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Saab JA37 Viggen (Thunderbolt)


Supersonic Strike Fighter / Interceptor Aircraft


Aviation / Aerospace

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Image from the United States Department of Defense imagery database.

After 34 years of faithful service to the nation of Sweden, the Saab JA37 Viggen supersonic fighter was replaced by the advanced Saab JAS Gripen multi-role performer in 2005.



Authored By: Staff Writer | Last Edited: 1/2/2018 | Content ©www.MilitaryFactory.com
The Swedish Saab JA 37 "Viggen" ("Thunderbolt") was yet another milestone aircraft design for the Scandinavian nation strictly adhering to a policy of indigenous design, development, and production of its various frontline military weapons. The aircraft - a true multirole fighter for its time- was designed from the outset to be as "battlefield friendly" as possible, capable of utilizing the Swedish network of highways as emergency runways and could further be serviced (refueled and rearmed) by a team of just seven - even with six being conscript-level personnel. To this battlefield survivability was added an advanced onboard computer that negated the need for a second crewman onboard to act as a dedicated radar operator, allowing internal volume to be used on fuel and avionics. Rounding out the requirements was a folding vertical tail fin which decreased the aircraft's side profile and allowed it to be housed in the various underground hangars positioned strategically about the country. If the Soviet Union was to invade, Sweden would have been ready.

The Viggen appeared per a Swedish Air Force requirement to succeed the Saab "Draken" as frontline interceptor/fighter with the inherent strike capabilities of the outgoing Saab 32 "Lansen" series. Work on what would become the Viggen was actually started as early as 1952 and evolved throughout the decade before being approved during December of 1961 by the government. The initial guise was to encompass a strike platform and this model was to be followed by a reconnaissance-minded variant and then an all-weather fighter/interceptor offering with exceptional performance and handling. A prototype first flew on February 8th, 1967 and proved the rather unorthodox design highly sound. The following April, serial production was ordered under the "Viggen" name and introduction occurred on June 21st, 1971.

Like the Saab Draken before it (detailed elsewhere on this site) the Viggen was required to operate from short runways. To help generate the needed lift in short order, the aircraft was given a large-area "canard delta" design wing planform with forward mounted canard foreplanes located to either side of the intake openings. While fixed in place, the canards featured trailing edge flaps and aided both lift and high-speed agility. To this was added a single powerful afterburning turbofan engine - the American Pratt & Whitney JT8D-22 series which powered Boeing 737s. The engine was license-built locally by Volvo Flygmotor as the "RM8" though the afterburner component was of an all-Swedish development. Additionally, the aircraft could be outfitted with rockets for power-assisted take-offs allowing the aircraft to get airborne quickly. Landings were shortened by way of a thrust reverser feature in the engine mated to the nose landing gear leg to work at slowing the aircraft down. The HUD (Head-Up Display) not only served to report pertinent mission details and weapon settings but also assisted the pilot during landings. The undercarriage was reinforced for the abuses of unprepared airstrips with the main legs featuring unique tandem wheels while the nose leg fitted a dual-wheel arrangement - something of a rarity for non-carrier, non-naval fighter aircraft.


The large-area wing surface served to provide six underwing/under fuselage hardpoints for the carrying of air-to-air and air-to-surface ordnance. A single 30mm Oerlikon KCA cannon was fitted for close-in work and allotted 150 rounds of ammunition. A typical weapons load became 2 x RB71 "Skyflash" short-range air-to-air missiles and 4 x AIM-120 AMRAAM medium-range air-to-air missiles.

The RM8 engine outputted at 16,200lbf on dry thrust and 28,110lbf with afterburning. This provided the aircraft with a maximum speed of Mach 2.1 - or 1,385 miles per hour - when running at an altitude of 36,100 feet. Range was out to 1,245 miles and the aircraft sported a service ceiling of 59,100 feet. Rate-of-climb was an impressive 40,025 feet per minute - a good quality for an interceptor-minded airframe.

The initial production version of the Viggen was the AJ 37 which served in the single-seat ground attack role while retaining fighter capabilities. The aircraft were delivered from 1971 onwards and fitted the RM8A engine with Ericsson PS-37/A series radar in the nose. Saab provided the navigation/attack computer hardware and software for this model as well as the HUD system. The SK 37 served as a two-seat trainer and appeared from 1973 onwards while lacking the radar seen in the AJ 37 mount. The SF 37 was a single-seater and used in the photographic-reconnaissance role which saw the radar system in the nose replaced by a battery of cameras. The SH 37 was used for the maritime patrol role with over-water strike capabilities built in. These aircraft appeared from 1975 onwards.

The JA 37 became the definitive (and final) Viggen production form. These were single-seat interceptors retaining their strike capabilities and first appeared in 1979. The model carried the Ericsson PS-46/A "Look Down/Shoot Down" Doppler multimode radar suite supporting missile armament. The RM8B engine was an uprated design and there proved a slight revision of the canard foreplanes. The last of these was delivered during 1990. The JA 37C were JA 37 models upgraded with new flight software and avionics for multirole service. Similarly, the JA 37D, numbering 35 aircraft, were JA 37s upgraded with new avionics and software and some 20 JA 37Ds followed, upgraded to the JA 37DI standard featuring more modern PS-46/A radar systems and AIM-120 missile support. The AJS model line were earlier upgraded (AJ 37, SF 37, and SH 37) Viggens to a new standard that introduced modern avionics and software. The modernization took place from 1993 to 1998 and numbered 86 existing airframes.

There also proved some lesser-known models of the Viggen including the SK 37E which served as an Electronic Warfare Aircraft (EWA) trainer platform. This stock was made up of 10 outgoing SK 37 trainer types and were modified from 1998 into 2000. The Saab 37X was to become an export-minded variant of the mainline JA 37 but the initiative fell to naught. The Saab 37E "Eurofighter" was a proposed interceptor competitor for NATO intended to replace outgoing stocks of Lockheed F-104 Starfighters then in service. This project was not furthered into anything tangible.

Total production of Viggens numbered 329 aircraft, a far cry from the original 800+ once envisioned. Production spanned from 1970 to 1990 and the type gave excellent service that spanned some 34 years of the critical and tumultuous Cold War decades. The product was never exported due to strict exportation rules followed by Sweden but the Saab aircraft served 25 total Swedish Air Force squadrons internally during its long, storied tenure. The line was eventually retired on November 25th, 2005 and succeeded directly by the new Saab "Gripen" multirole, lightweight fighter detailed elsewhere on this site.


Specifications



Year:
1968
Status
Retired, Out-of-Service
Crew
1
[ 329 Units ] :
Saab - Sweden
National flag of Sweden Sweden (retired)
- Fighter
- Interception
- Ground Attack
- Anti-Ship
- Reconnaissance (RECCE)
Length:
51.12 ft (15.58 m)
Width:
34.78 ft (10.6 m)
Height:
19.36 ft (5.9 m)
(Showcased structural dimension values pertain to the Saab JA37 Viggen (Thunderbolt) production model)
Empty Weight:
33,069 lb (15,000 kg)
MTOW:
37,479 lb (17,000 kg)
(Diff: +4,409lb)
(Showcased weight values pertain to the Saab JA37 Viggen (Thunderbolt) production model)
1 x Volvo Flygmotor RM8B afterburning turbofan developing 28,110 lb of thrust.
(Showcased powerplant information pertains to the Saab JA37 Viggen (Thunderbolt) production model)
Max Speed:
1,320 mph (2,125 kph; 1,147 kts)
Service Ceiling:
60,007 feet (18,290 m; 11.36 miles)
Max Range:
1,243 miles (2,000 km; 1,080 nm)
Rate-of-Climb:
32,000 ft/min (9,754 m/min)
(Showcased performance values pertain to the Saab JA37 Viggen (Thunderbolt) production model; Compare this aircraft entry against any other in our database)
STANDARD:
1 x 30mm Oerlikon KCA internal cannon.

OPTIONAL:
Additional mission-specific ordnance across six hardpoints for:

Rb-74 Sidewinder, Rb-71 Sky Flash, or AIM-120 AMRAAM air-to-air missiles, rocket pods, and conventional drop bombs.
(Showcased armament details pertain to the Saab JA37 Viggen (Thunderbolt) production model)
Aircraft System 37 - Initial Developmental Project Model Designation.
AJ 37 - Basic Attack Platform Version Designation.
S 37 - Reconnaissance Variant Designation
JA 37 - All-Weather Fighter Model Designation
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