v1.0.8 / 01 jul 11 / greg goebel / public domain
* Svenska Aeroplan AB (SAAB) of Sweden became well-known in the postwar period for the design of a series of excellent fighters that had long and distinguished service careers. One of the earliest of these fighters was the SAAB J 29 "Tunnan (Barrel)", a portly aircraft that was surprisingly fast and agile. This document provides a short history of the Tunnan.
* The Swedes were thoroughly intimidated by the fall of Denmark and Norway to Hitler in the spring of 1940, since they knew their country could not withstand a German assault. The crisis led to a high-priority effort to improve Sweden's defenses, with a strong emphasis on the development of modern combat aircraft that carried into the postwar period. By the end of the conflict, it was obvious to the engineers of the primary Swedish aviation company, Svenska Aeroplan AB (SAAB), that jet power was the way of the future for combat aircraft. However, Axis and Allied jet development efforts were largely secret, and the Swedes had little knowledge of the technology.
They worked hard to catch up. By the fall of 1945, they were able to get their hands on the British de Havilland Goblin centrifugal-flow turbojet engine, quickly arranging to manufacture it under license. SAAB used the Goblin engine to provide the Flygvapnet (Swedish Air Force) with the first indigenous Swedish jet fighter by fitting the engine to the innovative J 21 pusher-prop fighter -- the "J" stood for "Jakt (Fighter)", by the way -- developed during the war. The first jet-propelled "J 21R" flew in 1947.
The J 21R was a step in the right direction, but it was still well behind the times. As an interim measure, until Swedish industry could provide up-to-date combat aircraft, the Flygvapnet obtained a quantity of British de Havilland Vampire F.1 jet fighters, giving them the designation "J 28A". The first J 28A Vampires reached operational service in 1947.
* In the meantime, SAAB was working on advanced design studies for jet fighter aircraft, beginning with the "RX-1", which was roughly along the lines of the Vampire, and then the "R-101" or "Cigar", which was more along the lines of the American Lockheed P-80 Shooting Star. SAAB engineers had no knowledge of the P-80 when they drew up the R-101 design, and when they found out about the Shooting Star they realized they were lagging developments by several years. They went back to the drawing board.
By October 1945, a SAAB team under Lars Brising had come up with a fighter design study built around the Goblin, featuring the engine stuffed into a fuselage with a straight-in intake in the nose and a straight-out exhaust in the rear, and the pilot perched in the fuselage above the engine under a sliding bubble canopy. The laminar-flow wing was to be very thin, and so the tricycle landing gear had to retract into the fuselage. The resulting fuselage had a fat appearance. The fuselage extended above the exhaust to support the tail assembly, this configuration giving the tail adequate clearance on steep take-offs despite short landing gear.
The Flygvapnet was interested in the design, but then SAAB learned that de Havilland had developed a new centrifugal-flow turbojet named the Ghost that was substantially more powerful than the Goblin. SAAB engineers worked with their de Havilland counterparts and determined that the Ghost would fit into the new fighter design.
During a visit to Switzerland, a SAAB staffer ran across a paper on German swept-wing aerodynamic research data from the war, and brought back to Sweden for Brising and his team to inspect. The design was then modified from the original straight wing to a wing with a sweepback of 25 degrees. The design study of the revised jet fighter concept, with the Ghost engine and swept wing, was complete by early 1946.
The new fighter was expected to have a top speed of 1,000 KPH (620 MPH), and the Flygvapnet became very keen on it. A formal development program was begun in February 1946 under the project designation of "R-1001". Wind tunnel tests were performed, and a SAAB 91A Safir light piston aircraft was fitted with a half-scale version of the 25-degree swept wing for flight tests that began in the spring of 1946. This odd experimental aircraft was designated "Aircraft 201".
* In the fall of 1946, the Flygvapnet ordered three prototypes of the fighter, which was given the designation "J 29". The initial prototype made its first flight on 1 September 1948, with test pilot Robert Moore, a Briton living in Sweden, at the controls. Moore was pleased with the machine, saying: "It was love at first flight. An ugly duckling on the ground, but in the air a swift."
The prototype was powered by a de Havilland Ghost 45 engine, with 19.6 kN (2,000 kgp / 4,400 lbf) thrust. The aircraft had power-boosted ailerons, with leading-edge slats fitted to the outer part of the wings to reduce landing speed. The slats were extended automatically when the flaps were lowered. Performance exceeded expectations, and despite the aircraft's tubby looks, the J 29 proved surprising agile. The first two prototypes were unarmed, but the third was fitted with four Bofors 20 millimeter cannon. The cannon were fitted under the nose intake and had 180 rounds per gun. A fourth prototype was also ordered, flying in 1950.
* The first production version of the "Flygande Tunnan (Flying Barrel)", as it was nicknamed, was the "J 29A". A total of 224 was built from 1951 to 1954, with the type initially entering Flygvapnet service in January 1952. The J 29A was powered by the RM2 Ghost turbojet with 22.3 kN (2,270 kgp / 5,000 lbf) thrust, built under license by Svenska Flygmotor. Trim tabs were added, as well as dive brakes. The dive brakes were mounted on the wings in early J 29A production, but were then moved to the fuselage ahead of the main landing gear doors.
Pilots found the aircraft pleasant to fly, though it did have a few handling quirks under certain circumstances. The Tunnan was very easy to maintain, with 145 service doors, hatches, and ports. Engine changes only took a couple of hours, even given the crudest service facilities. However, an inlet screen had to be implemented after a conscript was sucked into the engine intake and killed.
* The J 29A was followed by the "J 29B", which was fitted with extra fuel tanks in the wings, increasing its fuel capacity by 50%. It also was fitted with stores pylons for bombs and rockets, allowing it to be used in the attack role. For this reason it was also referred to as the "A 29B", where "A" of course stood for "Attack". Possible J 29B underwing loads included:
The initial flight of the J 29B was on 11 March 1953, and 332 were built from 1953 to 1955. The type set a world speed record of 977.35 KPH (607.05 MPH) over a 500 kilometer (310 mile) closed-circuit course in 1954. The Tunnan was a leading-edge fighter by the standards of the time; during a visit to the UK in 1953, a group of Swedish pilots with Tunnans got a chance to take on US Air Force F-86 Sabres, with the two types proving very equivalent in performance. The Tunnan could out-turn the Sabre, but the Sabre could out-loop the Tunnan.
* SAAB was also working on a reconnaissance variant of the Tunnan, the "S 29C", where "S" stood for "Spaning (Reconnaissance)". This version featured a modified nose, with a flat bottom and straight sides, accommodating five cameras of various sorts. The cameras replaced the four cannon. The S 29C also had tail-warning radar, originally mounted in the tailcone but later moved to the fuselage.
Initial flight of the S 29C was on 3 June 1953. 76 were built from 1954 through 1956. While most Tunnans flew in natural metal finish, the S 29Cs generally operated at low level and so were given a disruptive camouflage pattern of dark brown and dark green on the top surfaces. Two S 29Cs set an international speed record of 900.6 KPH (559.4 MPH) over a 1,000 kilometer (621 mile) closed-circuit course in 1955.
Other work proceeding in parallel focused on improving the Tunnan's performance. Svenska Flygmotor developed an afterburning version of the Ghost turbojet, the RM2A, with 27.5 kN (2,800 kgp / 6,175 lbf) afterburning thrust, and this improved engine was fitted to a J 29B for tests. This single modified aircraft was designated "J 29D"; the modification affected its flight qualities, with this aircraft scrapped in 1961.
* In addition, SAAB engineers were refining the wing design to improve the aircraft "critical Mach number", resulting in a new wing with a "dogtooth" leading edge. The leading-edge slats were deleted, but the new wing provided good low-speed handling and the loss of the slats was not noticed. This wing was used on a new Tunnan variant, the "J 29E", with the prototype flying on 3 December 1953. 29 J 29Es were built in 1955. The new wing was also refitted to S 29C reconnaissance aircraft, with no change in designation.
The last variant of the Tunnan was the "J 29F", which featured the afterburning Ghost engine that had been evaluated on the single J 29D and the dogtooth wing developed for the J 29E. The prototype performed its first flight on 20 March 1954, and demonstrated much improved take-off and climb characteristics.
There were no new-production J 29Fs; all J 29Fs were updates of existing
Tunnan fighter variants. The aircraft updated included the single J 29D, 288
J 29Bs, and 19 J 29Es, for a total of 308. In 1963, all J 29Fs remaining in
front-line service were fitted to carry a pair of US-designed AIM-9B
Sidewinder heat-seeking air-to-air missiles, built by SAAB under license as
the "Robot 24" or "Rb24", the "Robot" indicating a guided missile.
SAAB J 29F TUNNAN:
_____________________ _________________ _______________________
spec metric english
_____________________ _________________ _______________________
wingspan 11 meters 36 feet 1 inch
wing area 24.0 sq_meters 258.34 sq_feet
length 10.13 meters 33 feet 2 inches
height 3.75 meters 12 feet 3 inches
empty weight 4,845 kilograms 10,680 pounds
max loaded weight 8,375 kilograms 18,470 pounds
maximum speed 1,060 KPH 660 MPH / 575 KT
service ceiling 15,500 meters 50,850 feet
range 1,100 kilometers 680 MI / 595 NMI
_____________________ _________________ _______________________
* The Tunnan saw action in the Congo in the early 1960s as part of a United
Nations (UN) peacekeeping force. Five J 29Bs were provided to the UN in the
fall of 1961, followed by two S 29Cs and then four more J 29Bs. It is
unclear how much action they saw, but a photo of them does survive of a
number of them "beating up" an airfield with a very low-level pass, leaving
UN peacekeeping troops sprawled on the runway. Four of the eleven were
returned to Sweden in the spring of 1963, with the remainder being destroyed
as a simple means of scrapping them.
The only foreign user of the Tunnan was Austria, which bought 15 J 29Fs in 1961. SAAB tidied them up before delivery, and the Austrians put them to use as fighter-bombers. The Austrians bought 15 more J 29Fs in 1962, with these aircraft modified by AB Svenska Flygvaerkstaederna in Malmoe to accommodate a removeable reconnaissance module. This module could be mounted on the left side of the nose, swapping out the two cannon, and twelve of these modules were delivered. The Tunnan was retired from Austrian service in 1972, being replaced by the SAAB 105. Tunnan sales deals with Israel, Finland, and Yugoslavia fell through.
The Tunnan was out of first-line service with the Flygvapnet by the mid-1960s, with a few used as target tugs and for other second-string tasks into the 1970s, with the very last in service retired in a formal ceremony in 1976. In early 1990s, a group of Tunnan enthusiasts managed to get their hands on a J 29F that had been in storage since 1970. It still had fuel in the tanks. The aircraft, named "Gul [Yellow] Rudolf", returned to flight in 1995 and still puts in appearances at airshows.
* The following table lists Tunnan variants and production:
variant built mods notes
______________________________________________________________________
J 29 4 Initial prototypes.
J 29A 224 Initial production with RM2 Ghost engine.
J 29B 332 Increased wing tankage, stores pylons.
S 29C 76 Unarmed reconnaissance variant.
J 29D - 1 J 29B for afterburning RM2A Ghost trials.
J 29E 29 Dogtooth wing.
J 29F - 308 Dogtooth wing & afterburning RM2A Ghost.
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TOTAL 665
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Some sources give the production as 661, which suggests that J 29 prototypes
were brought up to J 29A status and put into operation. However, details are
lacking.
* In 1950, SAAB generated concepts for the "Sk 29", where "Sk" stood for "Skol (School)", an unarmed two-seat side-by-side trainer version of the Tunnan, and also the "J 29R" single-seat radar-equipped all-weather fighter version with air-intercept radar mounted in a radome above the air intake. Since SAAB was heavily committed to production of the Tunnan fighter variants at the time, the Flygvapnet discouraged the company from pursuing these ideas, and they never happened.
* Sources include:
A few comments from Urban Frederiksson's website were used as well.
* Revision history:
v1.0 / 01 may 01 / gvg
v1.0.1 / 01 may 02 / gvg / Review & polish.
v1.0.2 / 01 jun 04 / gvg / Review & polish.
v1.0.3 / 01 feb 06 / gvg / Review & polish.
v1.0.4 / 01 jun 06 / gvg / Review & polish.
v1.0.5 / 01 aug 06 / gvg / Minor corrections.
v1.0.6 / 01 aug 08 / gvg / Review & polish.
v1.0.7 / 01 jul 10 / gvg / Review & polish.
v1.0.8 / 01 jul 11 / gvg / Review & polish.
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