Enhanced Mode S

Mode S Enhanced Surveillance consists of the extraction of downlink aircraft parameters (DAPs) for use in ground-based air traffic management systems. These parameters include: magnetic heading, airspeed (indicated air speed and Mach number), selected altitude, vertical rate, track-angle rate, roll angle, ground speed and true-track angle.

Mode S Enhanced Surveillance is the first stage in making use of air-derived data (ADD) in the form of downlink aircraft parameters, either directly to the controller or to air traffic management systems.

This technology improves situation awareness and reduces radio/telephony congestion, thus enhancing safety and also capacity. It also helps to reduce the amount of potential level busts and/or supports their earlier detection.

Air traffic controllers at MUAC see on their screens the down-linked selected altitude, magnetic heading, indicated air speed and Mach number from any equipped flight. An automated warning tool alerts controllers to any mismatch between the down-linked selected altitude and the official ground-based cleared flight level, as instructed by air traffic control.

Mode S parameters have proved to be a very popular system feature for MUAC controllers. The number of level busts has roughly halved, despite the fact that not all aircraft are equipped to downlink EHS parameters at present. In addition, by reducing the frequency load, controllers have more “thinking” time – something which is very welcome in one of Europe’s densest and busiest airspaces.