Stemming from the lightweight fighter philosophy that emerged from the Korean conflict, the SO 9000 Trident single-seat interceptor developed by a team led by Lucien Servanty was of unusual concept in employing turbojets for auxiliary power and a rocket motor for primary thrust. Two prototypes of the Trident were ordered on 8 April 1951, the first of these flying on 2 March 1953 solely on the power of two wingtip-mounted Turbomeca Marbore II turbojets each rated at 400kg, the more powerful Vipers being substituted in 1955. The second prototype was destroyed on its first flight on 1 September 1953, but development continued with the first example, which, on 4 September 1954, flew for the first time with its primary power plant, a triple-barrel SEPR 481 triple-chamber liquid rocket motor providing a total thrust of 4500kg. As the aircraft could not take-off on the power of the Marbores at fully loaded weight, these gave place to Dassault MD 30 (Viper ASV 5) turbojets of 745kg, with which it flew on 17 May 1955. Although conceived as a combat aircraft, the SO 9000 had meanwhile been overtaken by a more advanced development, the SO 9050, and its test programme was terminated on 10 December 1956, the prototype having achieved a speed of Mach=1.63 – the highest speed attained by any piloted aircraft in Europe at that time – and an altitude of 15,000m.
SO 9000 Trident
SO-9000 Trident I 2 x Marboré II turbojets, 800 lb st
SO-9000 Trident I 2 x Armstrong Siddeley Viper 5 turbojet, 1640 lb st, 1 x SEPR 481 rocket, 9920 lb thrust Wingspan: 26 ft 8.75 in (8.15m) Length: 45 ft 11.25 in (14m) Wing area: 99.03 sq.ft (9.2 sq.m) Max wt: 12,125 lb (5500kg) Max speed: 1056 mph @ 36,000 ft Crew: 1
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
SO-6020 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
The Sud Ouest SO 6000 Triton, first flying on 11 November 1946, was the first French jet powered aircraft to fly. Five were built. The first was powered by a 1980 lb thrust Junkers Jumo 004-B2 with a nose intake. Later versions had a 4850 lb thrust H-S Nene with both nose and fuselage scoops.
They were used as test beds and side-by-side trainers.
The third built, SO-6000-03, is at the French Musee de L’Air.
Engine: Rolls Royce Nene 101, 21582 N Length: 34.121 ft / 10.4 m Wingspan: 32.644 ft / 9.95 m Wing area: 162.536 sq.ft / 15.1 sq.m Max take off weight: 10363.5 lb / 4700.0 kg Weight empty: 7056.0 lb / 3200.0 kg Max. speed: 513 kt / 950 km/h Cruising speed: 462 kt / 855 km/h Initial climb rate: 9842.52 ft/min / 50.0 m/s Service ceiling: 39370 ft / 12000 m Wing load: 63.76 lb/sq.ft / 311.0 kg/sq.m Crew: 2
After the cancellation of the SO.4000, the Sud-Ouest design team turned to a more refined type, the SO.4050 Vautour that eventually entered service in three versions optimized for MK.IIN all-weather interception, Mk.IIA close support, and Mk.IIB bombing from medium and high altitudes.
The SNCASO SO.4050 Vautour (Vulture) was first flown on 16 October 1952. Midway in size between small fighters and jet medium bombers, it had the same layout as the much bigger Boeing B 47, with a mid-high 35 degree swept wing, under-slung engines, a fighter type nose cockpit and so-called bicycle landing gear. The front wheels retract forward and the rear wheels rearward. Small balance wheels were under each engine nacelle. Fitted with conventional ailerons, rudder, all-moving tailplane, split flaps, and an air brake on each side of the rear fuselage.
Each engine was fed from its own set of fuel tanks. The inner 17 fuel tanks had an automatic system to “isolate” cells which caught fire or to neutralize leaks in the passages. The pilot could direct or divert flow of fuel in case of damaged pipes or engine malfunction. The Vautour didn’t have inflight refuelling devices. Only the experimental (FR-AF) IIA(R) s/n 8, was tested as an air tanker for the Mirage-4.
The Vautour prototype was the first French twin-jet aircraft to exceed the speed of sound in a shallow dive. Various engines were fitted in the three prototype and six pre-production models but all production Vautours had Atar turbojets.
Produc¬tion took place later in three versions. The Vautour IIA is a single seat tactical fighter, of which 30 were built, the first production machine flying on 30 April 1956. Twenty-five Vautour II-As were supplied to Israel.
Vautour IIA
Vautour IIB
Only one of the six pre-production Vautours was a bomber, the others consisting of two tactical support aircraft and three all-weather fighters. The Vautour IIB had a single seat pilot cockpit similar to that of the Vautour IIA attack version, but added a glazed nose for a navigator/bombardier who could use a conventional bombsight. Navigation was mainly by a twin gyro platform and Doppler radar, and considering the small dimensions of the aircraft an excellent bombload could be carried both internally and externally. The first production aircraft of this IIB sub type flew on 31 July 1957 and eventually 40 were delivered to equip the Armee de l’Air’s 92e Escadre, which was the original operating ele¬ment of the Commandement des Forces Aeriennes Strategiques (strategic air command). Special bomb-dropping gear was developed for them in which the weapons were extended below the bomb bay prior to release, to make possible attack a transonic speeds from all altitudes. The Vautour IIB (redesignated Vautour IIAB after fitting one piece tailplanes in the early 1960s) was replaced by the Dassault Mirage IVA from 1965.
The first of 70 Vautour II-N all weather fighters flew on 10 October 1956.
SO.4050 Vautour II-N
It was in service with the air forces of France (II-Bs and II-Ns) and Israel (25 II-As).
Mk.IIA Engine: 2 x SNECMA Atar 101F-3, 34.3kN, 7716 lb Wingspan: 15.09 m / 49 ft 6 in Wing area: 484.4 sq.ft Length: 15.57 m / 51 ft 1 in Height: 4.5 m / 15 ft 9 in Max take-off weight: 20000 kg / 44093 lb Empty weight: 10000 kg / 22046 lb Internal fuel: 5,364 lt / 17 tanks Weapon bay fuel capacity: 3,000 lt (2 x 1,500 lt tanks) External fuel: 2 drop tanks of 1,300 lt or 600 lt Max fuel capacity: 10,964 lt / 8,771 kg Max. speed: 1105 km/h / 687 mph at SL Ceiling: 15000 m / 49200 ft Armament: 4 x 30mm cannons, 1850kg / 6000 lb of bombs Seats: 1
Mk.IIB Type: two seat bomber Engines: 2 x Powerplant: 2 x SNECMA Atar 101 E 3 turbojets, 3500 kg (7,720 lb) Wing span: 15.1 m (49 ft 6.5 in) Length: 15.55 m (51 ft 0.25 in) Height: 4.32 m (14 ft 2 in) Wing area: 45.00 sq.m (484.4 sq ft) Empty wt: 10470 kg (23,082 lb) MTOW: 21000 kg (46,300 lb) Max speed: 1100 km/h (685 mph) at low level and 950 km/h (590 mph) at 12190 m (40, 000 ft) Radius with max bombload: 930 km (580 miles) Max range: 5950 km (3,700 miles) Armament: internal six bombs of 340 kg (750 lb) Hardpoints: four – 500 kg (1, 102 lb) each Weapon bay fuel capacity: 3,000 lt (2 x 1,500 lt tanks) External fuel: 2 drop tanks of 1,300 lt or 600 lt
Mk.IIN Engines: 2 x SNECMA Atar 101E-3 turbojet, 7716 lb Wingspan: 49 ft 6.5 in Length: 14 ft 1.75 in Wing area: 484.4 sq.ft Empty weight: 23,150 lb MTOW: 45,635 lb Internal fuel: 4426 lt Weapon bay fuel capacity: 3,000 lt (2 x 1,500 lt tanks) External fuel: 2 drop tanks of 1,300 lt or 600 lt Max fuel capacity: 10,026 lt / 8,021 kg Max speed SL: 685 mph Max ROC: 11,800 fpm Service ceiling: 50,000 ft Armament: 4 x DEFA cannon Hardpoints: 4 Seats: 2
IIBR Engines: 2 x Powerplant: 2 x SNECMA Atar 101 E 3 turbojets, 3500 kg (7,720 lb) Max speed: 1100 km/h (685 mph) at low level and 950 km/h (590 mph) at 12190 m (40, 000 ft) Radius with max bombload: 930 km (580 miles) Max range: 5950 km (3,700 miles) Empty wt: 10470 kg (23,082 lb) MTOW: 21000 kg (46,300 lb) Wing span: 15.1 m (49 ft 6.5 in) Length: 15.55 m (51 ft 0.25 in) Height: 4.32 m (14 ft 2 in) Wing area: 45.00 sq.m (484.4 sq ft) Weapon bay fuel capacity: 1 x 1,500 lt tank External fuel: 2 drop tanks of 1,300 lt or 600 lt Max fuel capacity: 9,464 lt
The SO 4000 was developed by the Société Nationale de Constructions Aéronautiques de Sud-Ouest (SNCASO) to meet an Armée de l’Air requirement formulated shortly after WWII for a twin-turbojet bomber capable of high subsonic speeds and having a maximum loaded weight of 25-30 tonnes. The SO 4000 project competed with the NC 270 project tendered by the SNCA du Centre, and after the flight testing of manned scale models, the SNCASO bomber was selected for further development. The half-scale model predecessors of the SO 4000 were the SO M.1 glider (F-WFDJ) and the powered SO M.2 (F-WFDK).
The single prototype of the full-scale SO 4000 bomber, (F-WBBL) had been rolled out for the first time on 5 March 1950. While essentially similar in configuration to the M.1 and M.2, the SO 4000 featured a tall undercarriage comprising a single nosewheel and tandem mainwheels each with independent legs. This undercarriage proved somewhat fragile, collapsing during ground trials on 23 April. After repairs were completed, flight testing finally commenced at Orleans-Bricy on 15 March 1951, test pilot Daniel Rastel being accompanied by flight engineer Pistrak.
The SO 4000 was powered by two Rolls-Royce turbojets mounted side-by-side in the rear fuselage, these being fed via lateral intakes immediately aft of the pressurised forward fuselage. Fuel was accommodated above the weapons bay in the centre fuselage and proposed defensive armament consisted of remotely-controlled gun barbettes at the wingtips. The 31 deg swept wing had a 10 per cent thickness/chord ratio from root to tip and the control arrangement was fundamentally similar to that of the M.2. The initial flight of the SO 4000 was also to prove its last as the undercarriage collapsed once more on alighting, the programme subsequently being discontinued as a result of a reduction in military credits.
Engines: 2 x Rolls-Royce Nene 102 turbojets, 4,980 lb st (2 260 kgp) Fuel cap: 1430 ImpGal (6500 lt) Wing span: 58 ft 7 1/8 in (17,86 m) Length: 64 ft 9½ in (19,75 m) Wing area of 807.32 sq ft (75,00 sq.m) Empty wt: 36,5581b(16 583 kg) Loaded wt: 48,510 lb(22 005kg) Estimated performance – Max speed of 528 mph (850 km/h) at 29,530 ft (9 000 m) or Mach 0.78 and 515 mph (830 km/h) at sea level or Mach 0.675.
This is the first French convertible. It can take off vertically, hover in the air, land vertically by means of its rotor, and fly forward at a speed greater than that of pure helicopters by means of a fixed wing and an airscrew fully independent of the rotor.
The change from one state to the other is accomplished without any change at all in the external appearance. The SO.1310 is provided with two independent power units. In the rear is an Arrius II 360hp Turbomeca unit, which supplies the jet rotor with compressed air at take-off. The all-metal three-bladed rotor is identical with the one used in the SO.1120 Ariel III, but with a larger diameter.
In the forepart there is a Turbomeca Artouste II turbo-prop engine with a take-off power of 360 hp, operating a variable-pitch airscrew. During forward flight, the rotor originally used for take-off continues to auto-rotate, but with low lift, and the greater part of the lift is transferred to the fixed wing. Mounted over the fixed wing is the pilot’s cabin, fitted with dual control, and in this cabin there is room for either three passengers, a freight load or two stretchers stacked on top of each other.
The Farfadet single prototype F-WBGD first flew on 8 May 1953. Its maiden flight, lasting about twenty minutes, was made as a true helicopter, the following one, on the same day, with the rotor and the airscrew respectively powered by their individual engines.
SO.1310 Farfadet Engine: 1 x 360 hp Turbomeca Artouste II gas turbine & 1 x 360 hp Turbomeca Arrius II gas turbine Rotors: 3-blade tip-powered main rotor; 2-blade propeller Rotor diameter: 11.2m / 36 ft 6 in Wingspan: 6.3m / 19 ft Fuselage length: 10.08m Height: 3.3m Weight fully loaded: 1510kg Empty weight: 995kg Cruising speed as a helicopter: 155km/h Cruising speed as an autogyro: 250km/h Range: 400km / 250 miles at 149 mph Seats: 3
The experience acquired by Sud-Ouest in building its two prototypes of the Ariel led to the SO.1221 Djinn. The Djinn’s began with two single-seat SO.1220 prototypes, F-WGVO and F-WGZX, the first of which made its maiden flight on 2 January 1953. A simple uncovered structure of welded steel tube carrying a two-blade rotor above it, and with a single exposed seat for its pilot. Its powerplant was a Turbomeca Palouste turbo-compressor producing a large volume of compressed air which, using a similar distribution method to that of the Ariel, was discharged at the blade tips. These were both intended primarily to prove the rotor and propulsion systems.
F-WGVO was later fitted experimentally with agricultural spray booms.
On 16 December 1953 the first of five 2-seat SO.1221 prototypes was flown, having a fully enclosed cabin, two side-by-side seats, an open-framework tail boom, and an all-up weight of 600kg. On 29 December this aircraft established a new altitude record in its class of 4789m.
The Djinn was the world’s first production helicopter to make use of the ‘cold jet’ principle of propulsion. This system used a modified Turbomeca Palouste IV engine as a turbo-generator to feed compressed air through the rotor shaft to ejectors built into the tips of each rotor blade. The air itself is in fact warm enough to eliminate the need for other means of de-icing the blades. No tail rotor is fitted, the aircraft having two outrigged fins and a large central rudder that is situated in the line of the residual thrust exhaust from the engine to provide directional control. The craft’s small spartan two-seat cockpit was surrounded by a sectioned bubble-type enclosure and transparent side doors, which combined to provide excellent visibility forward and to both sides. Cockpit instrumentation was quite basic in the standard SO.1221, and The Djinn’s landing gear was of the skid type, with small retractable wheels to facilitate ground handling.
Twenty-two pre-series SO. 1221’s were then built, primarily for evaluation for the French Army, and the first of these was flown on 23 September 1954. Three machines from this batch were evaluated by the U.S. Army, under the designation YOH-1.
In late 1956 the US Army leased three examples for evaluation in the observation role. The Djinn, which had first flown in December 1953, was already in service with the French Army as an observation craft and its success in that role, coupled with its relatively low per-unit cost and fairly basic maintenance requirements, piqued the Army’s interest. The machines obtained by the Army (serials 57-6104 through -6106) were the first helicopters acquired under the new HO (helicopter, observation) classification, and were designated YHO-1. the three YOH-1s were consequently fitted with additional U.S. military-standard avionics and communications equipment for their Army evaluation.
The Army’s engineering and operational evaluation of the YOH-1 found the aircraft to be well built, relatively easy to maintain under field conditions, and an exceptional observation platform. The Djinn was not adopted for service use, however, primarily because the Army faced continuing budgetary constraints and some domestic political opposition to the procurement of French, rather than American (or Canadian) aircraft. In early 1958 all three YOH-1s were returned to Sud-Ouest for ultimate delivery to the French Army.
Chief customer for the Djinn has been France’s Aviation Legere de l’Armee de Terre, which received one hundred of the one hundred and fifty production Djinns completed up to 1961, and still had about half of these in service in mid-1967. The first production aircraft was flown on 5 January 1956, and French and US certification was gained in April 1958. Six were also delivered to the Federal German Heeresfliegerei. The military Djinns operate at a slightly higher gross weight – 800kg – than the civil models. One was used in France for the first experiments in launching Nord SS.10 anti-tank missiles from a helicopter, but the Djinn’s main military functions have been those of observation, liaison, training and (with one pilot and two external litters) casualty evacuation.
Between forty and fifty civil Djinns were active in ten countries, most of them in an agricultural role, for which Sud-Aviation offered renewed conversion facilities in 1965. The so-called ‘agricopter’ version of the Djinn can carry up to 200 litres of liquid chemical in twin tanks, and is fitted with lateral spray bars for the spraying, dusting or ‘fogging’ of crops with fertilisers or pesticides.
When production ended in the mid-1960s a total of 178 had been built, exported to about 10 countries. Many were used in an agricultural role, equipped with two tanks to contain liquid chemicals and spray bars for its distribution. By the time that production ended Sud-Ouest had twice changed its name, to Ouest-Aviation on 1 September 1956 and Sud-Aviation on 1 March 1957 when it merged with Sud-Est Aviation; this explains why the Djinn is sometimes recorded as the Ouest S.O.1221 or Sud-Aviation S.O.1221.
Sud-Ouest SO-1221 Djinn Engine: 1 x Turbomeca Palouste IV turbo-compressor, 179kW / 237 shp Main rotor diameter: 32 ft 10 in / 10.97 m Fuselage length: 17.388 ft / 5.3m Height: 8.530 ft / 2.6m Width of hull: 6.332 ft / 1.93 m Max take-off weight: 800kg / 1,550 lb Empty weight: 793.8 lb / 360kg Max speed: 70 kts / 130km/h / 75 mph Endurance: 2h 15min Initial climb rate: 1279.53 ft/min / 6.5 m/s Service ceiling: 13123 ft / 4000 m Range: 103 nm / 190 km Typical range: 100 miles at 44 mph Crew: 2
The 1948 experimental Ariel helicopters used tip jets at the blade tips.
The SO.1221 was powered by a cold-jet propulsion system developed by Sud-Ouest for its earlier two prototypes Ariel II and III helicopters. Residual thrust from the engine is ducted to the end of the fuselage and used for directional control.
Engine: 275 h.p. Turbomeca Arrius gas-turbine Rotor diameter: 35 ft 5 in Rotors: 3-blade tip-powered main rotor. Fuselage length: 27 ft 2 in Loaded weight: 2,750 lb Ceiling: 15,000 ft Typical range: 155 miles at 85 mph with 1,000 lb load Seats: 2-3
The half-scale model predecessors of the SO 4000 were the SO M.1 glider (F-WFDJ) and the powered SO M.2 (F-WFDK), these featuring a laminar flow wing swept 31 deg at the mainspar, mounted in the high-mid position and combining small ailerons interconnected with spoilers and leading-edge slats. The undercarriage consisted of a retractable central skid with wingtip stabilising skids in the case of the M.1, while that of the M.2 comprised a nosewheel, three main-wheels in train and wingtip outrigger wheels.
The powered M.2 had entered flight test five months earlier than the M.1, on 13 April 1949, when it was flown for the first time at Orléans-Bricy with Jacques Guignard at the controls. The M.2 was powered but was in most other respects, similar to the M. 1.
During its seventh flight in May 1950, with Daniel Rastel at the controls, the M.2 exceeded 621 mph (1 000 km/h) in a shallow dive. For the second phase of its flight test programme, commencing in October 1951, the M.2 was fitted with a modified control system, a revised undercarriage retraction system, provision for the installation of powder rockets to augment thrust at high altitude and wingtip fuel tanks. Empty and loaded weights being raised to 9,369 lb (4 250 kg) and 11,905 lb (5400kg).
Engine: Rolls-Royce Derwent V turbojet, 3,000 lb st (1360 kgp) Span: 3l ft 2 in (9,50m) Length of 32 ft 5.75 in (9,90 m) Wing area: 193.76 sq ft (18,00 sq.m) Empty wt: 8,466 lb (3 840 kg) Loaded wt: 10,362 lb (4 700 kg)
The Alouette II is a turbine development of the earlier SE-3120 Alouette with 200 h.p. Salmson 9 NH piston engine. A small pre-production batch was under construction, with the first five due for delivery late 1955.
Engine: Turbomeca Artouste II turbine, 360 hp Rotors: 3-blade main; 2-blade tail Rotor diameter: 38 ft Loaded weight: 2,980 lb Ceiling: 14,764 ft Typical range: 323 miles at 106 mph Seats: 5
All Aero 