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Volpe Journal Spring 98Previous Section | Contents | Next Section Aircraft Safety on the RunwayAs airports become more congested, both the National Transportation Safety Board (NTSB) and the Federal Aviation Administration (FAA) are emphasizing improving safe operations while planes are moving on the groundthat is, as they maneuver from touchdown to an assigned gate and from the time they leave the gate until they again are airborne. During these periods, pilots' visibility from the cockpit of large aircraft is limited and air traffic controllers' view of the airport often is restricted by buildings or bad weather. In support of the FAA's Runway Incursion Reduction Program (RIRP), the Volpe Center is evaluating several systems designed to prevent on-ground collisions at both the largest airports and those that are less congested. The FAA manager of the RIRP is Vincent Capezzuto; the Volpe Center's Program Manager is Tom Comparato. Fear of flying is a perfectly normal human instinct. No one can expect to survive an accident occurring several miles above the earth's surface. But not many people realize that the worst accident (in terms of lives lost) in the history of commercial aviation occurred on the ground. In March, 1977, 583 people died when two Boeing 747s collided on a runway in Tenerife, Canary Islands. Runway incursions, "any occurrence[s] at an airport involving an aircraft, vehicle, person, or object on the ground that creates a collision hazard or results in loss of separation with an aircraft taking off, intending to takeoff, landing, or intending to land," are not uncommon. During the 1990s, an average of 230 runway incursions occurred each year in the U.S., with the number increasing 25 percent between 1993 and 1995. Furthermore, during the first six months of 1996, the number of runway incursions was approximately 12 percent more than the number occurring during the first six months of 1995. Since this decade began, runway incursions resulting in serious accidents and deaths have occurred in Atlanta (January, 1990), Detroit (December, 1990), Los Angeles (February, 1991), and St. Louis (November, 1994). (View Photo: Northwest Airlines, Detroit, MI, December 3, 1990.) In response to these accidents and potential accidents, the NTSB placed runway incursion on its "Ten Most Wanted List" of safety improvements. The FAA's Strategic Plan includes reducing runway incursions as a top goal for its administrator. Although incursions by ground vehicles do occur and are a concern, this initiative's primary focus is on aircraft-to-aircraft incursions. Preventing runway incursions has been a priority since the publication of the FAA's 1991 Runway Incursion Plan. In the absence of a formal funding mechanism, however, progress has relied largely on individual initiative in the FAA to investigate ways to reduce runway incursions. About a year ago, the FAA restructured its efforts and organized a Runway Incursion Reduction Program (RIRP) team. Runway incursion prevention is planned to be a formal FAA acquisition program, with congressional line-item funding expected in fiscal year 1999. As part of the FAA's RIRP team, the Volpe Center is responsible for most of the research and development (R&D) activity. The Airport Surface Division, headed by Tom Comparato, conducts Volpe's efforts, which consist of the work of key electronic and software engineers including Ian McWilliams, Fred Hills, Frank Coyne, Steve Nuzzi, Dave Olster, Khang Nguyen, and Yen Dao. Tom Comparato considers the R&D efforts to have two primary focal points: sensors, which locate aircraft or ground vehicles on the runways and taxiways; and tracking systems, which analyze the movements of these vehicles and predict and report potential incursions before they occur. The sensing and tracking systems being evaluated differ in cost and complexity to accommodate the varying degree of traffic congestion associated with U.S. airports. (View Figure 1: Two commuter aircraft, Quincy, IL, November 11, 1996.) LOCATING GROUND TRAFFIC Under FAA guidance and as part of the RIRP, the Volpe Center is directing the ASDE-X project, which seeks a less expensive alternative to the costly ASDE-3 radar unit. Such a device would be more cost effective for less congested airports. The program includes the installation and evaluation of a number of radar alternatives, including commercial off-the-shelf systems. Two of the alternatives being evaluated are manufactured by Raytheon; one is from the Israeli company ELAR; and another is made by a French company, Dassault. The Volpe Center either purchases or leases these systems, installs them at selected airports, and evaluates and monitors how the air traffic controllers use them:
During this R&D time frame, the air traffic controllers are expected to use the ASDE-X systems as a complement to their existing systems and procedures, not as primary tools. The air traffic controllers' comments about each of the radar systems are being incorporated into the overall evaluation. The Volpe Center has published and distributed reports of functional and operational evaluations of the Raytheon ASDE-X Phase I and Phase II and Israeli ELAR surveillance systems conducted in 19961997. Installation and functional testing of the Dessault phased-array surveillance is now complete, with operator (air traffic controller) training and operational evaluation of the system to be conducted in MarchJune 1998. Evaluation of these alternative technologies for the prime sensor will provide key input to the FAA's efforts to develop a specification for acquiring low-cost surveillance systems for the less congested airports. FILLING THE GAPS As part of the RIRP, the Volpe Center has been evaluating several sensor types to determine their potential effectiveness as secondary sensors. Sensor types considered have included infrared cameras, as well as a millimeter wave radar adopted from the automotive radar developed by the Hughes Division of General Motors. The latter was designed to help prevent automobile collisions in the Intelligent Transportation System program that envisions vehicles guided along "smart" highways without driver input. Preliminary results favor a sensor system type known as ATIDS, an acronym for the rather ominously named Airport Target Identification System. In addition to providing coverage in airport areas out of the line of sight of the primary sensor, ATIDS offers a second important advantage: A group of four or five sensors not only locate an aircraft through multilateralization (directional time bearings from their known locations) but also read the plane's identity from the signal that is automatically transmitted by the transponder currently installed in most commercial aircraft. The advantage of this system is obvious. A monitor displaying information from other sensor types shows only the location of unidentified aircraft; however, one displaying information from ATIDS sensors would display not only an aircraft's location but also its identification number. ATIDS sensors, manufactured by Cardion Corporation, were installed and evaluated at the Atlanta Airport during the past year. Future evaluation of ATIDS technology will take place at the Dallas/Fort Worth Airport over the next couple of years. Although ATIDS is still in the R&D stage, the technology appears promising. (View Figure 2: Runway Incursion Reduction Program Goals.) TRACKING THE GROUND TRAFFIC AMASS is an FAA acquisition program wherein AMASS units are produced by the Norden Corporation, manufacturer of the ASDE-3 radar system. Procuring both the primary sensor and the tracking system from the same sourceat least for the initial installations in congested airportssimplifies the task of integrating the two. The FAA's strategy for congested airports is first to install the ASDE-3 primary radar, then join it with the AMASS when that tracking system is deployed. Recognizing the safety enhancement offered by AMASS, Congress has indicated that it is willing to appropriate sufficient funding to enable the FAA to install AMASS systems at all of the nation's seriously congested airports. (View Figure 3: Graph showing that the number of reported runway incursions has increased steadily.) Volpe Center engineers are teaming with the FAA staff and contractor personnel to provide oversight of Norden's efforts to develop and produce the AMASS. Meanwhile, Volpe engineers are operating an R&D version of the AMASS system in Atlanta to evaluate future enhancements and are monitoring a preproduction system that is operating at the San Francisco International Airport. Based on this work, a series of recommendations for the deployment of full-scale AMASS systems is being implemented. Site survey and installation activities are currently underway at Detroit, St. Louis, and Atlanta international airports, and the installation of all AMASS systems is scheduled to be complete in the year 2000. As each of these systems is fielded, Volpe Center engineers will receive data from each site on a daily basis, analyze it, and offer the FAA recommendations for improvements. One of the problems that Volpe Center engineers are attempting to solve is the false alarm that the AMASS often issues, caused by false images inherent in radar systems. False alarms reduce air traffic controllers' confidence in AMASS; if there are too many false alarms, the controllers might ignore the warnings. To date, AMASS has only relied on input from the primary sensor. Because secondary sensors will be added to the system, Volpe Center engineers are carefully studying how AMASS should resolve any differences in the location of an aircraft as reported by the two types of sensorsthe line-of-sight primary sensor and the triangulation of the secondary sensors. Resolving these differences, a process known as "data fusion," required the engineers to develop a sophisticated set of algorithms. The first data fusion occurred this past June in Volpe's AMASS R&D installation at the Atlanta airport and used data from the ASDE-3 primary sensor and the ATIDS secon-dary sensors installed there. For demonstration purposes, the display showed all three positions of an aircraft: one determined by the primary sensor, another by the secondary sensors, and a third by the fusion algorithm. After the fusion algorithm has been finalized, the display will show only the "fused" position. (View Figure 4: Northwest Airlines, Detroit, MI, December 3, 1990.) As part of its role in supporting the FAA on AMASS, the Volpe Center is investigating simpler, less expensive variations of AMASS that might be suitable for reducing runway incursions at less congested airports. As stated previously, the intent of the RIRP for these airports is to deploy a low-cost surveillance system that could include this lower-cost AMASS system combined with the less costly radar sensors being investigated under the ASDE-X program. The procurement for this low-cost surveillance system is currently planned for fiscal year 1999 and will be structured to offer flexibility to individual airports in terms of the capabilities each might need for surface surveillance. Also included in the RIRP, in addition to the sensor and tracking technologies, is the evaluation of various communication capabilities, or data-link, as it is sometimes called. This part of the system transfers information from one part of the system to the other, that is, sensor to tracker (AMASS) and tracker to display. Displays can be either for the air traffic controllers in the tower or for the pilots in the aircraft. For example, pilots on the ground currently rely on observations made through the comparatively small field of vision allowed by their windshields, in addition to instructions from the air traffic controller. Sending AMASS information to the cockpit will enable them to see the position of their own aircraft on the airport surface, along with the positions of all other aircraft and ground vehicles. Various communication technologies and schemes are being evaluated, such as spread spectrum, fiber optics, and local- and wide-area networks. (View Figure 5: ASDE-X tower traffic control display (snowstorm conditions).) DEMONSTRATING PROGRESS Thanks to the FAA's efforts over the past decadeand the Volpe Center's major contributions to these effortsthe possibility of an aircraft collision while planes are on the ground is being reduced greatly. Contributor: Tom Comparato |
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