Eurofighter Typhoon

The genesis of the RAF Typhoon lay in the early seventies AST.396 requirement for a STOVL light ground attack fighter intended to replace the Jaguar and Harrier. This requirement was abandoned in favour of the AST.403 specification for a multirole fighter with similar capabilities to the emerging US F-16 and F/A-18. The STOVL requirement soon disappeared since neither Germany nor France saw any such need and they were the most likely teaming partners for a project too big for the UK industry to tackle alone. The objective thus became the replacement of the RAF Jaguar and Phantom FGR.2. With Germany seeking a highly agile F/RF-4F/E replacement, and France seeking a Jaguar replacement, AST.414 was created.

The European Combat Aircraft (ECA) study group was formed, and by 1979 a joint BAe-MBB proposal for the European Combat Fighter (ECF) presented. With Dassault joining the BAe-MBB consortium, a twin engine delta canard was agreed as the preferred configuration. By 1981 the ECF collapsed, since the French wanted a fighter small enough to operate from their aircraft carriers.

Concurrently the national manufacturers worked on their own studies, BAe the P.110, MBB the TKF-90 and Dassault the ACX (which became the Rafale).

In April 1982 a new team was formed comprising the former Panavia Tornado players, and the extant design studies were merged into the Agile Combat Aircraft (ACA). To prove the concepts proposed in the ACA, the UK funded the Experimental Aircraft Program (EAP), the other two governments not coming to the party. Supported by UK government funding and industry funds from all three countries, the EAP first flew in August, 1986. The EAP demonstrator flew until 1991, logging 191.3 hours of total flight time.

European air forces continued to show interest in the idea of a common European design, and in late 1983 a common European requirement for the Future European Fighter Aircraft (FEFA soon changed to EFA) was defined with the UK, France, Germany, Italy and Spain participating. The EFA was to be a highly agile twin engine, single seat fighter with STOL capabilities. Its role was to be BVR counter air combat, short range air superiority over the battlefield, while a respectable strike capability would be provided.

The influences of the period were quite evident. The Soviets were fielding the Su-27S and MiG-29, during what was to be their final surge in the Cold War arms race. Europe's BVR air defences and air superiority hinged on the availability of USAF F-15As based in Germany and Holland, while most European air forces flew the agile but day-VFR F-16A. Germany and Britain flew tired F-4s of various vintages, and France the Mirage F.1 and 2000. The FEFA reflected these pressures, and was clearly intended to provide a smaller and cheaper European BVR capable substitute for the then expensive F-15, in numbers competitive with the F-16, with enough multirole capability to support the dedicated strike assets in any NATO vs Warpac contingency.

It was a European solution to a European scenario. The nearest comparison to the teen series would be an F/A-18 class multirole fighter with the BVR capabilities and agility of an F-15. The USAF replaced their Phantoms with the longer ranging, agile BVR F-15, whereas the USN replaced theirs with smaller and lighter F/A-18, compromising top end BVR performance in favour of numbers and strike capability. The RAF and Luftwaffe, the leaders in the EFA, rolled the equivalent of the USAF and USN Phantom replacements into a single F/A-18 sized airframe.

The question an Australian observer might ask is why not buy a mix of F-15s and F/A-18s off-the-shelf? This would have been unthinkable to the Europeans since they would lose the design expertise and manufacturing base the Eurofighter promised, as well as the massive investment by then sunk into the program, the production base built up for the Panavia Tornado, and concede the future fighter market to the US.

By 1984 the extant divisions between the French and the remaining players surfaced again, over carrier compatibility. The French wanted a 19,000 lb aircraft (between the F-16 and F/A-18) and the British a 24,255 lb aircraft (F/A-18 class empty weight). A compromise 21,000 lb weight was agreed upon. The French also sought design leadership, 50% of total workshare, control of the umbrella company and exports. A schism arose between the French and the other players and the EFA collapsed.

August 1985 saw the UK, Germany and Italy decide to resurrect the program and Spain and France were invited to join. Spain did, France went solo with the Rafale. By June 1986 the Eurofighter Jagdflugzeug GmbH company was formed, and in September 1986, Eurojet Turbo GmbH was formed to design and build the engine. The ECR-90 radar was awarded to GEC Ferranti in the UK.

The RAF EFA requirement was SRA.414, which sought a lightweight twin turbofan BVR and close combat fighter, with a secondary strike capability. The RAF sought 250 aircraft, the Luftwaffe 250, Italy 165 and Spain 100.

The EFA was in trouble again by 1992, under threat from the “peace dividend” expectations of European parliaments. Germany threatened to pull out altogether, after initially chopping numbers to 140, while Italy and Spain reduced the size of their planned buys. After much political bickering, the programme survived with revised build numbers, but serious delays were incurred.

Reports suggest that the F-22 was proposed to the UK, a historical fact which would explain the peculiar fixation on comparing the EFA to the F-22 in much of the marketing literature. The comparison is curious in the sense that the EFA is conceptually an evolution in the teen series fighter paradigm, whereas the F-22 combines sustained supercruising engines and Very Low Observables (stealth), thus representing a completely new paradigm.

The first prototype Eurofighter 2000 DA.1 flew from the DASA Manching facility in March 1994.


The Eurofighter Typhoon - A Technical Summary


The Typhoon employs a combined delta canard configuration with a wing area similar to the F-15, and similar internal fuel capacity, yet the aircraft has an empty weight of around 24,250 lb, much like a late model F/A-18C. The excellent empty weight of the Typhoon in relation to the wing size is as much a result of the compact configuration, as it is of the generous use of carbon fibre composites in the fuselage and wing of the aircraft. Titanium canards and outer control surfaces, and Aluminium Lithium alloy leading edges were employed to minimise weight yet achieve high structural strength.

The combined delta canard configuration and 538 ft2 wing size confer very low wing loading on 50% internal fuel, and are optimised for transonic manoeuvre and supersonic dash performance. The combination of sweep angle and unstable aft CoG is clearly intended for minimising supersonic drag, and is comparable to a classical supersonic interceptor like the Mirage series, but is more modest than the “supercruiser” 72° swept inboard wing section of the F-16XL/E.

The Typhoon is unlikely to match the supersonic high G envelope of F-16XL/E due to a lower wing sweep angle, but will have a useful advantage over most teen/teenski series types optimised for transonic turning. In transonic manoeuvre, the automatic full span leading edge slats are used to adjust the wing camber and therefore reduce the lift induced drag at high G characteristic of classical deltas in this regime. Fuselage vortex generators on either side of the cockpit are employed to promote vortex formation at high AoA and low speeds, and thus increase lift.

The paired inlet is optimised for high AoA performance, using forebody flow to promote air ingestion, as well as a boundary layer splitter above the inlet. The combination of vortex lift and inlet geometry used by the Typhoon exploits the same ideas used in the F-16A/C/XL/E.

The loosely coupled canard is intended to provide high control authority at high angles of attack, by placing the surfaces ahead of the main vortices, but also to provide lower trim drag in supersonic flight.

In comparing the Typhoon to established fighters, the aerodynamic design exploits basic ideas used in F-16 family, but combines them with a strongly swept delta and canard configuration to extend the supersonic envelope, although not as aggressively as GD did with the 660 ft2 cranked arrow F-16XL/E wing. The simpler wing design in the Typhoon in turn required canards to achieve the desired supersonic drag and manoeuvre envelope.

From the perspective of airframe optimisations, the Typhoon is without doubt optimised for its two primary design objectives, which are supersonic BVR interception and close in combat at transonic speeds, with no obvious concessions made to the secondary objective of strike. The low wing loading will confer excellent climb performance for the installed thrust, and the the delta configuration lower supersonic drag, in comparison with the F/A-18. The low wing loading is not optimal for low level strike profiles, but the gust sensitivity will be alleviated by the large sweep angle and the use of artificial stability and canards. The airframe is rated to +9/-3G at an undisclosed combat weight, pylon G ratings have also not been disclosed.

The aircraft is powered by a pair of Eurojet EJ200 afterburning turbofans, rated at 13,500 lbf dry and 20,000 lbf reheated at sea level, which is comparable to growth variants of the F/A-18's GE F404. The 0.4:1 bypass ratio is characteristic of modern fighter engines, and is optimised for transonic performance rather than cruise burn. Eurofighter claim the engine has a supercruise capability, although the duration of possible supercruise has not been disclosed. As the engine is technologically of the same generation as evolved teen series engines, expectations that it can deliver the kind of supercruise performance provided by uniquely designed supercruising powerplants like the US F119 and F120 are difficult to accept.

In an OCA/DCA combat configuration, clean, at 50% internal fuel (~6,500 lb), the Typhoon delivers a nominal sea level dry thrust/weight ratio of 0.82:1 and reheated thrust/weight ratio of 1.22:1 with a wing loading of 60.8 lb/ft2. Both are in the class of the F-15A/C, F-16A/C, MiG-29 and Su-27SK.

The aircraft uses a quadruply redundant digital flight control system intended to provide carefree handling, the latter an advancement over the teen series, and in many respects a necessity given the inherently pitch unstable aerodynamic configuration.

An experienced F/A-18 pilot who flew the Typhoon simulator commented to the author that the aircraft's manoeuvre/handling performance did not appear to be a dramatic improvement over the F/A-18, and rudder authority at high AoA did not match the F/A-18. It is however possible that further refinement of the flight control software could have yielded handling improvements since the mid nineties.

The overall impression resulting from a review of the aircraft's basic configuration, propulsion and fuel package is of a fighter with F-15 class transonic and supersonic agility at optimal weight, instantaneous manoeuvre performance slightly exceeding the teen series, all packaged into an F/A-18 sized airframe with installed thrust comparable to late build F/A-18 models. This reflects very closely the initial EFA design objectives.







The Typhoon's avionic package is built essentially upon the technology base used in the teen series fighters, but employs a higher level of integration against established in service teen series types.

The centrepiece of the avionic package is the X-band (I/J-band) ECR-90 pulse-Doppler multimode radar, similar in concept to the US Raytheon APG-63/65/70 series and derived from the Blue Vixen (Harrier FRS.2). Eurofighter are claiming twice the output power of the F/A-18's APG-65/73 series (typical power output for this class is 10 kW peak), and twice the detection range of the F-16's APG-68. However, in the absence of published data on the ECR-90's mechanically steered planar array aperture size, and peak power ratings, it is impossible to robustly verify these assertions. The radar is frequently credited with a detection range advantage over the F-15's APG-63/70 series, a necessity for the intended use of ramjet BVR missiles with an 80 NMI class A-pole range.

In terms of modes the ECR-90 incorporates the typical package we are familiar with in the teen series, or equivalents. Eurofighter emphasise the rapid slew rate of the planar array.

At this time an active phased array, the AMSAR, is in development as an upgrade to the ECR-90 and the Rafale's RBE2 passive phased array. The AMSAR/ECR-90 is technologically in the same category as the APG-68 ABR (F-16C/B.60) and APG-73 RUG III. It is expected to be available by around 2005, and would provide like the ABR and RUG III improved BVR performance, much lower sidelobes, interleaved search and engagement modes and the potential for interleaved terrain following and ground attack modes. AMSAR offers the potential for LPI operation, but would require further design optimisations and a fundamental redesign of many portions of the ECR-90 back end.

The ECR-90 is supplemented by two passive sensors. The Pilkington Optronics PIRATE mid-wave IRS&T/FLIR can be used for detection, identification and terrain avoidance, with eight discrete operating modes. It is tightly integrated with the radar's functions and either can be slaved to the other. In the absence of aperture and detector size data it is impossible to estimate the effective range under clear sky conditions.

An ESM is integrated into the Defensive Aids SubSystem (DASS), and could be employed as a passive targeting tool in engagements, in addition to its basic function as a sensitive long range RWR. The antenna packages are in the wingtip pods.

The DASS package is comprehensive, incorporating the ESM/RWR, a MAWS, a forward sector Laser Warning Receiver (RAF), expendables, DECM and an optical fibre towed decoy. This is a competitive package by any measure, against its US contemporaries.

The core avionic architecture is based upon the federated model, using multiple Mil-Std-1553B busses, making it comparable technologically to late build teen series systems. Eurofighter claim the use of sensor fusion techniques in the system software, to combine the data produced by the radar, IRS&T and ESM to provide a very high confidence of early BVR target identification and engagement. Given the significantly lower available computing power in the Typhoon, against the F-22A's Cray class CIPs, assertions that this capability is competitive against the sensor fusion software in the F-22A are somewhat peculiar, given that real time sensor fusion is a computationally intensive task.

Eurofighter take much pride in the aircraft's cockpit, which incorporates a holographic HUD, 3 colour MFDs, HOTAS controls, and pilot voice input for selecting system modes. Marconi are developing a HMD, which is intended to provide the pilot with visor projected binocular NVG imagery, FLIR/IRS&T imagery and symbology. On the available data the cockpit is state of the art, and clearly very competitive against teen series equivalents.

Primary navigation reference is provided by a Litton LN-93EF RLG INS, supplemented by GPS and TACAN. A GPWS (ground prox warning) and Microwave Landing System (MLS) are incorporated, the former to aid in low level operations. The aircraft carries secure VHF and UHF comm, an IFF interrogator and a MIDS/JTIS terminal.

For BVR combat the Typhoon's primary weapon will be the Matra-BAe Meteor FMRAAM, a ramjet powered AAM with a radar seeker evolved from the Matra-BAe MICA. The proposal to use the extended range AMRAAM derived ERAAM, or an ramjet AMRAAM derivative, was rejected in favour of a wholly European AAM. The interim BVR weapon will be the US AIM-120B AMRAAM. Most sources credit the FMRAAM with 80 NMI engagement range against a closing target, about 20% better than the ERAAM. The FMRAAM is to outrange the Russian Vympel R-77M ramjet Adder derivative. Four BVR AAMs will be carried in wing root semi-conformal wells.

For close-in combat the RAF Typhoon will be armed with the AIM-132 ASRAAM, soon to be deployed on the RAAF's F/A-18A+ fleet. Non-RAF Typhoons will carry a single Mauser 27 mm cannon, the MoD having decided to delete the gun from RAF aircraft. Weapon interfaces are compatible with standard Sidewinder and AMRAAM interfaces, it is likely the FMRAAM will use the AMRAAM interface.

For strike operations, a range of weapons may be carried. The primary RAF standoff weapon will be the Matra-BAe Storm Shadow cruise missile, derived from the French Apache, the Luftwaffe is likely to stay with the Tornado's KEPD-350. Variants of the Paveway laser guided bomb may be carried, with a TIALD FLIR/laser pod occupying one forward AAM well. For close-in tank busting, the millimetric wave Brimstone (AGM-114F Hellfire derivative) will be used. We can expect to see the Matra-BAe ALARM used for SEAD by the RAF, the AGM-88 HARM by the Luftwaffe. Mil-Std-1760 interfaces are provided as with current build teen series fighters to facilitate the integration of new weapons.

A wide range of options exist for external fuel carriage. For supersonic OCA/DCA combat, around 4,500 lb can be carried in upper wing root Conformal Fuel Tanks (CFT) and around 1,800 lb each in a pair of drop tanks. For subsonic strike sorties, 1,500 L or 2,000 L drop tanks may be carried in addition to CFTs.

Eurofighter marketing literature makes much mileage out of a claimed “stealth” capability, acquired by the use of S-bend inlet tunnels and selective application of radar absorbent materials. The design spec is claimed to have included bounds on RCS performance.

The assertion that the aircraft has a “stealth” capability is curious by any measure, since there is no evidence of planform alignment, panel edge alignment, blending or faceting, all established techniques used and proven on US types such as the F-117A, B-2A, YF-23A, F-22A and the JSF prototypes. Indeed the external carriage of stores alone would make the Typhoon's radar signature at least 10-100 times greater than the golfball to insect sized RCS we are accustomed to with US types. Unless the Europeans have invented new laws of radar scattering, the aircraft is at best a conventional fighter with reduced forward sector RCS, comparable to evolved F/A-18, F-16 variants, the Rafale or the B-1B.

The benefits of such limited RCS reduction are marginal, since the detection range curve is fairly steep in this region and modest increases in opposing radar performance can largely offset any gains in such RCS reduction. While every dBSM down is useful, beyond 0.3 of a square metre the payoff is questionable with external stores being carried. Moreover, unless an LPI radar is carried, the emissions of the radar will betray the fighter to an opponent from well outside radar range.

Published detection range performance for the NIIP N-011M and Phazotron Zhuk-Ph (Su-30MK upgrades) and Agat 9B-1103M/9B-1348E R-77/R-77M seekers would suggest that a Typhoon loaded with external stores could be successfully engaged within the 50-65 NMI envelope. The Meteor ramjet AAM is therefore vital to the Typhoon, since the AMRAAM cannot fully exploit the range
advantage of the BVR weapon system.