“To create a unique symbol for each place”

Bruce Fairbanks, founder of Fairbanks Arquitectos, has accumulated extensive experience in the design of airport buildings since 1996 when he won the tender for the construction of the Madrid-Barajas control tower.

Presently in the world of airports there is a trend to promote the control tower as a symbol, an image that represents the airport and a reference point for the arrival in, and departure from the city where it is located. This trend has created increased interest in architectural execution in the design of control towers in addition to their functional requirements. It is precisely the individuality of these requirements that significantly affects the type of building, such that throughout history there are various examples of “types” of tower designs, which, once designed, were repeated in various airports: one notable case is the leoh Ming Pei control tower. It was designed between 1962 and 1965 with the objective implementation in 70 airports, although in the end 16 were built. The concept of locating in upper levels strictly that which was necessary was developed, putting the maximum amount of functions in the base building, which was adapted to the specific characteristics of each location. As such, the tower could be prefabricated and repeated with standardised equipment, giving the airport network an image of safety since a controller could work in any location without having to adapt. The tower was designed with 5 standardised heights (18-46 m) in accordance with visibility requirements in each location. The control tower’s cab is pentagonal so there are no parallel façades and so as to avoid reflections. In Spain, in the 1970s, Juan Montero Romero, an aeronautical engineer, built a tower, which was repeated in several cities: Málaga, Alicante, Valencia, etc.

To create a landmark, the architect must find within the functionality the characteristics that distinguish one tower from others

Converting control towers into airport landmarks and reference points for cities is a challenge in the work of an architect: creating a symbol, always unique for each location, which meets all of the requirements for the optimal functioning of the tower. The location, the height of the control room, its form and the layout of its structural elements are some of the first elements to define. Control towers typically have a base building and a shaft that supports the upper floors, which are designed to adapt to the control operations. Given the form, with an upper part and a lower part and the height of the type of building, in my opinion it is essential to incorporate the construction process into the design of the tower, and this is what I have done in those which I have designed. This design comes from an analysis of the functional aspects, the programme and the location. To create a landmark, the architect must find within the functionality the characteristics that can distinguish one tower from others and strengthen them to create a unique tower with its own character in each case.

Analysis of four cases

The following examples of control towers show diferente conceptual approaches to design this building type and the elements that diversify its design.

1962. Dulles airport, Washington DC
Eero Saarinen

The Dulles tower has all of the equipment rooms at a height, elegantly assembled by Saarinen with two juxtaposed bodies. The form of the tower is integrated with that of the terminal building, also designed by the same architect.

1992. JFK airport, Nueva York
Pei Cobb Freed & Partners

The upper part of the JFK tower, 97.5 metres in height, contains only the aerodrome control cab and half way up the shaft there is the platform control room, which takes the same form as the upper levels.

1997. Adolfo Suárez Madrid-Barajas airport
Bruce Fairbanks

The Adolfo Suárez Madrid-Barajas control tower had the specific feature of a 400 m² equipment room located at a height. To resolve the transition between the shaft of the tower and the projection, an inverted half sphere was adopted, with a floor for air conditioning equipment being inserted in the support. The octagonal shape defined for the
cab is extended throughout the top of the building, the structural design of a central column and 8 perimeter columns is repeated on all levels.

Another particular feature of the tower is the construction system designed as an integral part of the design. The shaft is built with prefabricated segments assembled in spirals, which, on the inside, contain the service ducts and circumscribe the emergency stairway. The upper floors were built with a metallic structure on the floor and subsequently hoisted onto the shaft. The system allowed the tower to be built in nine months, without using scaffolding.

2004. Barcelona-El Prat airport
Bruce Fairbanks

The functional requirements were similar to those of Barajas, with the exception that a large part of the equipment is located in the base building. The resistant structure is defined independently from the functional elements of the shaft, which was developed as a representative design element. An eight-pointed hyperbola generated from the octagonal shape of the cab holds the upper floors.

The hyperbola links the tower with Catalan Modernism and Antoni Gaudí, who used this form in many of his designs, including on the domes of the Sagrada Familia. The construction system is a representative part of his design. The assembly of the hyperbola, built with prefabricated concrete girders, was guided by a central aluminium structure designed to contain the elements of the shaft. The upper floors were built on land and hoisted into position, supported by the eight points of the hyperbola, consolidating the whole structure when it was under load.

“In the future, it will not be necessary to view operations”

Roberto Serrano has participated in more than 50 aeronautical projects, amongst them, the NET and SAT control towers of Madrid-Barajas airport and the new control tower of Eldorado airport (Bogotá).

Although the first control towers date back to the 1920s (in 1921, Croydon airport in London was the first in the world to introduce air traffic control), it was from the 1930s that they became commonplace, due to the fact that growing aircraft traffic made controlling and managing it necessary. At that time, in which technology was nothing like the current systems, the need to visually supervise aeronautical operations around the airport was met by placing the control room (cab) in an elevated and predominant position of the airport (control tower).

To date, the first steps in designing a control tower involve establishing its site and the height of the cab. Internationally, to meet the viewing requirements from the cab, the recommendations of the Federal Aviation Administration (FAA) are applied. The optimum height and location of a control tower is the result of weighing up many considerations. The view from the cab requires the air traffic controller to be able to distinguish the aircraft and vehicles that circulate in the manoeuvring area, as well as aircraft that fly over the airport, particularly in take-off and landing paths. The objective is to have the maximum visibility possible and avoid the sun, external light sources and reflections from adjacent buildings affecting the visibility of the controller.

Nowadays, technology allows a practically blind landing

With regard to the location, we must consider the potential effects of local weather: flood areas or areas susceptible to fog. Its compatibility with the potential future development of the airport must also be studied, thereby avoiding the need to relocate the tower before the end of its life cycle. Insofar as possible, the tower and its buildings should be located on the landside of the airport, thus avoiding access through the airfield and facilitating the entry of staff. Furthermore, the location should be such that it does not affect the quality of the signals of the airport’s radio navigation aids (ILS, VOR, DME, etc.), or communication systems. The minimum height required for the control tower can be obtained with the aid of the FAA visibility analysis tool, ATCTVAT (Airport Traffic Control Tower Visibility Analysis Tool), in accordance with the physical conditions of the airport.

Once the position and height has been determined, the infrastructure is designed, and generally includes a cab and an antenna field, which, located on the roof of the cab, normally has communications antennas, radio relays, and other electronic and lightening protection elements. Furthermore, there are areas for staff, equipment, power, air conditioning, etc.

In an era in which technology provides information to pilots to allow a practically blind landing, is it necessary to keep air traffic controllers in a high position so they can see these operations? In the future, air traffic control rooms will probably be in buildings that are more similar to those of offices or air traffic control centres than the current towers.

The future has already become reality

2015. Control tower of Örnsköldsvik airport, Sweden

Recently, Örnsköldsvik airport in Sweden replaced its control tower with high-tech cameras. Signals are sent to controllers stationed in Sunvsal airport, located around 150 kilometres away, from a 25-metre mast with 14 high-definition cameras. The high performance of these cameras eliminates blind spots, provides information in rain, fog or snow and, along with a whole series of weather sensors, microphones and other devices, it allows controllers to feel as if they were beside the runway. The Swedish Transport Agency approved remotely operated towers on 31 October 2014. Six months later, the first airplane landed in Örnsköldsvik airport using the remote tower services.

Spain is the third most popular tourist destination in the world in terms of revenue and for another year it has beaten its own record by exceeding 68 million visitors in 2015, three million more than the previous year. According to all of the analyses carried out, a factor that has benefited the sector is the situation of political instability from 2011 in Mediterranean destinations such as Tunisia, Egypt and Turkey. They all compete with Spain, which mainly receives European tourists: seven out of ten are British, French, German or Italian although, in relative terms, the increase in arrivals from the US and Asian countries is notable. According to Turespaña data, almost 80% of the total number came by air (half on a low-cost airline); a determining factor in this figure is that the Balearic and Canary Islands, for example, which are amongst the most touristic destinations in the world, are islands. As such, in 2015 all of the 46 airports in Spain registered more than 207 million passengers, 5.9% more than the previous year.

During 2015, eight out of ten visitors came to one of the 46 Spanish airports

Besides the two major Spanish airports, Adolfo Suarez Madrid-Barajas and Barcelona-El Prat, which between them accounted for 41.7% with 86.5 million, more than 101.7 million passengers –49.1% of the total– were counted in the 14 airports classified as “touristic”, coinciding with the most touristic destinations: the Balearic Islands, Palma de Mallorca, Ibiza and Menorca; the Valencian community, with Valencia and Alicante airports; Andalusia, with Málaga and Seville; the Canary Islands, with the airports of Gran Canaria, Tenerife South, Lanzarote, Fuerteventura and La Palma; and Catalonia, with Girona and Reus airports.

They all underwent processes of improvement and enlargement in the 2000s in order to increase their capacity, closely linked to the growth in tourism, known as the Barajas Plan, Barcelona Plan, Levant Plan, Málaga Plan, Canary Islands Plan, etc. During this time, Ineco has provided its services to the Ministry of Development and Aena in the planning and execution of the activities. Since 2008 it has also been in charge of the Traffic Forecast Office, which plays a key role in airport planning. A few times a year, a team of engineers and technicians updates the forecasts, and this is carried out with a macroeconometric model called PISTA (Integrated Prognosis of Air Traffic Systems), also developed by Ineco, with a specific methodology based on the concept of a ‘network’ and independent models for the national and international segments, based on significant economic variables. Furthermore, in preparing the specific forecasts for each airport and for the short-medium-term, other factors are taken into account such as competition from other means of transport (mainly AVE), the existence of other airports in the area of influence, changes in offers from airlines (new destinations, greater frequency, new models of airplanes used, etc.), special events (sports competitions, summits, etc.) and others.

Since 2008, Ineco has also been in charge of the Traffic Forecast Office, which plays a key role in airport planning

Not only are volumes of passengers, operations and goods for each airport in the network forecast, but the design values (DHP, design hour passengers; and DHA, design hour aircraft) that are essential for adequate planning of the infrastructure are also considered, since they allow detection of the needs that airports will have and, furthermore, when it will be necessary to carry out the activities. The results of the traffic forecasts are used to prepare Aena’s business and investment plans, as well as to design commercial strategies in airports and, as such, they are very important.

The renovation work is part of the comprehensive restoration project drawn up by Ineco in 2008 which sought to remedy shortcomings while remaining consistent with the historic character of the architecture. These large, riveted iron structures were built as a result of the Industrial Revolution during the 19th century and are epitomised by the Eiffel tower. Spain lagged a bit behind other cities with regard to the use of iron in architecture and engineering as can be seen in countless examples from Paris, London, Amsterdam, Belgium and Germany in addition to Boston and New York in the United States.

With all of this, transport infrastructure in 19th-century Spain such as stations, bridges and viaducts requiring versatility, luminosity, spaciousness and low prices were easily adapted to the engineering of iron which was best received by engineers of that time period as well as by architects. Examples of riveted iron infrastructures in Spain include the Atocha and Delicias railway stations, the Catalonia Railway Museum, the Valencia railway station and the Aranjuez railway station –the main feature of this article. Furthermore, some quite representative buildings include Sabatini’s Royal Firearms Factory in Toledo and the Geological and Mining Institute of Spain, in addition to bridges and viaducts such as the prominent Triana Bridge.

Spanish transport infrastructure in 19th-century such as stations, bridges and viaducts requiring versatility, luminosity, spaciousness and low prices were easily adapted to the engineering of iron

Aranjuez station is one of the most characteristic vestiges of the industrial age of the 19th century. The earliest railway facilities at Aranjuez were built in 1851 for the line connecting Madrid with Alicante, popularly known back then as the ‘Tren de la Fresa’ (The Strawberry Train) and whose name is now in use once again for tourist services. This station also provides service to the C3 Madrid-Aranjuez commuter rail line. It is the second oldest railway line in Spain (the oldest is the Barcelona-Mataró line, 1943) and is one of the monuments of the Royal Sites of Aranjuez, a Unesco World Heritage Landscape Site since 2001. This line originally reached all the way to the Royal Palace. The original station faced towards the palace on grounds of the company’s prestige and the fact that they needed support from the monarchy. Nevertheless, this location caused so many problems affecting train traffic that it became necessary to build a new station with a completely different layout. The platform marquees are living proof of the iron beams and framework –signs of progress from that time period– that were used to construct public buildings such as stations, markets, factories, libraries and bridges.

The technique of riveting

The steel marquees, roofed by fibre cement and fluted glass, were built around 1851 to provide shelter over the station’s three platforms which were later renovated around 1980 in order to adapt them to the trains and general regulations at that time. As can be observed in the images, the marquees suffered from corrosion problems that affected their structural framework, foundation and ornamentation due to an unsatisfactory roof water drainage system, thus causing damage to the suspended wooden ceiling and corroding the metal. Rehabilitation and restoration of these marquees was a year-long, painstaking process that rediscovered the traditional technique of riveting.

Riveting is the process of joining together several metallic pieces (metal sheets and/or profiles) using rivets. Rivets are elements that are similar to screws –but without the thread– consisting of a cylindrical shaft called a shank or the body, and a head normally shaped like a spherical cap, such as the rivets utilised for the marquees at Aranjuez station. These rivets are manufactured from ductile, malleable and durable metals such as copper, aluminium, some alloys and mild steel, such is the case with the rivets presented herein.

Riveting is the process of joining together several metallic pieces using rivets –elements similar to screws but without the thread- consisting of a cylindrical shaft and a head

To join together metal pieces made from steel, rivets are used –also made from steel– whose quality and characteristics can vary. Holes are drilled just once, piercing through two or more pieces, after having assembled, clamped and tightly screwed said pieces together. Once the holes have been drilled, the pieces are separated from each other in order to eliminate metal scrap, remnants and sharp edges from the surface. The diameter of the holes, save for exceptional cases, is made 1 millimetre larger than the diameter of the body of the rivet. Selecting the length of the body of the rivet is very important: after the rivet is placed in a furnace and uniformly heated to a temperature between 950 and 1,050 ºC in order to allow for its moulding, the riveting process is carried out by introducing the heated rivet into the hole on the pieces which are to be joined together. The body of the rivet should be cast and forged in order to form the shop head of the rivet. This piece must completely fill the hole. To form the shop head, either a riveting machine applying uniform compression is utilised, or a pneumatic hammer with a riveting pin or a bucking bar is used, always held steadily in place. These tools –not the direct strike of a hammer– are used to form the rivet’s second head. Both the furnace and the riveting machine need to be located close to the area where the riveting is to take place so as to avoid significant cooling of the rivet before it is set into place. The pieces that are joined together must lie perfectly flush and tight against each other to ensure a union without bending or warping. Afterwards, the rivet is introduced into the pieces that are being joined together, and the body of the rivet is forged. This process is carried out using a pneumatic hammer and a bucking bar on the spherical head of the rivet.