A shadow detection and extraction algorithm using digital elevation models and x‐band weather radar measurements

The aviation industry has been investigating the potential of synthetic and enhanced vision systems (SVS and EVS) to increase the situational awareness of pilots who are operating in low‐visibility weather conditions. Synthetic vision displays provide a real‐time depiction of a terrain model from the pilot's perspective. To ensure the integrity of this terrain depiction, consistency checking using remote sensing of the terrain environment has been suggested. This requires the detection and extraction of terrain features from both the model and the sensor measurements. Further, the features must be represented in the same reference domain.

Terrain shadowing occurs when areas are not in the line‐of‐sight of the observer. It is these shadowed regions and their morphological characteristics that are identified as the feature domain in which consistency can be assessed between two sources of terrain information. This paper describes an algorithm to extract shadow features from digital elevation models during flight to enable direct comparison with x‐band radar modus operandi. Results are presented using flight‐test data acquired from two platforms with different radar equipment.

The proposed algorithm not only has application to the consistency‐checking problem, but also to terrain navigation, image fusion, and digital elevation model accuracy assessments.     

Synthetic vision systems: the effects of guidance symbology, display size, and field of view

Two experiments conducted in a high-fidelity flight simulator examined the effects of guidance symbology, display size, and geometric field of view (GFOV) within a synthetic vision system (SVS). In Experiment 1, 18 pilots flew highlighted and low-lighted tunnel-in-the-sky displays, as well as a less cluttered follow-me aircraft (FMA), through a series of curved approaches over rugged terrain. The results revealed that both tunnels supported better flight path tracking and lower workload levels than did the FMA because of the availability of more preview information. Increasing tunnel intensity had no benefit on tracking and, in fact, degraded traffic awareness because of clutter and attentional tunneling. In Experiment 2, 24 pilots flew a lowlighted tunnel configured according to different display sizes (small or large) and GFOVs (30 degrees or 60 degrees). Measures of flight path tracking and terrain awareness generally favored the 60 degrees GFOV; however, there were no effects of display size. Actual or potential applications of this research include understanding the impact of SVS properties on flight path tracking, traffic and terrain awareness, workload, and the allocation of attention.     

The virtual landing pad: facilitating rotary-wing landing operations in degraded visual environments

The safety of rotary-wing operations is significantly affected by the local weather conditions, especially during key phases of flight including hover and landing. Despite the operational flexibility of rotary-wing craft, such craft accounts for a significantly greater proportion of accidents than their fixed-wing counterparts. A key period of risk when operating rotary-wing aircraft is during operations that occur in degraded visual environments, for example as a result of thick fog. During such conditions, pilots’ workload significantly increases and their situation awareness can be greatly impeded. The current study examines the extent to which providing information to pilots via the use of a head-up display (HUD) influenced perceived workload and situation awareness, when operating in both clear and degraded visual environments. Results suggest that whilst the HUD did not benefit pilots during clear conditions, workload was reduced when operating in degraded visual conditions. Overall results demonstrate that access to the HUD reduces the difficulties associated with flying in degraded visual environments.     

Use of Highways in the Sky and a virtual pad for landing Head Up Display symbology to enable improved helicopter pilots situation awareness and workload in degraded visual conditions

Abstract

Flight within degraded visual conditions is a great challenge to pilots of rotary-wing craft. Environmental cues typically used to guide interpretation of speed, location and approach can become obscured, forcing the pilots to rely on data available from in-cockpit instrumentation. To ease the task of flight during degraded visual conditions, pilots require easy access to flight critical information. The current study examined the effect of ‘Highways in the Sky’ symbology and a conformal virtual pad for landing presented using a Head Up Display (HUD) on pilots’ workload and situation awareness for both clear and degraded conditions across a series of simulated rotary-wing approach and landings. Results suggest that access to the HUD lead to significant improvements to pilots’ situation awareness, especially within degraded visual conditions. Importantly, access to the HUD facilitated pilot awareness in all conditions. Results are discussed in terms of future HUD development.

Practitioner Summary: This paper explores the use of a novel Heads Up Display, to facilitate rotary-wing pilots’ situation awareness and workload for simulated flights in both clear and degraded visual conditions. Results suggest that access to HUD facilitated pilots’ situation awareness, especially when flying in degraded conditions.     

Investigating pilot performance using mixed-modality simulated data link

OBJECTIVE: General aviation (GA) pilot performance utilizing a mixed-modality simulated data link was objectively evaluated based on the time required in accessing, understanding, and executing data link commands. Additional subjective data were gathered on workload, situation awareness (SA), and preference. BACKGROUND: Research exploring mixed-modality data link integration to the single-pilot GA cockpit is lacking, especially with respect to potential effects on safety. METHODS: Sixteen visual flight rules (VFR)-rated pilots participated in an experiment using a flight simulator equipped with a mixed-modality data link. Data link modalities were text display, synthesized speech, digitized speech, and synthesized speech/text combination. Flight conditions included VFR (unlimited ceiling and visibility) or marginal VFR flight conditions (clouds 2,800 ft above ground level, 3-mile visibility). RESULTS: Statistically significant differences were found in pilot performance, mental workload, and SA across the data link modalities. Textual data link resulted in increased time and workload as compared with the three speech-type data link conditions, which did not differ. SA measures indicated higher performance with textual and digitized speech data link conditions. CONCLUSION: Textual data link can be significantly enhanced for single-pilot GA operations by the addition of a speech component. APPLICATION: Potential applications include operational safety in future GA systems that incorporate data link for use by a single pilot and guidance in the development of flight performance objectives for these systems.     

Interface design on cabin pressurization system affecting pilot's situation awareness: The comparison between digital displays and pointed displays

The fundamental approach to improve pilots’ situation awareness (SA) would be to reorganize and restructure the presentation of information to fit pilot's cognitive model on the flight deck. This would facilitate pilots’ perception, understanding, and projection, hence making it easier to find the relevant targets. Sixty pilots (30 B‐737 pilots and 30 B‐777 pilots) participated in this study to investigate pilots’ SA while interacting with digital displays and moving pointed needle displays on cabin pressurization system. The results have shown significant differences on pilots’ perception, understanding, and overall SA between digital display and pointed display on the flight deck. Pilots significantly preferred the digital design cabin pressurization system, which is consistent with the proximity compatibility principle, and the position of the display on the center instrument panel is easily accessible to both pilots and does not require large head movements. There are some recommendations on the cabin pressurization design including the size of outflow valve position indicator, which should be significantly increased to provided saliency of information; color coding should be used on cabin altitude and differential pressure indicator to mark critical cabin altitude; and standard operating procedures shall include cabin altitude and differential pressure reading by pilot monitoring. The final and completed solution to the issues on the cabin pressurization system is to redesign the scattered pointed displays as integrated digital displays to fit the human‐centered principle.     

基于DWL的合成视景系统数据库的完整性

合成视景系统（SVS）是解决可控飞行撞地(CFIT)事故的有效途径,近年来,国家实施的重点基础研究发展计划已经把SVS的相关研究纳入了计划研究的一部分。SVS数据库的完整性研究是SVS研究中比较重要的部分。基于现阶段大部分飞机上都配备GPS、雷达测高仪等设备,本文主要基于下视传感器（DWL）对SVS数据库的完整性进行研究。基于DWL对SVS数据库进行实时监控可以有效保证数据库垂直方向数据的完整性,但是对于飞机数据库水平方向数据的完整性保证能力还略显不足。     

Workload benefits of colour coded head-up flight symbology during high workload flight

The manipulation of colour in display symbology design has been recognised as a method to improve operator experience and performance. An earlier paper by the authors demonstrated that redundantly colour coding head-up flight symbology supported the manual flying performance of both professional and non-professional pilots during low-workload flying scenarios. In this study the workload and performance of 12 professional airline pilots was evaluated in high workload conditions whilst they flew manoeuvres and an instrument landing system (ILS) approach with and without the presence of colour feedback on a head up display (HUD). Workload was manipulated by presenting pilots with a concurrent auditory n-back task. Colour coded flight symbology reduced the subjective workload of the pilots during high workload conditions. In contrast, manual flying performance during high workload was not improved by the presence of colour coded feedback.     

Spatial awareness in synthetic vision systems: using spatial and temporal judgments to evaluate texture and field of view

OBJECTIVE: This work introduced judgment-based measures of spatial awareness and used them to evaluate terrain textures and fields of view (FOVs) in synthetic vision system (SVS) displays. BACKGROUND: SVSs are cockpit technologies that depict computer-generated views of terrain surrounding an aircraft. In the assessment of textures and FOVs for SVSs, no studies have directly measured the three levels of spatial awareness with respect to terrain: identification of terrain, its relative spatial location, and its relative temporal location. METHODS: Eighteen pilots made four judgments (relative azimuth angle, distance, height, and abeam time) regarding the location of terrain points displayed in 112 noninteractive 5-s simulations of an SVS head-down display. There were two between-subject variables (texture order and FOV order) and five within-subject variables (texture, FOV, and the terrain point's relative azimuth angle, distance, and height). RESULTS: Texture produced significant main and interaction effects for the magnitude of error in the relative angle, distance, height, and abeam time judgments. FOV interaction effects were significant for the directional magnitude of error in the relative distance, height, and abeam time judgments. CONCLUSION: Spatial awareness was best facilitated by the elevation fishnet (EF), photo fishnet (PF), and photo elevation fishnet (PEF) textures. APPLICATION: This study supports the recommendation that the EF, PF, and PEF textures be further evaluated in future SVS experiments. Additionally, the judgment-based spatial awareness measures used in this experiment could be used to evaluate other display parameters and depth cues in SVSs.     

Pathway HUDs: are they viable?

We describe two experiments that examine 3D pathway displays in a head-up location for aircraft landing and taxi. We address both guidance performance and pilot strategies in dividing, focusing, and allocating attention between flight path information and event monitoring. In Experiment 1 the 3D pathway head-up display (HUD) was compared with a conventional 2D HUD. The former was found to produce better guidance, with few costs to event detection. Some evidence was provided that attentional tunneling of the pathway HUD inhibits the detection of unexpected traffic events. In Experiment 2, the pathway display was compared in a head-up versus a head-down location. Excellent guidance was achieved in both locations. A slight HUD cost for vertical tracking in the air was offset by a HUD benefit for event detection and for lateral tracking during taxi (i.e., on the ground). The results of both experiments are interpreted within the framework of object- and space-based theories of visual attention and point to the conclusion that pathway HUDs combine the independent advantages of pathways and HUDs, particularly during ground operations. Actual or potential applications include understanding the costs and benefits of positioning a 3D pathway display in a head-up location.     

Effects of modes of cockpit automation on pilot performance and workload in a next generation flight concept of operation

The objective of this study was to compare the effects of various forms of advanced cockpit automation for flight planning on pilot performance and workload under a futuristic concept of operation. A lab experiment was conducted in which airline pilots flew simulated tailored arrivals to an airport using three modes of automation (MOAs), including a control‐display unit (CDU) to the aircraft flight management system, an enhanced CDU (CDU+), and a continuous descent approach (CDA) tool. The arrival scenario required replanning to avoid convective activity and was constrained by a minimum fuel requirement at the initial approach fix. The CDU and CDU+ modes allowed for point‐by‐point path planning or selection among multiple standard arrivals, respectively. The CDA mode completely automated the route replanning for pilots. It was expected that the higher‐level automation would significantly reduce pilot workload and improve overall flight performance. In general, results indicated that the MOAs influenced pilot performance and workload responses according to hypotheses. This study provides new knowledge about the relationship of cockpit automation and interface features with pilot performance and workload in a novel next generation–style flight concept of operation. © 2012 Wiley Periodicals, Inc.     

Superimposition, symbology, visual attention, and the head-up display

In two experiments we examined a number of related factors postulated to influence head-up display (HUD) performance. We addressed the benefit of reduced scanning and the cost of increasing the number of elements in the visual field by comparing a superimposed HUD with an identical display in a head-down position in varying visibility conditions. We explored the extent to which the characteristics of HUD symbology support a division of attention by contrasting conformal symbology (which links elements of the display image to elements of the far domain) with traditional instrument landing system (ILS) symbology. Together the two experiments provide strong evidence that minimizing scanning between flight instruments and the far domain contributes substantially to the observed HUD performance advantage. Experiment 1 provides little evidence for a performance cost attributable to visual clutter. In Experiment 2 the pattern of differences in lateral tracking error between conformal and traditional ILS symbology supports the hypothesis that, to the extent that the symbology forms an object with the far domain, attention may be divided between the superimposed image and its counterpart in the far domain.     

Autonomous flight cycles and extreme landings of airliners beyond the current limits and capabilities using artificial neural networks

We describe the Intelligent Autopilot System (IAS), a fully autonomous autopilot capable of piloting large jets such as airliners by learning from experienced human pilots using Artificial Neural Networks. The IAS is capable of autonomously executing the required piloting tasks and handling the different flight phases to fly an aircraft from one airport to another including takeoff, climb, cruise, navigate, descent, approach, and land in simulation. In addition, the IAS is capable of autonomously landing large jets in the presence of extreme weather conditions including severe crosswind, gust, wind shear, and turbulence. The IAS is a potential solution to the limitations and robustness problems of modern autopilots such as the inability to execute complete flights, the inability to handle extreme weather conditions especially during approach and landing where the aircraft’s speed is relatively low, and the uncertainty factor is high, and the pilots shortage problem compared to the increasing aircraft demand. In this paper, we present the work done by collaborating with the aviation industry to provide training data for the IAS to learn from. The training data is used by Artificial Neural Networks to generate control models automatically. The control models imitate the skills of the human pilot when executing all the piloting tasks required to pilot an aircraft between two airports. In addition, we introduce new ANNs trained to control the aircraft’s elevators, elevators’ trim, throttle, flaps, and new ailerons and rudder ANNs to counter the effects of extreme weather conditions and land safely. Experiments show that small datasets containing single demonstrations are sufficient to train the IAS and achieve excellent performance by using clearly separable and traceable neural network modules which eliminate the black-box problem of large Artificial Intelligence methods such as Deep Learning. In addition, experiments show that the IAS can handle landing in extreme weather conditions beyond the capabilities of modern autopilots and even experienced human pilots. The proposed IAS is a novel approach towards achieving full control autonomy of large jets using ANN models that match the skills and abilities of experienced human pilots and beyond.

     

Visual misperception in aviation: glide path performance in a black hole environment

OBJECTIVE: We sought to improve understanding of visual perception in aviation to mitigate mishaps in approaches to landing. BACKGROUND: Research has attempted to identify the most salient visual cues for glide path performance in impoverished visual conditions. Numerous aviation accidents caused by glide path overestimation (GPO) have occurred when a low glide path was induced by a black hole illusion (BHI) in featureless terrain during night approaches. METHOD: Twenty pilots flew simulated approaches under various visual cues of random terrain objects and approach lighting system (ALS) configurations. Performance was assessed relative to the desired 3 degrees glide path in terms of precision, bias, and stability. RESULTS: With the high-ratio (long, narrow) runway, the overall performance between 8.3 and 0.9 km from the runway depicted a concave approach shape found in BHI mishaps. The addition of random terrain objects failed to improve glide path performance, and an ALS commonly used at airports induced GPO and the resulting low glide path. The worst performance, however, resulted from a combination ALS consisting of both side and approach lights. Surprisingly, novice pilots flew more stable approaches than did experienced pilots. CONCLUSIONS: Low, unsafe approaches occur frequently in conditions with limited global and local visual cues. Approach lights lateral of the runway may counter the bias of the BHI. The variability suggested a proactive, cue-seeking behavior among experienced pilots as compared with novice pilots. APPLICATION: Visual spatial disorientation training in flight simulators should be used to demonstrate visual misperceptions in black hole environments and reduce pilots' confidence in their limited visual capabilities.     

Pilots’ gaze strategies and manual control performance using occlusion as a measurement technique during a simulated manual flight task

The aim of this study was to analyze pilots’ visual scanning under conditions visually restricted by the occlusion paradigm. During manual flight, pilots experienced interruptions in their panel scan due to concurring tasks and monitoring of distant displays. Eleven volunteer airline pilots performed several manual instrument landing system approaches in a fixed-base flight simulator. Some of these approaches were performed using the paradigm of occlusion with shutter glasses. Under occlusion, the gaze pattern analysis revealed that pilots demonstrated reduced mean glance durations, but did not reduce their attention to lesser information displays. The results also indicated that the attitude indicator (artificial horizon) as a preview instrument was less affected by occlusion compared to other areas of interest. A subsequent scanpath analysis revealed that vertical tracking was the predominant information acquisition strategy and corresponded to larger deviations on the glideslope. These results imply the need to optimize information even for short glances, and to be very cautious with adaptive layouts of free programmable or dynamic displays, and not to overburden the pilot flying with parallel tasks.     

Memory processes of flight situation awareness: interactive roles of working memory capacity, long-term working memory, and expertise

This research examined the role of working memory (WM) capacity and long-term working memory (LT-WM) in flight situation awareness (SA). We developed spatial and verbal measures of WM capacity and LT-WM skill and then determined the ability of these measures to predict pilot performance on SA tasks. Although both spatial measures of WM capacity and LT-WM skills were important predictors of SA performance, their importance varied as a function of pilot expertise. Spatial WM capacity was most predictive of SA performance for novices, whereas spatial LT-WM skill based on configurations of control flight elements (attitude and power) was most predictive for experts. Furthermore, evidence for an interactive role of WM and LT-WM mechanisms was indicated. Actual or potential applications of this research include cognitive analysis of pilot expertise and aviation training.     

A Method of Applying Flight Data to Evaluate Landing Operation Performance

Abstract

Pilots’ operation has an important effect on flight safety and performance, particularly in the final landing stage when pilots need to deal with complicated operations. This study aims to determine the potential value of flight data and develop a method of evaluating a pilot’s performance during landing phase based on flight quick access recorder (QAR) data from the perspective of risk assessment. First, a Landing Operation Performance Evaluation Model was developed based on risk evaluation principles. Three landing parameters, which are touchdown distance, touchdown vertical acceleration and touchdown pitch angle, were selected as indicators to evaluate the pilots’ landing operation performance in this model. Second, the flight landing operation performance evaluation system (FLOPES) was set up based on the evaluation model. Test results showed that FLOPES can accomplish all calculation flow of operation performance evaluation. Finally, it concluded that this method is a more accurate and effective way for evaluating the landing operation performance of a flight. It could be as a practical tool for airlines to manage landing risk quantitatively and to provide a more practical support for improving training and design in aviation.Practitioner summary: This study aims to determine the potential value of flight data and to develop a method of evaluating pilot’s landing operation performance from the risk evaluation perspective. Test results showed that this method is effective and could be as a practical tool for airlines to manage landing risk and improve training.Abbreviations:QAR: Quick Access Recorder; FLOPES: Flight Landing Operation Performance Evaluation System; ICAO: International Civil Aviation Organization; IATA: International Air Transport Association; SMS: Safety Management System; CAAC: Civil Aviation Administration of China; FOQA: Flight Operations Quality Assurance; VBA: Visual Basic for Applications     

Bidirectional raster scanning to increase time for vector writing in avionics see‐through displays

See‐through displays (STD) like head‐up displays (HUD) play major role in providing aircraft data to pilot through a visual interface. The data is displayed in form of symbology in pilot's line of sight using vector scanning technique and is deciphered to get flight and mission information. Contrast ratio required to see against bright sunlight at high altitudes is given only by luminance of cathode ray tube (CRT). Therefore, CRT is still used as display source in avionic HUDs, although other devices are also being explored for these applications. Aircraft's night mode operation requires raster display of external scene information along with vector data display due to low visibility during night. It reduces time available for writing vector data during night mode resulting in reduced symbology. Conventionally used raster scanning methods are unidirectional scanning methods. Bidirectional raster scanning (BRS) is an unconventional approach which scans display screen from both directions. In present work, an algorithm for BRS has been developed in VHDL providing more time for vector writing by increasing vertical retrace period (VRP) of raster scanning. Functional verification of design has been performed by simulations carried out through test‐bench and VRP is increased to 5.8304 ms from conventional 1.2800 ms per field.     

A comparative survey of the utility of cross-cockpit linkages and autoflight systems' backfeed to the control inceptors of commercial aircraft

'Fly-by-wire' (FBW) electronic flight control systems in modern commercial aircraft have removed the requirement for the primary control inceptors in the cockpit to have a cross-cockpit linkage, and also for them to be back-driven from the autoflight systems. This comparative survey of 157 commercial pilots with current type ratings on either an FBW aircraft or a conventional technology aircraft, however, suggests that the deletion of these linkages may have degraded the lines of communication in the cockpit, both between the pilots and between the pilot and the aircraft. It is argued that this may adversely affect a pilot's situation awareness.     

Object-oriented landing gear model in a PC-based flight simulator

Training pilots the skill of maneuvering an aircraft on ground is important for flight safety. This demands a detailed landing gear model running in real-time. We developed the model and verified its validity by contrast with flight test data. It is accurate sufficiently and very suitable for real-time flight simulation to represent complex ground reaction behavior under various conditions and occasions. Based on this model, we realized a landing gear class in a unified flight simulation framework written in C++ and successfully applied the whole simulation codes through S-function in a PC-based experimental flight simulator. Because of the unique features of object-oriented design principles, the software framework presented here is structural, transplantable and convenient to maintain. The constitution and the quality of the simulator reveal that it would have cause to decrease the cost for developing a flight simulator with higher fidelity in future.