SNCASO SO.4000

The SNCASO SO.4000 was an experimental French twin-engine jet-bomber aircraft of the 1950s. Only a single example was built, which only made a single test flight before development was abandoned.

Design and development
The French Air Force drew up a requirement for a jet bomber shortly after then end of the Second World War, with the new bomber expected to have a weight of about 25–30 tonnes and to fly at high-subsonic speeds. Designs were tendered by SNCASO, the SO 4000 and by SNCAC, the SNCAC NC 270, which resulted in SNCASO receiving an order for two manned scale models, the first, the SNCASO M.1 - an unpowered glider which would be tested from atop the first prototype of the Heinkel He 274 which had remained in France post-war and restored to flightworthiness by the French, while the SNCASO M.2 was powered by a single Rolls-Royce Derwent, and a full-size prototype, as did SNCAC.

The SO.4000 had a mid-mounted wing swept at an angle of 35 degrees, and had a carefully streamlined oval section fuselage accommodating two 22.2 kN (4,980 lbf) Rolls-Royce Nene engines mounted side-by-side in the rear fuselage, while it was fitted with a tall tricycle landing gear with tandem mainwheels. The crew of two sat in a pressurized cockpit in the extreme nose of the aircraft. The aircraft was designed to carry a bombload of up to 5,000 kg (11,000 lb), while it was planned to fit remotely controlled barbettes carrying two 15 mm cannon on the wingtips.

Although production plans were abandoned in 1947, it was decided to complete the two scale models and the full size prototype for experimental purposes. The M.2 made its maiden flight on 13 April 1949, with the M.1 glider making its first free-flight, launched from a SNCASE Languedoc on 26 September 1949. Testing of the M.2 was successful, with it exceeding 1,000 km/h (621 mph) in a dive. The SO.4000 was rolled out on 5 March 1950, but was damaged when its undercarriage collapsed during taxi-tests on 23 April that year. After repair, it made its maiden flight on 15 March 1951, but its undercarriage failed again on landing, and the project was abandoned, with no more flight testing being carried out.

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 3500 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 × 4980 lbf Rolls-Royce Nene 102 centrifugal flow turbojet engines.