JET BRIDGES- WALKWAYS TO 35000ft
A brief insight into the engineering and economics of the Passenger Boarding Bridge
Jet bridges have long become a characteristic feature of the modern airport terminal, offering passengers and crew a short, sheltered walk in and out of an airplane.
The conception of the Passenger Boarding Bridge, as they are called in more formal circles, is credited to Frank Der Yuen, a United States aeronautical engineer, who envisioned an apparatus for the loading and unloading of passengers and cargo. The first prototype tested, the ‘Aero-Gangplank’ at the now Los Angeles Hollywood Burbank Airport commissioned for United Airlines, closely resembles the much familiar jet bridges of today.
With increasing passenger traffic over the last decade, investment in airport infrastructure has witnessed a sharp rise. Notwithstanding the economic impact from Covid, this trend is bound to recover, although this would take time. The largest buyer of jet bridges has been North America, closely followed by the Asia-Pacific region. With their zealous expansions in regional connectivity, India and China are sought to have the highest growth potential in aviation, pushing the need for better passenger boarding solutions. The Middle East follows suit with their investment-heavy airport expansion projects.
A single jet bridge unit roughly costs around 0.5 to 1 million in US dollars. The leading providers in jet bridges are the German steel giant ThyssenKrupp, the US home player JBT, the Spanish conglomerate Adelte and the Chinese competition CIMC, with many offering complete apron solutions.
Jet bridges come in many offerings. The fixed (nose loader) allowing little sweep, or the standard (apron drive) allowing larger sweep; the multi-door bridge connecting the terminal to multiple doors on the aircraft by way of separate walkways, like those equipped for servicing an Airbus A380. Then there is the less popular version of the bridge, which moves between terminal floors for boarding and deboarding.
Many buyers are leaning away from the conventional steel bridges and into more aesthetically pleasing glass bridges. This shift has been more prevalent in the US with recent relaxations on fire protection grades and safer glass bridges. Boarding was no longer a claustrophobic experience but a visually appealing one.
THE MODERN JET BRIDGE
Most jet bridges have a transition point at the face of the terminal, called a rotunda. This dome-like structure supports the bridge’s telescoping tunnels and serves to segregate passengers into separate walkways on multi-door bridges. The tunnels are also supported at the far end by the drive column consisting of a wheel bogie, which steers or advances the bridge. The landing at the end of the tunnel called the cabin opens up to the aircraft. It has a folding canopy that extends to sit on the airframe and provides near weatherproof sealing. A service stair also leads up to the cabin from the apron.
An operator’s console is provided in the cabin. The console has a joystick that allows positioning the bridge to the aircraft by conventional inputs in the vertical and horizontal direction. In addition, the console also provides limited adjustments in rotation and height of the cabin for fine alignment with the door. The actuation of these functions is achieved using hydraulics or electrical motors.
The modern jet bridge, unlike its many predecessors, is a feat of engineering. Most offer prepositioning, an automatic positioning function that brings the bridge to a programmed close distance to an aircraft by its type, leaving the operator to make the final adjustments. Newer jet bridges offer complete automation in positioning. Also, they integrate smoothly with other apron systems, such as the Visual Docking Guidance System that guides aircraft to the correct parking position at the gate without a marshal. Jet bridges may also carry comprehensive solutions such as air conditioning and external power connections for the airplane.
It also incorporates multiple safety features. The speed of the bridge is progressively reduced on approaching the aircraft regardless of stick input. An ‘auto-leveler’ lever that sits against the airframe detects aircraft movement in response to loading changes and adjusts the level of the cabin. A redundant feature to the auto-leveler is the safety shoe placed under the aircraft door during operations. Should the door contact the shoe, an alarm is raised, and the level of the cabin dropped down to prevent damage to the door. Sensors are placed in the wheel bogie to arrest its movement should it detect personnel or equipment in its way. Similar sensors are placed in the canopy end frame to detect excessive press on the airframe and relax the bridge’s forward motion.
Airports and airlines are now looking to revolutionize the boarding experience, with many collaborating on crafty media placements. Some even walk the extra mile in delivering unique sensory elements, such as native music, elegant lighting, and welcoming scents along the walkway. Well, much of the excitement around this innovative undertaking has taken a back seat owing to the need for implementing stricter health protocols in light of the pandemic.
So, are jet bridges all for the praise?
Maybe not. Jet bridges eat into parking spaces. Servicing a jumbo jet (Airbus 380/ Boeing 747) at the terminal would mean taking up the equivalent space required for two narrow body jets (Airbus A320/ Boeing 737).
The high cost of installation, maintenance, and requirement for trained personnel translates to higher landing and parking charges for airlines. Low cost carriers, wary of this, resort to using the modest mobile stairs from the golden days of aviation. The stairs allow for quicker boarding and deboarding from both front and rear exits, which most jet bridges do not cater to, at least with narrow body jets.
Jet bridges are an integral part of the premium experience. They are rightfully justified for wide body aircraft that necessitate split boarding owing to their larger passenger capacity.