Saab 35 Draken
|Saab 35 Draken|
|A Swedish Air Force SK 35C in flight|
|First flight||25 October 1955|
|Introduction||8 March 1960|
|Status||Retired from military service|
|Primary users||Swedish Air Force|
Austrian Air Force
Finnish Air Force
Royal Danish Air Force
The Saab 35 Draken (IPA: [²drɑːkɛn]; 'The Kite' or 'The Dragon')[Nb 1] was a Swedish fighter aircraft developed and manufactured by Saab between 1955 and 1974. It was the first fully supersonic aircraft to be deployed in Western Europe.
The Draken was developed during the 1940s and 1950s to replace Sweden's first generation of jet-powered fighter aircraft, the Saab J 29 Tunnan and, later, the fighter variant (J 32B) of the Saab 32 Lansen. It featured an innovative double delta wing; in order to test this previously-unexplored aerodynamic feature, a sub-scale test aircraft, the Saab 210, was produced and flown. Developed in Sweden, the Draken was introduced into service with the Swedish Air Force (SAF) on 8 March 1960. Early models were intended purely to perform air defence missions, the type being considered to be a capable dogfighter for the era.
The Draken functioned as an effective supersonic fighter aircraft of the Cold War period. In Swedish service, it underwent several upgrades, the ultimate of these being the J 35J model. By the 1980s, the SAF's Drakens had largely been replaced by the more advanced Saab 37 Viggen fighter, while the introduction of the more capable Saab JAS 39 Gripen fighter was expected in service within a decade, although delayed. As a consequence of cutbacks and high maintenance costs, the SAF opted to retire the Draken during December 1999. The type was also exported to Austria, Denmark, Finland, and the United States; the last operated the type as a training aircraft for test pilots.
As the dawn of the Jet Age arrived, Sweden foresaw that there would be a need for a jet fighter that could intercept bombers at high altitude and also successfully engage fighters. During September 1949, the Swedish Air Force, via the Swedish Defence Material Administration, released its recently formulated requirement for a cutting-edge interceptor aircraft that was envisioned to be capable of attacking hostile bomber aircraft in the transonic speed range. As released, this requirement specified a top speed of Mach speed 1.4 to 1.5; however, during 1956, the specified speed was revised upwards to Mach 1.7-1.8.
Other specified needs were that it had to be flown by a single pilot yet capable of conducting combat operations under all weather conditions or at night while being operated out of relatively austere airstrips while carrying all of the equipment needed to neutralise modern jet bombers. Although other interceptors, such as the US Air Force's F-104 Starfighter, were being conceived during the same period, the new fighter would have to undertake a role unique to Sweden. Specifically, it was required to include the ability to operate from reinforced public roads, which were to be used as part of wartime airbases; the aircraft would also need to be refuelled and rearmed in no greater than ten minutes by conscripts that had minimal training.
In response to the release of the requirement, Swedish aircraft manufacturer SAAB commenced work on producing an aircraft to fulfil the identified role. Preliminary studies had found that the majority of the critical issues which were posed in meeting the requirement could be resolved via the adoption of a delta wing configuration. However, this posed difficulties of its own in that, so that to obtain an aerodynamically desirable location, the forward fuselage would need to be extended and, as a consequence, the aircraft would become unnecessarily heavy. The optimum solution to this conundrum was uncovered in the form of the double delta wing. However, this wing configuration was unexplored quantity, and accordingly, SAAB's design staff on the project, headed by aircraft engineer Erik Bratt and a team of more than 500 technicians, opted to design and construct a small jet aircraft for the purpose of exploring the behaviour of the revolutionary new wing.
This resulted in the only sub-scale test aircraft to be constructed in Sweden, the Saab 210, which was unofficially nicknamed "Lilldraken" (the little kite). The Saab 210, which tested the concept of the double delta wing, performed its first flight on 21 January 1952. The successful results produced by the test flights of the Saab 210 led to an order being placed for three full-size Draken prototypes. On 25 October 1955, the first of these prototypes, which was not fitted with an afterburner, conducted its maiden flight. According to aircraft publication Flight International, an atypically intensive flight test programme was conducted to define and test the type's exceptional speed range and complicated systems. The second prototype, which was equipped with an afterburner, unintentionally broke the sound barrier during its first flight while climbing.[page needed]
During 1956, the first operational version of the Draken, designated as the J 35A, was ordered into quantity production. During February 1958, the first production aircraft performed its first flight.
The Saab 35 Draken is a fighter aircraft, equipped with a distinctive double delta wing. According to Flight International, it is difficult to differentiate between what constituted as the fuselage and what would be defined as being of the wing. The fuselage has a circular section, and the inboard portion of the wing is a large-chord surface which extended aft of the engine intakes; it was possible to dispense with a tailplane, and the overall design is one of relative cleanliness. Draken's design incorporated a distinctive double delta configuration, which featured one delta wing within another larger delta. The leading edge of the inner wing had an 80° angle for high-speed performance, while the outer wing, swept at 60°, provided for good performance at low speeds.
The cockpit of the Draken featured mostly Swedish-sourced instrumentation. Successive models introduced various improvements to the cockpit fittings, such as the revised canopy and new avionics. For export customers, the Draken was outfitted with a Ferranti-built Airpass II fire-control radar, which was effective for acquiring various air-to-air or air-to-surface targets, along with a ground-mapping mode working in conjunction with the aircraft's navigation systems. Typically, two separate radio units would be installed, along with a high-speed data link and two navigation systems. As there is no natural feedback placed upon the stick, artificial forces were generated by a q-feel system. The Draken was also fitted with a three-axis autopilot.
The fuselage of the Draken consisted of two sections, front and rear, joined by bolts. The forward section, which was integral with the intake ducts and neighbouring wing structure, accommodates the fire-control radar, cockpit, nose undercarriage, integral fuel tanks and various systems. The rear portion, which was manufactured as a single piece alongside the rest of the inner wing, contained the engine and afterburner, bag-type fuel tanks, armament, main landing gear, and other systems. The flight control surfaces consisted of a rudder, along with inboard and outboard elevons, the outer sections being fitted with mass-balance weights. Each surface was operated by a tandem hydraulic jack, which was connected to separate circuits. As a weight-saving measure, the hydraulic systems would operate at a line pressure of 210 kp/cm2 (20.590 kPa), which would be greater than double the pressure used in the earlier Saab 29 Tunnan.
Propulsion was provided by a single Svenska Flygmotor RM6B/C turbojet engine, a licence-built model of the Rolls-Royce Avon 200/300 engine. A ram turbine, positioned under the aircraft's nose, provided emergency power, while the engine also featured a built-in emergency starter unit. In order to reduce its landing speed when required, the Draken was equipped with a drogue parachute. The principal armament was carried externally, up to four AIM-9 Sidewinder air-to-air missiles were carried on hard points beneath the wings and fuselage; alternative payloads include a variety of bombs and rockets, along with provisions the installation of a pair of 30 mm cannons, located within each of the inboard wing panels. In place of the cannons, additional fuel tanks could be fitted in the same space. For aerial reconnaissance missions, a variety of camera pods could be carried underneath the fuselage.
At the end of 1959, deliveries of the J 35A Draken commenced to the SAF, the first unit to receive the type being fighter wing F13, stationed at Norrköping. During March 1960, the Drakens of unit F13 participated in a three-day long exercise, flying by night and day while operating under a state of "highest readiness" throughout. According to Flight International, the introduction to service of the J 35A was "very smooth", and that the scramble and turn-round times had been found to be "most satisfactory". By the end of 1960, multiple wings had been equipped with the Draken and had attained operational status.
Although the J 35 Draken was not designed to serve as a dog fighter, it proved to have a good quick-turn capability and was a capable fighter plane. The early models were intended purely to perform the air defense mission. However, in order to assist pilots in converting to the type, Saab produced a small number of twin-seat J 35C trainer aircraft, the first of which having been completed during December 1959. During 1959, an improved air defence fighter model, designated as the J 35B, was developed, which featured improved performance and equipment over the J 35A. Amongst other things, it was powered by an improved engine fitted with an enlarged afterburner, a redesigned rear fuselage, a new Saab-built S.7 collision-course gunsight and fire-control radar, and integration with Sweden's STRIL.60 air defence control network.
A total of 651 Drakens were manufactured by Saab. Sweden's fleet of Drakens comprised a total of six different versions, while two additional models of the Draken were offered to prospective export customers. The final model of the Draken to be produced was the J 35F, which was also the final version to remain in Swedish service. Its export customers included Denmark and Finland. In May 1985, the Austrian Air Force purchased 24 J 35Ds, which had been refurbished by Saab.
The J 35 Draken design underwent several upgrades. The last of these was the J 35J version, which was produced during the late 1980s; by this point, the Draken had been almost entirely replaced by the Saab 37 Viggen in SAF service. The Draken J 35J was effectively a service life extension programme, which had been initiated as a result of the impending delivery of the new Saab JAS 39 Gripen having suffered several delays. The extension program was intended to keep the Draken flying into the 2000s but, as a consequence of budgetary cutbacks and high maintenance costs being incurred with the type, the Draken was phased out of Swedish service in December 1998, although the aircraft has since remained operational in limited numbers within both military and civilian roles.
All Drakens functioned as interceptors with limited air-to-ground capability; the sole exception to this rule was the Danish Drakens, which functioned as strike aircraft and were capable of carrying a mixture of AGM-12 Bullpup air-to-ground missiles, electronic countermeasures, and increased internal and external fuel storage. The Danish Drakens were the heaviest of the series to have flown. During 1993, the last of the Danish J 35 fleet were retired.
During the 1990s, Finland updated its 35XS fleet with new avionics, cockpit displays, navigational/attack systems, and electronic countermeasures; these were finally retired in 2000 to be replaced by F/A-18 Hornets.
Austria was the last country to have the Draken in active military service. The Austrian Air Force bought refurbished J 35Ds. This was the last Austrian Air Force fighter plane fitted with internal cannons to perform their lone air-to-air armament because of the restriction in the Austrian State Treaty of 1955, which had forbade their carrying of air-to-air missiles. During 1993, this restriction was dropped as a response to airspace violations made by neighbouring Yugoslavian air combat services. American AIM-9 Sidewinder missiles were purchased. In 2005, these Drakens were retired, having been replaced by former Swiss Air Force F-5 Tiger IIs, while waiting for new Eurofighter Typhoons to take their place in the long term.
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Proof of concept
- Saab 210 Draken
- Also known as Lilldraken, a scaled-down, proof of concept experimental aircraft to evaluate the double delta wing configuration, not specifically a Draken variant but included here for sequence purposes.
- J 35A
- Fighter version, total production 90 including prototypes. The J 35As were delivered between 1959 and 1961. The tail section was lengthened after the 66th aircraft to house a new afterburner for additional thrust, the longer tail cone unexpectedly reduced drag. This forced the installation of a retractable tail-wheel. The two versions were nicknamed Adam kort (Adam short) and Adam lång (Adam long). The Adam was fitted with a French Cyrano Radar (Swedish designation PS-02) (same as on the Mirage III) as the Swedish radar hadn't been developed in time.
- J 35B
- Fighter version, built and delivered between 1962 and 1963, total production 73. This variant had improved radar and gun sights, and was also fully integrated into the Swedish STRIL 60 system; a combat guidance and air surveillance system. Fitted with a Swedish built radar PS-03.
- SK 35C
- 25 J 35As with short tail sections rebuilt into a twin-seated trainer version. The minor modification meant that the aircraft could easily be converted back to a J 35A standard if necessary. The trainer version lacked armament.
- J 35D
- Fighter version, delivered between 1963 and 1964, total production 120. The aircraft had a new and more powerful Rolls-Royce Avon 300 (RM6C), which could deliver 77.3 kN thrust when using its afterburner. This was also the fastest Draken version, capable of accelerating until out of fuel. It was also the last Draken to carry two cannons. Fitted with the PS-03 radar.
- S 35E
- Reconnaissance version, total production 60 with 32 built from scratch and the remainder converted from the J 35D model. The armament and radar was removed and several cameras (of ortho and oblique types) fitted. The aircraft was unarmed to make room for the nine cameras of Vinten design (five in the nose and four in the fuselage) but was fitted with a countermeasure system to increase its survivability. It also carried an active infrared reconnaissance system of EG&G design in a pod fitted to a hardpoint.
- J 35F
- Fighter version, delivered between 1965 and 1972, total production: 230. This variant had improved electronics and avionics, e.g. integrated radar, aim and missile systems. The aircraft's main armament were IR and SARH versions of the Hughes Falcon missile originally intended for the J 35D, but one of the cannon was removed to make space for more avionics. The J 35F2 was a J 35F, produced with a Hughes N71 Infra-red search and track sensor. This was a change in the production line from the no. 35501 airframe. The Hawé mods I & II where carried out on the P/S-01/011 radar sets in the early 1980s to improve resistance to ECM.
- J 35J
- In 1985 the Swedish government decided to modify 54 J 35F2s to the J 35J standard. In 1987, 12 more modifications were ordered: between 1987 and 1991, the aircraft received a longer lifespan, modernized electronics and cannon, additional two Sidewinder (AIM-9P) pylons under the air intakes and increased external fuel capacity. The final operational J 35J flew for the last time in 1999.
- Saab 35H
- Proposed export version for the Swiss Air Force; none sold or delivered.
- Saab 35XD
- 51 Danish export versions: F-35 single-seat strike aircraft, TF-35 two-seat trainer and RF-35 reconnaissance aircraft. The type was heavily modified to make it into a strike aircraft; compared to the Swedish versions the outer wings where completely redesigned, and the radar was missing. These aircraft could carry heavy bombs as well as Bullpup missiles; during the WDNS upgrade of the 1980s they received the ALQ-162 jammer, a Marconi 900 Series HUD and a Ferranti LRMTS (laser rangefinder and marked target seeker)
- Saab 35XS
- 12 fighter version units for the Finnish Air Force; built by Saab and assembled under licence by Valmet in Finland.  The "S" stood for "Suomi" (Finland).
- Saab 35BS
- Used J 35Bs sold to Finland.
- Saab 35FS
- Used J 35F1s sold to Finland.
- Saab 35CS
- Used SK 35Cs sold to Finland.
- Saab 35Ö
- In the mid-1980s, Saab re-purchased 24 J 35D aircraft from the Swedish Air Force and converted them into the J 35Ö version (also called J 35OE in English literature) for export to Austria. Austria bought AIM-9P5 all aspect Sidewinders for these aircraft during the war in former Yugoslavia.
|J 35B||SK 35C||J 35D||S 35E||J 35F/F-2||J 35J|
|Length||15.207 m (49.89 ft)||15.34 m (50.33 ft)||15.207 m (49.89 ft)||15.34 m (50.33 ft)|
|Wingspan||9.42 m (30.9 ft)|
|Wing area||49.22 m2 (529.8 sq ft)|
|Tail height||3.869 m (12.69 ft)||3.89 m (12.76 ft)|
|Empty weight||6,590 kg (14,500 lb)||6,792 kg (15,000 lb)||7,265 kg (16,000 lb)||7,311 kg (16,100 lb)||7,425 kg (16,400 lb)||7,422 kg (16,400 lb)|
|Maximum take-off weight
|10,089 kg (22,200 lb)||10,189 kg (22,500 lb)||10,508 kg (23,200 lb)||10,089 kg (22,200 lb)||11,864 kg (26,200 lb)||11,973 kg (26,400 lb)||11,914 kg (26,300 lb)||12,430 kg (27,400 lb)|
|Maximum speed||1,900 km/h (1,200 mph)||2,150 km/h (1,340 mph)||Mach 2.0|
|810 m (2,660 ft) dry, or
510 m (1,670 ft) drag chute
|920 m (3,020 ft) dry
680 m (2,230 ft) Drag Chute
|921 m (3,022 ft) dry
678 m (2,224 ft) Drag Chute
|1,220 m (4,000 ft) dry, or |
880 m (2,890 ft) drag chute
|Internal Fuel||2,240 L (590 US gal)||2,820 L (740 US gal)|
525 L (139 US gal)
|Air to air missiles
|Air to air rockets
|Afterburner||Ebk 65||Ebk 66||Ebk 65||Ebk 67|
Before it was decided to develop the JAS 39 Gripen in the 1970s, studies were undertaken on modification for low flight hour J 35F airframes.
- 35 MOD Level 4
- The most ambitious modification in the program. The proposed modifications were new outer wing, additional weapon stations, RBS 15 capability, the addition of canards by the air intakes for increased maneuverability and maximum take-off weight increased to 15 000 kg.
- 35 MOD Level 1b
- Essentially the aircraft that became the J 35J.
The total number of Drakens produced and delivered was 644.
The Saab 35 Draken was withdrawn from military use in 2005. Several aircraft fly in the civilian service, mainly by the National Test Pilot School.
- Austrian Air Force, 24 aircraft:
- Fliegerregiment 2
- Staffel 1
- Staffel 2
- Fliegerregiment 2
|J 35A||J 35B||SK 35C||J 35D||S 35E||J 35F/F2||J 35J|
A small number of Drakens are still with civilian owners mainly in the United States, many former-operational aircraft have been preserved in the operating nations.
Specifications (J 35F Draken)
- Crew: 1
- Length: 15.35 m  (50 ft 4 in)
- Wingspan: 9.42 m  (30 ft 10 in)
- Height: 3.89 m  (12 ft 9 in)
- Wing area: 49.20 m²  (529.6 ft²)
- Empty weight: 7,865 kg (17,340 lb)
- Loaded weight: 11,000 kg  (24,250 lb)
- Max. takeoff weight: 16,000 kg (35,273 lb)
- Powerplant: 1 × Volvo Flygmotor RM6C  afterburning turbojet
- Dry thrust: 56.5 kN (12,787 lbf)
- Thrust with afterburner: 78.4 kN (17,637 lbf)
- Maximum speed: Mach 2.0 (1990s improvements)
- Range: 2,750 km  (1,709 mi) with external drop tanks
- Service ceiling: 20,000 m  (65,600 ft)
- Rate of climb: 199 m/s (39,370 ft/min)
- Wing loading: 231.6 kg/m² (47.4 lb/ft²)
- Thrust/weight: 0.70
- Takeoff roll: 800 m (2,623 ft)
- Guns: 1× or 2× 30 mm M-55 ADEN cannon with 100 rounds per gun (in Saab 35F one cannon was omitted to fit avionics needed for Falcon missile integration, earlier variants and export variants retained twin guns.)
- Hardpoints: for fuel tanks or ordnance with a capacity of 2,900 kg (6,393 lb) and provisions to carry combinations of:
Aircraft of comparable role, configuration and era
- Avro Canada CF-105 Arrow
- Convair F-102 Delta Dagger
- Convair F-106 Delta Dart
- Dassault Mirage III
- English Electric Lightning
- General Dynamics F-16XL
- Lockheed F-104 Starfighter
- Mikoyan-Gurevich MiG-21
- Erichs et al. 1987
- Nilsson, Axel (13 January 2012). "JAS 39 Gripen − Milestones". Projects. Swedish Defence Materiel Administration. Archived from the original on 22 February 2014. Retrieved 12 February 2014.
Swedish naming of aircraft
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- Andersson 1989, p. 126.
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- J 35J, SE: AEF.
- Andersson 1989, p. 134.
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- Peacock, Lindsay. "Saab Draken Variant Briefing". World Air Power Journal, Volume 17, Summer 1994, pp. 116–35. London: Aerospace Publishing. ISBN 1-874023-43-3. ISSN 0959-7050.
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- Eden, Paul (ed.)Modern Military Aircraft Anatomy. London, UK: Amber Books Ltd, 2007. ISBN 978-1-905704-77-4
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