Dependent approaches:(Simultaneous parallel approaches)
Allow aircraft to approach parallel runways, but controllers must ensure a minimum separation from aircraft on the adjacent approach path (diagonal spacing) in addition to maintaining standard separation behind aircraft on the same approach path (in-trail spacing). Aircraft may not pass or be passed once they are established on their approaches.
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Independent parallel approaches:
Simultaneous approaches to parallel instrument runways where radar separation minima are not prescribed between aircraft using adjacent ILS.
Simultaneous instrument departure procedures and instrument approach procedures in the same direction on parallel runways. The nominal tracks of the departure procedures and of the missed approach procedures must diverge by at least 30° as soon as practicable.
There are three sorts of operations:
– One runway is used for approaches.
– The other one is used for departures.
– One runway is used for approaches and departures.
– The other one is used for either approaches or departures.
– Simultaneous parallel approaches with departures interspersed on both runways.
Based on (ICAO doc9157) Aerodrome Design Manuel Part 1 Runway, the minimum distance between center lines of 2 parallel (or near-parallel) runways:
1) For Visual Meteorological Conditions (VMC) operation:
*210m for category 3(runway length=1200m-1800m) and category 4(runway length>1800m)
*150m for category 2(runway length=800m-1200m)
*120m for category 1(runway length<800m)
2) Instrument flight Condition (IMC) operation:
*1035m for independent parallel approaches (radar separation minima between aircraft and adjacent centerline is not prescribed)
*915m for independent parallel approaches (radar separation minima between aircraft and adjacent centerline is prescribed)
*760m for independent parallel departures or Segregated parallel operations (one exclusive for departure and another for landing) PS: It can be reduced by 30m for each 150m arrival runways is staggered toward arrival aircraft down to 300m between the centerline of two runways, and vice versa (but no maximum)
When two runways are closer than the regulations above, only one can be “operated” at the same time (eg: LGW). Even though only one of the parallel runway would be operated at the same time, the separation of the runway have to follow the “Runway strip rule”, which is:
*75m each side from the center lines for category 3/4
*40m each side for category 2
*30m each side for category 1
Therefore minimum distance of two parallel runways is the sum of the strips, ie: minimum distance of two parallel 4E/F runways is 75+75=150 m from their center lines.
(The above is a global standard which represents the minimum requirement of the runway, other aviation authorities such as FAA in the US may have a stricter standard.)