Is the airport capacity related to number of runways?

Question

Lets say two different airports have the same number of runways, and terminals capable of handling any number of passengers. I realise that year round climate may have an effect on the number of days that planes may be able to land. But are there any other major factors which are able to make a big difference to the number of passengers those airports would be able to process? For example, do the placement of runways interfere with air traffic control?

If both make maximum use of their capacity, is it likely that both would have very similar numbers of annual passengers?

Answer 1

Airport Capacity

At major airports the capacity of the system of runways is the most restricting element. While it is usually possible to increase capacity of the other airport elements or adding a new runway (plus associated taxiways) is very expensive and takes a very long time to complete.

The runway capacity is the principal cause of most extreme instances of delays that lead to widespread schedule disruptions, flight cancellations and missed flight connections. The runway capacity varies greatly from day to day and changes are difficult to predict (even a few hours in advance).

Factors:

The capacity of the runway system depends on several factors, the most important ones:

1. Mix of aircraft classes using the airport: the aircraft mix indicates composition of aircraft fleet that is using any particular runway (e.g. 25% S, 60% L and 15% H).
2. Separation requirements imposed by the ATM system: due to wind tip vortices, leading aircraft and trailing aircraft must be separated by a determined distance (Heavy aircraft are the ones that produce more wake turbulence).
3. Type and location of exits from the runway: trailing aircraft of any pair cannot touch down on the runway before leading aircraft is clear of the runway. High-speed runway exits (also well placed runway exits) reduce runway occupancy times for arriving aircraft.
4. Mix of movements on each runway and the sequencing of the movements: specified for all combinations of consecutive operations (arrival-departure). There's an important trade-off between maximum arrival and departure rates that an airport can achieve.
5. Lateral separation: (especially in bad weather) between aircraft approaching the same airport on parallel runways.
6. Sequencing and separation of departing and landing aircraft on runways that intersect.
7. Sequencing of aircraft approaching airports located in close proximity to one another, where one aircraft must cross the path of another aircraft landing at a nearby airport.
8. Direction and strength of winds.
9. Noise-related and other environmental considerations and constraints.

Conclusion:

It is difficult to predict the capacity of the runway system of an airport, so it is difficult to compare two airports with similar runway characteristics, since the factors depending on the airport capacity involve different design and operational parameters. Furthermore, everything is subject to the important probabilistic factor, the weather, which makes the prediction and comparison of airport capacity even more difficult.

Answer 2

This is a complicated question to answer but I'll try my best to give you an idea.

When you say number of runways there are a few situations; this will vary based largely on wind as well as when and where the airport was built, but there are two main cases to consider. Keep in mind the wind may prevent the use of certain runways.

1: Side by side runways. Large airports like KPHL, KJFK, KORD (and even places similar in size to Van Nuys Airport) have parallel runways. This can greatly aid in throughput as two planes can land/takeoff simultaneously

2: Intersecting Runways. In this case you still have two runways but they will cross each other and depending on aircraft size cannot be used simultaneously. If the airport supports GA or the runways intersect towards their respective ends a land and hold short may be possible. With intersecting runways you would, in theory, have less options since you can't have the simultaneous situation you do with parallel runways.

Other Factors

Aircraft Size: another thing to consider is runway length and aircraft size. Generally speaking runways at a given airport are often of different sizes. As such some aircraft may require a specific runway, if, on a given day you happen to only be landing large aircraft you may only be able to make use of one of your two parallel runways even though both are useable in the current wind.

Taxi Ways: for what it's worth I would not think taxi ways are a limiting factor in airport design. They often are the place where the queue builds up but generally are not the cause of the queue.

Ground Crew/Ground Resources: If we are talking strictly commercial operations it takes time and resources to turn a plane around (get it back in the air). The plane may need fuel or a de-ice (de-ice facilities have gotten better and are usually near the runway now). You may need a tug, a crew to load the plane, food, cleaning … you get the idea.

Physical Obstacles: Some airports are built in areas with tough terrain. This may cause all departures and takeoffs to come in from a single direction. This can limit the amount of traffic in and out of an area as well.

Noise Abatement: With the growing concern for local communities and increasing noise of jet engines, some airports have growing restrictions on when you can and can't take off. I fly out of KPNE and they have restricted runway use on Sundays as well as no touch and go's at various times. In this case two airports with the same number of runways may have different throughput due to runway restrictions.

Runway Approach Systems: Not all airports have instrument approaches on all runways (or any runway for that matter, although with the addition of GPS approaches, more and more airports have some kind of approach). If the weather is bad the better equipped airport will always have a greater throughput (an ill-equipped airport may prevent landings all together, although that's unlikely for commercial airports these days).

The locale is a big factor as well; if you build a huge airport in an area that no one wants to go to or leave, it's not going to see much traffic. Likewise if you build a tiny airport in Central Park, chances are you will have a stream of planes heading to and from the Hamptons in the summer….

Answer 3

In brief, parallel runways are built to increase capacity, intersecting runways are built to increase usability (i.e. crosswinds).