Maturing teens

The different generations of jet fighters are generally defined by advances in aerodynamics, engine technology, radars and other sensors, and weapons. While there is no central authority tasked with describing these generations, most observers broadly agree with the following definitions.

The first generation of jet fighters covered those aircraft introduced at the end of WW2 such as the Me 262, Gloster Meteor and Lockheed P-80 Shooting Star, through the post-war FH-1 Phantom I, MiG-15/17 and NA Sabre. Second generation fighters – such as the first of the US ‘Century series’ of fighters like the F-100 Super Sabre, Grumman F-9F Panther, Hawker Hunter, Dassault’s Mystere series, and the Soviet MiG-19 started to introduce a supersonic dash capability, basic fire control radars, and the first generation of air-to-air missiles.

Third generation fighters added more powerful radars which could provide targeting data for air-to-air missiles and bombing computers, rudimentary electronic warfare systems with chaff and flare countermeasures, the ability to fly at Mach 2, and longer endurance through air-to-air refuelling. Developed at the height of the cold war in the late 1950s and early 1960s, this generation included the F-4 Phantom II, A-6 Intruder, A-7 Corsair and F-8 Crusader, Dassault Mirage III, MiG-21 and 23/27 series, and the Saab Viggen.

It is generally accepted that fourth generation fighters encompassed afterburning turbofan engines, digital flight control systems, advanced radars which could look down and discriminate targets from the ground clutter, beyond visual range air-to-air weapons, the first generation of datalinks, precision weapons such as laser and GPS guided bombs, and a degree of integration between EW, radar and other sensors and communications systems. At first glance, examples of this generation of fighters include all of the US’s teen series fighters, Europe’s Panavia Tornado, Sepecat Jaguar, Saab Gripen and Mirage 2000, and the Soviet MiG-29 and Su-27/30. Further, upgrades to aircraft such as the F-111, Mirage III/Kfir and even the F-4 added fourth generation capabilities to these aircraft.

The success of the F-117 Nighthawk in Iraq in 1991, Kosovo and Bosnia in the late 90s, and – along with the B-2 – Iraq again in 2003 left little doubt that, despite the F-117 relying almost solely on its exotic faceted shaping, built-in low observability was to be the way of the future. As a consequence, most experts place stealth at the top of any fifth generation checklist. It should be stressed that, in this narrow context, stealth is defined as airframe shaping, radar absorbent materials, and passive sensors. Northrop Grumman’s B-2 and YF-23, and the Lockheed Martin F-22 and F-35 all have low observability designed in to their primary structures ‘from the ground up’ in the form of shaping, exotic radar absorbent materials, and systems shielding.

But it’s important to note that, when defining the wider application of stealth, force planners see the aircraft as just one element of a larger system, and that low observability also takes into account how the aircraft and its systems and weapons are employed, what support assets such as airborne electronic attack (AEA) or AEW&C are used, and other factors.

Airborne electronic scanned array (AESA) radars are a key feature of fifth generation fighters. Due to huge advances in processing power and lack of moving parts, AESAs typically enjoy mean-time between failure rates less than one-tenth that of traditional radars with rapidly moving gimballed antennas. Further, the ability of an AESA to simultaneously scan multiple segments of the sky, to track and engage multiple targets in the air or on the surface due to having multiple transmit/receive modules (TRMs), to see targets at range three or more times further away than conventional radars, or even to focus its energy on a single tangent, gives it incredible flexibility and capability.

Another capability commonly associated with fifth generation fighters is that of data-fusion, where the information gathered by an aircraft’s sensors such as radar, electro-optical/infra-red (EO/IR), infra-red search & track (IRST), distributed aperture system (DAS), and electronic warfare systems is fused into a common picture on a single screen, giving the pilot unparalleled and instant situational awareness. All of these systems have been integrally designed into the F-35 JSF, and most are on or are being integrated with the F-22. By comparison, legacy fighters have traditionally carried many of these systems in ‘plug-in’ external pods, and the pilot was required to scroll through a series of pages on a small screen or set up the feed from each sensor on different screens in order to gain situational awareness.

Other commonly defined fifth generation features include internal weapons bays which preserve the aircraft’s low radar cross section, an ability to supercruise – that is, exceed the speed of sound without the aid of afterburners, low probability of intercept (LPI) radars and other sensors which emit few or no ‘side lobe’ emissions, and infra-red suppression shaping or devices in the engine exhaust.

But there has always some blurring of the lines between the generations, with some aircraft featuring capabilities that cross different generations, so it has always been difficult to categorically allocate particular aircraft to a specific generation.

Indeed, it has become even more difficult in recent years, with definitions such as ‘4.5 generation’ becoming more common to cover many new aircraft or capabilities, many legacy derivatives such as the F/A-18E/F Super Hornet and proposed F-15SE Silent Eagle have had some low observable features added to their designs. The effect of enhancements such as engine intake blockers, radar absorbent materials, cerated ‘saw-tooth’ panel and aperture edges, conformal weapons bays and fuel tanks, finer panel gap tolerances and other added-on shaping should not be understated, and can effectively reduce the radar cross-section of an aircraft by several orders of magnitude.

Newer sensors are finding their way onto legacy jets as well. Even though the F-22 featured the first operational AESA, this was closely followed by Boeing’s Block II Super Hornet with its Raytheon AN/APG-79 radar. Further, new AESAs are being retro-fitted to a limited number of USAF F-15C fighters and F-15E Strike Eagles, and are original equipment on Singaporean F-15SGs. In Europe similar systems are being developed for retrofit to the Eurofighter Typhoon, Dassault Rafale and Su-30, while new systems are being developed for the Saab Gripen NG and Su-35 for fielding in the mid 20-teens.

Raytheon and Northrop Grumman are also offering AESA radars for retrofit to the large global fleet of F-16s and ‘classic’ F/A-18s whose operators are being forced to keep these aircraft in service longer due to shrinking defence budgets or delays with the F-35.

And even though the ability to supercruise is a common held fifth generation prerequisite, the F-35 is unlikely to be able to achieve this, and will instead rely on the exceptional situational awareness its pilots will have to avoid trouble. Indeed, many third and fourth generation fighters have demonstrated an ability to supercruise, including the F-111F, MiG-23, later marque F-16s, and the Eurofighter Typhoon, albeit without any external stores.

THE ‘TEEN SERIES’

The ‘teen series’ of fighters were developed in the late 1960s and early 1970s to replace the plethora of US fourth generation fighters which were predicted to be outclassed by the late 70s.

The first of these – Grumman’s F-14 Tomcat – replaced the F-4 in US Navy service, and despite the complexity of its swing-wings, advanced weapons system, and turbofan engines, was without doubt the pre-eminent naval fighter of its generation. The F-14B and F-14D developments of the late 1980s featured more powerful and reliable engines, better electronic warfare suite, digital avionics, and enhanced sensors.

The last F-14s were retired from US Navy service in September 2006 and was replaced by the Boeing F/A-18E/F Block II Super Hornet. About 80 F-14As were delivered to Iran in the mid-1970s, and a small number of these aircraft continue in operation today despite US sanctions. In total, 712 F-14s were built, including 38 F-14Bs and 37 F-14Ds.

The second of the teen series fighters was the McDonnell Douglas F-15 Eagle. The F-15 was the result of the USAF’s F-X program which sought a long range air superiority fighter to replace the F-4 and to counter Soviet long-range bombers and the MiG-25.

With an original ‘not a pound for air-to-ground’ philosophy, the F-15 had a large radar and could carry eight AIM-7 and AIR-9 air-to-air missiles, and had superb manoeuvrability. The original F-15A/B entered USAF service in 1975. Production switched to the upgraded F-15C/D in 1978 which featured more internal fuel, the provision for conformal fuel tanks on the fuselage flanks, a new radar with greater processing power, and a strengthened structure which allowed for 9G manoeuvring at high loads.

Israel also acquired the F-15A/B in 1977, and ordered a follow up buy of C/Ds in the late 1980s, while Japan purchased a large fleet of F-15Js and DJs in the 1980s, most of which were licence built by Mitsubishi. Saudi Arabia also bought F-15C/Ds in the late 1980s.

McDonnell Douglas funded a conceptual development of the F-15 in the early 80s with the multi-role mission but with a strike emphasis in mind. Featuring further strengthening of the aircraft’s structure, conformal fuel tanks, air-to-ground modes for the radar, digital engine controls, podded precision navigation sensors, and the integration of air-to-ground weapons, the two-seat F-15E Strike Eagle was selected by the USAF in 1984.

Israel ordered a version of the Strike Eagle, dubbed F-15I, in 1994, which featured most of the F-15E’s capabilities and a comprehensive Israeli electronic warfare kit and a helmet mounted sight. Around the same time, Saudi Arabia ordered the F-15S which deleted some of the more advanced air-to-ground modes of the APG-70 radar but retained the F-15E’s great range and multi-role capabilities. The Saudi aircraft had their P&W F100 engines replaced by new GE F110 engines from 2008.

The F-15K Slam Eagle is also a variant of the F-15E and was supplied to South Korea from the mid-2000s in response to that country’s F-X requirement. The F-15K has the APG-63(V)2 radar which features the processing capability and other provisions to be upgraded with an AESA TR module face in the future. Singapore has bought the F-15SG which features the APG-63(V)3 AESA, advanced EW systems, Tiger Eye IRST system, GE F110 engines common to its F-16C/D fleet, and other advanced systems.

In 2011, Saudi Arabia signed an order for a batch of advanced F-15SAs which are similar to Singapore’s F-15s, including the AESA and GE F110, but which will also be fitted with an advanced BAE Systems developed EW system. Further, its existing F-15S fleet is to be upgraded to the SA standard as part of the deal.

In total, 1614 production F-15s have been built, comprising 445 F-15A/Bs, 575 C/D models, 176 F-15Js and DJs for Japan, 236 F-15E Strike Eagles, 25 F-15Is for Israel, 61 F-15Ks for South Korea, 72 Saudi F-15Ss, and 24 F-15SGs for Singapore. In addition, Saudi Arabia has ordered 84 F-15SAs, production of which will commence later this year.

Hot on the heels of the F-15 was the Lockheed Martin (nee General Dynamics) F-16 Fighting Falcon or Viper, development of which started in the early 1970s in response to a USAF lightweight fighter (LWF) requirement.

The F-16 was originally intended to be a day air superiority fighter only, with little or no consideration given early on to the air-to-ground mission. The initial F-16A/B was selected ahead of the Northrop YF-17 for the LWF, and entered production in 1976.

While the F-16 product line has been allocated A, B, C, D and E model suffixes, it has also had numerous sub variants which are identified by Block numbers, and one would need a whole separate article to cover all of these. In summary, the F-16A/B was built in Block 1, 5, 10, 15, and 20 versions, each of which added various enhancements. The F-16C/D covered from Block 25, 30, 40, 42, 50 and Block 52, while the F-16E in also known as the Block 60.

As the model line evolved, aerodynamic enhancements were made to areas such as the horizontal stabiliser and air intake. But it is in avionics and propulsion where the F-16 has grown most, with the APG-68 radar with beyond visual range (BVR) AMRAAM air-to-air missile and air-to-surface capabilities being added in the F-16C/D, and dedicated suppression of enemy air defence (SEAD) versions being developed as the F-16CG and CJ variants from Block 40 onwards.

The F-16E Block 60 Desert Falcon was developed specifically for the United Arab Emirates (UAE) – the first of which was delivered in 2002, and features an APG-80 AESA, conformal fuselage fuel tanks, an enhanced EW suite, the ASRAAM air-to-air missile, an integral FLIR/laser seeker, the 144kN (32,500 lb thrust) GE F110-232 engine which produces about 50 per cent more power than the F-16A’s original P&W F100-200 engine, and other enhancements. The Block 60 also formed the basis for Lockheed Martin’s failed F-16IN bid for India’s MMRCA fighter competition in 2011.

The 4,500th F-16 was delivered to Morocco in April 2012, making the F-16 the second most produced western jet fighter after the legendary F-4. In total, 26 countries have ordered more than 4,600 F-16s, while the US, South Korea, Taiwan and other nations are currently studying options to upgrade their F-16s with AESA radars and other enhancements to maintain capability until they are replaced by F-35s or other types next decade.

Last on the teen series was the Boeing (nee McDonnell Douglas) F/A-18 Hornet which entered service with the US Navy in 1978.

The F/A-18 evolved from the Northrop YF-17 which lost out to the YF-16 in the USAF’s LWF competition, but which had greater growth potential due to its larger twin engined design and thus formed a more robust basis for carrier operations. Originally designed to be developed in two versions – the A-18 attack version and F-18 fighter – the two variants were so similar it was decided to incorporate a multi-role capability into the aircraft, hence the ‘F/A’ prefix.

In 1987, the F/A-18A/B gave way to the improved C/D models which incorporated the new APG-73 radar, the AMRAAM missile, enhanced cockpit displays, more powerful GE F404 EPE engines, an enhanced EW system, and a more robust communications suite.

Now called the ‘classic’ Hornet, the F/A-18A-D has been sold to Canada, Australia, Spain, Switzerland, Malaysia, Finland and Kuwait, and a total of 480 F/A-18A/Bs and 773 F/A-18C/Ds were built up to 1999.

In the wake of the cancellation of the US Navy’s A-12 Avenger attack aircraft program in 1991, McDonnell Douglas proposed the F/A-18E/F Super Hornet, cleverly disguising the significantly redesigned variant as an engineering change proposal (ECP) and thus avoiding much of the added scrutiny and restrictions placed on what was essentially a new program.

The Super Hornet was basically a scaled-up F/A-18C/D, featuring many of the same internal systems repackaged into a longer and wider fuselage with a 30 per cent bigger wing area and more powerful GE F414 engines. The Super Hornet also featured a number of signature reduction techniques including finer panel gap tolerances, added radar absorbent materials, cerated panel and aperture edges, and engine fan face blockers which went some way to alleviating the Navy’s disappointment at losing the all-aspect stealth A-12.

The original Block I Super Hornet gave way to the significantly improved Block II in 2005. The Block II introduced the APG-79 AESA, further signature reduction enhancements, greater computer processing power, enhanced cockpit displays and the advanced crew station, a helmet mounted cueing system, and numerous other improvements that had been developed for Boeing’s unsuccessful X-32 JSF contender. The Block II also forms the basis of the EA-18G Growler airborne electronic attack (AEA) aircraft.

A total of 710 Super Hornets have been delivered or are on order, comprising 137 Block I aircraft, 569 Block IIs including 24 for Australia, and 114 EA-18G Growlers. 12 of Australia’s Super Hornets have the F/A-18F+ sub-designation which denotes they have been pre-configured during production for possible future conversion to an EA-18G configuration.

THE 4.5 GENERATION?

With delays to the F-35 program now nearing six years, the F-22 program having been cut off at just 187, and defence budgets worldwide shrinking, both Boeing and Lockheed Martin have proposed advanced versions of their teen series fighters to bridge the gap to the fifth generation, or to offer to allied nations who may have different requirements.

The F-15SE Silent Eagle takes the best of that developed for the Singaporean F-15SG including the AESA radar, GE F110 engines and Tiger Eye IRST, and adds a large single screen cockpit display, a digital fly-by-wire flight control system, canted vertical stabilisers, engine face radar blockers and increased use of radar absorbent materials, and two conformal weapons bays each capable of carrying two air-to-air missiles or one AAM and one JDAM.

Designed to provide a high degree of low observability in the forward and side sectors, the Silent Eagle will not carry any external stores of auxiliary fuel tanks when operating in the first few days of a conflict. But Boeing points out the CWBs can be removed and replaced with CFTs and the aircraft can be reconfigured for external weapons carriage in less than two hours if low observability is no longer a priority.

A conformal weapons bay (CWB) was successfully tested aboard Boeing’s F-15E test aircraft in 2010 when an AMRAAM was launched from the bay. The CWB is similar in profile to the conformal fuel tanks (CFT) carried by the F-15E/I/K/S/SG models, but with the forward half devoted to weapons carriage and the aft only to fuel.

The Silent Eagle has been designed primarily with South Korea’s F-X II requirement in mind, and to this end, Boeing signed an agreement with Korea Aerospace Industries in November 2010 for KAI to design, develop and manufacture the aircraft’s CWBs. This agreement builds upon a previous arrangement with KAI which also produced the wings and forward fuselages for the F-15K and F-15SG.

Lockheed Martin unveiled its proposed 4.5 generation offering at the 2012 Singapore Airshow. Dubbed the F-16V – for Viper – the aircraft will feature a Northrop Grumman SABR or Raytheon’s RACR AESA radar, as well as conformal fuel tanks and other enhancements incorporated into the UAE’s F-16E Block 60 and the F-16IN proposal.

While few details have been released as Lockheed Martin probes the market for interest, the F-16V will likely also feature enhanced mission computers, integral sensors such as IRST and EO/IR FLIR, advanced cockpit displays, an advanced EW suite, and a high degree of integration, but will always be compromised by having to carry its weapons externally.

Possible customers for the F-16V would be those who may not be cleared for export of the F-35, or perhaps those who already operate the F-16 and want a better version of what they are already familiar with. And with 26 operators worldwide, the F-16 customer base is certainly a large one!

Boeing is also gauging market interest for its F/A-18E/F International Roadmap proposal. This variant builds upon the Block II’s high level of integration, and adds enhancements such as a new single screen cockpit display with greater data fusion, additional low observable materials and treatments, an integral IRST and DAS, and a ‘stealthy’ centreline weapons pod which can carry a range of air-to-air and air-to-surface weapons such as AMRAAMs, small diameter bombs, JDAMs, or a mix.

Using Boeing’s evolutionary philosophy, it says the International Roadmap will provide a bridge to its nascent sixth generation FA-XX concept which it expects to begin development of late next decade. When the Block I Super Hornet was developed it utilised many of the systems developed for the late model classic F/A-18C/Ds. The Block II Super Hornet in turn advanced the concept by using many of the fifth generation systems developed for Boeing’s unsuccessful X-32 JSF contender such as the AESA radar, advance crew station and high levels of integration.

The International Roadmap advanced this risk-reduction development model further by combining the fourth generation Super Hornet airframe with even more advanced fifth generation avionics, sensors and other systems. In turn, the company predicts many of the systems being developed for the International Roadmap will flow into the FA-XX. The company says this allows it to develop airframe and systems advances separately, thus amortising the risk over longer periods and model upgrades, instead of developing them concurrently into a whole new airplane.

But all of these advanced proposals may come to nought without a launch customer willing to fund the expected high non-recurring expenses associated with their development. Of the three, the F-16V is probably the less risky as many of the advances have already been funded by the UAE for the Block 60. But with the USAF aiming to phase out its F-16s in favour of the F-35, it is also unlikely that service will be a launch customer for any new F-16 variant. Instead, some elements of the upgrade such as the AESA integration may be funded through upgrade programs for existing aircraft.

Similarly, the F-15SE may never see the light of day in its fully proposed form, with work on the canted tails reportedly being frozen in 2010 due to the development cost and a general lack of interest from possible customers. But with the USAF likely to retain many of its F-15Es well into the 2030s and with an APG-82 AESA retrofit program already underway, it’s possible other Silent Eagle improvements such as the enhanced cockpit display and CWBs may find their way onto these aircraft in the future. The USAF is also planning on retaining some of its F-15Cs much longer than planned after the capping of F-22 production at just 187, and may look to upgrade some of this fleet further too.

And with the US Navy planning to retain some of its F/A-18E/Fs and EA-18Gs into the 2030s, there is a good chance many of the International Roadmap enhancements will find their way into the Navy’s ‘Flightplan’ upgrade schedule in the next few years, and by extrapolation possibly onto Australia’s small fleet of F/A-18Fs as well. The Navy is reportedly very interested in the enhanced cockpit display and the integral DAS proposed for the International Roadmap, and is already developing an IRST which will be mounted in for the forward quarter of the centreline auxiliary fuel tank.