Knowledge of the statistics of aircraft vertical speeds is important both for the construction of realistic traffic simulators and for the development of trajectory prediction tools for use in future air traffic control (ATC) systems. This paper reports on the analysis of radar data recordings for nearly 10000 civil flights on airways. Results are presented for the means and spreads of vertical speeds as functions of altitude. Evidence is presented that roughly half of the observed spreads arise from fluctuations within each aircraft's trajectory, as opposed to variation from one aircraft to another. A simple procedure is proposed for simulating vertical speed data which has statistics similar to those obtained from the radar recordings. Some consequences of the results for the development of trajectory prediction tools for use in future ATC systems are discussed. The results suggest that the provision of accurate trajectory prediction tools is not as straightforward as it might at first appear to be.

A new threat detection criterion is described which provides a better match to the requirements than the well-known modified tau criterion for a civil air transport collision avoidance system. Experimental evidence is given to show that it also reduces the number of undesirable alerts.

The views expressed in this paper are those of the author and do not necessarily represent CAA policy.

The author would like to give grateful acknowledgement to the various companies from which information has been received. (Note that the original presentation at a RIN ordinary meeting was illustrated by numerous colour slides which cannot be reproduced here, as well as three video films).

The Federal Aviation Administration (FAA) is conducting experimental programmes to support introduction of satellite navigation and communications services into the air traffic control system during the 1990 time period. This work programme is closely related to the activities that have been conducted by the ICAO Future Air Navigation Systems (FANS) Committee and will result in development of standards for avionics systems and services for the Global Positioning System (GPS), as well as digital voice and digital data link services. This paper summarizes the FAA programmes supporting the introduction of the new satellite services.