The McDonnell – Douglas MD-80

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The fuselage's stretch capacity, inherently incorporated in the basic design of DC-9, had characterized its program, resulting in larger and divergent versions in four dimensions, including the DC-9-30 initially elongated over the reference series -10/14/15, the later DC-9-40 and the last DC-9-50, the latter with capacity for 49 passengers more than the original maximum of the double jet.

The DC-9, based on the four principles of robustness, simplicity, reliability and low-cost design, had been McDonnell-Douglas's best-selling commercial aircraft, so much so that, in fact, it took off or landed somewhere in the world every seven seconds, which serves more than 570 cities with about 6,050 daily flights, and in 1979, the collective fleet had transported more than one billion passengers and registered more than 18 million hours with a dispatch reliability rate of almost 99 percent.

Its Pratt and Whitney JT8D engine, the most widely used engine with a numbering greater than 12,000 units, had not only provided a thrust thrust for all versions of the DC-9, but also boosted the Boeing 727, the Sud-Aviation SE.210 Super Caravelle, the Boeing 737 and the Dassault-Breguet Mercure 100.

Therefore, both the basic design of the DC-9 and its JT8D turbo fan offered the most optimal and cost-effective platform on which to base a successor of greater capacity, which needed to match the capacity of the DC-9-30 range, but exceed the DC-9 -50 of the economy.

Its fuselage, having not reached its stretch capacity limit, lent itself to a larger capacity housing, but its obstacle had been a power plant of sufficient thrust to maintain a payload, a range and acceptable performance parameters for its operators .

Based on the previous two-stage JT3D, which had fed both 707 and DC-8, the JT8D, a low-bypass, one-to-one turbo fan, was first run on April 7, 1961, arriving at the heavens for the first time on May 1 of the following year he rode a 707. Upon receiving FAA certification on February 9, 1963, as the JT8D-1 of 14,000 pounds of thrust, he had fed the 727-100 before if used by the DC-9 -10 and subsequently offered in several successive versions of greater thrust, the last of which was the JT8D-17R of 17,400 pounds of thrust.

A new generation variant, which provides the application for a definitive DC-9 section designated JT8D-109, had been one of the six demonstration power plants incorporating larger, single-stage fans developed for the Quiet Engine Program. NASA, which ran between 1972 and 1975, and two of its versions had registered more than 50 hours adapted to a modified DC-9-32. The design of a new development, the JT8D-209 of 18,500 pounds of thrust, began in 1974 and was first executed two years later, in a McDonnell-Douglas Advanced Medium STOL Transport (AMST) in March 1977.

Although initially a new supercritical wing had been considered, the aircraft, destined for short to medium-range sectors that implied higher ascent and descent ratios with respect to actual cruise profiles, could not fully exploit such a new design, its benefits resulting unable to justify its higher development costs. The existing DC-9 wing, which incorporates root and tip extensions and high elevation modified devices, would provide the required performance, economy and range parameters.

Several initial iterations, based mainly on the DC-9-50 and all with fuselage stretches for higher capacities, larger area wings and two refined turbofan, had included the ref-stretched DC-9-50RS, the super stretched DC refan -9-50RSS, the DC-9-55 and the DC-9-60, while a DC-9QSF, intended for Japanese operators as a twin turboprop replacement NAMC YS-11, combined a fuselage DC-9- 40 with two JT8D-209 engines of 18,000 pounds of thrust and a larger two-foot wing, allowing the 114,000-pound aircraft to operate from 4,000-foot runways with 120 passengers.

However, the cost limitations and design complexities dictated a simpler and more direct version that incorporated the longer fuselage, the increased area wings and the JT8D-209 turbofans, but maintained the similarity of the cabin with all the previous variants of DC-9. Skipping the DC-9-60 and DC-9-70 sequences, the definitive aircraft, designated DC-9-80-or DC-9 Super 80, to more accurately reflect the planned year of inauguration of the service, was launched in October 20 of 1977 with the reception of 27 firm orders and 13 optional orders from Swissair, Austrian Airlines and Southern Airways, together with a letter of intent from LAV Lineas Aeropostal Venezolanas, all of which had been previous operators of DC-9. Visualized as a complement of greater capacity for its DC-9 fuselage and a replacement for higher-cost tri-jets, it was intended to provide service in mature markets whose environmental and noise restrictions had prevented the replacement of larger capacity equipment, the Aircraft offered lower noise footprint, greater range and capacity, and the lowest seat mile costs of any comparable double jet.

According to the then president of Douglas Aircraft Company, John C. Brizendine, "in recent years … we have realized the need to conserve energy, protect the environment and produce more and more economically efficient airplanes. (DC -9 Super 80) is specifically designed to meet the requirements of our industry for years to come. These include environmental compatibility, energy efficiency, economic operation and a spacious and comfortable interior. "

McDonnell-Douglas boasted the aircraft, "The DC-9 Super 80 is a mix of proven design with available low-risk technology for greater effectiveness, (but) the remarkable DC-9 reliability and lower operating costs are maintained ".

Although it had been based on this twin from the previous generation, it introduced several advanced features.

A stretch of the fuselage, achieved through a plug of eight frames forward of the wing and a single frame insert back, resulted in a total length of 147.10 feet, increasing the maximum capacity to 172, or 33 more than the DC- 9 -50 and an astonishing 82 more than the initial DC-9-10, and producing the most mass-drawn commercial aircraft so far. The front, left and rear, ventral exits had been retained, both equipped with extendable air ladders, but a left, rear service door had been introduced, located just a few feet from the engine. Aeritalia of Naples, Italy, manufactured its fuselage panels.

A new 10.6-foot central section and two-foot parallel rope tip extensions, resulting in the third dimensionally divergent DC-9 wing, produced an area of ​​28 percent, fuel capacity of 57 percent and an increase in 11 percent efficiency.

Measuring 107 feet, 10 1/4 inches, the aerodynamic profile, with a sweep of 24 degrees back in its fourth string, an aspect ratio of 9.62, three degrees of dihedral and an area of ​​1,239 square feet, had been composed by four precision machined wing cladding panels that had been transformed from 14,000-pound ingots measuring 60 inches wide, 15 inches long and 30 inches thick by the Reynolds Metal Company of McCook, Illinois.

The all-metal structure of two stringers, with riveted stringers in the form of a section, featured front edge slats with three full-section positions with a new intermediate configuration to reduce take-off drag and improve ascent performance to higher gross weights; larger, double groove and rear edge fins covering 67 percent of the section and lowering the plane's loss rate; three spoiler panels, the two exteriors of which could be used as flight and ground lift dumpers; and spoilers. All but the latter were hydraulically operated, while the ailerons were manually operated. A vortillon fence under the wing ensured adequate air flow. By providing 1,520 US gallons of additional fuel tank, it also offered a major area main landing gear bay.

The horizontal, electrically operated variable-incidence tail covering 40.2 feet, or 3.6 feet more than that of the DC-9-50, retained the characteristic t-tail configuration of the design and sports elevators equipped with handles, while the vertical fin, With a total aircraft height of 30.2 feet, it had a hydraulically operated rudder. He had been 1.4 feet taller than the DC-9-50.

Its Pratt and Whitney JT8D-209 turbofan, mounted on both sides of the stern fuselage and retaining the original thrust-type inverters, was based on the core of the previous JT8D-9, but introduced a 49-inch wider fan and An advanced, low-pressure compressor, which produces 18,500 pounds of thrust along with an additional 750 pounds of automatic power reserve (APR), generated during engine loss conditions. The fan of a larger diameter stage, which drove a larger mass of hot core section bypass air, along with a more efficient intermingling hot and cold air outlet, and a greater sound absorption material in its gondola and surrounding carcass produced numerous improvements including increased thrust capacity; a higher derivation ratio of 1: 1.78 compared to the previous JT8D 1: 1; lower output speed; an 11 percent decrease in specific fuel consumption; and a significantly smaller noise footprint than the medium-range tri-jets that were intended to be replaced.

Using Kevlar-reinforced aluminum honeycomb reinforcements to reduce weight with graphite ribbon caps on the outer barrel of its nasal cover and its upper and two lower deck doors, the gondola, 21.1 feet long, was 4.5 feet longer than the JT8D-9 and, therefore, presented engineering challenges in relation to its mounting on the body of the DC-9, although longer.

The DC-9 Super 80 retained the Cleveland Pneumatic Retractable, Tricycle, Double Wheel, Hydraulic, Landing Gear equipped with Goodyear wheels, tires and disc brakes; Anti-skid units Hydro-Aire Mk IIIA; and Douglas executed the air brake cooling. The nose wheel was adjustable at 27 degrees on each side.

Although the Super 80 maintained a common pilot type rating with the DC-9, however, it offered several advances in the cockpit, including a digital control and flight guidance system designed by the Sperry Sperry Flight Systems Division Rand Corporation, which integrated the performance of seven flights control subsystems on two identical digital computers; cathode ray tube (CRT) screens; a digital fuel quantity measurement system; a dial-a-flap system; and Category IIIA automatic landing capability of 50 feet of decision height (DH) and 700 feet of visual range on the runway (RVR). An electronic performance management system introduced later provided automatic tilt and thrust to achieve optimum speed and fuel consumption during the ascent, cruise and descent profiles of the aircraft.

The "wide-looking" cabin, 101 feet long, featured a ceiling with a wide, contoured and sculpted acoustic treatment that mixed with the closed upper storage compartments; aluminum side panels sculpted around the windows; fluorescent lighting; a 19-inch hall; and economy class seats set to five, two or three or two, which halved the number of intermediate seats traditionally associated with six-in-one arrangements.

The interior decoration, which varied from a conservative business-oriented event to bright patterns and bright colors, was determined by the operator and designed by McDonnell-Douglas, whose interior design teams often made trips to the countries of origin of the airlines to absorb local culture and customs and then turn that experience into motifs that reflect the area or the country. Synthetic wool and wool blends were used as standard for seat covers and carpets.

Class and seat configuration vary by operator. An agreement of 137 double-class passengers, for example, involved 12 first-class seats with four seats in a 38-inch field and 125 economy-class seats with five seats in a 34-inch field, while class densities The only one included 155 passengers on a 32/33-inch pitch, 167 charter seats on a 30-inch pitch, or a maximum of 172 high-density passengers, the latter with capacity for a single galley installation.

The interior noise reduction was achieved by an insulating Mylar blanket reinforced with fabric on fiberglass.

The elongated DC-9 introduced a new pressurization and air circulation system, which replaced cabin air at higher frequencies, and its potable water system featured in-line heaters in all of its water lines. A higher capacity auxiliary power unit (APU) executed its environmental control system on the ground.

The longer fuselage of the aircraft significantly increased the volume of the luggage compartment and cargo of the lower deck, whose front, center and rear holds, respectively, covered 434, 376 and 443 cubic feet.

The DC-9-80 retained 80 percent of the key maintenance features of the DC-9-50.

Like all of its previous predecessors of shorter fuselage, the aircraft had been designed for short-sector self-service operations and rapid response from short aerodromes of limited facilities, with its greatest thrust, larger area wings, self-contained air ladder, Auxiliary power unit for environmental conditioning and engine starting, low ground profile to facilitate service, loading and maintenance, and the ability to operate two or more sectors without refueling. Most delivery times required little more than luggage carts.

With a maximum structural payload of 40,112 pounds, the DC-9-81, as designated in its initial variant, had a gross weight of 147,000 pounds, although it had then increased to 149,500 pounds with improved engines, and a maximum weight of 128,000-pound landing. Their normal and maximum cruising speeds were, respectively, Mach 0.76 and 0.80. Range, with 155 single class passengers and national reserves, was 1,564 nautical miles.

Piloted by Douglas Chief Engineering Pilot HH "Knick" Knickerbocker, John P. Laine Project Pilot and Virginia "Ginny" Flight Test Engineer A. Claire, the first DC-9 Super 80 and the 909th twin jet in Leaving Long Beach assembly line, he made his first flight from Runway 30 of the Long Beach Municipal Airport on October 18, 1979 with the DACO 80 badge for "Douglas Aircraft Company 80".

Following a 25-mile circular pattern on the water, the long and thin fuselage aircraft, with a capacity for 13,100 pounds of test equipment, completed a successful two-hour and 50-minute basic maneuver test exit before landing at the Facility of Flight Operations of McDonnell-Douglas in Yuma, Arizona, where the Chief of Engineering Pilots concluded: "The ground handling of the Super 80 is even better than the other DC-9s. It also seemed quite stable in flight … The new engines were impeccable, and the reverse thrust was very effective on landing … I think the Super 80 is a great plane and will live up to all our expectations. "

The flight test program of three 1,085-hour and $ 36 million aircraft, which involved the first flights of the N1002G prototype on December 6, 1979 and N1002W on February 29, 1980, led to FAA certification seven months later , on August 26, under an amendment to the original type certificate of DC-9.

First delivered to the Swissair launch client on September 12, which had operated before the DC-9-15, -30 and -50 series, it was inaugurated on scheduled service on October 5 from Zurich to Frankfurt, becoming the commercial aircraft pure more silent. The joint launch customer Austrian Airlines, which had also operated a fleet of DC-9-30 and -50, opened its first revenue service 21 days later, on October 26, from Vienna to Zurich.

To adopt the McDonnell-Douglas designation scheme, the DC-9-80, or DC-9 Super 80, was renamed "MD-80" in 1983, its initial version was called "MD-81".

II

Development of the Pratt and Whitney JT8D-209 base engine, which resulted in additional increased versions of an additional 20,000 pounds of thrust -217, the origin of which was the 1979 requirement for a takeoff and short landing aircraft (STOL) to operate within the Japanese domestic market. An iteration projected at that time, designated DC-9 Super 80SF, would have matched the fuselage of the DC-9-40 with the wing and motors of the DC-9-80, but the higher thrust JT8D-217, applied to the dimensions of the existing fuselage, they have provided most of the desired performance. As a result, a second variant, designated MD-82 and first announced on April 16, 1979, featured improved 20,000-pound turbofans with 850 pounds of automatic power reserve, a payload of 44,024 pounds and a range of 2,050 miles with 155 passengers First flying on January 8, 1981, it received its FAA type certification six months later, on July 31, with a maximum initial takeoff weight of 147,000 pounds, although the 1982 option of the JT8D engines -217A further increased this to 149,500 pounds, which resulted in even higher payload and range capabilities.

Republic Airlines, the July 1, 1978 merger of North Central and Southern Airways, had been the launch client of the version, having been the world's largest DC-9 operator with -10s, -30s and -50s series, a which its eight MD-82s were finally added.

The variant had been involved in two unique programs. The first one, which took place in October 1982, involved the innovative lease of 20 MD-82 to American Airlines, so McDonnell-Douglas agreed to assume maintenance and training costs. This allowed the purchase in February 1984 of 67 aircraft, at attractive prices and with low cancellation penalties, to be delivered in blocks of ten to 25 cells, each of which had been confirmed 24 months before the expected delivery date . Becoming the pillar of American's short-to-medium-range fleet to facilitate downtown connections in Chicago and Dallas, the plane, configured for 142 first-class and economy-class passengers, was finally number 234, the total single type largest in the world outside the former USSR.

The second innovative transaction occurred on April 12, 1985, when the Shanghai Aviation Industrial Corporation agreed to build 25 MD-82 in the People's Republic of China.

An extended range successor, designated MD-83 and first announced on January 31, 1982, introduced even higher engines. The JT8D-219, with a power of 21,000 pounds of thrust, featured a redesigned low-pressure turbine, a new high-pressure turbine, aerodynamically improved profiles, a five percent thrust increase and a two percent reduction in the fuel consumption.

First flying on December 17, 1984, the double jet, with a maximum takeoff weight of 160,000 pounds, offered a range of 2,502 nautical miles, reached through 1,160 US gallons of additional supplementary fuel tanks installed on the deck of the bottom cover. Finnair, which had operated DC-9-14 / 15, -40 and -50, served as the launch client for the version, operating the longest nonstop flight MD-80 on November 14, 1985, when it covered 3,406 miles distance between Montreal and Helsinki in seven hours, 26 minutes. Transwede, from Sweden, opened the first transatlantic flight that generates revenue from Stockholm to Ft. Lauderdale with intermediate stops in Oslo and Gander.

In order to offer a lower capacity counterpart more suitable for reduced demand sectors and compete more effectively with the Boeing 737-300 designed for this market, McDonnell-Douglas offered the first and only dimensionally divergent variant, the MD -87 , which had evolved since its previous studies DC-9 Super XX for a 100 to 120 passenger aircraft powered by the JT8D-200 series of Pratt and Whitney or CFM International CFM56-3 CFM56-3 turbofans and offered between 110,000 and 120,000- Pound gross weight. The variant, with a shorter fuselage of 16.5 feet, had a new total length of 130.5 feet and had a maximum payload of 38,726 pounds, or the same as the DC-9-50.

Due to the decrease in the moment arm of the shorter fuselage, vertical axis control required a larger, ten-inch higher fin, visible by the extension above its traditional T-tail coupling point and giving as resulted in a new total height of 31.2 feet. It also introduced hinges and low resistance flap fairings, a fillet fairing between the fuselage and the engine pylon, and a low-resistance blade-shaped back cover.

Initially powered by the JT8D-217B of 20,000 pounds of thrust, but then adapted with the -217C version of lower fuel consumption, the MD-87 had a range of 2,372 nautical miles with 130 passengers and national reserves, although additional, type fuel MD-83 the tankage in the lower wineries increased this to 2,833 miles.

On December 4, 1986, he first launched into the heavens, received his FAA-type certificate on October 21 of the following year and opened on December 17 with Austrian Airlines from Vienna to Zagreb.

The latest and most advanced of the five versions, the MD-88, reintroduced the original dimensions of the fuselage and was announced on January 23, 1986 after the launching client Delta Air Lines placed an initial order at 80 of the type. Offered with 21,000 JT8D-219 pounds of thrust turbofans, the version, based more closely on the MD-82, featured a larger composite material to reduce the weight of the structure, a new passenger cabin with a wider aisle and storage compartments. Modernized superior storage, and an advanced, glass cabin, the latter composed of an electronic flight instrument system (EFIS), a flight management system (FMS) and an inertial reference system (IRS). It retained the blade-shaped back cover of the MD-87.

First flight on August 15, 1987 and certified by the FAA four months later, on December 9, the MD-88 entered scheduled service with Delta on January 5, or just over 22 years after operating the first service of passenger transport in the world with the – 14 series on December 8, 1965. The extended DC-9-30 and the MD-82 had also operated.

III

The MD-80 number 1,000 was delivered on March 29, 1992 and, in December 1997, 1,150 of the type had been in service with 60 airlines worldwide. The design, partially achieved by its advanced and reconditioned MD-90 counterpart and Boeing's Next Generation 737 family after the manufacturer's acquisition of McDonnell-Douglas, however became its best-selling pure jet commercial aircraft, surpassing the sales of the DC-8, the Super DC-8, the DC-9 itself, the DC-10, the MD-11, the MD-90 and the MD-95/717, whose last delivery took place on the 21st of December 1999, when an MD-83 had been delivered to TWA, ending two decades of production. Combined with the 976 sales of the original short-body DC-9, it became the third best-selling twin aircraft after 737 of Boeing and the A-320 family of Airbus Industrie, with a total of 2,167 aircraft built.