The evidence lies within Air Force Systems Command’s Aeronautical Systems Division (ASD) at Wright-Patterson AFB, Ohio. There, the Air Force Wright Aeronautical Laboratories (AFWAL) are marshaling a mind-bending array of newly mature or fast-ripening technologies for convergence in future high-performance aircraft. And the spotlight is on USAF’s Advanced Tactical Fighter program, which is now, finally, a going concern.
As presently conceived, the ATF will be far more capable than any fighter yet built. But it will not overtax its pilot. On the contrary, its technologies will mesh to make the pilot’s many tasks more manageable, his cockpit less cluttered and disconcerting, his presence more meaningful. The ATF will be a highly automated airplane, but its pilot will be anything but an automation.
The promise of unprecedented compatibility between the ATF and its pilot springs partly from developments in the Advanced Fighter Technology Integration (AFTI) program, being managed by ASD for USAF, NASA, and the Navy, Capitalizing on rapid advances in avionics, propulsion, aerodynamics, computational capability, materials, and other high technologies, AFTI and an assortment of related programs are giving new meaning to the term “weapon system.”
In short, the programs are showing that men, missiles, and flying machines will make an ever-better team, and that their future roles in air warfare should be examined in orchestration with – not in isolation from – one another.
Over the past several years, the US defense establishment’s most fervent adherents of autonomous missiles have predicted that such weapons will render air-superiority aircraft and fighter pilots passé. They claim that, in air warfare of the future, aircraft will be employed merely as trucks to take the omniscient missiles aloft and cut them loose from afar. Moreover, the missile buffs argue that high-performance fighters already strain their pilots’ physiologies and powers of concentration, and thus have reached their limit of utility.
This problem was addressed in a 1982 report for AFSC by the Air Force Studies Board of the National Research Council. Called “Automation in Combat Aircraft,” it said that “the intelligent allocation of tasks between pilots and automated systems has long-been recognized as a key problem in the development of aerospace technology.” That problem must be overcome, said the report, because “the human operator is a crucial component of the combat aircraft system.” Moreover: “Any attempt to automate combat aircraft …must be done in the context of human capabilities and limitations.”
Integrating Man and Machine
This is exactly what is happening at ASD. “What we’re aiming for in the Advanced Tactical Fighter,” explains Col. Albert C. Piccirillo, ATF Program Manager in the office of ASD’s Deputy for Development Planning, “is to integrate the man and the machine to an unprecedented extent, to where everything – pilot, airframe, engines, weapons, fire control, flight controls, and sensors – is interfaced and working as total system.”
The cockpit is the cynosure. “Cockpit integration and simplification are what we need,” declares Brig. Gen. Ronald W. Yates, ASD’s F-16 Program Manager. “We have got to the point where we provide the pilot with tremendous amounts of information, highly compressed, from many sources, all in real time. Often, he doesn’t know what to do first. He doesn’t need any more sensors or switches. He needs something to tell him, ‘Here are your targets and your threats, and this guy is going to kill you unless you deal with him now.’ “
This is being done. In the name of cockpit automation technology, ASD’s laboratories and other USAF experts are studying the configuration and content of fighter cockpits. With an eye to the future, they are exploring such questions as how much should be done automatically vs. intervention by the pilot, how best to cohere and convey information on his panels, and what his optimum seat angles should be for certain tasks under certain conditions. Such research is relying heavily on simulators, an expanding arena at ASD.
Making the pilot a better manager of his work load will avail him nothing, however, if his fighter is too hot to handle, too easy to detect, lacking in combat radius for all its speed, or precluded from using airstrips torn up by enemy bombs.
This is why ASD is also concentrating on developing engine, airframe, and flight-control technologies that will restrain G loadings, provide short-takeoff-and-landing (STOL) capability while upgrading performance, and permit sustained supersonic speeds with out using fuel-gobbling afterburners.
The many disparate technologies for accomplishing all this – at system, subsystem, and component levels – should be at hand by the time the ATF goes into full-scale development. But the tough part will lie in sorting out the technologies, and in forming the right combination at the right time for incorporation in the ATF. This, says Lt. Gen. Robert D. Russ, USAF’s Deputy Chief of Staff for Research and Development, will entail “a fantastic effort – but it’s doable.”
Lt. Gen. Thomas H. McMullen, Commander of ASD, agrees on both counts. General McMullen makes the additional point, a salient one, that “the integration of technologies has become a technology of its own.” (See also p. 42.)
This is nowhere truer than in the ATF program, which Colonel Piccirillo confidently predicts will produce “the most integrated weapon system ever built.” Such a prospect suggests a need for exquisite coordination among the already tightly knit AFWAL laboratories and ATF-related program offices. Thus, the sense of teamwork at Wright-Patterson is especially palpable now that the ATF is on its way.
After several years of discussions about the need for and timing of the ATF program, it came alive only last September. USAF awarded contracts to seven aerospace companies – Boeing, General Dynamics, Grumman, Lockheed, McDonnell Douglas, Northrop, and Rockwell International – for conceptual designs to be delivered next spring.
“The concept definition phase will do a great deal to converge our ATF technology options,” explain Dr. Keith Richey, Chief Scientist at ASD’s Flight Dynamics Laboratory. “We probably have five to six years to bring the technologies to the point of readiness. That’s adequate time to do some technology demonstrations that need to be done, assuming the funding holds up.”
The companies involved in the ATF program are guarding their design concepts closely. For one thing, explains a high-ranking industry official, “eighty-five percent of what each of us [the companies] is doing is pretty well known to all the others. But the other fifteen percent is highly proprietary, and a lot of it has to do with how we plan to put all the technologies together.”
Eluding Enemy Detection
There is another reason for silence. The fighter will be designed to embody a variety of advanced low-observables technologies. The threat makes this imperative.
As a result, ASD and its design contractors are up against the problem of keeping the ATF’s radar, infrared, and optical signatures at very low levels, while retaining the classic capabilities of a fighter. Among other things, this means attaining transonic and supersonic speeds with minimum use of heat-spewing afterburners, a capability that is coveted for its fuel efficiency and fighting range as well.
It also means engine-inlet designs – a la the B-1B bomber and presumably the Advanced Technology Bomber (ATB) – that prevent enemy radar signals from echoing off of engine fan blades, and nozzle innovations, such as the “Venetian blind effect.” For veiling exhaust emissions and thwarting IR seekers.
Eluding enemy detection will become exponentially more difficult for US aircraft in the years ahead. The Soviets continue to develop new generations of fighters and interceptors now rivaling, in their target-acquisition and fire-control capabilities, top-line US fighters and attack aircraft. Soviet radars operating with SAM batteries are also demonstrably more formidable. All such systems strongly suggest an increasing Soviet mastery of digital electronics, a technology in which the US has begun to lose its longtime lead.
The urgent need to outdistance the Soviets once again in microelectronics is the raison d’être of the Pentagon’s high-priority, tri-service Very-High-Speed Integrate Circuits (VHSIC) program. A resounding success so far in development, the program is beginning to turn out semiconductor chips for military computers that should make them capable of processing signals and data at least a hundred times faster than is presently possible.
USAF can hardly wait for the VHSIC microprocessors. “The total integration of the avionics systems on each of our airplanes is number one among all our VHSIC program priorities.” Asserts one USAF official. And the ATF will be designed for VHSIC data and signal processing right from the start.
Given the Soviet threat, there is no longer much doubt among US defense policymakers – as once there was – of the need for the ATF. “Do we need it? We sure do,” declares Deputy Defense Secretary Paul Thayer, a onetime fighter pilot. “I doubt that the Russians will come up with anything equal or superior to the ATF between now and sometime in the 1990s,” Thayer adds, “but they’ll certainly forge ahead in new fighters.”
Even at that, such timing would make for a very close call. The ATF’s first flight is not scheduled until 1991, which suggests operational status approaching the mid-1990s.
Cautioning against slippage in that schedule, General McMullen makes the point that “the ATF is already farther behind the F-15 than the F-15 was behind the F-4.” Moreover, USAF officials claim that in the context of fighter technology advancement, the leap from the F-4 to the F-15 – even though both are jets – was longer than the one from the propeller-driven P-15 to the F-86 Sabre.
There is however, a plus side to the ATF program pacing. In its current programs for upgrading or variegating the capabilities of its F-15s and F-16s, ASD is getting a more certain feel for technologies – and their integration – that are apropos of the ATF. Among them are improved radars, cockpit displays, flight controls, engines, and aerodynamic shapes, such as the cranked-arrow wing and the tangential weapons carriage features of the F-16 and F-15 Dual Role Fighter (DRF) candidates respectively.
ASD’s F-16C and D development program provides insight into the problems of upgrading fighter technologies and integrating them as they go. The new F-16s are being readied to accommodate, at various stages, the Advanced Medium-Range Air-to-Air Missile (AMRAAM), the Advanced Self-Protection Jammer (ASPJ), the Low-Altitude Navigation and Targeting Infrared for Night (LANTRIRN) pods, and receivers and data links for the Navstar Global Positioning System (GPS) navigation satellites.
In addition, the F-16C and D variants will also contain new-generation radar altimeters, radar warning receivers, and perhaps – later on – navigation systems employing ring laser gyroscopes.
All of the above, says General Yates, the program manager, “are fantastic challenges in advanced technologies in and of themselves. And they are all interactive. They have to play together as an integrated weapon. That’s the biggest challenge of all.
A Dual Role ATF?
Facing up to that challenge from the outset of the design process is what the ATF program is all about. The challenge will become more and more complicated as ASD and its ATF contractors continue to cope with the very big question of how much air-to-surface capability the fighter should ultimately have.
The ATF will be designed, first and foremost, as an air-superiority aircraft. But, secondarily, it will also have to have air-to-surface capability.
At the moment, USAF is planning on a fleet of ATFs that could be at least as large in numbers as the planned fleet of F-15s. Justifying such numbers may be difficult in light of defense-budget stringencies and operational goals unless USAF promotes the ATF to the Defense Department and Congress as a highly flexible combat aircraft, no fudging about it.
Such duplication of missions in one aircraft may be possible with the ATF as never before. Given the swift pace at which aeronautics technologies are progressing and are being integrated, the best air-to-air and air-to-ground capabilities may indeed be attainable in the ATF. The reason: Historical tradeoffs between those capabilities are no longer so severe as in the past, and may indeed be disappearing. This is being demonstrated by ASD’s work on the Dual Role Fighter (DRF) program, and in its farther-out programs as well.
The ATF’s potential for air-to-surface capability as a fully integrated weapon system is showing through in the ASD Avionics Laboratory’s “night-in-weather-attack” program. That program is exploring new technologies to enable attack aircraft to fly and strike targets around the clock and in the nastiest weather imaginable.
A major program goal is to develop microelectronic target-acquisition and navigation systems that are not only move effective and reliable but also so small and compact that they will not encumber the aircraft in its air-superiority mode.
USAF has long believed that radars – of the synthetic-aperture or millimeter-wave variety – may be the key to this. But synthetic aperture radar is apparently farther away from application than its adherents had hoped. And millimeter-wave radar turns out to have a lot of problems with raindrops and other forms of precipitation.
As a result, ASD’s Advanced Target Acquisition Sensor (ATAS) experimentation takes on special significance. Looking beyond the LANTIRN system now in development, with its two outboard pods for navigation and targeting, ATAS – employing highly advanced Forward-Looking Infrared (FLIR) technology – shows great promise.
ATAS technology is expected to double the range of existing FLIR systems and to be much more difficult to spoof with countermeasures, such as flares. Moreover, ATAS will be sufficiently sharp-eyed, officials claim, to tell the difference between, say, a tank and a tank-mockup decoy.
ASD is also developing ultra-sophisticated software for fire-control avionics in strike aircraft. This comes under the MULTACK, for Multiple Target Attack, program. Its essence is software, and its goal is this:
When fire-control processors received data from aircraft sensors showing multiple targets, the micro-processors themselves will work out the complex algorithms needed to deliver the aircraft’s weapons onto those targets, in a discriminating manner, in just one pass.
ASK is also nurturing terrain-avoidance (as distinguished from terrain-following) technologies that will enable attack aircraft to approach densely defended ground targets on preprogrammed paths that approximate broken-field running in order to elude ground fire, and at altitudes as low as 100 feet. To this end, ASK is developing a carbon-dioxide laser detection system for the strike aircraft that should be capable of discerning attack-approach impediments as tiny as wires strung across canyons or gorges.
New Ways to Fly
While current fighter-enhancement programs teach ASD how to cope with technology insertion on the run, they are probably transcended – in their technological significance for the ATF and for other future aircraft – by the AFTI effort. Accurately billed as a demonstration of “new ways to fly.” AFTI is managed by ASD’s Flight Dynamics Laboratory for USAF, NASA, and the Navy. One of ATF’s main test-bed aircraft, operating out of Edwards AFB, Calif., is an F-16 featuring a Digital Flight Control System (DFCS).
At the core of that system are three digital computers (naturals for future VHSIC implantation) and copious multiplex data transmission buses that add startling dimension to the Fly-by-Wire (FBW) technology pioneered by FDL two decades ago. Now AFWAL is edging even farther out in such technology. It is testing “fly-by-light” controls in which a fiber-optic cable supplants electrical circuitry as the data link between computers and flight controls. Such links are lighter, faster (they can transmit more data, more swiftly, through smaller connections), and – very importantly – may be virtually impervious to electromagnetic interference.
If mature when needed, fiber optics technology could well find a home in the ATF. For now, however, FBW technology at the DFCS state of the art does quite nicely. DFCS’s ultra-fine-tuning of control surface innovations such as the AFTI/F-16’s twin vertical canards makes it possible for the pilot to fly the aircraft in several bizarre modes. Among these are sideways without banking and up and down with the aircraft at the horizontal – all the time with weapons firmly on target or firing.
The weapons connection is a key one. It signifies one of the highest-priority goals of all future aircraft technology integration: the blending of fire and flight controls.
Now, ASD is moving to factor STOL nozzle technology into the high-maneuverability equation. Late last September, it issued an industry Request for Proposal (RFP) for a “STOL and Maneuver Technology Demonstrator” aircraft. The aim is to fly, by 1987, a test-bed aircraft with a two-dimensional exhaust nozzle for thrust vectoring and thrust reversing, all integrated by means of digital flight controls.
This program also comes under the heading of “sortie generation,” one of AFWAL’s four “major thrusts” – along with night-in-weather attack, supersonic persistence, and space applications. The sortie-generation endeavor is oriented to making future fighter and attack aircraft capable of taking off from and landing on damaged runways within 1,500 feet, maybe even slantwise, to avoid bomb craters.
Given the proliferation of Soviet long-range missiles and forward-based attack aircraft, this is an urgent matter. But the STOL program’s payoff for in-flight fighter maneuverability, too, could be very big. Vectored-thrust nozzles, perhaps even blowing against the aircraft’s surface, hold promise for some pretty fancy flying.
General Russ describes it: “With the flight controls being demonstrated in AFTI, and with vectored and reverse thrust, we’ll be approaching the maneuverability of helicopters in high-performance fighters.” For example, says the General, pilots will be able to “skid” their aircraft into turns – combining lateral movement and acceleration at high thrust – without inducing overpowering G loadings. Such a prospect, he declares, is “very exciting.”
The Wings of Tomorrow
Wing technologies now bearing fruit also bode well for aircraft maneuverability. Over the years, wing designers have come up with an assortment of wings oddly shaped or meant to move in flight. Many have been wildly impractical. Some of the promising ones were far in advance of structures and controls technologies needed to make them worthy of application. Now such technologies have caught up, and new wing concepts are attracting greater attention.
One such concept is the forward-sweptwing that the Defense Advanced Research Projects Agency plans to test on Grumman’s X-29 Advanced Technology Demonstrator aircraft. The wing skin is built of epoxy composites reinforced with boron and graphite fibers. This gives it stiffness to resist bending and torsion. Its champions are confident that the forward-sweptwing, working in conjunction with automated canards, will demonstrate eye-catching maneuverability.
Some high-ranking USAF officials appear to be interested in the DARPA program more for what it may tell them about canards, automation of controls, and the advantages and disadvantages of flying an intrinsically very unstable aircraft. But they are perking up to the potential of another design – the mission-adaptive wing.
Late next summer, the AFTI/F-111 aircraft is scheduled for first flight with a mission-adaptive wing. Now being attached to the F-111 by Boeing, its builder, and NASA, the wing has no conventional flaps, slats, ailerons, or spoilers. It changes camber (shape) in flight. Controlled by a digital FBW system, its advanced-composite leading and trailing edges flex continually In accordance with varying flight conditions. Thus, the completely smooth wing is always at its optimum shape for cruise or climb, in clear air or turbulence – you name it.
For the combat pilot, says Ronald W. DeCamp, ASD’s manager of the mission-adaptive wing program, this means, “tighter maneuver radius for evasive action and survivability, a more stable aircraft to weapons delivery, increased confidence, and a more comfortable ride.”
Indeed, a great many of today’s developments or new applications of aerodynamics, engines, and avionics, singly or in integration, are creating a more orderly and comprehensible environment for the pilot. Prominent among them is the integration of avionics, centered in the Advanced Systems Integration Demonstrations (Pave Pillar) program under the direction of ASD’s Avionics Laboratory.
Beckoning to VHSIC technology, Pave Pillar contractors aspire to nothing less than consummate interaction – amid an avionics architecture featuring high-speed multiplex data – of the aircraft function functions of navigation, guidance, target acquisition and tracking, weapons management and delivery, terrain following and avoidance, and electronic countermeasures.
The implications of this for the pilot are enormous. It means that instead of data from such subsystems showing up willy-nilly on cockpit-crammed individual displays and dials, the data will be collated by information-integrating microprocessors and then fed to a relatively few head-up or cathoderay tube (CRT) displays.
In coming years, CRTs will almost certainly be replaced by Light-Emitting Diode (SEL) displays in showing the pilots cartoon-like pictures or maps of what needs to be done. Now being developed by FDL, the LED displays are smaller and more reliable than CRTs. CRTs tend to go blank all at once upon malfunctioning. In contrast, LED displays fade out gradually, giving ample warning of their need for repair or replacement.
Sensors and Computers
When the fully integrated sensors and computers show the pilot that he had better concentrate for the moment on dodging a hill, or on turning away from outrunning an oncoming missile, other micro-electronic devices will automatically find to weapon-system duties less demanding of his attention, such as fuel management. Moreover, the pilot may well be able to command the aircraft to take action, in attack, avoidance, or whatever, simply by telling the computers what he wants done.
The ability of computers to respond to voice commands, or indeed to issue them, is nothing all that new. Some automobiles have computers that speak. An F-15 computer emits an “Over-G, Over G” warning, in female tones, when the pilot is overextending his fighter. F-16 computers sounds off amid a score of emergency situations with the words “Caution” and Warning.” But all this is trifling technology as compared to the intricacies of a computer that will be able to handle an extensive vocabulary and to recognize and react to the pilot’s voice as it varies in timbre and pitch under combat stress.
Such computers require a relatively high level of artificial intelligence programming, or complex algorithms (mathematical expressions), in their software. This, again, is why very-high-speed integrated circuits and very-large-scale integrated circuits will be in heavy demand once they emerge from development and testing. As microprocessors, their commodious, quicksilver-fast circuitry will be highly conducive to artificial intelligence programming.
Even without such circuits, however, USAF’s current voice-reactive computers are doing fine. The AFTI/F-16 now embodies some voice-recognition functions and shows “great promise,” says one ASK official. For example, the system has demonstrated that it can set up weapons-delivery modes in the fighter’s fire-control system with, he says, “a pretty reasonable degree of reliability.”
The problem is that, in combat, such a system would have to be downright foolproof. Pilots do not want their weapons going off at the wrong time because the computer thought it heard something it hadn’t. Moreover, many pilots, despite their wish to be free of “switchology” – and to spend less time looking down into their cockpits – may feel strange talking instead of touching, as they have always been trained to do.
Consequently, USAF voice-command researchers believe that a happy medium may be in the offing. Pilots may still rely on switches, although far fewer of them, for such lethal functions as releasing bombs or launching missiles.
Simplifying the pilot’s workload and freeing his hands for flying is also the aim of the helmet-mounted sight, which will be used in the AFTI/F-16. This system permits the pilot (the aircraft weapon system’s optical supercomputer) to lock on the target just by looking at it.
As of now, in single-seat fighter, pilots locate and track a target by turning their radar. On the new helmet-mount sight, across hairs are on the helmet visor. All the pilot has to do in order to lock on a target – once it is within visual range – is keep his eye on it. His line-of-sight angle to the target is translated into digital data by an electromagnetic receiver on his helmet visor and is passed on to the aircraft’s fire-control system via a transmitter on the canopy behind his head.
Harking to the worsening threat of chemical warfare, ASD is developing a pair of potential lifesaving cockpit systems. Called the On-Board Oxygen-Generation System (OBOGS) and the On-Board Inert Gas-Generation System (OBIGGS), they are systems that generate air suitable for respiration. The air enters the system from the engine, where it has been purified by hear, is cooked for breathing, and then passed back. USAF plans to install such systems on some developmental aircraft in the near future.
Electronics Is the Key
Interdependence of pilot and aircraft is strikingly evident, too, with regard to engines. And once more electronics is the key.
In ASD’s current fighter engine programs, for example, Pratt & Whitney and General Electric have already introduced Engine Electronic control (EEC) systems. Those systems do not actually run the engines: rather, they act, in effect, as supervisors – and optimizers – of the conventional hydro-mechanical controls. The EEC system is based on analog computation. Now, however, ASK and its engine contractors are advancing to Digital Engine Electronic Control (DEEC) systems.
These DEECs will literally operate the engines, fine-tuning the various stages at all times in keeping with what the pilot – through his throttle settings – tells them what he needs them to do. And during hands-off, steady-state fight operations, the DEECs can be totally in charge, prescribing optimum engine adjustments for most efficient “surge” operations.
“Digital electronics will give us tremendous improvements,” declares Col. James Nelson, ASD’s Deputy for Propulsion. “Analog control is good. But it’s relatively fixed in what it can do for you. Digital control is much more flexible. It opens up that whole new arena of programming, just as it does for radar, electronic countermeasures, sensors, or whatever.”
The engine companies are making the transition to DEECs in their improvements of existing engines for current fighters and bombers. What they are learning will be applied and refined in developing engines for the Advanced Tactical Fighter.
P&W and GE are assimilating technologies for ATF engines (the fighter is expected to have two powerplants) in the 9:1 or 10:1 thrust-to-weight ratio class. In comparison, P&W’s F100 engine is 8:1 thrust to weight; GE’s F110, in the 7.5:1 class.
The ATF demonstrator engines being designed by both companies are not expected to exceed, by much, the absolute thrust of the F100 or the F110. But they will be much lighter than either, thus allowing for much greater relative thrust. They will also be capable of running hotter and a great deal more reliably. The companies will bring off this seeming anomaly. USAF officials predict, by means of their extensive incorporation of heat-resistant alloys and, even more importantly, of sophisticated cooling techniques.
Engines: The Pacing Item
As in all aircraft development programs, the engine development will determine the pace of the ATF development program. Long engine-hardware lead times make it imperative that the ATF engines get an early start. But from the word go. ASD is paying special attention to keeping ATF’s airframe, avionics, and engine designs and developments on closely spaced parallel tracks, ready for smooth confluence at the proper milestones.
A major goal of such monitoring is to ensure that the ATF engine inlet design will be synergistic with the airframe design. This may be a tricky proposition, given all possible airframe configurations and the need, for instance, to design the inlets with signature reduction high in mind.
Once ASD narrows down its field of ATF airframe designers, the engine developers will undertake computer-model testing of inlet designs appropriate to the designs of the two or three airframe finalists. This approach is a far cry from that of the old days (pre-F-15), when engine and airframe designs all too often proceeded in isolation, and were found to be workable or unworkable only when flown.
Stunning advances in computational capability now make It possible to presage optimal inlet-air-frame matchups before hardware is ever cut, or to determine, for example, the heat-resisting and other durability properties of a structure such as a turbine disc. As part and parcel of the computer-aided design (CAD) process that is becoming pervasive in the aeronautical world, computerized analytical models derived from mathematical expressions can tell as much about the behavior of a system or a structure as can, for example, a wind tunnel.
Such computational wizardry is not an end-all, however. As one USAF official puts it: “We’ll always have it sit in airplanes and feel them out in flight before we’re totally confident of what they’ll do.” And that means pilots.
Over the years, as automation-cum-artificial intelligence proceeds apace, it is more than likely that unmanned aircraft will play a larger role in such missions as reconnaissance, targeting, and ground attack. The Boeing Pave Tiger Remotely Piloted Vehicle (RPV), being developed for USAF, is a promising example. But when it comes to air superiority, says Stan Tremaine, ASD’s Deputy for Development Planning: “That’s where you have the need for split-second decisions best made by humans.
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