Featured image: Udo K. Haafke/GFDL 1.2

5/28/1971: First Flight of Dassault Aviation Mercure

DALLAS Today in aviation, Dassault Aviation Mercure took to the air for the first time from Bordeaux-Merignac Airport (BOD) in 1971. Onboard for the May 28 maiden flight were Dassault Aviation Chief Pilot, Jean Courot, co-pilot Jerome Resal, and test engineer Gerard Joyeuse.

The Mercure project was pushed by the Direction Générale de l’Aviation Civile (DGAC), the French Civil Aviation Authority. Marcel Dassault observed that, on a global basis, many routes were short-leg flights but no aircraft were adapted to this type of traffic. This opinion gave more credence to the program’s inception.

Marcel Dassault in front of Mercure02 bearing the colors of Air Inter. Photo: Dassault Aviation

Developing a Jumbo Challenger

The DGCA proposes to Dassault Aviation to take up a challenge: to compete with Boeing’s 737 by offering an upscale alternative, an aircraft capable of carrying 140 passengers. The first 1968 design was issued for a 110-120 seat aircraft, powered by two tail-mounted Rolls Royce Spee engines, but Dassault finally adopted a final project for a 150-seater with a range of 1000km.

The wings were developed with modern computing systems; the aircraft, larger than the Boeing 737, flies faster. It is finally powered by two Pratt & Whitney JT8 D15 turbofan engines, mounted under the wings, and is named Mercure (Mercury in English) by Marcel Dassault.

Marcel Dassault explains the choice of this name as “Wanting to give the name of a God of mythology I found only one who had wings on his helmet and fins on his feet, hence the name Mercure.”

Six-abreast cabin. Photo: By Konstantin von Wedelstaedt. Gallery page LPhoto, GFDL 1.2
Flight Deck. Photo: By Konstantin von Wedelstaedt – Gallery page LPhoto, GFDL 1.2

Program Launch

The final program is launched in April 1969, and fabrication starts, under Dassault’s project management, and is distributed among Italy’s Fiat, Spain’s CASA, Belgium’s ADAC, the Swiss Fabrique Fédérale d’Avions FW in Emmen, and Canada’s Canadair, becoming the first large European civil aviation cooperation program.

The final assembly takes place at the Dassault Aviation facility in BOD for the prototype while the final type assembly takes place in Istres (QIE), a military airport in South France. After its first flight at BOD, on June 2, 1971, the Mercure01 prototype flies to the Bourget Airport to take part in the 1971 Paris Air Show. It is its sixth flight and the ninth flight hour.

Dimensions and performances of the type are as follow. Engines: two Pratt & Withney JT8D-15 Turbofans, 7030kg (15500lb) thrust – Span: 30.55m – Lenght: 34.84m – Height: 11.36m – MTOW: 56500kg – Max speed: 935km/h, 503kt/h – Max ceiling: 6000m, 19685ft – Max range: 2070km, 1117nm – Max capacity: 150 passengers.

On display at the Musée de l’air et de l’espace at Paris–Le Bourget Airport. Photo: By ignis – Own work, CC BY-SA 3.0

Air Inter, Sole Operator

Air Inter placed an order for ten Mercures on January 30, 1972, with delivery dates from October 30, 1973, to December 13, 1975. The break-even point was estimated to be about 125–150 aircraft at this time. However, the production line was shut down on December 15, 1975, due to a lack of other orders.

There were only two prototypes and ten production planes completed. Air Inter (IT) subsequently bought and refurbished one of the prototypes (number 02) to add to its fleet.

The last two Mercures in operation conducted their last commercial flights on April 29, 1995. According to Dassault, the Mercure accrued a total of 360,000 flight hours over the course of their combined operating lifetimes, during which 44 million passengers were transported through 440,000 individual flights with no incidents and a 98 percent in-service reliability.

A Pratt & Whitney JT8D nacelle. Photo: By Mathieu Marquer from Paris, FRANCE – Réacteurs de mercure Uploaded by High Contrast, CC BY-SA 2.0

Other Opinions on the Mercure

Outside Dassault Aviation, opinions on the Mercure project were different. Too short, too small entering a market already conquered by the McDonnell Douglas DC9, the Boeing 737-100, or the British Aircraft Corporation BAC1-11, no one is willing to take this aircraft that, in the common opinion, can not be improved.

This negative opinion explains the changes adopted during the Mercure development with a new design, under-wing mounted engines instead of tail-mounted, new engines PW JT8 to replace the Rolls Royce Spey, an increased capacity that goes from an initial 86 o 110 seats to 136 as the final choice along with the possibility to load 3.3 tons of cargo.

The type’s performance was improved by modifying the engines’ pylons and moving their center of gravity backward, as well as changing the design of the horizontal tail surfaces to compensate for longitudinal instability. Once these changes were applied, the aircraft performed well, with the pilots finding the flight controls “remarkable.”

The toughest part of the venture was selling the aircraft. IT, operating only domestic stretches, was interested in the type, but negotiations with the flag carrier were much harder since Air France (AF) saw no interest in an aircraft with a maximum range of 2,070km (1,117nm), even when considering that the Mercure was equipped with an “all-weather landing system,” a must for IT CEO, Robert Vergnaud.

Air France finally decided against the Mercure, leaving IT as the sole Dassault Aviation customer for the Mercure project, a premier for Dassault more easily identified when speaking of Mystere, Mirage, or Rafale, a family of fighter aircraft, or corporate jets such as the Falcon types.

Marcel Dassault used to say, ” A nice plane will fly well…” but this feeling does not apply when trying to sell a nice plane, the Mercure commercial failure is there to prove it.

The featured image shows an Air Inter Dassault Mercure 100 on short finals at Marseille. Article source: Dassault Aviation. Musée de l’Air et Espace, Histaero.blogspot, Wikipedia

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