Approach Control – Air Traffic Service for Arriving and Departing Aircraft

In-Depth Definition

Approach Control (sometimes called APP or, in the U.S., TRACON) is a specialized air traffic control unit responsible for the safe, orderly, and expeditious flow of air traffic in the vicinity of one or more airports. It manages aircraft during the critical approach (arrival) and departure phases, controlling flights typically within a radius of 20–60 nautical miles and up to 10,000–15,000 feet above ground, or as specified by local regulations.

Approach controllers take responsibility for sequencing arrivals, maintaining separation between aircraft, issuing headings, altitudes, and speeds, and coordinating handoffs to and from both en-route (area control) and aerodrome (tower) controllers. They use radar surveillance as their main tool, but can also operate procedurally in non-radar environments, relying on pilot reports and published procedures.

Approach control is essential for the safety and efficiency of terminal airspace, especially at busy or complex airports. It forms the critical bridge between the high-speed, high-altitude world of en-route flight and the precision required in the close-in airport environment.

Purpose and Objectives

The main objectives of approach control are:

• Prevent collisions: Maintain prescribed separation between all aircraft in the terminal airspace, whether arriving, departing, or transiting.
• Efficient traffic flow: Sequence inbound and outbound flights to maximize runway and airspace capacity and minimize delays.
• Timely information and alerting: Provide weather, NOTAMs, traffic advisories, and emergency coordination.
• Seamless coordination: Ensure smooth handoffs and information transfer between en-route and tower controllers.

By achieving these goals, approach control supports the safe, predictable, and efficient operation of airports and the overall air traffic management system.

Operational Workflow

Arrivals

1. Handoff from En-Route: As an aircraft approaches the terminal area, the en-route controller hands it over to approach control.
2. Sequencing and Vectoring: The approach controller sequences arrivals, assigns headings, altitudes, and speeds, and integrates aircraft onto published STARs or vectors as needed.
3. Approach Clearance: Once established on final approach (e.g., ILS, RNAV, or visual approach), the aircraft is cleared for approach.
4. Handoff to Tower: When the aircraft is on final, approach control instructs the pilot to contact the tower for landing clearance.

Departures

1. Handoff from Tower: After takeoff, the tower controller hands the aircraft to departure control (often a part of approach control).
2. Climb and Integration: Departure controllers issue headings and altitudes, ensuring departing flights remain separated from arrivals and other departures.
3. Transition to En-Route: Once clear of the terminal area, the aircraft is handed off to en-route (area) control.

Tools and Communication

• Radar surveillance: Real-time tracking of aircraft positions.
• Procedural methods: Used in non-radar areas; relies on pilot reports and published procedures.
• Standard phraseology: Ensures clear, consistent communication.
• Electronic flight data: Facilitates coordination and reduces errors.

Responsibilities of Approach and Departure Controllers

Approach Controllers:

• Sequence and space arriving aircraft.
• Issue vectors, altitudes, and speeds.
• Maintain minimum separation standards.
• Provide approach clearances.
• Handle missed approaches and emergencies.
• Coordinate with en-route and tower controllers.

Departure Controllers:

• Manage aircraft immediately after takeoff.
• Assign headings and altitudes to maintain safe separation.
• Integrate departures into the en-route structure.
• Coordinate handoffs to en-route control.

Both roles require keen situational awareness, technical proficiency, and the ability to make rapid decisions under pressure, following ICAO and national standards.

Airspace Structure and Sequence of Control

Terminal airspace is structured to ensure safety and efficiency:

1. En-route to Approach: Handoff at terminal area boundary or designated waypoint.
2. Approach to Tower: Handoff when established on final approach.
3. Tower to Departure: After takeoff, handoff to departure control.
4. Departure to En-route: Transition to cruise phase.

TRACONs in the U.S. may serve multiple airports and use advanced radar and automation tools. Airspace classes (B, C, D) define the level of service and separation standards.

Separation Minima: ICAO Standards and Practical Application

• Vertical Separation: 1,000 feet below FL290 (2,000 feet above, except 1,000 feet in RVSM airspace up to FL410).
• Horizontal Separation (Radar): 3–5 nautical miles in terminal airspace, depending on radar coverage and procedures.
• Non-Radar/Procedural Separation: Based on time and distance, with more conservative intervals.
• Wake Turbulence: Increased minima for aircraft following heavy or super aircraft.

Controllers constantly monitor and adapt separation based on traffic, weather, and operational conditions.

Approach Control Phraseology: ICAO Standards

Standardized phraseology reduces misunderstanding:

• Facility Identification: “Boston Approach,” “Dallas Departure.”
• Clearances: “Descend and maintain 3,000 feet,” “Turn right heading 270.”
• Approach Clearances: “Cleared ILS runway 27 approach.”
• Handoffs: “Contact Tower on 118.7.”
• STARs/SIDs: “Climb via SID to flight level 150.”

Strict adherence to phraseology is mandatory for safety.

Non-Radar (Procedural) Approach Control

In areas without radar, controllers:

• Use time and distance to separate aircraft.
• Rely on pilot position reports and published STARs/SIDs.
• Require frequent communication and careful planning.
• Apply more conservative separation, reducing capacity.

These skills are vital in remote, mountainous, or oceanic airspace.

Terminal Radar Approach Control (TRACON): U.S. Example

TRACONs manage approach/departure for one or more airports, using:

• High-resolution radar: Coverage up to 60 NM and 10,000–15,000 feet.
• Automated tools: Conflict detection, sequencing, flight data processing.
• Multiple sectors: For complex, high-density airspace.
• 3 NM radar separation: Standard in U.S. terminal areas.
• Collaboration: With en-route and tower facilities.

TRACONs are critical for handling busy metropolitan airspace safely and efficiently.

Example Procedures and Communications

Sample Radio Communications

• Arrival:
  Pilot: “Boston Approach, Delta 456, descending via the ROBUC 3 arrival, passing 12,000 feet.”
  Controller: “Delta 456, Boston Approach, descend and maintain 6,000 feet, expect ILS runway 27 approach.”

• Departure:
  Pilot: “Atlanta Departure, United 789, climbing through 4,000 for 10,000.”
  Controller: “United 789, radar contact, climb and maintain 12,000, turn right heading 090.”

• Handoff:
  Controller: “American 2123, contact Tower on 119.1.”
  Pilot: “Switching to Tower, American 2123.”

• Non-Radar:
  Controller: “Cessna 123AB, report passing waypoint GABRE.”
  Pilot: “Will report GABRE, Cessna 123AB.”

Common Scenarios

• Missed Approach: Controller vectors aircraft for another approach or sequence as needed.
• Weather Deviations: Vectoring around storms or turbulence, with coordination between ATC units.
• Emergencies: Immediate vectors and priority handling for distressed aircraft.

Importance within Air Traffic Services (ATS)

Approach control is a vital component of ATS, linking en-route and aerodrome operations, and ensuring safe, efficient transitions for every flight. The existence of approach control greatly enhances runway and airspace utilization, minimizes delays, and provides a safety net for handling emergencies and unusual situations.

Conclusion

Approach control stands at the heart of modern air traffic management, orchestrating the complex dance of arrivals and departures with precision and professionalism. Its blend of advanced technology, standardized procedures, and human expertise ensures that the world’s busiest skies remain safe, efficient, and predictable.

Approach controllers, whether using radar or procedural methods, are indispensable guardians of the terminal airspace, keeping the flow of global aviation running smoothly.