Dependent Parallel Approaches

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Parallel Approaches (Source: FAA AIM)

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Diagonal Separation (Source: FAA AIM)

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Simultaneous (Parallel) Independent Approaches (Source: FAA AIM)

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Simultaneous Close Parallel PRM Approach (Source: FAA AIM)

Dependent parallel approaches are instrument procedure operations used at airports with multiple parallel runways. These procedures allow air traffic controllers to sequence arriving aircraft on adjacent runways simultaneously—but unlike independent parallel approaches, strict longitudinal and diagonal separation standards must be maintained.

Key Characteristics

• Operational Dependency Aircraft are not separated independently but instead require controlled spacing in terms of both time and distance to ensure safety. A minimum of 1.0 NM diagonal spacing is typically required, although this can vary based on airport layout, runway orientation, and aircraft category.

• Controller Monitoring Air traffic controllers are actively involved in ensuring spacing is maintained throughout the final approach, especially from the final approach fix (FAF) to the runway threshold.

• Visual and Instrument Support: These operations often rely on high-fidelity radar systems, PAPI (Precision Approach Path Indicators), and other navigational aids to facilitate accurate tracking and timely intervention.

Implementation Context

• High-Volume Airports Frequently used at capacity-heavy airports like ATL (Atlanta), DFW (Dallas/Fort Worth), and ORD (Chicago O'Hare), especially when demand for simultaneous arrivals is high.

• Peak Period Utility Particularly beneficial during rush hours, weather disruptions, or runway maintenance, when maintaining throughput without sacrificing safety is crucial.

• Benefits vs. Independent Approaches While independent parallel approaches permit aircraft to land without coordination across runways, dependent operations allow increased efficiency while using fewer navigational resources. However, they demand precise spacing compliance, making controller skill and pilot awareness essential.

Why It Matters to Safety

• Separation Assurance Aids in maintaining collision-free approach paths.

• Efficiency Optimization Increases arrival rate without exceeding workload thresholds for ATC.

• Conflict Avoidance Reduces the potential for runway incursions or missed approaches due to unexpected aircraft convergence.

Source Reference – SKYbrary