With stealth, fully integrated avionics, advanced sensor fusion, and a dizzying array of interoperability and data-exchange requirements, the F-35 Joint Strike Fighter represents more revolution than evolution. Nowhere are the advances in this multirole combat fighter more starkly illustrated than in the cockpit.
What is not there is what is most evident to pilots the first time they see the F-35 cockpit. Gone are the analog steam gauge dials that populated the control panels of previous generations of fighter aircraft. In their place are large liquid-crystal touch-screen displays featuring color-coded symbology, pictographs, and digital information.
Changing the displays is only a matter of pressing a finger on different parts of the screen of the multi-function display, or MFD, to reconfigure or prioritize information or activate systems. The forest of toggle switches in previous fighter cockpits has been wiped clean from the F-35’s interior landscape, with most of their functions moved to the touch screen. A few switches still sprout here and there, but the overall cockpit ambience is one of simplicity and calm, almost to the point of aeronautical feng shui.
Similarly, the cockpit of the F-22 Raptor offers a trio of glass displays. “Those displays represent a significant step toward the F-35 cockpit’s spare ambience and a departure from its steam-gauge predecessors,” notes Jon Beesley, the chief test pilot for the F-35. Beesley should know. As a veteran of advanced aircraft development programs, he served as a US Air Force test pilot on the F-117 stealth fighter and as a General Dynamics test pilot for the YF-22. Beesley was the fourth pilot to fly the YF-22 and second pilot to fly the F-22. “The F-22 prototype, the YF-22, had finger-on-glass controls as well,” Beesley notes. “We learned a lot from the experience with this technology on the prototype, which was not implemented in the production F-22.”
The F-22 Raptor is equipped with four reconfigurable liquid crystal displays — three 6.5 by 6.5 inches and one eight by eight inches — along with two non reconfigurable three- by four-inch up front displays. “They are a real advance from the past,” Beesley explains. “But the F-35 is the ultimate expression of the less-is-more sensibility.”
Beesley’s initial reaction to the F-35 cockpit is shared by many other seasoned pilots who see the cockpit for the first time. “Pilots are most impressed by the minimal number of hard switches in the F-35 cockpit,” he explains. “The most prominent portion of the cockpit is the eight- by twenty-inch LCD controlled primarily using finger-on-glass technology that has matured tremendously over the last several years. In the pursuit of easing pilot workload, advanced technology takes care of what pilots refer to as housekeeping chores.”
For example, finger-on-glass controls replace cockpit switches for selecting such functions as air refueling mode and flight control system tests. All radio, mission systems computers, and identification and navigation controls are on glass.
Beesley notes that the large eight- by twenty-inch multifunction display (created by combining two eight- by ten-inch displays) can be customized and divided into many different-sized screens through what he describes as an “elegant pilot-vehicle interface design.” By touching the screen, the pilot can select a pair of eight- by ten-inch window displays, or four five- by eight-inch windows, or any combination of window sizes to project information based on its importance at any given moment.
“This ability to control formats eases the interpretation of complex data,” adds Beesley. “The flexibility in display size and the diversity of data are not available in any other fighter aircraft.”
If one of the eight- by ten-inch screens fails, all information is automatically transferred to the other eight- by ten-inch screen. At the same time, this second screen remains fully customizable. “The missions for the F-35 can be some of the most complex fighter missions conceivable, varying from air superiority to close air support, to the destruction of enemy defense systems,” Beesley explains. “Well-thought-through pilot-vehicle interface makes the transition from one type of cockpit mission to another type of cockpit mission very natural, effectively reconfiguring the cockpit at the same time. Pilots adapt to the concept quickly.”
Rather than evolving the F-35 cockpit from previous designs, engineers decided to start with a clean sheet and base the cockpit’s architecture solely on the needs of the 21st-century fighter pilot. Instead of presenting the pilot with acres of gauges representing all systems and situations all the time, engineers gave priority to situational awareness and to ensuring the information — not just raw data—the pilot receives is the most pertinent for any given moment.
“The F-35 cockpit design is driven by the desire to return the pilot to the role of tactician,” says Mike Skaff, a former US Air Force F-16 pilot who serves as senior manager of the team designing the F-35 pilot-vehicle interface. “Modern fighters are amazingly complex. Monitoring the status of aircraft systems can divert a pilot’s attention from information more critical to the mission. The F-35 cockpit is designed to ensure that the pilot can focus on getting the job done without having to worry too much about other tasks.”
Beesley, whose résumé includes more than 5,000 hours of flying time in twenty different fighters, has already logged hundreds of hours in F-35 cockpit simulators. More recently, he is spending more time in the actual first F-35A test aircraft, known as AA-1, as its first flight approaches. The cockpit appearance of AA-1 is essentially the same as that of all subsequent F-35s. The handful of AA-1 features that won’t make it to production include a pair of electrical system emergency switches, an instrumentation control panel mounted in the center pedestal, and a small digital readout of tactical air navigation information required for AA-1’s unique communications, navigation, and IFF equipment.
“In past programs, controls unique to flight test, such as flutter excitation, control change evaluation, and flight test maneuvers, were selected through panels and switches,” continues Beesley. “On the F-35, these controls have all been incorporated into a display format that can be brought up on any of the LCD screens. We’ve incorporated numerous lessons learned from previous programs on the layout of these displays and on the operation of these flight test critical controls. We engage and terminate various modes using the controls on the hands-on throttle and stick, or HOTAS.”
The three F-35 variants share identical cockpits but with one functional difference. The conventional and carrier variants provide a button to drop and raise the arresting hook for carrier and emergency landings. The STOVL variant commands conversion into and out of the STOVL propulsion mode.
The engine throttle on the pilot’s left and the side stick on the pilot’s right are positioned to be compatible with the widest possible range of pilot shapes and sizes. The throttle is designed to give pilots the capability to vary the detents. It is also an active throttle, which means it provides feedback to the pilot as a function of flight envelope and flight mode. The side stick is also an active controller.
“Stick forces and deflections can be programmed in an active stick to allow either a slight increase or decrease in stick force while pulling g’s,” Beesley explains. “The real driver for an active stick was for vertical flying conditions on the F-35B, or STOVL, variant where we thought we would need light stick forces. In fact, we haven’t needed the feature so far. We have put detents in the STOVL stick. We use a soft stop detent to indicate the desired touchdown sink rate in the STOVL mode.
“The throttle uses the active controls to a greater degree,” Beesley continues. “The internal motors allow the throttle to be moved back automatically when the pilot has an auto throttle connected or in some of the STOVL modes allows the option to input soft stop detents and afterburner detents at will.”
One unique feature of this active throttle is that it does not have an engine cutoff position. It has, instead, a single toggle switch to cut the engine. The use of the active stick and throttle and a cutoff switch was introduced on the JSF demonstrator, the X-35.
Pilots have guided the F-35 cockpit design process from the very beginning to ensure the fighter’s front office is an efficient workspace that liberates the operator from unwanted distractions. “The design has been driven entirely by current and former military pilots from the US Air Force, Navy, and Marines as well as current and former military pilots from the United Kingdom, Canada, Denmark, Norway, the Netherlands, Italy, Turkey, and Australia,” Skaff says.
One of those military pilots providing direction is Lt. Col. Jeff Karnes, a Harrier pilot who is currently flying the F/A-18 Hornet for the US Marine Corps. He is a member of the exclusive fraternity that is both shaping and testing the F-35 cockpit. “The twenty- by eight-inch display provides expansive tactical workspace for manipulating the system and for segmenting down to twelve individual displays,” he says. “It places navigation, threat warning, target designation, and ordnance displays together for quick reference. The Joint Strike Fighter has been specifically designed to reduce pilot workload by minimizing cockpit switches, increasing system automation, and reducing displayed information to only critical items the pilot requires to complete current tasks. The active stick and throttle allows realtime control shaping to optimize feel and aircraft response as a function of current flight envelope and mode.”
Text and symbology on the MFD are color-coded to contrast clearly and sharply with the absolute black of the display screen background. Bob Russell, who manages simulations for the team integrating F-35 pilot systems, simplifies the significance of the colors. “In general, green indicates good or safe conditions, yellow indicates potential problems requiring pilot attention, and red indicates serious conditions demanding immediate pilot attention,” he says. “For example, text for advisories appears in green, cautions appear in yellow, and warnings appear in red.”
The same color codes apply to exterior objects, other aircraft, and phenomena detected by the F-35’s sensors. Symbols on the tactical display appear green if the aircraft’s sensors or off-board assets determine these objects are friendly. If unknown to the sensors, objects appear yellow. If identified as potential adversaries, objects appear red. “We also use blue and magenta, but sparingly,” adds Russell. “We use shades of gray to outline maps and to outline the aircraft planform shown on various subsystem formats, such as fuel, flight controls, and weapons. The symbols representing air and ground threats appear in different shapes that, along with the colors, enhance the pilot’s comprehension and situational awareness.”
Among the other cockpit features is voice activation of certain aircraft functions. “In the movie Firefox, thought or voice control is used to command weapons,” Beesley says. “Finger activation, however, is much quicker than voice activation. Consequently, we do not use voice activation for tasks that demand split-second decisions. We use voice commands to take care of duties that normally require numerous inputs on a keypad, such as punching in navigation coordinates and changing radio frequencies and bingo fuel amounts. Voice is very effective for housekeeping chores.”
The F-35 cockpit also includes a simplified control system for the short takeoff/vertical landing variant and the ability to accommodate a spectrum of pilot physiques ranging from the light and short (about 100 pounds and four feet eleven inches tall) to heavy and tall (about 250 pounds and six feet five inches tall).
The F-35 cockpit is also the first in a production fighter to use a virtual head-up display that projects information onto the pilot’s helmet visor. The new system, called a helmet-mounted display, or HMD, was switched on in March for the first time in F-35 laboratories where it projected symbology onto the visor by way of the actual F-35 vehicle-management and display-management computers. The HMD provides HUD information as though pilots are looking through an actual HUD no matter in what direction they turn their heads.
“We have flown in the past with helmet-mounted sights, such as Joint Helmet-Mounted Cueing System, or JHMCS,” explains Beesley. “This system is used for off-axis symbology for tactical maneuvering. But because of higher latency, or lag times, these systems cannot be used to fly the airplane. This latency issue has been solved thanks to improvements in computer technology that allow very quick update rates needed for information associated with flying the airplane.”
With the virtual HUD, pilots can look in different directions to find key tactical and flight information in their line of sight. This off-axis capability, as it is called, increases lethality and survivability by allowing the pilot to target threats with head instead of aircraft motions. The HMD eliminates the cost and weight associated with traditional head-up displays and simplifies cockpit design.
“HMD advancements will improve both weapons’ aiming and target information that flows to the pilot,” Beesley says. “In the past, forward-looking infrared, or FLIR, imagery used for targeting was restricted to the narrow field of view of the head-up display or to the restrictions of a head-down display. With HMD, pilots can view the FLIR imagery in its true location, thereby greatly enhancing their awareness of the immediate environment.”
In addition to these advancements, the HMD allows night vision display capability both on-axis and off-axis using the F-35’s 360-degree array of infrared sensors, which is called a distributed aperture system. The sensors work in combination with night-camera technology.
While the F-35 cockpit has undergone evolution and iterative change during its development — including a switch from digital light projection technology to advanced liquid crystal displays — the baseline design is now essentially fixed. It is unlikely to undergo any further significant modifications. “The design will continue to be refined throughout the life of the F-35,” Skaff says, “but the actual layout and hardware will probably not change appreciably.”
“Any changes will lie primarily in pilot-vehicle interface improvements and in additional aircraft capabilities,” Beesley says. “One of the great areas for development is the use and operation of the HMD, because we are doing things with the helmet that have never been done before.”
Overall, the F-35 cockpit environment is a generation beyond those aircraft preceding it, with changes made not for technology’s sake but purely for the sake of mission success. “The significant difference is the F-35 cockpit’s flexibility,” says Beesley. “Complexity of missions, sensors used, weapons employed, and technology available have made this cockpit both necessary and possible.”