Russell V. Parrish

CFIT prevention using synthetic vision

In commercial aviation, over 30 percent of all fatal accidents worldwide are categorized as Controlled Flight Into Terrain (CFIT) accidents where a fully functioning airplane is inadvertently flown into the ground, water, or an obstacle. An experiment was conducted at NASA Langley Research Center investigating the presentation of a synthetic terrain database scene to the pilot on a Primary Flight Display (PFD). The major hypothesis for the experiment is that a synthetic vision system (SVS) will improve the pilots ability to detect and avoid a potential CFIT compared to conventional flight instrumentation. All display conditions, including the baseline, contained a Terrain Awareness and Warning System (TAWS) and Vertical Situation Display (VSD) enhanced Navigation Display (ND). Sixteen pilots each flew 22 approach / departure maneuvers in Instrument Meteorological Conditions (IMC) to the terrain challenged Eagle County Regional Airport (EGE) in Colorado. For the final run, the flight guidance cues were altered such that the departure path went into the terrain. All pilots with a SVS enhanced PFD (12 of 16 pilots) noticed and avoided the potential CFIT situation. All of the pilots who flew the anomaly with the baseline display configuration (which included a TAWS and VSD enhanced ND) had a CFIT event.

New computational control techniques and increased understanding for stereo 3-D displays

Three-dimensional pictorial displays, incorporating depth cues via stereopsis, offer a potential means of displaying information in a natural way to enhance situational awareness and provide increases in operator performance. Conventional computational techniques rely on asymptotic transformations and symmetric clipping to provide the stereo pair. New techniques that replace these conventional computations were developed to increase the control of the stereo-viewing space. Also, the effective region of stereopsis cuing was determined empirically by comparing perceived depth against computed depth. Conventional asymptotic transformations, used to map the visual scene to the stereo viewing volume, allow a single, specific scene distance to be fixed at the screen location. The new piece-wise linear approach allows creative partitioning of the depth viewing volume, with freedom to place the depth cuing emphasis where desired. Asymmetric clipping makes better use of the available display surface than symmetric clipping, and provides increased fields-of-view throughout the depth-viewing volume. The results of the experiment determining the effective region of stereopsis cuing indicate that a practical viewing volume falls between -25%and+60% of the viewer-to-screen distance. Also, the data revealed that increasing viewer-to-CRT distances provide increasing amounts of usable depth.

Nasa Synthetic Vision Ege Flight Test

NASA Langley Research Center conducted flight tests at the Eagle County, Colorado airport to evaluate synthetic vision concepts. Three display concepts (size “A” head-down, size “X” head-down, and head-up displays) and two texture concepts (photo, generic) were assessed for situation awareness and flight technical error / performance while making approaches to Runway 25 and Runway 07 and simulated engine-out Cottonwood 2 and KREMM departures. The results of the study confirm the retrofit capability of the HUD and Size “A” SVS concepts to significantly improve situation awareness and performance over current EFIS glass and non-glass instruments for difficult approaches in terrain- challenged environments.

Flight test evaluation of tactical Synthetic Vision display concepts in a terrain-challenged operating environment

NASAs Aviation Safety Program, Synthetic Vision Systems Project is developing display concepts to improve pilot terrain/situational awareness by providing a perspective synthetic view of the outside world through an on-board database driven by precise aircraft position information updating via Global Positioning System-based data. This work is aimed at eliminating visibility-induced errors and low visibility conditions as a causal factor to civil aircraft accidents, as well as replicating the operational benefits of clear day flight operations regardless of the actual outside visibility condition. A flight test evaluation of tactical Synthetic Vision display concepts was recently conducted in the terrain-challenged operating environment of the Eagle County Regional Airport. Several display concepts for head-up displays and head-down displays ranging from ARINC Standard Size A through Size X were tested. Several pilots evaluated these displays for acceptability, usability, and situational/terrain awareness while flying existing commercial airline operating procedures for Eagle County Regional Airport. All tactical Synthetic Vision display concepts provided measurable increases in the pilots subjective terrain awareness over the baseline aircraft displays. The head-down display presentations yielded better terrain awareness over the head-up display synthetic vision display concepts that were tested. Limitations in the head-up display concepts were uncovered that suggest further research.

Synthetic Vision CFIT Experiments for GA and Commercial Aircraft: "A Picture Is Worth A Thousand Lives"

Because restricted visibility has been implicated in the majority of commercial and general aviation accidents, solutions will need to focus on how to enhance safety during instrument meteorological conditions (IMC). The NASA Synthetic Vision Systems (SVS) project is developing technologies to help achieve these goals through the synthetic presentation of how the outside world would look to the pilot if vision were not reduced. The potential safety outcome would be a significant reduction in several accident categories, such as controlled-flight-into-terrain (CFIT), that have restricted visibility as a causal factor. The paper describes two experiments that demonstrated the efficacy of synthetic vision technology to prevent CFIT accidents for both general aviation and commercial aircraft.

Depth-viewing-volume increase by collimation of stereo 3-D displays

The results from an investigation into whether or not a dramatic increase in depth-viewing volume for stereo 3-D displays would be provided by the application of collimated optics to a stereo display source are presented. As background, some previously used 3-D stereo displays are described. The graphics-generation hardware and software are discussed. The stereo visual system is described. The collimation system consists of a beam-splitter and reflective mirror combination. The curvature of the mirror and display source placement provided a collimated output to the viewer. A conventional stereo 3-D monitor, although it had a nonoptimal size and curvature profile, was mounted on the collimation system. The results show that even though the actual screen distance was set by design at 27 in, the light collimation produced a virtual screen distance, subjectively estimated at between 50 and 100 ft.<<ETX>>

In-simulator assessment of trade-offs arising from mixture of color cuing and monocular, binoptic, and stereopsis cuing information

Research done to assess the tradeoffs arising from the mixture of color cueing and monocular, binocular, and stereopsis cueing information in peripheral monitoring displays encountered in helmet-mounted display (HMD) systems is discussed. The accompanying effect of stereopsis cueing in the foveal display of tracking information was assessed. A description of the simulator as well as experimental results are provided. The results of this experiment indicate that binoptic display of monitoring information in the right-peripheral region, with color cueing as an alerting function, to such information, and stereopsis cueing in the central region of the display, were the most effective display conditions examined. To obtain the advantages, of binocular summation with binoptic displays in the peripheral region, a sacrifice in total field of view (FOV) is required. The performance gains realized from binoptic or stereopsis cueing over monocular display in the periphery require a loss of total FOV that may not be justified for all applications.<<ETX>>

Recent research results in stereo 3-D pictorial displays at Langley Research Center

Results from a NASA Langley Research Center program which addressed stereo 3-D pictorial displays from a comprehensive standpoint are reviewed. The program dealt with human factors issues and display technology aspects, as well as flight display applications. The human factors findings include addressing a fundamental issue challenging the application of stereoscopic displays in head-down flight applications, with the determination that stereoacuity is unaffected by the short-term use of stereo 3-D displays. While stereoacuity has been a traditional measurement of depth perception abilities, it is a measure of relative depth, rather than actual depth (absolute depth). Therefore, depth perception effects based on size and distance judgments and long-term stereo exposure remain issues to be investigated. The applications of stereo 3-D to pictorial flight displays within the program have repeatedly demonstrated increases in pilot situational awareness and task performance improvements. These improvements have been obtained within the constraints of the limited viewing volume available with conventional stereo displays. A number of stereo 3-D pictorial display applications are described, including recovery from flight-path offset, helicopter hover, and emulated helmet-mounted display.<<ETX>>

Effect on real-world depth perception from exposure to heads-down stereoscopic flight displays

The application of stereopsis (true depth) cuing to advanced heads-down flight display concepts offers potential gains in pilot situation awareness and improved task performance, but little attention has been focused on a fundamental issue involving their use. The goal of this research was to determine whether or not the short-term use of heads-down stereoscopic displays in flight applications would degrade the real-world depth perception of pilots using such displays. Stereoacuity tests are traditionally used to measure the real-world depth perception of a subject. This study used such a test as part of the experimental protocol. Eight transport pilots flew repeated simulated landing approaches using both non-stereo and stereo 3-D heads-down pathway-in-the-sky displays. At the decision height of each approach, the pilots transitioned to a stereoacuity test using real objects rather than a two-dimensional target test apparatus. Statistical analysis of stereoacuity measures (averaged over pilots and replicates), comparing a control condition of no-exposure to any electronic flight display with the transition data from non-stereo and stereopsis displays, revealed no significant differences for any of the conditions. Clearly, transitioning from short-term exposure to a heads-down stereopsis display has no more effect on realworld depth perception (based on stereoacuity) than transitioning from a non-stereo display. However, depth perception effects based on size and distance judgements, and long-term exposure remain issues to be investigated.

Determination of washout performance of various monochrome displays under simulated flight ambient and solar lighting conditions

The aircraft cockpit ambient lighting simulation system (ACALSS) has been developed to study display readability and associated pilot/vehicle performance effects in a part-task simulator cockpit. In the study reported, the ACALSS was used to determine the illumination levels at which subjects lose the ability to maintain aircraft states when using three display technologies as display media for primary flight displays: a standard monochrome EL (electroluminescent) flat-panel, a laboratory-class monochrome cathode-ray tube (CRT), and an enhanced-brightness EL flat-panel. The multivariate statistical technique of modified profile analysis was used to test for performance differences between display devices as functions of illumination levels.<<ETX>>