page_title: Dassault Mercure
section_title: Design
hierarchical_section_title: Dassault Mercure / Design
caption_attribution_description: English: diagram of production parts of Dassault Mercure
context_page_description: The Dassault Mercure is a twin-engined narrow-body jet-powered airliner developed and manufactured by French aircraft firm Dassault Aviation. According to Dassault, it was the first large-scale European cooperative civil aeronautics programme.
  During 1967, the Mercure was proposed as a French counterpart to the American Boeing 737. It was Dassault's first venture into the commercial jet airliner market, the company having traditionally built fighters and executive jets. On 28 May 1971, the prototype conducted its maiden flight, while the type entered service on 4 June 1974 with French airline Air Inter.
  Attempts were made to market the type in the US, including partnerships with American manufacturers Douglas, Lockheed and General Dynamics, with the vision of producing it in the United States. However, the Mercure had very little success on the market, which has been attributed to several factors, including a lack of range in comparison to rival aircraft. As a consequence, there were only 12 aircraft constructed, all of which were built between 1971 and 1975. The Mercure performed its final flight in 1995.
context_section_description: The Dassault Mercure was a jet-powered narrow-body jet airliner, optimised for short-haul routes. It intentionally exchanged fuel for passenger capacity in order to carry a greater passenger load; as such, the Mercure had up to 17 per cent more seats than the competing Boeing 737 while having a shorter range. It was designed to be outfitted with a two-crew flight deck, although operator Air Inter had its aircraft flown by three-man crews. According to Flight International, the basic model of the Mercure featured a degree of built-in stretch potential; elements of the design were reportedly capable of supporting the envisioned expanded model with little or no change, including much of the wing, cabin, and the undercarriage, the latter being spaced in order to accommodate the fitting of longer legs to in turn enable larger engines and an elongated fuselage to be later adopted.
  The wing of the Mercure was largely conventional; it was relatively thick, possessing a section of 12.5 per cent thickness at the wing root, slimming to 8.5 per cent thickness at the tip of the wing. Aspects of the Mercure's wing, such as the general layout and individual wing sections, were optimised using a combination of wind tunnel tests and computer-generated simulations by Dassault's design team. The wing had a good lift/drag ratio and a high block efficiency; the flaps formed a continuous spanwise unit when deployed in the take-off position, neither low-speed ailerons or cut-outs to accommodate jet exhaust due to the engines have been fixed low down upon deep pylons.
  Production Mercures were powered by a pair of Pratt & Whitney JT8D-15 turbofan engines, capable of generating a maximum of 15,500 lb (69 kN) thrust. These were mounted on underwing pylons, which were designed with anti-vibration mountings; the engines themselves featured joint Snecma/Dassault-developed thrust reverser and noise suppression system. Significant attention had been paid to reducing engine noise, this issue having been one of the final topics of research during the Mercure's development; according to Flight International, there was a perception that the Federal Aviation Administration of the United States, a major potential market for the Mercure, may enact regulations that would necessitate the implementation of a noise-attenuation retrofit programme, and thus Dassault needed to be prepared to address this foreseen scenario.
  Dassault emphasised the commercial value of the Mercure, highlighting its low operating costs across short sectors, which principally resulted from its refined aerodynamic features and low structural weight. The design also benefitted from an advanced fail-safe structure, the majority of which having been milled in accordance to Dassault's traditional military manufacturing practices. The Mercure featured in-house-developed triplicated, fail-safe hydraulic flight control system; the flight controls lacked any manual reversion. Air conditioning also featured independent duplicated systems with a cross-feed tapped from the engines compressors along with, unusually, the auxiliary power unit for use during takeoffs and on the ground, as well as in the instance of a double-engine failure scenario. The electrics were composed of a pair of independent 120/128 volt three-phase 400 Hz AC systems fed via engine-driven alternators, while a third AC system was driven by the APU; in addition, there are three independent 28 volt DC sources.
caption: Diagram of partners involved at the beginning in the project, for the first prototype. During production, Fiat reduced its involvement.
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