Dassault Mercure

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. The Mercure 100 was the first commercial airliner operated by an entirely female crew.

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 having been built between 1971 and 1975. The Mercure performed its final flight in 1995.

Development

Origins
During the mid-1960s, Marcel Dassault, the founder and owner of French aircraft company Dassault Aviation, as well as other parties such as the French Directorate General for Civil Aviation (DGAC), examined the civil aviation market and noticed that there was no existing aircraft that was intended specifically to serve low-distance air routes. Thus, it was found that there could be a prospective market for such an airliner, if it were to be developed. The DGAC was keen to promote a French equivalent to the popular American Boeing 737, and suggested the development of a 140-seat airliner to Dassault.

In 1967, with the issuing of backing by the French government, Dassault decided to commence work on its short-haul airliner concept. During 1968, the initial studies performed by the company's research team were orientated around a 110 to 120-seat airliner which was powered by a pair of rear-mounted Rolls Royce Spey turbofan engines; as time went on, a specification for a 150-seat aircraft with a 1000-km range (540 nm) was developed. As envisioned, the new airliner would attack this market segment at the upper end with a 140-seat jetliner, contrasting against the 100-seat Boeing 737-100 and the 115-seat Boeing 737-200 variants then in production. In April 1969, the development programme was officially launched.

This aircraft was viewed as being a major opportunity for Dassault to demonstrate upon the civilian market its knowledge of high-speed aerodynamics and low-speed lift capability that had previously been developed in the production of a long line of jet fighters, such as the Ouragan, Mystère and Mirage aircraft. The French Government contributed 56 per cent of the programme's total development costs, which was intended to be repaid by Dassault via a levy on sales of the airliner, the company also financed the initiative with $10 million of its own money, as well as being mainly responsible for costs related to manufacture.

According to aerospace publication Flight International, the design of the new airliner had been shaped by Dassualt's "philosophy of aiming the aircraft at a corner of the market which it believes existing types do not adequately serve". Marcel Dassault decided to name the aircraft Mercure (French for Mercury). "Wanting to give the name of a god of mythology, I found of them only one which had wings with its helmet and ailerons with its feet, from where the Mercure name.." said Marcel Dassault. Extremely modern computer tools for the time were used to develop the wing of the Mercure 100. Even though it was larger than the Boeing 737, the Mercure 100 was the faster of the two. In June 1969, a full scale mockup was presented during the Paris Airshow at Le Bourget Airport. On 4 April 1971, the prototype Mercure 01 rolled out of Dassault's Bordeaux-Merignac plant.

On 28 May 1971, the maiden flight of the first prototype, powered by a pair of Pratt & Whitney JT8D-11 turbofan engines, capable of generating up to 6800 kg of thrust, took place at Mérignac. On 7 September 1972, the second prototype, which was powered by a pair of Pratt & Whitney JT8D-15 engines, which would be used on all subsequent Mercures built, flew for the first time. On 19 July 1973, the first production aircraft conducted its maiden flight. On 12 February 1974, the Mercure received its Type certificate and, on 30 September 1974, was certified for Category IIIA approach all-weather automatic landing (minimum visibility = 500 ft, minimum ceiling = 50 ft). The Mercure 100 was also the first commercial airliner to be operated by a 100% female crew on one of its flights.

Dassault tried to attract the interest of major airlines and several regional airlines, touting the Mercure 100 as a replacement for the Douglas DC-9. A few airlines showed some initial interest but only Air Inter, a domestic French airline, placed an order. This lack of interest was due to several factors, including the devaluation of the dollar and the oil crisis of the 1970s, but mainly because of the Mercure's operating range – suitable for domestic European operations but unable to sustain longer routes; at maximum payload, the aircraft's range was only 1,700 km. Consequently, the Mercure 100 achieved no foreign sales. With a total of only ten sales with one of the prototypes refurbished and sold as the 11th Mercure to Air Inter, the airliner represented one of the worst failures of a commercial airliner in terms of aircraft sold.

Further development

After the commercial failure of the Mercure 100, Marcel Dassault requested of his engineers to develop a new version of the Mercure, the Mercure 200C, in cooperation with Air France. The variant was to carry a maximum of 140 passengers across a range of 2,200 km. Several major airlines in the United States showed some interest in the project. However, the project's design costs were also high. This might have been mitigated if the original Mercure had had a larger fuel capacity or sufficient design strength so that additional fuel tanks could have been easily added.

At the beginning of 1973, an agreement was formed with the French government to finance this programme. Dassault was to receive a loan of 200-million French Francs from the French government, which would be paid back based on sales after the 201st aircraft was delivered. However, by this point, Air France sought an airliner that was powered by the Pratt & Whitney JT8D-117 engine, which was quieter and larger than the older JT8D-15. Dassault needed an additional loan of 80-million French Francs from the government to accommodate Air France's request. The French government replied to Dassault that it had to carry half of the development costs of the Mercure 200C on their own, which was impossible after the commercial failure of the Mercure 100. As a consequence, the Mercure 200C project was canceled.

Later, in order to answer a request from the DGAC (Direction Générale de l'Aviation Civile, the French civil aviation authority), Dassault proposed a Mercure equipped with a new engine developed by General Electric/Snecma called the CFM International CFM56; this version came to be known as the Mercure 200. In 1975, contacts were made with Douglas and Lockheed to build and sell the Mercure 200 in the US, and with SNIAS to build it in France. However, Marcel Dassault was concerned about the fact that the CFM56 had not had a single order yet, and production might end before the Mercure 200 could be built. Meanwhile, Douglas proceeded to introduce a stretched version of the DC-9, which was in direct competition for orders with the Mercure 200; accordingly, contacts with Douglas were terminated shortly thereafter. Dassault then initiated contacts with another American manufacturer, General Dynamics, who was at the time their primary competitor in the military jet market, where the Dassault Mirage F1 was facing the F-16 Fighting Falcon. Nothing would come out of these contacts.

Design

The Dassault Mercure was a jet-powered narrow-body jet airliner, optimised for short-haul routes. It intentionally exchanged capacity for fuel in order to carry a greater passenger load; as such, the Mercure had up to a 17 per cent greater seating capacity 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.

Operational history

Intending for the Mercure to be mass-produced in substantial numbers (According to Flight International, the 300th aircraft was projected to be delivered by the end of 1979), Dassault established a total of four plants especially for the Mercure program: Martignas (close to Bordeaux), Poitiers, Seclin (close to Lille) and Istres. Additional manufacturing work was distributed across locations throughout Europe, the production programme being a collaborative effort between Dassault, Fiat Aviazione of Italy, SABCA (Société Anonyme Belge de Constructions Aéronautiques) of Belgium, Construcciones Aeronáuticas SA (CASA) of Spain and the Swiss National Aircraft Factory at
Emmen, all of which acted as risk-sharing partners in the venture.

On 30 January 1972, Air Inter placed an order for ten Mercures, which had to be delivered between 30 October 1973 and 13 December 1975. At this point, the break-even point was anticipated to be around 125–150 aircraft. However, due to the lack of other orders, the production line was shut down on 15 December 1975. Only a total of two prototypes and ten production aircraft were built. One of the prototypes (number 02) was eventually refurbished and purchased by Air Inter to add it to its fleet.

On 29 April 1995, the last two Mercures in service flew their last commercial flights. Throughout their combined cumulative operational lifetimes, the Mercure accumulated a total of 360,000 flight hours, during which 44 million passengers were carried across 440,000 individual flights without any accidents occurring, and a 98% in-service reliability.

Operators

 Air Inter
 Ecole Supérieure des Métiers de l'Aéronautique used fifth produced Mercure (registered F-BTTE and painted in fictional Air Littoral colours), as a ground instructional airframe.

Survivors

 F-BTTB, c/n 2 is on display at the Technik Museum Speyer in Germany. The cabin of the aircraft although closed to the public can be seen through a grille. It is presented in the same condition as it left service (on its last commercial flight), complete with French magazines on the passenger seating.
 F-BTTD, c/n 4 is on display at the Musée de l’air et de l’espace at Paris–Le Bourget Airport in France.
 F-BTTE, c/n 5 is preserved as an instructional airframe at Montpellier–Méditerranée Airport.
 F-BTTF, c/n 6 is stored at Bordeaux–Mérignac Airport in France.
 F-BTTH, c/n 8 is preserved at Marseille Provence Airport.
 F-BTTI, c/n 9 is preserved as an instructional airframe at Bordeaux–Mérignac Airport in France.
 F-BTTJ, c/n 10 is preserved at the Musée Delta in Athis-Mons, near Paris-Orly Airport.

Specifications

See also

References

Notes

Bibliography

 "Air Transport". Flight International, 22 April 1971, pp. 538–540.
 Middleton, Peter. "Dassault Mercure". Flight International, 20 May 1971, pp. 721–726.
 Taylor, John W. R. Jane's All The World's Aircraft 1976–77. London: Jane's Yearbooks, 1976. .
 Uijthoven, René L. "An 'Airbus' Before Its Time: Dassault's Mercure Airliner". Air Enthusiast, No. 115, January/February 2005, pp. 70–73. Stamford, UK: Key Publishing.

External links
 YouTube video of an Air Inter Mercure
 Safety card of an Air Inter Mercure

Mercure
Category:1970s French airliners
Category:Low-wing aircraft
Category:Twinjets
Category:Aircraft first flown in 1971