Editing Sud Aviation Caravelle (section)

===Origins===
On 12 October 1951, the ''Comité du matériel civil'' (civil aircraft committee) published a specification for a medium-range aircraft, which was later sent to the aviation industry by the ''Direction technique et industrielle''. This called for an aircraft capable of carrying 55 to 65 passengers and {{convert|1000|kg|abbr=on}} of cargo on routes up to {{convert|2000|km|nmi mi|abbr=on|lk=out}} with a cruising speed of about {{convert|600|km/h|kn mph|abbr=on|lk=out}}. The type and number of engines were not specified. Since 1946, various design studies for aircraft in this category had already been underway at several of the leading French aircraft manufacturing organisations, and had resulted in some ambitious concepts being mooted. None of these firms possessed the financial power to independently embark on the substantial development work involved, let alone to establish a manufacturing line for the construction of such aircraft.<ref name="López1"/><ref name = "doug 456"/>

The response to the specification from the French industry was strong, it has been claimed that every major manufacturer submitted at least one proposal; a total of 20 different designs were ultimately received. The majority of these proposals were powered by all-[[turbojet]] engine arrangements, although [[Breguet Aviation|Breguet]] had entered a number of designs that were powered by both turbojet and [[turboprop]] engines; among these was one for a [[Snecma Atar]]-powered tri-jet to be developed in association with the [[Nord Aviation|SNCA du Nord]] and a turboprop type; all of the different designs were designated as ''Br. 978''. [[Hurel-Dubois]] had entered several turboprop designs based on a narrow fuselage and shoulder-mounted wing, similar to many regional propliners. Proposals from [[SNCASO]] included the S.O.60 with two Rolls-Royce Avon RA.7 engines, outfitted with two smaller [[Turbomeca Marboré]]s as auxiliaries. SNCASE had also returned a number of designs from the X-200 to X-210, all of these being purely jet-powered.<ref name="López1"/>

On 28 March 1952, after studying the various entries, the ''Comité du Matériel Civil'' announced that it had produced a short list of three entrants: the four-engined Avon/Marbore SNCASO S.0.60, the twin-Avon Hurel-Dubois project, and the three-engined Avon SNCASE X-210. At this point, British engine manufacturer [[Rolls-Royce Limited|Rolls-Royce]] had already begun to offer a new version of the Avon that was to be capable of developing 9,000&nbsp;lbf (40&nbsp;kN) of thrust, which would render the auxiliary engines of the S.O.60 and the third engine featured on the X-210 unnecessary.<ref name="López1"/> The Committee issued a request for SNCASE to re-submit its X-210 proposal as a twin-Avon design.<ref name = "doug 456"/> In doing so, SNCASE decided to not remove the remaining engines from their rear-mounted position; most designs had placed the engines underneath the wing, where they could be mounted on the spar for lower overall weight, but it was felt that these weight savings were not worth the effort. This turned out to be a benefit to the design, as the cabin noise was greatly reduced as a result. In July 1952, the revised X-210 design with twin Avons was re-submitted to the [[Secretariat General for Civil and Commercial Aviation]] (SGACC).<ref name="López1"/>