Docking guidance systems have come a long way since the days when aircraft wheels passing over pneumatic hoses and inductive loops in the apron gave a signal to a display that lit a lamp. Radar-based systems followed and in the 1990s laser-based docking technology took the lead; it remains at the forefront today. While marshallers may still wave their wands, increasing volumes of traffic at modern airports call for ever-more sophisticated and precise docking technology
Visual Docking Guidance Systems (VDGS) or Nose-In Docking Guidance Systems/Stand Entry Guidance Systems (SEG) – such as the Parallax Aircraft Parking Aid (PAPA), which tells flight crews when/where to stop – are among the most popular forms of stand guidance. Azimuth Guidance for Nose-in Stands (AGNIS) guidance systems, often combined with PAPA, consist of two lights side by side. If the pilot is on the stand centreline, he will see two green lights; if he is off the centreline, one of the lights will appear red and the pilot will steer towards the green one.
Both systems have their limitations, however. AGNIS VDGS is cheap to implement and reliable, but relatively imprecise, while PAPA relies on the position of the viewer and will not give accurate distance information to aircraft that have deviated significantly from the stand centreline.
Consequently, more and more airports are adopting Advanced Visual Docking Guidance Systems (A-VDGS), with electronic displays performing the functions of an AGNIS/PAPA installation with greater accuracy. FMT Aircraft Gate Support Systems AB, based in Trelleborg, Sweden, developed its first radar-based systems known as APIS in 1989.
Initial systems were installed at Sydney and Copenhagen airports; however, frequency and interference problems led to a laser-based alternative, which launched in Sydney. “This first laser-based docking system entered the market in 1992 and it’s still the leading technology for docking today,” says Joachim Brink, sales and marketing manager at FMT. “We are also the only ones using independent azimuth guidance.”
The latter system tells the pilot whether he should turn right or left, while the laser gives distance measurements and stopping information. “It’s a very straightforward technology,” Brink points out. “The laser is high-performance; it scans 10 times per second, and we can collate and analyse a lot of measurements in order to provide a very high level of accuracy. Azimuth guidance is independent of the laser and this is really important because the pilot needs this information as early as possible. We can give him it before he is on the lead-in line, before the laser has spotted the aircraft.”
APIS++ can also be equipped with traffic lights in order to make the stopping information even easier to understand. In addition, the traffic lights can be operated manually as a fall-back procedure.
The system can operate ‘stand-alone’ or be integrated with the airport’s central database through an open interface. When interfaced, APIS++ can be automatically activated. APIS++ is always integrated with the passenger boarding bridge (PBB) to provide safety interlock functions. FMT can also offer automatic or semi-automatic docking by co-ordination between the PBB and APIS++. After block on, APIS++ gives information for automatic adjustment of the PBB’s position and for connection of it to the aircraft.
When interfaced with the airport’s central database, APIS++ receives information such as aircraft type and series, flight number, etc, and submits information such as block on time and stopping position back to the central system.
When FMT’s central stand management system, Atlantis, is installed, interface can be established with any airport system to allow comprehensive control of all different IT systems at the airport. For example, Atlantis could be used to control stand allocation, ground support equipment, billing systems, apron lighting, CCTV and so on.
FMT’s Airpark is a guidance system featuring traffic lights and azimuth guidance, but not laser, and is operated manually by a marshaller. It can be interfaced with other airport systems and the PBB, so that the safety interlock function ensures that the bridge will not move before the aircraft is properly docked. A signal to the PBB confirms that the aircraft is parked correctly and that the connection can be made.
Stephen Driscoll, group operations director at Jersey airport, chose APIS++ VDGS, saying: “Our technicians found the system very satisfactory and resilient, as have the users, as it gives reliability and the accuracy they need. The units are programmed with all the aircraft that visit us and these are displayed and easily accessed, so the
system is very simple to operate.”
He adds with hindsight that the networked system option would have been preferable, allowing integration with the stand allocation; nevertheless, “cost, service and durability” influenced choice of this “good, sturdy system”.
Integrating functions
Fredrik Johansson, product leader for Safedock A-VDGS at its manufacturer, Sweden-based Safegate International, cites safety, efficiency and reducing carbon emissions as core functions of his company’s docking system. Safedock is based on laser technology that scans the apron and gate area for obstacles, creating a three-dimensional image that facilitates security checks and safe and correct docking. Safedock’s high-performance laser range finder and LED display guide pilots to within 10cm plus/minus of the ‘stop’ position. “The fact that we have a three-dimensional scanner, which some of our competitors do not, makes us look to more than just the centre-line and where aircraft are expected to be,” explains Johansson.
“We look at the complete gate or the apron area instead of just the aircraft nose and docking area,” he continues. The automated docking sequence meanwhile limits emissions, operational costs, time at the gate and resources.
Safedock A-VDGS Type 1 is the most advanced of the three types, giving the longest range of stop positions and greater accuracy and superior performance on long and short distances. A new, lateral scanner will deliver a broader and longer view of the gate and help to detect small or distant objects.
Safecontrol-Apron Management (SAM), formerly Gate Operating System (GOS), networks all airfield systems (such as stand management tools) to provide real-time gate status and monitoring, minimising disruption here and improving ramp safety. SAM involves visual guidance of each aircraft to ensure that it gets to the right gate as well as central monitoring of the docking process, giving an overview of airport stand status and smoothing docking operations.
Johansson has a broader perspective of the function of the gate docking system: “It is becoming increasingly important and popular to use the docking system as a message board to show information to the ground crew or the pilot, related to the turnaround process of flights arriving and departing.” Such data can range from timetabling to bag numbers to be loaded onto aircraft. “Increasing numbers of airports are looking to utilise our Safedock system for more than just docking aircraft,” he adds.
Future streamlining activities in the gate area, for example, could involve integrating Safedock with the lighting system from 10 miles out to the ‘stop’ of the gate.
Minimising tarmac delays and fuel costs were the original business goals of American Airlines (AA) in choosing Safedock. According to Pilar Geist, IT senior manager, operations technology and realtime systems at the carrier, the main benefit has been the “capability to park aircraft without waiting for ramp crews. This has a positive impact on customer service since we enable passengers to deplane when a ramp is closed due to weather conditions. It also reduces fuel costs.”
At London’s Gatwick airport, airfield duty manager Glen Lindup describes Safedock A-VDGS as very easy to operate and flexible around upgrades and programming. He regards the system as “extremely reliable and we haven’t seen any major failures in terms of maintenance, with spares utilisation being low”. Gatwick Airport Limited (GAL) is working to network its entire raft of 141 Safedock systems.
GAL, in conjunction with Mirror Technology, is meanwhile pursuing the tactic of precision parking of aircraft using mirrors. Nose-loaders move in and out or up and down; hence, aircraft need to be positioned correctly and must stop at an exact point every time, with the nose-wheel stopping on a painted mark on the ground as viewed through a mirror.
Other systems have a tolerance of 20-60cm, which can be significant when trying to align an aircraft door with the bridge. Pilots also require different seating positions, while there is a reaction time regarding visual reference for stopping and applying brakes. For a small aircraft, this can be 20cm but for a B747, it can be 60cm. The system does not apply to larger aircraft types, but works well for smaller aircraft such as the B737.
The human factor
In the USA, Hobart Ground Systems’ J&B Aviation has developed the JB1900 Gate Park System, with both human (ground handling agent) and mechanical components guiding aircraft on a taxi-line into docking position, informs Ann Roberts, the company’s marketing manager. The system gives guidance on both the lateral position and forward motion of the aircraft.
The JB1900 signal can be turned quickly to red, allowing the ground handling agent to alert the pilot in an emergency. In mechanical terms, the JB1900 comprises aircraft alignment and a fail-safe feature to stop the aircraft; the human aspect allows the handling agent to control aircraft parking while visually observing critical ramp operations to ensure there is no debris in the envelope area.
A single, JB1900 hand-held controller can manage multiple parking devices via a selector switch. The ground-handling agent can easily designate a parking device by switching from a to b, for example, which is particularly effective at gate positions where different types of aircraft are positioned, requiring multiple centrelines. Each Gate Park System can be set at a different height to accommodate different aircraft, from a 737 to a 757, for example.
“The JB1900 Gate Park System is extremely cost-effective as compared to other laser solutions on the market,” Roberts considers. It also uses energy-efficient and highly luminous LED lights rather than standard bulbs. The system is installed at most major US airports, including recently at 29 gates at JFK International Airport.
The J&B Aviation Gate Park System, often referred to as an ‘Aircraft Docking System’ is used exclusively at Atlanta’s Hartsfield-Jackson new International Terminal as well as at the rest of the gateway.
Docking Guidance Systems may be focused on safety on the ramp; however, the advance of technology is expanding the potential of such systems to encompass the turnaround process of aircraft arriving and departing, and the information beneficial to people involved in that process. As to the broader picture, Safegate’s Johansson believes that “we’ll start thinking more and more about efficiency, safety and giving value to customers, and about the complete airport, with greater integration between the systems.”
