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ⓘ Saab 29 Tunnan




Saab 29 Tunnan
                                     

ⓘ Saab 29 Tunnan

The Saab 29, colloquially called Flygande tunnan, is a Swedish fighter that was designed and manufactured by Saab in the 1940s. It was Swedens second turbojet-powered combat aircraft, the first having been the Saab 21R; additionally, it was the first Western European fighter to be produced with a swept wing after the Second World War, the Me 262 having been the first during the war. Despite its rotund appearance, from which its name derives, the J 29 was a fast and agile aircraft for its era. It served effectively in both fighter and fighter-bomber roles into the 1970s.

                                     

1. Development

In the aftermath of the Second World War, Sweden required a strong air defence utilising the newly developed jet propulsion technology. According to aviation author Bo Widfeldt, there was a perception that Sweden had not kept up with wartime innovations and technical progress, and that Saab was eager to make aeronautic advances, particularly in terms of developing jet propulsion. Accordingly, project "JxR" was initiated in the final months of 1945, leading to the requirements being drawn up in October 1945. This led to a pair of proposals being issued by the Saab design team, led by Lars Brising. The first of these, codenamed R101, was a cigar-shaped aircraft which bore a resemblance to the American Lockheed P-80 Shooting Star. The second design, which was later picked as the winner, was the barrel-shaped design, codenamed R 1001, which proved to be both faster and more agile upon closer study.

The original R 1001 concept had been designed around a mostly straight wing, but after Swedish engineers had obtained German research data on swept-wing designs, the prototype was altered to incorporate a 25 degree sweep. Information on swept-wings came from Switzerland and included drawings on Messerschmitts Messerschmitt P.1101, Messerschmitt P.1110, Messerschmitt P.1111 and Messerschmitt P.1112. SAABs project manager Frid Wanstrom retrieved these secret papers from Switzerland to Sweden in 1945. The documents came from engineers from Messerschmitt who fled to Switzerland at the end of the Second World War. Among them were the engineer and aerodynamicist Hermann Behrbohm, who came to be part of Saabs core in the team around J29 and upcoming aircraft types. These files had clearly indicated delta and swept-wing designs to have the effect of "reducing drag dramatically as the aircraft approached the sound barrier." In order to make the wing as thin as possible, Saab elected to locate the retractable undercarriage upon the aircrafts fuselage rather than upon the wings.

Extensive wind tunnel testing performed at the Swedish Royal University of Technology and by the National Aeronautical Research Institute had also influenced aspects of the aircrafts aerodynamics, such as stability and trim across the aircrafts speed range. These tests had determined the required slenderness of the fuselage in order to ensure compatibility with the targeted critical Mach number, as well as supporting the use of a straight-through airflow system to ensure the maximum attainable thrust, in addition to the advantages of its ease of development. For the reason of lateral stability during take-off and landing, automatically-locking leading edge slots, which were interconnected with the flaps, were also deemed necessary. In order to further test the design of the swept wing, it was decided to modify a single Saab Safir, which received the designation Saab 201, with a full-scale wing for a series of flight tests. The first final sketches of the aircraft, incorporating the new information, was drawn in January 1946.

The originally envisioned powerplant for the type was the de Havilland Goblin turbojet engine. However, in December 1945, information on the newer and more powerful de Havilland Ghost engine became available. This was deemed to be ideal for Saabs in-development aircraft as not only did the Ghost engine have provisions for the use of a central circular air intake, the overall diameter of the engine was favourable for the planned fuselage dimensions; thus, following negotiations between de Havilland and Saab, the Ghost engine was selected to power the type instead.

Despite early doubts over the availability of a suitable aluminium alloy, similar to the American 75S alloy, Svenska Metallverken was able to manufacture the sufficient grade of sheet metal, equivalent in strength to its US-based counterpart, albeit requiring the use of significantly larger sections than had typically been employed in aircraft construction. The structure employed a complicated mixture of stressed skin and heavy frames in order to meet conflicting requirements on space, strength, rigidity and accessibility.

By February 1946, the main outline of the proposed aircraft had been clearly defined, and the Swedish Air Force requested that work commence to verify the performance particulars and provide solutions for essential production queries on the project. In Autumn 1946, following the resolution of all major questions of principal and the completion of the project specification, the Swedish Air Force formally ordered the completion of the design and that three prototype aircraft be produced, giving the proposed type the designation J 29.

Some problems were encountered during the static testing of a full-scale experimental mock-up of the front portion of the aircraft, including leaks within the experimental pressure cabin and concerns regarding the behavior of the ailerons, leading to a hydraulic system being installed to solve the latter issue. However, faults were encountered with the aileron servomotors which delayed the first flight of the first prototype, which had been originally intended to take place prior to 1 August 1948.

On 1 September 1948, the first of the Saab 29 prototypes conducted its maiden flight, which lasted for half an hour. The test pilot for this first flight of the type was an Englishman, S/L Robert A. Bob Moore, DFC and bar, who subsequently went on to become the first managing director of Saab GB Ltd, UK, set up in 1960. Following the flight, Moore described the aircraft as being: "on the ground an ugly duckling – in the air, a swift." Because of the shape of its fuselage, the Saab J 29 quickly received the nickname "Flygande Tunnan" "The Flying Barrel", or "Tunnan" "The Barrel" for short. While the demeaning nickname was not appreciated by SAAB, its shortform was eventually officially adopted.

A total of four prototypes were built for the aircrafts test program. The first two lacked armaments, carrying heavy test equipment in their place instead; while the third prototype was armed with four 20mm automatic guns. Various different aerodynamic arrangements were tested, such as air brakes being installed either upon the fuselage or on the wings aft of the rear spar; along with both combined and conventional aileron/flap arrangements. The flight test program revealed that the J 29 prototypes were capable of reaching and exceeding the maximum permissible Mach number for which they had been designed; the flight performance figures gathered were found to be typically in excess of the predicted values.

In 1948, production of the type commenced; in May 1951, initial operational deliveries of production aircraft were received by Bråvalla Air Force Wing F 13. The Tunnan was produced in five principal variants, these being the J 29A the first model to enter service, J 29B and J 29E for the fighter mission, the S 29C for the reconnaissance mission, and the afterburner-equipped J 29F fighter, which was the final variant. From 1950 to 1956, at which point manufacturing was terminated, a total of 661 Tunnans were completed, making it the largest production run for any Saab aircraft.

                                     

2. Design

The Saab 29 Tunnan is a first-generation jet fighter, possessing the distinction of being the first Swedish aircraft to be specifically designed to use jet propulsion. Visually, it was a small, chubby aircraft featuring an integral single central air intake forming the aircrafts nose, the pilot being housed within a bubble canopy located directly above the air intake on the upper-forward section of the fuselage, and a very thin mid-mounted swept-back wing. The two-spar wing is a single piece structure attached to the fuselage by four bolts. The undercarriage was hydraulically retracted during flight and was designed to be suitable for landing upon rough grass airstrips.

The Tunnan was equipped with a single de Havilland Ghost turbojet engine, capable of generating up to 5.000lb of thrust. It was capable of powering the aircraft to speeds in excess of 650 MPH, and reportedly provided performance in excess of Swedens existing de Havilland Vampire fleet. The engine was attached to the fuselage at three key points, while the engine cowling could be removed as a single piece; a special trolley was used to remove the engine for maintenance. To improve pilot survivability in light of the aircrafts high speeds, the Tunnan took advantage of the availability of a Saab-developed ejector seat developed in 1943, which was combined with an explosive jettison system for the rapid removal of the canopy.

Later versions of the Tunnan received various refinements, including the addition of an afterburner, which was the first successful use of such a device in combination with a British jet engine. Improvements were made to the wing shape, incorporating a dog-tooth leading edge, for the effect of raising the critical Mach number of the aircraft. From 1963 onwards, all frontline J 29Fs were equipped with AIM-9 Sidewinder infrared-seeking air-to-air missiles.

                                     

3.1. Operational history Sweden

The J 29 was one of the first production fighters with a swept-back wing, being the first Western European fighter to be introduced with such a wing configuration. It was fast and agile, and set the world speed record on a 500 km 310 mi closed circuit in 1954 at 977 km/h 607.05 mph. Two S 29C reconnaissance variant additionally set an international speed record of 900.6 km/h 559.4 mph over a 1.000 km 620 mi closed-circuit course in 1955.

The crash record in early service was poor, mainly due to the inexperience with swept-winged aircraft and the lack of a two-seat, dual control Tunnan trainer variant: this meant that Swedish fighter pilots could only be trained using two seat variants of the de Havilland Vampire a straight-winged jet, before going solo in a Tunnan. 99 pilots were killed during military practice flights in Sweden.

In May 1967, the fighter versions of the Tunnan was retired from combat service; however, a number of aircraft were retained and reconfigured for use as countermeasures trainers and for target towing duties into the 1970s. In August 1976, the last official military flight was performed at the Swedish Air Forces 50th anniversary air show.



                                     

3.2. Operational history Austria

On 27 January 1961, the Swedish Government granted the Air Board permission to sell 15 J 29F Tunnans to Saab for restoration and resale to the Austrian Air Force. In 1962, government approval for the sale of a further 15 J 29F aircraft to Austria was granted. This second batch received modifications in order that a specialized camera pod could be installed in the port side of the nose of each aircraft, requiring the removal of the two nose-mounted cannons to accommodate this. This interchangeable camera pod, the cameras of which could be moved in-flight via controls installed in the cockpit, took roughly 30 minutes to exchange. Due to limitations imposed by the Austrian State Treaty of 1955, these aircraft were never armed with air-to-air missiles. The Tunnan remained in service with the Austrian Air Force until 1972.

                                     

3.3. Operational history Combat service in the Congo

The Tunnan was the first Swedish jet aircraft to perform combat operations. In September 1961, in response to an appeal by the United Nations UN for military support, an initial force of five J 29Bs were stationed in the Republic of Congo as a contribution to a UN peacekeeping mission ONUC in the region, organized as the F 22 Wing of the Swedish Air Force. It was subsequently reinforced by four more J 29Bs and two S 29C photo reconnaissance Tunnans in 1962. The J 29s were the only combat aircraft at the disposal of the UN, the J 29Bs dispatched receiving the UN identifying legend upon their fuselages.

Most of the missions involved attacking ground targets with internal cannons as well as unguided rockets. No aircraft were lost in action despite large amounts of ground fire. Consensus of the crews and foreign observers was that the Tunnans capabilities were exceptional. Their secessionist adversaries used a few Fouga Magisters and other aircraft with relatively poor air combat capabilities. The only aircraft lost was by a high-ranking officer who made a trial run and crashed during an aborted takeoff. When ONUC was terminated in 1964, some of the Swedish aircraft were destroyed at their base, since they were no longer needed at home and the cost of retrieving them was deemed excessive.

                                     

4. Variants

J 29 Four prototypes built in 1949–50. J 29A Fighter, 224 built from 1951 to 1954; later series had wing-mounted dive brakes moved to the fuselage, ahead of the main landing gear doors. J 29B Fighter, 332 built 1953–55; featured 50% larger fuel capacity and underwing hardpoints to carry bombs, rockets and drop-tanks. A 29B Same aircraft as the J 29B, when serving with attack units. S 29C Reconnaissance "S" was derived from S paning ; scouting or reconnaissance in Swedish, 76 built from 1954 through 1956; five cameras mounted in a modified nose no armament was carried. Later modified with the improved wing design introduced on the J 29E. J 29D Single prototype to test Ghost RM 2A turbojet with 27.5 kN 2.800 kgp/6.175 lbf afterburning thrust; ultimately converted to J 29 F standard. J 29E Fighter, 29 built in 1955; introduced an improved wing design with a leading edge dogtooth to increase the critical Mach number. J 29F Fighter, 308 aircraft converted from available stocks of B and E model airframes from 1954 to 1956; featured the afterburning Ghost and dog-tooth wing; all remaining aircraft were further modified in 1963 to carry a pair of US-designed AIM-9B Sidewinder heat-seeking air-to-air missiles, built by SAAB under license as the Rb 24.


                                     

5. Operators

Austria
  • Austrian Air Force
Sweden
  • F 7 Såtenas
  • F 10 Angelholm
  • F 4 Froson
  • F 21 Luleå
  • F 8 Barkarby
  • F 13 Norrkoping
  • Swedish Air Force
  • F 11 Nykoping
  • F 6 Karlsborg
  • F 16 Uppsala
  • F 12 Kalmar
  • F 3 Malmslatt
  • F 9 Save
  • F 15 Soderhamn
United Nations ONUC
  • Swedish Air Force
  • F 22 Congo
                                     

6. Survivors

  • J 29F 29449 in the Militarluftfahrtausstellung museum at Zeltweg, Austria as F yellow.
  • J 29F 29392 displayed on the roof of the airport terminal building at Vienna-Schwechat Airport, wearing false marks as H yellow but it was once really I yellow.
  • J 29F 29441 displayed on a pillar at highway E4 outside Linkoping, Sweden.
  • J 29F 29624 displayed at the Aeroseum in a cavern at Gothenburg/Save airport.
  • J 29F 29657 National Air and Space Museum, Only example currently in the US.
  • J 29F 29665 at the Musee de lAir located at the former Paris–Le Bourget Airport in France.
  • S 29C 29970 displayed at the Flyvapenmuseum at Linkoping, Sweden.
  • J 29F 29543 at the Italian Air Force museum at Vigna di Valle.
  • S 29C 29974 displayed at the Vasterås Flygmuseum, Vasterås, Sweden.
  • J 29F 29401 displayed on a pillar at former Swedish Jamtland Air Force Wing F 4, just outside Ostersund, Sweden.
  • J 29F 29589 displayed at the side at Route 152 at Hillerstorp, Sweden.
  • J 29F 29566 displayed at the Technisches Museum fur Industrie und Gewerbe in Vienna, Austria as O yellow.
  • J 29F 29560 at Hubhof, Austria, in an anonymous blue/white colour scheme, but was once E yellow.
  • J 29F 29447 in Linz, Austria as B yellow.
  • J 29F 29666 in Soderhamn/F 15 Flygmuseum, Soderhamn, Sweden
  • J 29F 29670 in the Swedish Air Force Museum Airworthy as SE-DXB. Maintained by Swedish Air Force Historic Flight. Based Skaraborg Air Force Wing F 7.
  • J 29B 29398 in the Swedish Air Force Museum at the Ostgota Air Force Wing, just outside Linkoping, Sweden
  • J 29F 29575 in the Swedish Air Force Museum. at the Angelholms Flygmuseum on the former Scania Air Force Wing F 10.
  • J 29F 29640 Midland Air Museum, Coventry, Only example currently in the UK.
  • S 29C 29945 displayed at a car dealers at Kareby, Sweden.
  • J 29F 29588 displayed at the entrance to the military area at Graz-Thalerhof in Austria, as D red.
  • J 29F 29541 in the Osterreichisches Luftfahrt-Museum, Graz-Thalerhof in Austria as H yellow.
  • J 29F 29621 with a collector at Gotene, Sweden.
  • J 29F 29446 displayed at the Fahrzeug-Technik-Luftfahrt Museum as Bad Ischl, Austria as I red.
  • J 29F 29443 near the main-gate to the military area at Linz-Horsching airport, Austria as M yellow.
  • J 29A 29203 in Svedinos Bil- och Flygmuseum, Ugglarp, Sweden
                                     

7. Specifications Saab J 29F Tunnan

Data from The Great Book of Fighters, The Saab J 29

General characteristics

  • Empty weight: 4.845 kg 10.681 lb
  • Crew: 1
  • Powerplant: 1 × Svenska Flygmotor RM2B centrifugal-flow turbojet engine, 27.0 kN 6.070 lbf thrust
  • Height: 3.75 m 12 ft 4 in
  • Wing area: 24.15 m 2 259.9 sq ft
  • Max takeoff weight: 8.375 kg 18.464 lb
  • Length: 10.23 m 33 ft 7 in
  • Wingspan: 11 m 36 ft 1 in

Performance

  • Range: 1.100 km 680 mi, 590 nmi
  • Rate of climb: 32.1 m/s 6.320 ft/min
  • Maximum speed: 1.060 km/h 660 mph, 570 kn
  • Service ceiling: 15.500 m 50.900 ft

Armament

  • Guns
  • 4x20mm Hispano Mark V autocannon
  • Rockets
  • 145 mm 5.8 in anti-armor rockets
  • 150 mm 6 in HE high-explosive rockets
  • 180 mm 7.2 in HE antiship rockets
  • 75 mm 3 in air-to-air rockets
  • Missiles
  • Rb 24 air-to-air missiles