Parallel runway operations

Two runways, different operating concepts

Independence describes the separation concept, not absence of monitoring.

Operating modes

Independent parallel approaches do not require the prescribed radar separation between aircraft on adjacent final approach tracks, because the approved geometry, monitoring and breakout safeguards provide the required protection. Dependent parallel approaches retain specified separation between adjacent approach aircraft. Simultaneous instrument departures use separate approved departure paths.

Segregated operations dedicate one runway to approaches and the other to departures. Semi-mixed operations use one runway exclusively for one movement type and the other for both; mixed operations allow both on each. Runway spacing, track geometry, surveillance, communications, procedures and approvals determine which combinations are allowed.

NOZ and NTZ

A normal operating zone contains the final track and acceptable deviations. The no transgression zone lies between the approach tracks and is monitored to protect the other stream from a penetration. Crossing into it triggers the prescribed intervention and potential breakout for the threatened aircraft; it is not an optional shortcut.

Approved independent operations require appropriate precision guidance/aircraft capability and surveillance performance, dedicated monitoring and prompt intervention. Severe weather or other conditions can prevent the operation when safe monitoring or tracking cannot be maintained. The approved AIP procedure and ICAO SOIR guidance define the installation-specific requirements.

Intercept and missed-approach geometry

A safe final pair also needs safe arrival and escape paths.

Intercept conditions

For the traditional independent ILS/MLS parallel approach criteria, the final intercept angle should not exceed 30 degrees; the aircraft needs the required straight and level segment before glide path interception and the specified vertical separation before the operation’s conditions are established. Use the approved procedure for the actual installation.

Missed-approach and departure tracks must provide the required divergence and separation for the approved mode; traditional independent parallel approach missed tracks diverge at least 30 degrees. Other approved modes and technologies have their own conditions. Do not assume that any two runways bearing similar numbers can operate simultaneously.

Know the breakout

Brief the missed approach for the assigned runway and the immediate response to a breakout instruction, including the operator’s automation procedure. A parallel approach can involve another aircraft at the same approximate distance on the adjacent final; a lateral deviation can become urgent quickly.

A normal published missed approach and an ATC-directed breakout are different actions. The pilot must respond to the actual instruction while retaining aircraft safety and following an ACAS RA when applicable. The model illustrates zone penetration; it is not a surveillance training simulator.

Can you apply the rules?

Four original questions. Choose from the facts, then review the explanation.