In the evolution of air transport and the necessary pursuit of efficiency in processes – such as airport safety – professionals in the aeronautics sector have been able to develop mobile boarding bridges between terminal buildings and parked aircraft.
A definition of airport boarding bridges is: mobile systems that are integrated into airport systems which allow connections between boarding gates in restricted areas of the Terminal Building and aircraft access doors.
Boarding bridges are very useful for improving efficiency and safety for boarding passengers, and for the airport operations that take place around them.
The use of boarding bridges contributes to passenger comfort by avoiding the need to walk to the aircraft or wait for shuttle busses for transportation to a remote area where the plane is parked. They make boarding and disembarking more orderly and reduce the number of ground handling personnel necessary, as well as reducing the presence of passengers on the apron, thus increasing safety and the efficiency of operation during the stopover.
But what factors must be taken into account when designing a boarding bridge?
- Type of aircraft in use both currently and in the future
- Type of terminal and its compatibility with this system
- Airport safety
- Minimum malfunctioning
- Minimum maintenance
Boarding bridges must be wide enough for two people to walk side by side. In normal conditions, the passenger flow is a round 30-55 passengers per minute.
Boarding bridges are designed with safety in mind, including extreme conditions, such as a storm. As a curiosity, the stowed position should withstand winds of up to 150 km/h and the extended position up to 90 km/h.
Furthermore, in all cases, boarding bridges are equipped with regulatory lighting for perfect visibility in any conditions the airport could be operating in.
There are two types of boarding bridges:
Telescopic boarding bridges are the most versatile for connecting to all types of aircraft.
Their length depends on the height of the Terminal Building and the lowest height of the aircraft door. Sometimes the height of the building is corrected using a stationary gate that connects the Terminal-Boarding Bridge via stairs or a ramp. The length is adjusted to prevent slopes greater than +5% and less than -10% when connecting the aircraft and the terminal.
Stationary boarding bridges are similar to telescopic bridges, but with more limitations. They only have one vertical rotating axis and a platform that joins the aircraft without angular movement capabilities.
What are the elements of a boarding bridge?
- Rotating hinge:
This is the part of a mobile boarding bridge with a fixed walkway providing access to the terminal. It consists of a rotating platform resting on a large hinge. The rotary part is joined to the moving part that can rotate vertically and horizontally to connect with the aircraft.
- Telescopic walkway:
This is made up of two stretches of metallic bridge, one is stationary and the other extendible. The interiors are made of lightweight metal. The floor is covered with non-slip material to make it easy for passengers to walk up and down. Materials must also be corrosion-resistant.
This bridge has an adjoining staircase on the right side of the movable bridge to allow access to and from the aircraft to the apron. This is for use only by ground handling personnel.
The useable width of the walkway for passengers is minimum 1.6 meters.
Where the stationary and telescopic bridges connect, there is a ramp to avoid a step between the two.
In terms of accessibility various measures must be taken in every case, for example, there must be a handrail on the right side of the walkway and the entire walkway must be sufficiently well lit.
- Platform connection to the aircraft (bridgehead)
This is a rotating platform joined to the telescopic stretch of the bridge to connect with the aircraft door.
The bridgehead is built entirely from lightweight, corrosion-resistant metals.
It must have a rotating disk that creates a seamless connection with the floor of the aircraft door in the event that the aircraft and the gangway are not perfectly perpendicular. At the end of the rotating disk there is a rubber protector to prevent even the slightest damage to the aircraft fuselage.
The control panel is located in this part of the bridge.
The exterior part of the platform opening is flexible allowing a precise fit with the walls of different aircraft. The head has lighting for night-time connections.
- Elevation/ascent system
This is carried out using hydraulic cylinders mounted on a gantry which serves as a guide.
The cylinders are driven by a two-flow hydraulic pump, which also drives the cylinders behind the telescopic movement. These cylinders are designed to withstand the necessary loads for long periods of time without changing position. The lifting speed is around 0.7 m/min.
The lifting movement is controlled either manually using controls or automatically using a levelling mechanism.
- Extension/retraction system
The function of this element is to provide support, rotate the wheels and raise the telescopic bridge. The impeller is made entirely of steel. Both this and the bridge are usually driven by electro-hydraulics that consist of an electric motor driving a pump that feeds the drive motors built into the wheels and support cylinders.
The impeller usually has two twin non-pneumatic wheels. The impeller controls the hydraulic lifting power of the bridge on a pair of rams located on both sides of the bridge and supported by a rotation axis that makes it possible to automatically correct the angles that describe the moving bridge for adapting to the different heights of aircraft doors.
The drives for the hydraulic wheels must be built independently on each side. In this way, should one unit fail, it is possible to operate with the other, at half capacity.
- Rotation system
This is composed of a self-propelled trolley. The drive is carried out on two driving wheels. The trolley serves as the supporting base for the vertical movement guiding gantry.
- Electrical safety elements
To move the gangway in any way requires a manual “dead man” style switch. This is a switch that stops movement as soon as the operator stops pressing it.
This switch has an extendable cable that allows the operator to move around to check movements and ensure a perfect connection with the aircraft.
On both sides of the connection platform’s rubber protection there are usually antenna micro-switches which, when activated, immediately stop the movements of the bridge.
To the right side of the connection platform, there is a levelling mechanism that consists of a wheel that makes contact with the aircraft. If for any reason the wheel does not make contact with the aircraft body, an alarm is activated.
The boarding bridges are systems that are very useful and safe for passengers. As architectural elements, there are different models with different finishing according to the style of each individual terminal building.
The evolution of boarding bridges is linked to the evolution of aircraft. Just as three-armed boarding bridges were once created for the A380, it is possible that we will see novel designs in the future if new aircraft arrive on the scene, such as the Flying V or the AIRBUS Maveric. Time will tell.