In the world's busiest airports, how is separation managed between departures and arrivals when there are only two parallel runways like in London Heathrow. What is the minimum safe separation?


1 Answer 1


With two runways, usually, one is dedicated to arrivals, and the other is dedicated to departures. That's the simplest way to handle separation -- only in-trail separation is involved.

That's usually the way traffic is managed at Heathrow (LHR) and Dubai (DXB), two of the world's busiest two-parallel-runway airports. At Heathrow, when in a westward flow (70% of the time) the runway functions are swapped about 3pm, to equalize noise impacts.

San Francisco (SFO) has two parallels, 28L and 28R, that are 750 ft apart -- very close. Under visual conditions, both runways are used for VISUAL approaches. Generally, aircraft arrive side-by-side, for wake avoidance.

For about an hour a day. 6am to 7am, when arrivals dominate, LHR allows arrivals on both runways. I don't know what separation rules are used. At SFO, under marginal conditions, both 28s are used for arrivals but aircraft are staggered and capacity is less than for visual operations.

  • $\begingroup$ Parallel landings at SFO are not simple visual approaches and require No Transgression Zone (NTZ) final monitor controllers. Feel free to use the link to expand on that part. Also see the chart labelled ILS PRM RWY 28L here. $\endgroup$
    – user14897
    Commented Mar 13, 2018 at 20:37
  • $\begingroup$ Worth mentioning that SFO can, weather permitting, use the perpendicular runways (1L and 1R) for most departures, which permits more capacity than if they just had the two parallel runways. $\endgroup$ Commented Mar 13, 2018 at 23:59
  • $\begingroup$ The 'usual' (over 90% of the time) way that SFO is configured is: arrivals on Rwy 28L and 28R; departures on Rwy 1L and 1R. Both runway pairs are separated by 750 ft -- really close. If you look at fly.faa.gov/Information/west/zoa/sfo/sfo_aar.htm, you'll see there are several ways to manage arrivals: side-by-side, staggered, in-trail, etc., each with its own arrival rate. $\endgroup$
    – user14736
    Commented Mar 14, 2018 at 21:16

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