SNCASO SO.4000

The SNCASO SO.4000 was an experimental French twin-engine jet-bomber aircraft of the 1950s. It was the first French jet bomber to be developed, despite the type never entering operational service.[1]

SO.4000
Role	Bomber
National origin	France
Manufacturer	SNCASO
First flight	15 March 1951
Status	Prototype only
Number built	1

The SO.4000 was developed out of ambitions to design and produce cutting-edge indigenous aircraft; specifically, the French Air Force sought to equip itself with its first jet bomber, and produced a specification calling for such shortly after the end of Second World War. Having tendered in response, SNCASO's SO.4000 received a development contract to produce a pair of models and a full-scale prototype. The single full-scale aircraft, which performed its first and only test flight on 15 March 1951, would never enter mass production. Even prior to this flight, the design had been rendered obsolete by rapid advances in the field of aviation. Specifically, the SO.4000 was considered to be overweight and underpowered. Shortly after its only flight, during which it had been damaged during landing, it was decided to abandon development entirely.

Development

According to aviation author Peter Caygill, France's aviation industry was in dire straights, perhaps having been more damaged than any other nation, as a consequence of events in the Second World War.[2] Regardless, French industrialists and government officials alike were keen to make rapid advances in aviation technology to not only revive the nation's aviation capabilities, but to utilise the newest advances and produce a new generation of competitive indigenously-built aircraft. France, akin to the other Allied nations in the war, had benefitted from captured German research into high speed aircraft; these factors combined gave a great impetus to undertaking advanced research projects.[2] Aviation authors Bill Gunston and Peter Gilchrist note that such efforts were aimed at reducing France's reliance upon foreign-sourced technology, such as mastering recent advances in jet propulsion and transonic aerodynamics.[3]

Shortly following the conflict's end, the resurgent French Air Force produced a requirement for a jet bomber with which to equip itself. The envisioned bomber was expected to have a takeoff weight of roughly 25–30 tonnes and would be capable of flying at high-subsonic speeds. The development of a capable jet-powered bomber aircraft was viewed as being a major technological challenge for the era; this initiative would produce the first French jet bomber in the form of the SO.4000.[3]

Multiple submissions were tendered by French aircraft manufacturers, including SNCASO with the SO 4000 and SNCAC's rival bid in the form of the SNCAC NC 270. Following a competitive review, SNCASO would receive a development order calling for a pair of manned scale models and a full-sized prototype. The first scale model, known as the SNCASO M.1, was an unpowered glider which would be tested from atop the Heinkel He 274 V1, (as the French AAS 01A), the first prototype of Heinkel's prototype-only late-war high-altitude strategic bomber design, which had remained in France after the war.[4] The He 274, having drawn the attention of French authorities, had been restored to a flightworthy condition to allow such use. The second aircraft, the SNCASO M.2, was powered by a single British-sourced Rolls-Royce Derwent turbojet engine. SNCAC also received a contract to prototype their submission.[5][6]

During 1947, as a result of the rapid advances made in aviation technologies made around this time, plans for a subsequent production run were abandoned. Nevertheless, it was decided to complete the two scale models and the full size prototype for experimental purposes.[7] On 13 April 1949, the sole M.2 conducted its maiden flight, while the M.1 glider performed its first free-flight, launched from a SNCASE Languedoc, on 26 September 1949.[5] Testing of the M.2 was considered to be successful, on one occasion having exceeded 1,000 km/h (621 mph) while flown in a dive, becoming the first French aircraft to achieve this feat. Both the M.1 and M.2 provided valuable data on features such as swept wings, pilot escape systems, spoiler control, and leading edge slats.[1]

On 5 March 1950, the SO.4000 was rolled out; by this point, it was already obsolete and lacking in capabilities compared to its contemporaries.[1] During the following month, the aircraft sustained damage when its undercarriage collapsed during taxiing tests. After completing repairs, the SO.4000 performed its maiden flight on 15 March 1951, piloted by chief test pilot Jaques Guignard.[1] During landing, its undercarriage failed again, resulting in damage. The aircraft would never fly again and work on the project was abandoned without any further testing being carried out.[5] According to Gunston and Gilchrist, the SO.4000 was a very heavy aircraft, which only compounded the weakness of possessing relatively little engine power, giving it an extremely poor thrust-to-weight ratio even when empty; they also criticised it as possessing "useless capabilities".[1]

Design

The SO.4000 was an unconventional experimental jet bomber. It featured a mid-mounted wing, which was swept at an angle of 35 degrees and mated with a carefully streamlined oval-section fuselage, which was furnished with a relatively tall tricycle undercarriage. This undercarriage, which was provisioned with tandem mainwheels, was somewhat unorthodox, as they retracted outwards into alcoves cut into perhaps the most stressed area of the airframe.[8] The aircraft was powered by a pair of Rolls-Royce Nene turbojet engines, each capable of generating a maximum of 22.2 kN (4,980 lbf); Gunston and Gilchrist note the use of the Nene to be one of the few conventional choices adopted for the design.[3] These engines were mounted in a side-by-side arrangement housed within the rear fuselage.[5] Inlets for the engine were located on either side of the forward fuselage, while boundary layer air was directed via a splitter to slits above and below the lengthy inlet duct. The tailpipes were somewhat unusual, the nozzles being separated by the aircraft's fin.[3]

The SO.4000 was operated by a crew of two, consisting of a pilot and test engineer/observer, both of which were seated in a pressurised cockpit located within the extreme nose of the aircraft and covered by a conventional canopy.[8][9] All of the flight surfaces were manually-actuated, although powered counterparts were envisioned for subsequent aircraft. A hydraulic system was used for some moving elements, such as the undercarriage and the flaps.[8] Being intended for use as a bomber, the (unbuilt) production aircraft were envisioned to be capable of carrying a bombload of up to 5,000 kg (11,000 lb); furthermore, it was planned to install remotely-controlled barbettes that would have been armed with a pair of 20 mm cannon on the wingtips.[10][1] The bomb bay would have been installed within the centre fuselage underneath the wing's central section. Despite its large size, the SO.4000's total fuel capacity was 1,430 gallons, which would have severely restricted its operational range if the type had ever entered service.[3]

Variants

SNCASO M1

A scale unpowered glider for research into the flying characteristics of the full size S.O.4000. Launched from a support frame above the fuselage of the sole Heinkel He 274, which had been abandoned in France and restored to airworthiness to support research programmmes, and/or a similarly equipped SE-161 Languedoc.

SNCASO M2

Essentially similar to the M1 but powered by a single 15.57 kN (3,500 lbf) Rolls-Royce Derwent V centrifugal flow turbojet engine. First flown on 13 April 1949.

SNCASO S.O.4000

A single prototype of this jet powered bomber first flown on 15 March 1951. Powered by 2 × 22.15 kN (4,980 lbf) Rolls-Royce Nene 102 centrifugal flow turbojet engines.

Specifications (Performance estimated)

Data from Plane Facts: An abortive bomber[5]

General characteristics

• Crew: 2
• Length: 19.75 m (64 ft 10 in)
• Wingspan: 17.86 m (58 ft 7 in)
• Wing area: 75.00 m² (807.3 sq ft)
• Empty weight: 16,583 kg (36,559 lb)
• Gross weight: 22,005 kg (48,513 lb)
• Powerplant: 2 × Rolls-Royce Nene 102 turbojet, 22.2 kN (4,980 lbf) thrust each

Performance

• Maximum speed: 850 km/h (530 mph, 460 kn) at 9,000 m (29,500 ft)
• Maximum speed: Mach 0.78

Armament

References

Citations

1. Gunston and Gilchrist 1993, p. 69.
2. Caygill 2006, .
3. Gunston and Gilchrist 1993, p. 68.
4. Griehl, Manfred; Dressel, Joachim (1998). Heinkel He 177 - 277 - 274. Shrewsbury, UK: Airlife Publishing. pp. 208–209. ISBN 1-85310-364-0.
5. Air International January 1986, p. 46.
6. "Le Sud-Ouest SO-4000: I. Origine". Le Sit des Projets et Prototypes d'Avions, 14 May 2003. Retrieved 15 May 2011.(in French)
7. "Le Sud-Ouest SO-4000: V. Essai et abandon du SO-4000". Le Sit des Projets et Prototypes d'Avions, 14 May 2003. Retrieved 15 May 2011.(in French)
8. Gunston and Gilchrist 1993, pp. 68-69.
9. Flight 12 May 1949, p. 552.
10. "Le Sud-Ouest SO-4000: II. Le NC-270 & le SO-4000". Le Sit des Projets et Prototypes d'Avions. 14 May 2003. Retrieved 15 May 2011.(in French)

Bibliography

• "An abortive bomber". Air International, January 1986, Vol 30 No 1. Bromley, UK: Fine Scroll. p. 46. ISSN 0306-5634.
• Caygill, Peter. Sound Barrier: The Rocky Road to MACH 1.0+. Pen and Sword, 2006. ISBN 1-47381-843-5.
• Gunston, Bill and Peter Gilchrist. Jet Bombers: From the Messerschmitt Me 262 to the Stealth B-2. Osprey, 1993. ISBN 1-85532-258-7.

External links

• Aviafrance (in French)
• A photograph of the SO.4000 F-WBBI