The lost track tool is an important feature for air traffic controllers. It alerts them when a monitored aircraft, tracked by the surveillance data processing system, is no longer visible. Most modern Automated Air Traffic Systems (ATS) have a coasting function. This function allows the display of an aircraft’s position to continue for a short period, even without new surveillance data. Typically, this lasts for three missed updates, which can be about 15 to 30 seconds. If new data isn’t received after this time, the lost track tool is activated.
On the situation display, the appearance of the lost track tool can vary depending on the system in use. However, it usually shows at least the aircraft’s call sign and the coordinates of its last known position. Additional details might include the time of the track loss, the last observed altitude, and the SSR code. The information can be represented with a special symbol on the screen where radar contact was lost or shown in a table format.
To illustrate, the first image typically displays a correlated track in white, showing details like the call sign (BDD0606), current level (FL 360), and ground speed (455 knots). The second image represents the track in coasting mode, indicating that no new plot was found. An X symbol alerts the controller that the position is not derived from surveillance sensors and suggests that the track might disappear soon. Generally, the coasting symbol appears up to three times. If a fourth missed plot occurs, a lost track position indicator, marked by a red symbol and label, visually conveys the position and the latest available data. The lost track window provides more information, including the coordinates of the loss and the transponder code (1234).
Several reasons may trigger the activation of the lost track tool: an aircraft leaving the coverage area of surveillance sensors, low-flying aircraft being obscured by terrain, or aircraft landing, especially off-airport in cases like forced landings or ditching. It’s important to note that if an aircraft lands at an aerodrome, even in emergencies, the ATS system usually recognizes this as a landing and doesn’t trigger an alert for lost track.
Other scenarios for lost track activation include a lack of transponder signals combined with missing primary surveillance. This can result from various issues, such as malfunctions, accidental standby mode selections, or electrical failures. Additionally, there could be collisions either with other aircraft or terrain.
The lost track tool offers several benefits. It clearly indicates to controllers when an abnormal situation arises, allowing for quick investigations. This tool also helps direct search and rescue teams more effectively. To minimize unnecessary alerts, the lost track tool is only activated for correlated tracks, and certain filter conditions may apply. For instance, alerts may be suppressed if the track was lost far outside the ATS unit’s area of responsibility.
