PRECISION AIR traffic control (ATC) approach-monitoring equipment has become fully operational at London's Heathrow and Gatwick airports, says the UK Civil Aviation Authority.

Known as the approach-monitoring aid (AMA), the system - the first of its kind - alerts the tower controllers to aircraft deviations from a normal approach path, enabling them to warn the pilots.

At both airports, the equipment uses the existing surface-movement radar's (SMR) sensor, tracking and labeling system, and the AMA picture is shown below the SMR display on the towers' Norcontrol screens. If an aircraft leaves a predetermined, fan-shaped tracking zone based on the extended centreline of the runway-in-use and with its apex at the threshold, the AMA generates an alert. This takes the form of an aural alert and a visual-warning bar on the screen. The latter details the aircraft's call sign, the destination runway and a plot of the last eight radar returns.

The AMA idea sprang from incidents at Gatwick, which has close parallel runways (not used simultaneously), where, in the past, pilots have become confused about which runway they were supposed to land on, according to the CAA. In two cases, aircraft have landed on a parallel taxiway at night. Had an AMA been available, the controller would have been alerted in time, either to advise the pilots or to order them to abandon the approach.

The system has been on trial at London Gatwick since the middle of 1994.

Source: Flight International