The DC-9 was designed specifically to operate from short runways and on short- to medium-range routes so that the speed, comfort and reliability of jet transportation could be extended to hundreds of communities previously served only by propeller-driven airliners.
Smaller than the DC-8, the trim DC-9 has a distinctive high-level horizontal stabilizer atop the rudder, commonly called a "T" tail. Two engines mounted on the aft fuselage power the aircraft at cruising speeds exceeding 500 mph (800 km/h) and altitudes over 30,000 feet (9,144 m).
Design, development and production of the DC-9 was centered in Long Beach, California, at what is now the Douglas Products Division of the Boeing Commercial Airplane Group, where 976 of the twin jets were built during an 18-year production run. The first flight was February 25,1965; the final DC-9 was delivered in October 1982.
There are five basic DC-9 versions, designated Series 10, Series 20, Series 30, Series 40 and Series 50. Several models in each series provide operators maximum efficiency for diverse combinations of traffic density, cargo volume and route distances to more than 2,000 miles (3,218 km). All models use variants of the reliable workhorse Pratt & Whitney JT8D engine.
Series 10: The first in the twinjet family, the fuselage length of the Series 10 DC-9 is 104.4 feet (31.8 m), accommodating up to 90 passengers with 600 cubic feet (16.9 m3) of cargo space below the floor. Wingspan is 89.4 feet (27.2 m). Engines can be JT8D-5s or JT8D-7s, with takeoff thrust ratings of 12,250 to 14,000 pounds.
Series 20: The DC-9 Series 20, although numbered second in the sequence of models, actually is the fourth member of the family. This high-performance version was announced in December 1966, and the first delivery was made in December 1968. The Series 20 is designed for operation from very short runways. It combines the fuselage of the DC-9 Series 10 with a high-lift wing developed for the Series 30. Power is provided by two JT8D-9s with 14,500 pounds thrust each, or 15,000-pound JT8D-11s.
Series 30: Fuselage of the Series 30 DC-9, actually second developed, is nearly 15 feet longer than the Series 10, at 119.3 feet (36.3 m), providing seats for up to 115 passengers and cargo space to 895 cubic feet (25.3 m3). Series 30 wingspan was increased to 93.4 feet (28.4 m), and a high-lift wing system of leading edge slats gives the Series 30 excellent short-field performance. The first of the type began airline service in February 1967.
Most of the Series 30s are powered by either JT8D-7 or JT8D-9 engines. Others are equipped with JT8D-11 or the JT8D-15, with 15,500 pounds of thrust. The Series 30 is the most widely used member of the DC-9 family, accounting for approximately 60 percent of the entire fleet.
Series 40: To again meet airline demands for a DC-9 with more capacity, the Series 40 was developed with a fuselage length of 125.6 feet (38.3 m). Seating is available for up to 125 passengers, 10 more than the popular Series 30s. Below-floor cargo space totals 1,019 cubic feet (28.8 m3). The Series 40 uses the same wing as the Series 30. Series 40 engines are JT8D-9s, JT8D-11s or JT8D-15s. The model entered service in March 1968.
Series 50: The fifth and largest DC-9 version is extended to 133.6 feet (40.7 m) long, permitting installation of five more rows of seats than the Series 30. Maximum passenger capacity is up to 139, with cargo capacity increased similarly. Wingspan is the same as for the Series 30. Engines are either JT8D-15s or JT8D-17s, which are rated at 16,000 pounds. Airline operations with the Series 50 began in August 1975.
All Models: Common to all versions of the DC-9 are the features that make them ideal for short- and medium-range flights providing direct service between small or large airports. All have built-in boarding stairs for use where jetways are not available. The low ground clearance puts the lower deck cargo bays at waist height, to allow loading and unloading without a conveyor or loading platform. The cockpit is designed for a two-member crew.
Passenger cabins of the DC-9s are designed for optimum passenger comfort and convenience. Economy class seating is five across -- an arrangement consistently preferred in passenger surveys to the six-across seating in other single-aisle jetliners. A "wide look" interior introduced in 1973 provides a greater feeling of spaciousness than in earlier models and offers enclosed overhead racks for carry-on bags.
Thirty years after beginning operations and more than a decade after the final aircraft rolled off the assembly line, DC-9s remain a mainstay in many airlines, still building a worldwide reputation for reliability and durability unmatched by any other aircraft. The fleet makes more than 3,500 flights per day, with each aircraft averaging more than five hours of revenue service daily. Total revenue service hours total more than 50 million.
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