Saab 29 Tunnan: The Remarkable ‘Flying Barrel’ Fighter Aircraft
The Saab 29 Tunnan was a jet fighter developed by the Swedish aerospace manufacturer Saab AB in the late 1940s. It was developed in response to a concern that Sweden was falling behind other nations in terms of military technology, particularly during the early days of the Cold War with Sweden sitting geographically between East and West.
The Tunnan was the first jet fighter produced by Saab and it was also the first Swedish aircraft to be equipped with an afterburner. Its unusual shape earned it the nickname “Tunnan” meaning barrel.
The Saab 29 also established a number of firsts during its production and military service. Not only did it exceed many of its prototype and design expectations in service, but it also became the first Swedish-built jet fighter to be used in an active combat situation during UN peacekeeping operations in the Congo.
Although Sweden had remained officially neutral during the Second World War, there was a feeling of concern among Swedish military strategists and air force chiefs after the war that the country was falling behind rapidly developing aerospace technology in other nations.
The early days of the Cold War also heightened these concerns as Sweden sat geographically between and close to the Soviet Union and Western NATO powers. Both powers were increasingly devoting time and finances to new military projects in a bid to outdo the other.
Domestically, Saab was also looking for a design to replace the Saab J21 fighter which was a piston-driven aircraft that had been the backbone of the Swedish Air Force.
Saab developed Project JxR to develop a new replacement and incorporate jet technology into the new plane in October 1945 under the management of engineer Lars Brising. The design team under Brising proposed two designs: one was a fixed-wing plane that borrowed engineering elements and looks from the Lockheed P-80 Shooting Star.
The second design featured a barrel shape for the fuselage, which would ultimately evolve into the Saab 29, and this was chosen on the basis that the designers felt it would provide more agility in the air.
Saab was aware that their new plane would have to be fast to hypothetically be able to intercept enemy fighters or bombers that entered Swedish airspace.
In the late 1940s, Saab engineers also began to acquire information and research about swept-wing jet designs conceived in Germany during the war. Saab engineer Frid Wänström collected documents from Messerschmitt engineers who had fled or emigrated to Switzerland after the war detailing their studies into jet technology.
He also recruited German-born aerospace engineer and mathematician Hermann Behrbohm who had worked on experimental wing designs and whose ideas had been incorporated into prototypes such as the Messerschmitt P.1101 jet and the Me 163 Komet rocket plane.
Behrbohm’s research during the war concluded that delta or swept wings reduced an aircraft’s drag significantly. Using Behrbohm’s studies into delta and swept wing concepts, Saab began conceiving designs for the new jet fighter with Behrbohm, Brising and Wänström guiding the project.
Development of the plane began in the late 1940s. Although Sweden had experimented with a previous jet design in the form of the Saab 21R, the Tunnan was the first jet fighter to be produced from scratch in Sweden, since the 21R had essentially been modified from the piston propeller J21.
Speed and agility became the focus of the Tunnan’s development.
To make the wings as thin and as aerodynamic as possible, the design engineers decided the undercarriage would retract into the barrel-shaped fuselage rather than the wings.
Saab also sought to use the British-made de Havilland Goblin turbojet in the design and combined with increased aerodynamics. It was hoped the Tunnan would reach an above Mach speed.
However, the Goblin was superseded by the more powerful de Havilland Ghost engine in 1945. Saab opted to switch the powerplant to the Ghost which could produce a top speed of up to 660 miles per hour. The engine was bolted inside the fuselage but could be removed on a wheeled cart for maintenance.
The Saab 21 was also constructed from a lightweight aluminium alloy after several wind tunnel tests were carried out to perfect streamlining.
In February 1946, the Swedish Air Force requested three prototypes to be put through a performance evaluation and proving flights before any formal orders could be made. The first test was of a static Saab 21 model and conducted in a wind tunnel.
This test revealed some issues with cabin pressure leaking and the performance of the ailerons. Saab rectified this with a new hydraulic system. The jet was also fitted with an afterburner to inject fuel into the aircraft’s exhaust stream in order to increase the thrust and propel the jet to an above Mach speed.
The working prototype of the Saab 29 completed its maiden flight in September 1948 under the control of British test pilot Bob Moore, a former RAF squadron leader who worked for Saab’s UK division. The test notes concluded that despite the unusual look of the plane, it handled well in the air with Moore describing it as an “ugly duckling” that was “a swift” once in the air.
The unusual barrel shape led to the Tunnan nickname being applied during the testing period, and although Saab was not happy with the name, it stuck in popular discourse.
More prototypes were built and fitted with both mockups and real weapons to gauge the realistic weight of the plane. Each test flight found that the Saab 29 exceeded expectations with its speed and performance and production was given the green light by the Swedish Air Force in 1948.
The production model of the Tunnan was given armaments consisting of four Hispano Suiza HS.404 20 mm canons and later air-to-air heat-seeking Sidewinder missiles from the early 1960s onward.
The Saab 21 was also the first Swedish jet fighter to be fitted with an ejector seat for quick evacuation in the event of an emergency and the seat was developed in-house by Saab engineers.
In total, 661 Saab 21 units were produced and to date, this remains the highest number of aircraft produced in Sweden.
Once it entered service, the Saab 29 was noted by pilots for its speed and agility, although this did lead to a number of minor and fatal accidents at first due to unfamiliarity with how a swept wing plane would handle and the lack of training variants to prepare pilots to fly it.
Initially, Swedish pilots were trained in a two-seater British-made de Havilland Vampire jet with straight wings before graduating to solo flights in the faster swept-wing Saab 29. Unfortunately, the higher speed and quick performance of the Saab 21 caught trainee pilots off guard and 99 fighter pilots were killed in training accidents after the jet was first produced.
To make the aircraft easier to control, Saab made small idents known as a “dog tooth” on the wing’s trailing edge.
As pilot familiarity with its handling and controls grew, the Saab 21 proved itself to be effective in combat situations. The Saab 29 set another first by being the first Swedish-built fighter to be deployed into active combat.
In 1961, a squadron of Saab 21s was sent by the Swedish military contingent as part of the United Nations Operation in the Congo peacekeeping force. More Tunnans were sent in the early 1960s as the conflict grew for both combat and observational duties and they became the only UN jet fighter to operate in the war.
The Saab 21 was used extensively in ground strike and light bombing operations during the Congo war often using rockets and unguided missiles. However Swedish pilots sometimes refused to provide strike support to ground troops or attack unarmed enemy aircraft in the air, arguing that the risk of civilian casualties and deaths during what was intended as a peace operation would be too high.
Despite this, both Swedish pilots and international observers deemed the Saab 21 to have incredible abilities and safety. None were lost to enemy fire during the entire conflict.
Once UN forces withdrew from the Congo, many of the Saab 21 units in Africa were sadly dismantled or destroyed by Swedish forces on sight after the Swedish government deemed it too expensive to fly them home and domestically, newer aircraft were starting to replace the Tunnan in fighter capacities.
Internationally, the Saab 21 was authorized for restoration and resale to the Austrian government in 1961. As Sweden officially maintained a code of neutrality, the sale of Swedish-made aircraft and weaponry abroad was often limited.
The Austrian Air Force Tunnans were initially delivered with their cannons removed and they were replaced by camera units for observational duties. The modification allowed the Saab pilot to rotate and move the camera using controls in the cockpit.
In May 1967, the Saab 21 was gradually withdrawn from fighter service in Sweden. By this point, Saab had begun work on the delta wing Saab 35 Draken which set even faster speed records and could achieve supersonic flight.
However, the Swedish Air Force retained many Tunnan models for use as a light bomber, a jet trainer and a target towing aircraft into the 1970s. The last official flight of the Tunnan was performed in 1976 as part of a fiftieth-anniversary celebration of the Swedish Air Force.
Austria retained their Saab 21 fleet from observational duties in 1972 and due to arms limitation treaties, these models were never armed with any missiles.
By the end of its service, the Saab 21 had established itself as an effective aircraft that brought Sweden up to speed with development technology in other countries as well as exceeding test expectations.
- Crew: 1
- Length: 10.23 m (33 ft 7 in)
- Wingspan: 11 m (36 ft 1 in)
- Height: 3.75 m (12 ft 4 in)
- Empty weight: 4,845 kg (10,681 lb)
- Max takeoff weight: 8,375 kg (18,464 lb)
- Powerplant: 1 × Svenska Flygmotor RM2B centrifugal-flow turbojet engine with afterburning, 27.0 kN (6,070 lbf) thrust
- Maximum speed: 1,060 km/h (660 mph, 570 kn)
- Range: 1,100 km (680 mi, 590 nmi)
- Service ceiling: 15,500 m (50,900 ft)
- Rate of climb: 32.1 m/s (6,320 ft/min)