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DESIGN ORIGINS:
Though the short-range, low-capacity phase of the market was saturated with twin-jet designs, inclusive of the Unhappy-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 a minimum of 150 passengers and working over sectors now not than 932 miles, was wanted to fill the hole between these different designs and the 336-passenger Airbus A300.
Market research carried out in 1968 indicated the necessity for as many as 1,500 plane on this class in the course of the subsequent 9 years. Of the present varieties, 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-111-200, as an example, solely had a capability of 89 and the F.28, even in its final stretch because the F.28-4000, accommodated 5 fewer than this. Dassault-Breguet’s supposed airliner was seen as an early airbus, economically working short-range, high-density routes, resembling these between France’s main inhabitants facilities.
In contrast to 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 huge sufficient, like that of the 737, for six-abreast coach seating, two pylon-mounted engines, and an equally standard tailplane. Its general look, in actual fact, was very a lot a mirror picture of that 737, besides that its turbofans had 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 a minimum of 50 agency orders for the finally named “Mercure,” or “Mercury,” however solely Air Inter, the French home provider, dedicated itself to 10 on January 29, 1972. So satisfied was Dassault-Breguet concerning the integrity of its design and the world market’s want for it, that it launched this system primarily based upon the only airline order.
The French authorities lent 56 p.c of the launch prices, whereas 14 p.c was carried by Dassault-Breguet itself and the rest by its 5 risk-sharing companions, that included Aeritalia of Italy, Canadair of Canada, CASA of Spain, the Eidgenosisches Flugzeugwerk of Switzerland, and SABCA of Belgium. Every was answerable for elements and methods manufacture: Aeritalia, the tail unit and the tailcone; Canadair, the wing panels, the vanguard, 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. Remaining meeting would happen on the Bordeaux-Merignac manufacturing plant in Southern France.
MERCURE DESIGN FEATURES:
The Mercure 100 in its initial-and, within the occasion, only-version, featured an all-metal, five-section, semi-monocoque fuselage of round form huge sufficient for six-abreast coach seating and stretching 112.11 toes in size, giving the plane a 114-foot, 3.5-inch general size. Of the 5 different low-capacity, short-range twin-jets, solely the Boeing 737 supplied enough 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 containers had been comprised of a steady spar, eight pores and skin panels, stiffeners, and machined ribs, had been geared up with three-section out- and downward-extending vanguard slats, (versus the 5 fitted to the prototype), two-section triple-slotted trailing edge flaps, an aileron, three spoiler panels, and two airbrakes. All had been hydraulically operated by way of twin actuators, which themselves had been fed by three unbiased circuits.
The spoilers, interrupting elevate upon fundamental wheel spin-up, operated along side the aileron in flight with a view to present 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 trialing edge flaps (261.6 sq. toes), the ailerons (45.2 sq. toes), the spoilers (49.5 sq. toes), and the velocity brakes (36.6 sq. toes).
Wing main edges had been deiced by way of engine bleed air.
The traditional tailplane, once more much like the 737’s, consisted of two-spar horizontal and three-spar vertical surfaces, leading to a 37-foot, 3.25-inch general 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. toes 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 vanguard underside. Differing from 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, increased capability Caravelle variants, the DC-9, and the 737 itself.
Gas, whose capability was 4,860 US gallons, was launched on the starboard wing’s outer vanguard, 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, whose tire dimension was 30 x 8.8 and whose stress was 123 psi, was steerable and retracted ahead. The principle gear, whose tire dimension was 46 x 16 and whose stress was 141 psi, retracted laterally into wing and fuselage wheel nicely fairings. The undercarriage could possibly be manually prolonged throughout hydraulic failure circumstances.
Nostril wheel steering and observe 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 aspect doorways, the primary of which standardly featured an extendible, lighted, handrail-provisioned airstair and the second of which could possibly be optionally so geared up. The ahead and aft, starboard-side galley servicing counterparts respectively measured 71-by-33- and 65-by-33-inches. 4 39.4-by 20-inch overwing emergency exits, two on both sides, facilitated egress.
Though the Mercure 100 was standardly operated by a two-person crew, two extra observer seats had been supplied. Imaginative and prescient was via two ahead and 4 aspect home windows, in addition to two eyebrow panes. Incorporating know-how designed for Dassault-Breguet’s well-known fighters, it was provisioned with a head-up show, decreasing the time between sky scanning and instrument monitoring for extra fast management and corrective motion, if required.
Three 3,000-psi unbiased hydraulic methods powered the first and secondary flight controls. The primary two, pushed by Abex engine-driven pumps, powered the vanguard slats, the trailing edge flaps, the spoilers, the tailplane, the nostril wheel steering, the undercarriage, and the brakes. The third, powered by a Vickers electrically-driven pump, supplied backup energy for ailerons, the elevators, and the rudder.
The 83.7-foot-long, 11.11-foot-wide, and 7-foot, 2.75-inch excessive cabin, with an 882-square-foot ground 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 and seat pitches and densities. This flexibility was additional provisioned by its rectangular, closely-spaced, polarized, mild filtering passenger home windows and the 4 ahead and aft entry doorways.
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, bathrooms, and garment closets could possibly be put in in 11 areas. 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 rest room, may equally be put in in a lot of areas, 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 areas.
Seating densities, configurations, upholstery, colour, and design, like galley, bathroom, and garment closet areas, diversified 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 firstclass 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 entailed 12 firstclass seats at a 38-inch pitch and 120 at a 34-inch one, however the extra capability was achieved by both relocating or eradicating some galley, bathroom, and/or garment storage closet services.
A global, 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 methods, utilizing engine bleed air, produced an 8.3-psi cabin differential.
Baggage, cargo, mail, and reside animals had been carried in three lower-deck holds.
The primary two compartments may respectively accommodate 5 and 4 727-type cargo containers, whereas the third solely accepted bulk or free masses. All had been heated, lighted, and pressurized, and housed oxygen and potable water provide tanks and bathroom waste receptacles. A powered loading system could possibly be optionally put in.
The Mercure 100 supplied 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 aircraft-that is, these ordered by carriers apart 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 gasoline consumption, of 124,560 kilos.
Fulfilling its design objectives, the Mercure 100 supplied the next payload, a larger 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 another twin-jet, reaching 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 a further powerplant.
The Mercure 100 additionally supplied the bottom gasoline burn per passenger on a typical 630-nautical mile European sector when working at its long-range cruise velocity at 33,000 toes with a 137-mile diversion allowance
These comparisons point out 4 primary design superiorities.
1). The very best gasoline mileage per seat of all jetliners carrying fewer than 250 passengers.
2). The very best common velocity of all short- to medium-range industrial plane.
3). The bottom empty weight per seat.
4). The very best payload of all twin-jets weighing lower than 200,000 kilos.
Optimized for brief flight instances, the Mercure 100 lined 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 turn-around functionality, these efficiency figures facilitated excessive every day utilization charges.
The plane required a 4,630-foot runway for touchdown primarily based upon a 136-mph (118-knot) strategy velocity and a 109,790-pound most touchdown weight.
Brief turn-around instances had been made attainable 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-compulsory aft, left) Aerozur airstair; and the starboard aspect galley servicing and decrease deck baggage and cargo maintain entry doorways. As a result of sectors had been brief, the quantity of galley servicing and cabin cleansing was little. And, whereas the plane could possibly be refueled in ten minutes, its excessive takeoff to touchdown weight ratio enabled it to function a number of sectors earlier than this was required.
Flip-around instances thus diversified from 10 to fifteen minutes at intermediate stops and from 20 to 25 minutes at terminating factors the place extra in depth provisioning was wanted.
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 sort’s main deficiency was its payload-range inflexibility. On a typical Air Inter flight with 150 passengers cruising at Mach 0.78 and at 32,000 toes 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 one-rendering it unable to take advantage of its passenger cabin and cargo maintain benefit on routes that eclipsed short-range ones.
FIRST FLIGHTS:
The primary Mercure 100 prototype, designated 01 and registered F-WTCC, first flew from Bordeaux on Could 28, 1971 powered by two 15,000 thrust-pound Pratt and 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 retook to the sky 4 months later, on September 7. However the extra energy did little to enhance its poor low-speed dealing with traits, which had been, partly, remedied with the addition of horizontal stabilizer dihedral, leaving it to once more fly, now on this configuration, nonetheless two months later, on November 18.
The second prototype, 02 and registered F-WTMD, joined the flight check program the next yr on September 7. The upper thrust engines and the tailplane dihedral, together with full-span vanguard slats, delivered the supposed efficiency.
The primary manufacturing model Mercure 100 supposed for launch buyer Air Inter, incorporating all of those modifications, together with the full-length fuselage, first flew from the brand new Istres manufacturing plant on July 17, 1973 and was awarded its French kind certificates the next yr on February 12.
Air Inter took supply of the primary of its ten plane on Could 16, integrating the sort into its shuttle-type French home route community. It obtained its second instance seven days later, on June 11.
Of the ten ordered, the primary six had been delivered in 1974 and the remaining 4 the next yr, alphabetically registered F-BTTA via -BTTJ.
Though its first 4 plane had been solely provisioned with Class II touchdown functionality, its remaining six featured the upgraded, Class III customary, enabling it to conduct approaches with 500-foot runway visible ranges (RVR) and 50-foot resolution heights (DH). The preliminary 4 had been subsequently introduced as much as this functionality.
Accommodating 150 passengers in single-class, six-abreast, three-three, preparations with 32-inch seat pitches, its ten Mercure 100s had been nicely obtained by its passengers and operated multiple-daily roundtrips between a dozen French home cities and cities on sectors that diversified between 50 and 70 minutes, demonstrating its speedy turn-around functionality.
Its capability, nonetheless, proved too extreme for demand. Decrease than anticipated load elements, together with escalating gasoline costs, paradoxically prompted Air Inter to in the end purchase a fleet of Sud-Aviation Caravelle 12s, working them on lots of the identical routes, however with decrease prices. Though it briefly flirted with the thought 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 supplied technological comparability to different twin-jets.
In the course of the first 5 years of operation, the ten Mercure 100s carried out greater than 90,000 hours, consisting of some 100,000 53-minute segments and reaching a median 98.5-percent dispatch reliability. Every plane operated eight to 10 every day flights.
Geared up with a completely monitored automated pilot and head-up instrument studying shows, they carried out Class IIIA landings throughout poor climate circumstances, and nonetheless achieved a 98- to 99-percent reliability charge.
On March 25, 1985, Air Inter took supply of the second prototype, F-WTCC. Already having been provisioned with the longer fuselage, the upper rated engines, the vanguard slats, and the tailplane dihedral, it was introduced as much as full manufacturing customary, giving Air Inter an 11-strong fleet.
PROGRAM CONCLUSION:
As a result of no different provider 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, had been ever constructed. Though the design was an aerodynamic success and it was extraordinarily dependable in every day operations, it was a monetary failure due to a number of causes.
1). Just like the Vickers VC-10 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 provider maintained.
2). Dassault-Breguet, maybe with out alternative, employed then-current know-how for it, 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 electing to make use of its thrust for payload and passenger capability versus vary.
3). As a result of it launched the Mercure program late, these and different twin-jets had already captured many of the market and supplied the required payload and vary variations to take action. Whereas the last word stretches of the Caravelle, the DC-9, and the 737 resulted, respectively, in most passenger capacities of 139, 139, and 130, their ranges had been considerably larger, providing operators extra flexibility.
4). Though market research for an airbus-type of plane had been correct, their timing was not. Solely after the Nineteen Eighties was the 150-seat twin prevalent.
5). Lastly, the Mercure 100’s working economics couldn’t be totally exploited if its extra capability was not crammed.
Whereas all of those elements led to the sort’s demise and resulted in its paltry manufacturing run, Dassault-Breguet formally attributed the explanation for its discontinuation as, “Fabrication stopped after completion of the tenth (manufacturing) plane because of the extraordinarily penalizing evolution of the US greenback change charge.”
Regardless of what was definitely a failure by many measures, the Mercure 100, whose final scheduled flight occurred on April 29, 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 precipitated a single fatality.
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Source by Robert Waldvogel
