Description

This article aims to provide an overview of what the controller is responsible for and what the general boundaries of their duties are. Details on these matters can be obtained from local instructions (e.g. Manuals of air traffic services).

Normal operations

The controller is responsible for:

• provision of separation, taking account of the airspace class, flight rules and other factors (e.g. RVSM, formation flights, special provisions for certain flights, etc.). 
• collision prevention between aircraft and obstacles on the manoeuvring area
• passing and acknowledging information, including coordination with other controllers and careful hearback of the pilots' readbacks
• ensuring the clearances and instructions are complied with by monitoring aircraft behaviour and issuing corrective instructions (or in case of aparently deliberate non-compliance, informing the appropriate authorities)

The controller is not responsible for:

• aerodrome/runway closure in case of e.g. poor braking action, snow, rain, thunderstorm, etc. They will inform the pilots about the current conditions but the decision whether to attempt a landing or to divert is up to the aircraft commander. Aerodromes may be closed e.g. for snow clearing, due to runway flooding, etc. but this decision is not made by the controller. They will, however, convey the message to the aircraft concerned.
• the decision for aircraft diversion and the aerodrome to divert to. The controller will provide the best and most recent information available but it is up to the pilot to choose an appropriate course of action.
• collision avoidance in case an aircraft is following an ACAS RA. However, the controller may be held responsible for the loss of separation that often (but not always) precedes the ACAS RA.
• terrain and obstacle clearance, except when:
  • the flight is flying in accordance with IFR and
  • the flight is being vectored or cleared to fly on a direct route

Nevertheless, the controller will warn other aircraft (e.g. VFR flights) in case of an MSAW alert and advise them to check their altimeter setting.

Emergency and abnormal situations

In case of an emergency or abnormal situation the main responsibilities of air traffic controllers (in addition to performing their regular duties) are:

• provision of approrpriate information to affected aircraft, e.g.:
  • weather information for the chosen aerodrome (e.g. METAR, actual weather, etc.)
  • aeronautical information (e.g. runways, radio aids, etc.)
  • aircraft in proximity to the one in distress (e.g. in case of fuel dumping or emergency descent)
• provision of navigation assistance (e.g. headings) on pilot's request
• provision of appropriate information to the affected ATS units and other agencies (e.g. rescue coordination centres, aerodrome RFFS, etc.)
• servicing aircraft that has declared an emergency with a high priority, e.g.:
  • changing the path of other aircraft in case of a potential conflict
  • accomodating crew requests (for levels, headings, etc.)
  • (temporary) suspension of operations (takeoffs and landings) in case of an emergency landing. This may include instructing an aircraft on final to go around or an aircraft on the apron to postpone their start-up.

The controller is not responsible for:

• the choice of an aerodrome. They will, however, provide options to the pilot to choose from.
• the declaration of an emergency or urgency situation. They may, however, ask the pilot for confirmation and forward the information to other controllers and agencies. In addition, they may treat an aircraft as being in a state of an emergency based on local procedures.
• the choice whether to continue the flight or to divert. They will, however, support the crew by e.g. providing priority and information in either case.
• the conduct of search and rescue (SAR) operations. They will, however:
  • advise the rescue coordination centres about aircraft in distress and provide other appropriate information (e.g. flight details, last known position, etc.)
  • provide priority to SAR flights

Related Articles

• How Air Traffic Control Works
• Executive and Planner Controller
• Coordination in ATC
• Air Traffic Service (ATS)
• Air Traffic Control Service

Further Reading

• ICAO Doc 4444 PANS-ATM
• UK CAA CAP493 Manual of Air Traffic Services Part 1
• US FAA JO 7110.65 Air Traffic Control