Airborne Wings

The Airbus A-310

Seeking to complement its original, although larger-capacity, A-300 on thinner sectors with a low-cost, minimally redesigned counterpart and thus expand its product range, Airbus Industrie explored a shorter-fuselage version designated "A-310."

A consortium of European aircraft manufacturers headquartered in Toulouse, France, Airbus Industrie itself had arisen because the design and marketing of an advanced, widebody airliner had exceeded the financial strength of any single, Europe-based company, the principle ones of which had included de Havilland with the DH.106 Comet, Vickers with the VC-10, Hawker Siddeley with the HS.121 Trident, and the British Aircraft Corporation with the BAC-111 in the United Kingdom, and Sud-Aviation with the SE.210 Caravelle and Dassault-Breguet with the Mercure 100 in France.

The A-300, its first joint design, not only signaled its launch as an aircraft manufacturer, but that of the aircraft itself and the concept it represented—a large-capacity, widebody, twin-engined "airbus."  Intended to compete with Boeing, and particularly with its still-envisioned 767, it provided a non-US alternative to continental carriers and a foundation on which a European commercial product range could be built, offering the first serious challenge to both Boeing and McDonnell-Douglas.

Intended for short- to medium-range, relatively high-capacity deployment, the aircraft featured a widebody fuselage mated to two high bypass ratio turbofans whose thrust capability and reliability, coupled with a high-lift wing, had served as the key elements of its design.

Obviating the need for a third powerplant characteristic of the 727, the DC-10, and the L-1011, the twin-engine configuration yielded numerous economic benefits, including the reduction of structural and gross weights, the reduction of maintenance costs, the elimination of the additionally required fuel lines, the introduction of structural simplicity, and the reduction of seat-mile costs.

Aerodynamically, the twin-engine design also resulted in several advantages.  The wings, mounted further forward than feasible by a tri-engine configuration, increased the moment-arm between the pylon-slung turbofans/center-of-gravity and its tail, thus requiring smaller horizontal and vertical stabilizers to maintain longitudinal and yaw-axis control and indirectly reducing structural weight and drag, yet maintaining certifiable control during single-engine loss, asymmetrical thrust conditions.

Designed by the Hawker Siddeley team in Hatfield, the 28-degree sweptback, supercritical wing, built up of a forward and rear full and mid half-spar, produced the greater portion of its lift over its aft portion, delaying shock wave formation and reducing drag.

Low-speed lift was augmented by full-span, engine pylon-uninterrupted leading edge slats, which increased the aircraft's take off weight capability by some 2,000 pounds, and tabbed, trailing edge Fowler flaps, which extended to 70 percent of their travel before rotating into camber-increasing profiles, resulting in a 25-percent larger chord.

Part of the reason for engine reliability had been the auxiliary power unit's integration into the main electric, air conditioning, and starting systems, providing immediate back-up in the event of engine failure at altitudes as high as 30,000 feet.

The A-300's widebody fuselage provided the same degree of twin-aisle comfort and loading capability of standard LD3 baggage and cargo containers as featured by the quad-engined 747 and the tri-engined DC-10 and L-1011.

Seeking to build upon these design strengths, yet decrease passenger capacity with a foreshortened fuselage and expand its market application, Airbus Industrie conceptionally studied and proposed nine potential aircraft varying in capacity, range, and powerplant number and designated A-300B1 to -B9 based upon the initial A-300 platform.  It was the tenth, however—designated A-300B10—which most optimally catered to carriers' needs for a 200-passenger airliner for segments with insufficient demand to support its larger counterpart and for those which merited additional frequencies, such as during off-peak times.  Other than the two original prototype A-300B1s and the three-frame longer A-300B2, the aircraft had only offered a single basic fuselage length, whose capacity partially accounted for initially sluggish sales.

Although a low-cost A-300B10MC "Minimal Change" entailed mating a shorter fuselage with the existing wing, powerplants, and tailplane would have provided few engineering obstacles, it would have resulted in an aircraft proportionally too small and heavy for the A-300's original surfaces.  Despite a lower structural weight, it would have offered insufficient internal volume for revenue-generating passenger, cargo, and mail payload to eclipse its direct operating costs (DOC).

Balancing both the superior performance and the minimized development cost sides of the program's equation, Airbus Industrie considered two possible approaches:

1). The A-300B10X, which employed a new wing designed by the since-amalgamated British Aerospace in Hatfield with smaller leading and trailing edge, high-lift devices.

2). The A-300B10Y, which utilized the existing A-300 wing box, with some modifications.

Lufthansa, the envisioned launch customer, strongly advocated the former approach, because of the reduced costs associated with a redesigned, more advanced airfoil, and, together with Swissair, which equally contemplated an order for the type, detailed performance specifications.  Placing deposits for 16 A-300B10s, which were concurrently redesignated "A-310s," in July of 1978, both airlines expected a final configuration by the following March.

The aircraft, which sported a 12-frame shorter fuselage for 767-like, 245-passenger accommodation, first appeared at the Hanover Air Show in model form.

Its wing, retaining the 28-degree sweepback of the A-300's, featured a shorter span and a consequent 16-percent reduced area, eliminating its center, half-spar and therefore offering equal, front and rear spar load distribution.  The spars themselves, with 50 percent greater depth, were stronger, yet decreased structural weight by more than five tons.  Its revised shape, requiring a new center section, introduced a double-curved profile, its metal, bent both span- and chord-wise, requiring shot-peening manufacturing techniques to form.

The increased-chord and –radius leading edge slats, necessitating a new cut-out over the engine pylon, improved take off performance, while the former, inner-tabbed, trailing edge Fowler flap panels were integrated into a single-slotted one with increased rearward movement.  The two outer panels, also combined into a single panel, decreased cruise drag.

Lateral control, no longer necessitating the A-300's outboard ailerons, was maintained by the inboard ailerons operating in conjunction with the spoilers.

The tailplane, a scaled-down version of the A-300's, featured reduced separation between the upper surface of its elevator and the horizontal stabilizer, in order to decrease drag, and a redesigned tailcone permitted optimized internal cabin volume.

Powerplant choices included the 48,000 thrust-pound General Electric CF6-80A1 and the equally powered Pratt and Whitney JT9D-7R4D1, while the Rolls Royce RB.211-524D was optionally available, although no carrier ever specified it.

Both potential launch customers, round whose specifications the foreshortened version took shape, placed orders, Swissair ordering ten Pratt and Whitney-powered aircraft on March 15, 1979, Lufthansa placing 25 firm and 25 optioned orders for the General Electric-powered variant on April 1, and KLM Royal Dutch Airlines mimicking this order with ten firm and ten options two days later, also for the General Electric version, thus signaling the program's official launch.

Three basic versions, varying according to range, were then envisioned: the short-range, 2,000-mile A-310-100; the medium-range, 3,000-mile A-310-200; and the long-range, 3,500-mile A-310-300.

Final assembly the first two Pratt and Whitney-powered A-310-200s, with construction numbers (c/n) 162 and 163, commenced in the Aerospatiale factory in Toulouse during the winter of 1981 to 1982, continuing, not reinitiating, the A-300 production line numbering sequence.  Major sectors, components, parts, and powerplants were fabricated by eight basic aerospace companies: Deutsche Airbus (major fuselage portions, the vertical fin, and the rudder), Aerospatiale (the front fuselage, the cockpit, the lower center fuselage, and the engine pylons), British Aerospace (the wings), CASA (doors and the horizontal tail), Fokker (the wing moving surfaces), Belairbus (also the wing moving surfaces), General Electric (the engines), and Pratt and Whitney (also the engines).  Fokker and Belairbus were Airbus Industrie associate members.

Transfer to the final assembly site was facilitated by a fleet of four, 4,912-shaft horsepower Allison 501-D22C turboprop-powered Aero Spacelines Super Guppys, which had been based upon the original, quad piston-engined B-377 Stratocruiser airliners, requiring eight flights collectively totaling 45 airborne hours and covering some 8,000 miles for A-310 completion.  The transports were re-dubbed "Airbus Skylinks."

A-310 customer furnishing, including thermal and noise insulation; wall, floor, and door cladding; ceiling, overhead storage compartment, and bulkhead installations; and galley, lavatory, and seat addition, according to airline specification of class divisions, densities, and fabrics, colors, and motifs, occurred in Hamburg Finkenwerder, to where all aircraft were flown from Toulouse.

The first A-310, registered F-WZLH and wearing Lufthansa livery on its left side and Swissair livery on its right, was rolled out on February 16, 1982.  Powered by Pratt and Whitney turbofans, it only differed from production aircraft in its internal test equipment and retention of the A-300's dual, low- and high-speed aileron configuration.

Superficially resembling a smaller A-300, however, it incorporated several design modifications.

The 13-frame-shorter fuselage, rendering an overall aircraft length of 153.1 feet, incorporated a redesigned tail and a relocated aft pressure bulkhead, resulting in a cabin only 11 frames shorter, and access was provided by four main passenger/galley servicing doors and two oversize type 1 emergency exits.  These measured four feet, 6 ¾ inches high by two feet, 2 ½ inches wide.

The A-310's wing box, a two-spar, multi-rib metal structure with upper and lower load-carrying skins, introduced new-purity aluminum alloys in its upper layer and stringers, which resulted in a 660-pound weight reduction, but otherwise retained the larger A-300's ribs and spacings.  Almost blended with the fuselage's lower curve at its underside root, the airfoil offered a greater thickness-chord ratio, of 11.8, as opposed to its predecessor's 10.5, reducing the amount of wing-to-body interference ordinarily encountered at high Mach numbers, yet it afforded sufficient depth at the root itself to carry the required loads at the lowest possible structural weight and simultaneously provided the greatest amount of integral fuel tankage.

Low-speed lift was attained by means of the three leading edge slat panels and a single Krueger flap located between the inner-most slat and the root, and inboard, vaned, trailing edge Fowler flaps and a single outboard Fowler flap panel.

Although the first two A-310s retained the A-300's outboard, low-speed ailerons, they quickly demonstrated their redundancy, roll control maintained by means of all-speed, trailing edge ailerons augmented by three electrically-activated, outer spoilers, which extended on the ground-angled wing.  The four inner spoilers served as airbrakes, while all seven, per wing, extended after touchdown to serve as lift dumpers.

Engine bleed air or that from the auxiliary power unit (APU) provided icing protection.

Engine pylons were positioned further inboard then those of the comparable A-300, and the nacelles protruded further forward.

With a 144-foot span, the wings covered a 2,357.3-square-foot area and had an 8.8 aspect ratio.

Although the A-310 retained the A-300's conventional tail, it featured a horizontal stabilizer span reduction, from 55.7 to 53.4 feet, with a corresponding decease from 748.1 to 688.89 square feet, while its vertical fin rendered an overall aircraft height of 51.10 feet.

Power was provided by two 48,000 thrust-pound Pratt and Whitney JT9D-7R4D1 or two 48,000 thrust-pound General Electric CF6-80A1 high bypass ratio turbofans, either of which was supportable by the existing pylons, and usable fuel totaled 14,509 US gallons.

The hydraulically actuated tricycle undercarriage was comprised of a twin-wheeled, forward-retracting, steerable nose wheel, and two, dual tandem-mounted, laterally-retracting, anti-skid, Messier-Bugatti main units.  Their carbon brakes resulted in a 1,200-pound weight reduction.

The smaller, lighter, and quieter Garrett GTCP 331-250 auxiliary power unit offered lower fuel consumption than that employed by the A-300, and the aircraft featured three independent, 3,000 pound-per-square-inch hydraulic systems.

The A-310's cockpit, based upon its predecessor's, incorporated the latest avionics technology and electronic displays, and traced its origin to the October 6, 1981 first forward-facing cockpit crew (FFCC) A-300 flight, which deleted the third, or flight engineer, position, resulting in certification to this standard after a three-month, 150-hour flight text program.  That aircraft thus became the first widebodied airliner to be operated by a two-person cockpit crew.

The most visually-apparent flight deck advancement, over and above the number of required crew members, had been the replacement of many traditional analog dials and instruments with six, 27-square-millimeter, interchangeable cathode ray tube (CRT) display screens to reduce both physical and mental crew workload, subdivided into an Electronic Flight Instrument System (EFIS) and an Electronic Centralized Aircraft Monitor (ECAM), which either displayed information which was necessary or which was crew-requested, but otherwise employed the dark-screen philosophy.  Malfunction severity was indicated by color—white indicating that something had been turned off, yellow indicating potentially required action, and red signifying immediately-needed action, coupled with an audible warning.

Of the six display screens, the Primary Flight Display (PFD), which was duplicated for both the captain and the first officer, and the Navigation Display (ND), which was equally duplicated, belonged to the Electronic Flight Instrument System, while the Warning Display (WD) and the Systems Display (SD) belonged to the Electronic Centralized Aircraft Monitor.

The Primary Flight Display, viewable in several modes, offered, for example, an electronic image of an artificial horizon, on the left of which was a linear scale indicating critical speeds, such as stick shaker, minimum, minimum flap retraction, and maneuver, while on the right of it were altitude parameters.

The Navigation Display screen, below that of the Primary Flight Display, also featured several modes.  Its map mode, for instance, enabled several parts and scales of a compass rose to be displayed, such as its upper arc subdivided into degrees, with indications of course track deviations, wind, tuned-in VOR/DME, weather radar, the selected heading, the true and indicated airspeeds, the course and remaining distance to waypoints, primary and secondary flight plans, top-of-descent, and vertical deviations.

The autopilot possessed full control for Category 2 automatic approaches, including single-engine overshoots, with optional Category 3 autoland capability.

The collective Electronic Centralized Aircraft Monitor, whose two display screens were located on the lower left and right sides of the center panel, continually screened more than 500 pieces of information, indicating or alerting of anomalies, with diagrams and schematics only appearing during flight phase-relevant intervals, coupled with any necessary and remedial actions.  The Systems Display, located on the right, could feature any cockpit crew member-selected schematic at any time, such as hydraulics, aileron position, and flaps.

Two keyboards on the center pedestal interfaced the flight management system (FMS).

The flight control system, operating off of two Arinc 701-standard computers and essentially serving as autopilots, drove the flight director and speed reference system, and was operable in numerous modes, inclusive of auto take off, auto go-around, vertical speed select and hold, altitude capture and hold, heading select, flight level change, hold, heading hold, pitch, roll/attitude hold, and VOR select and homing.

The thrust control system, operating off of an Arinc 703-standard computer, provided continuous computation and command of the optimum N1 and/or engine pressure ratio (EPR) limits, the autothrottle functions, the autothrottle command for windshear protection, and the autothrottle command for speed and angle-of-attack protection.

Unlike earlier airliners, the A-310 replaced the older-technology pilot command and input transmission by means of mechanical, cable linkages with electronic bit or byte signaling.

Retaining the A-300's fuselage cross-section, the A-310 featured a 109.1-foot-long, 17.4-foot-wide, and seven-foot, 7 ¾-inch high cabin, resulting in a 7,416-cubic-foot internal volume, whose inherent flexibility facilitated six-, seven-, eight-, and nine-abreast seating for first, business, premium economy, standard economy, and high-density/charter configurations and densities, all according to customer specification.  Typical dual-class arrangements included 20 six-abreast, two-two-two, first class seats at a 40-inch pitch and 200 eight-abreast, two-four-two, coach seats at a 32-inch pitch, or 29 first class and 212 economy class passengers at, respectively, six-abreast/40-inch and eight-abreast/32-inch densities.  Two hundred forty-seven single-class passengers could be accommodated at a 31- to 32-inch pitch, while the aircraft's 280-passenger, exit-limited maximum, entailed a nine-abreast, 30-inch pitch arrangement.

Standard configurations included two galleys and one lavatory forward and two galleys and four lavatories aft, with encloseable, handrail-equipped overhead storage compartments installed over the side and center seat banks.

The forward, lower-deck hold, measuring 25 feet, ½ inch in length, accepted three pallets or eight LD3 containers, while the aft hold, running 16 feet, 6 ¼ inch in length, accepted six LD3 containers.  The collective 3,605 cubic feet of lower-deck volume resulted from the 1,776 cubic feet in the forward compartment, the 1,218 in the aft compartment, and the 611 in the bulk compartment, which only accepted loose, or non-unit load device (ULD), load.

Powered by two General Electric CF6-80C2A2 engines and configured for 220 passengers, the A-310-200 had a 72,439-pound maximum payload, a 313,050-pound maximum take off weight, and a 271,150-pound maximum landing weight.  Range, with international reserves for a 200-nautical mile diversion, was 4,200 miles.

The A-310-200 prototype, flown by Senior Test Pilot Bernard Ziegler and Pierre Baud, took to the skies for the first time on April 3, 1982 powered by Pratt and Whitney JT9D turbofans, and completed a very successful three-hour, 15-minute sortie, during which time it attained a Mach 0.77 airspeed and a 31,000-foot altitude.  After 11 weeks, 210 airborne hours had been logged.

The second prototype, registered F-WZLI and also powered by Pratt and Whitney engines, first flew on May 3, completing a four-hour, 45-minute flight, and the third, powered by the General Electric CF6 turbofans for the first time, shortly followed, the five aircraft demonstrating that the A-300-morphed design had far more capability than originally calculated.  Drag measures were so low, in fact, that the cruise Mach number was increased from the initially calculated 0.78 to a new 0.805, while the buffet boundary was ten-percent greater, permitting a 2,000-foot-higher flight level for any gross weight to be attained, or a 24,250-pound greater payload to be carried.  Long-range fuel consumption was four percent lower.

The Airbus A-310 received its French and German type certification on March 11, 1983 for both the Pratt and Whitney- and General Electric-powered aircraft and Category 2 approaches, and a dual-delivery ceremony, to Lufthansa German Airlines and Swissair, occurred on March 29 in Toulouse.  It became the European manufacturer's second aircraft after that of the original A-300.

Lufthansa, which had operated 11 A-300B2s and -B4s and had inaugurated the larger type into service seven years earlier, on April 1, 1976, from Frankfurt to London, followed suit with the A-310-200 on April 12, 1983, from Frankfurt to Stuttgart, before being deploying the type to London later that day.  It replaced its early A-300B2s.

Swissair, which, like Lufthansa, had been instrumental in its ultimate design, inaugurated the A-310 into service nine days later, on April 21.  Of its initial four, three were based in Zurich and one was based in Geneva, and all were used on high-density, European and Middle Eastern sectors, many of which had previously been served by DC-9s.

A convertible variant, featuring a forward, left, upward-opening main deck cargo door and loading system, was designated A-310-200C, the first of which was delivered to Martinair Holland on November 29, 1984.

By March 31, 1985, 56 A-310s operated by 13 carriers had flown 103,400 revenue hours during 60,000 flights which had averaged one-hour, 43 minutes in duration.

Demand for a longer-range version precluded A-310-100 production, but resulted in the second, and only other, major version, the A-310-300.

Launched in March of 1983, it introduced several range-extending design features.

Wingtip fences, vertically spanning 55 inches and featuring a rear navigation light fairing, extended above and below the tip, extracting energy from unharnassed vortices created by upper and lower airfoil pressure differential intermixing, and reduced fuel burn by 1.5 percent.  The device was first flight-tested on August 1, 1984.

Increased range capability, to a far greater extent, resulted from modifying the horizontal stabilizer into an integral trim fuel tank.  Connected to the main wing tanks by double-walled pipes and electrically driven pumps, the new tank was contained in the structurally strengthened and sealed horizontal stabilizer wing box, storing five tons of fuel and shifting the center-of-gravity over 12- to 16-percent of the aerodynamic chord.  The modification, requiring minimal structural change to an aerodynamic surface beyond the pressurized fuselage, offered numerous advantages over the increase in range, including Concorde-reminiscent, in-flight fuel transferability to effectuate optimum trims, and an aft center-of-gravity to reduce wing loading, drag, and resultant fuel burn.  A trim tank computer controlled and monitored center-of-gravity settings, and the amount of needed fuel could be manually selected during the on-ground refueling process.

Structure weight had been decreased by use of a carbon-fiber vertical fin, resulting in a 310-pound reduction.  The A-310 had been the first commercial airliner to employ such a structure.

Total fuel capacity, including that of the trim tank, equaled 16,133 US gallons, while up to two supplementary tanks could be installed in the forward portion of the aft hold, increasing capacity by another 1,902 US gallons.

In order to permit extended-range twin operations (ETOPS), a certification later redesignated extended-range operations (EROPS), the aircraft was fitted with a hydraulically-driven generator, increased lower-deck fire protection, and the capability of in-flight APU starts at minimum cruising altitudes.

Powered by General Electric CF6-80C2A8 turbofans and carrying 220 dual-class passengers, the A-310-300 had a 71,403-pound payload capability and a 330,675-pound maximum take off weight, able to fly 4,948-mile nonstop sectors.

First flying on July 8, 1985, the type was certified with Pratt and Whitney JT9D-7R4E engines six months later, on December 5, while certification with the General Electric CF6-80C2 powerplant followed in April of 1986.

Four of Swissair's ten A-310s, which were operated on its Middle Eastern and West African routes, were -300 series.

The A-310-300 was the first western airliner to attain Russian State Aviation Register type certification, in October of 1991.

Although it had initially been intended as a smaller-capacity, medium-range A-300 complement, the design features incorporated both conceptually and progressively resulted in a very capable twin-engine, twin cockpit crew, widebody, intercontinental airliner which, in its two basic forms, served multiple missions: an earlier-generation Boeing 707 and McDonnell-Douglas DC-8 replacement; a Boeing 727 replacement on maturing, medium-range routes; a DC-10 and L-1011 TriStar replacement on long, thin sectors; an A-300 replacement on lower-density segments; an A-300 complement during off-peak times; and a European competitor to the similarly-configured Boeing 767, enabling Airbus Industrie to describe the type as follows: "The A-310's optimized range of up to 5,000 nautical miles (9,600 km) is one of the parameters that has made it the ideal ‘first widebody' aircraft for airlines growing to this size of operation."

Singapore Airlines had been the first to deploy the A-310-200 on long-range overwater routes in June of 1985, covering the 3,250-mile sector between Singapore and Mauritius, although the aircraft had not been EROPS-equipped, that distinction reserved for Pan Am, which had connected the 3,300 miles over the North Atlantic from New York/JFK to Hamburg the following April.

During that year, the A-310-200 became available with wingtip fences, first deliveries of which were made to Thai Airways International, and the A-310-300 was progressively certified with uprated engines and increased ranges, a 346,125-pound gross weight producing a 5,466-mile range capability and a 361,560-pound gross weight producing a 5,926-mile range, all with General Electric engines.  Pratt and Whitney turbofan-powered aircraft offered even greater ranges.

The first EROPS-equipped A-310-300 with JT9D-7R4E engines, was delivered to Balair on March 21, 1986, and its range capability, with 242 single-class passengers and a 337,300-pound gross weight, exceeded 4,500 miles.

By the end of that month, the A-310 fleet had collectively logged more than 250,000 hours.

A post-production cargo conversion of the A-310-200, designated A-310-P2F and performed by EADS EFW in Dresden, Germany, entailed the installation of a forward, left, upward-opening door, which facilitated loading of 11 96 x 125-inch or 16 88 x 125-inch main deck pallets, while three of the former and six LD3 containers could be accommodated on the lower deck.  With an 89,508-pound payload and a 313,055-pound maximum take off weight, the freighter offered 10,665 cubic feet of internal volume.

The last of the 255 A-310s produced, an A-310-300 registered UK-31003, first flew on April 6, 1998 and was delivered to Uzbekistan Airways two months later, on June 15.  Although Airbus Industrie had contemplated offering a shorter-fuselage version of the A-330, the A-330-500, as a potential A-310 replacement, its range and capacity had proved too high to assume its mission profiles.  Resultantly, no definitive design ever succeeded it.

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Pinning Airborne Wings