Re: parallel runways on airports

Date:         20 Mar 97 02:38:33 
From:         D.P.Rhodes@lboro.ac.uk (Darren Rhodes)
Organization: Loughborough University
References:   1
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On 09 Mar 97 12:39:40 , "Marc SCHAEFFER" <marcmsc@hotmail.com> wrote:
>I read in 'Aero international' that the two parallel runways 25L/07R and
>25R/07L at the Frankurt airport (FRA) can't be used at the same time since
>they are only seperated by 518 meters.
>- What's the minimum distance where two parallel runways can be used
>  at the same time ?
>- Are there other restrictions for these type of runways ?
>- Are the rules the same in Europe and the US ?

Okay, the current ICAO IFR standard for simulataneous use of parallel
runways states they must be 1,525m apart. Here simulataneous means
independent use,  i.e. arrivals and departures on each runway.

If the runways are closer than 1,525m they may be used as dependent
parallel runways. This is allowable down to 760m apart. For arrivals
at 760m spacing the aircraft must be staggered by a diagonal distance
of 3.7km apart, reducing through-put relative to independent
parallels.

The above are IFR standards. The US permits operation under VFR
(Visual Flight Rules) and in that case dependent parallels are allowed
down to 210m apart - a classic example being LAX which has two pairs
of close parallels - the pairs wide enough to be indendent of each
other, yet operated dependently within each pair. Europe does not
allow VFR rules to be used as the weather is more unpredictable.

The FAA and ECAC (European Civil Aviation Conference) have proposed
alterations to the above IFR standards. New radar systems allow radar
updates at 2.4 second intervals or less. Provided the airport is
equipped with such a system they propose intially to reduce from
1,525m to 1,035m for indepent use. This has been demonstrated
successfully in the US at Raleigh Durham airport. The ultimate goal is
to achieve 900m for independent use. Similarly dependent runways could
be operated at separations less than 760m with such radar systems.

The main aims is to increase the number of movements per hour at
airports like Frankfurt and allow new runways to be built closer
together to save on cost and also benefit the environment (in terms of
land use).