Air Traffic Management: General Provisions and ATS Services
The three services and their objectives
Air traffic management is the umbrella; air traffic services are the operational core. Candidates must separate the three ATS components: air traffic control service (prevent collisions and maintain an orderly, expeditious flow), flight information service (advice useful for safe and efficient conduct, e.g. weather, aerodrome conditions, traffic not under control), and alerting service (notify SAR and assist aircraft in distress or overdue). A controller must know which service applies to which class of airspace and which flight rules.
Control vs information
A frequent trap: providing traffic information to a VFR flight does not create a clearance and does not relieve the pilot of responsibility; conversely, an IFR flight in controlled airspace requires a clearance. Another trap is the flight plan: an ATS flight plan is required for IFR and for most controlled VFR operations, and its content (aircraft identification, type, route, level, speed, destination, alternate, endurance, persons on board) must be understood, including how changes are transmitted (modification messages, DLA, CHG).
Flight rules interplay
Know when special VFR may be authorised, when an aircraft must be separated, and when only information is owed. The concept of essential traffic and essential local traffic appears in questions about who must be told what.
Rule of thumb
Before answering, ask: is this a clearance, an instruction, or information? Only a clearance/instruction creates an obligation; information transfers awareness, not responsibility.
Worked example
An IFR aircraft requests a level change in controlled airspace. The controller must coordinate and issue a clearance; simply telling the pilot "traffic at your level" is information and is not a substitute for the clearance.