Tunnan | Plane-Encyclopedia

Sweden (1950)
Fighter Plane – 662 Built

The Saab 29 Tunnan was a single-seat, single-engine transonic aircraft and first-generation jet fighter. It was a small aircraft with a single central air intake placed at the nose, a bubble cockpit and thin sweptback wings. It was the very first Western European design to have a swept wing layout of 25 degrees rearward, incorporating many of the latest technologies of the time. Saab obtained access to WWII German studies involving swept wings and their positive effects in regards to speed in Switzerland, and as a result, the J 29 Tunnan came to be similar to the German Luftwaffe’s Messerschmitt Me P1101 project.

The Tunnan acheived a top speed of 1035 km/h which made it one of the fastest aircraft in the world in 1950. The nickname: ‘Flying Barrel’ was coined due to the shape of the fuselage, which came to resemble the shape of a barrel due to the large cross section of the engine and the size of the engine itself with a tapered nose and aft section. The Tunnan’s ungainly and small appearance could be deceiving however it was fast enough to set several world speed records and also had a very good agility. However, the aircraft proved challenging for inexperienced pilots. The 29 was comparable to its contemporaries: the US-made F-86 Sabre and the Soviet-made Mig-15.

The development aimed initially at producing a fighter-interceptor, but reconnaissance and ground attack versions were also developed and produced, however a training version was not produced due to time constraints of the production schedule. Sweden was developing a strong air defence system that enabled it to take advantage of innovations introduced in WWII. As a result, by late 1945 the development of the Tunnan began, with the Swedish Royal University of Technology and the National Aeronautical Research Institute taking part by providing wind tunnel testing that defined the general aerodynamics of the Tunnan. Just like the Saab J32 Lansen, a single Saab Safir was modified, fitting swept wings to its airframe in order to test the design of the wings alone.

Four prototypes were built during the development process, with the first two lacking any sort of weaponry carrying heavy testing equipment instead, and the third prototype carrying four 20mm Hispano Mark V cannons. These prototypes tested different aerodynamic features, such as the location of the airbrakes – either in the fuselage or on the wings, as well as the configuration of the ailerons and flaps. The prototypes also hinted that the Tunnan design would be able to reach and even exceed the maximum Mach they were designed for. Once in service the Tunnan broke many records. It set a world speed record on a 500 km closed circuit as it reached a speed of 977 km/h in 1954. The reconnaissance version set also a record of 900.6 km/h in a closed circuit of 1000 km.

In 1948, the J 29 Tunnan flew for the first time, in service with the Flygvapnet from 1951 until 1976, with 662 fighters built from 1950 to 1956 making the Tunnan the most numerous aircraft produced Saab, as well as the longest lived design in service. It also served with the Austrian Air Force with 30 units in service until 1973. A single J 29F still can be seen flying at airshows around Europe.

Design

The Tunnan is a thin 25 degrees swept back laminar-flow mid-wing fighter, having a single tail and a single engine, featuring the design similar to most of the first generation jet fighters: a single engine with a central straight-through airflow system that maximized thrust. Two tubular pitot sensors were located at the wing tips. For lateral stability during take-off and landing, automatic-locking leading edge slots were fitted in the wings and were also interconnected with the flaps. It was later on enhanced with the installation of an afterburner and of dog-tooth leading edge in the wings – which increased the Mach speed the Tunnan could attain. Trim tabs and dive brakes were also incorporated to the design, being initially placed on the wings and later re-located to the fuselage, directly forward of the main landing doors.

The Tunnan also featured a bubble shaped canopy with the cockpit located right above the engine air intake, and forward the wing’s leading edge. The canopy was opened by sliding backwards, allowing the pilot to access and exit. The design also took advantage of the already existing ejector seat developed in 1943 by Saab, complemented by an explosive jettison system to remove the canopy in case of ejection. The landing gear was of tricycle configuration, with the rear wheels retracting into the fuselage, which contributed in making the wings thin, and a single wheel gear at the nose. The vertical stabilizer had a tapered edge, being straight trailing edge with a blunt tip, with the tail section placed above and behind the engine exhaust nozzle. In turn, the horizontal stabilizer is mounted practically at the base of the tail. The Tunnan proved to be not only a very capable and agile fighter, but also proved very durable in sorties. During a UN mission in the Congo it received intensive ground fire without sustaining any noticeable damage.

The engine, along with its aerodynamic characteristics, made of the Tunnan a fast fighter. The powerplant consisted of a DeHavilland Ghost turbojet engine producing 5000 lbs of thrust. This engine was deemed suitable for the fuselage of the Tunnan, replacing the originally planned DeHavilland Goblin, and had the advantage of making maintenance easy with the engine cowling able to be removed as a single piece.

The armament of the Tunnan consisted of four 20mm Hispano Mark V cannons placed in pairs on both sides under the nose. The pylons were capable of carrying 75mm air-to-air rockets, 145mm anti-armour rockets, 150mm HE (High Explosive) rockets and/or 180mm HE anti-ship rockets. Later versions were capable of using Rb24/AIM-9 Sidewinder air-to-air missiles. Fuel air-drop tanks could be used as napalm bombs.

Swedish Resolve

The Tunnan is the product of Swedish concerns about its security during World War II, in the face of Germany’s rapid annexations of both Norway and Denmark and acknowledging the country was unable to resist such aggression. But there were also of concerns that Sweden was falling behind after the rapid development of technologies and innovations brought about during the war. Sweden’s isolation in this aspect was exacerbated by the degree of defense secrecy by both the Axis and Allied countries. As a result, an effort was made in order to strengthen defensive capabilities with the focus being placed on the development of modern aircraft to bolster air defence, exploiting the war-time innovations in power – namely the recently introduced jet propulsion technologies as well as other advances in aircraft design. The new technologies were exploited after Sweden obtained access to research after the war. The already existing Saab J 21R was utilized to make the transition between the piston and jet propelling engines and to provide a temporary solution, but it was deemed necessary to develop a much more modern aircraft in order to keep the air defences fit. The Tunnan became the solution, making the Swedish Air Force the 4^th largest during the mid-century.

Peacemaker from the North

All the aircraft produced by Saab and in service with the Flygvapnet from 1948 to 1989 saw relatively little combat. The Tunnan constitutes the only exception, as it saw extensive use during conflict in Central Africa. As the crisis in the Congo unfolded in 1961, Sweden contributed five J29B Tunnans that were tasked with protecting UN’s air transport and providing fire support to cover UN ground troops when needed, constituting the F22 unit. In 1962, four additional J29Bs and two J29Cs were sent. The 11 Tunnans provided by Sweden to the UN mission comprised the only air component of the UN at the time. As the crisis evolved and the additional six Tunnan were required, air superiority was achieved along with ground attack missions that involved the utilization of the fighter’s 4 Hispano cannons and rockets. The missions mainly focused attacks on military trains and airfields at Katanga, as other aerial assets from Ethiopia – F 86 Sabres – and India – Canberra light bombers – withdrew. When the UN peacekeeping mission was over in 1963, four of the Tunnans returned to Sweden, while the remaining met an ignominious ending, destroyed at the base, as it was deemed prohibitively expensive to return them.

Variants

J 29 – Four prototypes built in 1948-1950, for the development process only.
J 29A – Fighter version. Armed with four 20mm Hispano Mark V cannons, and 12 75mm anti-armor rockets. Later series relocated the wing-mounted dive brakes into the fuselage. Remained in service until 1965. 224 delivered.
J/A 29B – Fighter/attacker version. It featured an increased 50% fuel capacity and wing hardpoints with provisions to carry bombs, rockets – 8 or 14 80mm or 145mm anti-armour; 8 or 14 150mm HE; 2 or 4 180mm anti-ship – and fuel drop-tanks that could be used as napalm bombs. Served until 1965. 332 delivered.
J 29C – Reconnaissance version for day and night operations. It carried between 5-6 cameras in a modified nose, being unarmed cameras replaced the 4 guns. It received the same wing enhancement of the J 29E. It also became the first jet-powered photographic-reconnaissance aircraft introduced by a non-aligned nation, as well as the first Swedish aircraft to be equipped with radar warning receivers. An antenna for backwards-looking radar was placed at the tail cone, being afterwards relocated This version set a new speed record back in 1955, reaching speeds 900.6 km/h (559.6 mph) in a closed circuit of 1000 kms (621.4 miles). 76 delivered.
J 29D – A single unit to test the DeHavilland Ghost RM2 turbojet fitted with an afterburning thrust, later upgraded to J 29F.
J 29E – Fighter version, which incorporated an enhanced wing design by fitting leading edge dogtooth, aimed at increasing critical Mach number. It also increased load factor. Same armament configuration as the J 29B. Upgraded to the J 29F version. 29 delivered.
J 29F – Fighter version, which were modified J 29B and J 29E airframes. This version featured the enhanced wing design of the J 29E, and the DeHavilland Ghost engine equipped with an afterburner. This version was also optimized to carry two Saab Rb24 (AIM-9 Sidewinder) missiles in 1963, having the same armament payload of the J 29B. It also performed in the role of aggressors, and performed target towing. Most were retired by 1967. 308 converted aircraft.
SK 29 – Planned training version. It could have featured a two-seated cockpit, with seats placed side-by-side, no armament and limited fuel capacity. Cancelled.
J 29R – All-weather fighter version equipped with an air intercept radar. Cancelled.

Operators

Sweden – The Flygvapnet operated the Tunnan from 1951 to 1967, having 665 units operating, all of the J 29A, J/A 28B, J 29C, J 29E and J 29F versions. Some were kept for countermeasures trainers and target towing duties until 1976. 11 J 29Bs and J 29Cs took part in the United Nations Operation in the Congo (ONUC), being the only Tunnan, and actually the only aircraft during the Cold War of the Swedish Air Force to take part in combat operations abroad.
Austria – The Österreichische Luftstreitkräfte (Austrian Air Force) operated 15 restored J 29Fs by Saab in 1961, where they formed the first Jagdbomber Staffel. An additional 15 restored J 29Fs were sold to Austria, where the two guns on the port side could be replaced by three cameras, which were moveable during flight forming the second Jagdbomber Staffel in the Austrian Air Force. These remained in service until 1972.

J 29F Tunnan Specifications
Wingspan	11 m / 36 ft 1 in
Length	10.23 m / 33 ft 6.7 in
Height	3.75 m / 12 ft 3.6 in
Wing Area	24.15 m² / 260 ft²
Engine	1 DeHavilland Ghost 50 Turbojet (Svenska Flygmotor RM2B Turbojet)
Maximum Take-Off Weight	7,530 kg / 16,600 lb
Empty Weight	4,580 kg / 10,097 lb
Loaded Weight	13,529 kg / 35,273 lb
Maximum Speed	1,035 kmh / 643 mph (1,075 kmh / 668 mph in full afterburner)
Range	1,500 Km / 932 miles
Maximum Service Ceiling	13,700 m / 45,000 ft
Climb Rate	2,400 m/min (7,874 ft/min)
Crew	1 (pilot)
Armament	4 X 20 mm Hispano Mark V located at the nose 2 Saab Rb 24 (AIM-9 sidewinder) missiles 75mm air-to-air rockets 80mm or 145mm anti-armour rockets, 150mm HE rockets, and/or 180mm HE anti-ship rockets. 4 X SKa 10 cameras, 1 X SKa 15 camera for mapping, and 1 X SKa 5. 2 X fuel drop tanks that could be used as napalm bombs.