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Between 1988 and 2000 the U.S. Runway Safety Program Office (ATP-20) reported 3,420 runway incursions; 48% of these incursions were caused by pilots deviating from taxi clearances issued to them by air traffic control (ATC). Research at Ames Research Center has been conducted to identify the factors that contribute to these incidents and to develop cockpit display technologies to mitigate these and other errors in order to increase runway safety while simultaneously increasing efficiency.
Two full-mission surface-operations simulation studies were conducted in the Advanced Concept Flight Simulator (ACFS) at Ames. The ACFS was equipped with the Taxiway Navigation and Situation Awareness (T-NASA) display suite, which is composed of an electronic moving map (EMM) and a head-up display (HUD) to be used during taxi (see fig. 1). The EMM presented an over-the-shoulder perspective view of the airport surface, location of own-ship in real time, and the taxi route clearance, textually and graphically. The HUD presented local guidance information via scene-linked symbols depicting the centerline and edges of the cleared taxiways. The ACFS was also equipped with advanced data-link technology that transmitted an electronic record of all ATC communications to the cockpit.
The simulations revealed that pilots committed navigation errors on 17% of land-and-taxi-to-gate trials in simulated low-visibility and night conditions. These navigation errors occurred as often during night conditions as during low-visibility conditions. An analysis of these navigation errors revealed three distinct classes of errors: (1) planning errors (formulating an erroneous understanding of the taxi route), (2) decision errors (making an incorrect turn choice at a taxiway intersection), and (3) exe-cution errors (incorrectly maneuvering through an intersection).
Each class of errors had a unique set of contributing factors and mitigating solutions (see fig. 2). Planning errors occurred most often because of miscommunication between pilots and ATC. Technologies such as data-link and the T-NASA EMM that provide clear, unambiguous, and readily available representations of the clearance were shown to mitigate these errors. Decision errors occurred because of high operational demands, as well as because of inadequate navigational awareness. The T-NASA HUD and EMM in combination reduced the number of these errors by providing pilots both global navigational awareness and local control guidance. Finally, execution errors were caused by inadequate or confusing environmental cues such as complex taxiway geometry, confusing signs and markings, and the "sea-of-blue lights" phenomenon (that is, the blue taxi lights form a confusing pattern when viewed off axis). The T-NASA HUD disambiguated the external environment cues and reduced the frequency of errors.
These studies revealed three classes of navigation errors: planning, decision, and execution. Further, it was shown that cockpit display technologies (such as T-NASA) that address these contributing factors can augment pilots' cognitive, decision making, and perceptual abilities, thereby resulting in fewer navigation errors and increased runway safety.
Point of Contact: Becky L. Hooey
(650) 604-2399
bhooey@mail.arc.nasa.gov
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Fig. 1. The T-NASA System consists of an electronic moving map and a head-up display depicting the cleared taxi route transmitted via data-link ATC.
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Fig. 2. The T-NASA cockpit displays mitigate navigation errors during surface operations, increasing taxi efficiency and safety.
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