When the DECISION WAS made to make Malpensa International Airport Milan’s new international hub, safe and efficient surface traffic management was a priority. ENAV SpA, Italy’s air traffic services provider, was mindful of the growing problem of surface incursions and knew that the about 245,000 aircraft movements that occurred at Malpensa during its first year as an air transport hub would grow dramatically in number.
ENAV selected Alenia Marconi Systems to upgrade the airport’s surface control by installing the manufacturer’s Advanced Surface Movement Guidance and Control System (A-SMGCS). The A-SMGCS incorporates a surface movement radar (SMR) and digital open architecture capable of fusing information from various sources and presenting a clear overview of ground activity to controllers in the Malpensa tower.
Shortly after the A-SMGCS became operational, Avionics Magazine visited Malpensa and saw an airport that has seen plenty of change in just a few years.
Malpensa has been an air cargo hub serving Italy’s Lombardy region since 1948. It has two 13,000-foot parallel runways. Until 1998, it had one terminal with 10 gates.
Passenger service to Milan long has been based at Linate International Airport, which also incorporates an area control center. Linate is located 4.4 miles (7 km) from Milan’s city center but in an increasingly developed area, precluding major growth.
So, facing a capacity crunch (6 million passengers in Linate during 1999), the Societa Esercizi Aeroportuali (SEA), the airport authority for the city and province of Milan, decided to seek air traffic relief at Malpensa. In 1998 the agency opened a second terminal at the airport, providing 40 more gates. The second terminal services 51 airlines while the original terminal, which was expanded in 1994, services 82 airlines. Two years later, SEA completed a new 262-foot (80-meter) high air traffic control (ATC) tower, the tallest in Italy.
Test, Test and Test Again
Meanwhile, Alenia Marconi Systems was busy developing Malpensa’s A-SMGCS, which was commissioned Jan. 15. Each A-SMGCS subsystem was subject to three sets of tests, according to Francesco Catelli, Alenia Marconi’s project manager-air traffic management (ATM) and airport services. The subcontrator that built the system conducted the first tests, Alenia Marconi the second, and the customer, ENAV, the third.
The introduction of commercial passenger services at Milan’s new hub accelerated aircraft activity. In 1999, the number of aircraft movements at the airport grew by 140 percent over the previous year, and by 240 percent since ‘97.
The airport modernization was significant, too, as becomes apparent upon viewing Malpensa’s new tower. It has two large box-like structures, containing support rooms, attached to the pedestal. They are just above the aeronautical reporting office-meteorological (ARO-MET) room, which is shaped like a flared skirt. Atop the pedestal is the large cone-shaped cab. It houses two control rooms, one above the other. Each control room occupies 1,400 square feet (130 square meters). The control room on the lower floor is identical to the active control room above it but is used for training and as a reserve. The Malpensa tower also supports a direction room and three equipment rooms.
The tower contains 12 central processors–six serving as backup–and an additional 60 processors. All systems in the tower are connected by some 62 miles (100 km) of cable. Processed data is distributed throughout the tower via a fiber optic local area network (LAN) provided by Alcatel.
Each processor room is equipped with a "fast switch" made by Digital Equipment Corp. (now part of Compaq). Malpensa officials also call it an "intelligent switch" since it can provide a room with all incoming data but also will extract data that is appropriate for a particular function.
The SMR
Less prominent, but perhaps most unique to the Malpensa tower is the odd-shaped white structure above the cab. It houses the K-band (8,700-to-8,900-MHz) SMR with polarizer, the heart of the A-SMGCS. A look inside the white radome, made by SITI, in Como, Italy, reveals a rotating antenna that looks much like one long airfoil, or like a two-bladed helicopter rotor. The latter anology is appropriate, for at 60 revolutions per minute (rpm), the antenna actually does generate lift, relieving a bit of its normal 300-pound (135-kg) load.
The 60-rpm rotation speed, incidentally, is four times faster than the rotation rate of the nearby Alenia Marconi solid state primary radar and secondary (approach) radar with Mode A/C. Malpensa’s approach radar is one of eight such systems located throughout the Milan flight information region (FIR) of central and northern Italy.
The SMR’s rotation speed is essential, according to Catelli. "When you have fast-moving ground vehicles and aircraft making quick turns, you need to have rapid returns for the precise positioning of all surface traffic," he explains. The SMR’s pulse width is 40 nanoseconds, and its pulse repetition frequency is 5,000 to 10,000 Hz. Its range resolution is 30 feet (9 m) at 1.87 miles (3 km). The SMR was made by Galileo, a Finmeccanica company.
Upon "painting" an aircraft’s profile, the SMR can distinguish the aircraft’s size and categorize it for the controller as small, medium or large. Symbols for different size aircraft will appear on the controller’s screen.
For wind resistance, the SMR radome is shaped to appear as if the top one-fourth of the sphere has been lopped off. To reduce vibration from the high-speed rotation, the antenna structure is mounted rock-solid on a concrete base. A special insulation material absorbs 40 db of sound in the radome. Combine these features and you have an antenna structure from which the controllers just below it hear virtually no noise and feel no vibration.
The Beauty of Fusion
Also below the antenna are two cabinets, one master and one slave (for "hot" standby), for dual transmitters and receivers. The SMR system also includes a diplexer and dual data extractor controllers.
With the A-SMGCS’ prodigious processing power, the SMR signals are fused with those of the approach radar by the sensors data handling subsystem (SDHS). Composed of the surface tracking processor and the A-SMGCS central processor, the SDHS provides controllers with a seamless presentation of the aircraft taking off, landing and moving on the ground at Malpensa. An aircraft’s identity, or call sign, fed by the secondary radar, remains on the controller’s screen even when the aircraft taxis on the ground. Indeed, since en-route radar data can be transmitted from the Linate area control center, controllers in the Malpensa tower can continuously monitor an identified aircraft’s movement from its departure in, say, Rome to a gate at the terminal below.
"Soon that data will be fused with information from a VHF data link that shows the positions of ground vehicles," says Catelli. This would have data from the SDHS joined with that of the ground vehicles management subsystem. Controllers then can view on their screens the ground vehicles, which would appear as rectangles.
ENAV plans to equip ground vehicles with Global Positioning System (GPS) receivers and VHF transmitters. Initially, 50 GPS/transmitter systems are proposed: 15 for fire vehicles, 15 for law-enforcement vehicles, 15 for SEA vehicles, and five portable units for, say, the ground transport of a top government official to his aircraft. "We want to start with just 50 [systems]," says Catelli. "We don’t need to overload the controller’s screen with information."
Of course, the controller can eliminate the imagery of all ground vehicles if he chooses, or he can select a "family" of vehicles that have distinct transmitter coding. The controller then could monitor the progress of a firefighting effort or a de-icing activity.
Let There Be Light
Preset parameters in the A-SMGCS at Malpensa give controllers an alert when the separation between taxiing aircraft is less than 3 nautical miles (nm). This provides an extra margin of safety over the standard 2-nm separation. Likewise, when an aircraft crosses a taxiway to pose a potential conflict with another aircraft, the call signs representing the two aircraft begin flashing on the controller’s screen, and a red line showing the path of possible conflict appears. "We could have an audio alert, as well," says Catelli, "but the Malpensa controllers chose not to have that feature."
The data fusion doesn’t stop there, however. The system architecture at Malpensa also incorporates the visual aids management subsystem (VAMS), which controls taxiway center lights, stop bars and other ground lights. Here a rather ingenious, high-tech guidance system directs pilots as they maneuver their aircraft along Malpensa’s taxiways at night or in low-visibility conditions. Taxiway routes programmed by the controllers at their consoles will direct the A-SMGCS to automatically illuminate about 10 lights in front of a taxiing aircraft. These lights, connected by a wireless LAN developed by Israel’s Breezecom, are about 130 feet (40 m) apart on a strip of straight taxiway and 33 to 50 feet (10 to 15 meters) apart along curves. The lamps automatically turn off as the aircraft passes by them; each aircraft has its own light-illuminating sequence for guidance. If an aircraft makes a wrong turn, the controller is alerted and can redirect the aircraft by contacting the pilot and quickly establishing another taxi route.
The 100-megabits-per-second data transfer within the lighting system goes two ways. Controller data providing the illumination sequencing travels to the lights. In turn, indication of a burned-out bulb will travel to the controller.
So far, 380 lights have been programmed into the A-SMGCS at Malpensa. "There are more than 1,000 lights on the airport," says Catelli. "We hope to have the total number programmed by the end of this year."
All processed data at the Malpensa tower is recorded on magnetic tape, says the project manager. Each tape has the capacity to record information from about two days of activity. The tapes are held for one month to serve as a reference or as evidence in legal proceedings.
A Firsthand Look
It was a typical hazy spring day when Avionics Magazine visited Malpensa. Traffic was light (the Alitalia pilots were on strike). Nevertheless, several controllers were busy, managing the infrequent approaches and departures and preparing taxi routes so aircraft could skirt construction on the airfield. The controllers used paper strips on their consoles, though electronic strips are an option on the Alenia Marconi ATC system.
Sitting at a free console, I observed the new ATC system’s Windows-like environment on a 21-inch horizontal, cathode ray tube (CRT) screen made by BarcoView. I had the airfield layout, with its moving call signs and airplane symbols, occupying most of the screen. And I positioned in a corner of the screen a window that showed the entire area controlled by the tower–fanning out 32 nm from the airport. I could zoom in to view just a portion of the airfield, and I could pull up other features, such as communications windows, alarm windows, lists and tables–all part of Alenia Marconi’s advanced human-machine interface.
No question, Alenia Marconi’s A-SMGCS at Malpensa represents leading-edge technology to combat runway incursions. "Some might even consider it overkill," says Georgio Gulienetti, Alenia Marconi’s marketing director-ATM and airport systems, "because it also ensures the safe flow of traffic. And it does more than tell you that you have a problem; it identifies the problem and gives you a solution."
The system does not eliminate human error, however, as may well be the case in a recent incident at Malpensa (see sidebar).
Still, obviously impressed with the Alenia Marconi air traffic control system, Italy’s ENAV is in the process of installing similar systems at Bologna’s Guglielmo Marconi Airport and Fiumicino’s Leonardo da Vinci Airport. The systems at both airports are scheduled to be operational by the end of the year.
Plans for Malpensa call for a third runway, which would be slightly off parallel and on the opposite side of the tower from the original runways. Also, a third terminal is planned for additional cargo traffic. The construction schedule for this expansion has not been finalized.
There also are plans to have Linate area control share flight plan data with Malpensa. Joined with the en-route radar information already available, Malpensa then could assume the area control duties. This flight plan information could enhance gate planning at Malpensa but more importantly, according to Catelli, the duplicated capabilities at the two facilities bring greater safety and security. Area control responsibilities will remain at Linate, but in case of an emergency, they can be transferred to Malpensa.
Human Error and Politics
The latest technology, alone, does not ensure safety. Human error can occur, and politics can impede safe procedures. Such has been the case at Malpensa Airport.
On Aug. 13, an Air Europe B777 began rolling down one of Malpensa’s two parallel runways when its pilots suddenly saw they were heading nose-on to an Egyptair airliner. The Air Europe B777 pilot quickly aborted the takeoff. No one was injured.
How could such a potential disaster occur with Malpensa’s sophisticated surface movement radar (SMR) and Advanced Surface Movement Guidance and Control System (A-SMGCS)? The incident is still under investigation; however, reports in the Italian media indicate controller error. While this is only speculation, early news reports suggest that the Egyptair pilot misunderstood the controller’s directions and turned onto the wrong runway. Whether the controller received a verification from the Egyptair pilots has not been confirmed.
The day was clear, so the controller presumably felt he did not need to refer to the surface movement image on his screen and thus did not see the flashing warning. And he did not hear the A-SMGCS’ audio warning, since Malpensa controllers decided to forego that option. Italian authorities likely will call for enhanced controller training and a change of procedures.
Sometimes, as well, procedural guidelines and policy don’t keep pace with new technology. For example, the International Civil Aviation Organization (ICAO) has not provided comprehensive guidelines for the A-SMGCS’ use. ICAO has issued guidelines for the SMR’s use in the surveillance function but not in guidance and control functions. This has caused a political impasse at Malpensa, which has a sequencing lighting system that guides aircraft on taxiways when visibility is poor.
Italy’s ENAV, which acquired the A-SMGCS, wants to use the airport’s runway and taxiway lights for automatic guidance, but the local authority, Milan’s Societa Esercizi Aeroportuali, owns the lights and has chosen not to have them used for airplane guidance until further guidelines are established.
Human error can take many forms.