DISPLAY DESIGN EXERCISE: F-16 UPFRONT CONTROLS (UFC)
Xxxxx X Xxxx (Contact me if needing reference)
Display Design Exercise 01 for Course ASCI 604 Submitted to the
in Partial Fulfillment of the Requirements of the Degree of
Master of Aeronautical Science
Embry-Riddle Aeronautical University
Giebelstadt Resident Center January 2004
Xxxxx X Xxxx (Contact me if needing reference)
Display Design Exercise: Upfront Controls (UFC)
Embry-Riddle Aeronautical University
Master of Aeronautical Science
The creation of the F-16 introduced the impressive fly-by-wire flight controls it soon become famous for. In its early years of operational capability, however, it was evident this jet offered much more - powerful and expansive hands on throttle and stick (HOTAS) controls and consolidated upfront controls. Comprised only of a standard keypad (with some supplemental switches) and a small display - the DED - these controls forever changed how a fighter pilot conducted both routine and critical tasks. Responsibilities such as changing radio and TACAN stations, modifying target coordinates, and even vital INS corrections could now be done quickly in one central location. No longer was the pilot required to make switch changes throughout the cockpit, and any task that could be done digitally, was. The ICP and DED are effective and easy-to-use displays, but have continued to suffer from some distracting software inconsistencies and the repercussions of begin designed for a day, VFR fighter - the original intent of the F-16.
As the 70s drew to a close, the revealing of the F16 Fighting Falcon by General Dynamics introduced the world to a new breed of aircraft - what has become known as the ‘electric jet’. The phrase described a unique trait of the F16 - it “was the first operational jet fighter to use an analog flight control system” (Day, 2004). This flight control system keeps the inherently unstable aircraft stable (low stability is conducive to high maneuverability and vice versa). This innovation is what coined the phrase, but the F16 also brought with it many new display and pilot interface ideas. After about five years of production, the F-16 transitioned from the A/B models to the C/D models - B and D are two-seat versions (Dewitte and Vanhastel, 2003). In these models, the Heads Up Display (HUD) was now accompanied by a fresh idea that distinguished the F16 from any other fighter - the Integrated Control Panel (ICP) and its associated Data Entry Display (DED).
Together, the ICP and the DED are called the Upfront Controls (UFC) and they “provide a simplified, centralized, head-up means of controlling the most frequently used functions of the communications system, navigation systems, IFF (Identification, Friend of Foe), [and much more]” (T.O., p. 1-148, 2001). Like many displays, the UFC has limitations any ways exist to make it a better interface. Overall, however, the UFC revolutionized pilot-to-jet input by condensing system control, easing data modification and minimizing heads-down time in the cockpit.
To best understand the UFC, the components and how they interface with the pilot operator, a brief description of the DED and ICP is required. Next, the display will be analyzed from a human factors perspective and finally, recommendations are provided.
Although there are several ways to input data into a display (or take data away), there are basically only two means of connecting the interface device and display - remotely or directly. Examples: televisions - direct via buttons or remotely via remotes; computers - remotely through a keyboard (while connected physically, it’s still remote) or directly on the touch screen of a PDA. Similar to the keyboard/computer arrangement, the DED is manipulated remotely through the ICP. The ICP does not move and is directly below the HUD, but it is not physically part of the DED (Figure 1).
The DED is located just right of the ICP and slightly further away from the pilot. A switch on the HUD control panel allows the pilot to display “DED DATA” (a standard practice) and any information displayed in the DED is also repeated in the bottom center of the HUD.
Integrated Control Panel (ICP). The ICP is essentially a keypad (arranged in the phone vice calculator layout) with some additional function keys and a joystick-like switch called the data control switch (DCS). The DCS can be moved up, down, left and right and is the switch marked “RTN” and “SEQ” on the left and right respectively in Figure 2 below.
Two gray spools are on the left and right edges of the ICP. However, only the top one on each side is used - left side turns on HUD symbology and controls its brightness; right side adjusts a stand-by bombing reticle.
The six buttons arranged at the top are ‘override’ buttons and the first four, COM1, COM2, IFF and LIST are used the most often. They are called override buttons because they take you to their respective screens or ‘pages’ on the DED (more on these pages below). Another common key is the “ENTR” key just right of the keypad. This key either selects highlighted options or accepts data you’ve entered with the keypad. The numbers in the keypad also serve as direct links. The “2” key, for example, not only enters 2 into data fields, but will take the user to the “ALOW” page where certain settings can be made to the auditory warning system.
The last of the frequently used switches are the three just below the keypad. The rocker switch marked only with up/down arrows is the increment/decrement (INC/DEC) switch. This switch increases/decreases a variety of items, but is usually used in conjunction with changing steer points (STPT) for navigation. The DCS (joystick switch mentioned above) is used so often, it borders on abuse. This switch moves the cursor around the DED, cycles through available options and acts as an ‘escape’ key - returning the user back to the previous screen.
Date Entry Display (DED). The DED alone is rather small and blasé. With the ICP, however, the DED becomes an integral part of the upfront controls and provides a ‘window’ to all available pages and switch actions.
The most common DED page is shown in Figure 3. The CNI (communication, navigation and IFF) page is the ‘home page’ of sorts and is the standard page to have displayed. It is very useful as it shows more than ten important pieces of information in one glance. Furthermore, since most pilots repeat the DED in the HUD, this data is now available for review after a sortie in the HUD videotape. As a highlight, the pilot can see the settings of both radios (UHF and VHF), the code of Mode 3, enabled IFF codes, the steer point which the navigation system is currently using, wind speed and direction, the system time, a running time hack and the TACAN the jet is receiving.
This page offers a good example of using the joystick-like DCS and the INC/DEC rocker switch. In the upper right corner of Figure 3, there are two arrows (up and down) between “STPT” and “12”. This informs the pilot that the STPT would be increased or decreased using the INC/DEC switch. Moving the DCS up or down will continue to cycle these two arrows next to “UHF”, “VHF” or “STPT”. So, a quick DCS down and INC/DEC up would change the VHF present from 10 to 11. In other words, the DCS down moved the two arrows next to “VHF” and the INC/DEC up increased the 10 by one.
Figure 4 shows the LIST page. There are too many DED pages to explain in this forum but Figure 4 helps explain the levels of available pages. This page is accessed with the “LIST” override button (fourth one in top row of six) and opens a variety of choices. Each selection is a page for data entry and/or deeper menus. For example, pressing “2 BNGO” opens the “Bingo” page on which the pilot can adjust when an auditory “Bingo, Bingo” is heard. Selecting “0 MISC”, on the other hand, opens another menu page with even more options. A comparison can be made to modifying the title of a Word™ document. Windows Explorer™ is similar to the CNI page and the document resides somewhere in the file structure. Clicking “My Documents” opens several options - some are documents where edits can be made directly, and some are folders with more choices. The location of your document will dictate how many options you must select before finally changing the title. Once you’ve changed the title and exited Word™, you return to Windows Explorer™ (your CNI page).
ICP Layout and Position. The layout of the keyboard is the similar to that of a telephone (as opposed to a calculator) where the 1 is in the upper right corner of the arrangement. People easily adapt and become familiar to both arrangements and without direct contact with the engineers, it would be difficult to speculate why General Dynamics (at the time) chose this layout. It was, however, a good design as the standard has become the telephone layout, and according to a 1960 study conducted by Bell Labs, “it was determined…the three-by-three matrix that had 1, 2 and 3 across the top was the easiest for people to use” (HowStuffWorks, 2004).
The ICP made an interesting departure from the pure telephone layout. On a telephone, the zero makes the fourth row with an asterisk to the left and a pound symbol to the right. On the ICP, the overall arrangement is a four-by-three matrix with the zero directly right of the nine and a “RCL” (recall) and “ENTR” (enter) stacked above the zero. Humans use the computer keyboard and telephones everyday and have the impressive ability to switch back and forth with ease. The ICP is slightly different, but with minimal exposure and practice the offset zero is readily accepted - just as it would have been if a true telephone arrangement were used.
The ICP is physically closer to the pilot than any other display on the center console and it falls just below the line of sight through the HUD.
This location has some critical advantages. First, it is very easy for pilots of any size to reach, which is extremely important since it’s used throughout flight. This is in contrast to the multi-function displays (MFD) which are several inches further away and force some pilots to lean forward. The left MFD is to the lower left of the ICP in Figure 5 (half of it is visible). Second, the sides of the ICP provide a good place to rest the four fingers or the left or right hand while the thumb manipulates the keypad - providing the sensation that you’re holding or squeezing the ICP in your hand. This is further supplemented by the fact that the keypad is not centered. Placing the keys closer to the left affords the user easy reach to the entire keypad using only the left thumb. At first this might seem less flexible since the keys are further for the right thumb, but the stick is much more critical to have hands on then the throttle. As a reminder, the F-16 has a side-stick controller so using the ICP with the left hand feels very natural. The DCS and INC/DEC switches which are used extensively are also located on the left half of the ICP, making them very accessible. Finally, the tendency is for the hand to drop before returning to the throttle or stick. Not only is the DCS placed on the left half, it is at the bottom so it lies in the path of the returning hand. This is a good position since the DCS is used to return to the CNI page, and more so, pulling it left activates the return function. One smooth motion allows data verification/entry, DCS back to the CNI page, and a fluid return to the throttle.
DED Screen. Together, the DED and ICP comprise the upfront controls, but as the DED is physically separated from the ICP, it almost appears an afterthought. Whether that is the case or not, the DED is overall a very good display and has proven itself over time. “It has been in production for over 15 years, with over 6,000 produced to date. The DED [is] a 3” x 1” matrix LED display [and] sunlight-readable” (Northrop Grumman, 2003). The matrix LED is a nice departure from line displays and makes it similar to text in bold font - easier to see at a distance. The DED is also fully compatible with night visions devices and does not drown out night vision goggles.
The arrangement of data on the DED screen is very straightforward and plain text is used whenever possible. However, some selections continue to advance to more and more sub pages. This can cause the user to forget which page they started with since there is no indication of the previous or parent page. Also, it’s difficult to determine which fields are pure data entry fields (where numbers are typed and entered) and which fields have preset, selectable options. Available options are viewed using DCS right - marked ‘SEQ’. Usually, fields that have selectable options will be displayed with the current or default selection but it is not always the case, and data entry fields may also display the last entry - making both fields appear the same. The best determining factor is text vs. numbers. Text usually indicates selectable fields while numbers tend to indicate fields in which data can be typed. Furthermore, some fields stand-alone but modify other fields on the page, which can be very confusing. This is best explained with a graphic. Figure 6 shows the DED page used to change TACAN channels, ILS frequencies and ILS final courses. Also shown is the asterisk-square (AS) bracket indicating the field of interest (the field to be modified).
When selecting the TCN/ILS page, the AS bracket is located just left of “CMD STRG” as shown. For the scenario, assume a pilot wants to change the TACAN channel from 24 to 35. Using the design of most pages, a pilot may attempt to DCS down (or up) to the “CHAN” field. DCS down, however, jumps the user to the “CRS” field. The page is structured to accept integers as changes to the TACAN. For the example, the pilot doesn’t move the AS bracket at all, but simply types “35” and presses ENTR on the ICP. The new value will replace “24” and the bracket remains in the same location. To change the “CRS” value, a DCS up or down is required. This scheme is not parallel to other pages and can delay changing the TACAN station.
Despite this example, the asterisk-square bracket is a good system for indicating the field of interest since this symbol isn’t used elsewhere in the DED. The bracket is moved around the screen by pressing the DCS up or down. DCS down will advance from one modifiable field to the next down the screen and DCS up will start at the bottom of the screen and advance up the screen. DCS up can be useful when modifying a field on the bottom of a screen with many fields. Herein lies another non-standard characteristic. Some screens have fields that initially appear unchangeable because the cursor will skip them if DCS down is used. DCS up, however, allows the cursor to enter that field and modifications can now be made. There is no indication of this on the DED page itself and is recognized only through practice and/or good briefings.
DED Location. As seen in Figure 7, the DED is located to the right and slightly aft of the ICP (the DED is not illuminated in the right view). Although the DED is recessed approximately six inches, the pilot’s cranium is far enough away and the ICP does not impede viewing the DED. Also, placing the DED under the right glare shield creates a darker environment, which in turn makes the display easier to read in daylight. Additionally, the DED is simply a display and only modified through the ICP so a hands-on capability is not required.
Lighting. The DED is close to the HUD and is almost always in your peripheral vision so the intensity of the lights is very critical - especially at night. An excellent part of the DED design is a dedicated rheostat on the light panel for the DED's brightness (Figure 8, upper right corner). During the day, the highest brightness setting overcomes sunlight directly hitting the DED. Also, the rheostat is very sensitive so it is easy to adjust the DED to a lower and lower setting as the eyes get adjusted to dark environments.
Unlike the DED, the ICP is not internally lit and gets illuminated with other components of the console. These rheostats, marked CONSOLES and INST PNL, are also visible in Figure 8. Different from the DED, these are not very sensitive and it can be difficult to make small changes. Obviously, this is a non-factor during the day, but is at night - to the point of becoming a limitation. With or without night vision goggles (NVG), it is a challenge to make the cockpit as dark as possible while still retaining some level of usable light. Without NVGs a higher setting on the console lights is acceptable since vision is seldom the sole receptor - almost every phase of a mission is system aided. However, when using NVGs, the situation is not only worse, it is unacceptable. At the lowest setting, these lights emit too much ‘white’ light which is not compatible with NVGs and if left on will drown or ‘wash out’ the NVG picture. The situation was bad enough to warrant a modification. Two NVG-friendly lights were attached to both sides of the ICP that can be positioned in different locations and are secured by Velcro. The pilot does his or her best to manipulate the lights on the Velcro to get the best illumination of the ICP. It is important to remember the ICP is used extensively on each flight and in every phase of flight - including ground operations. If poorly lit, a pilot may be hindered when making time sensitive adjustments to system settings, suffer additional (and unnecessary) stress and the overall workload is increased. For example, prior to weapons release, several screens of the DED and MFDs must be checked to confirm critical data and time doesn’t always exist to fumble through DED pages. Also, NVGs already induce additional physical stress due to extra weight and pressure on the neck and face. This is compounded if the operator has to continually lean forward in order to better see the ICP keypad. NOTE: If a jet has been fully modified to be NVG compatible, the problem of 'white' light is eliminated, but a reliable light source on the ICP itself is still lacking.
DED and HUD Relationship. Explained earlier, the HUD has the ability to repeat the DED information in the lower center of the display. This is not only useful for data in the review of post-mission tapes; it adds some additional features to the DED. First of all, the HUD doesn’t simply repeat the DED display - it repeats the DED data - therefore, an additional level of redundancy is provided in the event of DED failure. The data will still be passed to the HUD and this now becomes the primary DED. Also, when the pilot keys the UHF or VHF radio, the HUD increases the font of ‘UHF’ or ‘VHF’. This can be used to confirm a transmission was made or at least attempted. The HUD does the same to the IFF Mode 4 when interrogated.
An interesting phenomenon exists when pilots use the ICP. Although the DED data is displayed directly in front of the pilot and above the ICP (in the HUD) pilots tend to exclusively look to the right at the actual DED. This can most likely be attributed to the brighter, easy-to-read DED display, habit and display familiarity. As an example, the pilot expects to see certain things highlighted on different DED pages. This highlighting becomes a familiar picture to the pilot and helps locate different fields. Highlighting in the ‘HUD DED’ is absent and pages that are otherwise common now require additional processing time.
As a whole, the DED and ICP are extremely reliable, simple and easy to use displays. The DED is readily visible in almost any light condition and arranges data in an intuitive manner. Also, the DED is essentially unlimited in what data is displayed - the display size can’t be changed without an aircraft modification, but pages could be modified, added or removed an infinite number of times. The biggest detraction is the existence of inconsistencies between pages. These are few in number, however, and with practice become almost unnoticeable. The differences would most likely affect new users, those transitioning from other airframes and familiar with different systems, or pilots who have been removed from the cockpit for an extended amount of time.
The ICP has also continued to prove itself a simple, rugged display for over 20 years. Other than the placement of the ‘zero’, the keypad follows a standard layout, and the entire keypad is relatively easy to reach from the left side. The DCS alone is an ingenious switch. Not only tactilely comfortable, it is an extremely effective and instinctive way to move around a screen, switch screens, cycle through options and return to the CNI page. The most significant limitation is not the layout or function of the ICP, but rather the lighting of the panel. Even if the original lighting is used, it is marginal at best and difficult to adjust. With an increase of night flying, the lighting has essentially been rendered useless. The ICP is a critical part of the cockpit and proper illumination is an absolute necessity. As mentioned, modifications have been made to improve the situation in the night environment.
Lighting. Part of the current modification to make an F-16 night vision capable includes the aforementioned adjustable lights. It also involves the addition of a hood - or ‘mini’ glare shield - affixed to the top of the ICP and extending toward the pilot approximately three to four inches. This hood helps prevent a glare on the HUD from the ICP lighting. In reality, the hood better serves as the place to secure the adjustable lights so they can actually direct light on the ICP. Also, pilots frequently wear finger lights (Figure 9) which are very helpful since the index finger naturally directs the light on the ICP anytime it’s used.
Although the modification works, it involves extra, unnecessary pieces of equipment. A better solution could be found with internal ICP backlighting. Illuminated keys on laptops or telephones (both mobile and home) are good examples of existing technology that could be transferred directly to the keys of the ICP. For the other switches such as the DCS and WARN RESET, two options are very feasible. First, the labels on the switch perimeter could be made translucent or semitransparent. A second option could replace the switches with a very durable, light diffusing plastic. Both options would take advantage of the same light source for the backlighting, but the first option would be most conservative - each switch location is labeled so no confusion arises in time-critical situations. Like the DED, the lighting modification should also include the addition of another highly sensitive rheostat on the interior lighting panel dedicated to the ICP backlighting.
DED Standardization. The fact that the DED is simple, easy to interpret and almost exclusively text-based, it doesn’t really require modification. On the other hand, with a few minor adjustments to program code, each page could respond identically to ICP input. First, each field that can be modified should be accessible regardless if DCS up or down is used. Second, blank fields should be omitted and instead, the AS bracket should default on the most-used field of each page. Referring back to the earlier example, the AS bracket would no longer appear on an empty field on the TCN/ILS page. Rather, it would be on the TCN CHAN field - the most common of that page. Thirdly, the fields with preset choices (those not accepting data entry) could be better differentiated from data-entry fields. A variety of techniques could be used and one possibility is to outline these fields with a box once the bracket is moved there. Also, any selectable field should be done exclusively via a DCS right movement (marked SEQ for sequence) followed by a DCS left (RTN for return) or the ENTR key on the keypad. This would eliminate confusion between the Zero key on the ICP and the SEQ option of the DCS. The Zero key is also labeled ‘M-SEL’ for mode select. Confusion arises because some DED options are selected with the Zero / M-SEL key while others are selected via DCS right (sequence).
ICP Layout. The ICP layout could be enhanced with a minor rearrangement of the keypad and priority, or override buttons. Figure 10 shows the current ICP (L) with an alternative design on the right.
FIGURE 10. F-16 ICP (left) and ICP-X (right)
Keys 1-9 are arranged in the telephone style layout, but the zero is placed to the right of the keypad. Centering the zero under the eight not only standardizes the keypad, it brings the zero closer to the left thumb. Also, the zero could be bracketed by RCL and ENTR similar to the asterisk and pound symbol on telephone keypads. RCL is used for recalling previous data entries, or correcting invalid entries. Placing RCL on the left makes it similar to RTN, which is on the left of the DCS. Placing the ENTR on the right places it directly above the DCS. This is useful since several options selected via the DCS require acknowledgement with ETNR - now quicker to reach.
The location of the six priority
buttons on the top of the ICP could remain the same, but this would require a
larger (in height) ICP. The ICP could
remain the same size if the six buttons are relocated to the right of the
keypad - as shown. Of these six buttons,
COM 1 and COM 2 are used the most since they change the UHF and VHF frequencies
respectively. However, these buttons
and the remaining four are all single-push buttons - their only function is to
display a specific DED page. After the
page is shown, the pilot must resort back to the keypad to enter/change any
data. It is simple (and typical even in
the current ICP layout) to press these buttons with the index finger before
resting the hand on the left of the ICP for data entry. Ideally, the height of the ICP would be
slightly increased to leave the six buttons across the top and incorporate the
new keypad layout. This would better
accommodate long-formed habits and keep COM 1 and 2 closer to the thumb if the
hand were already resting against the ICP.
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