PILOT-VEHICLE INTERFACE is a dry, but accurate, description of the centrepiece of the F-22's array of technologies. The F-22 cockpit is seen as a showcase of the team's achievement in integrating human potential into the aircraft.
It is here, under the single-piece canopy, strapped into the modified ACES II ejection seat, wearing the purpose-designed pilot's ensemble, hands on throttle and sidestick, facing an array of flat-panel displays, that the F-22's operational concept comes together - the concept of the pilot as mission manager, not sensor operator.
The F-22's integrated avionics operate the sensors, within limits set by the pilot, explains Ken Thomas, cockpit team manager. "The pilot commands information, and the system picks the sensors to answer the pilot's questions," he says. The pilot does not turn a sensor on, but instead sets the emission-control level, from passive through low-probability-of-intercept to fully active, within which the avionics must operate.
"The concept is based on a decision-making globe. The pilot needs information to make a decision, and the avionics need to provide it," Thomas explains. The time available to make a decision determines the quality of information required. "It's based on timeline, on whether the threat is a slow or fast mover," he says. "The outside ring is bearing-only, but the pilot can slew the cursor and the avionics will go get more information, and create a range/bearing track. If the pilot designates a target, the avionics will go get a weapon-quality track," Thomas says.
NEED TO KNOW
The pilot's need for information in time to make decisions determines zones of operational interest around the aircraft, based on the relative capabilities of the F-22 and the threat, such as signatures and sensor and weapon ranges. These zones determine the data the avionics must collect, fuse and present to the pilot.
In the outermost zone, only situational awareness is required, in the form of tracks provided by passive sensors. As targets move closer, they are prioritised by identity and/or threat potential. Based on target priority, the sensors are tasked to collect the additional information required to enable the pilot to decide whether to engage or avoid. At any time, the pilot can slew the sensors' area of interest, but the system will maintain situational awareness, to detect threats that pop up.
The highest-priority targets are placed in the shoot list; the pilot can accept or change the priority and the system will provide attack steering cues to launch AMRAAMs beyond visual range.
Information is presented to the pilot on three tactical displays, using icons which convey target identity and track quality. Thomas says that the concept was proved to be intuitive in dem/val, when Air Force pilots with little combat experience emerged from full-mission simulations with some of the highest rankings. F-22 chief test pilot Paul Metz agrees: "An incredible assimilation of information appears in front of you very intuitively. The use of colour, shape and size passes information in a unique way."
Symbology is being tested which indicates target classification. Five different aircraft-shaped icons will identify the threat as a high-technology fighter, low-technology fighter, bomber, helicopter or transport. Previously the pilot had to hook an icon to display target type.
Threat classification fuses seven different types of data, "-six of which we can't talk about", says Gherry Bender, tactical subsystem manager at Boeing, which is responsible for the tactical displays. Target identity can come from the EW system detecting emissions, from the radar counting engine blades or from the CNI system.
According to Bender, the challenge of deciding what data are important and what are not has required considerable pilot input. In evolving the displays, "-the biggest effort has been to make it useable to the pilot and not overwhelm him. We want the pilot to be a tactician, and not a sensor manager," says Stan Kasprzyk, pilot-vehicle interface team leader.
To help the pilot concentrate on the mission, housekeeping has been eliminated by automating subsystem control. Programme general-manager Tom Burbage says that start-up has been reduced to four steps: "Data-transfer cartridge in, battery on, APU [auxiliary power-unit] switch on, throttles to idle, close the canopy - okay, five steps," he jokes. Avionics are brought on line and tested automatically.
In the air, response to system failures has been automated. "It's the pilot's job to go out there and fight, not be an engineer," says Metz. "If an engine stalls and flames out, it will restart itself. If it won't start, the pilot will be asked to descend so the aircraft can start the APU and use it to try to restart the engine. The pilot has to tell the engine to quit trying, by pulling the throttle to off."
The integrated caution/advisory/warning system is being designed to provide the pilot with information on how failures affect the mission. Clicking on an warning message on the upfront display will bring up an electronic checklist on the multi-function display below. The checklist will tell the pilot how to handle the emergency - ultimately the pilot will press 'execute' and the system will handle everything, says Thomas. The system is being designed to screen out the secondary effects of individual failures, so that one warning message requires one action.
CAREFREE ABANDON
The F-22 will be easy to fly, says Metz. "We've worked hard to achieve user-friendliness in the handling qualities of the aircraft," he says. The flight-control concept of 'carefree abandon' means that the pilot "-will never have to worry about losing control, overstressing the aircraft, or getting anything but power," he says. There are 20 controls with 63 functions on throttles and sidestick, which enable the pilot "-to do everything hands on", says Burbage.
Unusually, canopy design was part of the cockpit team's task, says Thomas. There is no canopy bow, because of low-observability and pilot-vision requirements, and the transparency is a single piece of monolithic polycarbonate, with no complex curves. Birdstrike testing revealed a problem when the canopy deflected and shattered the head-up display, he admits, and display supplier GEC-Marconi Avionics is developing a collapsible combiner which will "-still work as a 600kt [1,100km/h] blast shield," he says.
The canopy rotates down and translates forward to lock. To jettison, the canopy is pushed back and lifted off by a rocket thruster at its forward edge. Thomas says that the canopy does not fall, but becomes a flying object, and is weighted asymmetrically to ensure that it diverges from the ejecting pilot's flightpath.
Modifications to the Air Force's McDonnell Douglas ACES II zero-zero ejection seat for operation at speeds up to 1,100km/h in the F-22 include arm restraints and a fast-acting drogue. As the seat moves up the rails, restraint nets encapsulate the pilot and the drogue is fired to deploy immediately the seat leaves the rails and before it can yaw. This prevents injuries which can occur if the seat is off axis when the drogue deploys, Thomas says. The seat is "electrified", he says, with an electronic sequencing system which can be tested on the ground.
The F-22 is the first programme to include development of the man-mounted life-support system. "We wanted to be able to spend lots of time at high altitude and high g without wearing the pilot out," says Michael Wright, senior specialist engineer at Boeing. "The problem was that, to protect the pilot from chemical/biological [CB] threats, we had him wrapped in plastic. So we had to give him thermal protection. In addition, he needed more thermal protection in case he ditched in the water. If you put CB gear, a cold-weather suit, g-suit and thermal protection on him, you'd be lucky to get him into the aircraft, let alone enable him to fly or fight, so we needed something different."
The resulting F-22 life-support system is divided into aircraft- and man-mounted pieces. An onboard oxygen-generating source has been developed by Normalair Garrett to "-fit into a small space with a peculiar shape". The UK manufacturer also developed a single breathing regulator/ anti-g valve, to provide positive-pressure breathing at high altitude and high g.
Man-mounted pieces include an air-cooling garment, produced by ILC of Dover, Delaware. A dedicated line feeds conditioned air to the pilot, providing a temperature range of 13-32 degrees C. Over this goes the flight suit, designed by Boeing and British Columbia-based META Research. Doubling as an immersion suit, as well as providing protection against flames and a CB environment, the integrated suit will meet with much higher pilot acceptance, Boeing says.
Over the suit goes an upper pressure garment, also CB-hardened, which provides counter pressure to assist breathing and counteract g. The lower g garment incorporates a one-piece bladder for the legs and lower torso. "It is still mobile enough so the pilots can fight, otherwise it would have had to be like a full pressure-suit like those used on the SR-71," says Wright.
A lightweight, low-lift helmet for successful ejection at speeds up to 600kt and high altitudes has been developed by UK-based Helmet Systems. The helmet has provision for anti-noise reduction to counter the cockpit roar of the supercruising fighter, and incorporates a suspension system to prevent high-g turns affecting helmet-mounted display optics.
"From a pilot's perspective, the integrated suit is better because you get used to wearing the same thing. It's already a stressful time if you have to go into combat, and it helps if the suit, mask and helmet are already familiar and you don't need to add extra things for overwater flights and CB," says Boeing chief test pilot Chuck Killberg. The Air Force has yet to buy the ensemble for production F-22s.
Source: Flight International
