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Sud-Ouest SO 6020 / SO 6021 / SO 6025 / SO 6026 Espadon

SO 6020 Espadon

The first turbojet-powered single-seat fighter of French design to be built, the SO 6020 Espadon (Swordfish) interceptor was developed by the Societe Nationale de Constructions Aeronautiques de Sud-Ouest (SNCASO) under the design leadership of Lucien Servanty. Conceived to meet the requirements of a programme promulgated on 25 March 1946, and the subject of an order for three prototypes placed two months later, on 28 June, the SO 6020 was powered by a 2268kg Rolls-Royce Nene turbojet with, unusually, an aft-mounted ventral air intake. The SO.6020 featured flush inlets on the fuselage sides aft of the wing trailing edge. Proposed armament was initially to have comprised four 30mm cannon and four 12.7mm machine guns, this later being changed to six 20mm or 15mm weapons.

The first prototype flew on 12 November 1948 and the second on 16 September 1949, the latter being modified, after initial test, with NACA-type lateral intakes in place of the ventral intake. It was appreciated at an early stage that the SO 6020 was underpowered and would offer inadequate performance, a major redesign as the SO 6021 therefore paralleling initial flight testing of the SO 6020. The third prototype, intended for tactical reconnaissance, was completed as the SO 6025 with lateral intakes and a ventrally-mounted SEPR 25 auxiliary rocket motor of 1500kg thrust, this flying on 28 December 1949.


Sud-Ouest SO 6021 Espadon

The SO 6021 represented an attempt to reduce the weight and alleviate some of the aerodynamic problems that had beset the SO 6020 from the outset of flight test. Retaining the same Nene engine, but having a 1.30sq.m increase in wing area, an entirely redesigned vertical tail and a 604kg reduction in empty weight, the SO 6021 was equipped with servo controls and flew on 3 September 1950. Armament comprised six 20mm cannon. In June 1951, a ground attack version of the SO 6021 was offered to the Armee de l'Air with an afterburning Rolls-Royce Tay engine and an armament of two 30mm cannon. However, testing of the SO 6021 indicated that some of the difficulties experienced with the SO 6020, notably the shortcomings of the air intake arrangement, had not been overcome. A speed of Mach=0.96 was attained in a shallow dive, but serious buffet occurred at Mach=0.75, and further development was abandoned, the sole SO 6021 serving as a test bed for small wingtip-mounted turbojets associated with the SO 9000 programme, continuing in this role until 1956.

SO.6025 Espadon


The second prototype, with a similar rocket motor installed in the rear fuselage, became the SO 6026, flying in this form for the first time on 28 March 1953.
In 1953 the third prototype built had its wings replaced by bigger ones and fitted with rocket engine SEPR. This resulted in being the first European aircraft to break the sound barrier in level flight on 15 December 1953.
Considerably more development followed, but by 1953 the type was clearly obsolescent and further work was abandoned.
The third prototype was once being used a target at firing range before being recovered to the Ailes Anceinnes museum in Toulouse by August 2018.

​Sud-Quest SO 6025 Espadon 03 ​


Loaded weight: 7454 kg / 16433 lb
Empty weight: 5354 kg / 11804 lb
Wingspan: 10.60 m / 35 ft 9 in
Length: 15.00 m / 49 ft 3 in
Height: 4.55 m / 15 ft 11 in
Wing area: 25.20 sq.m / 271.25 sq ft
Max. speed: 967 km/h / 601 mph

SO 6021 Espadon
Loaded weight: 6870 kg / 15146 lb
Empty weight: 4750 kg / 10472 lb
Wingspan: 10.60 m / 35 ft 9 in
Length: 15.00 m / 49 ft 3 in
Height: 4.72 m / 16 ft 6 in
Wing area: 26.50 sq.m / 285.24 sq ft

Sud-Ouest SO 6021 Espadon




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