Update – Saab JAS 39 Gripen

Programme History

The Gripen programme resulted from the requirement for a single aircraft type to replace earlier Viggens and Drakens in the Swedish Air Force service. From the very beginning, the fighter was intended to fulfil all three primary missions that were being undertaken by these aircraft in different variants, these being the air-to-air, attack and reconnaissance. These roles would be undertaken by a single model, the ability to undertake all three missions only being influenced by the aircraft’s payload. The requirement also stressed the use of new technologies to reduce the size and complexity of the aircraft, keeping it to roughly half the size and weight of the earlier Viggen. Other stringent demands were applied and it was envisaged that the aircraft would feature considerable improvements over its predecessors in the areas of in the field maintenance, survivability, availability, and low operating costs, while being able to operate from dispersed loc’. ltions throughout Sweden, utilising 800 metre (2625 ft) stretches of freeway.

The development of a totally new airframe was deemed the best way to satisfy Sweden’s defence requirements following the assessment in the early eighties of the F/A-18, F-20, F-16 and Mirage 2000. Despite considerable political opposition to such an ambitious and expensive programme (approximately $US5b in 1982 terms), Swedish government approval for the development of this new generation combat aircraft was granted in May 1982. This gave the go-ahead for Industriegruppen JAS AB-the Gripen industry group headed by Saab, to commence full scale development.

From then on development work continued largely unhindered and the prototype Gripen completed its maiden flight during December 1988. The loss of the prototype in a landing accident attributed to software problems was the only major problem encountered in the programme.

The Gripen Described

The configuration used for the Gripen is that of a close coupled canard delta. This layout was deemed the most suitable, especially in the air-to-air role for which the airframe design is necessarily optimised. The all moving canards offer a number of benefits including increased lift at low speed, essential for the type’s short field performance. Another benefit, and the major reason for its incorporation into a number of new designs is its better lift to drag ratio while manoeuvring. The Gripen design is also laterally unstable and uses digital fly- by-wire which further improves agility. The unconventional flight modes offered by this combination can be used to good effect in air-to-ground attacks and allowing head on air-to-air firings at targets at angles to the aircraft’s flight path.

Air intakes on the Gripen are side mounted, rather than underneath the fuselage which is the currently favoured position suited to high angles of attack operations, possibly to minimise ingestion of water thrown up by the nose wheels.

Much of the mid set wing’s construction features carbon fibre composites. In the construction and design of the wing the Saab relied heavily on British Aerospace’s experience in this field, with BAe being responsible for the torsion box design and the construction of the wings for the first three prototypes. Other areas of composite construction in the Gripen are the canards, fin and undercarriage doors.

An important feature of the JAS 39’s design in fulfilling its stringent Swedish Air Force landing requirements is its undercarriage units. The three heavy duty units are optimised forthe highsinkrates involved with the carrier type flare less landings that will be used to land and stop in the specified 800 metres on major Swedish roadways. Unlike the Viggen which features thrust reversers, the Gripen relies on snow ploughing the canards, extending the rear fuselage air brakes and undercarriage braking to bring the aircraft to a stop in the required distance. It would be fair to suggest that the use of bulky, strengthened undercarriage units, while enabling short landings, incurs some sort of weight penalty compared to conventional units, as well as taking up more internal volume due to its larger size. Certainly the use of a twin wheel nose unit is unusual in an aircraft of its small size. Now under development alongside the single seat fighter is the two seat combat capable conversion trainer. Development of the two seat Gripen, which features a small fuselage stretch and an enlarged canopy, was sanctioned during mid 1992. The design of the trainer will also allow future developments requiring a second crew member to be adopted such as electronic warfare aircraft. First flight is due during 1996.

The heart of the JAS 39 is the Volvo Flygmotor RM12. The RM12 is a derivative of the General Electric F404 turbofan which by now has seen extensive service onboard the F/A-18 Hornet (including those of the RAAF). The engine was chosen ahead of the Pratt & Whitney PW1120 and the Turbo Union RB199 for not only its proven reliability but also its growth potential. The RM12 development has been adapted jointly by both GE and Volvo for the Gripen and has an afterburning thrust of 18,100lb, substantially more than the base F404 at 16,000lb. The Swedish derived engine differs from its American forebear in having an increased fan airflow and a higher turbine inlet temperature. The fans have also been strength- ened to better survive bird strikes.

Progressively more powerful developments of the RM12 are also planned, with an intermediate version of 20,000lb afterburning thrust and an ultimate development rated at 22,000lb.

The key to the Gripen’s multirole capability lies with its advanced avionics and radar, which enables it to engage multiple aircraft at different heights, make pin point precision bombing runs and record, collect and store tactical reconnaissance data.

The Ericsson Ferranti PS-06/A multi mode pulse doppler radar was developed specifically for the Gripen and is the key to the Gripen’s multi role capability. The radar can be used for the demanding roles the aircraft will be employed in by using varied waveforms including high, medium and low pulse repetition frequencies. Radar modes in the air-to-air role include long range target search and tracking, multiple target track while scan, short range wide angle search and track, and automatic gun and missile fire control. In the air-to-ground mission modes include search and track, ground and sea target track while scan, high resolution mapping and air-to-surface ranging. Reflecting 20 years in radar development, the radar is stated as being three times as effective, yet 40% lighter than the radar fitted to the earlier Viggen.

All avionics fitted will give the aircraft multirole capability without modification or the carriage of role specific hardware. This means, as is the case with the F/A-18, that every individual Gripen will be able to undertake attack or fighter missions at any one time, the type of mission flown purely dependent on the aircraft’s payload. Furthermore, also in common with the Hornet, all software is reprogrammable for future requirements.

Interfacing and controlling the radar, cockpit displays and other aircraft systems is the Ericsson SDS 80 computing system. Overall computing power of the aircraft is some 200 times greater than that of the earlier Viggen, again representing the great technological advances of the last two decades. Interestingly the system is said to be capable of a higher rate of work than the MDC F-15E and has a similar sized memory.

Within the cockpit all information is displayed on three CRT head down displays (HDDs). The left unit displays all flight data, replacing conventional flight instruments; there being only back up conventional instruments in the cockpit for emergency use. The central HDD features all known and detected target and battlefield information superimposed on top of a computer generated map of the area in which the aircraft is flying. The right screen meanwhile displays either radar information or a visual representation of data picked up by the Forward Looking Infra Red (FLIR) pod. The cockpit also features a Hughes wide angle Head Up Display (HUD) which presents visual cues for weapons firing and aiming. The pilot sits on a zero-zero ejection seat while the centrally mounted control stick and otherwise conventional flight controls provide inputs for the full authority digital triple redundant fly-by-wire system. Furthermore all critical flight controls and targeting selections are inputted through the HOTAS principle-hands on throttle and stick.

Because of its small size the Gripen will be more reliant on delivering guided munitions rather than carrying high loads of iron bombs. Compatible weapons in the air-to-ground role include the RB75 Maverick ASM, the Saab RB15 anti shipping missile, retarded bombs, rockets and a proposed heavy guided weapon to be developed by the Swedish Defence Material Administration. In addition to weapons, a series of mission pods are under or will be developed for the aircraft. Foremost of these is the above mentioned FLIR pod. This pod will form an integral part of the aircraft for attack and reconnaissance missions, providing targeting information, particularly in poor weather, for weapons guidance and delivery.

For reconnaissance missions, in addition to radar mapping and data collected by the FLIR pod, the Gripen will be able to carry dedicated camera pods and sensors.

In the air-to-air role, primary armament will consist of short and medium range AAMs in addition to the inbuilt 27mm Mauser cannon. For interception and air superiority flights the aircraft will be fitted with wing tip carried Sidewinders, BAe Skyflashes (derived from the Sparrow) and the AIM-120 AMRAAM. A dispute however with the US and Sweden over the fitting and testing of the AMRAAM missile may well see Sweden looking at other alternative weapons in the same performance class.

The Gripen has seven weapon stations, six of which would be used to carry four medium range and two short range missiles. The aircraft is also fitted with electronic counter-measures and a radar warning receiver housed in tail mounted fairings.

Performance Very little performance data has been published on the Gripen, other than to say that the aircraft is supersonic at all altitudes. Other approximate data such as aircraft weights and engine thrust are also known, allowing some scope for surmising the aircraft’s performance parameters. What can be con- cluded from published data on the Gripen is that at combat weight it would possess a thrust to weight ratio of 1. 1 or better, while study of published weight figures yields a maximum payload of around 3500kg.

While there is little published data on the type, some information can be gleaned from a comparison with the similar weightand powered Northrop F-20Tigershark andthe Gripen’s immediate predecessor the Viggen (assuming the Swedish Air Force would not accept an aircraft with markedly inferior performance to the types it will replace). With reserves, two tanks and a 1760kg warload, the Tigershark has a hi-lo-hi ground attack radius of 360nm (667km), while the Viggen has a hi-lo-hi radius with an unpublished payload of 540nm (1000km). The true figure for the Gripen is probably some-where in between these two radii. If anything though these figures are only a rough guide and for attack missions the Gripen will carry precision guided munitions, negating the need to carry high tonnages of dumb bombs.

Similarly, by way of comparison, the F-20 climbs to 40,000ft (15,330m) in 2 min 18s, while the Viggen will climb to 32,800 ft (10,000m) in less than 1 min 40s.

Prospects The Gripen’s potent agility, healthy payload radius, state of the art avionics and radar, and operational flexibility and maintainability makes it, especially considering its small size, a very capable all round fighter ahead of, or at least on par with the very best the world has under development or in-service. Indeed the future for the Gripen would appear to be bright. Current Swedish orders for the type amount to 130 aircraft, including 14 two seaters, out of an eventual requirement for over 300. A highly capable package in a small airframe, the Gripen should also attract considerable interest outside Sweden. While it should be noted that Finland has selected the F/A-18 in preference to the Gripen for its new fighter for operations in essentially very similar conditions (the reasons for the selection are not fully known), the type may well be embraced by a number of air forces replacing their Mirages and F-5s with a modern and capable type later in the decade and early in the next century.

In the past Sweden has been reluctant to export such potent military aircraft due to its non aligned stance, although it has now indicated that the Gripen will be sold to almost anyone who can afford it. If that country can provide a watertight guarantee of back up support, the Gripen, having an attractive unit cost of approximately SEK 150 million ($A32 m) falling between the F-16 and F/A-18, should find considerable acceptance on the international market.

By all indications it appears the Gripen will be a most highly capable and potent fighter. Despite its small size it will be the most advanced fighter in service when imminent (at the time of writing) first deliveries commence, leading the field in manoeuvrability, multirole flexibility and avionics and radar technology, beating its contemporaries into service by a number of years.