Saab Viggen | Plane-Encyclopedia

Sweden (1971)
Multirole Fighter Plane – 329 Built
The Saab Viggen is a single-seat, single-engine fighter with a low double delta wing and with two canards equipped with flaps, intended to replace the Saab J35 Draken. Its first flight took place in 1967. When it entered service in 1971 with the Flygvapnet, the Swedish Air Force, it was the most advanced fighter jet in Europe until the introduction of the Panavia Tornado (1981). It was also the first canard-designed aircraft to be produced in a large quantity.

Development of the Viggen

Development for the Viggen began in 1952, with the development period of 1958 to 1961 being crucial for the airplane, as it was decided to integrate the System 37 as standard arms control. This system would end integrating radar, air-defence screens (Stril 60), and computers, and the Viggen were intended to be the platform for such system. This system made the aircraft extremely advanced in comparison to other designs. Along with the Draken it was the precursor to the advanced datalink system the Gripen would later incorporate. Like most of Swedish designs, it also had short taking-off landing (STOL) capabilities (500 meters), thanks to canards, a thrust reverser – that allowed the aircraft to reverse on the ground, and an afterburner to facilitate short take offs. The engine and the remarkable HUD capability also assisted in landing operations.

Interestingly, it can withstand a force of 12G, but operational limit is 7G. It is also a multirole aircraft. However the multirole ability resides more in a basic airframe giving way to different versions: fighter-bomber, attack, tactical reconnaissance, sea reconnaissance, training, and fighter. Given the specific defence conditions of Sweden, the aircraft was required to be easily maintained and serviced by airmen with little training, within a time of 10 minutes.

329 Viggens were built, and served in the Flygvapnet until 2005. Noteworthy to mention that the Swedish Air Force was the main and only user of the Viggen. Agreements with the United States provided technology enough to increase the performance of an already advanced fighter, making it one of the most advanced during most of its service life.

Design

The Viggen is designed as a low double delta wing fighter, with a single tail and a single engine (A Volvo Turbofan Flygmotor RM8B, the most powerful installed in a jet fighter upon its introduction, achieving a maximum speed of Mach 2. It has canards with flaps that provide lift for both flight and taking-off and landing. Assessed as a very stable platform with good low flight, the canards and the combination of the engine, the thrust reverser, the HUD, and the afterburner allows for STOL capabilities (Taking off: 400 mts/ 1310 ft; landing: 450-500 mts/1640 ft).

The wings were provided with dogtooth at the attack border, in order to improve stability at high incidence angles. The structure was built with aluminium with a honeycomb structure, with the rear being totally of aluminium, allowing the Viggen to withstand the stress of no-flare landings, while the vertical stabilizer, or tail, was made tall given the requirements the large anti-ship missiles existing back then imposed on the design. It has a “hump” on the dorsal area to reduce drag. An interesting feature of the tail is that it can be folded, so to enhance the storage in underground and/or smaller hangars. Earlier version of the Viggen did not have an internal cannon, as it was considered by the days a close-range combat was not necessary, an approach that also affected other designs, such as the American Phantom F4. Further variants incorporated an internal cannon. The pilot seat was angled by 19 degress so to allow the pilot to resist better G forces.

A Cold Warrior with Digital Features

The Viggen was intended to be a single pilot fighter, making the introduction of advanced avionics a requirement as there would be no navigator. As a result, the Viggen incorporated the CK 37 (Centralkalkylator) computer, the first airborne computer with integrated circuits, and that even remained in service with the Flygvapnet fleet of Viggens until the early years of the 21^st century. During the development of the Viggen’s electronic components, operational aspects like vibration, exposure to strong forces and even crashes were considered, resulting in a very strong computer with a strong hardware capable of resisting crashes while keeping valuable information of the aircraft. It was also a very valuable computer for the Viggen, as it was able for assisting the pilot and aircraft missions and control of the aircraft.

Another important avionics element of the Viggen, working in tandem with the integrated computers, was the radar, an Ericsson PS-37 X radar. This radar was able to perform air-to-ground and air-to-air telemetry, search, track, terrain avoidance and cartography tasks. The further versions of the Viggen received enhanced avionics and electronic/digital components, enhancing their capabilities and mission performance.

Guardian of Neutrality

The Viggen is a pure product of the times it was designed and the context in which Sweden was a neutral country forced to increase its military power in order to safeguard its neutrality during the heated days of the Cold War. As Sweden was a close neighbor to the Soviet Union, many incidents between the two nations took place. Those incidents prompted Sweden to have an alert service, with round-the-clock radar surveillance, fighters and attackers on high readiness for combat, among other measures. The design therefore was intended to meet the defence needs of Sweden and the missions of the Flygvapnet.

A first requirement was for the Viggen to have STOL capabilities, so to be able to operate from damaged runways – or runways and highways – and also from secondary airfields. The aim of such operational conditions was to increase the survival of air assets and to difficult the destruction, blocking or dispersion of such assets by an aggressor. A second requirement was the Viggen to be serviced, refuelled and rearmed in less than ten minutes by untrained personnel. This, considering that Sweden’s particular defence conditions required small and dispersed air and field bases, having little personnel and facilities. In fact, and thanks to this system, the Viggen was able to execute up to 11 sorties within a period of 24 hours. In addition, the Viggen became the main asset of Swedish air defence, intercepting, patrolling, and monitoring Soviet and Western activities and flights. This explains the multi-role capacities of the Viggen, or at least to have served as a basis for different versions using the same airframe. It also allowed Sweden to demonstrate its readiness. During the S-137 Soviet submarine incident, the submarine ran aground on the Swedish archipelago and Soviet surface vessels closed in on the Swedish coast to attempt a rescue, armed Viggens were put into the air so to ward-off the Soviets. Also, with the routine of the American SR 71 Blackbird path known, the Viggen was able to get radar-lock on the SR71 despite the jamming measures of the reconnaissance plane and thanks to coordination with ground-based radars. It is the only aircraft that managed to lock onto the SR 71.

Variants

AJ 37 – An all-weather attack aircraft with air-to-air secondary capacity. Considered outdated, it lacked a gun, but had increased bombing precision thank to its HUD and Weapons Aiming Computer System. Armed with rockets and iron bombs for strike missions, and Saab 305/Rb 05 or Sidewinders and 30mm cannon pods for air-to-air. It also had anti-ship capabilities thanks to the Saab 304 anti-ship missile. 108 delivered.
Sk 37 – Training version, with a second cockpit and the avionics and fuel removed, also lacking a radar array. It had instead of the internal fuel tank, a permanent fuel tank under the belly. It also had a shorter range. The second cockpit has two periscopes to provide forward view. It was tasked with providing pilots conversion and supersonic training. It also had secondary combat capacities. 10 were converted to electronic warfare trainers (SK 37E). 17 delivered.
SF 37 – All-weather reconnaissance version and intended to substitute the S35E. The nose had a peculiar form thanks to the fact that the recce equipment was placed there, with seven cameras. On the hardpoints further reconnaissance equipment was placed. One camera can take infrared pictures, two vertical cameras can take shots for high-altitude, and four cameras for low-altitude shots. It had the same armament as of the JA 37 interceptor version yet lacking of radar. 28 delivered.
SH 37 – Single seat version fitted for sea surveillance and attack/anti-ship roles, armed usually with the Saab 305 anti-ship missile and other ground-attack weaponry. It could also carry Sidewinder missiles for self-defence. 28 delivered.
JA 37 Jaktviggen – All-weather interceptor version of the Viggen, powered with a Flygmotor RM8B. Incorporated an internal 30 mm Oerlikon cannon, and could operate AMRAAM, Sidewinder or Rb71 Sky Flash missiles. Armed also with radar and infrared homing missiles. It also had upgraded avionics, such as a long-range Ericsson UAP-1023 pulse Doppler radar, enhancing target acquisition, and new computers that enhanced as well the aircraft performance. In fact, there is a coupling of radar gunsighting with the autopilot, presenting a lock information to the pilot’s HUD while increasing the cannon lock thus reducing the workload for the pilot. It also had an inertial navigation system. Furthermore, it provides tracking for land, air and sea-borne targets while resisting to ECM attacks. Some were upgraded with airframes, avionics and software modified for international duties (JA 37C, JA37D, and JA37DI) 149 delivered.
Saab 37 Eurofighter – Proposed replacement for NATO F-104 Starfighter. None built.
Saab 37 X – Proposed version to be exported to Norway. None built.

Operators

Sweden – The Flygvapnet has 329 Viggens, 108 of which are AJ 37, 17 were Sk 37, 28 were SF 39, 28 were SH 37, and 149 were JA 37.

Viggen Specifications
Wingspan	10.6 m / 34 ft 9 in
Length	16.40 m / 53 ft 9 in
Height	5.6 m / 18 ft 4 in
Wing Area	46 m² / 500 ft²
Engine	1 Volvo Flygmotor Turbofan RM8
Maximum Take-Off Weight	20,500 Kg / 45,194 lb
Empty Weight	11,800 kg / 26,014 lb
Loaded Weight	16,000 kg / 35,273 lb
Maximum Speed	2,125 km/h / 1,320 mph
Range	2000 Km / 1,242 miles
Maximum Service Ceiling	18,000 m /59,100 ft
Climb Rate	203 m/s ( 12,000 m/min / 40,026 ft/min )
Crew	1 (pilot)
Armament	• 1 Oerlikon KCA 30mm cannon (JA 37) • 7 hardpoints that could allow 6000 kg of payload. A pod for Aden 30 mm cannon; 135mm Bofors M70 rockets in pods for six rockets; air-to-air Saab 305/Rb 05, Rb71 Sky Flash, AMRAAM or Sidewinder missiles; air-to-surface or Maverick missiles; Anti-ship Saab 304; 120 kg iron bombs.

Fighter Pilots and Fighter Jets

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