Compiled by Urban Fredriksson, SAAB 37 VIGGEN, a short history 1993 July 13 Viggen means The Thunderbolt (or maybe it's a small black and white sea bird :-), especially those resulting from the Norse god Thor's warhammer Mjollner. In 1952 studies were started to design a replacement for Saab Draken. "Project 1357" in 1954, was the first to have a canard layout (lots of other layouts were studied as well). In 1961, P&W JT8D-22 was the chosen engine to be locally built, with a locally designed afterburner and lots of material changes in the rest. In 1962 the design was frozen, and the prototype first flew in Feb 8:th 1967. During the 1960's, it was foreseen that the Swedish air force would purchase 800+ Viggens, but the final figure ended up at 329. In order to make the airframe smaller, it was early decided to replace the navigator with a good navigational computer. It's designed to withstand 12 G. Emergency power is supplied by a ram air turbine just before the left wing leading edge, which is always out when the gear is out and will also extend automatically on hydraulic power failure. The canard doesn't contribute much lift in itself during normal flight, it acts more as a gigantic vortex generator for the main wing. During low speed flight, its rear edge flap can be lowered to increase lift and permit a high nose angle. It is maneouvered with the same handle as the landing gear, which has tree positions: Gear and flap up; Gear up, flap down; Gear and flap down. The requirement was that the aircraft would be able to operate from 500 m runways. A short take-off run is possible due to the powerful engine (it used to be the most powerful installed in a fighter). Landing distance is reduced by several means: The HUD is used as a precision landing aid, making it possible to aim just 30 m in from the threshold; The landing gear thinks a landing sink rate of 5 m/s is normal, so landings are done without any flare; The thrust reverser is interconnected with the nose gear link, so it can be selected in the air and will operate when the nose is lowered. (It thus cannot be used in the air.) The aircraft must be servicable very quickly by concripts with short training. Re-fueling and re-arming by 7 men, of which 6 are concripts, is supposed to take less than 10 min. It is said that attack squadrons expect to fly 11 missions per aircraft and 24-hour period. Designations A,Attack = Strike Sk, Skol = Training SF, Spaning-Foto = Reconnaissance: Photo SH, Spaning-Havsovervakning = Reconnaissance: Maritime surveillance J, Jakt = Fighter SWEDISH AIR FORCE VARIANTS designation number delivered in service serial numbers ----- AJ 37 108 1971-? -1998? 37001-37108 This is the strike variant. When it was designed, guns were definitely passe, so there was no provision made for an internal cannon. Dumb bombs weren't popular either, it wasn't until the prototypes were actually in progress of beeing built, that someone thought of incorporating wiring for iron bombs. Main armament is the Saab 304 rocket-powered anti-ship missile. 135 mm rockets in pods is the main area covering weapon. Saab 305, a command controlled missile, with a smoke-less liquid fuel engine was to be the precision ground attack weapon. Now it's used as an allround weapon, as it is rather effective against slow, large aircraft and helicopters too. A TV version was contemplated, but it was cheaper to buy Mavericks instead. It has always had a secondary fighter role, with Sidewinders and 30 mm cannon in pods. ----- Sk 37 17 1973-? - 37081-37817 To make room for the second cockpit, fuel and avionics was removed, so it has a shorter range and lacks a radar. The fin is taller. The trainer version wasn't planned from the outset, as it was considered enough for pilots to learn to fly delta winged aircraft on Draken trainers. ----- SH 37 27 1975-80 -1998? 37901-37927 Long time ago, it was envisioned to have both cameras and radar in the same airframes, but that proved to take up too much space, so The radar has better range than AJ 37, as well as a recorder. A long focal length forward looking SKa 24D-600 is semi- permanently mounted on the right fuselage station, to register what's been seen on the radar. The fuselage pylons look like this As compared to this on the attack on the recce versions and fighter version / \ / \ | | ----- SF 37 28 1977-80 -2005? 37950-37977 All fixed cameras are carried in the nose, that lacks a radar. There are three SKa 24C-120 for horizon-to-horizon coverage, an SKa 24-57 for wide angle pictures and two SKa 31-600 for high altitude or stand off photography. There is also an IR-linescan designated VKA 702. For night photography, a pod is carried on the left fuselage station, with three SKa 34-75 cameras loaded with IR sensitive film in the front. The rear of the pod houses electronic IR flashes, as does a complementary pod on the starboard fuselage station. ----- JA 37 149 1979-90 -2010-15? 37301-37449 By the time this version was in final design, it was clear that guns were definitely useful, so it was given the most powerful cannon a fighter has had, a 30 mm Oerlikon KCA with 150 rounds. Rate of fire is 22.5 0.36 kg rounds/s at 1050 m/s, which gives them six times more kinetic energy than the 30 mm Adens on the attack version. The fighter version has an intertial navigation system instead of the earlier versions' doppler navigation system. It is 13 cm longer, partly because the RM8B engine is 8 cm longer than the RM8A, which is more powerful, better suited to higher altitudes as well as beeing smokeless. There is a three stage fan, three stage LP compressor and a seven stage HP compressor, as compared to 2/4/7 on RM8A. The fin is the same tall one as on Sk 37 to compensate for the longer fuselage. The external tank is the same size as on the other versions, but because there's a bulge where the gun is installed, there is no room for the abbrevited top fin, instead of three fins, this tank has four fins, in a flattened 'X'. The system has gone through numerous upgrades since service entry. The radar is able to track more targets now, for example. A unique feature is the coupling of the radar gunsighting mode to the autopilot. When the pilot places a target in a capture window, the autopilot takes over pitch and yaw, and presents bank information on the HUD for the pilot to follow. Even if it's not followed, the pitch and yaw channels have enough authority to precision aim the cannon, reducing pilot workload letting him or her concentrate on tactics and situational awareness. In spite of having a strengthened wing, an engine 100 kg heavier (2200 kg) and a fixed cannon, it only has an empty weight 400 kg more than earlier versions. In addition to this, it has a maximum take-off weight that is 2000 kg higher (which can hardly be needed, but would have, either for export versions with more internal fuel or the planned strike version derivative). Normal take-off weight is sometimes said to be 16800 kg -- but not by the air force, which for a long time released no weight information except maximum take off for any version. ----- AJS 37 115 1992- -98?/05? rebuilt AJ, SH and SF To take advantage of the weapons already ordered for Gripen, it was decided to modify a number of earlier Viggens, to make them truly multi-role. Not all AJ/SH/SF will be modified, as there will be no life extension involved, and the first AJ 37s will have to be retired starting in 1995. The last Viggens in service will probably be SF 37s, as the reconnaissance pod for Gripen is not expected until after 2000. The modification will be in two stages, the ability to carry AIM-9Ls won't come until 1996. ----- There have been 14 prototypes, of which 5 were rebuilds of other aircraft. One aircraft was lost before delivery, and is not included in the above. ----- | Weapons options. | ____/n\____ _______[(.)]_______ AJ 37 T External tank (1400? litre) R R R R 6 x 135 mm M70 rockets (364 kg) B B B B 16 x 120 kg M63FFV fragmentation bombs I I I I 16 x 80 kg illumination flares 04 04 04 Rb 04E, Saab 304, 620 kg rocket anti-ship missile U22 Erijammer 200 ECM pod (350 kg) (Previously known as KA, for "pod type A") KB BOX-9 chaff/flare dispenser (325 kg) (KB = "pod type B") 75 75 Rb 75 (AGM-65A) Maverick (210 kg) 05 05 Rb 05, Saab 305 command controlled missile (305 kg) usable against ground and slow air targets G G 30 mm Aden cannon with 150 rounds (364 kg) 24 24 Rb 24 (AIM-9B/J) Sidewinder 28 28 Outer wing stations were meant for Rb 28 (AIM-4C), but for some reason they don't seem to have been used (much) ----- Sk 37 Lacks a radar, so its weapons are limited to: T External tank R R R R 6 x 135 mm M70 rockets (364 kg) G G 30 mm Aden cannon with 150 rounds (364 kg) ----- SH 37 T External tank FC Forward looking 600 mm camera in U22 Erijammer 200 ECM pod (350 kg) KB BOX-9 chaff/flare dispenser (325 kg) 24 Rb 24 (AIM-9B/J) Sidewinder C C Port station: 3 IR film cameras, electronic IR flashes in the rear, starboard IR flashes only. 04 04 Rb 04E, 620 kg rocket powered anti-ship missile ----- SF 37 T External tank C C Port station: 3 IR film cameras, electronic IR flashes in the rear, starboard IR flashes only. U22 Erijammer 200 ECM pod (350 kg) KB BOX-9 chaff/flare dispenser (325 kg) 24 24 Rb 24 (AIM-9B/J) Sidewinder ----- JA 37 Built in 30 mm Oerlikon KCA with 150 rounds T External tank, with four fins 24 24 24 24 24 24 Rb 24J (AIM-9J) Sidewinder 74 74 74 74 74 74 Rb 74 (AIM-9L) Sidewinder 71 71 Rb 71 SkyFlash R R R R 6 x 135 mm M70 rockets (364 kg) for ground attack ----- AJS 37 In additions to what they could carry before: 24 24 24 24 24 24 Rb 24J (AIM-9B/J) Sidewinder 74 74 74 74 Rb 74 (AIM-9L) Sidewinder (1996 and later) 15 15 Rb 15F jet powered anti-ship missile (598 kg) BK BK BK BK Bombkapsel m/90, Mjolner. Gliding bomblet dispenser. G G 30 mm Aden cannon with 150 rounds (364 kg) R R R R 6 x 135 mm M70 rockets (364 kg) B B B B 16 x 120 kg M63FFV fragmentation bombs I I I I 16 x 80 kg illumination flares TSA TSA "Heavy guided stand-off weapon" (none selected yet). "Ex AJ 37" AJS 37s will never carry cameras, but may perform radar reconnais- ssance missions. It will also have some weapons the the "ex SH/SF 37s"doesn't: 75 75 75 75 Rb 75 (AGM-65A) Maverick (210 kg) 05 05 05 05 Rb 05, command controlled missile (305 kg) ----- Data AJ/Sk/SH/SF: Empty weight: 11800 kg, Max take off weight: 20500 kg JA: Empty weight: 12200 kg, Max take off weight: 22500 kg AJ/Sk/SH/SF: Engine thrust: 6690 kp; 11790 kp with afterburner JA: Engine thrust: 7350 kp; 12750 kp with afterburner All: Take off run: 400 m, Landing 450 m All: Time from brake release to 10 km or Mach 1 at low altitude: 100 s AJ/Sk/SH/SF: Max speed: Mach 2.0 at high altitude, Mach 1.1 at low altitude JA: Max speed: Mach 2.1 at high altitude. AJ/SH/SF: Length: 16.3 m, Span: 10.6 m, Height: 5.6 m with folded fin 4.0 m JA: Length: 16.43 m, Span: 10.6 m, Height: 5.9 m with folded fin 4.0 m Sk: Length: 16.3 m, Span: 10.6 m, Height: 5.9 m with folded fin 4.0 m -- Urban Fredriksson urf@icl.se