining the developments expected in en-route navigation capabilities in Western Europe and describes the current provision of surveillance employing monopulse SSRS. Following a brief review of GPS characteristics, it then considers the use of ADS, in conjunction with GPS, as an alternative and/or supplement to these ground-based systems. In the light of a simple cost comparison, it suggests that the space-based system could be very advantageous, particularly where new routes are to be established in areas with little or no ATS infrastructure. A final section discusses the possibility of using GPS for height-monitoring purposes as will be necessary when a reduced vertical separation minimum of iooo ft, is employed above FL290 in Europe, and elsewhere.

Improved radar surveillance for air traffic control can be obtained by the integration of radar systems. Integration, however, might cause the delay of radar information, which would hamper the air traffic controllers in their work. To estimate the delay, a mathematical equation to assess the amount of radar information causing this delay has been deduced from the properties of the behaviour of air traffic. The mathematical equation has been tested using results obtained from operational secondary surveillance radar in the Netherlands.

In a strong wind, groundspeed may vary appreciably during a turn, as, for example, in the case of a landing after a U-turn preceding the localizer intercept. Such conditions are critical for maximum use of the runway, and render human estimation of aircraft motion extremely difficult.

This paper summarizes the tests conducted using a ground-based 4D-guidance program, developed to assist the air traffic controller in maintaining the predicted landing-time sequence with an accuracy better than 10 seconds for each arrival.