UK air navigation service provider (ANSP) NATS hopes to provide the UK general aviation community with an incentive to fit Mode S transponders, so they can be seen and identified on secondary radar even if they are not in controlled airspace or in contact with air traffic control.
The incentive is that airspace that is uncontrolled, but in line for recategorisation for instrument flight rules traffic, would only remain open to visual flight rules flights that are Mode S-equipped.
Mode S transponders not only make equipped aircraft identifiable on secondary radar, they also trigger airborne collision avoidance system (ACAS) resolution advisories in commercial transport aircraft.
NATS and the UK Civil Aviation Authority say they are seriously concerned about near-collisions involving commercial air transport aircraft and military or GA types in areas where airliners have to transit uncontrolled airspace to approach or depart from several provincial airports. As a consequence, the CAA could close uncontrolled airspace to VFR operations. NATS says Mode S-equipped GA aircraft would not be obliged to call ATC, but if they were on frequency they could be provided with advisories and traffic information.
Source: Flight International
