In September 1945, the French Air Force's High Command issued a very ambitious programme for the French industry of the time.
The specifications for that bomber were that it should weight 25 to 28 tons at maximum with a payload of, at least, 5 tons of bombs with a maximum range of 3000km (1864milles) with a minimum speed of 900km/h (559mph) at 9000metres (29527ft) of altittude. It should've been powered by two British-built Rolls-Royce Nene engines. All evidence point that it was going to be underpowered.
Two French companies presented their projects in March 1946, the Sociétés Nationales de Constructions Aéronautiques (Aérocentre-SNCAC) and Sud-Ouest (SNCASO) with the N.C.270 and the SO.4000 respectively.
The fuselage was circular with a fuel deposit in the upper part and the bomb compartment that could carry up to 5 tons of bombs in the lower side. The two Rolls-Royce Nene engines were to be installed at the sides of the fuselage.
The cockpit was going to be located at the front and was integrated with the fuselage in order to erase any drag and make it completely aerodynamical. The expected crew of two, one pilot plus one navigator/bomber would have acceded through a hatch located in the ventral part of the aircraft and it would've had a defensive remotelly-controlled turret with four 20mm guns located at the back, behind the tail. It would've had a trycicle landing gear with a main wheel retracting into the main fuselage and two smaller one retracting into the jet engines.
At the end of 1946, the construction of the N.C.270 prototype was going to be started after having tested with a 1/25 scale model of the aircraft attached to a SNCASE SE.161 Languedoc transport aircraft. At the factory of Boulogne-Billacourt, close to Paris, the engineers that designed the bomber realized that they had overstimated the power of the jet engines and therefore it was obvious that the power of the Rolls-Royce Nene engines was highly insufficient for an aircraft of those characteristics. Furthermore, the price of the project was highly understimated and therefore the project seemed to be a financial failure both for Aérocentre and the French Air Force.
The project was subsequently classified as "not prioritaire" and, in October 1947 the technical direction of Aérocentre abandoned definitely the project of the N.C.270 but retained the scale models in order to perform experimental aerodynamic testings.
According to some sources, Aérocentre continued on to build unofficially the prototype until June 1949 when they went bankrupt and shut down. It seems that the prototype was 60% to 85% complete. Anyway, the company was bought by SNECMA -Safran Aircraft Engines- and Aérocentre's factories were reconfigured to manufacture Renault piston engines.
Sources:
1. https://fr.wikipedia.org/wiki/SNCAC_NC.270 (translated)
2. http://aerophile.over-blog.com/article-les-projet-secret-de-la-sncac-premiere-partie-104222679.html (translated)
