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4.2 Sequencing Techniques

4.2.1 General

Sequencing techniques are used by the Tower Controller to establish and maintain safe spacing between aircraft.

Effective sequencing shall:

  • Prevent conflicts
  • Maintain safe separation
  • Reduce the likelihood of go-arounds
  • Support efficient runway utilisation

Sequencing shall be proactive and established as early as possible.

4.2.2 Objectives of Sequencing

The Tower Controller shall aim to:

  • Maintain safe separation between aircraft
  • Establish a stable and predictable landing sequence
  • Minimise the need for corrective action
  • Integrate different aircraft types and speeds

4.2.3 Establishing the Sequence

The landing sequence shall be determined at the earliest opportunity.

The Tower Controller shall:

  • Identify aircraft positions relative to the runway
  • Determine and plan landing order
  • Communicate sequence clearly to pilots
  • Monitor spacing continuously

Example Phraseology:

GFA123, number two, follow traffic on final.  
GFA456, number one, runway 27, cleared to land.

4.2.4 Extending Downwind

Extending downwind shall be used to increase spacing between aircraft.

The Tower Controller shall use this technique when:

  • Aircraft are too close on base or final
  • Additional spacing is required
  • Integrating faster aircraft behind slower aircraft

Instructions shall be issued early to avoid unstable approaches.

Example Phraseology:

GFA123, extend downwind, I will call base.

Extending downwind shall not be used if:

  • It would result in excessive track miles
  • It would create further sequencing complexity

4.2.5 Orbit Instructions

Orbit instructions may be used to delay an aircraft and create spacing.

The Tower Controller shall ensure that:

  • The instruction is safe and appropriate
  • The aircraft has sufficient altitude and airspace
  • The orbit will not create additional conflicts

Example Phraseology:

GFA123, orbit right, report established downwind.

Orbit instructions shall not be used when:

  • Aircraft are on short final
  • Terrain or airspace limitations make it unsafe
  • Pilot workload is high or conditions are unsuitable

4.2.6 Speed Considerations

The Tower Controller shall consider aircraft performance when sequencing traffic.

The controller shall:

  • Identify differences in aircraft speed
  • Increase spacing for faster-following aircraft
  • Avoid compressing spacing on final approach

Sequencing decisions shall account for wake turbulence and aircraft type.

4.2.7 Use of Go-Around

A go-around may be used as a sequencing tool of last resort.

The Tower Controller shall instruct a go-around when:

  • Safe spacing cannot be maintained
  • Runway occupancy is not assured
  • Sequencing has become unstable

Go-arounds shall be issued early to maintain safety and reduce disruption.

4.2.8 Key Principle

Sequencing shall be proactive and controlled.

The Tower Controller shall:

  • Plan ahead
  • Issue instructions early
  • Avoid reactive or last-minute corrections

If sequencing becomes unstable, the controller shall take immediate corrective action.

Use when:

  • Immediate spacing is required
  • Sequence needs correction
  • Traffic is too close

Example:

GFA123, orbit left.

4.2.5 Speed Control

Speed adjustments can assist with maintaining spacing.

The controller may:

  • Request pilots to reduce speed
  • Use spacing instructions in conjunction with sequencing
  • Note: Speed control is limited at Tower level and should be used cautiously.

4.2.6 Go-Around for Spacing

A go-around may be used as a last resort to maintain separation.

Use when:

  • Spacing cannot be maintained
  • Runway occupancy prevents landing
  • The approach becomes unsafe

Example: 

GFA123, go around, I say again go around. Acknowledge

4.2.7 Common Sequencing Errors

Common mistakes include:

  • Leaving sequencing too late
  • Overusing orbits instead of planning ahead
  • Not adjusting spacing early
  • Trying to “force” aircraft into unsafe gaps

4.2.8 Recovery Techniques

If sequencing becomes unstable, the controller should:

  • Issue a go-around
  • Re-establish the sequence
  • Increase spacing using downwind extension or orbits
  • Reduce traffic complexity if required
  • Reduce traffic to minimum speed

4.2.9 Key Principle

Good sequencing is achieved through early planning and small adjustments. Large corrections usually indicate that action was taken too late.