Lining up
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Posted Date: 16/06/2008
Issue: Airside International June 2008
Publication: Airside International
“A visual docking guidance system shall be provided when it is intended to indicate, by a visual aid, the precise positioning of an aircraft on an aircraft stand. The factors to be considered in evaluating the need for a visual docking guidance system are in particular: the number and type(s) of aircraft using the aircraft stand, weather conditions, space available on the apron and the precision required for manoeuvring into the parking position due to aircraft servicing installation, passenger loading bridges, etc”.
So reads part of ICAO’s Annex 14, which lays down the standards for aircraft docking guidance systems. At first sight a deceptively simple, straightforward requirement yet one that has, in practice, become increasing complex and reliant on technological innovation. This challenge has been addressed by a number of companies whose products are in increasing demand as airport construction, updating and expansion reaches record levels, particularly in Asia.
Typically, many airports featured visual docking guidance systems (VDGS) such as azimuth guidance nose in stand (AGNIS) and parallax aircraft parking aid (PAPA) boards or mirrors, the latter allowing the pilot to view the position of the nosewheel, relative to the stopping position. In practice, these only cater for the aircraft’s left-hand seat operation and require the pilot to turn his/her head to ascertain the stopping position. This is not in compliance with updated ICAO requirements. Instead developments now favour the use of advanced docking visual guidance systems (ADVGS) that provide more accurate guidance information to both pilots, such as the azimuth position of the aircraft and stopping distance. Some AVDGSs determine the aircraft type automatically and adapt the relevant guidance.
Some 40 years ago, Sweden-based, FMT was approached by airport authorities and pilot organisations, to improve the VDGSs that were available at that time. It was important to develop a system that showed unambiguous azimuth guidance and stop guidance, from a single display located in the extension of the lead-in line to the stand.
The first solution by FMT was APIS – Aircraft Parking and Information System – based on azimuth guidance by range target, featuring two bars and ground sensors which detect position of the nosewheel to provide distance to go and where to stop.
The second step in the development, patented by FMT, used Moiré (optic) technology for azimuth guidance and microwave technology for assessing distance. The third step was to use laser to replace the microwave technology and this has since become the most common standard to measure distance to go and STOP information for aircraft in the stand. This system was named APIS++ and more than 1,000 of these units have been delivered worldwide.
An important consideration when using lasers is to ensure eye safety and avoid interference to the beam by vehicles passing in front of the aircraft.
Consequently, APIS++ with its unique technology providing uninterruptible azimuth guidance, available for pilots in both left and right seat, with accuracy and reliability for long distance guidance, in combination with eye safe laser technology and central control by ATLANTIS software, is now a leading technology.
In another FMT patented technology, APIS++ may be integrated with the FMT Passenger Boarding Bridge to provide control and safety of the boarding bridge by passing coordinates to its computer, guiding it, semi-automatically, to the aircraft door.
This integration is said to be the key to safety, flexibility and speed for efficient turnaround of large aircraft. By providing integrated and automatic boarding bridge system, including over-the-wing configuration, aircraft like the A380, can be turned around within 30 minutes, using three boarding bridges, of which one is upper deck, one to the front door and one over the wing.
In the US, J & B Aviation Services, a division of Hobart Brothers Company, has developed the JB1900 gate park system, a simple to-operate, fail-safe device to control docking positions during parking. The system uses both human and mechanical components for guidance.
The automatic element comprises aircraft alignment and a fail-safe feature to stop the aircraft in case of emergency. The human input allows the handling agent to control the parking of the aircraft via a hand held controller. Because the JB1900 signal can be quickly returned to red (by release of the hand-held controller), the handling agent can alert the pilot to any emergency that would require the aircraft to come to a rapid stop.
A single JB1900 hand-held controller can manage multiple aircraft parking via a selector switch. This is particularly effective at gate positions where many types of aircraft are positioned, requiring multiple aircraft centerlines.
Based in Malmö, Sweden, Safegate International recently won its largest US contract for 92 advanced visual docking guidance systems (A-VDGS) Safedock docking guidance systems at Dallas Fort Worth. This follows on from another contract covering Beijing’s international airport that is being expanded with a new terminal, adding more than 100 gates.
During the last 30 years Safegate has developed the Safedock docking guidance system and the SafeControl airfield lighting control and monitoring system, aiming to maximise the number of aircraft an airport can handle whilst maintaining a high level of safety.
The Safedock system automatically guides an aircraft during its approach to the stand in a smooth, safe and time saving way. In 1995, the new generation of Safedock was introduced, a laser based system of which more than 1,800 have been delivered. It is considered to be a state-of-the-art A-VDGS and can safely dock all known aircraft, with a stopping precision of just 10cm.
The Type 1 is the latest member of the family. It will maintain the Safedock stopping accuracy of 10 cm whether the stopping position is two or 65 metres from the terminal. The Type 1 will dock all known and future aircraft types with the same precision, including a 73 metre long A380.
The laser scanner of the new model has a 30% longer range than earlier models, which means enhanced detection capability in rain and fog. It has also, an increased scanning rate for safer measuring and identification of aircraft. A wider scanning range gives a better apron scan, with a greater ability to detect vehicles and other obstacles before the aircraft reaches the gate. The wider scanning area also offers the possibility to include more and curved centre lines in a single system.
The manufacturer emphasises that the safety and efficiency levels of the airport are increased by the extended view of the Type 1, allowing vehicles and other obstacles to be detected and moved before the aircraft reaches the gate. Aircraft need not occupy the gates longer than necessary as the Type 1 allows a faster docking process than other systems, saving time and resources.
It is arguable that the docking process begins as soon as the aircraft vacates the runway; the lighting systems guiding the crew to the gate being a critical factor. Perhaps this was one of the reasons that the Safegate Group acquired Thorn Airfield Lighting in 2007. In these eco-sensitive times it can be acknowledged that it is possible to save emissions at the airport by efficient routing on the taxiways and fast parking at the gates. Safegate/Thorn can be a useful partnership to help achieve these environmental goals.
The gate operating system (GOS) is complementary to the Safedock system, as it minimises delays and interruptions at the gates. However, an aircraft can be redirected, at short notice, due technical problems or human error. With GOS the airport staff achieve a better overview and can monitor every event as well as carry out centralised maintenance of the docking system. Not only does the GOS information make gate allocation easier, the performance of the airport ground operations is enhanced, with gates utilised to maximum advantage.
ADB is a Siemens Company that develops and manufactures a full range of airfield ground lighting products. It produces also the innovative video docking system (VDOCKS), which became the first video-based docking system in the US, when it was installed at the Delta Air Lines hub in Boston Logan International Airport.
VDOCKS is based on video sensors and image processing that locate and track aircraft approaching the gate. It features three-dimensional object detection technology, using video cameras and image processing software. Being a video-based system, apron surveillance is an integral part of VDOCKS. Consequently, videos can also be made available to other interested users, via the airport network. It is claimed that fewer systems are required on gates with multiple centerlines, thanks to a wide-angle (120º) LED display and use of video sensors.
No motors or other critical moving parts are needed, offering high reliability and minimal maintenance. As an additional safety feature, there is an optional passenger boarding bridge interlock, ensuring that docking only starts when the bridge is properly positioned.
Aware that many docking incidents are due to badly positioned or wrongly parked equipment, a gate scanning option detects obstructions in the safety area.
Siemens stresses that VDOCKS provides pilots with precise guidance information during the docking process, especially in poor weather conditions such as snow, heavy rain, fog or low sunset. A central working position (CWP) allows interaction with multiple VDOCKS units from a central control room.
Also video-based is the visual docking guidance system (VDGS), from Honeywell Airport Systems, that guides the pilot providing continuous data, registering ONBLOCK/OFFBLOCK times and monitoring the gate area. This is achieved using a high dynamic range video sensor unit and an image processing system based on 3D aircraft models. The computer-assisted VDGS calculates information on an aircraft's location and transforms it into precise guidance information for both pilot and co-pilot. Its video sensor and 3D model-based processing system are able to recognise the outline of an approaching aircraft at distances up to 100m.
In addition to specific docking guidance instructions, the pilot display unit (PDU) can also provide information to ground crews before, during and after on blocks periods. The PDU can be integrated into the facade of a terminal gate or mounted independent of the terminal structure. An optional video surveillance component can continually monitor apron activity independent of docking procedures.
In conclusion, it should be noted that the docking procedure is not really completed until the aircraft leaves the stand, using pushback procedures. These tend to be labour intensive, heavily reliant on visual signals between ground handling members and open to risk of minor collisions if clearances, particularly wingtips, are not monitored.
CeoTronics AG, in Germany, offers the GATECOM compact wireless duplex communication system, for up to four users, in pushback operations. Using a digital open network for “hands free” communication between the tug driver and wing walkers, GATECOM enhances the safety of the operators, as well as providing communication with the aircraft flight deck. The ability to have instant information from the “wing walker” helps prevent incidents due to “lost sight”. Both Luxair and Cargolux Airlines International have adopted the system.
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