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Buyantukhaa
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Rwy Capacity: Mixed Use Vs. Non-mixed

Wed Sep 27, 2006 9:27 am

Hi all,

I saw some threads regarding mixed use being considered at LHR, and I had to think of some earlier observations:

AMS has many runways, that are always use for either TO or landing, but never mixed. The only runway that would realistically be able to handle this would be 18C-36C, but it doesn't happen (nor should it have to, with such an abundance of runways). Apparently LHR is similar.

At MUC, there are two parallel runways that would allow for TO on one runway, landing on the other. Yet both runways are used for mixed operation, and I have spent many times waiting up to 20 mins. to take off there, because heaps of planes were getting in.

There are plenty of other airports with two (or more) parallel runways, but I am not familiar enough with them to include here.

My question: does mixed use really increase capacity? Having two runways available for landing is better than one of course, but you'd have to slot in the take-offs in between. If you have one for take-offs only, then you can pretty much keep firing aircraft at the maximum capacity without having to worry about incoming aircraft. So what's the trade-off between the two?

Could anyone provide some numbers or other experience?
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Boeing7E7
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RE: Rwy Capacity: Mixed Use Vs. Non-mixed

Wed Sep 27, 2006 1:54 pm

It's based on the runway separation. ICAO differs slightly from FAA standards but the concept is the same.

With 4,300' of separation, runways operate independent of eachother in any weather condition.

2,500'-4,300 of separation is sufficient for heavies in VFR conditions only. In IFR, the runways are "dependent" and only one runway can be used for takeoff, the other for landing - or departures/arrivals on both runways are offset.

1,200'-2,500 of separation is sufficient for non-heavies in VFR conditions only. In IFR, the runways are dependent and only one runway can be used for takeoff, the other for landing - or departures/arrivals on both runways are offset.

The minimum separation is 750'.

Anything between 750' and 1,200' creates "dependent" runways in all conditions where one runway is used for takeoffs, the other for landing.
 
Tristarsteve
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RE: Rwy Capacity: Mixed Use Vs. Non-mixed

Wed Sep 27, 2006 9:58 pm

At LHR the runway use is regulated by agreements with the local ommunity. One runway is used for landing until 1500, then this changes to the other runway for 24hr. This useage is kept to strictly unless a runway is blocked. It leads to many problems, mainly the crossing of the runway by aircraft taxying to or from T4. If mixed mode was employed then all T4 aircraft could land or take off from the southern runway and runway crossing could be eliminated. Also there are times when there are a lot more aircraft waiting to land than take off, and vice versa. Mixed mode would then allow parallel landings or take offs. Mixed mode would definitely allow more movements at LHR, and less delays, but is banned by present regulations.
 
bomber996
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RE: Rwy Capacity: Mixed Use Vs. Non-mixed

Thu Sep 28, 2006 11:03 am

Quoting Boeing7E7 (Reply 1):
Anything between 750' and 1,200' creates "dependent" runways in all conditions where one runway is used for takeoffs, the other for landing.

But there are many pics at SFO with 757s and 747s on approach right next to each other?

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vikkyvik
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Joined: Thu Jul 31, 2003 1:58 pm

RE: Rwy Capacity: Mixed Use Vs. Non-mixed

Thu Sep 28, 2006 11:29 am

Quoting Boeing7E7 (Reply 1):
Anything between 750' and 1,200' creates "dependent" runways in all conditions where one runway is used for takeoffs, the other for landing.

Two questions (approximately):

1. What exactly does offsetting departures/arrivals mean? Does this mean you stagger them? I understand staggering departures, or staggering arrivals, but how does one do both?

2. SFO's runways are 750' apart, but I believe they have special procedures there that may go above and beyond the FAA mandates. But maybe not....However, LAX's northern runways (6L/R-24R/L) are ~700' apart. Yet 6R/24L is used for departures, and 6L/24R for arrivals (typically). Is this also a special case with specific procedures?

Thanks a lot.

~Vik
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Boeing7E7
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RE: Rwy Capacity: Mixed Use Vs. Non-mixed

Thu Sep 28, 2006 1:51 pm

Quoting Bomber996 (Reply 3):
But there are many pics at SFO with 757s and 747s on approach right next to each other?

Sorry. They are offset. If they weren't the 757 would be doing a back flip in the wake turbulence. Notice they are offset and the lighter aircraft is kept higher than the heavier aircraft above the wake turbulence.


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Here's the standard smart ass (Section 207):

http://www.faa.gov/airports_airtraff.../150-5300-13/150_5300_13_part1.pdf

Offset Approach Standard for SFO:

http://204.108.4.16/d-tpp/0609/00375IPRM28L_C.PDF

Quoting Vikkyvik (Reply 4):
1. What exactly does offsetting departures/arrivals mean? Does this mean you stagger them? I understand staggering departures, or staggering arrivals, but how does one do both?

You can use runway to launch a bird while landing a bird on the other, or two aircraft can appraoch both runways in a staggerd arrangement. One ahead of the other and often on a different glideslope to keep the in trail aircraft highers and avoid wake turbulence from a heavy.

Quoting Vikkyvik (Reply 4):
2. SFO's runways are 750' apart, but I believe they have special procedures there that may go above and beyond the FAA mandates. But maybe not....However, LAX's northern runways (6L/R-24R/L) are ~700' apart. Yet 6R/24L is used for departures, and 6L/24R for arrivals (typically). Is this also a special case with specific procedures?

Those are based on the old design standard, if either was built today, the close pairs of runways would be separated by at least 1,000' at LAX (preferably 1,200') and 1,200' at SFO. At LAX the inners are typcially used for departures (minimum separation of 3,500) and the outers for arrivals (minimum of 4,300'). To each pair the operation is dependent, but it doesn't matter as LAX has two independent departure streams from the inners and two independent arrival streams to the outers.

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