Parallel Instrument Runway Operations: Independent, Dependent, and Segregated Modes

010-06-07Pablo Asensio Martínez2026-03-271 min

Simultaneous operations on parallel instrument runways require specific procedures and separation.

Modes of Operation

  1. Mode 1 - Independent Parallel Approaches:
    • Simultaneous approaches to parallel runways where radar separation minima are not prescribed between aircraft on adjacent centerlines.
    • Requires a No Transgression Zone (NTZ).
  2. Mode 2 - Dependent Parallel Approaches:
    • Simultaneous approaches where radar separation minima are prescribed (diagonal) between aircraft on adjacent runways.
    • Requires procedures like divergent missed approach turns (30°).
  3. Mode 3 - Independent Parallel Departures:
    • Simultaneous departures in the same direction.
    • Runway centerlines must be separated by a minimum (e.g., 760 m).
    • Departure tracks must diverge immediately after takeoff (minimum 15°).
  4. Mode 4 - Segregated Operations:
    • One runway is used exclusively for approaches and the other for departures.
  • Mixed Operations: Approaches and departures mixed on both runways.
  • Semi-mixed Operations: One runway exclusive (departures or arrivals) and the other mixed.

Technical Requirements

No Transgression Zone (NTZ)

  • Airspace corridor at least 610 m (2000 ft) wide.
  • Located centrally between the extended runway centerlines.
  • Fundamental in independent approaches.
  • If an aircraft penetrates the NTZ, the controller must intervene immediately to maneuver any threatened aircraft on the adjacent approach.

Localizer Interception (ILS/MLS)

In independent parallel approaches:

  • Interception angle: Maximum 30°.
  • Straight and level flight prior to interception: At least 2 km (1.0 NM).
  • Established on the localizer: At least 3.7 km (2.0 NM) before intercepting the glide path.

Suspensions

Independent parallel approaches may be suspended under certain meteorological conditions (crosswind, turbulence, wind shear) that may increase track deviations towards the NTZ.