Fifth Generation Fighters [PDF]

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CONTENTS



04INTRODUCTION



SECTION 1 GENESIS OF THE BREED 1 GENESIS OF THE 08CHAPTER GENERATIONS



The first jet fighters took to the skies during the Second World War but after 1945 the development of airframes and engine accelerated.



70CHAPTER 10 MIG 1.44



It’s almost as futuristic as you can get and still retain development status as a radical test bed for new technology with 3D nozzle deflection.



78CHAPTER 11 SUKHOI SU-47 BERKUT



The Russian heavyweight fighter manufacturer developed a radical forwardswept wing test aircraft and provided a potential denied only by political vacillation.



15CHAPTER 2 GENERATION GAP



86CHAPTER 12 SUKHOI T-50/SU-57



22CHAPTER 3 GENERATION RISING



96CHAPTER 13 CHENGDU J-20



SECTION 2 DESIGNING FOR THE FUTURE



102CHAPTER 14 SHENYANG FC-31



Following the first two generations of fighter aircraft, technology pushed the boundaries of speed and capability, turning dogfighters into missile platforms.



As global confrontation threatened in the height of the Cold War, proxy conflict brought a surge in technological innovation.



30CHAPTER 4 THE SEARCH FOR STEALTH New threats from robust air defences stimulated a drive toward low observable combat aircraft and a whole new way of designing fighters to survive.



38CHAPTER 5 UNDER THE SKIN



This definitive Russian fifth-generation fighter emerged from a long line of developed variants originating with the Su-27 family to exhibit unique capabilities.



Almost out of nowhere, China displayed breakthroughs in stealth and high performance in a fighter that may not be all it seems.



6 SURVIVAL IN 42CHAPTER HARM’S WAY



110CHAPTER 16 CONTENDERS



SECTION 3 THE FIFTH GENERATION



122CHAPTER 17 FIGHTING THE FIFTH



First of the fifth, this new fighter that emerged from early work on stealthy aircraft with low observables became the backbone of the air dominance threat.



8 LOCKHEED MARTIN F-35 54CHAPTER LIGHTNING II



Whereas the F-22A was built in limited numbers for special incursions, the first mass production fighter of the fifth generation offered three variants for different services.



Printed by: William Gibbons and Sons, Wolverhampton ISBN: 978-1-911276-58-6 © 2018 Mortons Media Group Ltd. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage retrieval system without prior permission



FRONT COVER IMAGE: America’s Lockheed Martin F-22, F-35 and China’s J-20 provide capabilities defining them as fifth-generation fighters, with several leading contenders presenting aircraft already flying. (VIA DAVID BAKER)



SECTION 4 ASPIRANTS, THREATS AND FUTURES



106CHAPTER 15 NEW ENTRANTS



7 LOCKHEED MARTIN 46CHAPTER F-22A RAPTOR



Published by: Mortons Media Group Ltd, Media Centre, Morton Way, Horncastle, Lincolnshire LN9 6JR. Tel. 01507 529529



Seeking a small fifth-generation fighter with potential for export, China has produced an F-35 lookalike with not all of the variability.



When aircraft went stealthy, control systems had to keep up with unstable aircraft designed with advanced avionics and advanced flight control systems.



New sensors to improve situational awareness matched advanced radars capable of seeking out targets beyond visual range for longdistance defence.



Author: David Baker Design: Lucy Carnell, atg-media.com Cover design: Holly Furness Reprographics: Angie Sisestean Production editor: Pauline Hawkins Publisher: Steve O’Hara Advertising manager: Zoe Thurling Publishing director Dan Savage Marketing manager: Charlotte Park Commercial director: Nigel Hole



Several countries aspire to take a place at the top table of fifth-generation types, some might make it but a few never will get that seat.



Existing aircraft, long in the tooth and honed in war, are receiving upgrades that will give them capabilities very close to bespoke fifth-generation types.



With technical challenges to their survival, the fifth generation are having to upgrade their capabilities to retain their unique role in conflict.



18 ENTER 127CHAPTER THE SIXTH



What can we expect with the sixth-generation fighter generation and how will they integrate with a warfighting scenario so very different from that of today?



62CHAPTER 9 MIG-35



Some say this Russian fighter is not of the fifth generation but its capabilities are growing and it is closer than most other types to the golden accolade. FIFTH GENERATION FIGHTERS



3



INTRODUCTION



Introduct 4



FIFTH GENERATION FIGHTERS



ABOVE: Russia’s new fifth generation, represented by the Sukhoi Su-57. (VIA DAVID BAKER)



T



for a photo-shoot. (USAF)



tion



he story of the fifth-generation fighter is a product of several evolving steps, advanced forward by technology, engineering, science and investment – from politicians, military services and industry. But to understand how the fifth has evolved it helps to see from whence it came and how 40 years of engineering and science helped build a bridge from the piston-engine fighters of the Second World War to the stealthy fighters of today, agile and equipped for electronic warfare as an integral part of their design. It is all about the never-ending quest for air superiority. In the air combat arena of the 21st century, air superiority has stretched toward air dominance – a goal sought but hardly ever likely to be achieved completely. Air superiority, as defined in fighter terminology, requires total control of the skies and that has already been achieved in some recent conflicts, usually employing highly trained, skilled and experienced fighter pilots pitted against lower levels of efficiency and effectiveness, either through poor training or an absence of experience. Air dominance, on the other hand, is about eliminating the ground threats too. And that is more difficult to achieve. Over the last 80 years, jet aircraft have evolved from sluggish contemporaries of prop-driven fighters, hardly keeping up with the performance of piston-engine powered combat planes, to supersonic, highly agile, electronic platforms launching weapons to targets in the air or on the ground beyond visual range. A dynamic in that line of progress has been the extraordinary advances in the science of flight added to outstanding breakthroughs in exotic technology. Joined together, it has been a powerful stimulus to successive generations of combat aircraft. It is quite common to refer to jet fighter aircraft within successive generations of increasingly sophisticated capabilities, beginning with the first fighters and progressing to the very latest air dominance, fifth generation, types.



But in reality there is no definitive agreement on just what those generations represent and where each generation starts or by what criteria it ends. Each source consulted has its own interpretation of what constitutes a specific generation, broadly defined as sequential steps from the first jet fighters introduced to operational service to the present and beyond. What follows in the opening chapters after this introduction is merely one sequence of categorisation defined by steps in technology, in aircraft design and within the evolving changes that have characterised steps from first to fifth in a succession of generational types framed by performance and capability. But there is no binding agreement as to where to draw the divisions between generations of fighter type, this being only one interpretation open to debate and redefinition. Yet, for all the boundary uncertainties, it is helpful to begin with a basic understanding of how the generations matured.



SMALL BEGINNINGS Discounting experimental, conceptual development aircraft and prototypes which never saw operational service, logically the first generation has to begin with the Messerschmitt Me 262, the world’s first operational jet fighter, and the Gloster Meteor, its contemporary and in many ways a superior fighter. Where the Germans excelled in aerodynamics and planform design, the British had more reliable and, arguably, better engines. Pilots who flew both Me 262 and Meteor concluded that a German jet fighter with British engines would have been an unbeatable combination, a view expressed to this author by General der Jagdflieger Adolph Galland, an arch exponent of the Schwalbe. British and German superiority was not to last, however, as the vastly superior financial resources of the United States quickly gained on the lead of European manufacturers. Frequently it came with the help of those assets – willingly offered up by the UK and ‘liberated’ from FIFTH GENERATION FIGHTERS



5



SECTION 1 – CHAPTER 1



ABOVE: First of the fifth, an F-22 Raptor peels away during a close pass. (USAF) Germany – providing encouragement to a major programme of development and expansion as a Cold War descended over the victorious powers on a legacy of the Second World War. The journey from that day to this has seen the end of the Soviet empire and the birth of a new race – not for direct military confrontation (although that seems at times to reappear if only temporarily) – but for technical and commercial advantage in consolidating industrial and political alliances in an effort to deter equals and increase exports. Aircraft now have a dual function – to return development investment through international sales as well as consolidating indigenous defence needs. The fifth generation has evolved gradually over the last 30 years, and some types conceived then are only now emerging for service introduction. The extended development of the Joint Strike Fighter is a case in point, built as a platform upon which can be grafted a wide range of new systems, sensors and avionics equipment which will undoubtedly see it succeeding through 5+ and 5++ evolutions. Yet the aircraft it will operate with are changing too and the way in which future air combat will integrate with new capabilities, and changing requirements, is deeply challenging to the air planners of today and the pilots of tomorrow. When the F-35 was conceived through the JSF programme, the B-2 had not yet entered service and its presence in the mix has only marginally changed the way the 6



FIFTH GENERATION FIGHTERS



F-35 is perceived. But that is about to change. Few could have foreseen the tidal wave of unmanned aerial vehicles (UAVs) and unmanned combat air vehicles (UCAVs) which have greatly influenced the air combat arena in the last decade or so. As a first-tier addition to primary reconnaissance and surveillance capabilities they are without equal and the fifth-generation fighter will operate on, and because of, information received after a strike package has left the runway. Battle management has shifted from ground stations in the rear, perhaps several hundred kilometres from the battlefield, to airborne command posts within region, to real-time information and data streams flowing on a continuous basis from UAVs and satellite-based information systems, some of which will use voice communication and commands from enemy sources to relocate mission vectors and targets. New air vehicles are emerging now which may require extended support from fifthgeneration types in a multirole application to clear ground threats for incoming strike packages with not-so-stealthy components, manned and unmanned, following through on a real-time/ re-targeting basis. It was for this kind of stealthy penetration, loiter, re-targeting and strike capability that the B-2 was originally designed. A primary objective of the stealthy bomber was to penetrate Soviet/Warsaw Pact airspace and hunt down and destroy mobile ICBMS



before they could launch and send their nuclear warheads to distant targets. With the end of the Cold War that requirement changed – and so did the configuration of the aircraft for a new role, redefined by the collapse of the Warsaw Pact as a unified threat against NATO forces. In less than a decade the B-21 Raider will be in service and its mission too may evolve over time. As a very long range, nuclear-capable strike system it will be a target that enemy forces on the ground and in the air will attempt to hunt down and it may not survive unattended by networked assets managed by fifth-generation fighters. Which is the very essence of what defines a fifth-generation combat aircraft: a command control node for handling a range of in-area assets toward a unified objective broken down into several separate threat regimes. It would be a bold person indeed who images the B-21 as a fixed-mission asset and it will surely change the nature of air warfare as it bridges the divide between autonomous and piloted systems. But there is more to the fifth generation, as it introduces a range of capabilities which had no precedent on fourth-generation types, specifically the advanced level of current low observables technology and the acclaimed benefits of thrust vector control. Even to the extent that some work has been done on examining the possibility of adapting the Typhoon to carry thrust-vectored nozzles. This aircraft is uniquely designed for high agility and has only latterly



come to have a multirole capability – much to the annoyance of some who wanted to keep it clean and mean! And the costs generally of these new technologies will come down with high production runs, as we are already seeing with the F-35, which is already cheaper than some of its fourth-generation competitors for orders.



A NEW GENERATION Beyond the fifth there are redefinitions as to what constitutes a fighter, perhaps best described as a combat aircraft exclusively dedicated to annihilating enemy air threats in whatever form they take, while attacking ground targets merely as a means of survival rather than for some tactical or strategic aim; air dominance being a subset defined by self-preservation rather than as some independent military objective. In that regard it brings us full circle to the definitions used at the beginning of this introduction, namely to define air superiority as the ‘silver bullet’ for opening the battlespace to options for friendly land, sea and air forces intent on neutralising hostiles – be they organised gangs of rebel hordes or major powers seeking territorial or military advantage. Which brings us to the sixth generation, logically an uncharted future defined by technology, yet to be invented, and to the changing face of the battlespace map. One-third of global military expenditure is funded by the Unites States alone, on national programmes in support of land, sea, air and space forces. What the US develops affects the remainder of the world and as a leader in air combat capabilities, the United States will be largely responsible for defining the future of the air combat arena – for several decades to come, despite assurances that major players such as Russia and China are catching up. As we define in Chapter 17 Threats to the Fifth, we explore the encroaching importance of space-based assets in providing the means to enable fifth-generation aircraft to operate with superior technical capabilities and to so define the sixth generation. Aircraft and GPS-guided weapons depend on satellites to honour their promises, when called upon to deliver, and the collective net-centric space is only going to increasingly rely on Earth-orbiting satellites to maintain



ABOVE: A new era of electronic warfare was born during the Second World War, epitomised here by a Messerschmitt Me-110G-2 at RAF Museum Hendon, England. (VIA DAVID BAKER) that advantage over fourth-generation types. It has been a long time coming. From the 1960s, military satellites have been used to enhance navigation, expand communications and inter-service links around the globe, map potential enemy targets with a precision measured in metres rather than miles and to construct an alert network on a spread from early-warning of imminent nuclear annihilation to the intelligence required to command and control forces in the air over hostile territory. The next step will be a constellation of satellites which can directly connect swarms of unmanned and piloted aircraft and for these activities upgrades to existing fifth-generation types will be sufficient to embrace the new technology, much of which is coming from the commercial sector. In the last 35 years, the detailed intelligence from satellites essential to accurate targeting and map updates enabling air operations in and around contested airspace has



ABOVE: A fourth generation Mig-29M with qualities close to those of a fifth-generation fighter. (VIA DAVID BAKER)



shifted from highly classified 100% governmentrun programmes to a commercial sector where 70% of the information used by intelligence services is derived from private companies. When that shift migrates to communications as well, the sixth generation will communicate directly through vast constellations of several thousand commercial satellites in relatively low Earth orbit. These constellations have been planned for some time, they have received licensed approval from the appropriate authorities and are being constructed as you read this. And there are several competing organisations, each preparing to launch in those staggeringly large numbers, an information-based environment in which demonstrations using laser-communication between satellites and specially configured F-16s are taking place now. Soon, direct communication between aircraft on opposite sides of the planet will be possible, perhaps routine if required, and that will define the sixth generation. The connecting reach will see sixthgeneration fighters flying higher and faster, perhaps using hypersonic air-breathing propulsion systems such as the Sabre engine designed and developed in the UK and now being exploited by companies both in Britain and the United States in a series of development programmes already researching hypersonic cruise weapons. These revolutionary technologies will open the possibility for a wide range of trans-atmospheric vehicles capable of operating in the thin regions of the upper atmosphere and connecting directly across several hundred square miles to coordinate air operations on a level and at a scale impossible now but feasible within 20 years. Behind it all is the fifth generation – an enabling series of radical technologies which equip front-line fighters in increasing numbers. Within 15 years the proportion of fighters with stealth, supercruise and supermanoeuvrability, operating as sensor-fusion platforms in a net-centric environment will dominate the air combat arena, paving the way for an extraordinary series of warfighters yet to emerge. FIFTH GENERATION FIGHTERS



7



SECTION 1 – CHAPTER 1



Genesis of the



Generations CHAPTER 1



ABOVE: The world’s first operational jet fighter, the Messerschmitt Me 262, entered service in July 1944 and failed to create the desired impact due to its late arrival and depleted production capacity. A superb aerodynamic design was compromised by an underpowered and unreliable engine. (DAVID BAKER)



O



n July 26, 1944 a de Havilland Mosquito from RAF Benson, Oxfordshire, was on a sortie to Munich. Its crew, Flt Lt A E Wall and Plt Off A S Lobban, approached their target at a height of 29,000ft (8840m) in relatively clear air. Suddenly, a German aircraft approached them from the rear, flying very fast. Gating the throttles, Wall believed he could outrun his pursuer and use the superior speed of the Mosquito to avoid deflection from his primary mission. Instead of falling behind, the German aircraft gained on its target and as it drew closer Wall recognised it as one of the new Messerschmitt Me 262 jet-powered fighters on which most Allied aircrew had been briefed. Wall turned to starboard to out-turn his adversary, taking advantage of the nimble Mosquito to briefly escape the jet fighter as it sped past, overshooting with a howling whine from its twin turbojet engines audible to the RAF crew. Inside the relatively spacious cockpit of the Me 262 Lt Alfred Schreiber came back four more times, completing fast fly-bys and on each one unsuccessfully bringing his guns to bear on his target, which evaded the slow-turning jet. Limited by short endurance, the Me 262 peeled away and as Wall powered the Mosquito



8



FIFTH GENERATION FIGHTERS



out of cloud, suddenly the sky was empty. Thus was the somewhat brief and inconclusive engagement of the world’s first jet fighter on another aircraft, an encounter consigned to the history books as the dawn g of jjet combat aircraft. Mistaken of a new age



in thinking he had a victory, Schreiber would go on to claim several more aircraft before he ran into a Spitfire on October 29, 1944. But the appearance of this fast jet was not unexpected and had been anticipated since Allied intelligence began to build a picture of this maturing programme several years before.



A NEW DAWN The race for speed had driven engineers and aerodynamicists to search for an effective use of reaction-engines in high-speed airframes from the late 1920s. Physical studies of gas dynamics and turbine technology in both mathematical theory and engineering practice opened the possibility of jet aircraft capable of very highspeed flight. Enthralled by talk of jet-powered combat aircraft, RAF recruits in the 1930s were wide-eyed at the thought of flying these superfast combat machines against inferior fighters. Neither was it a dream, for several countries were on the verge of demonstrating such a capability. With research into propulsion and aircraft design funded by the government, as measured by practical experiments and tests, German aircraft and engine manufacturers led the field, despite the early work carried out by Frank Whittle in Britain. Two years after beguiling his fellow flight cadets at RAF Cranwell with ideas of building a working jet engine, Whittle had registered his patent for a turbojet on January 16, 1930 and set up a private company, Power Jets, in March 1936. Paradoxically, the unwieldy bureaucracy of the German government restricted support for free enterprise and work by Heinkel and Junkers was held back by a reluctance to divert resources to a still questionable concept. Nevertheless, work did progress but not quickly enough to beat Frank Whittle, who fired up his first gas turbine engine on April 12, 1937. Nevertheless, once begun, progress in Germany was rapid, with the world’s first jet aircraft taking to the air when the He-178 made its first hop on August 24, 1939 followed by the first official flight three days later. Despite a promising start it was not Britain that became the second country to put a jet aircraft in the air, that distinction falling to the Italians when Mario De Bernardi piloted the Campini Caproni CC.2 on August 27, 1940. It was powered by a thermojet engine in which a piston engine replaces the turbine with a j It was not successful,, the conventional turbojet.



ABOVE: Italy’s Caproni Campini CC.2 was powered by a thermojet engine and while unsuccessful it is notable for being the world’s second jet aircraft to fly. (DAVID BAKER)



ABOVE: The thermojet engine adopted for the CC.2 incorporated a piston engine with a large propeller to achieve the same results as a compressor, and which is seen here on test with the aft fuselage section removed. (DAVID BAKER) basic design of the thermojet being flawed in that it progressively lost power the higher it flew. Britain was the third country to fly a jet aircraft, on April 8, 1941 when the experimental Gloster E.28/39 made a few short hops, nine days after the first flight of the Heinkel He 280 – the first aircraft specifically designed as a fighter. But that aircraft was eclipsed by the Me 262, which took to the air for the first time powered by jet engines supplemented by a nose-mounted piston engine on March 25, 1942, and as a pure jet piloted by Fritz Wendel on July 18 that year. Astonishingly, considering the dominant role they were soon to play in the evolution of first-generation jet fighters, America was a long way behind but soon caught up courtesy of a leap forward provided when US Army Air Forces’ Maj-Gen “Hap” Arnold arranged for all the drawings on the Whittle engine to be sent to the United States. It went with approval for General Electric to copy it as the GE Type 1, which made its first bench run on April 18, 1942, exactly one year after the Me 262 V1 had first taken to the air with a single piston engine. Less than five months after the bench run, Bell Aircraft was contracted to build a prototype jet fighter. For the allies, the British were still in the lead. On February 7, 1941 the Ministry of Aircraft Production had ordered 12 jet fighters and sufficient jigs and tools plus production facilities for turning out 80 aircraft of this type per month. It was initially called Thunderbolt but it would become known as the Gloster Meteor. The company had been a lowproduction manufacturer, despite having built the Grebe, the first fighter ordered for the RAF after the First World War, and the last RAF biplane fighter, the Gladiator. Before the



ABOVE: Japan’s Nakajima Kikka jet fighter was designed around the Me 262, drawings of which had been supplied by Germany for a type which came too late to see service before the war ended. (DAVID BAKER) Meteor, Gloster had built little more than 1,400 aircraft of its own design, half of which had been the Gladiator. It would soon mastermind production of almost 4000 Meteor jet fighters. When it first flew on November 13, 1943, as the world’s second axial turbojet fighter, the Meteor was in some respects superior to its German counterpart, although nobody knew that at the time. But the Meteor was 16 months behind the Me 262 and it would never see combat before the war in Europe ended on May 8, 1945. Neither would the de Havilland Vampire, Britain’s second jet fighter. Characterised by twin tail booms and a single Goblin delivering a thrust of 3100lb (13.79kN) it was marginally less powerful than the Meteor, which carried two 1700lb (15.1kN) Rolls Royce Welland I engines. Nearly 3300 would be built, an astonishing figure for post-war austerity Britain. When Lt Schreiber encountered the RAF Mosquito over Munich in July 1944 it heralded the dawn of a new age – one which would open unheralded possibilities for air combat, adopting the general principles which had matured through 30 years of experience in aerial jousting but developing tactics and warfighting very different in the detail. It presaged a new era in aircraft design and manufacturing, with new technologies forged during the Second World War, capabilities brought to the fighter that would challenge scientists and engineers in a broader field of air combat. As the war came to a conclusion in the first few months of 1945, Germany introduced a jet interceptor, the He-162 Salamander.



ABOVE: The Whittle W.1 developed by Power Jets, a company set up by Whittle to demonstrate the possibilities of an air-breathing reaction engine which, unlike the liquid rocket motor, could achieve sustained operation for lengthy periods. (DAVID BAKER) Novel and innovative, it was designed from the outset for mass production as well as for minimal servicing and maintenance. These latter qualities, so necessary in conventional manufacturing, were deemed unnecessary because damaged airframes could be written off and quickly replaced through cheap mass production. Powered by a single BMW 109-003E, it had a limiting Mach number of 0.75 but displayed high manoeuvrability and sustained high speed. Fewer than 300 were produced and it succumbed to a collapsing manufacturing base and evaporating resources. Both the Meteor and the Vampire saw operational service in Europe before the conflict ended, the Meteor being used to down V-1 flying bombs, usually by flying alongside and flicking the assailant’s wing, disrupting the controlling gyroscope and sending it earthward prematurely. America’s first jet fighter prototype, the Bell P-59 Airacomet, first flew on October 1, 1942 but failed to impress while a handful of Lockheed YP-80A Shooting Star jet fighters saw limited service in Europe but engine fires and accidents prevented engagement with the enemy.



FROM EXPANSION TO CONTRACTION



ABOVE: Gloster Meteor F.3 with Welland engines, representative of the world’s second jet fighter to enter service, operational with the RAF from July 1944 at around the same date as the Me 262. (DAVID BAKER)



For a very brief few months after the end of hostilities, Britain was the world leader in operational deployment of jet fighters. It did not last long. The first Russian jet fighters appeared in early 1946, initially using engines liberated FIFTH GENERATION FIGHTERS



9



SECTION 1 – CHAPTER 1 from Nazi Germany toward the end of the war; most notable of which was the MiG-9. Powered by a pair of RD-20 engines, essentially the BMW 003, the MiG-9 had a limited performance, was underpowered and quickly outdated by successive designs such as the MiG-15, which made its first flight in 1947 and revolutionised the capabilities of Soviet jet fighter and interceptor units with which they were equipped. The MiG-15/-17 family of jet fighters that emerged by 1950 would set in play contenders for air superiority totally unexpected in the West and their time would come quickly as tensions between political ideologies grew into direct confrontation. It was the challenge from Soviet military technology, plus the retention of a very large standing army, that frightened the West into responsive action through advanced engineering designs and new offensive and defensive systems. This would underpin successive generations of fighters and interceptors. In the West, in the wake of a devastated Europe, only the United States and Britain had credible air forces capable of matching Soviet capabilities, although their technological supremacy would be fleeting and short-lived. In the five years after the end of the Second World War, the assumption was mistakenly held that this would continue for many years. A degree of self-delusion set in as the expansion of air power during the war was followed by five years of contraction. In the three years after the Second World War US air power was drastically reduced, the naive assumption being that the quality of American design and engineering would maintain a strategic and tactical advantage over the quantity of men and material mobilised by the Soviet Union – and for a very long time. This delusion would hold sway for several decades, although dented by the detonation of a Russian atomic bomb in 1949, by the firing of the world’s first intercontinental



ABOVE: A de ABOVE d Havilland H ill d VVampire i T.11 T 11 (XJ-771) (XJ 771) from f a batch b t h off six, i one off which hi h was ddelivered li d tto th the RRoyall NNavy. Unlike U lik the th Meteor, M t the th VVampire i evolved l d into it the Venom and bequeathed the twin-tail boom arrangement to the Sea Vixen. (DAVID BAKER)



ABOVE: America’s early experiments with jet fighter concepts realised the Bell P-59 Airacomet, which took to the skies in 1942 but proved to have little potential. This particular aircraft is a prototype YP-59A. (USAF)



ABOVE: The h cockpit k off a Vampire FB Mk.2 k displaying d l a vintage layout l reminiscent off Secondd Worldld War piston-engine aircraftf withh llittlel attention to the h ergonomics of later jet aircraft of the 1950s. (IAN DUNSTER) 10



FIFTH GENERATION FIGHTERS



ABOVE: The P-59 incorporated nose armament of three 0.5-calibre machine guns and a single 37-mm cannon. Note the chin intakes for the single turbojet engine. (USAF)



ABOVE: Lockheed’s P-80A Shooting Star, the first successful US jet fighter, this particular example modified for a photo-reconnaissance role. (USAF)



before late 1954 and the re-establishment of multirole aircraft which had been forced upon allied air forces during the Second World War would not reappear for 20 years after that conflict was over. In the meantime, allied air forces would continue to acquire increasingly sophisticated technology, sometimes to the detriment of the flying skills of the pilot, in the vain search for supremacy in interception and penetration. Paradoxically, it was the Soviet Union that unwittingly provided the spur for US doctrinal planners to keep their eyes off the ball and go for all-out speed and interception rather than manoeuvrability and dogfighting. Almost as soon as the Second World War was over, political hostilities between East and West brought a need to acquire tactical and strategic intelligence on the position, strength



ABOVE: Seaborne fighters developed for the US Navy included the McDonnell F3H Demon, a prototype of which is seen here on the carrier USS Coral Sea in 1953. (USN) ballistic missile coupled to the launch of the world’s first satellite just eight years later. Rewriting many of the assumptions about air power doctrine, a scientific advisory panel in the United States urged the newly emerging Department of Defense to concentrate on speed and this led directly to a disestablishment of tactical air power in favour of strategic strike underpinned by the colossus of a mighty bomber force equipped with atomic weapons. In fact, many blamed the emerging doctrine of overwhelming and disproportionate response, fielded equally by the Truman and Eisenhower administrations, as abandoning the army which air power had done so much to support in the recent global conflict. In the mistaken belief that speed, evading concentrated air defences and single-point interception would govern future air warfare, scientific and technological development steered toward the offensive capabilities of a force of supersonic assets. Which is why the newly formed independent US Air Force in 1947 flexed its doctrinal muscles on the first supersonic flight by Charles “Chuck” Yeager in the Bell X-1 in October that year. But in basing future planning on the belief that science, technology and engineering would win the next war, the US pressed ahead with development of point interceptors. Unforgivably, that had been the mistaken belief in the 1930s. It had not been true then.



and deployment of Russian land and air forces. This was satisfied to some considerable degree by clandestine overflights using Second World War aircraft probing deep into Soviet territory over the North Pole, where Soviet defences were almost non-existent. That, in turn, prompted a major national counter response on the part of the Russians to develop, and



B h wings i folded, f ld d on an elevator l off the h carrier i USS ABOVE AAn F2H Banshee, ABOVE: Essex in 1951, a type that performed well during the Korean War. (USAF) deploy, primitive air defence systems gradually shifting from anti-aircraft artillery (AAA) to surface-to-air missile (SAM) technology. Alone, this move would outfox the Americans for more than a decade, until the experiences of the Vietnam War would once again turn fighters into mud-movers, with SAMsuppression and anti-air-defence roles grafted on to increasingly diverse capabilities for fighters and ground attack aircraft. It was a long step to take from the initial jet fighters of the immediate post-war era but the trajectory upon which this evolution would take place was sustained in large part by the employment of systems initially fielded during the Second World War. A return to swing-role employment of fixed-role interceptors and fighters that had taken place during the mid-years of the Second World War – turning aircraft such as the Spitfire and the P-47 Thunderbolt into ground attack aircraft – was slow in re-establishing the defining roles of air combat aircraft. It was, again, the eternal conflict as to whether fighters are dedicated high-speed interceptors or dogfighting combat aircraft, a role largely unchanged since 1916. Paradoxically, it was the latter which spawned the first mature first-generation US fighter, the North American F-86A Sabre. While the P-80A had fielded opportunities for learning an entirely different way in which to



JET ON JET The first US fighter capable of supersonic speed in level flight would not enter service







ABOVE: The McDonnell F3H-2N Demon poses for a PR shot during a cross-country fight in 1956. (USN) FIFTH GENERATION FIGHTERS



11



SECTION 1 – CHAPTER 1



ABOVE: An F7U-3 in flight, circa 1955, powered by two 4600lb (20.46kN) thrust Westinghouse turbojet engines, four cannon in the upper lips of the intake fairing and underwing rocket pods. (USN)



ABOVE: First of the post-war US aircraft carriers, CV-41 Midway supports the launch of a Vought F7U-1 Cutlas which was developed from captured German p g a veryy low aspect p wingg with 38-degree g sweepp and almost parallel p research work sporting chord. ((USN))



ABOVE: CConsidered ABOVE id d bby many to bbe one off the h most aesthetic h i off the h earlyl jjet fifighters, h the h Hawker H k SSea Hawk H k replaced l d the h AAttacker k when h iit enteredd service i with ih the Royal Navy in March 1953. The definitive FGA 6 was powered by a single 5200lb (23.12kN) thrust Rolls-Royce Nene engine. (DAVID BAKER) maintain, service and prepare aircraft for flight, this jet fighter would be quickly outdated – not by the enemy but by rapidly advancing technology, a lot of it acquired from the Germans at the end of the war. Some of it in the form of liberated spoils; a lot of it by active cooperation of former scientists, engineers and technicians, not least of which was manifest through the swept wing. The US Navy had a jet combat aircraft in development from the beginning of 1945, the North American FJ-1 Fury, and it was proposed that the Army Air Force valuate its suitability as a land-based fighter. Like the P-59 and the P-80, the Fury had straight wings and was firmly in the ranks of a subsonic aircraft with little more performance than the German Me 262. When the war in continental Europe ended in May 1945 a veritable treasure-trove of valuable research information became available. The Germans had been engaged in one of the most wide-ranging research programmes of modern times, investing vast amounts of money into science, technology and engineering to support the war effort and to build a significant 12



FIFTH GENERATION FIGHTERS



lead over the allies. Aeronautics, jet and rocket propulsion and the exotic science of highspeed/high-altitude aerodynamics benefited greatly from this research and this information proved invaluable in the post-war race for supremacy in weapons and military equipment. One segment of research concerned the use of swept-back wings to improve stability and airflow in the transonic regime, where compression and turbulence around the speed of sound caused problems for straightwing aircraft. The Me 262 had modest sweep of 18.5 degrees, not to improve transonic performance but to compensate for the extra weight of the turbojet engines and restore the appropriate centre of lift. There had been no attempt to apply sweep technology to the German jet although some aerodynamicists had wanted to give the type a 35-degree sweep to improve its high-speed performance. When the German results became known to US aircraft designers, a classified “secret” kept from America’s allies for some time, North American hastily applied it to the land-based



version of the Fury, designated the F-86 Sabre, despite it delaying the type by almost a year. But the results paid off, as did the opportunity to give the type a fully pressurised cockpit, a lengthened fuselage, power-boosted ailerons and automatic leading-edge slots. The type first flew on October 1, 1947, exactly two weeks before the Bell X-1 broke the sound barrier for the first time. What the Americans obtained from the Germans the Russians also had and when the MiG-15 first flew on December 30, 1947 it was similar in appearance to the F-86, except for a mid-fuselage mounted wing, also swept at 35 degrees – whereas the F-86 wing was low mounted – but with a horizontal tail on the upper section of the vertical fin carrying modest anhedral. Several competing Soviet jet fighters contested the apparent superiority of the MiG-15 but it prevailed as the fighter of choice for the Soviet Air Force. The F-86 had some technical advantages, specifically in the all-flying horizontal tail in the F-86E from 1951, which, combined with linked elevators and power boost for the tail flying surfaces, aided control in the transonic area. By 1950 tension between East and West had reached a heightened state; in early 1948 a group of Soviet operatives completed a coup in Czechoslovakia that toppled the one remaining East European democratic country into Communist control and the Berlin blockade from June 1948 to May 1949 raised the temperature on the Cold War. When the Russians detonated their atom bomb on August 29, 1949 and China was taken over by Mao Zedong’s communist forces in 1950, the age of contraction in allied military power was brought to an end. In April 1950 Soviet MiG-15s appeared over the city of Shanghai to chase away Nationalist bombers attempting to attack the city and on June 25 North Korean forces invaded South Korea with Mao’s support, quickly followed by



ABOVE: Of equal aesthetic attraction to the Hawker Sea Hawk in form and layout, the Hawker Hunter, seen here in its two-seat trainer variant, was one of the most successful post-war military aircraft produced by the UK. (TIM FELCE)



munitions and equipment provided by Russia. A United Nations resolution called on the United States and its allies to support the South, which it did, and in November the Russians started to provide the Chinese and North Koreans with MiG-15s. The stage was set for the first aerial combat involving jet fighters. On November 1 a group of eight MiG-15s attacked 15 US Air Force Mustangs, one of which, piloted by Aaron Abercrombie, was shot down. In another engagement, three MiG-15s attacked 10 F-80s (a nomenclature change had redesignated the P-80) and in the first jet-onjet engagement 1st Lt Semyon Fyodorovich Khominich shot down an F-80C piloted by Frank Van Sickle. On November 9, the first MiG-15 loss



ABOVE: A Sea Vixen of 899 Sqn (XN694) refuels another (XJ571) from the same unit at a Farnborough Air Show event during the 1960s. (ARPINGSTONE)



ABOVE: Wings folded, a Sea Vixen from 890 Sqn, a type which entered service with the Royal Navy in July 1959 and which was successfully adopted as the service’s standard all-weather fighter. (DAVID BAKER) was credited to Lt Cmdr William T Amen flying a Grumman F9F Panther, a straight-wing jet fighter operating off the carrier USS Philippine Sea.



ABOVE: An English Electric Lightning F.1A at Yeovilton, the UK’s first Mach 2 fighter with a phenomenal climb rate mandated for its role as an interceptor. (DAVID BAKER)



THE SECOND GENERATION



support operations seconded to the Royal Australian Air Force and a range of other types were employed on support operations. The complement of first-generation jet fighters operationally deployed in the Korean War was mixed with significant numbers of aircraft left over from the Second World War, the US Air Force having more than 1100 F-47 and F-51 (formerly P-47 and P-51, respectively) piston-engine fighters in the mix and a significant number of F-80s were deployed. But the transition was rapid and the obsession with single-point interception was challenged



Lessons were hard won during the Korean War, each side making extravagant claims for combat kills, victory scores which have since been levelled through scrutiny and disclosure. When the ceasefire took effect from July 27, 1953 both sides had achieved much, in experience and application of revised combat techniques from four years of sustained hostilities. The MiG-15 and the F-86 were only part of the total force inventory. When the war began the dominant fighter type in service was the Republic F-84 Thunderjet, the total inventory being 962 versus 423 F-86s. By the end of the conflict the latter outnumbered the former by three to one with a total of more than 3700 Sabres in service. However, albeit with a thinner and more highly swept wing and a more powerful turbojet engine, the improved MiG-17 appeared only a few months before the ceasefire and made only a minor contribution. But when it came to the battle record, logs differ as to who came out on top. The US Air Force claimed more than 900 aerial victories of which 792 were assigned to the F-86 for the loss of only 78 Sabres. But after decades of scrutiny and checking of combat records and unit histories, it is generally agreed that US fighters shot down 379 aircraft for the loss of 224 F-86s. But even these are approximations as some losses were not attributable to combat. The RAF was not directly involved in the conflict, in that no squadrons were based in South Korea, but several pilots served with the USAF on exchange and accounted for seven kills, flying F-86 and F-84 Thunderjets. Other RAF pilots flew Meteors on ground



by the experiences of the Korean War. Increasingly, air superiority was becoming a vital precursor to ground operations. Even absenting the direct role of ground support, clearing the air over the battle area was a vital part of preparing an attack or covering a repositioning deployment. By 1954 the legendary Hawker Hunter was becoming available, with deliveries first to No 43 Squadron at RAF Leuchars. Too late to see action in Korea, this ubiquitous aircraft, called upon to fill many roles, would remain as the UK’s standard single-seat fighter until 1960, when it was succeeded by the English Electric Lightning. The Americans, paying just attention to the needs of their carrier forces, deployed the McDonnell F2H Banshee, the McDonnell F3H Demon and the Vought F7U Cutlass. For its part, the Royal Navy began to receive the de Havilland Sea Vampire in 1949, succeeded by the Sea Venom four years later (both developments of the Vampire/Venom series developed for the RAF) before the Sea Vixen entered service in 1959. As qualified in the introduction, the lines of demarcation between generations of fighters are at best arbitrary and subject to debate and disagreement as to the criteria for deciding what constitutes a second-generation fighter. But the general principles that marked first-generation types are subsonic top speed, primarily a gun







ABOVE: Lightning interceptors of No 56 Sqn at RAF Akrotiri, Cyprus, during armament practice with Firestreak missiles in 1963. (RAF) FIFTH GENERATION FIGHTERS



13



SECTION 1 – CHAPTER 1



ABOVE: The MiG-21 represented the definitive progression from the MiG-15 through the -17 and -19 series and remains one of the most extensively exportedd aircraft in history with several still serving and many examples retained by private owners. (DAVID BAKER) armament and with modified controllability in the transonic zone. Their airframes were essentially unmodified in general engineering terms from those designed for piston-engine types and very few lacked any ability to use sensors for detecting enemy aircraft. The experience of the Korean War and the rapid development of air defences forced the design of small radar sets for onboard detection of enemy aircraft operating beyond visual range (BVR) and pushed the introduction of the air-to-air missile (AAM) as a combined system for defence. Passive infrared homing missiles became common during the second general phase and this capability, while limited, afforded a minimal, but significant, form of tail defence. Radar guided missiles were a characteristic of the new fighter generation and semi-active radar homing missiles (SARH) began to appear. Radar gunsights became standard and these were integrated with greater lethality through enhanced gun technology. First-generation types carried armament largely adopted from late Second World War equipment. Considerable attention was paid to delivering a viable, and reliable, BVR capability but in that regard the second-generation types were really only part of a development curve that would be fully realised with third-generation fighters. Condemned to support the concept of high-speed interception, second-generation aircraft are most notably identified as types capable of supersonic level flight and for this a wide range of aerodynamic features were introduced, including area-rule fuselage contouring to improve transonic and supersonic



drag characteristics. Afterburners, or re-heat, became standard with increasingly powerful powerplants while engine performance expanded the flight envelope and radius of action. Finessed aerodynamic design helped improve manoeuvrability and powered turn capability and weapons delivery encompassed both conventional and nuclear stores. To many, the US Century-series fighters epitomise the second-generation type, a category defined by the numerical system of type identification beginning with the North American F-100 Super Sabre, first flown on October 29, 1953. The world’s first jet fighter capable of supersonic speed in level flight, the F-100 was an evolution of the F-86, which had been informally named by the company as the Sabre 45 – on account of the 45-degree wing sweep angle. With an oval-shaped lip intake and a slab tail, the type entered service in 1954 and would remain so for 34 years. Others in the series quickly followed during the 1950s, including the F-101 Voodoo and the delta-wing F-102, in service from 1956 as the first US fighter designed purely as a missile carrier and carrying a pinched-in mid-fuselage profile introducing Richard Whitcomb’s “area-rule” concept for minimising drag. This was followed by the F-105 Thunderchief in 1958 and the F-106 in 1959. Specialised types too flourished during this period, with the Northrop F-5 Freedom Fighter emerging as an international lightweight fighter specifically designed for foreign markets. Arguably the most outstanding secondgeneration fighter of its day, the Mach 2 English Electric Lightning was a leap forward



ABOVE: A Fiat G.91R of the German Air Force, developed as a lightweight fighter to a NATO specification of which more than 750 were built. It also served in the Italian and Portuguese air forces with the type remaining in operation for 35 years. (DAVID BAKER) 14



FIFTH GENERATION FIGHTERS



The SSaabb 35 DDraken k was established bli h d as a fifirmlyl second-generation d i ABOVE Th ABOVE: jet fighter which made its first flight in 1955 and entered service five years later. More than 600 were built, this example being the SK 35C. (KATSUHIKO TOKUNAGA) for the British aircraft industry. With a thin wing of 60-degree sweep and two engines in an over-under installation, the Lightning was a point-defence interceptor originally conceived as an air defence system for British V-bomber bases and was in service from December 1959, the first British aircraft to achieve Mach 2. Although designed to engage and bring down enemy bombers at a distance, leaving those few that got through to airfield defences such as the Bloodhound SAM batteries, the Lightning had twin guns in addition to two AAMs. Meanwhile, in 1959 Russia’s MiG-21 entered service with a pirated copy of the American Sidewinder AAM, an intact example having been extracted from the tailpipe of a MiG-15 after it failed to explode following an encounter with a Taiwanese F-86! Known as the AA-2 Atoll, the missile gave the MiG-21 credibility and the types became one of the longest-surviving examples of a second-generation fighter. Numerous other examples of this generation proliferated in the burgeoning inventories of jet fighters – many modified, upgraded or improved on the lessons of the Korean War, largely a first-generation fighter conflict. France produced the Super Mystere, the Etendard IV and the Mirage III and 5 series, Italy launched the G.91 as an all-NATO fighter and Sweden fielded its delta-wing Saab 35 Draken. The development of first and secondgeneration jet fighters had been fast and robust, with battle experience from the Korean War providing a valuable stimulus to identifying requirements for the next generation, when developments were to take a significant leap forward.



ABOVE TTwo Mirage ABOVE: Mi III fifighters ht with ith the th RRoyall AAustralian t li AiAir Force, F second-d generation fighters with considerable export success. These two were sold to Pakistan. (RAAF)



SECTION 1 – CHAPTER 2



Generation CHAPTER 2



I



t is an axiom of cynics that soldiers are doomed to fight the next war with weapons from the last one. It was so with the Korean War, which broke out less than five years after the end of the Second World War, where the majority of the aircraft deployed were from that global conflict. Most of the jet-powered fighters deployed to the Korean conflict were designed during the closing year or two of that war and lessons learned played out into the murky and subjective divisions between first and second-generation fighters. Notwithstanding the importance of improved technology and a completely new war-fighting capability, examination of the kind of lessons learned from that conflict make sombre reading. Right after the war ended in Europe, the US government was pitched into a radical restructuring of national defence policy. The unification of the army and the navy into a Department of Defense (DoD) had been the logical conclusion of a detailed examination of how best to mobilise national resources for a major war. The formation of the DoD and the convergence of these separate services into an integrated unit, responsible for managing and operating military forces, had been placed on hold until the conflict in the Pacific was concluded with the surrender of Japan. Formally signed on September 2, 1945 the cessation of hostilities came almost exactly six years after Germany attacked Poland in 1939. In that time, air power went from a wide range of aircraft still sporting open cockpits, fixed landing gear and piston-engines, to closed cockpits, retractable landing gear and jet engines doubling speeds



A B-29 from the 307th BG drops a heavy load over a target in Korea during 1951. At this early stage in the Korean War the Air Force still held to a bombers-first procurement policy. (USAF)



from North Korea and its paymasters China and Russia. In planning for the next generation of combat aircraft, an age of fast jets and highperformance aircraft, few lessons, it seems, were applied from the Korean conflict.



AN ECLECTIC MIX Paradoxically, initially the most soughtafter aircraft in the Korean War was the F-51 Mustang – but only because there was a job it could do which was beyond the capabilities of the new jet fighters deployed. Its ability to operate out of shorter airstrips and fly for greater distances meant the piston-types were more flexible in responding to rapidly changing needs. Moreover, with longer range they were capable of extended loiter time in the battle zone waiting to respond to enemy movements and a sudden call to action. On paper, the jets were supreme, and so



ABOVE: Commander-in-Chief of the US Far East Asia Air Force, General George E Stratemeyer presided over a turning-point in elevating the importance of jet fighters. (USAF) and pushing aircraft into the transonic regime. Add a further six years to the end of the Korean War and speeds had doubled again with aircraft designed for a wide range of new technologies not even invented 12 years earlier. Yet despite the pressure to build faster interceptors and to plan for a push-button war where missiles replaced guns, to place emphasis on a massive nuclear response to aggression and to minimise the requirement for dogfighting capabilities, it was with Second World War-era weapons that the allies fought back aggression



ABOVE: The carrier USS Boxer loaded with F-51 Mustang fighters at Naval Air Station Alameda in June 1950, embarking for a war that would transform the fighter forces of the US Air Force. (USAF) FIFTH GENERATION FIGHTERS



15







SECTION 1 – CHAPTER 2



51D off NNo 2 Sqn S South S th Af African i Air Ai FForce, partt off the th allied lli d ABOVE: FF-51Ds ABOVE contingent responding to a call from the United Nations to evict the North Korean invaders, May 1, 1951, many with ex-Second World War types. (USAF)



ABOVE: An F-51 encounters unfamiliar weather in support of the Korean War but unlike early jets it was able to operate off short and very rough airstrips. (USAF) they were in the numbers deployed. But the flexibility and operational support provided by the Mustangs forced a rethink over exactly what role the jets would play in a future, perhaps more regional, conflict. Most operations carried out by the F-51 supported army units and for a while these were the only aircraft operating off the peninsula itself. Troubled by the need for long runways, the first-generation jets lacked the flexibility and response time for close air support (CAS) which, to many pilots and senior officers in the fighter echelons of the new United States Air Force, was anathema to their purpose. As a side note, even the optimum deployment of the B-29 heavy bombers was at first in an exclusive Close Air Support (CAS) and interdiction role. The bombers were employed attacking trucks, tanks, arsenals and supply dumps, operating in a purely tactical role but even when turning to a strategic assignment they were so effective that they quickly ran out of targets. But this worked against the optimum use of air power, which for 20 years had stressed the primacy of a strategic bombing doctrine, a policy that had resulted in the employment of the B-17 and B-24 during the Second World War. What has this to do with the evolving shift in jet fighter generations? Peripherally, quite a lot. Inflexible due to shorter range and minimal loiter time, the F-80 Shooting Star was given greater range through the use of 265-gallon (1000-litre) Misawa drop tanks. Much improved over the smaller wing-tip tanks, the Misawa type had been invented by Lt Robert Eckman and this conferred a combat radius of 350 miles (563km). During the first six weeks of combat, the F-80s flew 70% of all combat sorties and accounted for 85% of all enemy losses to aircraft. Gen Stratemeyer said: “I wouldn’t trade the F-80 for all the F-47s and F-51s you could get me.” But this euphoria was short-lived and would soon give way to reality checks. Initially, the only available airfield on the Korean peninsula was Taegu, which was a dirt and gravel strip incapable of supporting the F-80. The range the aircraft had to fly to get to combat allowed only 15 minutes over the target, extended to 45 minutes with 16



FIFTH GENERATION FIGHTERS



the Misawa tanks. But the type was a hard “sell” in the conflict. Compared to the three hours of loiter time for an F-51, this was still poor. Ill-suited to the local conditions, the five Wings equipped with the F-80 quickly reverted to the Mustang but some fighter-bomber units harboured devotees who switched units to keep flying the Shooting Star! The jet certainly impressed the locals, being used at first to cover the evacuation of civilians, but the ability of the F-51 to fly off dirt strips, in-country, forced a return to piston-power for a while. But new requirements forced a niche for the F-80 with the introduction of a reconnaissance role. But even that had its compromise, the type



being completely outclassed by the MiG-15 and unable to survive attack unless operating under the umbrella of F-86s flying top-cover, especially in “MiG alley” – the name given to a MiG-infested zone in the north-east of North Korea close to the Chinese border. With each passing week developments and shifting tactical requirements were feeding back information to the “number-crunchers” in the Pentagon analysing the balance of technical capabilities between friend and foe, between the expectations of the planners and the realities of field commanders, and between the technical developments tumbling out of research laboratories and aircraft companies keen to apply engineering and design breakthroughs and innovative design improvements to existing types. Several technical developments improved the performance of aircraft operating in theatre, not least with the F-86F introduced in June



ABOVE: Taken from a concept tried out by the Luftwaffe in the Second World War, an F-80 equipped with Schräge Musik mountings for upward firing cannon at an angle which would allow attack from below and behind. (USAF)



ABOVE: The parlous state of North Korea’s air forces is epitomised by the Ilyushin Il-10, an example of which is seen here at Kimpo in 1950. (USAF)



LESSONS LEARNED



ABOVE: Th ABOVE The YYakovlev k l Yak-3, Y k 3 one off severall types supplied li d by b RRussiai andd operatedd by b the h North N h Koreans K which hi h were easy pickings i ki for f the h F-51 F 51 andd the h limited li i d numbers of F-80s initially deployed in theatre. (OREN ROZEN)



Some of the experiences of pilots and aircrew in Korean War combat drew on what the enemy was doing and how the balance between aircraft and airman could be picked out. By the end of 1951 the initial tranche of Soviet pilots drawn from their most experienced ranks, blooded in the Second World War and some of them “aces”, were taken out of theatre and replaced by fresher and younger pilots who were experienced in handling the firstgeneration jets but without combat skills. This skewed the performance results against the MiGs for the duration of the second half of that war because the American pilots who had gathered experience during engagements with the best of the Soviet pilots applied those newly acquired skills in air combat. The statistical balance of MiG against Sabre is highly prejudiced by the period in which the statistics are quoted. Moreover, the exacting scrutiny regarding which aircraft was the best in air combat generally failed to add in the pilot’s training and experience. Second World War veteran and first through the sound barrier in level flight, Charles “Chuck” Yeager flew both an F-86 and a captured MiG-15 where he prevailed in whichever aircraft he was flying. To Yeager it was “the man” rather than “the machine” and this lesson was taken to heart by the Americans when they examined how critical that could be in combat. The Russian base at Antung was a communist training school where pilots went through six weeks’ training before taking to the air at high altitude while the instructors engaged the enemy to show the students how it was done. In combat the students remained out of



1952. This variant introduced the famous “6-3” wing, whereby the leading edge slats were removed and a new solid leading edge incorporated with 6in (15.24cm) additional root chord and a 3in (7.62cm) tip extension. To direct airflow across the wing, a 5in (12.7cm) boundary layer fence was added at 70% of the span, changes which resulted in reduced drag coefficient and put 7mph (11km/hr) on the top speed. But these improvements extended across the entire performance spectrum. By delaying the onset of buffeting, manoeuvrability was enhanced allowing it to turn inside the MiG-15, providing a new top speed of 695mph (1118km/hr), the climb rate increased by 300ft/min (91m/sec) and operating altitude raised to 48,000ft (14,630m). All of which also enhanced the handling characteristics, further offsetting the onset of a spin, from which it would benignly recover on centring the controls. Moreover, with an upgraded engine, the type could climb as high as the MiG-15 and almost as quickly. But there was more to effectively operating the F-86 than sheer performance. Logistical supply routes from the United States to Japan, from where initial operations took place, could support fewer Wings than were deployed and by February 1952 almost



half of all F-86s were temporarily grounded due to a temporary shortage of spares and fuel. The Korean War provided a fast learning curve regarding the operation of jet aircraft in-theatre, completely different logistical and operational considerations to standard practice for piston-engine fighters. But for all associated logistical problems, the F-86 proved to be the one aircraft that would counter the threat of overwhelming communist superiority. For the first several months of the conflict, the F-86 was more than a match for the YAK-3, YAK-7 and Il-10 aircraft put up by the North Koreans. On November 1, 1950 the first Russian MiG-15s arrived and the battle for air superiority began in earnest. Within seven months the communists had 445 MiG-15s in theatre to 89 USAF F-86s and big air battles began as formations of up to 90 and more enemy aircraft engaged allied aircraft. On October 23, 1951 a force of about 100 MiG-5s engaged 34 F-86s, 55 F-84s and eight B-29s. Not untypical, these air battles provided a unique opportunity for intensive postengagement analysis, which fed directly into the evaluation of what would be required for the next sequential steps in fighter evolution.



ABOVE: The US Air Force had been preparing for a war involving large bombing forces against great-power states and found itself playing international policeman against a rogue state, using ageing B-26 medium bombers in this case against targets at Wonsan. (USAF)



ABOVE: The Russians supplied new MiG-15s to the North Koreans and surprised the allies with more effective firepower than the F-86s, introduced to the conflict at the same time. (DAVID BAKER) FIFTH GENERATION FIGHTERS



17







SECTION 1 – CHAPTER 2



Despite a reward of $100,000 offered for the first pilot to defect with a complete MiG-15, none were delivered until No Kum-Sok landed at Kimpo Air Base near Seoul with this pristine example after the ceasefire. (USAF)



the action while the experienced pilots suffered the highest losses. In contrast, US Air Force pilots flew F-86s for 18 months before deployment to Korea. Many of these pilots were Second World War veterans and had gone through rigorous training at Las Vegas Air Force Base (now Nellis). While the aircraft were close to being equally matched, apart from differences as each jockeyed for superiority through continuous modification and improvement, 18



FIFTH GENERATION FIGHTERS



it was the training and the way the pilots prepared for combat that made the difference. The Russians had a highly organised method of fighter control, aspects of which when studied later by the Americans provided structure regarding what was required in advanced fighter aircraft of the day. Good and highly effective ground control would vector the MiGs on to their targets from where they would operate autonomously in pairs. Squadrons operated in



six-ship groups divided into these three pairs. The first pair would attack while the second pair protected the first and the third remained above, being afforded a panoramic view of the air-battle space. Because the Americans operated in pairs – with a single attacker and his wingman – if either was shot down it would leave a remaining aircraft vulnerable to attack, or to be available to intercede with the pair of Russian attackers. The third Soviet pair would swoop down to take out the loner and in this way the Russians gained a tactical advantage over the Americans. The Korean War showed, in a way the Second World War never could, how blurred could be the lines between tactical and strategic conflict, and how fighters and bombers would have to adapt equipment built for one application into the needs of another quite different application. For example, when the Chinese started building forward air bases to afford MiG pilots longer time over their target, B-29s would destroy those bases while protected by F-86 fighters. Moreover, as the allied forces pushed the invaders farther to the north of North Korea they were able to build fighter bases to achieve what the Chinese communists had failed to accomplish to the south. An intermediate type, the F-84E Thunderjet had been the first variant to arrive in Korea and was used to escort B-29 bombers and to operate with the F-86D. But it had been an inauspicious start; poorly protected from corrosive salt spray on the open decks of ships at sea, half those arriving had significant structural damage. However, with a single 230-gallon (870-litre) drop tank under each inner wing mounting, the aircraft quickly found its niche as a fighter-bomber. Some spectacular attacks were carried out against bridges and dams with concentrated mass attacks involving up to 60 Thunderjets. This transitioning role fed back into the expanding inventory of stores the type was cleared to carry for ground attack. Within a few months of the outbreak of the Korean War, the F-84G became the first fighter aircraft anywhere in the world to carry tactical nuclear weapons and operational deployment to Europe started in 1951. The following year, the low-altitude bombing system (LABS) was adopted, clearing the aircraft to lob tactical nuclear bombs safely from low altitude. Proving flights for long-range deployment was also used to expand the first and second-generation fighter jets. The F-84G was used to demonstrate long-range deployment when an aircraft from the 31st Fighter Escort Wing deployed from Turner AFB, Georgia, to the Far East, refuelling twice en route from KB-29P tankers. Although the F-84 was 40mph (64km/hr) faster than the F-80, it was inferior to the F-86 but served well as an interim type and was far less vulnerable to MiG attack than the Shooting Star had been. Quick to accelerate at low altitude, it was down on the deck that the Thunderjet found its true location, the aircraft capable of absorbing a lot of battle damage and proving itself more of a mud-mover than a tactical fighter, but with a high survivability rate nevertheless. The F-84E was equipped with a radar gunsight and better wing-tip tanks with a lengthened fuselage for better comfort in the cockpit, improvements that underpinned a rapid escalation in upgrades and improvements as the budget available for procurement



ABOVE: MiG-15s curving in to attack B-29s over Korea in 1951. (USAF)



ABOVE: The rapid development of the F-86 was based around a series of technical developments and operational needs provided by pilots gaining experience in jet-on-jet warfaree in the Korean War. The aircraft itself was an evolution from the US Navy FJ1 Fury. (NOORTH AMERICCAN))



the Vietnam War that followed, an achievement both under-reported and frequently forgotten. Initially, the F3D Skyknight had a more effective suite of radar than the F-94 Starfire, a development of the F-80 into a two-seat, all-weather, radar-equipped fighter which was fully operational from 1950. It was sent to the Korean theatre to fill an embarrassing void in night fighters. Subsonic and with a range of 239 miles (385km), the F-94 was gradually improved over the duration of the war and became the single best night fighter in the world by 1953. With advanced AN/ APQ-33 radar sets, they were prohibited from flying over enemy territory for fear the equipment would fall into the wrong hands.



and engineering evolution rapidly increased. The austere days of the immediate postwar years were over and the Air Force worked hard to import changes recommended by contractors – eager for additional contracts – previously left unexploited through lack of funds. The new evolutions of technical innovation introduced specific role-adapted upgrades, some with spectacular success. One example of that was the Navy’s Douglas F3D Skyknight, developed as an all-weather jet fighter, which entered service a year before the Korean War broke out. Robust, powered by two 3400lb (15.1kN) thrust Westinghouse J34 engines, it had a top speed of 600mph (965km/hr) and carried a crew of two in side-by-side seating. By 1952 the Skyknight was a state-of-the-art combat aircraft and had three radar sets: an AN/ APG-26 to lock on the 20-mm cannon, which was effective to a range of 12,000ft (3600m); an AN/APS-21 search radar to scan the forward quadrant 90 degrees either side of the nose to a range of 15 miles (24km); and a AN/APS-28 tailwarning radar scanning a 144-degree cone from 450ft (137m) to a range of four miles (6.4km).



The Skyknight achieved its first kill on November 2, 1952 when a MiG-15 was shot down in the first recorded success of a jet-onjet night interception. The Skyknight would achieve more air victories, and destroy more enemy aircraft, than any other type operated by the Navy and the Marine Corps. Never given the credit it deserves, the type played an important role in the Cuban Missile Crisis and in



ABOVE: A potent ABOVE t t exponentt off night i ht attack, tt k DDouglas l F3D Sk Skyknights k i ht off VMFN-513 at Kunsan in 1953 toward the end of the Korean War. (USN)



ABOVE: AB Republic F-84 Thunderjets of the 14th FW. The type evolved into nuclear strike and photo-reconnaissance variants pointing the way toward truly multirole types. (USAF)



A CHANGE OF DIRECTION Before the Korean War the predominant strategic bombing doctrine that held sway from the last full year of the Second World War was made critically suspect by the new conflict. Where



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ABOVE: Filling the photo-reconnaissance requirement, the RF-84F Thunderflash played an important role in gathering intelligence for tactical and strategic operations, another adaptation of a day fighter. (USAF) nuclear weapons had been thought to complete the concept of massive strategic retaliation, relied upon as a force-leverage in an environment of shrinking defence budgets, the Korean War showed how effective the heavy bomber could be in providing a tactical, ground support role in addition to its strategic operations. It also showed that development of strategic bombers (such as, perhaps, the massive but slow B-36 and the faster B-47 and B-52 types) must not preclude the need for medium and light bombing capability. And arguing against a purist defence of fast interceptors and air-defence fighters, Korea showed that multirole aircraft down at the lower and lighter level of aircraft were just as important. In short, the Korean War redirected attention toward a much more even split between fighters and bombers. Air superiority had shown the way in which ground operations, even strategic warfare, could eclipse limitations on quantity and performance with combined operations involving bombers in a support role. Witness the value B-29s had in destroying Chinese forward bases which denied them the challenge to US air superiority; had those bases not been destroyed, the air fight could have swung in favour of communist forces. Add too, the fact that when the MiG15 showed up at the end of 1950 it tipped the scales toward a superiority only denied because of the simultaneous arrival of the F-86. When the war began most US fighters were only marginally superior to the enemy aircraft and the jets were insufficient in number to pull a distinct advantage without the appearance of the F-86. The allies also learned that they could



be faced with a combination of regional conflict and an intercontinental war. Of the 137 USAF combat wings in 1953 only 17 were deployed to Korea, the remainder held back, in part for fear that the war was a feint to decoy forces away from Europe or the defence of the US. The official report into the air operations during the Korean War would play a significant role in shaping requirements put out to industry for the next generation of fighters – as well as other aircraft, including a pressing and urgent need for aerial refuelling tankers for ferrying combat aircraft to dispersed war zones. Through these findings, the Department of Defense began to restructure how it saw air power contributing to victory in any future conflict. It concluded that: “In a war with a major power the aerial superiority… so easily attained in Korea would be dearly purchased at a heavy cost of airmen, aircraft and an all-consuming war effort.” Clearly, the Air Force was not going to give up on its drive toward ever-faster aircraft. Nor did it totally abandon the idea that dogfighting was a Second World War construct outdated by supersonic flight and prolific availability of



ABOVE: An F-84E plays the ground attack role using rockets against enemy targets in support of ground operations. (USAF)



long-range AAMs. But added to those demands for future fighter types was the self-evident value in multirole aircraft capable of long-range operation through the use of drop tanks and copious stores points for ground attack, close air support and a variety of specialised missions – not least the delivery of tactical nuclear weapons, planning for which had already seen F-84 Thunderjets deployed to the UK and to selected continental European air bases. The impact on the Department of Defense was to change the military policy of the United States and that would drive the kind of aircraft the Air Force sought. It was believed that the combined objective of the Soviet and Chinese communist governments was to test the West through brush-fire aggression, probing the opportunity to use any small-scale conflict as an escalator to general war. This was the sown seed of the “domino” principle that would become the prevailing doctrine of Robert McNamara when he became Secretary of Defense in 1961. Coupled to concerns about Soviet aspirations regarding its willingness to engage in a war involving nuclear weapons, the United States began a period of military expansion that would influence the decisions made by the new occupant in the White House, who had pledged to end the Korean War – Dwight D Eisenhower. When the war began in 1950 the US Air Force was struggling to maintain 42 effective air Wings with 400,000 personnel. Within two years those plans had escalated to a planned 95 Wings and a million personnel. By mid-1953 the plan was to grow the Air Force to 143 Wings and 1.2 million men and women in arms and when the armistice was signed those numbers had already reached 106 active Wings, of which 93 were fully operational. The overall changes that were brought about by the Korean War galvanised the aviation industry and vitalised the fighter sector, spurring on manufacturers who could take greater risks with investing their own resources into proposals that now had a greater chance of being accepted. Added to which, there was greater feedback through the various research and development organisations that were providing advanced technical input for radical concepts as well as subtle improvements. The rapidly evolving capabilities of the F-86 are an exemplar in this story of how designs spawned successive variants based on operational experience to achieve significant steps forward with existing aircraft. The transformation in equipment during the three years of the Korean War was



ABOVE: Anothher devellopment from an existing airfframe, thhe Lockkheedd F-94B benefited from the development of the F-80 into the two-seat T-33 trainer and evolved into this two-seat, all-weather fighter. (USAF) 20



FIFTH GENERATION FIGHTERS



unprecedented. The old F-80s and the F-51s had been replaced even before the end and the supersonic F-100 was replacing the F-86, while the swept-wing Republic F-84F Thunderstreak was replacing the straight wing “G” variant. Previously, the F-84F had been held back by limited funds for new aircraft and thus appeared in service out of alphabetical sequence. With renewed interest and extra money, the Air Force invested in the type and it entered service in January 1953, the more familiar RF-84F reconnaissance version following along. The purists seeking sleek and uncluttered aero-surfaces for light and feisty performance were taking a beating. Fighters were having to take on added roles, which meant additional stores and that significantly affected their performance. Manufacturers provided figures based on “clean” aircraft devoid of stores, drop tanks or other appendages which drastically reduced performance. Fighters were still being designed for a “clean” wetted area and real-world performance figures of aircraft with added stores and heavy ordnance were closely guarded secrets. Even to the extent that figures published by erudite, open-source industry literature failed to reflect the damage that multirole applications did to manufacturers’ claims. Many books still use figures published by various editions of Jane’s All the World’s Aircraft, which merely repeated the sales claims from manufacturers. Pilots knew different. Another application where the Korean War changed doctrinal viewpoints emerged with the carrier task forces, which since the end of the Second World War had been at the sharp end of a political battle over the primacy of sea or air forces in a future conflict. Independent since September 18, 1947, the Air Force had won the fight for that role where the carrier forces were increasingly seen as obsolete. A surprising conclusion perhaps, given the primary role they, and associated naval air power, had secured in the defeat of Japan. Perhaps not so surprising after atomic weapons tests showed the devastating effect even a relatively small



ABOVE: The definitive embodiment of an evolving capability brought about by improved engine performance and greater understanding of transonic aerodynamics, the supersonic F-100D seen here over Rogers Dry Lake, California. (USAF)



ABOVE: An F-84E plays the ground attack role using rockets against enemy targets in support of ground operations. (USAF) nuclear bomb would have on a fleet of ships. During a so-called “revolt of the admirals”, in 1949 the Air Force had won a battle with the Navy in getting funds for the hemispheric Convair B-36 bomber over a super-carrier. Unable to afford both, the government cancelled the carrier and gave the heavy nuclear strike role to the Air Force, backing the B-36. However, the Korean War demonstrated the proven ability of naval aircraft operating off carriers to strike farther up toward the Chinese border



than land-based aircraft, a capability which regained for the Navy the eminent position it had fought for, and temporarily lost, after the Second World War. This served as a stimulus for naval aviation and provided the spur for development of third-generation fighters. The resurgence in naval air power was too late for the existing generation of carrierbased fighters, which retained straight wings for low-speed handling but would soon adopt the swept wing out of necessity, recognising that supersonic performance and slow landing speeds were not incompatible. After Korea, the Navy never fielded a straight-wing fighter again. For land-based fighters, the recognition that jets needed more potent armament was delivered with force when MiG-15 cannon proved more effective than the guns carried by the F-86 – but this was only one of the many improvements which were required, and made possible with third-generation fighters that emerged after the Korean War.



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21



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T



he demarcation between the second and third-generation fighters is defined by the shift toward greater manoeuvrability, refined aerodynamic design, complex integrated engineering solutions, much improved engines and more sophisticated stores and weapons. Third-generation fighters emerged in the early 1960s and were replaced by fourth-generation types around the late 1970s and early 1980s. But again, this is subjective and dependent upon the precise criteria used to measure the boundary. And where precise and clear boundaries between generations are sought, there are as many subjective opinions as there are commentators. Here, we will consider the boundary where the first and second-generation types gave way to the third and fourth-generation fighters. The major shift which defined the transformation came from a radical new way of designing aircraft and integrating the various systems, subsystems and sensors. Arguably the most dramatic external change came with the shift to an integrated engine and airframe assembly, where the total aircraft was part of the general design process through to signed-off drawings. Previously, in first and second-generation types, while the overall configuration was set when the general design was complete, separate elements of the design were handed over to draughtsmen who set about the job of focusing on their own dedicated elements, be it wing, fuselage, tail, landing gear or cockpit. This approach tended to invite compromise and, as discussed later, the McDonnell F-4 Phantom II is an excellent example of that 22



FIFTH GENERATION FIGHTERS



internal or external stores and with low fuel loads misleadingly presents the aircraft in an unrealistic configuration and loading. As airshows demonstrate, the dramatic takeoff performance, manoeuvrability and agility displayed by test pilots wows crowds and can (sometimes frighteningly!) influence politicians when lobbied for support by over-zealous sales teams. But that is a different story! ABOVE: The Miles M.52, designed for research into transonic and supersonic flight with an annular engine inlet and a conformal cockpit canopy to smooth the airflow over the forward fuselage. (M L WATTS) flawed approach. That changed when integrated aero-design and engineering solutions retained separate elements – the entire aircraft being developed rather than separate elements brought together on the production line. Third-generation fighters displayed a gradual shift more closely aligned with defined mission requirements for the particular type of combat aircraft involved, producing a design which could maximise the set of sensors, avionics, radar and weapons systems as a collective and integrated “system” of its own. Instead of designing an airframe upon which to hang an increasingly complex suite of systems and subsystems, this evolution effectively returned the aircraft to its original purpose as a weapons platform and let the technology drive the capability. It is very easy to see aircraft defined in their success by outright performance and the tendency to demonstrate aircraft in a “clean” configuration devoid of external tanks,



TRANSFORMATIONS As we have seen earlier, speed was sought along with a general performance increase in early jet fighters to minimise the flight time to a designated target and to achieve a superior engagement condition. Aeronautical design engineers first encountered supersonic speeds when they worked to limit the speed of a propeller tip, below Mach 1, seeking in the jetpropelled fighter a means of breaking through that (falsely named) “barrier” by pushing the entire aircraft through the transonic region. Apart from avoiding the propeller tip speed problem simply by eliminating the propeller, thereby opening up an unlimited access to supersonic flight, another promise of the jet fighter was the greater efficiency from the significantly lower weight per unit power number compared to a propeller-driven aircraft. Development of appropriate airframes for the performance sought by the Air Force required a considerable change in mindset from the way aircraft had been designed up to 1945 and the configuration they would need to have to achieve those ambitious objectives. Maturation



place between the British and the Americans, as the world slid remorselessly into the Cold War.



INS AND OUTS



ABOVE : The rocket-powered Bell X-1, first through the sound barrier in October 1947 – flown by Chuck Yeager heralding the supersonic era but with an aircraft that was carried into the air by a carrier-plane. (DAVID BAKER)



ABOVE: The Whittle W2/700, designed in 1944 for the Miles M.52 and incorporating reheat to boost thrust, could take off from the ground and land under its own power. (DAVID BAKER) of the aerodynamic refinements that would characterise the second-generation jets was brought about by extensive research, and by copying existing work conducted by Germany during the war. But it required innovative thinking to create test shapes of wings and fuselages that would allow safe flight through the transonic barrier (Mach 0.095-1.05) and on into truly supersonic flight. It would not come through the design trends that had characterised even the very best of wartime fighter types. Work to fully understand the effect of high-speed airflow across a surface had been pioneered by Jakob Ackeret, an aerodynamicist who took the studies of Ernst Mach (18381916) and suggested that his name should be the measure by which the speed of sound was known and that multiples of that should be the “Mach” number. In a paper published in 1887, Mach displayed photographs of the shock waves coming off a projectile travelling through the speed of sound. During the early 1930s, Ackeret took Mach’s work and built wind tunnels to demonstrate how calculations based on fluid dynamics could be tested in such a facility to open the possibility of supersonic flight. He investigated the interaction of shock waves with boundary layers and used his wind tunnels to develop multistage axial compressors for jet engines. After the war, the work that German research scientists had been conducting was gathered up and taken to the United States, to Russia or to Britain, depending on who got to the facilities first! Early work by aircraft designers recognised that standard aerofoil



shapes would be inadequate for the new jets when they managed to break out toward the transonic region in level flight. Early jet fighters had round nose areas, thick wings and hinged elevators and these types were suited only to speeds well below the transonic region. But the principles coupling wing thickness to drag were becoming well known before the end of the war and the Royal Aircraft Establishment carried out tests in 1943 with the Spitfire which conclusively proved that thin wings were essential for supersonic flight. Before the Miles M.52 was cancelled all the technical drawings, specifications and research results were handed over to the Americans and gh the Bell X-1 that carried Chuck Yeager through the sound barrier bore a strikingly close resemblance to the British project. But this was largely due to parallel teams working in isolation to each other finding common solutions to physical problems. Nevertheless,, the Americans were catching up fast and considerable effort was applied by the National Advisory Committee on Aeronauticss (NACA) to problems regarding high-speed flight and the appropriate wing profiles and fuselage shapes for supersonic aircraft. But only limited convergence of research took



The very existence of the NACA in America and the Royal Aircraft Establishment at Farnborough in the UK was a bellwether for aeronautical progress on both sides of the Atlantic Ocean, albeit largely devoid of the cooperation that would have avoided some duplication of research. Nevertheless, cooperative projects tackled universal problems, with a completely new set of criteria essential for tackling issues regarding propulsion and the way air moves, and is treated, before it enters the engine and after it is combusted and discharged through the exhaust outlet. A significant design challenge is to shape the intake so that the air entering the engine can be slowed to half the speed of sound and in so doing provide some of the compression. There is also a limit on altitude by the need to maintain a density to allow combustion, which is about 131,200ft (40,000m) in the case of the turbojet or about 180,500ft (55,000m) for a ramjet. The very dynamic of a working jet or turbojet engine tends to set a limit on speed within the denser layers of the atmosphere. As air is compressed at the intake nozzle it heats up and as speeds reach Mach 5 the nitrogen in the atmosphere reacts and wastes a very high percentage of the energy involved in combustion and this has a negative return on performance. Above Mach 5, the hypersonic regime, only scramjet engines have any practical value but they are ill suited for fighters and have ever only realistically shown potential for point interception BELOW: The Grumman F9F-6 Cougar entered service with the US Navy sporting swept wings and a turbojet engine with added reheat. (USN)



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ABOVE: The Vought F-8 Crusader had a chin intake providing a shorter duct between inlet and engine and allowing the provision of a radar unit in the nose. (DAVID BAKER) over great distances, for very high-altitude reconnaissance or for propulsion systems in advanced AAMs. In theory scramjets could power hypersonic aero-vehicles up to Mach 15. The domain above that belongs to the rocket motor, totally isolated from inducted air and increasingly efficient with thinner air and at their maximum efficiency in the vacuum of space. Engineering challenges are high. The air is kept at around half the speed of sound from the space where it exits the combustion stage, along the duct to where it enters the nozzle. This is required so as to keep to a minimum the pressure loss in the duct proper. Thrust is highest if the static pressure reaches the ambient value as it leaves the nozzle and is made possible if the exit area is at the appropriate value for the nozzle’s pressure ratio. This pressure can be as low as 1.5 times the ambient pressure for a low-pressure, single-stage turbine, or as high as 30 times for a Mach 3 aircraft. The search for added thrust began at the very dawn of the jet age, the ability to increase the power of the engine either by increasing the velocity of the exhausting gases or by expanding the mass of gas expelled from the nozzle. A turbojet is transformed into a turbofan engine by increasing the amount of exhausted gas, albeit at a lower velocity. While the turbofan can produce greater thrust for a longer period they are large and unwieldy, especially for combat aircraft. Fighters can achieve greater speeds by increasing the velocity of the gases leaving the nozzle. To some extent, fighters can have it both ways. By tapping into the excess oxygen that flows past the turbine to keep the temperatures within acceptable limits for the available materials of which the turbine is fabricated, added fuel, injected in the duct to the nozzle and then combusted, increases the velocity of the exhausted gases and marginally adds mass in the form of spent fuel. Theoretically, this provides the opportunity for short bursts of speed, when taking off or at various times in flight, with the deficit, however, of increased fuel consumption and reduced flying time. Early work on reheat, or afterburning as 24



FIFTH GENERATION FIGHTERS



the British called it, was carried out in the UK by Power Jets on the W2/700 engine. It was always understood that high-performance aircraft powered by jet engines could achieve



bonus thrust from reheat and the W2/700 was the perfect place to start. In 1944 it was being designed for the Miles M.52, the aircraft assigned to break the sound barrier, a project cancelled in a shroud of half-secrets and obfuscation! After bench tests, early in 1945 this engine was flight tested in a Meteor using its afterburner to increase speed from 420mph (676km/hr) to 460mph (740km/hr). Initially, research on reheat in the US was conducted by the NACA and a flurry of research papers, many of them classified at the time, were published between 1945 and 1948, by which date the new Pratt & Whitney J48 appeared, delivering a thrust of 8000lb (36kN) with reheat and this was selected to power the Grumman F9F-6 Cougar, a sweptwing fighter which entered service with the US Navy in November 1952. Relatively quickly, other aircraft were fitted with engines designed for reheat capability, including the Westinghouse J46, which powered the Vought Cutlass. In Britain, in a classic case of developing an engine too powerful to find a user, the de Havilland Gyron was produced in the early 1950s delivering a thrust with reheat of 20,000lb (89kN) in the basic version and 25,000lb (110kN) in a developed version. It was never used in a production aircraft but, scaled down, the Gyron Junior emerged in 1953 to initially power the Blackburn Buccaneer until replaced with the Rolls-Royce Spey. By the end of the 1950s no credible fighter developed by anyone anywhere



ABOVE: The principle of the pure turbojet with an axial compressor and annular burners dominated jet fighters of the first and second generation. (JEFF DAHL)



ABOVE: The turbofan made more efficient use of air and facilitated the use of added thrust. (K. AAINSQATSI)



The afterburner ft b exhaust h t on a MiG MiG-23 23 with ith airi bbrake k pedals. dl ABOVE Th ABOVE: (DAVID BAKER) failed to incorporate a reheat capability. But what comes out the back is shaped to some degree by the way air enters the engine at the front. The F-100 represented the last US fighter to have a nose inlet, theoretically the optimum position because it has good airflow characteristics at a wide range of angles of attack, and in sideslip, and is free from flow separation incurred by other external structures on the aircraft. Yet, by virtue of its location forward of the pilot, it has to have an extended duct, either following a serpentine route below the cockpit to the engine interface or split in two to pass around the cockpit either side of the pilot. Moreover, with a nose inlet it is difficult to attach a forward-looking radar and almost impossible



ABOVE: The English Electric/BAC Lightning F6 displaying the annular nose intake with conical dielectric cone covering the radar unit. (ALAN WILSON) to locate guns in that location. Although the re-contoured nose of the F-86D made space for a radar set supporting the aircraft’s role as an interceptor, the fuselage-mounted gun packs were replaced with 24 x 2.75in rockets. Predictably, the location of the air intake migrated to the chin-mounted type with semi-circular or oval-shaped cross-section, as designed into the Navy’s LTV F-8 Crusader, in service from 1957. Located just forward and below the cockpit, the inlet duct was



ABOVE: Rarely has there been any major design proposal incorporating ramjet propulsion for fighter aircraft although this has been adopted for missiles, due to its performance value at high altitude. (WOLFKEEPERSVG)



ABOVE: Scramjet propulsion has been proposed for hypersonic speed above Mach 5 but the type of engine is inefficient at slower speeds and has little application other than for intercept missiles. (EMOSCOPES)



comparatively short and had all the advantages of a pure nose inlet, in that it maintained efficient ingestion characteristics while providing ample space for radar or armament. No US Air Force fighter has had a nose inlet since the F-100 entered service with the Air Force in 1954, wing root installations becoming favourite from the end of the 1950s with triangular or semi-circular cross-section profile. A noted departure from the rule which appeared to govern all fighters, the English Electric P-1 and its descendent, the Lightning, had a nose inlet with armament on fuselage stores positions, providing a very clean ingestion profile and low flow separation characteristics. But this was a point-defence interceptor, a missile-carrying aircraft designed to knock down high-flying bombers; combat fighters would need greater manoeuvrability, which required larger wing area and greater agility. The Lightning was an exception, bearing testimony to its design origin in 1948 when the layout and configuration was finalised, but is noteworthy in that research into its complex aerodynamic problems generated the first transonic wind tunnel built in the UK. A quick survey of its features provides a useful benchmark for comparing first and secondgeneration thinking versus the changes which occurred to stimulate third-generation design. The “over-under” engine arrangement for the Lightning pushed a mid-wing fuselage location so that the wing carry-through structure ran between bifurcated intake pipes for the upper and lower powerplants to maintain structural continuity. The wing was thin and sharply swept and slightly tapered with the added advantage that its location avoided interference drag with the fuselage. The selection of a nose inlet, rather than chin or side intakes, was based on simplicity of design, adhering to the fundamental law of reliability in that complexity increases risk on the square of the number of separate solutions: minimise the need for those solutions and reliability increases. Considering the extended operational service life of the Lightning, it remained in frontline service for almost 30 years from service introduction in 1960. The Lightning is a classic example of a specialised requirement being  FIFTH GENERATION FIGHTERS



25



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ABOVE: The early design solution for the Navy’s requirement for a defence fighter was met by McDonnell with the F3H in 1954, progenitor of the F-4H Phantom II. Note the broad chord wing and flat horizontal tail. (VIA DAVID BAKER) met so tightly that it was virtually impossible to apply the aircraft to any other role. As such its sales potential was strictly limited, and only applicable to countries that held a similar requirement for a Mach 2.2 interceptor. Moreover, despite several growth derivatives proposed and examined, the aircraft was impossible to evolve further, due to its vintage. Generally, for a manufacturer, a combat aircraft is only considered a success if it matches technical and operational requirements and if it achieves good sales. The Lightning was highly successful in the former but distinctly lacking in the latter – only 54 being sold abroad – about which the initial customer (the RAF) had little or no interest because it received exactly what it sought. US manufacturers, on the other hand, built aircraft that had great sales potential and manufacturers were backed by a government willing to support that drive for expanded production because it lowered unit cost for the initial buyer.



AN EVOLUTION OF DESIGN The technical evolution of second and thirdgeneration fighters picked up pace during the 1960s with a variety of engineering adaptations to operationally driven requirements. Most notable of which became the tortured histories of the McDonnell (later McDonnell Douglas) Phantom II and an Air Force development programme known as the Tactical Fighter Experimental (TFX). These two stories involve in sequence, a transition in fighter requirements and a classic example of political meddling to compromise the optimum design configuration. Understanding its outcome is crucial to subsequent events driving consequences that opened new concepts in design. By tracing the evolutionary transition from a mid-1950s requirement through technical innovation there is a direct link to the fourthgeneration types which emerged in the 1970s. Tracing this through two separate programmes also illuminates the extraordinary range of engineering ideas and concepts on the road to a definitive fourth-generation fighter. Two stories, each involving game-changing evolutions forged by the US Air Force and the Navy, illustrate that point. Both involve fighter requirements, fleet defence and air superiority types. During the early 1950s a problem posed for carrier-based fighters grew from the increasing power levels available from the engine manufacturers, allowing an upward trajectory for overall weight growth. By the time the Korean 26



FIFTH GENERATION FIGHTERS



ABOVE: The definitive Phantom II, the F-4B of VF-74, the first unit to fly the type. Note the upswept outer wing sections and anhedral tail, design changes made ABOV to compensate for a lack of design integration at an early stage. (MCDONNELL) War began Navy fighters began to get really heavy, the McDonnell F2H Banshee grossing 22,300lb (10,136kg) while the F3D Skynight weighed in at a maximum 26,850lb (12,205kg). By 1955 the need for an effective fleet defence fighter to reach further out from the carriers they were designed to protect imported expanded roles, heavier armament and greater range. The swept wing F3H Demon grossed out at almost 30,000lb (13,640kg) while the F7U Cutlass hit almost 32,000lb (14,545kg) and the Vought F8 Crusader weighed 34,000lb (15,455kg). The Crusader arose from a demanding specification issued in 1952 calling for a speed of Mach 1 giving the Navy its first supersonic fighter, which would also embrace novel features. To achieve Mach 1 in level flight yet operate at very low speeds for carrier operations, Vought gave the Crusader a hydraulically operated, variable incidence wing, pivoted by seven degrees around the rear spar to maintain an essentially forward-facing view for the pilot on approach and landing. Extensive use of titanium and magnesium alloy broke new engineering barriers and the use of integral fuel tanks in the wing, as pioneered by Vought’s VS44A flying boat, was a novel innovation for a supersonic fighter. Fighters of the F8 generation were responsive to operational challenges introduced by the user pushing capabilities and adaptations. When the Navy wanted to test its ability to switch fighters from one ocean to another without relying on land bases or the use of the Panama Canal, in June 1957 an F8 streaked from the carrier USS Bon Homme Richard in the Pacific to the USS Saratoga in the Atlantic via one aerial



refuelling. On July 16 that year a reconnaissance variant of the Crusader flashed across the 2445 miles (3,935km) from Los Angeles to New York in 3hr 22min at an average speed of Mach 1.1, including three subsonic refuelling hookups, sustaining continuous photo coverage all the way. The pilot was Marine Maj John Glenn. Less than five years later he became the first American to orbit Earth in space. In 1956 the F-8 Crusader took the coveted Thompson Trophy for being the first supersonic Navy fighter and the first to exceed 1000mph (1609km/hr) in level flight. But this was a time when stores and weapon loads were changing fast and the F8 had four fixed forward-firing 20mm Colt cannon, four Sidewinder AAMs or up to 5000lb (2268kg) of bombs or rockets. Two years earlier, on October 18, 1956, the Navy had issued a letter of intent to McDonnell Douglas to produce the AH-1 attack aircraft but fundamental changes were put into effect the following year changing its role to a long range, high altitude interceptor and its designation to F4H-1 Phantom II. Instead of carrying guns it was to be equipped exclusively with missiles and a second crewmember was mandated as a radar operator as advanced electronics and AAMs found unprecedented favour. Because of its success with the F8, Vought was encouraged to bid against the F4H-1 and an existing design concept, the V-401, was stood up to be known as the XF8U-3 Crusader III. Vought’s idea behind the upgrade to the Crusader III was essentially the same as that adopted by other century-series fighters developed for the Air Force – replace the workhorse Pratt & Whitney J57



ABOVE: The Vought F8U-3 Crusader III, in many respects far superior to the Phantom II, with similarities to its F-8 Crusader predecessor in name only, useless as an advanced two-seat interceptor and fleet defence fighter and devoid of any other role. (USN)



ABOVE: NASA tested the Crusader III in extensive flight trials against the Phantom II and found it superior in agility, dogfighting and interception. (NASA) ABOVE: An artist’s impression of the Vought Crusader III displaying the ventral fins deployed for controllability and stability at high speeds and high altitude. (AEROSPACE PROJECTS REVIEW) turbojet engine with a J75, with afterburner, and get almost twice the performance. This required a new inlet which had greater sophistication than the plain, fixed geometry of the F8. It retained the chin position but adopted a sharply sloping Ferritype inlet with a moveable wedge on the interior to absorb shock waves before engine ingestion. Crusader III looked remarkably similar to the F8 but shared very few components or systems. The wing had reduced thickness but retained the variable incidence capability while the tail was new with double the area and increased chord. Because designers believed it was capable of sustained speeds of Mach 2.7, it had extensive use of titanium for which a new spot-welding technique was developed for its application, while much of the rest was a stainless-steel honeycomb sandwich. Special glass was used for the curved, one-piece windshield and although supporting an enlarged intake duct and engine bay the fuselage was considerably deeper, which allowed a 25% increase in fuel capacity.



In what became the classic case of designing an aircraft for too specific a role, Vought in America succumbed to the same problem experienced by English Electric/BAC with the Lightning in Britain, although the latter did not have a competitor to give it a free run in the absence of an alternative, as did the former. Loaded with advanced avionics, radar and fire control systems for its all-missile armament, the single-seat XF8U-3 had no room for a radar operator/weapons officer essential for the new generation of fast jets as perceived in the late 1950s. Capable of speeds in excess of Mach 2.3 and a ceiling of 65,000ft (19,800m) with



controllability maintained by two large moveable ventral fins near the tail, Vought’s contender was in every measure far superior to the Phantom II. But as a multirole aircraft it was useless. In November 1958 the Phantom II became the winner and the five existing Crusader III test aircraft were handed over to NASA, where four were used to keep one flying for research into noise problems with supersonic aircraft, automatic pilot projects and high speed radar tracking. When NASA got its hands on the XF8U-3 it sent it for flight testing and, operating out of NATC Pax River in Maryland, their test pilots flew it persistently against F4 Phantom IIs,



ZERO-LENGTH LAUNCH Over the immediate post-Second World War period, various degrees of thrust augmentation had been either necessary or desirable, adding supplementary energy to either reduce takeoff runs or to increase speed at selected regions of the flight profile. Fighters require this selective acceleration more than any other type but early in the 1950s tests were carried out using rocket propulsion for what became known as zero-length launch (ZLL), whereby the aircraft was propelled up a short, inclined ramp and accelerated to flying speed by a powerful solid propellant rocket motor. Republic F-84 Thunderjets were attached to the boost motor used to launch the Martin MGM-1 Matador, which provided a thrust of 52,000lb (240kN), but the F-100D Super Sabre was test fitted with a



powerful rocket motor with a thrust of 135,000lb (600kN), which burned out in seconds and fell away leaving the fighter to continue on its way under its integral jet engine. The ideas had been to use ZLL launchers to disperse deployment in the event of war to evade detection and enhance survivability. The equipment proved too bulky, difficult to move around and lacking security for a force potentially equipped with tactical nuclear weapons. They were tried out by several countries, the requirement for dispersed operating bases in Europe being particularly acute due to their proximity to Warsaw Pact countries. But for Europe a novel solution came with the directed-thrust VTOL Harrier, unique in its class but a foretaste of what would be built into one fifth-generation fighter.



dash the variable ABOVE: Designed for low speed landing and supersonic dash, geometry “swing-wing” on the F-111 could sweep from 16 degrees to 72.5 degrees with leading edge slats and double slotted flaps. (GENERAL DYNAMICS)



ABOVE: With a shorter nose and several changes in equipment, the visually similar F-111B was to have been the naval version until rejected as unsuitable for carrier-based fleet defence activity. (USN)



ABOVE: A US Air Force F-100D is test-fired from a Zero Length Launcher powered by a boost motor from the Matador cruise missile. The concept was never deployed operationally. (USAF) FIFTH GENERATION FIGHTERS



 27



SECTION 1 – CHAPTER 3 that for the recoverability it promised should one engine fail far from the safe deck of a friendly aircraft carrier. And it was rugged, able to fly at Mach 2.2, max out at 60,000ft (18,000m) and carry 18,600lb (8440kg) of ordnance on nine hard points. And it eventually got back the gun initially removed. In every respect, the Phantom II redefined the requirement for a fighter and made itself available for effective operational service with the Air Force. It remains in service on a limited basis today, nearly 60 years after its introduction. ABOVE: The F-111 incorporated side-by-side seating for the pilot and weapons officer in a spacious cockpit more akin to a bomber than the fighter it was originally specified to be. (USAF) which it consistently beat during mock attack or combat tactics. The Navy put a stop to the tests when rumours began to leak out and criticisms were expressed against the new Phantom II. Ironically, the Phantom II went on to become one of the most successful aircraft ever produced by American industry with almost 5200 built for domestic and foreign use, securing an export market unavailable to niche aircraft designed for a specific operational role. During its design gestation, the cards were stacked against the Phantom II, as for three successive years from 1955 the Navy changed its specific role on an annual basis,, its design reflecting brute-force solutions. This aircraft had all the potential for being a failure and only after test trials began with the F4H-1 were aerodynamic and handling problems solved by applying dihedral to the outer wing sections and anhedral to the horizontal tail. Nothing about the Phantom II was refined, its engineers not subscribing to the blended aerodynamic profiling which was then being whispered about, nor to the integrated airframe and engine design so lauded in a future decade. But it had two engines and the Navy liked



REDEFINING THE BREED The second story involving transitional development is closely parallel in date to the struggle to find a progressive role for Navy fighters- which resulted in the demise of the Vought F8 and the success of the F4 Phantom II. And strangely, it also involves the Navy, but not to begin with. At the end of the 1950s the Air Force wanted a successor to the F-105 tactical fighter and ground attack aircraft and raised the Tactical Fighter Experimental (TFX) g programme to evaluate bids received from



ABOVE: The F-111 was suitable for all-weather, day or night operations. With a semi-glass cockpit the aircraft straddled the generations and proved adaptable to a variety of roles. (USAF)



MIXED-POWER ROCKET PACKS Hybrid propulsion applications were sometimes adopted for specific mission requirements, an example being the liquid-propellant rocket motor used to boost interception speed on the Dassault Mirage III. The SEPR 841 rocket



ABOVE: The SEPR 841 rocket boost pack designed for the Mirage III interceptor, fitted so that the pilot could switch it on for short bursts to increase speed. (SEPR) 28



FIFTH GENERATION FIGHTERS



pack used hypergolic propellant which ignited on contact (nitric acid and TX2 furaline) but the cost in propellant weight and the rate of consumption compromised other aspects of the aircraft’s performance. The objective had been to carry the removable pod for intercepting high-altitude bombers, pushing the speed of the aircraft from Mach 1.4 to Mach 1.8 and allowing the interception altitude to increase from 65,000ft (20,000m) to 75,000ft (23,000m). A developed version of the pack, the SEPR 844 used nitric acid and kerosene for simpler operation but the need to knock down bombers fell back on to high-altitude surface-to-air missiles. Several attempts were made to marry rocket packs with conventional jet fighters, even to the extent of building in a rocket motor for optional use, such as the Saunders Roe SR.53. Other rocket packs were incorporated for supplementary boost in other aircraft, including the Vought F8 Crusader III. With significant performance improvements in turbojet and turbofan engines, these rocket packs were considered too cumbersome, too heavy and potentially catastrophic and were soon outmoded.



several contenders. When Robert McNamara became Secretary of Defense under the incoming Kennedy administration in 1961, in a drive to economise by reducing the number of different aircraft between the services, he married the Air Force requirement to one from the Navy for a fleet defence fighter capable of defending carrier battle groups. The only shared requirements from the two services were for high supersonic speed, twin engines, two crew, heavy armament and long-range capability. Despite protests from the Navy – who never did believe one aircraft could serve the needs of the two services – proposals came in from Boeing, General Dynamics, Lockheed, McDonnell, North American and Republic. In January 1962 the selection board recommended further bids and Boeing and GD were selected to refine their proposals, eventually choosing the Boeing 818 design. This was endorsed by the Air Force but rejected by the Navy before further evaluations and submissions, with Boeing again coming out on top. In November 1962 McNamara selected GD over Boeing, citing a greater degree of commonality between the g two, giving the kind of cost savings sought as prime criteria for selection. Investigations followed during which it emerged that GD was in great danger of going into bankruptcy unless they got the TFX contract and questions were raised as to the real reason for the decision but the selection held and the F-111 was placed in development. The Navy requirement, defined in its Fleet Air Defense Fighter (FADF) document, wanted a weapon system to drive the specification for a new launch platform. The FADF solution was to design an aircraft around a missile which could bring down offensive weapons with a Mach 4 capability fielded by the Soviet Union as threats to the carrier battle groups. The Air Force had chosen to counter massed fleets of incoming enemy bombers with nuclear-tipped missiles, destroying them in the blast wave from a 1.5KT warhead. The Navy had to counter dispersed threats, each of which would have to be separately targeted. It needed both a long-range missile attached to a radar system capable of acquiring and tracking multiple targets and a launch platform for fleet defence over great distances. For the first time, the Navy reasoned that it was better to place control of the intercept in the missile rather than in the airframe of the carrier and build into the missile range and flexibility to seek and destroy selected targets.



ABOVE: The F-111 had great flexibility and was adapted to carry a payload of up to 31,500lb (14,300kg) of bombs on nine points. Here, it displays a payload of Matra Durandel concrete penetration bombs at Eglin Air Force Base. (USAF)



ABOVE: Uniquely, the F-111 incorporated an escape capsule designed to ensure the survival of both crewmembers, this example doubling as a simulator. (DAVID BAKER) In converging the two requirements, McNamara had successful got the Navy to quietly retire the original FADF specification. Two F-111 configurations would be built: the F-111A for the Air Force and the F-111B for the Navy, a great degree of commonality between the two ostensibly providing considerable cost savings as a result. The search for commonality had driven compromise and there were significant engineering challenges as a result. The very separate and distinctive roles of dogfighter and tactical bomber were largely incompatible and the Air Force wanted the F-111 as an F-105 replacement. These two requirements gave aerodynamicists and engineers a serious headache over optimised wing/ fuselage shapes. A variable-geometry wing planform could provide low-speed lift and control stability without detracting from supersonic performance but serious mechanical problems delayed a design solution. In 1958, engineers at the NACA Langley Aeronautical Laboratory found a solution by adopting an idea from the British aircraft industry separating a single pivot into two separate pivots, one for each wing and located outboard of the outer fuselage wing glove. The blended inner wing and fuselage juncture would provide a deep structural unit where the pivot box could be located. The Navy had been disenfranchised from the commonality programme when McNamara had given programme lead to the Air Force, calling for the Navy to eliminate its bespoke requirements and merge with the Air Force on specification. But just as the two very different requirements had been shackled together and pruned away from their original objectives, the converged design began to depart from the true principle of commonality: the Navy version would take far longer to develop because the radar systems were very different to support the separate requirements. By 1967 it was clear that McNamara’s commonality programme had sunk without trace and the Navy was clear that it would not accept an aircraft which ran very short of its requirement. While the F-111A went on to perform well and to fill a particular niche in the Air Force ground strike and attack role, albeit after a shaky start, the Navy rejected the F-111B and asked Grumman to examine a new design for a dedicated replacement. In the five years that had elapsed during the TFX debacle, the threats had shifted and now long-range supersonic bombers of Soviet naval aviation posed new challenges. Moreover, the Air Force was now faced with a new generation



ABOVE: A Grumman F-14D of VF-213 over the Persian Gulf, an aircraft which finally satisfied the Navy requirement for a long-range fleet defence fighter with unique capabilities which were never replaced after its retirement in 2006. (USN)



ABOVE: The “pancake” area between the two Pratt & Whitney TF-30 turbofan engines, which gave the aircraft a top speed of Mach 2.34, came in useful for ordnance. The F-14 had a payload capacity of 14,500lb (6600kg). (DAVID BAKER) of Russian aircraft such as the MiG-25 Foxbat, which posed a performance challenge. From the insoluble problems posed by commonality emerged two very separate and distinct fighter types which would satisfy respective requirements. The Navy got the Grumman F-14 Tomcat while the Air Force received the McDonnell Douglas F-15 Eagle. Each represented a new approach to design



characteristics, displaying a more concerted approach to wing/body blending and powerful turbofan engines. The F-14 entered operational service in 1972 followed by the F-15 four years later. Both were twin-engine aircraft and were designed for air superiority. But the Tomcat got its AIM54 Phoenix long-range missile system satisfying the role of fleet defence fighter and was, eventually, adapted t a ground attack role; the F-15 had a to greater capacity to operate as a bomb t truck while retaining its air defence role. The evolution of generational types had carried the aircraft and engine industry through to a high-tech age of advanced design engineering while adapting to the more demanding requirements of highly advanced avionics, radar, fire control equipment and weapon systems. Despite predictions, the gun had not entirely disappeared and the missile had not completely dominated the air battle environment. The war in Vietnam saw to that. But the technological developments that had been practised were as nothing compared to what was to come, transforming the air battle and redefining the role of the fighter.



ABOVE: Representing a new generation of air superiority fighter, an F-15C of the 71st FS, 1st FW, on combat air patrol over Washington, DC, on October 7, 2007. Note the profile of the adjustable engine nozzles. (USAF) FIFTH GENERATION FIGHTERS



29



SECTION 2 – CHAPTER 4



The Search for Stealth CHAPTER 4



S



uccessive generations of front-line combat aircraft were defined by technological capabilities. Some of those were driven by inventions, discoveries and innovations making new defensive and offensive weapons systems possible. In turn many of these developments drove the specification for aircraft types, designed to respond to, or exploit the new possibilities. Paradoxically, each successive generation pushed the combat aircraft further away from the purest definition of a fighter: to engage the enemy and bring him down. Instead, added roles and responsibilities burdened the fighter with additional weight, stores points and compromised design requirements. This would further compromise the search for stealthy fighters forced through adaptation to take on additional roles. First-generation fighters were little more than jet-powered equivalents to the pistonengine types that emerged at the end of the Second World War, carrying guns and little else. The emergence of second-generation fighters such as the F-100, F-105, F-106 and MiG-21 were defined with supersonic capabilities, on-board radar and the first guided air-to-air missiles. Thirdgeneration types of the 1960s carried improved avionics but expanded into multirole applications as defined by requirements and specifications to industry. The age of the “pure” fighter had gone. With that came the first precision munitions for types such as the F-4 Phantom II, the MiG-23, -25 and -27 and the Mirage F-1. From the 1970s, developments in avionics



ABOVE: F-106 fifighters ffrom the 102nd FIW during William Tell exercises in 1984; a type which carried the air defence f role ffor many years but was compromised by a distinctly unstealthy configuration. (USAF) and enhanced radar systems dominated the fourth-generation types such as the America’s F-14, F-15 and F-16, Russia’s MiG-29/31, Europe’s Tornado and Typhoon programmes as well as the Gripen from Sweden and Rafale from France. From these fighter types dedicated role changes began to appear producing bomb trucks such as the F-15E Strike Eagle which first took to the air as a modified F-15B airframe on July 8, 1980 and went on to play a major role in air-to-ground operations around the world. Essentially a third-generation type, the F-111A which began in concept as a tactical fighter had switched to the fighter-bomber role before service introduction, a precedent for a number of discreet role reversals accorded to selected types. The F-111 would progress to perform as a nuclear strike aircraft designated FB-111A, 76 of which were acquired by Strategic Air Command as a manned strategic bomber in 1970. Largely as a result of lessons learned in Vietnam, in 1981 the EF-111A went operational for dedicated electronic warfare, sporting a large fin tip antenna for the AN/ALQ-99E jamming system with antennas in two large canoe-shaped radomes under the fuselage.



THE SEARCH FOR STEALTH



ABOVE: Aircraft developed for an air superiority role were adapted to multirole functions increasing their visibility to long-range radar systems, as compromised on the F-15E Strike Eagle with external stores which enhanced its visibility beyond visual range. (USAF) 30



FIFTH GENERATION FIGHTERS



Arguably the most effective development during the 1970s and 1980s, however, was the introduction of low-observables technology, otherwise known as “stealth”. While we have here being decrying the watering down of “purist” fighter principles forged in the first major air battles of the First World War more than a century ago, in an unexpected way the concept of stealth technology speaks to that most basic of fighting principles, where



combat favours the element of surprise. In theory, this had been sought by air fighters from the earliest days of aerial combat, where usually the sun was used to hide the presence of an attacker homing on an intended victim. With the introduction of radar targeting and interception during the Second World War, first for night-fighting and then generally for air defence, the parameters shifted to the electromagnetic spectrum. Radar works by receiving a return signal reflected from a solid object, the strength of the signal being proportional to the observed visibility of the object. That “observed visibility” is a measure of the object’s radar cross-section (RCS) and is dependent on the proportion of the signal which is reflected back. Considerable secrecy surrounded the work on radar and ways to evade detection were carried out in German laboratories during the Second World War. After the German surrender, as the victorious allied powers sought to obtain as much of this work for their own exploitation some ideas were researched and investigated using data and results from extensive studies and tests conducted toward the end of the war. One of those was the marriage of flying-wing design concepts and low-observables (LO) technology. Some of the claims made by German designers were pure myth while other techniques inadvertently did contain stealth characteristics. One example was the Horten Ho 229 which was developed by Reimar and Walter Horten, advocates of tailless “flying-wing” designs, and built by the Gotha works in 1944. The German Air Ministry wanted a bomber capable of carrying a 1000kg (2200lb) bomb a distance of 1000km (620mls) at 1000km/hr



ABOVE: Preserved remains of a Horten Ho 229, placed in early production by Gotha but never deployed operationally, an early example of the advantages of the flying wing concept. (SMITHSONIAN INSTITUTION)



ABOVE: Germany’s Horten Ho 229 was the culmination of work by the Horten brothers on flying wing concepts that exhibited some stealth characteristics, claimed by the designers to have been implicit in selection of this configuration, in reality an inadvertent advantage when seeking low drag and extended range. (SAMOLET/DEREDOS) (620mph). Only by reducing the cruise power, said the Horten brothers, could this condition be met. That could most easily be achieved by significantly reducing drag by creating a tailless, blended wing-body shape powered by jet engines buried in the wing/fuselage root. The Ho 229 was built and flown on several occasions but development was held back by numerous factors and the type never entered service. The Horten brothers had been correct in selecting this design concept for minimum drag and the aircraft was certainly less visible to radar than a conventional aircraft of this size would have been. There were no abrupt angles between the wing and the fuselage, no large vertical tail to reflect radio waves and no propellers to appear as bright discs on a radar screen. When the type was subjected to a detailed analysis by Northrop Grumman long after the war it was determined that, with a wing span of 55ft (16.8m), it had only 80% of the visibility presented by a lightweight fighter such as the Messerschmitt Bf 109, which had a wing span of 32ft (9.8m). But claims by Reimar Horten that he had mixed charcoal with the glue to bond the wood laminates of which the structure was made in an attempt to achieve a low reflection were rebuffed by a chemical analysis which showed there was no evidence of such a substance. However, we may be too quick to rebut this claim as there was indeed a noticeable change



ABOVE: Measurements of the wood laminates used in fabricating the structure of the Ho 229 to determine the possible addition of charcoal to improve the stealth characteristics of the aircraft. (SMITHSONIAN INSTITUTION) in the dielectric constant. Horten maintained that the carbon charcoal, which would have significantly absorbed propagated radio waves, was to have been used in production versions while the V3 prototype taken to the United States, and subject to tests, was the earlybuild which may not have had that additive. The reason for this detailed scrutiny of the Ho 229 story is that, if it were true that the aircraft was conceived not only as a low-drag bomber but also to have stealth qualities, it wass about 30 years ahead of its time. Yet the realityy of this is lost in obfuscation, confusion, lying and finger-pointing. After the war German scientists, engineers, technicians and labourerss



ABOVE: An iconic symbol of the Cold War, Roy Chadwick designed the Avro Vulcan for high-altitude, high-speed flight profiles, creating a delta-wing configuration which achieved greater levels of stealth than its contemporaries, only compromised by a large vertical tail. (DAVID BAKER)



were only too willing to blame those no longer alive (usually in high political or military positions in the Third Reich) for missed opportunities, clearly ineffective decision-making or deliberate mismanagement; these men were also quick to claim they were aware of applications that, in reality, only became apparent when aallied brains were matched with those ffrom the German research facilities to point out subtle possibilities such as tthe variation of a shape to effectively produce a more stealthy design. During the Second World War, aand for some time after, other priorities ssuch as rapidly evolving engines, aarmament and radar systems inhibited tthe development of stealth aircraft ttechnology. The allies had known that tthe de Havilland Mosquito, fabricated ffrom wood laminates, was less easy to detect on enemy radar screens than aircraft made of metal but factors essential to a true stealth capability were not applied for several decades. For some time it just did not seem as important as the technical development of conventional high-performance aircraft. Nevertheless, the delta-wing applied to the design of the Avro Vulcan, set out in 1947, was a superb example of how a search for aerodynamic efficiency, high-altitude capability and great range inadvertently converged to provide a shape which exhibited one of the lowest RCS readings at that time. With engines submerged in the thick wing root, only the vertical tail compromised the perfect shape for



ABOVE: Jack Northrop harboured a lifelong dream of applying the flying flying-wing wing concept to civil and military aircraft, keeping alive the innovative design configuration that would result in the B-2 several decades later. (USAF) FIFTH GENERATION FIGHTERS



31



SECTION 2 – CHAPTER 4



ABOVE: The jet-powered YB-49, a conversion from the XB-35, which came close to a production order but lost out to immature technology incapable of resolving flight control issues with the flying wing. (USAF)



ABOVE: The Northrop XB-35 flying wing bomber contender with dual contra-rotating propellers driven by pusher-engines embedded in the wing. (USAF) stealth. In reality, the Avro design team gave no attention at all to low-RCS capabilities, the low-observable characteristics being an unintended consequence. But it certainly got the Americans thinking and on at least one occasion a Vulcan suddenly appeared unannounced, low over a mid-western State to the annoyance of the Defense Department! Neither had the stealth characteristics of Jack Northrop’s flying wing designs been intended when he developed his own version of such a concept, the propeller-driven XB-35 which was awarded a development contract in 1941. When technical problems prevented it from achieving operational status, a jet version designated YB-49 was first flown in October 1947 – the month the newly independent US Air Force was born. That lost out to a much more conventional contender, the Convair B-36, but Jack Northrop never gave up on his flying wings, a dream realised with the Northrop Grumman B-2.



ABOVE: Lockheed design engineer Clarence “Kelly” Johnson poses at the wing tip of a U-2 spyplane, the company’s first entry in a succession of projects that would point the way toward a true stealth design concept. (USAF)



that would scatter the radio waves and redirect them away from the receiver on the ground. One effort produced a conductive c coating known as Wallpaper that would b applied to the surface as a deterrent be against higher frequency radar. Really low frequency radars of around 70 MHz would be countered by a system dubbed Trapeze in which a series of wires were installed standing proud of the leading and trailing edges of the wings and horizontal tailplane. Other wires ran diagonally across the engine inlets. Low frequency radar was addressed by Wires, a series of ferrite beads strung along wires hung out between the nose and the tail and up the leading and trailing edges of the vertical stabiliser. The effort proved fatal when the Wallpaper wires caused overheating. The engine stalled and pilot Robert Sieker was killed. When deployed on tests known as Covered Wagon, the first of which took place on July 21, 1957, it became clear that the measures would be ineffective and it was decided to



FOR OPERATIONAL REASONS The pressing need for a dedicated attempt to produce an aircraft which was primarily designed to possess low-observables characteristics came via the Lockheed A-12. That in turn was developed when Lockheed failed to find a stealth capability for the legendary U-2 spyplane. The urgent need to produce a low-observable aircraft was triggered on July 5, 1956, when a Russian A-100 Kama radar locked on to a U-2 flying across Smolensk en route to Moscow at an altitude of 70,000ft (21,400m). At first the Russians did not believe the object was real, convinced that no aircraft could fly that high they passed it off as a glitch. In any event, the S-25 Berkut (NATO reporting name SA-1 Guild) AAMs were not deployed in that area and there was no possibility of a response. Under Project Rainbow, Lockheed chief designer Clarence ‘Kelly’ Johnson was asked by U-2 CIA project director Richard Bissell to join a select team seeking ways to make the spyplane stealthy. Given that the actual shape of the aircraft could not be significantly altered, the only options available were to absorb as much radar energy as possible or to create reflections 32



FIFTH GENERATION FIGHTERS



ABOVE: Lockheed’s Mach 3 A-12 was conceived as an unarmed reconnaissance aircraft and as such was the first serious attempt at producing a stealthy aircraft. This particular example is the ninth in a development batch of 25. (USAF)



ABOVE: The YF-12A derivative of the A-12 incorporated AN/ASG-18 radar and was to have been capable of carrying four AIM-47A missiles on rapid-action snap-open/shut internal bay doors so as to minimise compromising its stealth characteristics. (USAF) cancel the programme. But the research had revealed much more than its intended purpose, showing that a stealthy aircraft would need to be designed from the outset for low-observables. The materials, structural design, engine intakes, wing/fuselage shaping and exposed surface structures would have to drive the configuration. As the work expanded, more people got to know about the effort and the programme went darker – becoming GUSTO, with very tight clearances in the Keyhole spectrum of intelligence categories and only those with a need to know getting involved. That programme led directly to the Lockheed A-12 OXCART programme. Thus began a line of legendary aircraft which would migrate through the twoman YF-12A to the SR-71, still an outstanding technical achievement in today’s terms and one which began a direct line of development through stealthy intermediaries to radical new concepts for low-observables technology. The A-12 was perfectly formed to satisfy the requirements for a stealthy penetrator, responding directly to major developments with Russian anti-aircraft capabilities, realised on May 1, 1960 when a U-2 piloted by Francis Gary Powers was shot down and put on trial, humiliating the United States. President Eisenhower, already paranoid about losing one of the US’s most secret projects, grounded the U-2 for a while and desperately sought ways to replace the spyplane, approving development of the A-12 and placing greater emphasis on the spy satellite, not yet ready to provide reliable data but with outstanding potential. These events helped shape the determination to expand a programme of research into a catalogue of essential stealth capabilities and from that came a more structured approach to examining the way radio waves could be absorbed, deflected or changed to minimise the effective RCS of a manned aircraft. At first there was very little interest in using stealth, except for covert intelligence gathering with specialised aircraft. In fact, the US was not alone in generally disregarding stealth as a meaningful contribution to air combat requirements, for Russian defence authorities too saw little value in this exotic research. Yet paradoxically, the direct line of association that stimulated development of modern stealth characteristics, today considered a vital capability for fifth-generation air combat



ABOVE: Developing new concepts for stealth fighter/attack aircraft design, Lockheed produced a test vehicle under the Have Blue programme, which aimed to demonstrate a faceted design configuration. (DARPA)



aircraft, began with the work of a Russian physicist, Petr Ufimtsev. Born in 1931, Ufimtsev worked at the Soviet Ministry of Defence on radar systems and associated technology exploring electromagnetic wave propagation. Astonishingly, because the Ministry felt it had no practical value, he received permission for his work to be published in international journals where he described mathematical models for finite analysis of radio reflection. Published in 1964, his paper Method of Edge Waves in the Physical Theory of Diffraction showed how the RCS was determined by the edge shape and not exclusively by the size of the aircraft.



REDEFINING STEALTH By the early 1970s Lockheed had a commendable track record in building radical new aircraft (the U-2 and SR-71 to name two) and Denys Overholser, a mathematician working with the company, decided to take Ufimtsev’s work and apply it to a new computer programme which he called Echo 1. With this he was able to show that an aircraft with an exterior surface formed of flat panels faceted into the



approximated contours of an aerodynamic frame would have unusually low RCS and be capable of operating in heavily defended skies, shrinking the effective radius of radar sites to open up large areas of the sky to relatively safe penetration. An aircraft comprising faceted surfaces would deflect in different directions virtually all radio waves encountered by the structure, leaving very little to reflect back to the propagating radar site. In this way, stealth could be made to work not by making the aircraft “invisible” to radar – nothing could do that – but by shrinking the effective radius of the propagating site. But in making the aircraft virtually invisible to radar in this way, it moved the aerodynamic profile outside the range of static stability and would be impossible to control through conventional manual or assisted control inputs. Positive stability is sought by designers



RIGHT: By comparison, the underside of the refined F-117 was flatter with more subtle means of achieving stealth and incorporated a V-tail configuration. (DAVID BAKER)







ABOVE: The underside of the Have Blue prototype exhibited an elaborate arrangement of flat panels and inward sloping vertical tail surfaces. (DARPA) FIFTH GENERATION FIGHTERS



33



SECTION 2 – CHAPTER 4



The upper surfaces of the F-117 carried compounded facets with a faceted dome for the pilot and a flat exhaust slot to minimise infra-red detection from heat generated by the engine. (DAVID BAKER)



seeking a safe aircraft easily controlled by minimal input and, theoretically, able to fly safely “hands off” and without disrupting control inputs. But these qualities have their drawbacks in that such an aircraft will resist induced changes in attitude, essential for directional control, and always try to oscillate around a tight harmonic motion. It is desirable to design into the basic aircraft some degree of inherent instability – enough to allow the aircraft to readily accept bank or pitch moments but not enough to totally upset its equilibrium. In fact, the less inherently stable the aircraft is the fewer deflections are required from the control surfaces and this reduces imposed stresses from drag as well as stress on the structural surfaces themselves. As Overholser worked to create a practical but truly stealthy aircraft it became apparent that an effective design would incorporate such a high level of inherent instability. He concluded that it could only be kept in the air by a computerised flight control system balancing the control inputs from the pilot at one end with multiple sensors preventing it from literally falling out the sky at the other. But inherent instability, together with its enhanced manoeuvrability, was already being applied to the General Dynamics F-16, which was to make its first flight on January 20, 1974, about which more in the next chapter. When Ufimtsev first wrote about his work, the possibility of controlling an aircraft with inherent instability was a distant hope but rapid developments during the 1960s and early 1970s allowed such a possibility to be reconsidered. Computers, software and electronic control systems were already demonstrating a level



ABOVE: This excellent view of the upper surfaces displays the detailed attention paid to external shaping of the faceted panels. (USAF) 34



FIFTH GENERATION FIGHTERS



ABOVE: Front-on, engine inlets had a mesh screen to prevent reflections off turbofan blades and to further suppress reflective radar returns. Note the serrated edge to the canopy. (USAF) of effectiveness and reliability that would open the possibility of designing, and safely flying, an aircraft built around these principles. It was largely as a result of the Vietnam War that lessons learned dictated a change in philosophy of combat aircraft design. Far from evolving into a push-button age of automated systems and robotic exchanges between antagonists, air warfare had ably demonstrated that basic principles of dogfighting and air-to-air combat were just as important in winning the battle and staying alive as they had ever been. That, and the surge in air defence capabilities with AAA and SAM sites creating “nogo” areas in skies above high-value targets forced



a rethink on how to make aircraft more survivable – right across the spectrum of air combat and ground support. And so was born what became the F-117A, the first real step on the road to a truly stealthy aircraft for a fifth-generation fighter. A total low-observables strategy is defined by more than just giving the aircraft a low RCS, it must also have low thermal emissivity to avoid infra-red detection, and it must have a low acoustic signature. These aspects were combined into a prototype model in 1975. Known as the “Hopeless Diamond”, because of its similarity to the shape of the Hope Diamond, it led to the joint programme managed by the Defense Advanced Research Projects Agency (DARPA) known as Have Blue to the very few who knew of its existence. Have Blue was essentially an exercise in integration as important for the eventual evolution of fifth-generation fighters as the c conformal blended wing/body concept h been for future stealth concepts had a low-observables design. Taking and fl fly-by-wire (FBW) technology from the F F-16 and jet engines from the Northrop T T-38A training aircraft, the three subscale p prototypes incorporated cockpit e environmental systems from the Lockheed C C-130 and several subsystems from off t shelf. In record time and for a low the b budget, the first flight of a demonstrator o occurred on December 1, 1977. From successful flight test and c concept evaluation, the demonstrator p programme led to a significant increase in ffunding, for both a full-scale stealth fighterbombe bomber and a structured stealth research and development programme. Convinced of its value as a potential game-changer, the Air Force got extra money and the political support was found for a development programme, Senior Trend. Denys Overholser was on board as the Lockheed computer wizard and Bill Schroeder was recruited as the mathematician within a very small team managed by Alan Brown under Ben Rich, then the director of the Lockheed Skunk Works. The Air Force made a commitment to develop what it designated as the F-117 on November 1, 1978 and shortly thereafter awarded Lockheed the contract to enter fullscale development and production. This was fast-tracking in the manner most programme managers only dream of but it was unique and demonstrated the overwhelming conviction held by its advocates and they were the ones with



ABOVE: An F-117 on the ramp. Limited in capability, the aircraft was an outstanding example of stealth achieved through complex mathematical algorithms creating a shape which could only be kept under aerodynamic control by a computer-controlled digital flight control system. (USAF)



PRINCIPLES OF RADAR



ABOVE: The Northrop Grumman B-2 Spirit was designed with third-generation stealth concepts significantly more advanced than those employed for the F-117, enabling the development of a truly stealthy flying wing strategic bomber. Note the angular pattern of matched leading and trailing edges. (DAVID BAKER) the power and influence to make it happen. The designation indicated the F-117 to be a fighter but it was not, its role as an attack aircraft defined by its internal weapons carriage without external stores points. The internal weapons bay was covered with rapid-snap-shut doors designed with a serrated edge. Internal carriage positions allowed for two Paveway or JDAM munitions or a single nuclear weapon. The aircraft itself was a somewhat conservative expression of stealth application in that it was subsonic due to the General Electric F404 turbofan engine selected for its sympathetic synergy with acoustic stealth and lack of afterburner, the use of which would expose the airframe to high infra-red detection levels. The aircraft had quadruple redundant FBW controls to make it flyable and advanced avionics packages and navigation systems with an integrated avionics suite. Navigation was achieved through GPS and a sophisticated inertial system, each chosen for passive operation so as not to require propagated signals and all of which are described in subsequent chapters insofar as they relate to fifth-generation fighters.



Although first demonstrated in Germany before the First World War, development of radar using reflected radio waves to detect solid objects made remarkable progress in Britain during the late 1930s, with the Chain Home series of coastal stations operating at 20-50MHz and designed to detect incoming bombers. Initially, this gave the RAF an advantage over German raiders because they could be observed before reaching the coast by fighters directed on to them. But fighters vectored to enemy aircraft approaching at night or in poor weather required some additional form of contact to close in and intercept the target. In 1936 Edward Bowen developed a small air interception set which was known as the RDF-2A which were initially fitted to Blenheim and then Beaufighter night fighters. Later in the war, significant progress was made with the introduction of the Mk VIII radar sets fitted in Mosquito night fighters which enabled them to track Lichtenstein radar sets operating from German aircraft. The losses sustained by the Luftwaffe were considerable, sufficiently alarming to focus attention on research into stealth design whereby the shape of the aircraft



HIDING IN PLAIN SIGHT The aircraft made a name for itself during the Gulf War of 1991, although initial claims that the F-117 contributed a mere 2.5% of coalition aircraft while attacking in excess of 40% of targets, were not substantiated in post-conflict analysis. Nevertheless, the type played an important role in supporting more conventional air strikes despite it never being seriously integrated with non-stealthy fourth-generation types. However, the outstanding value of this aircraft was in its demonstration of faceted stealth technology and in the grouping of separate low-observables within a single platform. As evaluated under a variety of conditions, the F-117 displayed an RCS of 0.0108ft² (0.001m²)



ABOVE: A Junkers Ju-88 at the RAF Museum, Hendon, displaying a Lichtenstein radar with nose-mounted antennas ushering in a new era in air interception and one which would drive a need for stealth. (DAVID BAKER) and adopted several extreme design restrictions to ensure optimum low-observables levels. These included a 50-degree wing sweep which limited the aircraft to subsonic speeds. The use of faceted surfaces was a direct product of the then limited computer capabilities and software but some technology would remain for evolved development leading to the sophisticated



ABOVE: The first public flight of the B-2 displaying the design characteristics derived from the same physical and mathematical models now employed for fifthgeneration fighters. (USAF)



itself would minimise the quanta of radio signal reflected back, in effect scattering the signal so that the signature was so small that it would be interpreted as “noise” in the system. The degree to which radio waves are scattered depends on the frequency of the wavelength and on the shape of the target. If the wavelength is longer than the target, perhaps several metres, the reflected signal will be poor and may go undetected. If it is shorter than the target, the associated resonance through Rayleigh scattering will be high and so it was always desirable to apply low wavelengths of a few centimetres or less. However, short wavelength radar can “see” the target through short, sharp flashes of reflected energy. Because radio waves are on the electromagnetic spectrum, changes in relative velocity between the transmitter and the target will provide a Doppler effect when the reflected component of the signal is received. This can improve the performance of the intercept but to a degree depending on whether this is a passive or an active system. Passive radar send a signal from the tracked object to the receiver while an active signal is propagated from the tracker and reflected back to the receiver. The Doppler computations produce the same result in either case, except that the passive system relies on the tracked object remaining active. Postwar, considerable development took place to make fighters more independent of ground control, allowing them to hunt down enemy aircraft while out of range from their base, or to allow the pilot to make real-time decisions regarding intercept and engagement. The object of radar is to obtain an advantage over the hostile target and the object of stealth is to make the intercepting aircraft less likely to be observed by the enemy, thus maximising surprise and achieving a level of protection from attack by air or by radar-guided AAA or SAM sites.



stealth capabilities of fifth-generation fighters. To reduce the IR signature, the F-117 had a slit-shaped exhaust outlet which reduced the cross-sectional area but increased the expansion volume which could be cooled with air. The swept V-tail is specifically designed to deflect radio waves. Doors, openings and orifices were designed with faceted edges, satisfying the criteria for low RCS and the cockpit itself incorporated several non-reflective technologies, some of which are still classified. Carrying no radar it had some highly innovative, but classified, radar detection equipment located at discreet positions on the exterior surfaces. Designated as a fighter but operated as an attack aircraft, the F-117 lacked the ability to survive long in close-in combat but Lockheed saw potential in the aircraft and proposed it as an upgraded contender for multi-mission roles with both the US and UK air forces and a select few RAF pilots evaluated what was designated the A/F-117X. But the limitations built into the design, so as to maximise the demonstrated stealth qualities, made the aircraft unsuitable for any other purpose and it was retired in 2008. By that time the basic design was more than 30 years old and stealth FIFTH GENERATION FIGHTERS



35







SECTION 2 – CHAPTER 4



ABOVE: The parrot-beak nose of the B-2 is purposely shaped to minimise frontal and side reflections with the aircraft incorporating p g techniques q for varying y g the degree of stealth achieved. (USAF) technology had moved on considerably. Since the mid-1970s, Lockheed had been centre-stage on stealth issues, including radar-absorbing paint, which was applied to sections of the SR-71, to the F-117 and to other classified aero-vehicles which never made it into the public domain. All these, together with radar absorbent materials (RAM) would define the final evolutionary development which matured through the Advanced Technology Bomber (ATB) programme to become the Northrop Grumman B-2 Spirit. Maturing through the expanded research and development programme on general stealth capabilities, the Air Force decided that a stealthy long-range strategic bomber might be feasible and to integrate that with the ATB requirement. Shortly after work got under way, on entering office in 1977 President Carter cancelled the supersonic swing-wing B-1 strategic nuclear bomber in favour of the heavily classified ATB with stealth in a bid to save money. On entering office, in 1981, President Ronald Reagan reopened the B-1 programme and it surfaced as the subsonic B-1B cruise missile carrier. Under the classified Aurora programme, several convergent technologies had been developed through a research programme conducted at Area 51 within the Experimental Survivability Testbed project, essentially the deep-black successor to the ATB programme which had a much lower level of classification. It was recognised at the outset that, after the F-117 programme, low-observables applications would break new ground that would not only make viable large stealthy aircraft but also a range of combat aircraft including fighters capable of penetrating previously prohibited areas. Lockheed and a Northrop/Boeing team competed for a development contract and each proposed a flying-wing concept to all but eliminate flat vertical surfaces. Supporting a small tail however, Lockheed’s Senior Peg design lost out to Northrop’s Senior Ice design in a decision made on October 20, 1981. This time the B-2, as it was soon designated, had a low level of secrecy while the technology itself had a very high level of classification and that remains so 36



FIFTH GENERATION FIGHTERS



ABOVE: The complex, yet visually simple, compounded curvature of the upper surfaces achieves low-observables across a range of measurements covering radar, infra-red and acoustic recognition at BVR, suppressing visual detection within line of sight. (USAF) today for the operational Air Force personnel working on it who go through an intensive and rigorous screening even to approach the aircraft. A significant design change was introduced when the Air Force changed the mission of the B-2 from high-altitude nuclear bomber to a low-level penetration intruder capable of loitering and responding to movements of Soviet road-mobile ICBMs. This had the effect of



changing the configuration of the wing trailing edge and several other aspects but did little to alter the fundamental underlying technologies. In shifting mission roles the LO design elements displayed flexibility which the original faceted approach could never have accommodated. Single-handedly, albeit with Boeing as a co-contractor, Northrop had secured the next generation stealth aircraft which would exploit a completely different approach to stealth, one made possible by advanced computer technology and software unavailable only a few years before. Paradoxically, it would lose out to Lockheed when that company got the contract for the Advanced Technology Fighter, which evolved into the dominant fifth-generation fighter – the F-22A Raptor, and lost a bidding place for the Joint Strike Fighter – which became the F-35. In the wake of this, to consolidate its business, Northrop acquired Grumman in 1994. To get to the stealth imported to the current generation of US fifth-generation fighters, the B-2 programme imported advanced computer-aideddesign (CAD) and computer-aided-manufacturing (CAM) processes which integrated into CAD/ CAM programme methodologies. This was as influential an addition to modern fifth-generation fighter design as the “systems engineering” concept had been when the US military adopted that method in the 1950s and got a 10-year jump on the European aviation industry. While the B-2 was never considered an evolutionary development toward a more flexible means of achieving LO, looking back it was crucial in forging a new synthetic approach. By the time the Aurora programme bled into the B-2, the exotic software programmes and algorithms then becoming available allowed a departure from the flat-panel, serrated-edge, faceted design which resulted in the somewhat clunky-looking F-117. That design was incapable of purposing a multirole fighter of the type which traditionally had been the backbone of tactical air operations. Just as the transistor and then solid-state electronics had opened up a development path for personal computer and cellphone technology, so too did the new CAD/CAM and powerful computer sets employed by the stealth-producing industries give aerodynamicists a greater degree of flexibility that would baseline fifth-generation fighters. The low-drag profile of the flying wing



ABOVE: Front-on, the B-2 displays the air-bleed lip below the engine intakes which sucks in air to cool the engine and exhaust. Note the serrated lip to the intake shroud. (USAF)



ABOVE: With a computerised flight control system, the B-2 crosses over to a new level of aeronautical design for military aircraft in which low-observables can be achieved through full integration of computerised flight controls. (USAF) m material applications were introduced to further ttighten the various sections of the airframe and iinhibit reflective leaks from lines and panels. All these technologies and improvements p placed the industry in a good place when it came to expanding the range of aircraft ttypes to which stealthy design concepts



ABOVE: ABOVE DDisplayed l d at the h Museum M off SScience andd IIndustry d in Chicago, Ch this h representative panel from a B-2 shows the surface texture applied to some areas of the aircraft. (DAVID BAKER) could be applied. Further developments in a new century would underpin the introduction of true fifth-generation fighters.



D I M E N S I O N S O F S T E A LT H



ABOVE: The B-2 has nine flight control surfaces, eight on the wing and a platypus-style flap at the centre trailing edge. (USAF) enhances range while assisting with stealthy characteristics, including optical suppression techniques such as anti-reflective paint, altitude optimisation sensors which tell the pilot when to change altitude for visual blending with the sky, contrail sensors to warn the pilot of imminent tail-trails, also triggering an altitude warning, and some classified active technologies. All of which give the B-2 a maximum visual interception range of 23 miles (37km), usually considerably less depending upon a wide range of atmospheric, weather and altitude variables. The B-2 introduced a series of phasedstealthy states, selectively chosen by the crew in flight according to the mission and the position along the flight path. The real breakthrough in B-2 stealth was the compounded round and curved surfaces in a shape-mapping over the entire wetted area involving continuous curvature. This can involve deflective shaping to send radio waves off in a different direction, or shared reflections, dissipating the strength of the signal by bouncing the reflection from one surface to another until, on the law of inverse-square proportionality, it becomes lost in the noise. As measured in stealth mode, the B-2 has a frontal RCS of 1.1ft² (0.1m²), or -20dBm², which is about that of a human being and 10 times that of a small bird. Traditionally, a conventional aircraft of the size and mass of the B-2 would have an RCS of 107ft² (10m²). Structurally, the B-2 was fabricated from carbongraphite composite material which, while being stronger than steel and having significant radar-absorbing qualities, was lightest of all. As development continued, alternate high-frequency materials were applied to the aircraft to improve its low RCS and automated



The unit of measurement for RCS parameters is the square metre but this does not represent the physical dimensions of the target. When fifth-generation fighters are rated with a specified number this indicates the theoretical value of a spherical metal object which is larger than the comparative wavelength. Clearly, there are a large range of amplitudes impinging upon a target and these are expressed in dBsm, which is decibels relative to one square metre. The quoted value, here and in all literature, is usually the best obtained from a variety of target orientations and attitude positions. The “electrical” size of a target is proportional to the frequency and inversely proportional to the wavelength of the radar and this determines the correct algorithm which must be used to calculate the amount of scattering. Two separate algorithms are used to calculate this for targets less than 5-10 wavelengths and those greater than this value. RCS values vary from type to type and some relaxation is frequently imposed on an aircraft for design, operational or cost considerations. For instance, to save money the F-35 has no radar blocker for the engine exhaust. Direct measurements on a scale show that a typical third-generation fighter such as the F-4 Phantom II has an RCS of 6m² while a first-generation Tomahawk cruise missile applied with first-generation stealth had an RCS of 0.05m². From the front the F-22 Raptor has an



ABOVE: A Boeing E-3 Sentry AWACS on patrol epitomising the evolution of electronic warfare and the development of stealth technology for operating undetected in hostile skies. (USAF)



RCS of -40dBm² which is equivalent to the size of a marble while that of an F-35 is -30dBm², approximating the size of a golf ball. All this computes into survivability by shrinking the effective radius of a ground radar, which may acquire a stealthy target but not get a sufficiently strong lock on to complete an intercept. The US Airborne Warning & Control System (AWACS) aircraft aim to detect aircraft with an RCS of less than 7m² at a range of 230 miles (370km) and stealthy cruise missiles at a range of 67 miles (108km). But non-stealthy missiles could be detected at 141 miles (227km), providing 17 minutes’ warning versus eight minutes to engage a stealthy intruder. Targets with an RCS of