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Publication Number: FHWA-RD-95-197
Date: December 1996
Development of Human Factors Guidelines for Advanced Traveler Information Systems and Commercial Vehicle Operations: Comparable Systems Analysis
CHAPTER 8. CREW STATION RESEARCH AND DEVELOPMENT FACILITY (CSRDF)
GENERAL SYSTEM DESCRIPTION AND OBJECTIVES
The Crew Station Research and Development Facility (CSRDF) is an Army advanced rotorcraft simulation research facility that supports engineering research and development in cockpit automation and pilot–vehicle interface design. It enables the Army to address issues such as crew complement (one versus two pilots) and advanced cockpit technologies for future aircraft in a full–mission simulation environment (see figure 56). The crew station, with its tandem, two–pilot configuration, is the focus of the system. The full–mission capability is achieved by multiple support stations that enable control of other aircraft, both friendly and hostile, and representation of command, control, and communications. Some of the advanced technology features of the CSRDF crew station include a wide–field–of–view, helmet–mounted display; a high–end image–generation system; advanced digital flight control model; side–arm four–axis hand controller; "glass cockpit" with touch–sensitive control points; speech input and output; and a simulated digital communications link. For the purposes of the present investigation, only a subset of the CSRDF is of interest, namely, the digital map with associated navigation and route planning capability. The ATIS functional characteristics that apply to CSRDF are shown in table 7.
The CSRDF was conceived and designed in 1985 at the NASA Ames Research Center and manufactured by CAE Electronics in 1986. The CSRDF is unique among the systems described in this report in that six of the seven members of the crew station design team had Ph.D.'s in behavioral science and were experienced human factors engineers. The leader of the design team, Dr. James Voorhees, had combat experience as an Army aviator in addition to his background in psychology and human factors. He was able to perform the dual roles of Subject Matter Expert (SME) as well as human factors design leader. This design team was collectively familiar with human factors design guidelines and with developments in the field of human factors research that had not yet been included in standards. In the other systems described in this report, with the possible exception of UMTRI, this level of input by human factors specialists was not available.
The CSRDF, unlike flight simulators that mimic a specific aircraft, is a generic reconfigurable rotorcraft simulation facility. It is routinely modified to accommodate new research needs and to incorporate new technologies. Design flexibility and a reconfigurable cockpit were key design goals.
Navigation is fundamental to the accomplishment of any mission in Army aviation. To date, paper maps have been used as navigation aids. A second crew member is often given responsibility for navigation while the first crewmember flies the aircraft, often very near the terrain. Rogers (1983) and others have found that Army aviators frequently are uncertain of their position using traditional navigation methods. One reason for this problem is that when flying at low levels or at nap of earth (NOE) level, it is difficult to determine current location with respect to the terrain features shown in plan view on a map. Current technology, such as Global Positioning Systems, combined with digital maps, can show the aircraft current location with great accuracy. This is a boon for the busy aircrew and an essential technology for single–pilot operations. The digital map has been used in simulation at CSRDF since its inception and is part of the design for the new Army aircraft, the RAH–66 Comanche, which is currently being developed. It is likely that digital map technology, combined with GPS, will be common in future aircraft as well as ground vehicles.
There are two related, but independent, subsystems associated with navigation and route planning. One is the CSRDF crew station, specifically, the digital map that is the normal mode selection on the pilot's Tactical Situation Display (TSD). The second is an off-line Mission Planner (MP).
Table 7. Comparison of CSRDF functions with those from ATIS/CVO systems.
CSRDF Navigation and Route Planning
The CSRDF cockpit navigation system interface consists of a keypad and a touchscreen CRT in both the front and rear aircrew cockpit positions. In the primary (front) seat, the TSD is located in the center of the cockpit display area. The color digital map shows current location of the aircraft; surrounding terrain; and symbology overlays, including waypoints, the location of known friendly and hostile forces, and tactical areas of interest, such as the Forward Area Refueling Point (FARP) and the Forward Line of Troops (FLOT). The digital map always displays the letter "N" with an arrow pointing North in the upper–left corner of the TSD.
Pilots plan a route prior to takeoff by inserting a series of numbered waypoints onto the digital map. The waypoints are displayed as small octagons enclosing the number of the waypoint. The waypoints are inserted by selecting "waypoint" and then touching the selected location on the map. Numbers are assigned automatically with consecutive waypoint placements. An alternative method for inserting waypoints is to enter the Latitude/Longitude coordinates for a selected location. This method is more cumbersome to enter, but locates the waypoint more precisely than touching the digital map. Turnpoints, which unlike waypoints are not numbered, may also be used to increase the articulation of the route. Once the series of waypoints are established, there is an edit function that allows the pilot to move or erase one or more waypoints to modify the planned route.
In addition to the waypoints, a flightpath can be selected that connects the waypoints with parallel lines depicting a virtual highway over the terrain. During flight, the current location of the aircraft is continually depicted as an "ownship" symbol. At the option of the pilot, a trail of dots is excreted from the ownship symbol on the map to indicate historical position information. Because the planned flightpath is displayed on the digital map, deviations from the planned flightpath are readily apparent by the relative location of the ownship symbol and associated trail of dots. Instantaneous deviation from the planned flightpath is indicated by deviation between the ownship symbol and the flightpath. The ownship symbol is centered laterally on the TSD and located approximately two–thirds of the way down from the top of the display.
Other navigation information, selectable by the pilots, includes current position (Latitude/Longitude coordinates), compass rose, grid (1 km at the lowest two map scales and 10 km at the highest), and heading and distance to any selected waypoint.
A "Mark" feature enables the pilot to locate an "X" on the map at any desired location. This can be used as a reminder to perform some task when arriving at that location or it may designate the potential location of some other entity or item of interest.
The Mission Planner (MP) was a resource intended to be used by engineers rather than pilots. Pilots used the mission planner indirectly, via a software engineer who operated the terminal. The MP ran on a Silicon Graphics Iris machine. The MP system was not designed by a human factors team. The MP software required substantial modification for the software engineers to determine what the pilots said they needed. It had a "terrible user interface" (to quote one of the persons interviewed about this system), was awkward to use, and, hence, has been discontinued.
Despite the interface, the MP did provide some utility. For example, it would plan a route between two points that took into account threat position, terrain type, and type of flight requirements (e.g., low level, contour, or NOE).
Visual Information Display
The CSRDF presents navigation information on the Tactical Situation Display (TSD), a 33–cm color CRT equipped with a touchscreen. The digital map has three scales available (1:50,000; 1:100,000, and 1:250,000) that correspond to the scales used on the paper maps used by Army aviators. The smallest map scale (1:250,000) depicts a large area with rich detail and consequently has a slow update rate, especially during a rapid turn while in the heading–up orientation. A toggle touchpoint switches between north–up and heading–up orientations of the map. A grid overlay can be selected to provide latitude and longitude grid lines over the map. The coordinates of any location on the map can be obtained by selecting "Lat/Long" and then touching the location on the map. A compass rose, centered on the ownship symbol, can be selected for display on the map. These navigation display options were designed for ease of access, enabling a single pilot to fly safely at NOE altitudes while navigating.
The TSD with digital map is located at the center of the cockpit instrument panel, approximately 20 degrees below the top of the panel. The pilot must look down from the outside scene to obtain information from the map display. When flying at NOE, Army pilots want to minimize the time looking in the cockpit, lest they encounter terrain obstacles. The aircraft design attempted to address this issue in two ways: (1) provide essential flight information as symbology on the helmet–mounted display, and (2) provide automated flight control modes (e.g., auto–hover, radar and barometric altitude holds, velocity hold, and turn coordination). The helmet–mounted display symbology enables pilots to perceive basic guidance information such as heading without looking away from the dynamic, out–of–cockpit visual scene. The auto–flight modes, alternatively, enable the pilot to perform tasks inside the cockpit, such as navigation, by reducing the workload caused by the high–frequency, closed–loop flight control task.
The digital map includes terrain features, forests, rivers, lakes, and manmade features such as bridges, roads, towns, and so on. Several levels of detail are selectable. This serves as a "declutter" function. Before flight, each pilot may establish a selected configuration as his or her default. An example might be heading–up, terrain–contours 15.24 m, no grid lines, no compass, show friendlies and show threats. For any reason during the flight, the pilot can modify one or more of these settings, but at any time he or she can return to the selected default setting with one button push. This design effectively allows each pilot/user to establish his or her own declutter technique, and to tailor the information displayed to the changing demands of the mission.
A feature added later to the map display was the capability to slew (recenter) the map to obtain a closeup (Scale = 1:50) view of terrain near the destination or any other area of interest. Simply changing map scale was inadequate because too much detailed information was lost with the "big picture" view (Scale = 1:250,000). The pilot recenters the map by touching any point on the map, which then becomes the new map center (rather than the normal "ownship" location). The pilot can then change map scales to view the area of interest in detail. One human factors concern was that if the pilot was to become distracted at that time, he or she might look down at the map for current navigation information, forgetting that the map had been recentered. This mistake has been observed. It may be prudent to design digital map interfaces to clearly indicate to users when they are in a mode that does not depict their current location.
The accuracy of the navigational information is monitored by the system, and poor input data from the simulated navigation system can be noted by the pilot. Several procedures are available to recalibrate the navigational system by confirmation of current position from outside sources or visual landmarks.
A side view of the map is available. It displays a 5–km radius and moves in concert with the roll, pitch, or yaw of the aircraft. This view, although rarely used, allows the pilot to investigate elevation or obstacle information from the side (perspective) view.
Auditory Information Display
A tone is presented with each input on the touchscreen to provide auditory feedback that the system has accepted the input. Little auditory information is associated with the navigation functions in the CSRDF.
Cautions and warnings are presented by a synthesized speech system. Additional information is presented on displays after acknowledgment of the problem by the pilot. It was thought that anything important enough to be a caution or a warning required audio cues to get the pilot's attention, followed by more specific information presented on cockpit displays when selected by the pilot.
User Input (Controls)
User input to the navigation system in the CSRDF cockpit is accomplished primarily by the TSD touchscreen. An alternative interface is provided by a second control/display unit called the Systems Management Display (SMD), which provides a hierarchical data entry format. The SMD is often used for pre–mission system setup. The digital data entry is slower, but more precise, than the digital map touchpoints provided on the TSD. Pilots rarely use the SMD when airborne, particularly when flying single–pilot operations (i.e., when flying solo). The touchpoints on the TSD can be accessed much more quickly. Entry of a waypoint, for example, would take two touches on the TSD or approximately 10 button presses on the SMD.
One design goal was to enable the user to access any cockpit function within three levels of a menu hierarchy. The design team felt that more than three levels would be difficult to use and would require more training to "navigate" through the hierarchy.
User input to the Mission Planner (MP) was through a system expert. The system expert interacted with the MP via a keyboard and a mouse.
The CSRDF cockpit has the ability to simulate all forms of communication that are typical of contemporary Army helicopters. Voice, encrypted voice, and data link technologies are fully simulated.
One aspect of the communications system is linked to the digital map display. Pilots can select one of three radios and tune it to the proper frequency simply by touching the appropriate "friendly force" icon on the digital map. This feature facilitates communications and reduces pilot workload. It does, however, require that the radios and frequencies be assigned in advance to the friendly forces.
Aircrew workload is exceedingly high in a night, adverse weather mission into hostile territory. Part of the rationale for procuring the CSRDF was to enable the Army to address issues of pilot workload in an environment that would enable control over tactical and environmental factors that influence workload. The CSRDF cockpit was designed to enable rapid access to the functions provided by advanced technology. The digital map and associated navigational features represent a central part of the theme to reduce pilot workload to acceptable levels under difficult circumstances. The initial issue to be addressed by CSRDF was whether advanced technology could enable one pilot to accomplish such a mission. The one– versus two–crew decision has large cost implications over the life cycle of an aircraft.
It was a design goal to prevent information overload by limiting the type and amount of information routinely displayed to the pilot. Instead, pilots were given the option to increase or decrease the amount and type of information displayed in different sub–systems, such as navigation information, display of grid lines, density of contour lines, and distance and direction to waypoints. Pilots can select any one or all combinations of three overlays and, on two of the overlays, they can select from several levels of information to be displayed.
Previous research on Army aviation indicated that navigation is not only difficult, but often unsuccessful. Studies leading to guidelines for the design of digital maps found that "descent to NOE flight levels greatly increases the likelihood of geographic disorientation due to the aviator's limited view of [geographic] checkpoint features useful in navigation." And further, "both anecdotal evidence and controlled field tests have indicated that the percentage of NOE sorties in which the aviators experience no navigation problems and remain well oriented throughout the flight is exceedingly small" (Rogers, 1983).
The digital map as implemented in CSRDF has virtually solved that problem. It has been easy to learn, easy to use, and dispenses with the need to fumble with paper maps while flying at low levels. Location error becomes a matter of error or drift of the navigation and position–determining equipment, rather than pilot confusion about the identity of geographical reference points. The digital map may be the single most effective technology included in CSRDF with respect to the reduction of pilot workload and successful mission accomplishment.
System Temporal Requirements
The update rate of the map display must be adequate to provide information that is perceived as being current by the pilot. The latency that is perceived as being "current" by the pilot depends, at least in part, on how accurately the pilot can relate the position of the aircraft on the display with what is seen in the out–of–cockpit visual, and the required precision of the task.
Large demands are put on the digital map system when operating in the heading–up orientation, which seems to be preferred by the majority of pilots in CSRDF. In addition to "heading up," other pertinent variables are map scale, aircraft dynamics, and the richness of the terrain features at the location. The worst case is:
The capability of the digital map system to update smoothly can be exceeded under this combination of circumstances. This problem leads to a series of apparent rotational "jumps" in the map. Future increases in computational speed and capacity are likely to meet this challenge, but the design goal should be to achieve smooth and accurate map representation even under the most difficult conditions.
DESIGN GUIDELINES USED
Human Factors Design Guidelines
General human factors design guidelines were available, but seldom used by the system designers who had backgrounds in behavioral science and human factors engineering. Few guidelines were available for development of the digital map display other than the prior work by Rogers (1983).
MIL–STD 1472C was available to help define the physical characteristics of the cockpit displays, such as size of soft keys and minimal separation between soft keys. Also, the use of color in the CRT displays was carefully considered by the professional psychologists involved who had considerable background and understanding of the limitations and usefulness of color in CRT displays (e.g., Hennessy, Hutchins, and Cicinelli, 1989).
Human factors design guidelines and reference materials were not consulted systematically during the design of the CSRDF. However, the individual design team members may have made use of standards and current research results in formulating their design recommendations. Two members of the design team had previously published general design guidelines for speech input/output systems (Simpson, McCauley, Roland, Ruth, and Williges, 1987).
Specific functions performed by the CSRDF cockpit interface were decided by the designers involved at the beginning of the project. They took into account their knowledge of Army aviation requirements, available technology, human factors and research psychology tenets, and user interviews.
Designers consulted available Army aviation manuals and documents to provide additional background for user needs. However, most of the systems modeled were new technology and had no supporting documentation or guidelines associated with them.
Army aviation manuals, helicopter operations manuals, and communications systems manuals were used as background for decisions on symbology, color meanings, and nomenclature.
Route guidance information was determined by expert opinion about what an Army helicopter pilot needed to do the job. The design team chose to display planned path and actual path differently so that the pilot could see his or her deviations from the planned ground track. CSRDF provides no information to the pilot concerning steering cues to get back on route. However, more recent systems (e.g., Comanche helicopter) do provide this information, and the capability may be added to the CSRDF.
Standard Army aviation symbols were used for most icons displayed. For information that had no standard symbols, icons were developed for simplicity and associative value with the information to be presented. Text size is large enough to be legible, but small enough to not obscure too much information on the map itself.
Effectiveness of Human Factors Guidelines Used by System Designers
The standard human factors guidelines were rarely referred to during the system design. The reasons for this are twofold: (1) the systems were advanced, notional technologies, for which no previous experience was included in the guidelines; and (2) the design team was very familiar with human factors principles without looking at the guidelines. Also, the CSRDF was software–intensive and modifiable, rather than being a fixed–point design intended for production. The design team believed that their best efforts would probably surpass the standard human factors design guides, and, if they were wrong, it would be a relatively straightforward task to modify the interface characteristics in the future.
[CS 01] DIGITAL MAP HELPFUL FOR NAVIGATION AND ROUTE FOLLOWING
[CS 02] MAP ORIENTATION DEPENDS ON APPLICATION MODEðC PRE–MISSION PLANNING OR EN ROUTE
[CS 03] POOR USABILITY OF A USER INTERFACE LEADS TO DISUSE
[CS 04] INTERFACE "MIDDLE–MEN" ARE UNACCEPTABLE
[CS 05] IN–VEHICLE DIGITAL MAP CAN PREVENT BEING LOST
[CS 06] ROUTE PLANNING BY WAYPOINTS IS SIMPLE
[CS 07] ROUTE CAN BE DEPICTED BY PATHWAY LINES
[CS 08] MAP SCALE/SLEW FEATURES CAN LEAD TO MISINTERPRETATION OF CURRENT POSITION
[CS 09] SYSTEM STATUS INDICATIONS ARE ESSENTIAL
[CS 10] THE OPTION OF TWO INPUT METHODS FOR SPEED VS. PRECISION CAN BE A GOOD DESIGN FEATURE
[CS 11] INTEGRATE ROUTE PLANNING AND GUIDANCE FUNCTIONS
[CS 12] TOUCHSCREENS CAN SUFFER FROM DEGRADATION
[CS 13] TOUCHPOINT FEEDBACK ON TOUCHSCREENS IS VALUABLE
[CS 14] DISPLAY UPDATE RATES MUST BE SUFFICIENT FOR THE APPLICATION
[CS 15] ONE–TOUCH DESIGN FOR IMPLEMENTING A COMPLEX, MAP–ORIENTED FUNCTION
[CS 16] COMMUNICATIONS FROM THE VEHICLE CAN BE EXPEDITED BY MENU–BASED, CONTINGENCY–SEND MESSAGES
[CS 17] EMPHASIS ON HUMAN INTERFACE DESIGN YIELDS A HIGHLY EVOLVED USER INTERFACE
[CS 18] SUBJECT MATTER EXPERTS ARE ESSENTIAL FOR SUCCESSFUL SYSTEM DESIGN
[CS 19] ITERATIVE TESTING AND RAPID PROTOTYPING SUPPORT CONTINUOUS REFINEMENT OF THE SYSTEM
[CS 20] MEASUREMENT OF HUMAN AND SYSTEM PERFORMANCE IS ESSENTIAL FOR SIMULATION AND SYSTEM DEVELOPMENT