Provision of Air Traffic Surveillance Services
The Provision of Air Traffic Surveillance Services domain tests Annex 10 Volume IV and PANS-ATM Chapter 8: how aircraft are identified, separated and monitored using primary radar, secondary surveillance radar (Modes A/C/S), ADS-B and multilateration.
Identification and monitoring
An aircraft is identified by direct recognition of its PSR return, by transfer of identity, by a discrete squawk with IDENT, by a position report over a fix that coincides with the label position (Mode C consistent within 300 ft of the reported level), or by a turn of 30 degrees or more. Controllers must check Mode C against a known elevation before relying on level information, and must tell the aircraft when its Mode C is wrong.
Separation
Surveillance separation is 5 NM between identified aircraft; 3 NM applies only inside designated terminal areas where the system, the display and the unit's approval support it. Separation must be established by at least one controller and remain continuously visible, with an adequate display update rate. Vectors and speed control are the tools used to build and hold the minimum.
Worked example
Two aircraft on converging tracks are 12 NM apart, closing at 420 kt. Reasoning: 420 kt is 7 NM per minute, so the 7 NM margin above the 5 NM minimum is consumed in one minute. That leaves no room for negotiation, so the controller turns one aircraft immediately and tells the pilot why.
Traps that cost marks
Applying 3 NM outside the designated terminal area; assuming 5 NM while an aircraft crosses a known coverage gap or a Mode S blind spot; issuing 'radar contact' to an aircraft that has only been transferred, not identified; using level-based separation without verifying Mode C; confusing surveillance separation with longitudinal time separation.