I
Fuselage stretchability, inherently included within the primary DC-9 design, had characterised its program, leading to 4 dimensionally divergent, higher-capacity variations, together with the initially-elongated DC-9-30 over the baseline sequence -10/14/15, the following DC-9-40, and the ultimate DC-9-50, the latter accommodating 49 extra passengers than the twin-jet’s authentic most.
The DC-9 itself, based upon the 4 design tenets of ruggedness, simplicity, reliability, and low-cost, had been McDonnell-Douglas’s best-selling business aircraft-so a lot so, in truth, that it took off or landed someplace on the planet each seven seconds, serving greater than 570 cities with some 6,050 each day flights, and by 1979, the collective fleet had carried a couple of billion passengers and logged greater than 18 million hours with an virtually 99-percent dispatch reliability fee.
Its Pratt and Whitney JT8D engine, probably the most extensively used powerplant and numbering in extra of 12,000 items, had not solely supplied propulsive thrust for all variations of the DC-9, however had additionally powered the Boeing 727, the Sud-Aviation SE.210 Tremendous Caravelle, the Boeing 737, and the Dassault-Breguet Mercure 100.
Each the DC-9’s primary design and its JT8D turbofan due to this fact provided probably the most optimum, cost-effective platform on which to base a larger-capacity successor, which wanted to equal the DC-9-30’s vary functionality, but exceed the DC-9-50’s economics.
Its fuselage, not having reached its restrict of stretchability, lent itself to nonetheless higher-capacity lodging, however its impediment had been a powerplant of ample thrust to keep up acceptable payload, vary, and efficiency parameters for its operators.
Primarily based upon the sooner, two-stage JT3D, which had powered each the 707 and the DC-8, the JT8D, a low, one-to-one bypass ratio turbofan, had first run on April 7, 1961, taking to the skies for the primary time on Might 1 of the next 12 months mounted to a 707. Receiving FAA certification on February 9, 1963, because the 14,000 thrust-pound JT8D-1, it had powered the 727-100 earlier than being employed by the DC-9-10 and was subsequently provided in a number of successively higher-thrust variations, the final of which had been the 17,400 thrust-pound JT8D-17R.
A brand new-generation variant, offering software for an final DC-9 stretch and designated JT8D-109, had been one in every of six demonstration powerplants incorporating bigger, single-stage followers developed for NASA’s Quiet Engine Program, which had run between 1972 and 1975, and two of its variations had logged greater than 50 hours retrofitted to a modified DC-9-32. Design of an extra growth, the 18,500 thrust-pound JT8D-209, started in 1974 and first ran two years later, take a look at flown on a McDonnell-Douglas Superior Medium STOL Transport (AMST) in March of 1977.
Though a brand new, supercritical wing had additionally initially been thought of, the plane, meant for short- to medium-range sectors which entailed larger ratios of climb-and-descent to precise cruise profiles, couldn’t absolutely exploit such a brand new design, its advantages resultantly unable to justify its larger growth prices. The present DC-9 wing, incorporating root and tip extensions and modified high-lift gadgets, would offer the required efficiency, financial system, and vary parameters.
A number of preliminary iterations, largely based mostly upon the DC-9-50 and all that includes fuselage stretches for larger capacities, larger-area wings, and two refanned turbofans, had included the refan-stretched DC-9-50RS, the refan-super stretched DC-9-50RSS, the DC-9-55, and the DC-9-60, whereas a DC-9QSF, meant for Japanese operators as an NAMC YS-11 twin turboprop substitute, mated a DC-9-40 airframe with two 18,000 thrust-pound JT8D-209 engines and a two-foot bigger wing, enabling the 114,000-pound plane to function from 4,000-foot runways with 120 passengers.
Nevertheless, price constraints and design complexities dictated a less complicated, extra easy model which included the longer fuselage, increased-area wings, and JT8D-209 turbofans, but retained cockpit commonality with all earlier DC-9 variants. Skipping each the DC-9-60 and DC-9-70 sequences, the definitive plane, designated DC-9-80-or DC-9 Tremendous 80, to extra precisely replicate the meant 12 months of service inauguration-had been launched on October 20, 1977 with the receipt of 27 agency and 13 optioned orders from Swissair, Austrian Airways, and Southern Airways, together with a letter of intent from LAV Lineas Aeropostal Venezolanas, all of which had been earlier DC-9 operators. Envisioned as a higher-capacity complement to its DC-9 airframe and a substitute for higher-cost tri-jets, it meant to supply service in maturing markets whose environmental and noise restrictions had precluded larger-capacity tools substitution, the plane providing a considerably smaller noise footprint, higher vary and capability, and the bottom seat-mile prices of any comparable twin-jet.
In line with then-President of the Douglas Plane Firm, John C. Brizendine, “Lately…we now have grow to be aware of the necessity to preserve power, to guard the atmosphere, and to provide increasingly more economically environment friendly plane. (The DC-9 Tremendous 80) is particularly designed to satisfy the necessities of our business for years to come back. These embrace environmental compatibility, power effectivity, economical operation, and a spacious, comfy inside.”
McDonnell-Douglas boasted of the plane, “The DC-9 Tremendous 80 is a mix of confirmed design with obtainable low-risk expertise for enhanced effectiveness, (however) the exceptional DC-9 reliability and decrease working prices are maintained.”
Though it had been based mostly upon this earlier-generation twin, it nonetheless launched a number of superior options.
A fuselage stretch, attained by the use of an eight-frame plug ahead of the wing and a single-frame insertion aft of it, resulted in a 147.10-foot total size, rising most capability to 172, or 33 greater than the DC-9-50 and a staggering 82 greater than the preliminary DC-9-10, and producing probably the most massively stretched business airliner as much as that point. The ahead, left, and aft, ventral, exits, each outfitted with extendible airstairs, had been retained, however an aft, left servicing door, situated solely ft from the engine, had been launched. Aeritalia of Naples, Italy, manufactured its fuselage panels.
A brand new, 10.6-foot heart part and two-foot parallel-chord tip extensions, ensuing within the third dimensionally divergent DC-9 wing, yielded a 28-percent space, 57-percent gas capability, and 11-percent effectivity enhance.
Measuring 107 ft, 10 1/4 inches, the airfoil, with a 24-degree sweep again at its quarter chord, a 9.62 side ratio, three levels of dihedral, and a 1,239 square-foot space, had been comprised of 4 per-wing precision-machined pores and skin panels which had been remodeled from 14,000-pound ingots measuring 60 inches huge, 15 inches lengthy, and 30 inches thick by the Reynolds Steel Firm of McCook, Illinois.
The all-metal, two-spar construction, with riveted spanwise stringers, featured full-span, three-position vanguard slats with a brand new, intermediate setting to lower take off drag and enhance climb efficiency at larger gross weights; bigger, doubled-slotted, trailing edge flaps which lined 67 % of the span and lowered the plane’s stalling pace; three spoiler panels, the outer two of which have been employable as each flight and floor raise dumpers; and ailerons. All however the latter have been hydraulically actuated, whereas the ailerons themselves have been operated by hand. An underwing vortillon fence ensured correct airflow. Offering 1,520 US gallons of further gas tankage, it additionally provided an increased-area foremost undercarriage bay.
The variable-incidence, electrically-actuated horizontal tail, spanning 40.2 ft, or 3.6 ft greater than that of the DC-9-50, retained the design’s attribute t-tail configuration and sported assister tab-equipped elevators, whereas the vertical fin, rendering an total plane top of 30.2 ft, featured a hydraulically-actuated rudder. It had been 1.4 ft larger than the DC-9-50’s.
Its Pratt and Whitney JT8D-209 turbofan, mounted on both facet of the aft fuselage and retaining the unique target-type thrust reversers, was based mostly upon the core of the sooner JT8D-9, however launched a 49-inch wider fan and a complicated, low-pressure compressor, producing 18,500 kilos of thrust together with a further 750 kilos of automated energy reserve (APR), generated throughout engine-loss circumstances. The larger-diameter, single-stage fan, driving a bigger mass of sizzling core section-bypassing air, coupled with extra environment friendly cold and hot exit duct intermixing air, and elevated sound absorption materials in its nacelle and surrounding casing, yielded quite a few enhancements, inclusive of elevated thrust functionality; a better bypass ratio-of 1:1.78 versus the sooner JT8D’s 1:1; a decrease exit velocity; an 11-percent lower in particular gas consumption; and a considerably smaller noise footprint than that of the medium-range tri-jets it had been meant to exchange.
Using weight-reducing Kevlar-reinforced aluminum honeycomb stiffeners with graphite tape caps within the outer barrel of its nostril cowl and its higher and two decrease cowl doorways, the nacelle, 21.1 ft lengthy, was 4.5 ft longer than the JT8D-9’s and due to this fact introduced engineering challenges relative to its mounting on the DC-9’s, albeit longer, physique.
The DC-9 Tremendous 80 retained the hydraulically-retractable, tricycle, dual-wheeled, Cleveland Pneumatic undercarriage, fitted with Goodyear wheels, tires, and disc brakes; Hydro-Aire Mk IIIA antiskid items; and Douglas ran air brake cooling. The nostril wheel was steerable to 27 levels to both facet.
Though the Tremendous 80 retained a typical pilot sort score with the DC-9, it nonetheless provided a number of cockpit developments, together with a digital and flight steerage management system designed by the Sperry Flight Programs Division of Sperry Rand Company, which built-in the efficiency of seven flight management subsystems into two an identical digital computer systems; cathode ray tube (CRT) shows; a digital gas amount gauge system; a dial-a-flap system; and Class IIIA autoland functionality of 50-foot choice top (DH) and 700 ft of runway visible vary (RVR). A later launched Digital Efficiency Administration System supplied automated pitch and thrust to effectuate optimum pace and gas burn throughout the plane’s climb, cruise, and descent profiles.
The 101-foot-long, “huge look” cabin, featured a broad, contoured, and sculpted acoustically-treated ceiling which blended in with the enclosable overhead storage compartments; aluminum sidewall panels sculpted around the home windows; fluorescent lighting; a 19-inch aisle; and five-abreast, two-three or three-two, configured financial system class seating, which decreased by half the variety of center seats historically related to six-abreast preparations.
Inside decor, which various from conservative, business-oriented appointment to daring patterns and brilliant colours, was decided by the operator and custom-designed by McDonnell-Douglas whose inside design groups typically made journeys to airline residence international locations with a view to take in native tradition and customs after which convert that have into area- or country-reflective motifs. Wool and wool artificial blends have been standardly used for seat covers and carpets.
Class and seating configuration equally various in accordance with operator. A 137-passenger, dual-class association, as an example, entailed 12 four-abreast first-class seats at a 38-inch pitch and 125 five-abreast financial system class seats at a 34-inch pitch, whereas single-class densities included 155 passengers at a 32/33-inch pitch, 167 constitution seats at a 30-inch pitch, or a most of 172 high-density passengers, the latter accommodatable with a single galley set up.
Inside noise discount was attained by the use of an insulating blanket of fabric-reinforced Mylar over fiberglass.
The elongated DC-9 launched a brand new pressurization and air circulation system, which changed cabin air at higher frequencies, and its potable water system featured in-line heaters in all of its water traces. An increased-capacity auxiliary energy unit (APU) ran its environmental management system on the bottom.
The plane’s longer fuselage considerably elevated its lower-deck baggage and cargo compartment quantity, whose ahead, heart, and aft holds respectively encompassed 434, 376, and 443 cubic ft.
The DC-9-80 retained 80 % of the DC-9-50’s key upkeep options.
Like all of its earlier, shorter-fuselage predecessors, the plane had been designed for short-sector, rapid-turnaround, self-sufficient operations from brief, limited-facility airfields, with its elevated thrust, larger-area wings, self-contained airstairs, auxiliary energy unit for environmental conditioning and engine begins, low-to-ground profile to facilitate servicing, loading, and upkeep, and skill to function two or extra sectors with out the necessity for refueling. Most turnarounds required little greater than baggage carts.
With a most structural payload of 40,112 kilos, the DC-9-81, as designated in its preliminary variant, had a 147,000-pound gross weight, though this had been later elevated to 149,500 kilos with uprated engines, and a most touchdown weight of 128,000 kilos. Its regular and most cruise speeds have been, respectively, Mach 0.76 and 0.80. Vary, with 155 single-class passengers and home reserves, was 1,564 nautical miles.
Piloted by Douglas Chief Engineering Pilot H. H. “Knick” Knickerbocker, Undertaking Pilot John P. Laine, and Flight Take a look at Engineer Virginia “Ginny” A. Claire, the primary DC-9 Tremendous 80 and the 909th twin-jet to roll off the Lengthy Seaside meeting line, made its maiden flight from Lengthy Seaside Municipal Airport’s Runway 30 on October 18, 1979 with name signal DACO 80-for “Douglas Plane Firm 80.”
Following a 25-mile round, overwater sample, the lengthy, slender-fuselage plane, accommodating 13,100 kilos of take a look at tools, accomplished a profitable two-hour, 50-minute basic-maneuvers take a look at sortie earlier than touchdown at McDonnell-Douglas’s Flight Operations Facility in Yuma, Arizona, the place the Chief Engineering Pilot concluded, “The bottom dealing with of the Tremendous 80 is even higher than the opposite DC-9s. It additionally appeared fairly steady in flight…The brand new engines have been faultless, and the reverse thrust was very efficient on touchdown…I consider the Tremendous 80 is a good airplane and can dwell as much as all our expectations.”
The 1,085-hour, $36 million, three-aircraft flight take a look at program, which entailed first flights of prototype N1002G on December 6, 1979 and N1002W on February 29, 1980, led to FAA certification seven months later, on August 26, below an modification to the DC-9’s authentic sort certificates.
First delivered to launch buyer Swissair on September 12, which had operated earlier DC-9-15, -30, and -50 sequence, it was inaugurated into scheduled service on October 5 from Zurich to Frankfurt, changing into the quietest business pure-jet. Co-launch buyer Austrian Airways, which had equally operated a fleet of DC-9-30s and -50s, inaugurated its first income service 21 days later, on October 26, from Vienna to Zurich.
With the intention to undertake the McDonnell-Douglas designation scheme, the DC-9-80, or DC-9 Tremendous 80, was rebranded the “MD-80” in 1983, its preliminary model dubbed “MD-81.”
II
Growth of the baseline Pratt and Whitney JT8D-209 engine, ensuing within the uprated, 20,000 thrust-pound -217, augmented further variations, the origin of which had been the 1979 requirement for a brief take off and touchdown (STOL) plane to function inside the Japanese home market. A then-projected iteration, designated DC-9 Tremendous 80SF, would have mated the DC-9-40’s fuselage with the DC-9-80’s wing and engines, however the higher-thrust JT8D-217, utilized to present fuselage dimensions, would have supplied many of the desired efficiency. Resultantly, a second variant, designated MD-82 and first introduced on April 16, 1979, featured the uprated, 20,000 thrust-pound turbofans with 850 kilos of automated energy reserve, a 44,024-pound payload, and a 2,050-mile vary with 155 passengers. First flying on January 8, 1981, it obtained its FAA sort certification six months later, on July 31, at an preliminary 147,000-pound most take off weight, though the 1982 choice of JT8D-217A engines additional elevated this to 149,500 kilos, leading to still-higher payload and vary capabilities.
Republic Airways, the July 1, 1978 amalgamation of North Central and Southern Airways, had been the model’s launch buyer, having been the world’s largest DC-9 operator with sequence -10s, -30s, and -50s, to which its eight MD-82s have been finally added.
The variant had been concerned in two distinctive applications. The primary of those, occurring in October of 1982, entailed the revolutionary lease of 20 MD-82s to American Airways, for which McDonnell-Douglas agreed to bear the upkeep and coaching prices. This let to the February 1984 buy of 67 plane, at engaging costs and with low cancellation penalties, to be delivered in blocks of ten to 25 airframes, every block of which had been confirmable 24 months earlier than the focused supply date. Turning into the mainstay of American’s short- to medium-range fleet to facilitate hub connections in Chicago and Dallas, the plane, configured for 142 first and financial system class passengers, finally numbered 234, the world’s largest, single-type complete outdoors of the previous USSR.
The second revolutionary transaction occurred on April 12, 1985, when the Shanghai Aviation Industrial Company agreed to license-build 25 MD-82s within the Individuals’s Republic of China.
An extended-range successor, designated MD-83 and first introduced on January 31, 1982, launched nonetheless higher-rated engines. The JT8D-219, rated at 21,000 kilos of thrust, featured a redesigned low-pressure turbine, a brand new high-pressure turbine, aerodynamically improved airfoils, a five-percent enhance in thrust, and a two-percent discount in gas burn.
First flying on December 17, 1984, the twin-jet, with a 160,000-pound most take off weight, provided a 2,502-nautical mile vary, attained by the use of 1,160 US gallons of further, decrease deck hold-installed supplementary gas tanks. Finnair, which had operated the DC-9-14/15, -40, and -50, served because the model’s launch buyer, working the longest, nonstop MD-80 flight on November 14, 1985, when it lined the three,406-mile distance between Montreal and Helsinki in seven hours, 26 minutes. Transwede, of Sweden, inaugurated the primary revenue-earning trans-Atlantic flight from Stockholm to Ft. Lauderdale with intermediate stops in Oslo and Gander.
With the intention to provide a lower-capacity counterpart extra appropriate to reduced-demand sectors, and to extra successfully compete with the 737-300 Boeing designed for this market, McDonnell-Douglas provided the primary, and solely, dimensionally-divergent variant, the MD-87, which had advanced from its earlier, DC-9 Tremendous XX research for a 100- to 120-passenger plane powered both by Pratt and Whitney JT8D-200 sequence or CFM Worldwide CFM56-3 turbofans and providing a 110,000- to 120,000-pound gross weight. The variant, with a 16.5-foot shorter fuselage, featured a brand new, 130.5-foot total size and had a 38,726-pound most payload, or the identical because the DC-9-50’s.
Due to the decreased moment-arm of the shorter fuselage, vertical axis management required a larger-area, ten-inch taller fin, seen by the extension above its conventional t-tail mating level and leading to a brand new, 31.2-foot total top. It additionally launched low-drag flap hinges and fairings, a fillet fairing between the fuselage and the engine pylon, and a reduced-drag, blade-shaped tailcone.
Initially powered by the 20,000 thrust-pound JT8D-217B, however later retrofitted with the decrease gas consumption -217C model, the MD-87 had a 2,372-nautical mile vary with 130 passengers and home reserves, though further, MD-83 sort gas tankage within the decrease holds elevated this to 2,833 miles.
First taking to the skies on December 4, 1986, it obtained its FAA sort certificates on October 21 of the next 12 months, and was inaugurated into service on December 17 with Austrian Airways from Vienna to Zagreb.
The final, and most superior, of the 5 variations, the MD-88, reintroduced the unique fuselage dimensions and was introduced on January 23, 1986 after launch buyer Delta Air Traces positioned an preliminary order to 80 of the kind. Supplied with 21,000 thrust-pound JT8D-219 turbofans, the model, most carefully based mostly on the MD-82, featured elevated composite materials to scale back construction weight, a brand new passenger cabin with a wider aisle and modernized overhead storage compartments, and a complicated, glass cockpit, the latter comprised of an digital flight instrument system (EFIS), a flight administration system (FMS), and an inertial reference system (IRS). It retained the MD-87’s blade-shaped tailcone.
First flying on August 15, 1987 and FAA-certified 4 months afterward December 9, the MD-88 entered scheduled service with Delta on January 5, or simply over 22 years after it had operated the world’s first passenger-carrying service with the -14 sequence on December 8, 1965. It had additionally operated the stretched DC-9-30 and the MD-82.
III
The 1,000th MD-80 had been delivered on March 29, 1992, and by December of 1997, 1,150 of the kind had been in service with 60 worldwide airways. The design, partially succeeded by its superior, re-engined MD-90 counterpart and Boeing’s personal Subsequent Era 737 household after that producer’s acquisition of McDonnell-Douglas, nonetheless grew to become its best-selling pure-jet business airliner, exceeding gross sales of the DC-8, the Tremendous DC-8, the DC-9 itself, the DC-10, the MD-11, the MD-90, and the MD-95/717, the final supply of which had occurred on December 21, 1999, when an MD-83 had been handed over to TWA, ending twenty years of manufacturing. Mixed with the 976 gross sales of the unique, short-fuselage DC-9, it grew to become the third best-selling twin-jet after Boeing’s 737 and Airbus Industrie’s A-320 household, with a collective 2,167 airframes having been constructed.