Regular air travellers have become so used to walking directly from the terminal lounge onto the aircraft that the need to walk up steps instead would be almost enough to put people off flying. But, for airports, choosing passenger boarding bridges has become a major and expensive exercise.
For a start, there are several different kinds of bridge to choose from. The old fashioned b ridges, such as the T-bridge (named for its shape), are fast being overtaken by equipment such as flexible Apron Drive models.
Other types of bridges available include nose loaders, commuter bridges and those specifically designed for the jumbo A380. The A380 bridge needs to be reinforced on the wheels and lifting frame because the bridge must be higher than normal in order to meet the aircraft door; the extra height requires extra strength – but also leads to extra costs. As Grant Smith, in charge of the ramp service group at Burns & McDonnell, points out: “Everything has to be re-designed for the A380.”
Materials used in bridge construction are changing, too, from the traditional steel make-up to steel frame with glass panels. “Airports are using more glass in terminals,” says Peter Reidy, managing editor at Reidy Airport Terminal Equipment (RATE), which is the agent for CIMC Tianda in Australia and the South Pacific.
“They are driven by the aesthetic factor: it looks nicer. Now they want to extend the passenger experience to the bridge, even though glass adds an average of 5 percent to the cost.”
However, US airports wishing to use glass have an extra hurdle to overcome first. “The US National Fire Protection Association code covering glazing specifies that glazing cannot be used within 100 feet of a fuelling position,” Smith explains.
“As the bridge goes right to the aircraft, it is inevitably very close to the fuelling point. An airport can get a waiver from the local fire marshal permitting them to use glass, but some don’t want to take that responsibility.”
Many do, though. JBT AeroTech supplies numerous glass-panelled bridges to US airports. But before an airport authority even gets to the stage of choosing materials, it has to consider the design of the terminal and apron. Where a new terminal is being built, the bridge design has to be included in the initial plans. How many gates will be provided? What position are they in? What types of aircraft will be using each gate? How big and long do the bridges need to be? How do the aircraft turn in and what is their turning space?
The fuelling point has to be considered, too. For narrow-bodied aircraft, the fuelling point is normally on the right wing; for widebodies, there are two, one on each wing. The position, length and shape of the bridge cannot interfere with the fuelling process.
In some cases, an underground hydrant is used. Although often the most efficient way to re-fuel aircraft, hydrants limit the flexibility of the gate, as the position of the hydrant pits must be constructed in the most appropriate place for the aircraft types that will be serviced. If a new aircraft type is introduced, the hydrant pits may have to be moved – a difficult task, at best.
A gate has to be as flexible as possible: the more flexibility, the greater number of aircraft types can be handled and the more opportunity for airports to attract new business and accommodate airline fleet changes. An airport could, for example, provide four gates which can service narrowbodied aircraft, at least two of which can be reconfigured for use by regional jets, with two more designed for wide-bodied aircraft.
Sometimes narrow and widebodied aircraft can use the same bridge; sometimes they can’t. Often a wide-bodied aircraft is higher off the ground, with a higher door. A lower aircraft needs a longer boarding bridge to connect terminal to door – but international safety legislation restricts the slope of the bridge to less than 14 percent; the average is between 8 and 10 percent.
This means that for every 8, 10 or 14 feet in length, the bridge can only drop one foot. Any greater than that, the bridge becomes too steep for passengers to negotiate safely. Levelling devices for the portion of the floor that connects with the aircraft can enable passengers to move slowly from the aircraft to sloping bridge.
Regional jets, which are smaller and lower than, say, a B767 or an average Airbus, have to be parked further from a terminal, which has a boarding bridge linked to the upper level. Extra apron space is therefore required. Commuter jets cause even more problems. For this reason, many regional jets and all commuter jets still rely on steps for passenger access. However, at some small airports, bridges are used for regional jets, with passengers negotiating an internal ramp or a flight of stairs before accessing the bridge.
The airport environment can also affect bridges. Many new terminals are built over water, on reclaimed land. Conditions are ripe for subsidence and, if this happens, the infrastructure settles. Although it is unlikely to affect bridges themselves, it can affect the terminal buildings they serve and the utilities required on the bridge.
Some existing airports, such as New York’s La Guardia, San Francisco and Boston, have suffered from subsidence. But older terminals can cause further problems, as designers for refurbished sites have to work within the confines of existing facilities.
The airport authority needs to check the existing bridge to ascertain, first, if it is structurally sound and then whether or not it can be adapted for the new gate. If the terminal/apron layout is being re-jigged, will the existing bridge fit? If too many alterations need to be made, it will be more cost-effective to replace the bridge.
The number of bridges required per gate depends on the type of aircraft being serviced. “Airports will always have at least one bridge per gate,” emphasises Jordi Floreta, ADELTE Group’s managing director. “Usually there are two bridges per gate, so it can be used to load both doors of larger aircraft.”
Some airlines also prefer to provide a dedicated bridge and door for first-class passengers. Although airports are the prime purchasers (or lessees) of boarding bridges, airlines have a huge input – and sometimes even acquire their own bridges. Moreover, the use of a third-party supplier is growing, as airports want to outsource as many non-core functions as possible.
There are other things to consider, too. When choosing a bridge and examining the layout of gate and apron, airports cannot forget about the need to load baggage, catering supplies and so on. There has to be room for the relevant vehicles, including the fuelling tuck, to access the aircraft, regardless of the type of equipment being served or the number of bridges at the gate.
Ancillary equipment such as air conditioning and electricity also have to be taken into account. More bridges are being fitted with air conditioning units attached to the roof or undercarriage of the bridge. Some bridges – particularly older ones – cannot take the extra weight, so they must be strengthened.
Some airports are innovative in the design of their bridges. In Melbourne, Australia, the airport authority commissioned an elevated link bridge which can be moved up to departures level or down to arrivals. It takes more room and costs more, but avoids the need for two bridges. Some other airports have opted for a fixed bridge linked to multiple apron drive bridges.
“A bridge is normally 80 percent standardised, but 20 percent customised,” explains Todd Tanner, a director at JBT AeroTech. “It has a basic structure and drive mechanism, with options such as hydraulics and electromechanical systems, air conditioning and ventilation, different power and lighting configurations.”
Just one of may companies providing computerised control for bridges, JBT AeroTech’s Apron Management System controls the bridge and all its ancillaries, using diagnostics to assess the equipment, anticipate the need to repair or service it, identify the tools required for the job and estimate the length of time the job will take to complete.
Technology is also used to improve the service performance of a bridge. A central unit can be built into the bridge to automatically grease components as required, eliminating the need for an engineer to identify and access any part of the bridge needing attention.
Motors are more efficient, too, reducing the amount of electricity used and maintenance required. The average life of a well-maintained bridge is 25 years, but many airports are now replacing bridges after 15 years, as advances in technology bring so much improvement.
“Lighter materials are also being introduced,” says ADELTE’s Floreta. “These help to improve energy consumption. And, in a further desire to save on energy, solar panels are beginning to come in on bridge roofs to provide enough energy for lighting the bridge.”
Whatever will they think of next?