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7.3 Sequencing Methods

7.3.1 General

Sequencing methods are used by the Approach Controller to establish and maintain spacing between aircraft.

The Approach Controller shall select the most appropriate method based on traffic density, aircraft performance, and operational requirements.

7.3.2 Distance-Based Sequencing

Distance-based sequencing is achieved by maintaining lateral spacing between aircraft.

The Approach Controller shall:

  • Maintain radar separation (typically 3–5 NM as applicable)
  • Monitor spacing continuously
  • Adjust spacing using speed control or vectoring

Distance-based sequencing is the primary method in most operations.

7.3.3 Time-Based Sequencing

Time-based sequencing is achieved by maintaining consistent time intervals between aircraft.

The Approach Controller shall:

  • Use speed control to regulate spacing
  • Maintain consistent groundspeed where possible
  • Apply this method in high-density or structured operations

Time-based sequencing requires stable and predictable aircraft performance.

7.3.4 Vector-Based Sequencing

Vector-based sequencing is achieved by adjusting aircraft track to create or reduce spacing.

The Approach Controller shall:

  • Use headings to position aircraft within the sequence
  • Extend or shorten downwind as required
  • Apply vectoring early to avoid late corrections

Vectoring shall be used to support sequencing, not replace proper planning.

7.3.5 Method Selection

The Approach Controller shall:

  • Use the simplest method appropriate to the situation
  • Prefer speed control where possible
  • Use vectoring when spacing cannot be achieved by speed alone

Selection shall consider workload, traffic complexity, and efficiency.

7.3.6 Limitations

The Approach Controller shall not:

  • Rely on a single method where ineffective
  • Apply late or reactive sequencing
  • Overuse vectoring resulting in excessive manoeuvring
  • Allow spacing to compress on final approach

7.3.7 Key Principle

Effective sequencing uses the simplest and most efficient method.

The Approach Controller shall:

  • Plan ahead
  • Select the appropriate method
  • Maintain spacing continuously

Good sequencing minimises intervention and maintains stable traffic flow.