Saab 35 Draken

The Saab 35 Draken, a Swedish fighter-interceptor, was developed and manufactured by Svenska Aeroplan Aktiebolaget (SAAB) from 1955 to 1974. This aircraft has an intriguing and storied history, marked by innovation, groundbreaking achievements, and a series of challenges that were overcome with remarkable engineering prowess.

The development of the Saab 35 Draken began in 1948, driven by the Swedish Air Force’s need to replace two other aircraft that were concurrently in development: the Saab 29 Tunnan dayfighter and the Saab 32B Lansen night fighter. The Draken was envisioned as a versatile and advanced interceptor capable of supersonic speeds. One of the most distinctive features of the Draken was its double delta wing, an innovative yet unproven design at the time. To test this new aerodynamic feature, SAAB produced a sub-scale test aircraft known as the Saab 210, which successfully demonstrated the potential of the double delta wing.

The full-scale production version of the Draken entered service with the Swedish Air Force on March 8, 1960. Over its production run, several variants of the Draken were developed, with the fighter-interceptor being the most common. The Draken was notable for several “firsts” in aviation history. It was the first Western European-built combat aircraft with true supersonic capability to enter service and the first fully supersonic aircraft to be deployed in Western Europe. It was also among the first combat aircraft designed with double delta wings, a feature that enabled it to perform the Cobra maneuver, a complex aerial maneuver that involves entering a controlled super stall state and rapidly reducing speed.

Despite its advanced capabilities, the Draken was never used in actual combat. It served as an effective supersonic fighter during the Cold War period and was considered a capable dogfighter for its time, even though it was primarily designed as an interceptor. The Draken underwent several upgrades during its service life, with the J 35J model being the ultimate version. By the mid-1980s, the more advanced JA 37 Viggen had largely replaced the Draken in Swedish service. The introduction of the Saab JAS 39 Gripen was also anticipated, although delayed. Due to budget cuts and high maintenance costs, the Swedish Air Force retired the Draken in December 1999.

The Draken was also exported to the air forces of Austria, Denmark, and Finland. Danish Drakens were later sold to the United States, where they were used as training aircraft for test pilots. The name “Draken,” meaning “The Dragon” or “The Kite” in Swedish, was inspired by the prototype’s appearance, resembling a paper kite when viewed from above. The number “35” in its designation comes from the Swedish Air Force’s system, where “flygplan 35” (fpl 35) means “aeroplane 35.” The prefix “J 35” indicates its role as a “jaktflygplan” (pursuit-aircraft), the Swedish term for a fighter aircraft.

The development of the Draken was driven by the need for a supersonic fighter capable of intercepting bombers at high altitudes and engaging other fighters. In September 1949, the Swedish Air Force released a requirement for an advanced interceptor capable of attacking hostile bombers in the transonic speed range. The initial requirement specified a top speed of Mach 1.4 to 1.5, which was later revised to Mach 1.7 to 1.8, and finally to Mach 2.0 in 1959.

The Draken had to be piloted by a single operator and capable of operating under all weather conditions, day or night, from austere airstrips. It needed to be refueled and rearmed in no more than ten minutes by conscripts with minimal training. SAAB’s design team, led by aircraft engineer Erik Bratt and supported by over 500 technicians, determined that a double delta wing configuration would best meet these requirements. However, this design was untested, leading to the creation of the Saab 210 test aircraft.

The Saab 210, unofficially nicknamed “Lilldraken” (the little dragon), performed its first flight on January 21, 1952. The successful test flights led to an order for three full-size Draken prototypes. The first prototype, without an afterburner, flew on October 25, 1955. An intensive flight test program followed, revealing the aircraft’s exceptional speed, range, and complex systems. The second prototype, equipped with an afterburner, unintentionally broke the sound barrier during its first flight while climbing.

The first operational version, the J 35A, was ordered into production in 1956, with the first production aircraft flying on February 15, 1958. The Draken reached Mach 2 on January 14, 1960, with test pilot Erik Dahlström at the controls of the J 35B prototype. The aircraft was powered by a slightly modified British Rolls-Royce Avon Mk.48A engine, designated RM6BE in Sweden.

The Draken’s design featured a distinctive double delta wing, blending the fuselage and wing into a ‘blended wing-body.’ The fuselage had a circular section, and the inboard portion of the wing extended almost to the engine intakes. The aircraft dispensed with a tailplane, resulting in a clean, simple design. The inner wing’s leading edge was swept back 80° for high-speed performance, while the outer wing was swept back 60° for better low-speed performance.

The cockpit was equipped with mostly Swedish-sourced instrumentation, with various improvements introduced in successive models. Export versions featured a Ferranti-built Airpass II fire-control radar, effective for both air-to-air and air-to-surface targets, along with a ground-mapping mode. The Draken typically had two separate radio units, a high-speed data link, and two navigation systems. A q-feel system generated artificial forces on the stick, and the aircraft was fitted with a three-axis autopilot.

The Draken’s fuselage consisted of two sections, joined by bolts. The forward section housed the fire-control radar, cockpit, nose undercarriage, integral fuel tanks, and various systems. The rear section contained the engine, afterburner, bag-type fuel tanks, armament, main landing gear, and other systems. The flight control surfaces included a rudder and inboard and outboard elevons, with the outer sections fitted with mass-balance weights. Each surface was operated by a tandem hydraulic jack connected to separate circuits.

The aircraft was powered by a single Svenska Flygmotor RM6B/C turbojet engine, a license-built model of the Rolls-Royce Avon 200/300 engine. A ram turbine under the nose provided emergency power, and the engine had a built-in emergency starter unit. The Draken was equipped with a drogue parachute to reduce landing distance. It could carry up to four AIM-9 Sidewinder air-to-air missiles, bombs, rockets, or camera pods for reconnaissance missions. Two 30 mm cannons were also installed within the inboard wing panels, although additional fuel tanks could be fitted in their place.

Despite its advanced design, the Draken encountered problems early in its service life due to the unproven double delta wing configuration. The unstable design made it difficult to land early versions, requiring manual stabilization during landing. The design also allowed the plane to enter a “super stall,” an uncontrollable stall affecting aircraft with specific wing configurations at high angles of attack. To address this, J 35 pilots were trained to prevent super stalls, leading to the development of the Cobra maneuver. This maneuver involved entering a controlled super stall state, gaining high alpha, and quickly negating the angle of attack to counter the stall. This forced the airframe to act as an air brake, rapidly reducing speed.

The Swedish Air Force was the first to discover and develop the Cobra maneuver, initially using it during training to teach pilots how to counter super stalls. It also saw secondary use as a combat maneuver, causing a pursuing enemy fighter to overshoot and allowing the pilot to counterattack.

The Saab 35 Draken’s history is a testament to Swedish innovation and engineering. Despite its challenges, the Draken achieved numerous aviation milestones and served as a highly effective fighter-interceptor during the Cold War. Its legacy continues to be remembered and celebrated in the annals of aviation history.