In the near future, Spaced-Based Augmentation Systems (such as the Wide Area Augmentation System in North America) will become operational, permitting the use of GPS as a primary system for all phases of flight. Recently the International Civil Aviation Organisation (ICAO) has recommended the use of un-augmented GPS as a supplemental navigation system for all phases of flight including non-precision approaches. In this paper, the salient features of the Air Traffic Control (ATC) system in India, and the use of conventional navigational aids are described. A new landing procedure is proposed using un-augmented GPS known as ‘a non-precision instrument approach procedure with vertical guidance (IPV)’ for Hyderabad Airport, Runway 27. This procedure, if implemented, would be cost-effective and reliable for many airports in India. An algorithm has also been developed for determining the range and bearing between the departure and the arrival waypoints of an aircraft using the IPV.

This paper presents the application of GNSS1, or more precisely of Satellite Based Augmentation Systems (SBAS), to vertical separation for en-route, approach and landing operations. Potential improvements in terms of operational benefit and of safety are described for two main applications. First, vertical separation between en-route aircraft, which requires a system available across wide areas. SBAS (EGNOS, WAAS, and MSAS) are very well suited for this purpose before GNSS2 becomes available. And secondly, vertical separation from the ground during approach and landing, for which preliminary design principles of instrument approach procedures and safety issues are presented. Approach and landing phases are the subject of discussions within ICAO GNSS-P. En-route phases have been listed as GNSS-P future work and by RTCA for development of new equipments.

Projected requirements for automatic dependent surveillance (ADS) include the downlinking of certain aircraft flight parameters periodically and upon command from the ground. This will require a primary source of the data such as a flight management system (FMS) and, of course, a radio datalink. This paper provides a description of an existing system that could fulfil much of the interim airborne ADS equipment requirements by using GPS/OMEGA/INS/ACARS for existing aircraft which are not equipped with, or envisioned to be equipped with, SATCOM, FMS or IRS.

The collision avoidance of a pair of uniformly moving bodies is considered in three dimensions. The relative motion of the bodies yields an expression relating the time to closest approach, the minimum range, the current range and its rate of change, other variables being unobservable. A Boolean relation is then proposed that is satisfied whenever the minimum range and time to closest approach simultaneously fall below given thresholds. The relation is further studied, in particular with regard to the issue of false and premature alarms. An airborne collision avoidance system is a possible application.

The following two papers were presented at a joint Royal Aeronautical Society/Royal Institute of Navigation conference on ‘European Navigation into the 21st Century’ on Tuesday 12 February 1991.

The existing system of point-source radio navigation aids deployed throughout the European Region (e.g. VOR, DME, NDB), is inherently inflexible and suffers from a number of problems which degrade its efficiency; providing little scope for route capacity expansion. Area Navigation (RNAV) is seen to offer the answer to many of these deficiencies. Many aircraft are already fitted with RNAV – a system of navigation that allows track maintenance to defined levels of accuracy without the need to overfly point source aids. However, the full benefits of RNAV, including the introduction of more direct fuel efficient routes, arrivals and departures, and substantial increases in route capacities made possible by the application of reduced lateral and vertical separation criteria, cannot be fully realized until virtually all aircraft are equipped to a precision RNAV standard, and minimum aircraft systems performance specifications are introduced. This is unlikely to be practicable before 1998.

Timescales have been established for the progressive implementation of RNAV capability. High levels of cooperation between European states should ensure that operational implementation is achieved in a coordinated, efficient, orderly and safe manner. Certification and operational standards are being developed jointly and European guidance material, developed under the auspices of ICAO, is soon to be adopted by ICAO RGCSP for global application. Appropriate legislative amendments are being developed in the United Kingdom and elsewhere in Europe. All the present indications are that the implementation of RNAV in Europe will proceed successfully on an evolutionary basis, between now and the turn of the century.