Design Origins
Though the short-range, low-capacity phase of the market was saturated with twin-jet designs, inclusive of the Sud-Aviation SE.210 Caravelle, the British Plane Company BAC-111, the McDonnell-Douglas DC-9, the Boeing 737, and the Fokker F.28 Fellowship, Dassault-Breguet believed {that a} bigger twin, accommodating not less than 150 passengers and working over sectors not than 932 miles, was wanted to fill the hole between these different designs and the 336-passenger Airbus A300.
Market research performed in 1968 indicated the necessity for as many as 1,500 plane on this class throughout the subsequent 9 years. Of the present sorts, solely the Caravelle 12 and the DC-9-50 accommodated 130 single-class passengers in high-density configurations, whereas the others carried significantly fewer. The BAC 1-11-200, as an example, had a capability of solely 89, and the F.28, even in its final stretch because the F.28-4000, accommodated 5 fewer. Dassault-Breguet’s supposed airliner was seen as an early Airbus, economically working short-range, high-density routes, similar to these between France’s main inhabitants facilities.
Not like 4 of those 5 different twin-jets, its personal configuration, ensuing from a number of sizes and design options, was a standard low-wing monoplane with a fuselage large sufficient, like that of the 737, for six-abreast coach seating, two pylon-mounted engines, and an equally typical tailplane. Its total look, in actual fact, was very a lot a mirror picture of that 737, besides that its turbofans have been hung decrease and forward of the wing, versus Boeing’s underside attachment association, and its fuselage was longer to allow six extra six-abreast seat rows to be put in.
Undertaking go-ahead was contingent upon receipt of not less than 50 agency orders for the finally named “Mercure,” or “Mercury,” however solely Air Inter, the French home service, dedicated itself to 10 on 29 January 1972. So satisfied was Dassault-Breguet of the integrity of its design and the world market’s want for it that it launched this system on the premise of a single airline order.
The French authorities coated 56 % of the launch prices, with 14 % borne by Dassault-Breguet itself and the rest by its 5 risk-sharing companions, which included Aeritalia of Italy, Canadair of Canada, CASA of Spain, the Eidgenössisches Flugzeugwerk of Switzerland, and SABCA of Belgium. Every was chargeable for components and programs manufacture: Aeritalia, the tail unit and the tailcone; Canadair, the wing panels, the forefront, the flap tracks, and the engine pylons; CASA, the primary and second fuselage sections; Eidgenossisches Flugzeugwerk, the engine air intakes and the cowling panels; and SABCA, the flaps, the spoilers, the ailerons, and the airbrakes. Closing meeting would happen on the Bordeaux-Merignac manufacturing plant in Southern France.
Mercure Design Options
The Mercure 100 in its preliminary—and, within the occasion, solely—model featured an all-metal, five-section, semi-monocoque fuselage of round cross-section large sufficient for six-abreast coach seating and measuring 112.11 ft in size, giving the plane an total size of 114 ft 3.5 inches. Of the 5 different low-capacity, short-range twin-jets, solely the Boeing 737 provided ample width for this configuration.
The airframe was designed for 30,000 flight cycles and 40,000 airborne hours.
The low-set wings, whose two-spar torsion bins have been comprised of a steady spar, eight pores and skin panels, stiffeners, and machined ribs, have been geared up with three-section out- and downward-extending forefront slats (versus the 5 fitted to the prototype), two-section triple-slotted trailing edge flaps, an aileron, three spoiler panels, and two airbrakes. All have been hydraulically operated by twin actuators, which have been themselves fed by three unbiased circuits.
The spoilers, interrupting elevate upon main-wheel spin-up, operated at the side of the aileron in flight to supply lateral management.
The 100.3-foot wingspan, leading to a 1,250-square-foot space, featured a 25-degree sweepback, producing a 96.25 pounds-per-square-foot loading. Different wing floor areas included the trailing edge flaps (261.6 sq. ft), the ailerons (45.2 sq. ft), the spoilers (49.5 sq. ft), and the velocity brakes (36.6 sq. ft).
Wing main edges have been deiced via engine bleed air.
The standard tailplane, once more just like the 737’s, consisted of two-spar horizontal and three-spar vertical surfaces, leading to a 37-foot, 3.25-inch total plane peak. The previous, mounted with three levels of dihedral and of the variable-incidence kind, had a 41.11-foot span and a 257.3-square-foot space with 86.1 sq. ft of hinged, hydraulically actuated elevators. The 166.3-square-foot fin was provisioned with a 64.1-square-foot, hydraulically-operated, dual-section rudder.
Energy was supplied by two nacelle-encased, sound absorption-treated, thrust reverser-equipped, 15,500 thrust-pound Pratt and Whitney JT8D-15 low (1:1) bypass ratio turbofans pylon-mounted to the wing forefront underside. Not like the direct-wing underside association of the 737, the configuration positioned the engine beneath and forward of the airfoil, necessitating an extended undercarriage strut. A number of variations of the engine powered the Boeing 727, higher-capacity Caravelle variants, the DC-9, and the 737 itself.
Gasoline, whose capability was 4,860 US gallons, was launched on the starboard wing’s outer forefront, with extra factors on the precise floor. Oil capability was 11.9 US gallons.
The Mercure 100 rested on a hydraulically-operated, twin-wheeled undercarriage consisting of Kleber-Colombes tires, Messier-Hispano wheels, oleo-pneumatic shock absorbers, Messier-Hispano brakes, and antiskid items. The nostril gear, with a tire dimension of 30 x 8.8 and a strain of 123 psi, was steerable and retracted ahead. The principle gear, whose tire dimension was 46 x 16 and whose strain was 141 psi, retracted laterally into the wing and fuselage wheel nicely fairings. The undercarriage could possibly be manually prolonged within the occasion of a hydraulic failure.
Nostril wheel steering and monitor enabled the plane to be turned 180 levels on the bottom on a 70-foot-wide floor.
Entry was supplied by 71-by-33-inch ahead and aft port-side doorways, the primary of which was standardly geared up with an extendible, lighted, handrail-provisioned airstair, and the second of which could possibly be optionally geared up with one. The ahead and aft, starboard-side galley-servicing counterparts measured 71-by-33- and 65-by-33-inches, respectively. 4 39.4-by 20-inch overwing emergency exits, two on all sides, facilitated egress.
Though the Mercure 100 was standardly operated by a two-person crew, two extra observer seats have been supplied. Imaginative and prescient was by way of two ahead and 4 aspect home windows, in addition to two eyebrow panes. Incorporating expertise designed for Dassault-Breguet’s well-known fighters, it was provisioned with a head-up show, lowering the time between sky scanning and instrument monitoring for extra fast management and corrective motion, if required.
Three 3,000-psi unbiased hydraulic programs powered the first and secondary flight controls. The primary two, pushed by Abex engine-driven pumps, powered the modern slats, trailing-edge flaps, spoilers, tailplane, nose-wheel steering, undercarriage, and brakes. The third, powered by a Vickers electrically pushed pump, supplied backup energy to the ailerons, elevators, and rudder.
The 83.7-foot-long, 11.11-foot-wide, and 7-foot-2.75-inch-high cabin, with an 882-square-foot flooring space and 5,717-cubic-foot quantity, was each wider and longer than that of any twin-jet as much as that point and thus facilitated quite a few class divisions, seat pitches, and seat densities. This flexibility was additional enhanced by its rectangular, carefully spaced, polarized, light-filtering passenger home windows and the 4 ahead and aft entry doorways.
Cabin Format and Passenger Configuration
Initially outfitted with a large cabin look, it featured a flat ceiling with recessed, subtle lighting; particular person, upward-opening overhead storage compartments for carry-on baggage; and paneled sidewalls. Galleys, toilets, and garment closets could possibly be put in in 11 places. The galleys themselves could possibly be merely or extensively provisioned with ovens, refrigeration items, espresso makers, storage compartments, counters, waste receptacles, and meal and beverage carts, and will serve something from an aperitif to a sizzling meal acceptable to the time of day.
Set up and the variety of items included the ahead, proper aspect (two items), the ahead, left aspect behind the passenger door (two items), the aft, proper aspect forward of the servicing door (two items), the aft, left aspect forward of the passenger door (one unit), and the aft, proper aspect behind the servicing door (one unit).
Bathrooms, which standardly consisted of a lockable door, a chrome sink and counter, dispensers for tissues, cups, and bathroom paper, a lighted mirror, and a recirculating bathroom, may equally be put in in quite a few places, together with on the ahead, proper aspect behind the servicing door; on the ahead, left aspect behind the passenger door; on the aft, left aspect earlier than the passenger door; on the aft, left aspect behind the passenger door; and on the aft, proper aspect behind the servicing door.
Garment storage closets is also put in in seven ahead and aft places.
Seating densities, configurations, upholstery, coloration, and design, like galley, bathroom, and garment closet places, various based on buyer specification, however every seat itself was provisioned with a seatbelt, an ashtray, a pull-down tray desk, and a literature pocket. Every additionally reclined.
A dual-class, 120-passenger association entailed 12 four-abreast first-class seats at a 38-inch pitch, their pairs spanning 54 inches in width and thus allowing a 31-inch aisle, and 108 six-abreast coach ones at a 34-inch pitch, their triples spanning 61 inches and the resultant aisle measuring 17 inches in width.
A dual-class, 132-passenger configuration consisted of 12 first-class seats at a 38-inch pitch and 120 at a 34-inch pitch, however the extra capability was achieved by relocating or eradicating galley, bathroom, and/or garment storage closet services.
A world, single-class association entailed 135 to 140 six-abreast seats at a 34-inch pitch, whereas its single-class home counterpart elevated the capability to 150 at a 32-inch pitch. The kind’s most single-class capability was 162 at a 30-inch pitch, which was 32 greater than the comparable 737-200’s and 23 greater than both the Caravelle 12’s or the DC-9-50’s.
Garett air-con and Hamilton Normal pressurization programs, utilizing engine bleed air, produced an 8.3-psi cabin differential.
Baggage, cargo, mail, and dwell animals have been carried in three lower-deck holds.
The primary two compartments may accommodate 5 and 4 727-type cargo containers, respectively, whereas the third accepted solely bulk or free masses. All have been heated, lighted, and pressurized, and housed oxygen and potable water provide tanks, in addition to bathroom waste receptacles. A powered loading system could possibly be optionally put in.
The Mercure 100 provided the next weights: an empty working weight of 70,039 kilos, a payload of 32,850 kilos, a most ramp weight of 121,250 kilos, and a most takeoff weight of 120,150 kilos.
Weights for export plane—that’s, these ordered by carriers aside from Air Inter—differed, as follows: a most zero-fuel weight of 105,820 kilos, a most ramp weight of 125,660 kilos, and a most takeoff weight, after taxi gas consumption, of 124,560 kilos.
Efficiency and Payload Limitations
Fulfilling its design objectives, the Mercure 100 provided a better payload, a better passenger capability, and extra cargo maintain quantity than any earlier twin.
It was additionally in a position to transport extra passengers for its weight than every other twin-jet, attaining superior working effectivity.
Solely the 727-200, which was additionally powered by the JT8D engine, may exceed the Mercure 100’s capability with 169 passengers, however at a significantly increased common weight of 145,000 kilos and with an extra powerplant.
The Mercure 100 additionally provided the bottom gas burn per passenger on a typical 630-nautical-mile European sector when working at its long-range cruise velocity at 33,000 ft with a 137-mile diversion allowance.
These comparisons point out 4 primary design superiorities.
The best gas mileage per seat of all jetliners carrying fewer than 250 passengers.The best common velocity of all short- to medium-range industrial plane.The bottom empty weight per seat.The best payload of all twin-jets weighing lower than 200,000 kilos.
Optimized for brief flight instances, the Mercure 100 coated 500 nautical mile segments in 5 to fifteen minutes lower than comparable twins due to its excessive climb, cruise, and descent charges. Mixed with its fast turnaround functionality, these efficiency figures facilitated excessive every day utilization charges.
The plane required a 4,630-foot runway for touchdown based mostly upon a 136-mph (118-knot) strategy velocity and a 109,790-pound most touchdown weight.
Constructed for Quick Turnarounds
Quick turnaround instances have been made doable by a tailcone-installed Garrett-AiResearch GTCP-85-163C auxiliary energy unit (APU) that supplied floor energy for cabin conditioning, engine beginning, and an emergency electrical provide; the ahead, left (and non-obligatory aft, left) Aerozur airstair; and the starboard aspect galley servicing and decrease deck baggage and cargo maintain entry doorways. As a result of sectors have been quick, galley servicing and cabin cleansing have been restricted. And whereas the plane could possibly be refueled in ten minutes, its excessive takeoff-to-landing weight ratio enabled it to function a number of sectors earlier than refueling was required.
Turnaround instances thus various from 10 to fifteen minutes at intermediate stops and from 20 to 25 minutes at terminating factors, the place extra intensive provisioning was required.
Plane at their most gross weight required a 6,300-foot runway for takeoff and will climb at 3,300 fpm.
Regardless of these seemingly superior design capabilities, the kind’s major deficiency was its payload-range inflexibility. On a typical Air Inter flight with 150 passengers cruising at Mach 0.78 and at 32,000 ft with a 200 nautical mile diversion allowance, as an example, the Mercure 100’s vary was solely 800 nautical miles. Solely payload restrictions would have elevated this—to 1,200 miles with a 25,000-pound payload and 1,600 miles with a 21,000-pound payload—thereby rendering it unable to take advantage of its passenger-cabin-and-cargo-hold benefit on routes that exceeded short-range ones.
First Flights
The primary Mercure 100 prototype, designated 01 and registered F-WTCC, first flew from Bordeaux on 28 Might 1971, powered by two 15,000-thrust-pound Pratt & Whitney JT8D-11 turbofans, however included a shorter fuselage than that supposed for manufacturing variations.
As a result of efficiency proved beneath design targets, it was retrofitted with 15,500-thrust-pound JT8D-15s and returned to the sky 4 months later, on 7 September. However the extra energy did little to enhance its poor low-speed dealing with traits, which have been, partly, remedied by including horizontal stabilizer dihedral, leaving it to fly once more, now on this configuration, nonetheless two months later, on 18 November.
The second prototype, 02, and registered F-WTMD, joined the flight check program the next yr on 7 September. The upper-thrust engines and the tailplane dihedral, together with full-span modern slats, delivered the supposed efficiency.
The primary manufacturing model of the Mercure 100, supposed for launch buyer Air Inter and incorporating all of those modifications, together with the full-length fuselage, first flew from the brand new Istres manufacturing plant on 17 July 1973, and was awarded its French kind certificates the next yr on 12 February.
Air Inter Service
Air Inter took supply of the primary of its ten plane on 16 Might, integrating the kind into its shuttle-type French home route community. It acquired its second instance seven days later, on 11 June.
Of the ten ordered, the primary six have been delivered in 1974, and the remaining 4 the next yr, alphabetically registered F-BTTA by way of BTTJ.
Though its first 4 plane have been solely provisioned with Class II touchdown functionality, its remaining six featured the upgraded Class III normal, enabling them to conduct approaches with a 500-foot runway visible vary (RVR) and a 50-foot resolution peak (DH). The preliminary 4 have been subsequently introduced as much as this functionality.
Accommodating 150 passengers in a single-class, six-abreast, 3-3 configuration with 32-inch seat pitches, its ten Mercure 100s have been nicely acquired by passengers and operated a number of every day spherical journeys between a dozen French home cities and cities, with sectors starting from 50 to 70 minutes, demonstrating its speedy turnaround functionality.
Its capability, nonetheless, proved extreme relative to demand. Decrease-than-anticipated load elements, together with escalating gas costs, sarcastically prompted Air Inter to finally purchase a fleet of Sud-Aviation Caravelle 12s, working them on lots of the similar routes, however with decrease prices. Though it briefly flirted with the concept of promoting its Mercures, the French authorities mandated their continued operation, however supplied a subsidy to take action.
Structurally, nonetheless, the Dassault-Breguet airliner was sound and provided technological comparability to different twin-jets.
In the course of the first 5 years of operation, the ten Mercure 100s logged greater than 90,000 hours, comprising some 100,000 53-minute segments and attaining a median dispatch reliability of 98.5 %. Every plane operated eight to 10 every day flights.
Geared up with a totally monitored computerized pilot and head-up instrument shows, they performed Class IIIA landings in poor climate situations and nonetheless achieved a 98- to 99-percent reliability fee.
On 25 March 1985, Air Inter took supply of the second prototype, F-WTCC. Having already been provisioned with the longer fuselage, the higher-rated engines, the modern slats, and the tailplane dihedral, it was introduced as much as full manufacturing normal, giving Air Inter an 11-strong fleet.
Program Conclusion
As a result of no different service or operator ordered the Mercure 100, which, to a level, was designed for Air Inter’s frequent home route system, solely a dozen, together with the 2 prototypes, have been ever constructed. Though the design was an aerodynamic success and it was extraordinarily dependable in every day operations, it was a monetary failure for a number of causes.
Just like the Vickers VC10 and the Hawker Siddeley HS.121 Trident, which had respectively been designed for British Abroad Airways Company (BOAC) and British European Airways (BEA), it was geared towards Air Inter and its distinctive high-density, multiple-frequency, short-range home routes, a system which no different service maintained.Dassault-Breguet, maybe with out alternative, employed then-current expertise, incorporating the present Pratt and Whitney JT8D engines that powered different twin-jets, such because the DC-9, the 737, and the later variations of the Caravelle, and subsequently elected to make use of its thrust for payload and passenger capability slightly than vary.As a result of it launched the Mercure program late, these and different twin-jets had already captured a lot of the market and provided the mandatory payload and vary variations to take action. Whereas the last word stretches of the Caravelle, the DC-9, and the 737 resulted in most passenger capacities of 139, 139, and 130, respectively, their ranges have been considerably better, providing operators extra flexibility.Though market research for an Airbus-type plane have been correct, their timing was not. Solely after the Eighties was the 150-seat twin prevalent.Lastly, the Mercure 100’s working economics couldn’t be absolutely exploited if its extra capability was not crammed.
Whereas all of those elements led to the kind’s demise and resulted in its paltry manufacturing run, Dassault-Breguet formally attributed the rationale for its discontinuation as, “Fabrication stopped after completion of the tenth (manufacturing) plane because of the extraordinarily penalizing evolution of the US greenback alternate fee.”
Regardless of what was definitely a failure by many measures, the Mercure 100, whose final scheduled flight occurred on 29 April 1996, achieved an enviable operational document. Air Inter’s 11 plane carried some 44 million passengers, logging 360,000 airborne hours throughout 440,000 flights with a 98-percent dispatch reliability throughout their 22 years of service, by no means having brought on a single fatality.
