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4. Separation Minima

4.1 Radar Separation

Radar separation is the primary method used within the Muscat FIR to ensure safe distances between aircraft under surveillance. Controllers use radar to maintain the following types of separation:

4.1.1 Lateral Separation

Unless otherwise specified, all aircraft operating within the Muscat FIR under radar control shall maintain a minimum horizontal radar separation of 5 nautical miles (NM) between each other.

4.1.2 Vertical Separation

If horizontal separation is not feasible, vertical separation shall be used. Vertical separation of 1,000 feet shall apply up to and including FL410 within RVSM airspace. Above FL410, a vertical separation of 2,000 feet is required unless both aircraft are RVSM-approved.

4.1.3 Longitudinal Separation (time/distance-based)

Aircraft operating enroute on the same airway and at the same flight level shall be separated by a minimum longitudinal distance of 20 nautical miles. This minimum may be reduced to 10 nautical miles if the leading aircraft is traveling at a speed at least 20 knots greater than that of the trailing aircraft. Additionally, when aircraft are expected to pass through the level of another on the same airway during climbing or descending flight, while one aircraft maintains the same level, a minimum separation of 10 nautical miles shall be maintained.

4.2 Procedural Separation

For aircraft operating in the enroute phase and approaching the limits of radar coverage from the Muscat FIR, the following longitudinal separation minima shall apply. A standard separation of 80 nautical miles or 10 minutes shall be maintained between aircraft. This separation may be reduced to 40 nautical miles or 5 minutes, provided the leading aircraft is at least 20 knots faster than the trailing aircraft. Further reduction to 25 nautical miles or 3 minutes is permitted if the leading aircraft is at least 40 knots faster than the trailing aircraft.

4.3 Wake Turbulence Separation

Wake turbulence separation is applied to mitigate the risk posed by vortices generated by heavier aircraft, which can affect the safety of following aircraft. Although wake turbulence is most critical during takeoff and landing phases, en-route separation minima are also established to ensure safe spacing where applicable.

The following wake turbulence separation minima apply in en-route airspace between aircraft of differing weight categories:

  • Heavy behind Heavy: No additional separation required beyond standard lateral, vertical, or longitudinal minima.
  • Medium behind Heavy: Minimum 4 NM lateral or longitudinal separation.
  • Light behind Heavy: Minimum 6 NM lateral or longitudinal separation.
  • Light behind Medium: Minimum 5 NM lateral or longitudinal separation.

Controllers must apply these minima when vectoring or sequencing aircraft with differing wake turbulence categories in en-route sectors, especially when aircraft are operating on converging or same tracks. If the required wake turbulence separation cannot be assured by lateral or vertical means, longitudinal spacing must be increased accordingly.

4.4 Separation in Mixed Surveillence/Procedural Areas

In portions of the Muscat FIR where radar surveillance coverage is partial or intermittent, air traffic controllers must apply a combination of radar and procedural separation methods to maintain safe aircraft spacing.

  • Radar surveillance areas: Controllers apply standard radar separation minima, continuously monitoring aircraft positions via radar displays and updating flight data accordingly.
  • Procedural areas: Where radar coverage is unavailable or unreliable, controllers revert to procedural separation, relying on position reports, estimated times over waypoints, and published procedural separation standards (e.g., time or distance-based minima).
  • Transitions between areas: Controllers must carefully coordinate the handover of aircraft between radar and procedural control zones. This includes verifying position reports, confirming clearances, and ensuring that appropriate separation standards are maintained without gaps.
  • Controllers must remain vigilant during these transitions to prevent loss of situational awareness and to mitigate the increased workload associated with mixed-mode separation.
  • Communication with adjacent sectors and pilots is essential to maintain seamless traffic flow and uphold safety standards in mixed surveillance/procedural environments.

4.5 Exceptions and Reduced Separation

Any exceptions to standard separation minima, including reduced separation, must be authorized only under strict conditions such as contingency operations or specific operational agreements. Controllers must ensure that risk assessments are conducted and that all involved parties are informed.