The air strike against Balakot by the Indian Air Force (IAF) and the air combat that followed in response to the Pakistan Air Force (PAF) riposte on February 27, 2019, rekindled interest in fighter aircraft technologies and air combat capabilities. Combat aviation has not only become the most preferred means of prosecution of war, but has also seen the fastest growth of technology. Fighter aircraft are designed for aerial combat and to bomb or attack surface targets. World War II featured fighter combat on a larger scale than any other conflict till date. During the invasion of Poland and France, the Luftwaffe’s air superiority played a major role in victory for the Germans.
In Battle of Britain, the use of radars resulted in advantage RAF. In WW II, strategic bombing was the main attack mission. Thus evolved the concept of aerial fighter escorts to bomber/strike missions. Light fighters proved very successful in WW II. Their special features were agility (speed, manoeuverability), accurate weapon delivery, all-weather and night operations capability and be secure from enemy air and surface threat. As technology grew, the pilot was not just flying the aircraft accurately and safely, but was also a weapon systems manager and operator. With aircraft and systems performance increasing, technology enabled the pilot to reduce workload and take on more tasks.
After the advent of the Jet Age, the aviation community started classifying jet fighters by ‘generations’. There are no official definitions, and they just represent stages in the development of fighter design, performance capabilities and technological evolution. Most air forces currently operate fourth-generation aircraft. There are a few fifth-generation aircraft flying and the sixth-generation aircraft are on the drawing board even as technologies are evolving.
Initial Fighter Aircraft Generations
The first-generation of jet fighters comprised the initial, subsonic jet fighter designs introduced late in World War II. Many had un-swept wings and only guns as the principal armament. The American F-86 Sabre and Soviet MiG-15s were first with swept wings and near transonic performance. Grumman’s F9F Panther was the first aircraft with an afterburner engine. Early versions of Infra-red (IR) Air-to-Air Missiles (AAM) and radar guided missiles came up in the 1950s. The second-generation fighters evolved by mid-1950s and had better aerodynamic design (Swept and Delta wings), propulsion systems (afterburner) and used aluminum alloys and were able to break the sound barrier.
Radars were miniaturised for carriage aboard smaller aircraft and greatly aided the pilot in target acquisition and weapon aiming. IR missiles became common place. Radar-guided missiles were introduced with the ability of Beyond-Visual-Range (BVR) combat. BVR allowed building the concept of the interceptor. However, based on experience in Korea and Vietnam, the third-generation aircraft that came around mid-1960s believed that combat would still devolve around dogfights using IR missiles. Analogue avionics began replacing the older cockpit instrumentation and started taking over part of the pilot functions. Flight Control surfaces like canards, slats and blown flaps greatly improved turning performance.
Thrust vectoring evolved for Harrier vertical and short take-off and landing. Medium-range AAMs gave greater ‘stand-off’ ranges. New techniques for Electronic Counter Measures (ECM) were introduced. The US Navy established its famous TOPGUN fighter weapons school. Advanced Air Combat Maneuvering (ACM) and Dissimilar Air Combat Training (DACT) began. Terrain avoidance radar made it possible to fly very low level at night. Air-to-surface missiles and Laser Guided Bombs (LGBs) increased stand-off weapon delivery distances. Power-plant reliability increased and jet engines became ‘smokeless’ to make it harder to sight aircraft at long distances. Variable-geometry wings were introduced on aircraft like F-111 and MiG-23. Very high speeds of aircraft necessitated development of ejection seats for safe exit during emergency. Ejection seats are nowadays designed for use at zero-speed on the ground. Quick response G-suits allow sustaining higher ‘G’ forces.
Fourth-generation fighters strengthened the trend towards multi-role configurations. Concept of ‘energy-manoeuverability’ impacted aircraft designs that required performing ‘fast transients’ – quick changes in speed, altitude and direction – as opposed to relying mostly on high speed. It called for small lightweight aircraft with higher thrust-weight ratio. The F-16, MiG-29 and Mirage-2000 evolved. Fly-By-Wire (FBW) flight controls became possible due to advances in computers and systems integration. This allowed relaxed static stability flight and in turn, agility. Analogue systems began to be replaced by digital flight control systems in late 1980s. Likewise, Full Authority Digital Engine Controls (FADEC) to electronically manage power-plant performance was introduced. Both allowed carefree manoeuvering by the pilot.
Pulse-Doppler fire-control-radars added Look-down/shoot-down capability. Head-Up Displays (HUD), Hands-On-Throttle-And-Stick (HOTAS) controls, and Multi-Function Displays (MFD) allowed better situational awareness and quicker reactions. Composite materials such as bonded aluminum honeycomb structures and graphite epoxy laminate skins helped reduce aircraft weight. Improved maintenance design and procedures reduced aircraft turnaround time between missions and generated more sorties. Another novel technology was stealth, using special ‘low-observable’ materials and aircraft design techniques to reduce detect-ability by the enemy’s sensors, particularly radars.
The first real stealth designs were Lockheed F-117 Nighthawk attack aircraft in 1983, and the Northrop Grumman B-2 Spirit in 1989. Military budget cuts after Cold War and high funding requirements of the fifth-generation fighter, resulted in a term called the 4.5th generation fighters during the 1990s to 2005. This sub-generation saw advanced digital avionics, newer aerospace materials, modest signature reduction, and highly integrated systems and weapons. These fighters operated in network-centric environment. Key technologies introduced included BVR AAMs; GPS-guided weapons, solid-state phased-array radars, Helmet- Mounted Display Sights (HMDS), and improved secure, jamming-resistant data-links.
A degree of super-cruise ability (supersonic without afterburner) was introduced. Stealth characteristics focused on front-aspect Radar Cross Section (RCS) reduction through limited shaping techniques. Eurofighter Typhoon, Dassault Rafale and Saab JAS 39 Gripen were in this category. Many fourth-generation aircraft were also upgraded with new technologies. Su-30MKI and Su-35 featured thrust vectoring engine nozzles to enhance manoeuvering. Most of them are still being produced and evolving. It is quite possible that they may continue in production alongside fifth-generation fighters due to the expense of developing the advanced levels of technology. 4.5th generation fighter aircraft are now expected to have AESA radar, high capacity data-link, enhanced avionics, and ability to deploy advanced armaments.
Air Superiority as a Concept
Air superiority fighter aircraft are meant for entering and seizing control of enemy airspace as a means of establishing complete dominance/supremacy over the enemy air force. They usually operate under the control/co-ordination of Airborne Early Warning and Control (AEW&C) aircraft. Aircraft like US Navy’s F-14 and USAF’s F-15 were built to achieve air superiority from design and development stage. Both later had multi-role variants. Soviets/Russians developed MiG-29 and Su-27 around same time. Eurofighter Typhoon and Dassault though multi-role fighters, but both have air-superiority missions. F-22 Raptor, Su-30 variants, Su-35, Chinese J-11 and J-15 were also air-superiority aircraft.
The fifth-generation was ushered in by the Lockheed Martin/Boeing F-22 Raptor in late 2005. These aircraft are designed from the start to operate in a network-centric combat environment and to feature extremely low, all-aspect, multi-spectral signatures employing advanced materials and shaping techniques. They have multifunction AESA radars with high-bandwidth low-probability of intercept. IRST and other sensors are fused in for Situational Awareness and to constantly track all targets of interest around the aircraft’s 360 degree bubble. Avionics suites rely on extensive use of Very High-Speed Integrated Circuit (VHSIC) technology and high-speed data buses. Integration of all these elements is claimed to provide fifth-generation fighters with a “first-look, first-shot, first-kill capability”.
In addition to their high resistance to ECM, they can function as a “mini-AWACS”. Integrated electronic warfare system, integrated Communications, Navigation, and Identification (CNI), centralised ‘vehicle health monitoring’, fibre-optic data-transmission and stealth are important features. Manoeuver performance is enhanced by thrust-vectoring, which also helps reduce take-off and landing distances. Super-cruise is inbuilt. Layout and internal structures minimise RCS over a broad bandwidth of frequencies. To maintain low signature, primary weapons are carried in internal weapon bays.
Stealth technology has now advanced to where it can be employed without a trade-off with aerodynamics performance. Signature-reduction techniques include special shaping approaches, thermoplastic materials, extensive structural use of advanced composites, conformal sensors, heat-resistant coatings, low-observable wire meshes to cover intake and cooling vents, heat ablating tiles on the exhaust troughs and coating internal and external metal areas with radar-absorbent materials and paints. These aircraft are very expensive. F-22 costs around $150 million. Lockheed Martin’s F-35 Lightening II fighters will cost on average $85 million due to large scale production. Other fifth-generation fighter development projects include Russia’s Sukhoi PAK FA, now SU-57.
India is also developing the AMCA. China’s fifth-generation fighter Chengdu J-20 is flying since January 2011, and combat units started inducting in early 2018. The Shenyang J-31 first flew in October 2012. The programme has received government funding and is being sought after by both the PLAAF and PLANAF.
Light Vs Heavy Fighters
There is a continued decision conflict about light vs heavy fighters. Light aircraft are relatively simple with only essential features and lower cost. Light fighters generally feature a high thrust-to-weight ratio, high manoeuverability and high reliability. Intentional simplicity also allows buying larger numbers to out-number the enemy in the air under combat conditions. Modern single engine light fighters include F-16, JAS-39 Gripen and Tejas LCA, all being significantly lower in cost. Larger fighters provide the opportunity for more technology, longer range radars and heavier weapons, but are much more expensive and often unaffordable.
Unmanned Aircraft technologies are already proven and it is clearly emerging that the future is unmanned. The world is in transition. There are some who see the JSF as the last manned fighter/bomber. Solar Powered Unmanned Aerial Vehicles (UAVs) are already flying. Dual use optionally manned aircraft are under development. Unmanned aircraft are already taking-off and landing by themselves including on the moving aircraft carrier (Northrop Grumman X-47B). Autonomous mid-air refueling has been tested. Lockheed Martin’s UCLASS drone ‘Sea Ghost’ looks rather like a stealth bomber and is expected to carry 1,000-pound class weapons. The USAF has already modified F-4s and F-16s to fly them remotely. In France, Dassault leads a multi-nation delta wing UCAV ‘Neuron’ of the size of Mirage 2000. UK has a Strategic Unmanned Air Vehicle (SUAVE) programme ‘Taranis’. This will be a supersonic autonomous stealth bomber with intercontinental range. The US is also working on a Strike Bomber that is likely to be optionally manned.
Today, technologies are offering enhanced capabilities that are driving operational employment and tactics. Artificial Intelligence (AI), smart structures and hybrid systems will dictate the future. Demand for streaming high-quality data requires bandwidth, which involves innovating sensor/processing systems. Network-centric payload processing units enable onboard data fusion prior to sending to digital links. Gallium Nitride (GaN) is a semiconductor material that is more efficient, easier to cool and improves reliability for radars. Any system must be designed with the aim of maintaining a competitive advantage in an austere budget environment. The Passive Aero-elastic Tailored (PAT), a uniquely designed composite wing will be lighter, structurally more efficient and have flexibility compared to conventional wings. This wing will maximise structural efficiency, reduce weight and conserve fuel.
Hypersonic cruise, fuel cell technologies, hybrid sensors, improved human-machine interface using data analytics and bio-mimicry, combination of materials, apertures and radio frequencies that ensure survival in enemy territory are under development. Things will be built faster, better and more affordably, using 3D printing yet ensuring quality and safety standards. Additive 3D manufacture creates a world with spare parts on demand, faster maintenance and repairs, more effective electronics, and customised weapons. The development of a hypersonic aircraft would forever change the ability to respond to conflict. Nano-materials will control sizes, shapes and compositions and significantly reduce weight while creating stronger structures for air and space craft, yet drive down costs.
Future weaponry will utilise scramjets for the production of faster missiles. Despite failing its recent tests, Boeing’s X-51A Wave-rider scramjet remains under development as it hopes to reach hypersonic speeds approaching Mach 6, a speed at which a missile cannot be stopped by conventional air defence technology. Continued experiments with DEW and lasers, used for defensive as well as offensive measures, delivering effects at the speed of light, are also likely to shape precisely what sixth-generation fighters are equipped with. New aircraft will be as much about reusable weaponry (lasers) as they will be about expendable weaponry. The solid-state laser systems defensively create a sanitised sphere of safety around the aircraft, shooting down or critically damaging incoming missiles and approaching aircraft with the laser turrets. Even attacking small targets on the ground with pinpoint precision, or shooting down ballistic missiles and other traditional targets are possibilities.
The USAF is developing a new air-to-air missile, dubbed the Small Advanced Capabilities Missile (SACM) for 2030s. SACM would promise an improved solid rocket motor having synergised control enabled by combined aero, attitude control and thrust vectoring. The missile will have improved ‘high off bore sight’ for rear hemisphere kills and ‘lower cost per kill’. The missile would also incorporate energy optimising guidance, navigation and control. The Miniature Self-Defence Munitions (MSDM) will enhance future platforms self-defense capability, without impacting the primary weapon payload. A sixth-generation missile could replace AMRAAM. A survivable, long-range missile with combined air-to-air and air-to-ground capabilities is being evolved. Range would be a big factor to counter potential adversaries with Chinese PL-15. It will be multiband, broad spectrum which aids it in survivability and reaching the target. DARPA’s the Triple Target Terminator (T3) programme envisions combined capabilities of Raytheon’s AIM-120 and AGM-88 High-speed Anti-Radiation Missile (HARM). No aircraft is invisible and using stand-off weaponry early in an air campaign to open up weaknesses in an enemy’s air defence will be required even for a fifth-generation fighter aircraft to operate in the area without assuming excess risk.
Heavy Stealth Revolution
Fighters such as the F-35 and F-22 may be stealthy, but their support assets, such as aerial tankers – KC-135R, KC-10A, KC-46A are not. The USAF needs ‘heavy stealth revolution’ for low observable tankers, transports, bombers and ‘flying sensor and communications trucks’, as these will be targeted. The USAF could adapt the new stealth bomber design for the stealth tanker role. It will also give the ability to insert Special Operations teams deep behind enemy lines via a stealthy high-altitude penetrating transport aircraft.
Future Pilot Support Systems
Many new technologies have improved pilot endurance for long flights. On-Board Oxygen (OBOX) generation now obviates the need to have oxygen cylinders and increases endurance. Smart drugs and hybrid supplements increase endurance, stamina, physical strength and alertness levels and regulate the sleep and waking hours and pilot could keep awake for days. Modified genes will convert fat into energy so as to last for long flights. A trans-dermal nutrient delivery system will provide just enough nourishment to keep the body going. The pilot’s physical and mental state will be monitored by sensors to check overload, physiological stress and the same transmitted to ground controller. Light-weight helmets with visor displays for integrated information from all sensors for weapon cueing and shoot command are being developed. Fire-resistant bullet-proof clothing is in use. Voice activated commands for multiple aircraft functions. Secure data-links aided commands will allow radio silence. Research is being done for contact lens-mounted displays that could focus information from drones and satellites directly into eyeballs and helmets that could enable to communicate telepathically. Next-generation helmets will pick up vibrations from the skull and transmit sound directly into the head instead of using traditional microphone-earpiece combine. To fit the body contours, flexible display screens would be of easy-to-bend synthetic material rather than glass.
US Sixth-Generation Fighter Programmes
The US Air Force (USAF) and the US Navy (USN) have been defining their own requirements of a sixth-generation fighter. US DoD began the sixth generation fighter quest in October 2012. DARPA began a study to try to bridge the USAF and USN concepts. Next-generation fighter efforts will initially be led by DARPA under the “Air Dominance Initiative” to develop prototype X-plane. Sixth-generation technologies have been evolving for several years. The USAF and USN will each have variants focused on their mission requirements. The USAF has announced that it will pursue “a network of integrated systems disaggregated across multiple platforms” rather than a “sixth-generation fighter” in its Air Superiority 2030 plan. Dubbed the “Next-Generation Tactical Aircraft”/”Next-Gen TACAIR”, the USAF seeks a fighter with “enhanced capabilities in areas such as reach, persistence, survivability, net-centricity, situational awareness, human-system integration and weapons effects”.
The future system will have to counter adversaries equipped with next-generation advanced electronic attack, sophisticated integrated air defence systems, passive detection, integrated self-protection, Directed Energy Weapons (DEW), and cyber attack capabilities. It must be able to operate in the anti-access/anti-denial environment that will exist in the 2030-2050 timeframe. It is expected to use advanced engines with Adaptive Versatile Engine Technology for longer ranges and higher performance which should be ready by 2030 when fighters would be ready. The newer engines could vary their by-pass ratios for optimum efficiency at any speed or altitude. That would give an aircraft a much greater range, enhanced acceleration and greater subsonic cruise efficiency. The ability to super-cruise may not be a critical requirement, but it will likely be able to with this engine type. USAF and USN have common approach on the engine. The engine companies involved are General electric (GE) and Pratt & Whitney (P&W).
The Rand Corporation has recommended that the USAF and USN run separate programmes to avoid mission compromise and that all joint programmes in the past turned out more expensive. A USAF General remarked that if next-generation air dominance capabilities came from pressing “a single button on a keyboard that makes all our adversaries fall to the ground” it would be acceptable. Concepts from the Air Force and industry have so far revolved around supersonic tail-less aircraft. The aircraft will feature AI as a decision aid to the pilot, similar in concept to how advanced sensor fusion is used by the F-22 and F-35. Stealth is ‘incredibly important’ for the next-generation F-X fighter of the USAF. The USN’s F/A-XX fighter might not be so focused on survivability as to sacrifice speed and payload.
The USAF intends to follow a path of risk reduction by prototyping, technology demonstration and systems engineering work before creation of an aircraft actually begins. The sixth-generation strike capability is not just an aircraft, but a system of systems including communications, space capabilities, stand-off, and stand-in options. The USAF fighter is, maybe larger, but it resembles a bomber rather than a small, maneuverable traditional fighter. Small size, high speed and maneuverability maybe less relevant and easier to intercept. Fighters significantly larger can rely on enhanced sensors, signature control, networked situational awareness and very-long-range weapons to complete engagements before being detected or tracked. Larger planes would have greater range that would enable them to be stationed further from a combat zone, have greater radar and IR detection capabilities and carry bigger and longer-range missiles.
Heavily armed combat aircraft could link itself to the development of the Long Range Strike Bomber. It would include stealth against low or very high frequency radars like those of the S-400 missile system, which would mean airframe with no vertical stabilisers. Lockheed Martin’s Skunk Works has revealed a conceptual next-generation fighter design which calls for greater speed, range, stealth and self-healing structures. Northrop Grumman is looking at a supersonic tailless jet, something never created before due to complexity; it may also be optionally manned.
Other Sixth Generation Programmes
France and Germany have awarded the first-ever contract – a Joint Concept Study (JCS) – to Dassault Aviation and Airbus for the Future Combat Air System (FCAS) programme. The JCS is based on High Level Common Operational Requirements Document (HLCORD) signed in 2018. It identifies the preferred baseline concepts for its major pillars such as the manned Next-Generation Fighter (NGF), Remote Carriers (RCs) and a System of Systems approach with associated next generation services. Both countries want to secure European sovereignty and technological leadership in the military aviation sector for the coming decades beyond 2040. The two-year study should be complete by February 2021. The Future Combat Air System (FCAS) is one of the most ambitious European defence programmes of the century.
BAE Systems’ the Tempest is a proposed stealth fighter aircraft concept to be designed and manufactured in the United Kingdom for the Royal Air Force. It is being developed by a consortium consisting of the UK Ministry of Defence, BAE Systems, Rolls-Royce, Leonardo and MBDA. It is intended to enter service from 2035 replacing the Eurofighter Typhoon. Approximately $2.66 billion will be spent by the British government on the project by 2025. The Tempest will be a sixth-generation fighter incorporating several new technologies. BAE Systems is planning to approach India for collaboration for the design and manufacture of the Tempest. The Tempest could be optionally manned and have swarming technology to control drones. It will incorporate AI deep learning and possess DEWs. The Tempest will feature an adaptive cycle engine and virtual cockpit shown on a pilot’s helmet-mounted display.
China is still evolving its J-20 and J-31. Some Chinese sixth-generation aircraft (J-XX) is referred to as Huolong (Fire Dragon). But as on date, China has serious limitations on radar, avionics and engine technologies. China planned to field it in the 2025-2030 timeframe. In Russia, the FGFA Sukhoi Su-57 is just being inducted and work is on for its sixth-generation aircraft Mikoyan MiG-41. Japan’s Mitsubishi F-3 sixth-generation fighter would be based on concept of aircraft informed, intelligent and instantaneous, technologies for which are under testing on the Mitsubishi X-2 Shinshin test-bed aircraft.
India is still evolving technologies for its LCA design. India’s fifth-generation aircraft, the AMCA, is still on the drawing board and will require foreign help for many technologies. There are a handful of major aircraft engine manufacturers in the world. China and India are still evolving their engine designs and manufacturing abilities. India has been dependent on Russian, French and American engines for long. The DRDO’s Kaveri engine has faced major hiccups for nearly three decades. It has now been decided to seek Safran (Snecma) help to recover the nearly dying project. India also needs help in AESA radars, EW systems, modern weapons, actionable Artificial Intelligence (AI) and other advanced avionics. It is best to adopt a collaborative approach and use economic muscle and high military systems requirements to seek Transfer of Technology. India needs to think ahead lest we get left behind again.