Adaptability at the Gate

Adaptability at the Gate

By Grant Smith, PG

Creating adaptable terminal gates is key to the future of airports. Airlines and airports are being driven to increase efficiency and profitability, which results in fuller planes, shorter turnaround times, tighter gate space, and many ground support vehicles for onboard services accessing the aircraft at once. Gates must provide more access than ever before. At the same time, more people are moving through airports faster, so coordinating gate functions with the arrival and departure of people is critical for smooth airport operations.

The gate area functions are behind the scenes to the traveling public — things that happen on the ground around the aircraft — but they can have a tremendous passenger impact on every flight. Aircraft layout, passenger boarding bridges, preconditioned air, ground power, fueling and ground service equipment operations — all these things must be considered when evaluating whether to build a new terminal or renovate an older one.

Aircraft Layout

Aircraft layout is both an art and a science. The layout must maximize flexibility to accommodate a range of aircraft while minimizing the space required for each gate, allowing the largest number of gates at the terminal. Computer programs can help determine aircraft parking positions, but the work doesn't stop there. Experienced engineers and planners are adept at recognizing nuances in aircraft layouts that computers can't detect. For example, a computer layout tool won't necessarily identify that fueling pits or access doors may be too close together for service vehicles to safely maneuver around aircraft. Determining the optimum aircraft layout is more than a life-size jigsaw puzzle.

Passenger Boarding Bridges

The passenger boarding bridge (PBB) is one of the most critical components contributing to a gate's flexibility. Considerable differences exist in aircraft layout for regional jets versus narrow-body aircraft when using a PBB. Regional jets are lower to the ground and typically must be farther from the terminal than narrow-body aircraft, allowing them to meet the required maximum slope for boarding or deplaning passengers. The PBB maneuverability and stowage must also be considered, along with the configuration of any associated fixed walkways and their support column locations.

When deciding between a new PBB and an existing unit, it is critical to focus on maximum flexibility at the gate. Costs for new PBBs that accommodate many aircraft types can be considerably higher as well, and that can influence decisions during the aircraft layout phase for both new and modified terminals. However, the benefit of future flexibility may be worth the additional cost in this ever-changing business.

Preconditioned Air Systems

Preconditioned air (PCA) systems are the most economically and environmentally advantageous means to providing in-cabin air while an aircraft is parked. But these systems must be properly sized to accommodate the varying sizes of aircraft and the maximum ambient temperature for the location. Often there is a "builder's grade" approach to sizing PCA systems — planning for the averages. The load factors for PCA systems are based on the aircraft size and number of passengers. When selecting a PCA system, airport engineers must consider the potential minimum and maximum sizes of aircraft, as well as the cooling losses that occur while service doors are open during the aircraft turn. For example, if the gate is to service 737 aircraft, there is a big difference in the cooling needs of a 737-400 (approximately 145 passengers) and those of a 737-800 (up to 189 passengers).

Ground Power

Ground power (400 hertz) is required to run the aircraft's systems while it is parked at the gate when the engine is off. Auxiliary power units (APUs) are usually part of the aircraft system and can provide power during a turn. However, airlines are increasingly reducing APU use to save expensive jet fuel and reduce environmental emissions. Ground power — cleaner and more efficient — can be provided by a central 400 hertz distribution system or individual ground power units at each gate. In either case, the building's electrical service must be able to support the 400 hertz system or be upgraded. Point-of-use systems are typically the logical choice for terminals without an existing central system.


Fuel service at the gate is often overlooked during aircraft layout, but can be a significant cost and operational impact during construction. Fuel can be provided either from truck refuelers or through an underground hydrant system. Truck refuelers are flexible but come with inherent safety risks, availability challenges and congestion. Hydrant systems are the most efficient and safest, but present their own set of challenges when modifying existing gates. Different aircraft require varying hydrant access locations. Accommodating both narrow-body and regional jets, which are refueled under the right wing, and larger aircraft, which take on fuel under both wings, affects aircraft layout. Experienced engineers understand the nuances of locating the fuel hydrant pit properly in relation to the parked aircraft to meet the goals of a flexible gate layout.

Ground Service Equipment (GSE)

Remaining ground services provided to the aircraft, including baggage handling, food service, lavatory service, potable water, pushback equipment and maintenance, require consideration, too. Although most are mobile connections with the aircraft made by GSE, they require specific connection points and could impact gate design and planning. Accounting for convenient GSE parking and access to each gate is an important part of gate planning.

Flexibility at the gate is desirable for both the airport and airlines. The ability to have multiple aircraft configurations at one gate is often complicated and may have a higher cost for design and construction. But careful consideration and planning during the conceptual design phase, paired with an experienced engineering team, can lead to a versatile and accessible terminal layout that will last well into the future.

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