Runway Incursion Studies in NASA'S FutureFlight Central

In recent years the Federal Aviation Administration (FAA) has made reduction of runway incursions a priority for surface operations throughout the national airspace system. In a series of experiments conducted in April 2001, NASA studied alternatives designed to improve the efficient movement of surface traffic and reduce runway incursions at Los Angeles International Airport (LAX). The experiments were conducted in NASA Ames Research Center’s FutureFlight Central (FFC), a full virtual reality air traffic control tower cab simulator. This paper details the lifecycle of the safety studies from design to execution, describes the alternatives that were proposed for runway incursion reduction, and offers a brief summary of the experiment results. Nomenclature http://ffc.arc.nasa.gov/about_us/technical_papers/runway.html (1 of 17) [6/5/2003 11:41:58 AM] Runway Incursion Studies in NASA'S FutureFlight Central AAR Airport Arrival Rate ASDE-X Airport Surface Detection Equipment Next Generation Version X ATC Air Traffic Control ATIS Automated Terminal Information System ATSP Air Traffic Service Provider D-BRITE Digital Bright Radar Indicator Tower Equipment FFC FutureFlight Central LAWA Los Angeles World Airports NAS National Airspace System NATCA National Air Traffic Controllers Association STA Scheduled Time of Arrival TRACON Terminal Radar Approach Control TMC Traffic Management Coordinator Introduction In 2001 the FAA Office of Runway Safety released a report summarizing the number and severity of runway incursion events at towered airports in the United States between 1997 and 2000. According to the report, the national airspace system managed approximately 266 million flights over that period, 1,369 of which resulted in a runway incursion, approximately five incursions for every 1 million operations. The number of incursions increased by 110 events the following year.[1] The FAA and the Los Angeles World Airports (LAWA), operator of LAX, commissioned a series of studies in NASA’s FutureFlight Central tower cab simulator in 2001 to explore alternatives designed to reduce runway incursions at LAX, which is the nation’s fourth busiest airport. While air traffic demand for LAX has increased over the past ten years, there has been no corresponding increase in airfield capacity. Numerous changes to airborne and on-ground operating procedures, runway and taxiway markings, and airport lighting have been implemented to better manage traffic flow. Despite these efforts LAX reported 19 runway incursions in 2000, with “deviations from FAA clearances” the second most frequently violated regulation (c.f. FAR 91.123(a) recognized as a major contributing factor.[1] The goal of the two-phase FFC study was to elicit feedback from LAX controllers on six proposed runway incursion reduction alternatives. Working closely with LAWA personnel, LAX controllers, and representatives from United Airlines, FFC engineers recreated LAX for the experiments, not only the out-the-window view of the airfield from the tower, but also traffic flow scenarios that mimic the airport's day-to-day operations, both on the surface and in the terminal area. http://ffc.arc.nasa.gov/about_us/technical_papers/runway.html (2 of 17) [6/5/2003 11:41:58 AM] Runway Incursion Studies in NASA'S FutureFlight Central This paper follows the development lifecycle and execution of the two LAX experiments. The authors will provide an abbreviated summary of experiment results; a comprehensive summary may be found under separate documentation.[2] A brief introduction to the FutureFlight Central facility is provided for clarity. Overview of FutureFlight Central Located at the NASA Ames Research Center, Moffett Field, California, FutureFlight Central uses twelve rear-projection screens and computer generated imagery to create a 360-degree “out-thewindow” representation of an airfield and its environs as seen from the tower cab. FFC’s image generator is an SGI, Incorporated Onyx 2 Reality Monster computer configured with six graphics engines and 16 processors that provide a nominal 30Hz update rate. FFC’s lower floor Operations Center is comprised of three main areas: the Pseudo-pilot Room, Test Engineer Room, and the Operations/Ramp Control Room. The Pseudo-Pilot Room hosts thirteen pilot stations, each with a 2-D map display of the airport surface on a 21-inch, color high-resolution monitor. This display is the pilot’s interface to the aircraft in his or her area of responsibility; from here, the pilot controls aircraft speed, heading, taxi routing, gate operation (push-back, taxi-in), runway operation, departure profile, and arrival routing, among other parameters. A flight may be moved to any position on the airport surface that has been defined for the operation, and fine adjustments to the aircraft position are possible. A pilot is able, for example, to comply with a controller’s direction to exit the runway at a given high-speed taxiway, taxi forward for maximum spacing, and hold short of the active parallel. The pilot communicates with tower and/or ramp controllers via voice communications system (VCS) located at the station. The VCS emulates standard radio communication; each pseudopilot has the ability to transmit and receive on appropriate frequencies (ramp, ground, local, departure) as the flight progresses through the area of positive control. Frequency values match those of the airport that is currently being simulated. The Test Engineer's Room is the control center for all of the facility’s audio/visual and simulation systems, and the facility’s data collection and reduction equipment is located here as well. The Test Engineer is connected via VCS to all other participants in the simulation, and is responsible for starting and stopping the simulation software. Next to the Test Engineer’s Room is the Operations/Ramp Control Room, which can be configured to simulate an airline ramp control operations center. The upper floor of the FFC facility accommodates the projection display system and the air traffic control tower cab. The tower cab is modular and can be configured to match the layout of the airport tower being simulated. Recessed into the perimeter console are 16-inch, flat panel touch screens on which radar equipment, wind indicators, clocks, and altimeters are simulated. Flight progress strips and container banks are provided, along with Digital Bright Radar Indicator Tower http://ffc.arc.nasa.gov/about_us/technical_papers/runway.html (3 of 17) [6/5/2003 11:41:58 AM] Runway Incursion Studies in NASA'S FutureFlight Central Equipment (D-BRITE) monitors, and multiple VCS plug panels at each station. Figure 1 is a view of the inside of the FFC tower cab. Figure 1: The FFC Tower Cab Recreating LAX in the FFC Tower As mentioned above, the FFC tower cab provides a 360-degree representation of an airfield as seen from any eye-point; for the purposes of the LAX experiments, the eye-point was located at the center of the air traffic control tower cab. The 3D model of the out-the-window view was based on computer aided design (CAD) drawings provided by the LAX airport engineering department, and overlaid with high-resolution aerial photographs to provide a high-fidelity representation of the airfield as viewed from the tower. Figure 2, below, is a comparison of actual and simulated views from the LAX tower. Horizon features (buildings, freeways, etc.) were modeled for realism and visual orientation. Although air traffic associated with the Los Angeles basin’s other airports is often visible from the LAX tower, no overflights were simulated. Ground vehicle traffic movement was not simulated, with the exception of aircraft tugs for pushback operations. Refer to Figure 3 for an LAX airport diagram, including typical arrival/departure traffic flow markers. http://ffc.arc.nasa.gov/about_us/technical_papers/runway.html (4 of 17) [6/5/2003 11:41:58 AM] Runway Incursion Studies in NASA'S FutureFlight Central Controller Staffing and Responsibilities in the FFC Tower In preparation for the LAX experiments, FFC engineers visited the airport to study the layout of LAX’s control tower and record information about controller staffing, the type and positions of various tower tools, and the physical placement of controller positions relative to the out-thewindow view of the airfield. Observations about airport demand, traffic flow and surface congestion points were used to determine pseudo-pilot staffing requirements and responsibilities for the tests. http://ffc.arc.nasa.gov/about_us/technical_papers/runway.html (5 of 17) [6/5/2003 11:41:58 AM] Runway Incursion Studies in NASA'S FutureFlight Central Normal staffing for the LAX tower includes three local controllers (Local One, Two, and Three), three ground controllers (Ground One, Two, and Three), a clearance delivery specialist, and a Traffic Management Coordinator (TMC). Only the Local and Ground positions were staffed for the LAX experiments. Five full performance level controllers currently on staff at LAX attended the experiments to rotate through the tower positions for the tests. Refer to Figure 4 for a diagram of controller positions in the virtual tower. http://ffc.arc.nasa.gov/about_us/technical_papers/runway.html (6 of 17) [6/5/2003 11:41:58 AM] Runway Incursion Studies in NASA'S FutureFlight Central Figure 4: Controller Positions in the Virtual Tower FFC Personnel Training and Staffing In addition to the five LAX controllers, 20 people were needed to staff each experiment run, including 17 pseudo-pilots, one test engineer, and two pseudo-pilot coordinators. Of particular importance to the successful execution of the experiment scenarios was training the pseudopilots to become comfortable with the controllers’ rapid speech delivery and shorthand clearances. Having LAX controllers attend dry run sessions before the actual experiment dates was helpful in this regard. Pseudo-pilots communicated with controllers on LAX frequencies using standard ATC phraseology. In addition to this standard phraseology, controllers were able to issue the “shorthand” taxi clearances which they have developed with the airlines at LAX. The pseudopilots had been trained, for example, to recognize clearances involving the “Bridge Route,” or the “North Route,” thus eliminating the need for lengthy taxi instructions and alleviating frequency congestion. Pseudo-pilots were also instructed to advise possession of current ATIS information on initial contact with controllers. Scenario Design Key to the success of the experiments was the design of realistic and challenging traffic scenarios which presented controllers with problems identical to those they solve on a daily basis at LAX: runway crossing restrictions, wake turbulence delays, heavy taxi-in/taxi-out delays, long departure queues, and the like. With these considerations in mind the FFC engineers designed two 45-minute traffic scenarios: http://ffc.arc.nasa.gov/about_us/technical_papers/runway.html (7 of 17) [6/5/2003 11:41:58 AM] Runway Incursion Studies in NASA'S FutureFlight Central ● Peak Arrivals: 92 arrivals/78 departures originating either in the departure queue, airline gate, alleyway, or in flight ● Peak Departures: 62 arrivals/107 departures originating either in the departure queue, airline gate, alleyway, or in flight Each of the alternatives was tested under both conditions. The mix of traffic included flights from American, Southwest, United, Delta, Qantas, Hawaiian and SkyWest air carriers; a total of 22 airlines was represented. FFC visual database engineers provided liveries and aircraft type models appropriate to each airline’s fleet. Gate assignments were determined with the help of airline consultants and through observations made by FFC engineers during site visits to LAX. The intent of these observations was to identify allowable gate assignments based on airline and aircraft type information and to provide a comprehensive, realistic gate assignment rationale for the airport. All parties agreed not to simulate ramp control, ground vehicle traffic, and maintenance tows for the experiments. Although this decision reduced the complexity of the airport simulation, the parties agreed to narrow the experiment focus to safety and operations in the airport movement areas only. Experiment Phase 1 Purpose and Key Findings The purpose of the Phase 1 experiments was to validate the LAX recreation and to elicit controller feedback as to the efficacy of the Peak Arrival and Peak Departure traffic scenarios. The results of the Phase 1 evaluations were to have a direct bearing on preparations for the Phase 2 tests. Results of the Phase 1 tests revealed that the LAX controllers found the FFC simulation to be an accurate recreation of their airport environment, taking into consideration the simulation constraints and modifications agreed upon by the participants. Specific feedback included the following: ● Controllers rated their workload as “about the same” as LAX ● Controllers rated the realism of the simulation as “about the same” as LAX ● The simulation successfully tasked controllers with the highest sustained traffic arrival and departure rates experienced at LAX ● Controllers requested that additional flights be included at the start of each scenario for increased workload and realism ● Outbound taxi times were accurate within 1-2 minutes of LAX times for aircraft originating in the north and south complex gates (approximately 82% of the total flights in the simulation) ● Runway occupancy times were within three seconds of corresponding LAX times for the http://ffc.arc.nasa.gov/about_us/technical_papers/runway.html (8 of 17) [6/5/2003 11:41:58 AM] Runway Incursion Studies in NASA'S FutureFlight Central inboard runways (24L, 25R), although the FFC occupancy times were longer than LAX times ● Duration of voice transmissions was on average 5-8% longer at FFC ● An average of 10-15% fewer voice transmissions per hour was accomplished at FFC as opposed to LAX [2] Feedback from the controllers proved that FFC engineers had been successful in recreating realistic traffic scenarios for the simulations. Controllers reported becoming involved in the problem at hand, working traffic and making sequencing decisions as if the aircraft out the window were real. With the Phase 1 results in mind, FFC engineers completed modifications to the experiment scenarios and proceeded with preparations for the Phase 2 tests. Phase 2 Experiment Objective and Subjective Measures Three types of test data were collected during each Phase 2 experiment run: controller subjective measures, airport operations statistical data, and controller voice communication data. FFC test engineers collected subjective measures in an eight-question survey completed by participants after each experiment run. For each question, FFC data reduction engineers calculated the mean rating and standard deviation by controller position. For questions one through seven, controllers were asked to evaluate the proposed alternative in terms of the following parameters: ● Overall efficiency ● Potential for runway incursion ● Traffic complexity ● Manageability of traffic flow ● Communication ● Coordination A 1-5 scale was used for the survey, where a value of 3 indicated that the alternative resulted in an operational complexity “about the same” as current LAX operations, and a value of 1 corresponded to a “worse than LAX today” rating. For question eight, controllers were presented with six operational criteria and asked to select up to three to indicate the most challenging aspects of each alternative. The total number of occurrences for each criterion was divided by the total number of forms filled out for any particular alternative. The resulting value indicated how frequently this criterion was marked as critical across all positions. Airport operations data was collected in order to compare the baseline LAX operation with the alternative scenarios. FFC engineers compared average arrival rates, average departure rates, average inbound taxi times by route, and average outbound taxi times by route against baseline http://ffc.arc.nasa.gov/about_us/technical_papers/runway.html (9 of 17) [6/5/2003 11:41:58 AM] Runway Incursion Studies in NASA'S FutureFlight Central