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Would it make more sense to land on the inners and depart on the outers

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Would it make more sense to land on the inners and depart on the outers

Old 4th Apr 2018, 09:31
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It wonder if Overrun is still on pprune as he is an airport engineer. Would love to hear his opinion on this
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Old 4th Apr 2018, 11:29
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Originally Posted by Ian W
Interesting that nobody has noted that the real problem is the design of the airport terminals that require all aircraft to cross active runways to the central terminal buildings.
From a throughput point of view it would be far better to have multi-mode runways so as an aircraft touches down a departure lines up and as the arrival clears the runway the departure takes off to be airborne before next inbound is at 2 miles. There are no wake turbulence delays as the departing aircraft wake is not interfering with the landing aircraft and vice versa. Imagine if you like 4 Gatwicks alongside each other. So the airport has widely spaced non-interfering approaches to widely spaced runways with terminal buildings between each pair of runways linked by underground rail to the other terminals. Each terminal has two potential multi-mode runways alongside that will not require runway crossing after landing or before takeoff.

But why think about airport design let's make do with the way it's always been done.
Operating interleaved departures and arrivals on all of your runways sounds like a great way of unnecessarily p*ssing off the maximum number of communities surrounding an airport.

Maybe the way it's always been done isn't such a bad idea after all.
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Old 4th Apr 2018, 11:44
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There are problems with ILS interference.

this was a selling point for SmartPath, multi-mode with no interference.
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Old 4th Apr 2018, 11:49
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Originally Posted by DaveReidUK
Operating interleaved departures and arrivals on all of your runways sounds like a great way of unnecessarily p*ssing off the maximum number of communities surrounding an airport.

Maybe the way it's always been done isn't such a bad idea after all.
Only at Heathrow the communities know what that is.

With mixed mode runway occupancy times are leading, making the capacity ~25 arrivals and ~25 departures per hour. Two closely spaced parallels thus a higher capacity of ~35 arrivals and ~35 departures, as departures have to be coordinated with arrivals. Two independant runways will still have have an arrival capacity of ~35 but a departure capacity of ~45. The most important downside of mixed mode and closely spaced parallels is that the capacity reduces dramatically under limited visibility as (visual) confirmation of aircraft departing, landing and leaving the runway is essential.

The main problem with more than two parallel arrivals and departures is that your missed approaches for your middle runways can only go straight and thus interfere with your departure flows.
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Old 4th Apr 2018, 12:25
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Originally Posted by procede
Only at Heathrow the communities know what that is.
I'm not sure what you're saying here.
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Old 4th Apr 2018, 13:03
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Originally Posted by DaveReidUK
I'm not sure what you're saying here.
I'm refering to the protest against mixed mode operations. I think Heathrow is the only airport where, due to the runway alternation scheme, there would be resistance to this. For most other airports the overall noise impact is minimal at most.

Last edited by procede; 4th Apr 2018 at 13:03. Reason: typo
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Old 4th Apr 2018, 13:44
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Originally Posted by procede
I'm refering to the protest against mixed mode operations. I think Heathrow is the only airport where, due to the runway alternation scheme, there would be resistance to this. For most other airports the overall noise impact is minimal at most.
Not necessarily.

The previous poster was suggesting that mixed-mode runways are more desirable than segregated mode runways (the latter being the subject of this thread). Whereas that may well be true from an ATC perspective, it isn't from the environmental point of view.

Most people living under an approach or climbout flightpath are capable of discerning whether or not they have aircraft flying over their head at any given time.

Yes, it's true that Heathrow has arrival and departure runways on opposite sides of the CTA rather than the inner/outer arrangement being discussed here, so the respite gains from segregated operation are more pronounced, but it's by no means unique in that respect.
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Old 4th Apr 2018, 18:26
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The Lden noise contours (with the same traffic) will be almost identical with mixed mode vs. closely spaced parallels. ATC will surely prefer segregated runways, as workload will be lower and capacity more constant, but of course it is more expensive for the airport. Also during maintenance still one runway will be available.

For Heathrow mixed mode means the same amounts of flights overhead per day per runway, thus the same Lden contour, but during the whole day instead of just concentrated in the morning or afternoon.

Last edited by procede; 4th Apr 2018 at 18:27. Reason: Typo
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Old 4th Apr 2018, 20:31
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Originally Posted by procede
For Heathrow mixed mode means the same amounts of flights overhead per day per runway, thus the same Lden contour, but during the whole day instead of just concentrated in the morning or afternoon.
Which is, of course, the reason for the fierce environmental opposition to mixed-mode at LHR.
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Old 5th Apr 2018, 16:44
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Originally Posted by Ian W
Interesting that nobody has noted that the real problem is the design of the airport terminals that require all aircraft to cross active runways to the central terminal buildings.
From a throughput point of view it would be far better to have multi-mode runways so as an aircraft touches down a departure lines up and as the arrival clears the runway the departure takes off to be airborne before next inbound is at 2 miles. There are no wake turbulence delays as the departing aircraft wake is not interfering with the landing aircraft and vice versa. Imagine if you like 4 Gatwicks alongside each other. So the airport has widely spaced non-interfering approaches to widely spaced runways with terminal buildings between each pair of runways linked by underground rail to the other terminals. Each terminal has two potential multi-mode runways alongside that will not require runway crossing after landing or before takeoff.
The ideal structure (if you have a lot of land), is something like that at KDEN. Planes can land and decelerate towards the terminal, and take off without backtracking. Further, there are staggers to avoid runway crossings on parallels. http://155.178.201.160/d-tpp/1804/09077AD.PDF But then again, KDEN covers 52.4 square miles. https://en.wikipedia.org/wiki/Denver...tional_Airport
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Old 5th Apr 2018, 20:42
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The best solution is at KDEN. Runways are like spokes from the terminal. Parallels pointing away from the terminal are both used for take off. Those pointed at the terminal are both used for landings depending on winds. Unfortunately most airports aren't built in the middle of nowhere with a million acres available, but it is a really nice layout.
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Old 6th Apr 2018, 17:07
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Lots of good points made in this thread.

Don't forget about aircraft weight and how it affects taxi maneuverability.

Departing aircraft are heavy and take a longer time to accelerate from a stop. If multiple departures are waiting to cross the inner 'arrivals' runway, it will take awhile for each of them to build momentum to cross the runway. An additional consideration is the flight attendants: during taxi-out they are up doing safety demonstrations and walking around.

On the other hand, arriving aircraft are lighter. Multiple arriving aircraft can cross the departure runway quickly because they can accelerate and maneuver more easily. Furthermore, the flight attendants and passengers are all seated and belted, so smooth taxiing is less of a consideration.
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