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Monday, October 1, 2001

Memphis: The Future of Surface Management

Multilateration, data fusion, ground-vehicle tracking–they are all part of an effort to prevent runway incursions and improve traffic throughput at this busy air cargo hub in southwest Tennessee.

Charlotte Adams

In the battle to improve traffic flow and prevent runway incursions, Memphis International Airport has become the front line. The engagement there involves both state-of-the-art ground-management equipment and procedures tailored to use the equipment as effectively as possible.

Memphis International, a test site for new surface management technologies, provides a window into the development of tomorrow’s procedures. "We’re in a prototyping and R&D environment," says Bill Wertz, the Federal Aviation Administration’s (FAA’s) Tennessee hub manager and the facility manager for the Memphis airport.

"Our job in operations is to use [technology]," says Stephen Vail, senior manager for air traffic operations with cargo carrier, FedEx Express. FAA and the airlines have sketched a concept of operations (CONOPS), a broad-based outline of airport surface management, he says. But individual airports need to develop local procedures to supplement the CONOPS. "We want to be the first site with an integrated airport management system," he adds.

FedEx’s ‘Maintenance Display’

FedEx already uses new surface management technologies. Memphis International Airport, the carrier’s home base, is a key site for FAA’s Safe Flight 21 program, which focuses on the improvement of ground as well as air operations. The FedEx ramp tower already features both a multilateration display and a developmental, fused-information display with additional data feeds from FAA’s Volpe National Transportation Systems Center. FAA controllers can view similar displays in a trailer parked alongside the air traffic control (ATC) tower, but development has not advanced to the point where the equipment can be installed in the ATC cab.

FedEx’s multilateration display–a "maintenance display" from Sensis Corp.–presents aircraft as moving digital icons. The information is based on multilateration sensors, which triangulate a target’s position from transponder signals. The display also correlates targets with call signs derived from flight plan information. The Volpe display, on the other hand, fuses multilateration information with live target data from the Airport Surface Detection Equipment-3 (ASDE-3) radar and airport surveillance radar (ASR), together with flight-plan call-sign information from the Automatic Radar Tracking System (ARTS) and Automatic Dependent Surveillance-Broadcast (ADS-B) data.

Ground operations improvement "starts out with metrics like time-to-gate," says Donald Barber, FedEx’s senior vice president for air operations. "With the kinds of tools we have demonstrated, combined with arrival and departure information, it becomes possible to orchestrate the entire surface movement scenario with complete and accurate information," he says. "It’s not a radio report. You know precisely where everybody is."

FedEx wants to wring any inefficiencies latent in existing systems out of its ground operation. The company’s contract to carry mail for the U.S. Postal Service (USPS) is expected to double the number of FedEx’s afternoon flights six days a week–from 40 to 75 in and out. The carrier already moves 150 aircraft in and out during its night shift. FedEx also is moving from narrowbody to widebody aircraft, putting ground productivity at a premium.

Memphis International now uses the 1980s-vintage ASDE-3 radar, whose monochromatic display overlays live-target video on an airport schematic. With this technology, however, it is impossible to know the order of airplanes lining up in inbound and outbound queues until they individually radio in their positions. These limitations can add minutes to flight turnaround times.

Tracking Ground Vehicles

Sensis, under an FAA contract, has installed nine ground stations, handling multilateration and other functions, around the Memphis airport. Memphis is the first airport to have multilateration sensors placed throughout the airport area. Five more of the compact refrigerator-sized units may be placed on the approach corridors away from the airport to support other applications, Vail says.

Vehicles fitted with emitters also can be located using multilateration or Global Positioning System (GPS) receivers. FAA in June 2001 requested information on cooperative vehicle tracking technologies. The agency wants to install and test a vehicle tracking system or systems at Memphis. FAA is interested in tracking vehicles on the airport surface movement area, not on apron or ramp areas. FAA received 37 preliminary responses.

Vehicles also can be labeled. "Three to five years from now, we’ll see information on runway and taxiway ground vehicles showing up on air traffic controllers’ displays," predicts Todd Donovan, Sensis marketing manager. There are many ways to label vehicles. One way would be a vehicle transmitter, which could periodically emit an identification code on Mode S transponder frequencies. These codes then could be associated, in the fusion processor, with classes of vehicles or individual vehicles. Designers, additionally, could embed a message in an emitter data field to add further information. Before technology moves to this point, however, developers need to resolve issues such as the number of available transponder addresses that can be used for vehicle IDs and the implications of address reuse on equipment like the traffic alert and collision avoidance system (TCAS).

FedEx is experimenting to see how the new technologies can increase throughput and efficiency. Vail hopes to better predict flight gate arrival time, for example. Pilot estimates of gate arrival times now can be 10 to 20 minutes off. But the carrier wants to get within four minutes of the target time. FedEx has "developed the means [for gate arrival-time prediction], and we are in the process of validating that means," Vail says.

Without the fused information, the FedEx ramp tower does not know the order in which FedEx aircraft are going to get to their entry spots on the FedEx ramp until individual pilots make contact, Wertz explains. Similarly, the ATC tower doesn’t know who is pushing back from the gate and preparing to taxi until the pilots call in.

Benefits of Fusion

But with the fused information, before incoming aircraft call the ramp tower, the ramp "will actually see on a display the order in which those aircraft are taxiing down the taxiway," Wertz says. FedEx can "even do gate reassignments with this better information, which will allow them to increase the productivity of their work force." FedEx hopes to increase ground support productivity by 5 to 10 percent with new systems and procedures, Vail says.

At this time FedEx is focusing more on outbound efficiencies because there is "such a concentrated outbound launch [and] the outbound window is much shorter than the inbound window," Vail explains. "By having all the surface information, we won’t have to have such a static plan outbound," he says. "If we have situational awareness, we’ll be able to adjust to the real-time situation and dynamically plan our launch each night."

Dynamic planning means the ability to get priority flights out ahead of other flights, to know how many pushes are going on at one time, to work collaboratively with the control tower, and "to capture all the runway capacity," Vail says. Active use of multilateration and common situational displays will help tower and ramp develop a set of procedures based on mutual expectations, he adds.

Under the current system, a carrier knows wheels-down time and gate arrival time through the Aircraft Communications Addressing and Reporting System (ACARS) system. But, if a problem exists with a particular aircraft’s taxi time, "They don’t know what happened between [touchdown and gate]," Wertz explains. Fused information, however, can be recorded, archived, and replayed to identify the problem. FedEx has used playbacks to critique its ramp controllers, but the carrier does not yet have the ability to get that information every night, Vail says.

Currently, the control tower first finds out which airplane wants to taxi out for takeoff when the FedEx pilot calls and asks FAA controllers for a ramp departure spot. But with fused information, the ATC tower "can put four or five 727s in trail of each other on one runway" and, in good weather, clear them one after another when each gets 6,000 feet down the runway and airborne, Wertz says.

"With the advanced information of who’s ready, we can pick and choose who will taxi next," he adds. "If we can establish queues at the runway with the best types of lineups, we can save FedEx a lot of money and taxi time."

FedEx and the airport authority also plan to test the multilateration system. They want to determine whether there are areas in which surface vehicles cannot be seen by the new sensor system, Vail says. Vehicles on the taxiways and runways will be readily visible, but crew buses, airline catering trucks and utility vehicles parking in nooks and crannies under the corners of buildings or under jetways may not be. Once these areas are identified, something could be put in vehicles to warn drivers that they can’t be seen, Vail says. FedEx already has GPS on some crew buses and is thinking about feeding that information into the tracking system, as well, he adds. For business reasons, carriers "may want to track a lot more than emergency vehicles," he says.

Head-Up Surface Guidance System Prepares for Live Demo

Controller equipment is by no means the whole story for surface operations management. Airlines are busy planning, evaluating and buying cockpit displays to gain the best perspective on and guidance for clogged runways and taxiways. Rockwell Collins Flight Dynamics and its team members have designed a high-end system displaying surface guidance information on Collins’ existing Head-up Guidance System (HGS).

The fruits of their labor will debut in a taxi demonstration this month (October), says Peter Howells, Flight Dynamics’ systems engineering manager. The Surface Guidance System (SGS)–envisioned as an extension to the HGS–will heighten pilot situational awareness in low-visibility conditions on high-speed rollout, high-speed turnoff and taxi, Collins says. Project leader, Collins, supplies its HGS, Smiths provides the flight management system (FMS), and Jeppesen adds the database of surveyed airport runways.

If all goes as planned, the SGS, now in engineering development, will be available in 2003. The initial version will integrate enhanced positioning via the Federal Aviation Administration’s (FAA’s) Local Area Augmentation System (LAAS), centerline guidance based on runway surveys, speed awareness, and the display of hold positions, signage and runway edges, Howells says. Subsequent upgrades probably will include Automatic Dependent Surveillance-Broadcast (ADS-B) inputs for surface traffic following and enhanced vision features such as a look-ahead infrared (IR) sensor for use on taxiways.

Head-up surface guidance functions will be worth the price, Collins claims, as airlines will save $60,000 to $120,000 per aircraft, per year. "It will reduce average taxi time up to two minutes in poor visibility," Howells predicts.

The original HUD provides critical flight information for low-visibility approach, landing, rollout and takeoff. Data includes altitude, attitude, airspeed, navigation, mode annunciation and glide slope. Used by Delta Air Lines, Southwest and Alaska–and standard on the Boeing Business Jet (BBJ)–HGS boasts more than 7 million flight hours, with about 1,000 systems in service.

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