The MiG-31 interceptor, fully loaded, weighs the same as four double-decker London buses, whereas the svelte KAI FA-50 Golden Eagle is four times lighter than the MiG and far cheaper to operate. Modern light fighters, like the Gripen, boast of being credible deterrents to far heavier opponents – but are light fighters as good as their word, and are they worth the effort?Jim Smith investigates.

Throughout the development and application of aircraft to air combat, there have been proponents of both ‘Heavy’ and ‘Light’ fighters. In thinking about why this interest has been sustained, I realised that the close linkage between air combat and aerospace technologies has varied substantially over time, as new technologies have enabled new approaches to air combat, and challenged existing doctrine and policy.

So, we’ll start by considering the different ‘ages’ of air combat, and how the technologies available, and the capabilities they enable, have changed the attributes required of fighter aircraft, and how this has influenced design choices. In looking at the technology aspects, we will find that armament, propulsion, and sensors have perhaps been as significant as aerodynamics in fighter aircraft design, and, at times, more so. For each of the identified ages of air combat, I’ll identify some representative ‘Lighter’ and ‘Heavier’ fighters.

This review will bring out the differing circumstances in which ‘Light’ fighters have been favoured, and allow me to consider what aspects might favour the ‘Lighter’ fighter, and what the trade-offs might be against ‘Heavier’ fighter aircraft. Finally, we’ll speculate about the future, and consider whether ‘Light’ fighters are of continuing relevance, and if so, what their future roles might be.

This article has been prompted by a fascinating input from warspot.ru examining a series of light fighter concepts developed by US Aerospace Engineer Bud Nelson for first Boeing, and later Northrop. My intention is to use this piece to set out the landscape over the relevant period, to aid in understanding those concepts, which I look at separately here.

Before launching into this, a word to the reader. The review of air combat, and the place of the light fighter that follows is an overview. It is not a comprehensive all-encompassing study – were one to attempt that the result would be a book, not a Hush_Kit article. I have also excluded carrier-based fighters, partly because I am trying to keep this reasonably short, but also because carrier aviation tends to favour heavier aircraft, in pursuit of operational flexibility and reach. And I know there are exceptions to this (Escort-carrier-based aircraft, and the Grumman F-11F, for example).

Air Combat – Beginnings. First World War to the mid 1930s

This period began with aviation in its infancy, and ends with the last of the biplane fighters.

The challenges facing designers at the start of this period were propulsion, performance, armament and robustness, and these problems were gradually resolved through technology developments. To succeed in air combat, it was necessary to bring armament to bear on the opponent, preferably in a tactically favourable situation to achieve a rapid and successful outcome. However, it was inevitable that, at times, fighter pilots would find themselves in situations where there was no tactical advantage, in which case, manoeuvring air combat would be required, coupled with the ability to disengage by diving at high speed without hazarding the aircraft.

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Key requirements were a powerful, reliable engine; high speed; a rapid climb rate; excellent turning performance; good armament; and a strong airframe. These requirements shaped the fighter aircraft of the day. Initially, the engines were largely rotary, offering light weight but relatively low power. Armament was a problem. Before the invention of interrupter gear, twin-boom pusher aircraft had a period of success, but once the problem of firing forward through the propellor had been solved, most fighters adopted a biplane configuration with a tractor propellor. Wire-braced monoplanes and triplanes were also used, the former offering higher speed for a given engine power, but perhaps with lower strength, and the latter great agility and climb performance.

As engines became more powerful and reliable, rotary engines were largely replaced with compact and powerful in-line, V-8 or radial engines, most being water-cooled. Over time, increases in power enabled increases in speed and operating altitude, as well as greater endurance. The lighter aircraft emphasised manoeuvrability, and the heavier aircraft speed, altitude performance and armament. Consequently, different tactics began to be employed, exploiting the different characteristics of the aircraft.

• Light Fighters: Sopwith Tabloid, Fokker Eindekker, Nieuport 10. Later examples: Sopwith Camel, Nieuport 17, Fokker Triplane
• Heavy Fighters: RAF SE 5a, Bristol F2B, SPAD XIII, Fokker D VII

Air Combat – The Piston Engine Supreme. Mid 1930s to the end of World War 2

In this period, the introduction of stressed-skin monocoque construction transformed the shape and potential performance of fighter aircraft. Combined with dramatic advances in engine power, the speed, altitude performance, armament, range and versatility of both fighter and bomber aircraft were transformed.

The fundamental requirements remained much the same as in the First World War. To succeed in air combat, it was necessary to bring armament to bear on the opponent, preferably in a tactically favourable situation to achieve a rapid and successful outcome. One difference from WW 1 was that ground-based radar installations and control systems could provide better awareness of the location and strength of airborne attack, aiding pilots in achieving a good tactical position at the start of combat.

Given the numbers of aircraft involved, it was still inevitable that, at times, fighter pilots would find themselves in situations where they were at a disadvantage. Cooperative tactics, coupled with high speed and evasive manoeuvring were required in these circumstances. Other advances, such as improved gunsights, heavy armament, and some armour protection were useful.

Key requirements remained a powerful, reliable engine; high speed; a rapid climb rate; excellent turning performance; good armament; and a strong airframe. To these might be added high octane fuels to enhance engine performance, one of the important technologies pursued by the combatants, whose engine development strategies had a key influence on fighter development.

In the UK, it was necessary to disperse production under the threat of Luftwaffe bombing, and, as a result, a limited number of fighters were used, principally the Hurricane, Spitfire, Typhoon and Tempest. The Spitfire was developed incrementally, more than doubling in both weight and power over the duration of the conflict, and effectively being transformed from a ‘Light’ fighter to at least a significantly heavier one.

Jeffrey Quill, speaking in 1976 at the RAeS Mitchell Memorial Symposium, noted that the Spitfire Mk I had a normal operating weight of 5820 lb, a maximum power of 1050 hp and maximum level speed of 362 mph. The final operational variant, the Seafire 47 had a max. overload weight of 12,500 lb, 2350 hp powerplant, and max. level speed of 452 mph. From a weight perspective, the Seafire 47 delivered its performance at a weight equivalent to a Mk I carrying 32 passengers (with baggage).

The Typhoon was developed into the Tempest and both aircraft represented a discontinuous increase in weight, power and performance over the Hurricane. The Mosquito and Beaufighter exploited their size to be successful heavily armed multi-role aircraft. These developments were very dependent on engine technologies, notably multi-stage supercharging, and the use of advanced material solutions to allow sustained high-power operation.

German developments followed a similar initial pattern, with incremental development of the Bf 109, and a jump in capability to the Fw 190 and incremental developments of that aircraft, with the Dornier 335 Pfeil being perhaps their ultimate piston-engine fighter, albeit too late to enter service. German engine developments gained advantages through direct fuel injection and clever internal design, but were handicapped by the inability to access some materials, and limited supply of high octane fuel.

The US developed, with the British Merlin engine, the excellent Mustang as a long-range escort fighter, but, aided (or perhaps compelled) by their development of the turbo-supercharger, embraced the ‘Heavy’ fighter, with the P-38 Lightning and P-47 Thunderbolt being the obvious examples. The US also made extensive use of large and complex radial engines, which were a feature of their bomber aircraft, and many of their Naval aircraft.

During this period, the development of Airborne Intercept (AI) radar enabled the development of effective night fighters, leading to a new class of radar-equipped heavy fighter, generally twin-engined and with multiple crew, due to the size and weight of early AI radars.

• Light fighters: Early Spitfire Marks; Messerschmitt 109; Yak 3; Curtiss P-40
• Heavy fighters: Late Mark Spitfires; Hawker Typhoon and Tempest; Focke-Wulf FW 190D; Dornier Pfeil; P-38 Lightning; P-51 Mustang; P-47 Thunderbolt
• Night Fighters: Bristol Beaufighter; De Havilland Mosquito; Junkers Ju 88; Heinkel 219 Uhu; Northrop P-61 Black Widow

Air Combat – The Early Jets – 1944 to the mid-1950s

Towards the end of World War 2, notwithstanding a deteriorating military situation, and shortages of critical materials, German aerodynamic and propulsion research developments, led to another discontinuous jump in capability, with the Me 163 and V2 exploiting rocket propulsion, and the Me 262 emerging as a capable jet fighter. Parallel jet engine research in development led, in the UK, to the Gloster Meteor twin-engine jet fighter, which saw limited service in the closing months of the war.

In an interesting parallel to the early aircraft of WW1, early jet aircraft development was critically dependent on the performance and operational life of their engines. The relatively low thrust of early jet engines resulted in the twin-engine configuration of the Messerschmitt 262, but this was perceived to be an expensive and difficult to produce aircraft.

Competition for a lighter, simpler, single-engine fighter led to the development of the Heinkel 162 Volksjäger. This aircraft was developed in just 90 days, and used wood in the construction of the wings, fins and some other components. As a result, surprisingly large numbers were built in the short time between its first flight on 6 December 1944, and the end of the war in May 1945.

Following the Second World War, aircraft manufacturers and research agencies in (primarily) the US, UK and USSR sought to exploit captured German research data and research scientists to marry advances in jet engine design to the many and varied airframe concepts that had been considered, and in some cases, built, in Germany. Principle among these technologies was the swept wing, but flying wing, delta and variable-sweep wings were also investigated.

In the period considered, air combat was still primarily conducted by day, using cannon as the primary armament. Unguided rockets were available, but their use was primarily in attacking ground targets, or conceivably against bomber formations. This was a time of rapid development on jet fighters by all the major powers. In the US, the principal early jet fighters were the F-80 Shooting Star, F-84 Thunderjet and the F-86 Sabre. The UK used the Gloster Meteor and the de Havilland Vampire, with the Hawker Hunter and Gloster Javelin in development. The USSR used British jet engine technology to develop the superb MiG-15 and -17, following on from early straight-winged designs such as the Yak 17.

At the same time, the realisation of the threat of night bombing, and of atomic weapons, led to a need for all-weather day and night fighters, using onboard radar systems to locate targets. The first jet night fighter was the Douglas F3D Skynight. Large, and relatively slow, this aircraft had the distinction of making the highest number of US aircraft kills in the Korean War.

• Light Fighters: de Havilland Vampire; F-86 Sabre; Mikoyan-Gurevich MiG-15; MiG-17; Heinkel Volksjäger
• Heavy Fighters: Messerschmitt 262; Douglas F3D Skynight;

Air Combat – Radar and Guided Missiles – Mid-1950s to the 1970s

In this period, spurred by a continuing post-WW2 contest of ideologies between US-led capitalism and Russian and Chinese Communism, giving rise to conflicts in Korea and Vietnam, and, following those, a continuing Cold War, aerospace technology continued to develop rapidly. The aerodynamic, propulsion and handling problems of the early jets were largely resolved, resulting in significant numbers of capable supersonic jet fighters becoming available.

On the other side of the coin, however, the improvements in Western fighters were mirrored by their opponents, and, to further complicate the situation, nuclear weapons proliferation resulted in much greater threats, initially from manned bomber aircraft. The first move to counter this emerging threat was to move away from the use of cannon as the primary anti-air weapon to the use of air-launched guided weapons instead. Coupled with the development of compact and effective fighter radars, heat-seeking or radar-guided air-to-air missiles (AAM) could allow fighters to engage each other, and bombers, at much greater distances. This not only offered greater prospects of survivability for the fighters, but also allowed the possibility of disrupting bomber attacks before they could reach their targets.

To achieve the capability required, fighters became larger, heavier, more powerful, more complex, and more expensive. But also much more capable, with the air-to-air effectiveness very dependent on missile capabilities, but the additional size and weapons capability allowing the flexibility to use the same airframe in strike and air-to-air roles.

In this period, a good US exemplar would be the F-4 Phantom II, which became a long-serving air defence and strike aircraft for many air forces over decades of service life. Carrying shorter range infra-red (IR) guided Sidewinders, and longer range, radar guided Sparrow missiles, with two crew, radar and two powerful J79 engines, the F-4 was developed for the US Navy, but later adopted by the USAF and proved to be exceptionally versatile in service. Initially flown with no cannon armament, experience in Vietnam led to the addition of this for later aircraft.

The UK were early entries into the world of missile-armed fighters, with the Gloster Javelin and the BAC Lightning both able to carry the Firestreak IR-guided missile, and the Lightning also carrying the longer-range Red Top IR-guided missile.

The USSR essentially replaced earlier MiG fighters with the fast and small MiG 21, a type which was incrementally developed over the years leading to innumerable variants, generally featuring additional fuel and improvements in the mission system – the radar, armament and defensive aids that enable an aging design to stay relevant.

Early air to air missiles such as the Sidewinder and Firestreak featured infra-red guidance. Initially IR AAM engagements were limited to stern attacks, but gradually became more flexible in operation as missile seekers improved. IR-guided missiles had an advantage over the early radar-guided missiles, as they required continuous illumination of the target by the fighter’s radar, which limited the pilot’s scope for manoeuvre.

In this environment, despite the major powers developing a range of highly capable heavy fighters, a class of small, agile, air defence aircraft emerged. These aircraft served two main purposes: meeting the needs of smaller Nations that required air power for defensive purposes, rather than to attack their neighbours; and to equip Client States of the major powers. These Client States were those countries, generally allied to the US or the USSR, that were supplied with large numbers of reasonably capable aircraft, at least in part to provide a means of the major powers distancing themselves from combat involvement.

Export sales of these lighter fighters was important in maintaining, and in some cases growing, industrial aerospace capability, as well as providing economic benefits, and maintaining Client States’ dependency on the major powers. In this context, the Mirage III became an important aircraft for France, as it proved both capable, and popular with non-aligned countries, and was exported in large numbers.

Light Fighters: F-104 Starfighter, Northrop F-5, Mirage III, MiG 21

Heavy Fighters: F-106 Delta Dagger; BAC Lightning; F-4 Phantom; SAAB Viggen; Sukhoi Su 15

The current day: BVR combat and Stealth

Over the past few decades, there has been a dramatic shift in air combat policies away from manoeuvring visual air combat – ‘dog-fighting’ to long-range engagements enabled by advances in guided weapon propulsion and seeker technologies, aircraft radar technologies, and the use of off-board information supplied through networked communications.

As a result, the desirable form of air combat is now beyond visual range, or BVR. Ideally, the fighter aircraft possesses longer-range missiles and sensors than its opponents, and has better situational awareness, allowing it to identify and engage opponents at distance. These combats preferably take place when the opponent is at a range where he is in the ‘no escape zone’ of your missile, but while you remain outside his ability to engage your aircraft. 

Key enablers for BVR combat have included the development of advanced radars, particularly those featuring Active Electronically Scanned Arrays (AESA). These radars can search for new targets, track previously detected targets, and provide datalink support to AAM after launch. Other advances in AAM technology have given greatly extended range capabilities to missiles like the MBDA Meteor through the use of rocket-ramjet propulsion systems. Missile seekers have also improved in range and aspect capability, enabling IR missiles to make all-aspect attacks at significant range.

One mechanism giving advantage in this sort of combat is to have very low detectability so that the opponent cannot locate and track your aircraft. Low radar signature helps to achieve this, but it must be remarked that the low signature also has to be achieved against Infra-Red sensors as well as a wide range of radar sensors which may be feeding information to opposition fighters.

Achieving a low radar signature requires the majority of weapons to be carried internally, increasing the size of the aircraft, limiting the number of weapons available, and potentially using space that might have been used for fuel, but delivering the intent of ‘first look, first shot and first kill’ capability.

Although this environment is challenging, there still remains space for the lighter fighter. As the systems and missiles have improved in capability, it has become possible to equip relatively small single-engine aircraft with capable radar, networked information systems and long-range weapons. Such aircraft are particularly useful as Air Defence rather than Air Superiority assets, largely because their small size limits the internal fuel that can be carried.

Light Fighters: Mirage 2000; SAAB Gripen; HAL Tejas

Heavy  Fighters: F-15 Eagle; F-20 Raptor; Shengdu J-20; MiG 29; MiG 31; Su-35 and derivatives; Su-57; Dassault Rafale; PANAVIA Tornado; Eurofighter Typhoon

Light Fighters: What’s in it for me?

When we review the development of air combat, we can observe that despite the enormous changes in technology that have occurred in the last 110 years or so, ‘Light’ fighters continue to be developed alongside heavier alternatives.

This section identifies the main drivers for this, and shows they are not as simple as the assumption that light weight gives greater agility. It does, but there other reasons that may make the lighter alternative attractive, as well as many reasons which may favour the flexibility gained through the use of a larger and heavier aircraft.

• Technology

At a couple of points in the development of air combat, technology constraints have favoured the ‘Lighter’ fighter. These two points were:

• at the start of the First World War, where immature engine technology favoured the light fighter, and the greater performance and agility that came with light weight
  • at the beginning of the jet age, where the higher speed and altitude achievable with jet engines was a prize worth having, but the low power available favoured a small, light design.

• Cost

While deeply unpopular with Industry and with requirements staffs, the truism that heavier aircraft cost more, has not been seriously countered. Every attempt to produce an aircraft that breaks this paradigm has failed. This may be considered a bold statement, but I stand by it, at least until I see evidence to the contrary.

The cost-weight relationship is a key tool used by Treasury Departments to put pressure on new aircraft development proposals. Historically, the correlation  between weight and cost has been relatively robust, and has allowed early and penetrating analysis of suggested unit costs.

Industry and operators will argue that new technologies allow lighter airframes and more capable systems, delivering more capability for a given weight. Treasury sceptics will point to the cost and risk of developing new airframe materials, and the cost and complexity of validating and certifying software intensive complex systems. In the end the result is usually a draw, with pressure being placed to reduce mass as a way of reducing cost – not least because weight and cost are both much easier to measure than capability.

Low cost is desirable, as greater numbers of aircraft can be procured from a given budget, and, if care is taken at the design stage, cheaper, simpler, lighter aircraft might even prove to be cheaper to operate.

• Production

Dr Ron Smith documents, in his British Built Aircraft 5-part series, the large numbers of aircraft built during World War I. In the period of that conflict, the British produced some 55,000 airframes; the French nearly 70,000 aircraft and more than 85,000 engines; the Germans nearly 50,000 aircraft and about 40,000 engines, with significant numbers also being produced by the USA and Italy. In four years, the equipment of the RFC/RAF grew by a factor of eighty, and the production rate by a factor of fifty.

The Second World War prompted an even greater surge in both technology and production capacity. Figures available for aircraft production in the 1939 to 1940 period do vary, but British, German, Soviet and American production numbers were in the order of 130,000, 120,000, 160,000 and 325,000 respectively.

Some countries became concerned about the availability of strategic materials for aircraft production, leading, at least in WW 2, to the exploration of lighter fighter aircraft, using wood rather than metal as the principal material for their construction. Examples of this include the British Miles M20 and Mosquito; German Ta 154 and Heinkel Volksjäger; and American Bell XP-77.

• Capability

Can cheaper, lighter, aircraft do the job?

Firstly, it should be said that air combat up to the time of the Korean War was conducted principally in daytime and under visual conditions. In these circumstances, lighter fighters had the potential to offer higher manoeuvrability compared to heavy fighters, but would perhaps have lower maximum speed and range, and generally have lighter armament.

These capabilities could, and did, lead to different tactics being employed, with light fighters seeking to exploit manoeuvrability, while heavy fighters used high-speed passes with minimum manoeuvring air combat.

As a comparison between a heavier, and a lighter fighter, consider the Hawker Hunter and the Folland Gnat, both designed in the UK. This example is drawn from Jet Fighter Performance, Korea to Vietnam by Mike Spick, Ian Allan, 1986.

The Hunter was a relatively heavily armed day fighter with four 30 mm Aden cannon, which entered RAF service in 1954, and was extremely successful once fully developed. Widely exported, and respected for its good handling, a few examples remain in use today. The primary intent of the design was the engagement of Russian bombers, but roles inevitably diversified over time, and the aircraft was very often used in the ground attack role. In service, it was complemented by the heavier Gloster Javelin night fighter, with missile armament, two crew and a large airborne intercept radar.

The Folland Gnat was broadly contemporary with the Hunter, its initial prototype, the Midge, making its first flight in the same year that the Hunter entered service. The Gnat was about 2/3 of the size of the Hunter, and weighed about 40% of the Hunter with a gross weight about 3 tonnes, compared to the Hunter’s 8 tonnes.

With closely comparable wing loading, slightly higher aspect ratio and 20% greater thrust to weight ratio, the Gnat had exceptional handling and higher climb rate than the Hunter, but only half the firepower, with two rather than four 30 mm cannon, partly because its role was seen as air defence against fighters, rather than bombers. In air combat with the Indian Air Force, the Gnat proved to be both agile and effective, hard to track visually, and with good climb performance.

The job to be done by the fighter aircraft changed dramatically with the introduction of capable, long-range AAM to air combat. Capability in current air combat situations has been explored in a couple of previous articles for Hush_Kit, looking at what makes a good BVR fighter, and at the future of air combat. These can be found at the following links:

Top 10 beyond visual range fighter aircraft 2018: selection process and the science of BVR combat

This discusses what capabilities you need to provide Air Defence, and to establish and maintain Air Superiority, and discusses how these capabilities drive towards somewhat different requirements.

Re-read this article in forty years time: We predict the future of aviation

This covers the future of air combat, emphasising the system-of-systems approach on which the major players appear to be converging as a means of delivering air power, in the broadest sense.

Some key points arising from these articles are:

• A distinction between Air Superiority, where the desire is to establish temporary or enduring air control over hostile territory, and Air Defence, where the focus is on deterring and defeating enemy air attacks and on ensuring air control over one’s own territory;
• The importance of sensors and systems in enabling long-range engagements whenever possible, using long-range and highly capable missiles;
• The importance of the electronic domain in ensuring and maintaining situational awareness across the battlespace, as well as providing opportunities to deceive and nullify opposition sensors and situational awareness;
• The emergence of low observable operations as a pervasive feature of future air operations.

Big as the damn world: Strategic considerations

Some geo-political and geographical considerations have worked in favour of lighter fighters. For some countries, engaged perhaps in a contest of political ideologies and looking with suspicion at others, it has been useful to build alliances with smaller countries, under the guise of providing defensive aid. Yes, we are looking at the USA and the USSR in the period of the Cold War, but this is not to exclude other possibilities.

A number of benefits flow from supplying their friends and allies with large numbers of light fighters, including:

• provision of a defensive umbrella so that if local disputes erupt into conflict, this can be kept remote from the homeland;
• maintaining the allies and friends (Client States) in a position where they are dependent on the homeland for support, hence helping to ensure political alignment;
• limiting the capability to primarily defensive, rather than offensive capabilities, aiding political stability;
• and providing business to maintain homeland armaments industries.

Light Fighters – Advantages

Summarising, we can observe the following benefits of light fighters:

• Low cost
• Simplicity, leading to
  • more rapid production
  • higher reliability
  • easier training
  • and availability in greater numbers
• Small size and weight, leading to
  • greater agility
  • potentially higher climb rate and performance
  • less visual signature
  • potential ability to use shorter airstrips and more austere bases
  • delivery of complementary tactical capabilities to heavier fighters
• Potential to further broader strategic aims
  • The Client State approach
  • Support to Industrial capability

Trade-offs compared to heavier fighters

One of the attributes strongly linked to the weight of a fighter is size, and, via size, the surface area and volume. This might seem academic, but for the fact that it is the volume of the aircraft which is available for payload and fuel.

In the case of a fighter aircraft, the payload is not just armament, but also sensors and systems, a myriad of which are critical to modern fighter aircraft, and some of which have certainly been critical for older designs. Obvious examples include radar, communications equipment, optical sensors, defensive aids like chaff and flares, electronic combat equipment such as jammers, missile launch and approach warners.

The surface area of the aircraft is most evident in the wing area, and the relationship between this and the weight of the aircraft will play a key role, not just in determining turn performance, but also take-off and landing requirements, as well as space for the carriage of external stores and sensors.

The fuel available for the aircraft is directly linked to the internal volume available – i.e. that space not already occupied by the structure, powerplant and intake system, undercarriage, pilot and the other systems which deliver flight control, armament management, displays and so on.

To generalise, a larger, heavier, fighter will be able to carry a greater proportion of sensors and fuel than a smaller, lighter aircraft, and is also likely to be able to carry a wider range of armament. However, it is likely that the wing loading of the aircraft will be higher, implying lower agility and greater take-off and landing requirements.

Sweating the elephant: Design and policy choices

Of course, all these aspects are subject to choices by the designer. If the agility is not sufficient, larger engines will help, but will consume more fuel. Multi-axis thrust vectoring can provide great agility but will increase weight and engine and flight control system complexity. Similarly, more complex wing designs incorporating variable sweep and high lift devices can improve take-off, landing and manoeuvre performance, but will come at the expense of complexity and additional weight.

These design choices have tended to lead to heavier fighters, with more powerful engines, driven by two principal factors. Firstly, there is a desire to engage at greater range, using long-range missiles. This is enabled by the use of powerful sensors, and assisted through the integration of both onboard and off-board systems, to aid the missile attack, and to confound enemy missile attack.

Secondly, there is a desire to reduce the size and cost of armed forces, so for most air arms there is continuing pressure for each aircraft type to be more capable than the last, again tending to increase size, weight and complexity, which in turn drives up the size of powerplant required. Paradoxically, the result is not just increased capability, but increases in the unit cost of the aircraft, although fewer will be purchased, and savings in manpower may also be made.

Investing in reduced signature, or low-observable aircraft, has three effects. Success means greater capability because of the ability to engage when the opposition is unaware of your presence, or, perhaps, your location. Along with this success comes significant cost increases due to the need for advanced production and maintenance processes, and the specialist materials required. In addition, internal carriage of stores is likely to result in a competition for internal volume between fuel and weapons, which may in turn impact on external aerodynamics and performance.

Measures to combat the trend of ever increasing cost, complexity and weight   include extensive use of airborne refuelling aircraft, which can enable extended patrol times without increased fighter size and weight. However, provision of extensive air-to-air refuelling introduces its own vulnerabilities and costs, particularly if offensive operations, rather than air defence, are to be conducted. A force-mix approach may also be used, with high-end air superiority roles restricted to a smaller number of high-performance strategic fighters, while lower-performance or shorter-range aircraft are used for strike operations or local air defence tasks.

Most major forces are now adopting a system of systems approach, devolving some systems to co-operating unmanned assets with roles varying from electronic combat to strike, air refuelling, communications relay and, perhaps in the future, air combat. Geography, and strategic intent also have a part to play here. Defence of a large homeland with many possible directions of attack, is likely to require high-speed, long-range interceptors, probably backed up by numerous smaller and reactive fighters providing local air defence against possible ‘leakers’ that have evaded interception.

Aspirations for global air dominance drive in the direction of air superiority systems, creating an environment for long-range strike operations, using manned or un-manned assets, and potentially, significant numbers of tactical fighter and strike assets to provide air cover and support to surface-based operations.

Will light fighters continue to be relevant?

Earlier in this article, I referenced a couple of other pieces covering BVR air combat, and future developments in air combat. In general, these articles suggest a future drive towards combat persistence and range, coupled with advanced sensors, long-range weapons and stealth to deliver Air Superiority. This would be backed up by a mix of advanced sensor and electronic combat platforms, and an extensive networked information capability. Strike missions would be delivered by a mix of manned, unmanned and autonomous systems, with target location, confirmation and dissemination a key enabler.

At first glance, these points suggest that there might be little room for ‘light’ fighters in delivering these capabilities, but that would be to ignore the opportunities which may lie in the systems-of-systems approach. For example, options may exist to use shorter-range, highly reactive and manoeuvrable light fighters to provide Air Defence capabilities, as well as protection for high value assets. These would exploit third party sensing and targeting system to ensure rapid and effective reaction to threats, or to provide reactive tactical support to ground forces.

In addition, as identified in the BVR combat article, some Nations have a need for Air Defence to deter potential aggressors but have no desire to impose their political ideologies outside their own borders. For such nations, a small, networked air defence aircraft, equipped with advanced radar, infra-red tracking capability, and long-range anti-air weapons might be sufficient, noting that any such aircraft would also have some capability as a strike aircraft if necessary.

From a capability perspective, for those Nations which do require an ability to deliver Air Superiority outside their own borders, a light fighter might provide a niche capability, focusing on responsive air defence, but also providing additional numbers to strengthen tactical support. In addition, of course, such an aircraft might also provide sufficient capability for regional Client States, as outlined earlier.

Industrial considerations are also important. Many nations enter the world of aerospace manufacturing through the production of advanced training aircraft, and over time, manufacturing capability improvements can bring the production of light fighters within reach. Given a reasonably benign operating environment, this may be sufficient to meet National needs, noting that if necessary, manufacturers of more advanced aircraft will generally be only too enthusiastic to fill any remaining capability gaps.

An emergent need for light fighters might be in the loyal wingman concept, if applied to air combat. By removing the pilot and his support systems, a new class of highly manoeuvrable unmanned weapons platforms might emerge, with higher manoeuvre capability, and, in extremis, expendable. Such systems might function as a disruptive element to force combat with enemy defensive assets, causing them to expend weapons and fuel, and diminishing their ability to respond to air superiority or strike elements.

Are Light Fighters worth the Effort?

It depends who you are. For a large nation seeking to be at the cutting edge of everything, your need might be rather niche. Advanced trainers that can be militarised and exported or used for initial air combat training – perhaps.

A nation with a large geographic area offering many possible lines of attack for an opponent – almost certainly useful as an adjunct to your reactive strategic fighter force; to cover less likely avenues of attack, and greater areas of your airspace; and as Air Defence assets for your Client States.

A nation seeking to enter the aerospace manufacturing arena – certainly.

A manufacturer – perhaps, but perhaps as a partner in a risk-shared programme, or as a means of gaining access to new markets.

As a DARPA equivalent – Highly likely, looking for novel ways to reduce the cost of low signatures; increase agility without compromising signatures; examine the human factors, technologies and robustness of unmanned air combat and loyal wingman concepts.

–Jim Smith