8herveg
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### Minimum Distance Allowed For Parallel Runways?

I was wondering what the minimum distance is for parallel runways if they are to be both used at the same time.

Both LAX and ATL have parallel runways...are they all used at the same time?

BWilliams
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### RE: Minimum Distance Allowed For Parallel Runways?

Minmum distance for simultaneous landings on parallel runways is 4300ft. (how the F I remember reading that is beyond me. o.O)

In ATL.. they don't have an option but to use parallel runways -- ALL the runways are parallel!

vikkyvik
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting BWilliams (Reply 1):In ATL.. they don't have an option but to use parallel runways -- ALL the runways are parallel!

Same as LAX.

However, "simultaneous" landings implies using ILS, does it not?

For instance, LAX, BOS, SFO, and various other airports have parallel approaches to their parallel runways, that are much less than 4300 feet apart, in VFR conditions.

LAX's north complex runways (6L/R-24R/L) are about 700 feet apart, centerline-to-centerline. South complex (7L/R-25R/L) are now 800 feet apart, I believe. SFO's two sets of parallel runways are 750 feet apart.

Depending on the type of approach (simultaneous, staggered, etc...) there are different minimum distances. I cannot ever keep them straight.
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timz
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### RE: Minimum Distance Allowed For Parallel Runways?

No idea what the rules are in the rest of the world, but in the US 4300 ft allows simultaneous independent ILS approaches-- i.e. no need for ATC to arrange any longitudinal separation. If ATC does stagger the approaches then you can have simultaneous ILS approaches to runways... is it 3000 ft apart? Or maybe 2500?

Looking at the rules you'd think it wouldn't be legal to do the simultaneous visual approaches that they regularly do at SFO-- it seems to say the runway edges have to be at least 600 ft apart, and presumably SFO's runway edges are 550 ft.

Smaller aircraft can land closer than that-- SNA's runway centerlines are 500 ft apart, and here and there other airports are closer than that.

Somebody said new construction has larger required separation-- if you're building a new airport, that is. Adding new runways to an existing airport probably only has to meet the old standards.

OPNLguy
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting Timz (Reply 3):If ATC does stagger the approaches then you can have simultaneous ILS approaches to runways... is it 3000 ft apart? Or maybe 2500?

2,500 feet for (parallel (staggered) ILS approaches, and 4,300 feet for simultaneous (wingtip to wingtip) ILS approaches.

The fact that SFO 28L/R don't meet either criteria explains why they can (and often do) go single runway ILS (with big delays) when seemingly "minor" ceilings and visibilities come in and wipe out the ability to conduct visual approaches to both 28L/R. I know you know this, but maybe others don't...
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KELPkid
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### RE: Minimum Distance Allowed For Parallel Runways?

So, what is the criteria for determining the distance?

A worst-case assumption, where aircraft A (on the right) goes full-scale deflection to the left while aircraft B (on the left) goes full-scale deflection to the right on the localizers? 3 degrees of of the centerline, no?

IIRC from my instrument and commercial groundschools, when parrallel approaches are active, there is a controller who is doing nothing but constantly monitoring the space between the parrallel glidepaths, and if that controller transmits on the radio, it overpowers the appropriate approach and/or tower controller.
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vikkyvik
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting KELPkid (Reply 5):A worst-case assumption, where aircraft A (on the right) goes full-scale deflection to the left while aircraft B (on the left) goes full-scale deflection to the right on the localizers? 3 degrees of of the centerline, no?

Those two paths will intersect at some distance from the thresholds. So with 4300 feet being the minimum for parallel non-staggered ILS approaches, the localizer signals will intersect about 7.77 miles from the runway thresholds (assuming colinear thresholds).

At least, I think that's what you were saying.

I also don't know how far out aircraft typically begin following ILS signals...
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KELPkid
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting Vikkyvik (Reply 6):I also don't know how far out aircraft typically begin following ILS signals...

5 (nautical) miles from the FAF (final approach fix) to the missed approach point/decision height seems to be about the norm...some ILS'es are longer and some are short. I'd say 80-90% of ILS approaches allow the controller to vector the aircraft to the FAF...

IIRC, a localizer signal is considered usable out to around 20 nautical miles or so, assuming no terrain interference or other mitigating factors. Of course, it is also a very narrow signal. I know that there are a few airway intersections in the world that can be identified by airway radial + localizer needle centered   .
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dragon6172
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting Timz (Reply 3): Adding new runways to an existing airport probably only has to meet the old standards.

Not so sure about that. Look at the new runways at IAD and ATL and they are well away from the ones they parallel. Not sure if its to meet the new standard or to prevent restricting some flow in weather.

Also, places like LAX and ATL use the two outter runways for approaches to increase the seperation. Not sure what the actual distances are at the two places, but I do not think you typically see aircraft approaching both parallels on the same side of the field at one time.

[Edited 2008-06-18 15:44:59]
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IAHFLYR
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting Vikkyvik (Reply 2):However, "simultaneous" landings implies using ILS, does it not?

I don't think simultaneous landings implies anything other than the aircraft touch down simultaneously.

Now the phrase simultaneous approaches implies only that approaches are being conducted to more than one runway.....not necessarily even parallel runways!

The correct phrase used in the U.S. for approaches conducted to parallel runways with the approved distance between center lines is "parallel dependant" or "simultaneous independent" approaches were you are able to conduct visuals or ILS approaches if you have the final monitors in place to monitor the runway center lines.

 Quoting Vikkyvik (Reply 2):Depending on the type of approach (simultaneous, staggered, etc...) there are different minimum distances. I cannot ever keep them straight.

And then there is the triple parallel runways where you are able to conduct triple simuls" as long as the airfield elevation IIRC is less than 1,000' MSL and the runway center lines are each at least 5,000' apart from the next runway centerline.

 Quoting KELPkid (Reply 7):5 (nautical) miles from the FAF (final approach fix) to the missed approach point/decision height seems to be about the norm...some ILS'es are longer and some are short. I'd say 80-90% of ILS approaches allow the controller to vector the aircraft to the FAF...

Actually vector to the final approach course outside the FAF applying the correct intercept angle and distance from the fix when required due to the weather. If visual approaches are being conducted then at times ATC will clear an aircraft direct to the FAF to report the airport or preceeding traffic in sight.

 Quoting KELPkid (Reply 7):a localizer signal is considered usable out to around 20 nautical miles or so

The localizer is normally certified to 18 NM from the antenna, unless it has been flight inspected for an expanded service volume then it may be greater distance.
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting Timz (Reply 3):Somebody said new construction has larger required separation-- if you're building a new airport, that is. Adding new runways to an existing airport probably only has to meet the old standards.

The new one (18R-36L) at AMS (which has existed since 1916) is at 2100m (I think) from the existing one. There were plans of inserting another runway in between, but I think this plan was abandoned in favour of a new parallel 06-24.
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Mir
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting IAHFLYR (Reply 9):And then there is the triple parallel runways where you are able to conduct triple simuls" as long as the airfield elevation IIRC is less than 1,000' MSL and the runway center lines are each at least 5,000' apart from the next runway centerline.

I don't know about the airfield elevation part - DEN can land triple parallel.

 Quoting KELPkid (Reply 5):IIRC from my instrument and commercial groundschools, when parrallel approaches are active, there is a controller who is doing nothing but constantly monitoring the space between the parrallel glidepaths, and if that controller transmits on the radio, it overpowers the appropriate approach and/or tower controller.

That's a PRM approach, which allows for simultaneous approaches to parallel runways as little as 3,400 feet apart, or 3,000 feet apart if one of the courses is offset. Not all simultaneous approaches are PRM - those with spacing of over 4,300 feet don't need it.

Then there's the SOIA approach, which is what SFO has. For a SOIA approach, rather than have the runways separated by at least 3,000 feet, they have the approach courses separated by at least 3,000 feet. The ILS to 28L is a straight-in approach, and 28R has an LDA with glideslope that is offset a couple of degrees. Pilots flying the ILS to 28L can go all the way down to Cat I minimums. Pilots flying the LDA to 28R can only go as far as the point where the approach courses are 3,000 feet apart before they have to have visual contact with the other traffic. That is the missed approach point, and beyond that a go-around must be made if the traffic cannot be seen, since there is no way to guarantee separation in IMC. Naturally, the minimums for this approach are quite a bit higher - 2,100 feet ceiling and four miles visibility. And thus, when fog rolls in, SFO is down to only one runway for landing.

 Quoting Vikkyvik (Reply 6):Those two paths will intersect at some distance from the thresholds. So with 4300 feet being the minimum for parallel non-staggered ILS approaches, the localizer signals will intersect about 7.77 miles from the runway thresholds (assuming colinear thresholds).

It's not quite as simple as that, since not all localizers widen equally as they get farther from the runway. The localizer is placed at the far end of the runway, and is calibrated to be 700 feet wide for full deflection at the threshold of the runway. So the longer the runway is, the narrower the beam will be (it varies between three and six degrees).

Worst case scenario: a six degree wide localizer. The runway centerlines are 4,300 feet apart, so the distance between full deflection on both localizers is 3,600 feet at the thresholds. (4,300 minus 350 from one side and 350 from the other). If my math is right, full deflections would intersect 5.6nm from the threshold. On the other hand, with a 3 degree localizer, interesection would be 11.25nm.

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JoeCanuck
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### RE: Minimum Distance Allowed For Parallel Runways?

It was a pretty cool sight to be on final at DFW and look out the window to see another md-80 at the same altitude, landing at the same time.
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IAHFLYR
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting Mir (Reply 11):I don't know about the airfield elevation part - DEN can land triple parallel.

Right out of the .65! DEN is using Final Monitor Assist (FMA) in STARS even though they are running an ARTS 3E system.......I think that gets them the ability to do TRIPS.
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BooDog
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### RE: Minimum Distance Allowed For Parallel Runways?

Quoting Mir (Reply 11):
I don't know about the airfield elevation part - DEN can land triple parallel.

Quoting IAHFLYR (Reply 13):
Right out of the .65! DEN is using Final Monitor Assist (FMA) in STARS even though they are running an ARTS 3E system.......I think that gets them the ability to do TRIPS.

35L and 35r are separated by over 5,000 feet. 34 is over 7,000 feet to the west of 35L. All that spacing is what allows the triples.

When DFW built 17L/35R in the mid nineties, they built it EXACTLY 5,000 feet from the nearest parallel runway.

[Edited 2008-06-18 20:24:47]
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P3Orion
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### RE: Minimum Distance Allowed For Parallel Runways?

Depends on the operation. While stationed at NHZ ATCT/TRACON in the Navy, our parallels (19L/19R) were seperated by 500 feet (700' centerline to centerline). We were authorized to conduct simo's between IFR and VFR or VFR and VFR.

[Edited 2008-06-18 20:58:49]

[Edited 2008-06-18 20:59:34]
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vikkyvik
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting Mir (Reply 11):That's a PRM approach, which allows for simultaneous approaches to parallel runways as little as 3,400 feet apart, or 3,000 feet apart if one of the courses is offset. Not all simultaneous approaches are PRM - those with spacing of over 4,300 feet don't need it.

These are instrument approaches, correct?

 Quoting Mir (Reply 11):It's not quite as simple as that, since not all localizers widen equally as they get farther from the runway. The localizer is placed at the far end of the runway, and is calibrated to be 700 feet wide for full deflection at the threshold of the runway. So the longer the runway is, the narrower the beam will be (it varies between three and six degrees).

Ah, OK - thanks for the clarification.

 Quoting Mir (Reply 11):If my math is right, full deflections would intersect 5.6nm from the threshold. On the other hand, with a 3 degree localizer, interesection would be 11.25nm.

Damn. I was using 6 degrees, but I calculated from the approach end threshold, instead of the far threshold.
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IAHFLYR
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting BooDog (Reply 14):35L and 35r are separated by over 5,000 feet. 34 is over 7,000 feet to the west of 35L. All that spacing is what allows the triples.

Respectfully, the field elevation of DEN requires a high resolution color monitor such as a PRM or FMA per the .65, unless of course the runways are minimum of 3 NM or more separation from each other.

From the 7110.65, para 5-9-7:

3. Triple parallel runway centerlines are at least 5,000 feet apart and the airport field elevation is less than 1,000 feet MSL.

4. A high-resolution color monitor with alert algorithms, such as the final monitor aid or that required in the precision runway monitor program shall be used to monitor approaches where:

(a) Triple parallel runway centerlines are at least 4,300 but less than 5,000 feet apart and the airport field elevation is less than 1,000 feet MSL.

(b) Triple parallel approaches to airports where the airport field elevation is 1,000 feet MSL or more require the high resolution color monitor with alert algorithms and an approved FAA aeronautical study.
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HaveBlue
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting BWilliams (Reply 1):In ATL.. they don't have an option but to use parallel runways -- ALL the runways are parallel!

Same in Orlando, FL. All 4 runways at MCO are parrallel.
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vikkyvik
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting IAHFLYR (Reply 17):Respectfully, the field elevation of DEN requires a high resolution color monitor such as a PRM or FMA per the .65, unless of course the runways are minimum of 3 NM or more separation from each other.

What is the reasoning behind the below 1000 MSL vs. above 1000 MSL?
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IAHFLYR
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting Vikkyvik (Reply 19):What is the reasoning behind the below 1000 MSL vs. above 1000 MSL?

Have to have somebody 100% smarter than I answer that.....maybe just another one of those things that make you go hmmmm!!!!
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timz
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting Dragon6172 (Reply 8):Look at the new runways at IAD and ATL and they are well away from the ones they parallel.

They're 4300 ft away, or maybe a bit less.

 Quoting Dragon6172 (Reply 8):places like LAX and ATL use the two outter runways for approaches to increase the seperation.

Forgot to check ATL, but the inners at LAX are 4500+ ft apart, so presumably separation isn't a problem.

BooDog
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting IAHFLYR (Reply 17):Respectfully, the field elevation of DEN requires a high resolution color monitor such as a PRM or FMA per the .65, unless of course the runways are minimum of 3 NM or more separation from each other. From the 7110.65, para 5-9-7: 3. Triple parallel runway centerlines are at least 5,000 feet apart and the airport field elevation is less than 1,000 feet MSL. 4. A high-resolution color monitor with alert algorithms, such as the final monitor aid or that required in the precision runway monitor program shall be used to monitor approaches where: (a) Triple parallel runway centerlines are at least 4,300 but less than 5,000 feet apart and the airport field elevation is less than 1,000 feet MSL. (b) Triple parallel approaches to airports where the airport field elevation is 1,000 feet MSL or more require the high resolution color monitor with alert algorithms and an approved FAA aeronautical study.

Did not know that. Thank you.
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CosmicCruiser
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### RE: Minimum Distance Allowed For Parallel Runways?

 Quoting HaveBlue (Reply 18):All 4 runways at MCO are parrallel.

Most often one is used for landings and the closest adjacent one for t/os. Eg. CDG usually uses 27L for t/o and 27R ldg and 26L ldg and 26R t/o.

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