Information Intensive. Advances in display technology, sensor technology, and data availability have resulted in an enormous amount of data available to the pilot in EFIS-enhanced general aviation operations. Unless properly organized and presented, this vast amount of data could easily overwhelm the pilot, resulting in decreased situational awareness and safety.
1. Dynamic. The general aviation flight environment is dynamic and complex. Pilots must have sufficient situational awareness to respond quickly, accurately, and safely to changes mandated by ATC, weather, traffic, or in-flight emergencies.
2. Multi-Tasking. Pilots, especially in single-pilot IFR operations, are frequently required to perform multiple tasks simultaneously while processing data from multiple sources.
3. Severe Consequence for Error. In many operations, there are severe consequences for pilot error.
4. High Workload. The general aviation environment has become much more demanding in recent years and can be characterized as high workload and stressful. This is most evident in critical phases of IFR operations.
5. Physically Constrained. The cockpit environments of many high-performance general aviation aircraft impose various physical constraints that may impair a pilot's ability to adequately observe, operate, and interpret a large number of discrete instruments.
6. Environmentally Hostile. The cockpit and component installation areas of general aviation aircraft constitute a harsh environment for pilot operation and electronic/mechanical component function. From a human factors standpoint, environmental considerations include vibration, ambient noise, cockpit lighting, viewing angles, operation in turbulence, tactile identification and feedback, and operational distraction. Component functional considerations include temperature extremes, vibration, EMI emissions and susceptibility, HIRF, and moisture.

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II. Design Concept

Pilot-Centered
Chelton EFIS symbology and hardware design are implemented using a "pilot-centered" approach. The pilot-centered philosophy is based on the functional and informational requirements of the cockpit environment as they relate to the pilot's capabilities and limitations. In a pilot-centered cockpit, data is processed and displayed so that the pilot acquires information rapidly and intuitively. The pilot-centered approach assumes that a human pilot, empowered with situational awareness, remains the most flexible and safest means of aircraft control. Chelton explicitly rejects the concept of "automation-centered" displays that relegates the pilot to the role of an autopilot monitor. In a pilot-centered cockpit, the pilot always has the situational awareness required to control the aircraft, even when it is being flown by an autopilot.

Integrated Systems
Chelton's symbology and hardware are highly integrated. In an integrated system, the means for displaying and controlling various disparate systems are integrated into common control and display schemes. This facilitates the accomplishment of a multitude of tasks in a complex environment and reduces the time required to learn and effectively use new systems.

IFR-VFR Equivalence
The cornerstone of Chelton's pilot-centered philosophy, Chelton Flight Systems unique primary flight display symbology presents the pilot with a sensor and database generated virtual reality view of the flight environment ahead of the aircraft. The view includes real-time 3-D terrain, 3-D navigation symbology, artificial horizon, and flight instruments integrated into a single presentation on the display. The pilot is presented with a sunny day VFR view on the display that matches the real world, regardless of meteorological conditions. From birth, humans learn to interact with a three-dimensional world. Replacing a large number of discrete instruments with a Chelton's primary flight display greatly increases situational awareness and minimizes primary causes of accidents, including loss of aircraft control, controlled flight into terrain, and misinterpretation of flight instruments—virtually none of which occur during VFR flight.

Maximize Situational Awareness
The Chelton EFIS utilizes unique symbology designed to give the general aviation pilot the greatest amount of situational awareness. Evidence is overwhelming that the loss of situational awareness plays a dominant role in general aviation aircraft accidents and incidents. The ability to anticipate events and to plan proactively can ultimately determine the success of a flight, especially in an IFR environment.

Minimize Errors and Improve Error Management
The Chelton EFIS symbology minimizes the potential for pilot error and maximizes the potential for recovering from pilot error should they occur. The most common cause of aviation accidents is pilot error. Symbology is designed to minimize the chance of misinterpretation or loss or situational awareness which may cause inappropriate action by the pilot. In addition, upon certain sensed parameters, symbology will adapt to help focus the pilot's attention onto the most critical piloting tasks; vocal and visual alerts are provided to further sharpen the pilot's focus and awareness of critical conditions.

Provide Easy Access to Information
To reduce pilot workload, the EFIS symbology facilitates access to and interpretation of flight-relevant and time-critical information. Additionally, it enables the pilot to quickly locate important information in response to changes in the flight environment. To the extent possible, the symbology integrates data from various sensors into truly useful information, thus minimizing the need for the pilot to mentally integrate information from multiple discrete sources.

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III. Display Principles

Prioritize Critical and Non-Critical Information
The Chelton displays are designed to minimize the information density on the screen by prioritizing and limiting information to be displayed. Minimizing information density is critical for avoiding misinterpretation and pilot confusion. In support of this philosophy, Chelton purposefully avoids competing by having a large "feature count." The inclusion of too many features, many of which are of negligible value to the pilot, can lead to distraction, confusion and misinterpretation of important information. Chelton believes that only features proven highly effective in the crucible of the flight environment should be included in its systems. Prospective features go through a series of "tryout" flights and simulator tests with experienced pilots before being included in the system.

Minimal Visual Competition
Information on the Chelton displays is organized so that visual competition among items of information is minimized. The most important information for the flight segment being flown appears as the most prominent information on the display. Prominent display of non-critical or non-essential information leads to distraction and confusion in assimilating the important information. Too much highlighting or the overuse of color interferes with information comprehension.

Frame of Reference Compatibility
Information on the Chelton EFIS is presented based upon the pilot's frame of reference (also know as "inside-out"). Displaying information in this manner facilitates more rapid and intuitive assimilation of information and eases the transition from instrument to visual flight. For example, Chelton's primary flight display is arranged so that the elements on the screen are conformal with the outside world. This matches the view the pilot sees as he or she looks forward out the window from the cockpit.

User Control of Displayed Data
Where possible, the pilot is allowed to control the amount and format of displayed data as necessary to meet the requirements of the current mode of flight. The most important information for the flight segment being flown appears as the most prominent information on the display; additional, non-critical information can be displayed by the pilot if desired. Continuous display of non-essential information can lead to distraction, confusion and misinterpretation of important information.

Display Declutter
Chelton EFIS displays are as uncluttered as possible; information is presented simply and in a well-organized manner. Major sources of display clutter include the number of elements to be searched, the number of confusing objects in a display, and their spatial proximity. Display clutter can directly affect a pilot's ability to visually locate flight-relevant information within and across displays, especially when under the stresses of single-pilot IFR or during an in-flight emergency.

Displays are decluttered in two manners: manually and automatically. Manual declutter allows the pilot to control the amount and format of displayed data as necessary to meet the requirements of the current mode of flight. Automatic declutter is based on a system of hierarchical information needs; for example, in the unusual attitude recovery mode, the most important flight information (attitude) is enhanced and information of lesser importance in this mode (3-D waypoint symbol) is removed. Automatic decluttering of the moving map removes the display of lesser features (i.e. NDB's or named fixes) as the map is zoomed out to larger scales.

Display Density
Chelton EFIS display density never exceeds 50%, and every effort is made to maintain less than 25%. Display density is automatically minimized for displays of critical information, like unusual attitude recovery. The unused areas of displays are distributed into separate logical groups and categories of data.

Consistent Format
Chelton display formats have a consistent structure and layout so that display features are always presented in the same way across display pages that support similar functions. Where appropriate, data fields such as headers and message areas are consistent in methodology and location across displays. Consistency speeds data acquisition by pilots and minimizes error and misinterpretation. In particular, messages, warnings, and pilot prompts appear consistently in the same location throughout the various display pages. The areas in which these items are displayed are reserved for this purpose. Consistency promotes rapid assimilation and processing of information. Warning and caution information must be quickly recognized and appropriate action taken, as this information is often time critical.

Integrated Format
When the pilot is required to assess the relation among different informational elements, the information is provided in an integrated format rather than partitioning them into separate windows or display pages. For example, fuel totalizer (range and endurance) calculations are displayed in the same window as the distance and ETE to the active and destination waypoints. Integrated formats reduce pilot mental and physical workload and reduce the possibility or error in interpreting data based on memory.

Display of Trend Information
All appropriate information is formatted and displayed in order to enable the pilot to easily identify historical and predictive trend information for parameters that require some estimate of this information. Trend information may be more usable than precise data for certain applications. For example, the projected path on the navigation display predicts the aircraft's ground track trend one minute into the future to facilitate course segment interception. For applications such as altitude, a combination of analog (trend) and digital (instantaneous) information has been proven by NASA and the military as being most appropriate.

Distinctive Display Categories
Chelton EFIS products employ distinct differentiation between different types of information such as display titles, menu options, operational modes, and control options. Differentiation is achieved with size and weighting of characters, color, position, and auditory annunciation, allowing the pilot to understand the type and category of information being presented in an instant.

Critical Information Protection
Key display data, such as critical information, warnings or other messages, has priority over all other information and cannot be overwritten.

Character Size
All Chelton EFIS symbology meets or exceeds FAA TSO and RTCA minimum operational performance standards for character size.

Use of Abbreviations
When abbreviations are used, they are distinctive, commonly recognized by pilots, and are used consistently. All abbreviations conform to appropriate FAA standards.

Shape Coding
Chelton Flight Systems EFIS employ different shapes to help pilots discriminate between different categories of information on the displays. When shapes are used, they are based on established standards or conventional meanings, and the number of different shapes does not exceed 15. Shape coding has been proven to be a quick way to differentiate between different types of information being presented at a glance. Shape coding promotes quick assimilation of information while minimizing the requirement of analysis. Shape coding also helps those pilots with reduced color vision.

Color-Coding
A total of 10 colors are used for coding different classes of information. Display elements are assigned colors based on the nature of the information to be displayed, and conform as closely as possible to established meanings associated with particular colors. Color-coding can be one of the fastest and most efficient means of differentiating between the type, importance, and meaning if information being presented.

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IV. Hardware Human Factors and Environmental Considerations

Appropriate Display Brightness
Chelton Flight Systems EFIS displays are designed to be adaptable to all likely cockpit illumination conditions, from direct sunlight to total darkness. Brightness is pilot-adjustable and an integral photocell determines initial illumination level at startup. Hardware illumination (buttons, slip indicator) is independently adjustable. Automatic initial brightness control ensures preservation of pilot nighttime vision during system startup. Manual control of button and display brightness allows adjustment based on pilot preference.

Tactile Feedback and Differentiation
The Chelton EFIS bezel controls are designed to give the pilot a tactile report upon actuation. Button and rotary switches are selected to provide appropriate "snap" to the finger when pressed or turned in order to confirm to the pilot that the switched has been actuated. Tactile differentiation of controls is accomplished through the bezel design to allow the pilot locate specific buttons without visual reference. Tactile differentiation enables the pilot to quickly make menu selections without looking at the screen or controls, thereby minimizing head-down time.

Facilitate Operation in Turbulent and High Vibration Environments
The EFIS bezel has several key design features that facilitate system control in turbulent and vibrating conditions. Indexing bevels at the top of each row of buttons and a "step" down each side of the display provide the pilot with a substantial surface on which to brace the hand while operating the buttons. Controls are large and widely spaced to minimize accidental actuation. Button labels are large and bold to provide readability in the relatively high vibration cockpit of piston/propeller and rotary wing aircraft. Rotary controls feature large, non-slip rubber grasping surfaces and solid metal shafts for reliable operation in turbulence.

Minimize Operational Distraction Level
Chelton EFIS human factors interface (operation of controls, menus, alphanumeric input, etc.) requirements are designed to minimize operational distraction. For example, alphanumeric waypoint entry is done on the screen rather than a keyboard mounted elsewhere on the panel so that the pilot still receives the visual cues required for aircraft control while entering characters. Removing attention from the primary flight display in order to enter information would be an operational distraction and would divert the pilot's attention from the task of aircraft control. This is extremely important in typical general aviation single-pilot IFR operations.

Address Environmental Considerations
All Chelton EFIS hardware is designed to conform to FAA/RTCA DO-160 environmental conditions requirements. Hardware is designed and tested to exceed the most demanding case anticipated in each DO-160 environmental category.

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IFR-VFR Equivalence
The cornerstone of Chelton's pilot-centered philosophy, Chelton Flight Systems unique primary flight display symbology presents the pilot with a sensor and database generated virtual reality view of the flight environment ahead of the aircraft. The view includes real-time 3-D terrain, 3-D navigation symbology, artificial horizon, and flight instruments integrated into a single presentation on the display. The pilot is presented with a sunny day VFR view on the display that matches the real world, regardless of meteorological conditions. From birth, humans learn to interact with a three-dimensional world. Replacing a large number of discrete instruments with a Chelton's primary flight display greatly increases situational awareness and minimizes primary causes of accidents, including loss of aircraft control, controlled flight into terrain, and misinterpretation of flight instruments—virtually none of which occur during VFR flight.

Maximize Situational Awareness
The Chelton EFIS utilizes unique symbology designed to give the general aviation pilot the greatest amount of situational awareness. Evidence is overwhelming that the loss of situational awareness plays a dominant role in general aviation aircraft accidents and incidents. The ability to anticipate events and to plan proactively can ultimately determine the success of a flight, especially in an IFR environment.

Minimize Errors and Improve Error Management
The Chelton EFIS symbology minimizes the potential for pilot error and maximizes the potential for recovering from pilot error should they occur. The most common cause of aviation accidents is pilot error. Symbology is designed to minimize the chance of misinterpretation or loss or situational awareness which may cause inappropriate action by the pilot. In addition, upon certain sensed parameters, symbology will adapt to help focus the pilot's attention onto the most critical piloting tasks; vocal and visual alerts are provided to further sharpen the pilot's focus and awareness of critical conditions.

Provide Easy Access to Information
To reduce pilot workload, the EFIS symbology facilitates access to and interpretation of flight-relevant and time-critical information. Additionally, it enables the pilot to quickly locate important information in response to changes in the flight environment. To the extent possible, the symbology integrates data from various sensors into truly useful information, thus minimizing the need for the pilot to mentally integrate information from multiple discrete sources.

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