Preparing for take-off

At over 36 m long, the wings of the double-decker Airbus A380 are the largest ever designed for a commerical aircraft. As with other Airbus planes, it will be a pan-European creation, with its parts being constructed around the continent before being transported to Toulouse, France for the final assembly.

The wings, like those of their predecessors, will be constructed in the UK. Their vast scale means that existing manufacturing facilities are too small to contain them. The solution is a £350 million aerospace factory sited alongside an existing Airbus manufacturing facility in Broughton, North Wales. Covering 83 000 m2, it will house wing assembly for the 555-seater A380 as well as other aircraft manufacturing activity.

The construction of the facility over a period of 46 weeks was arguably as creative and tightly controlled a process as will be the wing manufacture, involving open procurement methods, prefabrication and close working.

The tender process was based on Airbus' strategic requirements. Airbus appointed BAE Systems as its project manager, who produced footprint sketches on which the tender teams based their proposals. "The requirements were were much more global than price," reports Mike Cooke, senior mechanical engineer with m&e contractor Haden Young. "They focused on quality, programme issues and a cost management approach as opposed to a fixed price."

Haden Young won its role on the project as a tender partner of Laing O'Rourke. Another member onboard early was m&e consultant R W Gregory, who was invited to join the pre-tender team by the contractor. Cooke explains: "We developed the design together and took on all the buildability issues of a 35-m high shed, how we're going to light it, and maintain it. There is quite a complex network of gantry systems, mezzanine platforms and access ladders. All of those were built into the scheme as we've gone along so they actually look as though they should be there."

To aid the design process Laing O' Rourke brought the construction team members together in a leased office. The starting point for the design involved a visit to the existing factory and a brainstorming session with the staff. This facility uses basically the same processes and machinery but on a smaller scale.

The building is formed of two main, essentially open plan, areas – production and equipping halls – that are divided by a four-storey, ten-metre wide 'spine' that houses staff areas, offices and the plantrooms. The production hall is the larger of the two and is divided into four lanes with identical equipment in each, giving the ability to produce four pairs of wings per month.

The materials are moved through the process by a vast network of overhead cranes, which are served via a high-level busbar system. Electricity is principally supplied by a chp plant, which generates medium-temperature hot water to run the mechanical services; the heat produced is used to dry the wings after painting. The hall is ventilated by a high velocity system installed at roof level.

The lower level equipping hall – the roof here is only 23 m high – is less heavily serviced, recognising the difference in the equipment used here. One of the main activities is the testing of fuel tanks, carried out by filling with helium, sealing, then checking for leaks with sensors, before exhausting. To prevent false alarms that may be caused by a recirculating ventilation system, a static underfloor heating system involving around 60 km of pipework was used in this area.

Logistics were crucial on this project and a lot of preplanning and programming was carried out. "We had our own set of management procedures that we followed through. It sets you up, makes you talk to one another, and if you're talking to one another, you're nearly there," stresses Cooke.

Clearly this worked: after starting on site in May 2002, all high level services were complete by December. Prefabrication played a major role in this achievement and standardisation was key.

Distribution from the plantrooms is mainly via roof level gantries. The designers therefore needed a solution that was fast to build, but also easy to access for installation and maintenance.

The gantries were delivered to site as 4 m-long modules. With an aim to reduce working at heights, a fabrication area was set up beside the factory, where bracketry, cable tray and lamp fittings were installed as far as possible before the modules were lifted to the roof space and bolted together by the steelwork contractor. This meant that the m&e contractor could simply pull the cables through when the gantries were secure; even the light fittings were pre-wired so connection to the ring main was all that was required.

Waterproof bay light fittings from Holophane were used after it was determined that being able to install them outside at ground level would provide a more cost-effective solution than using cheaper fittings that had to be installed at height. "There was quite a proactive approach in terms of spending money to get the most benefit from it," stresses Cooke. It also meant that installation was considerably faster.

The bulk of the roof level ductwork and sprinkler system was completed before the building walls were in place. Cooke explains: "We've been able to deliver that on the basis that we were involved very early in the project. And we could see the only opportunity to get the services in was right at day one."

An added complication to the installation was the arrival of the wing manufacturing equipment. In order for it to be fully operational when needed, it was delivered to site when the building was under construction. To provide the protection needed and satisfy Airbus' requirements, Laing's solution was to construct a temporary structure inside the frame of the final building. This was a lightweight structure that could be quickly completed to give the heated, lit, watertight area needed for the fit-out contractors to work on the manufacturing equipment. This increased the need for close co-ordination and raised the importance of prefabricating the services to the roof trusses and gantries as the temporary structure was removed after the roof level services were completed.

The factory was officially opened on 4 July, although fit-out work in the hall continues. The first wings are now in the production process and deliveries to clients are scheduled for 2006.