The Global Navigation Satellite System

Navigating into the New Millennium

Alessandra A.L. Andrade

• Publisher: Routledge
• Year: 2017
• ISBN:
  9781351888851
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Aviation
• Index: Technology & Engineering

The book constitutes a valuable guide to the implementation of the CNS/ATM system towards ensuring safe, efficient and orderly evolution of international air transport. It uses a pragmatic approach in addressing the major legal, institutional, technical, political and economic aspects underlying the Global Navigation Satellite System, which is expected to play a fundamental role in aviation safety and air navigation world-wide. The book also examines, through well-reasoned analysis and research, the various controversial and relevant issues which will dominate the system in the years to come. The author demonstrates a profound grasp of the subject-matter through a sustained absorption of technical, institutional and legal principles applying to this complex subject. This is brought to bear in the coherent structure and logical organisation of the chapters which makes the book an invaluable tool for the aviation community, scholars and national and international regulatory authorities. It will also be immensely useful for practitioners who work towards further development and implementation of the CNS/ATM system. There has been no comparable work previously published.

PART I

TECHNICAL ASPECTS

1 An Overview of the CNS/ATM Systems

Current Systems — A brief history

It has been said that if aviation pioneers¹ were to return today, “they would readily understand the aerodynamics and propulsion system of a Boeing 747, but they would be completely baffled by the aeroplane’s electronic control, navigation and communications equipment”.²

From a technical viewpoint, this assumption can be easily understood since the basics of aviation technology, at least as far as subsonic flight is concerned, were already well established by the time of the 1944 Chicago International Civil Aviation Conference, and jet engines were already in use in military aircraft.³

In the words of the Hon. L. Welch Pogue, former Chairman of the U.S. Civil Aeronautics Board and member of the U.S. Delegation to the Conference, at the close of the Second World War, “as a result of the intense competition for victory” which called for the utmost speed in military travel, significant technological improvements made it possible for aviation to “burst forth from an experimental, crawling promise into an impressive and soaring part of our civilisation”.⁴

In those early days, most aircraft were converted military aircraft and powered by piston engines. Although “flying boats” were still relatively common and suitable runways rather few, large four-engine aircraft types, such as the Lockheed Constellation or the Boeing Stratocruiser, dominated long-range flying. Mechanically complex and of questionable reliability, these engines rapidly yielded to the turbine engine, faster and smoother, of which the first to be introduced into commercial service in the 1950s was a turboprop engine, whose overall propulsive efficiency was improved by using its power to drive a propeller. Simpler though they might have been, they were rapidly overtaken by a not much later development, the jet-powered aircraft. At first considered too expensive to operate because of fuel consumption, and extremely noisy, the large, long-range jet aircraft, such as the Havilland Comet, the Boeing 707 and the Douglas DC-8, were soon followed by second-generation types, which entered service during the sixties. Examples of such aircraft are the Boeing 727 and the McDonnell Douglas DC-9. At the next step, there were the commercial supersonic aircraft, a remarkable technical achievement, two types of which were built, the Concorde and the Tupolev Tu-144, as well as the development of the turbofan engine, responsible for an increase in the propulsive efficiency of the jet engine, with a corresponding improvement in fuel consumption. Jumbo jets with larger engines followed, having been designed to cope with much greater passenger capacity, examples being the four-engined Boeing 747 and the three-engined Lockheed L-1011 and DC-10. The latest developments account for very economical, lighter, long-range aircraft with only two engines, such as the Boeing 757 and 767 and also the European Airbus models.⁵

Half a century of major technological progress and the increase in the volume of aviation activity have been accompanied over the years by a substantial development in the vital areas of communications and navigation as well as in its supporting infrastructure (facilities and equipment), namely runways, air traffic control, cockpit instrumentation,⁶ control systems, navaids, among others. Despite the continuous improvements, most have been considered inadequate to cope with future demand, as it remains to be seen.

The field of communication in aviation encompasses the operation of navigation aids on the ground, in the air and in space, consisting mainly of radars, landing aids, air to ground and ground to ground telecommunication equipment.⁷ Such navigation aids require an extensive use of the radio frequency spectrum, and that is the reason why they are also known as radionavigation aids. Safety of flight requires voice and data communication between the aircraft and air traffic control (ATC), in addition to the interchange of meteorological and flight alerting data, ATC instructions and search and rescue information.⁸

At the beginning, however, air-ground communication had to rely upon radiotelegraphy, since the use of voice communication would not become general practice until after the end of the World War II. Very high frequency (VHF) technology was later employed, but due to its inherent limitations to line of sight distance, high frequency (HF) transmissions, even though not as clear and reliable as VHF, were used in remote areas and over the oceans. Efforts to improve long-range VHF and HF communication were made over the years, by means of sophisticated antenna systems and single side-band transmissions. Yet, no other major development took place until communications satellites came into existence. Nowadays, wherever there is satellite coverage, voice communication is straightforward for all suitably equipped aircraft. Besides, the systems are able to handle large quantities of digital data for operational purposes.⁹

As regards ground-to-ground communications, connections between ground stations had to be initially undertaken by HF radio band despite its reliability limitations imposed partly by the variability of propagation characteristics. Comprehensive systems of ground links were eventually developed, including under-sea cable and voice communication, and were progressively refined and automated. The replacement of HF voice by satellite communication is considered to be a major step forward in the fixed telecommunications network.¹⁰

As for navigation, the present systems may be said to encompass three categories: i) very short-range, for approach and landing guidance; ii) short/medium range, for guidance over populated areas, where ground-aids can be provided; and iii) long-range, providing coverage over the oceans or continental areas where ground navigation aids are not available.¹¹

The primary approach and landing navigation aid today still is the instrument landing system (ILS), which functions by means of two separate radio beans, capable of defining the approach path in the horizontal and vertical planes, and is associated with three marker beacons, which indicate the distance from the runway. Because of distortions by surrounding areas and interference caused by the relatively narrow frequency band allocated for its use, the need arose for new systems to be designed and a transition plan was established by the ICAO Council in 1987. The implementation of the microwave landing system (MLS), as these other systems are called, has been threatened by the development of the satellite-based navigation systems¹² and its use limited to those locations where it is operationally required and economically beneficial.¹³

As for short/medium-range navigation, the earliest widely used aid was the non-directional beacon (NDB), used for marking points on airways. Other early aids, while providing area coverage, did not confine aircrafts to either fixed or to direct routes. Eventually, the need for channelling aircraft along airways for air traffic control reasons led to the adoption of a second World War point aid, the very high frequency omnidirectional radio range (VOR), as an international standard. But since VOR only provides the pilot with radial information, for the position of the aircraft to be fixed, it is also necessary to provide him with information on its distance from a fixed point, by means of the distance measuring equipment (DME).¹⁴

Navigational guidance over uninhabited areas and the high seas is generally provided by ground based long-range navigation systems, such as LORAN-C and OMEGA, or by self-contained aids, independent from ground sources, known as inertial navigation systems (INS). While both LORAN-C and OMEGA equipment may be stand-alone, most airborne systems are often duplicated, integrated with other systems and coupled to the autopilot. OMEGA’s accuracy depends on the quality of signal reception from the various stations, thus the need for it to be frequently cross-checked with other conventional aids. As for LORAN-C, once highly subject to local interference, it must be limited to areas of good ground wave signal reception. These systems were eventually supplanted by the use of the INS, which is entirely self-contained in the aircraft and operates by sensing the aircraft’s accelerations with a gyrostabilised platform. Such information is then integrated by computers to provide accurate position information and navigation data. The system will navigate the aircraft along a predetermined track with waypoint...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Table of Contents
• Dedication
• Foreword
• Preface
• List of Abbreviations
• Introduction
• PART I Technical Aspects
• PART II Institutional Aspects
• PART III Legal Aspects
• Conclusions
• Bibliography
• Index