McDonnell Douglas DC-9
The McDonnell Douglas DC-9 is an American five-abreast, single-aisle aircraft designed by the Douglas Aircraft Company. It was initially produced as the Douglas DC-9 prior to August 1967, after which point the company had merged with McDonnell Aircraft to become McDonnell Douglas.
Even before the introduction of its first jetliner, the high-capacity Douglas DC-8, in 1959, Douglas was interested in producing an aircraft suited to smaller routes. As early as 1958, design studies were conducted; approval for the DC-9, a smaller all-new jetliner, came on April 8, 1963. The DC-9-10 first flew on February 25, 1965, and gained its type certificate on November 23, to enter service with Delta Air Lines on December 8.
The DC-9 is powered by two rear-mounted Pratt & Whitney JT8D low-bypass turbofan engines under a T-tail for a cleaner wing aerodynamic. It has a two-person flight deck and built-in airstairs to better suit smaller airports. The aircraft was capable of taking off from 5,000 ft runways, connecting small cities and towns in the jet stream of air travel where jet service was previously impossible.
The Series 10 aircraft are 104 ft long for typically 90 coach seats. The Series 30, stretched by 15 ft to seat 115 in economy, has a larger wing and more powerful engines for a higher maximum takeoff weight ; it first flew in August 1966 and entered service in February 1967.
The Series 20 has the Series 10 fuselage, more powerful engines, and the Series 30's improved wings; it first flew in September 1968 and entered service in January 1969.
The Series 40 was further lengthened by 6 ft for 125 passengers, and the final DC-9-50 series first flew in 1974, stretched again by 8 ft for 135 passengers.
When deliveries ended in October 1982, 976 had been built.
Smaller variants competed with the BAC One-Eleven, Fokker F28, and Sud Aviation Caravelle, and larger ones with the original Boeing 737.
The original DC-9 was followed by the second generation in 1980, the MD-80 series, a lengthened DC-9-50 with a larger wing and a higher MTOW. This was further developed into the third generation, the MD-90, in the early 1990s, as the fuselage was stretched again, fitted with V2500 high-bypass turbofans, and an updated flight deck. The shorter and final version, the MD-95, was renamed the Boeing 717 after McDonnell Douglas's merger with Boeing in 1997; it is powered by Rolls-Royce BR715 engines. The DC-9 family was produced between 1965 and 2006 with a total delivery of 2441 units: 976 DC-9s, 1191 MD-80s, 116 MD-90s, and 155 Boeing 717s. As of August 2022, 250 aircraft remain in service: 31 DC-9s, 116 MD-80s, and 103 Boeing 717s, while the MD-90 was retired without freighter conversion.
Development
Origins
During the late 1950s, Douglas Aircraft studied a short- to medium-range airliner to complement their then-sole jetliner, the high-capacity, long-range DC-8. The Model 2067, a four-engined aircraft sized for medium-range routes was studied in depth, but work on it was abandoned after the proposal did not receive enough interest from airlines. In 1960, Douglas signed a two-year contract with the French aeronautics company Sud Aviation for technical cooperation; under the terms of this contract, Douglas would market and support the Sud Aviation Caravelle and produce a licensed version if sufficient orders were forthcoming from airlines. However, none were ever ordered from the company, leading to Douglas returning to its design studies after the co-operation deal expired.In 1962, design studies were underway into what would become the DC-9, known as Model 2086. The first envisioned version seated 63 passengers and had a gross weight of 69,000 lb. This design was changed into what would be the initial DC-9 variant. During February 1963, detailed design work commenced. On April 8, 1963, Douglas announced that it would proceed with the DC-9. Shortly thereafter, Delta Air Lines placed the initial order for the DC-9, ordering 15 aircraft along with options for another 15. By January 1965, Douglas had garnered orders for 58 DC-9 as well as options for a further 44.
Unlike the competing but larger Boeing 727 trijet, which used as many 707 components as possible, the DC-9 was developed as an all-new design. Throughout its development, Douglas had placed considerable emphasis on making the airliner as economic as possible, as well as to facilitate its future growth. The adoption of the Pratt & Whitney JT8D low-bypass turbofan engine, which had already been developed for the Boeing 727, enabled Douglas to benefit from the preexisting investment. Pratt & Whitney had long collaborated with Douglas on various projects, thus their engine was a natural choice for the company. In order to reduce the considerable financial burden of its development, Douglas implemented one of the first shared-risk production arrangements for the DC-9, arranging for de Havilland Canada to produce the wing at its own financial cost in return for promises on prospective future production orders.
Entry into service
The pace of development on the program was rapid. The first DC-9, a production model, flew on February 25, 1965. The second DC-9 flew a few weeks later, with a test fleet of five aircraft flying by July. Several key refinements to the aircraft were made during flight testing, such as the replacement of the original leading-edge slat design to achieve lower drag. The flight test program proceeded at a rapid pace; the initial Series 10 received airworthiness certification from the Federal Aviation Administration on November 23, 1965, permitting it to enter service with Delta Air Lines on December 8.Through the DC-9, Douglas had beaten rival company Boeing and their 737 to enter the short-haul jet market, a key factor that contributed to the DC-9 becoming the best selling airliner in the world for a time. By May 1976, the company had delivered 726 aircraft of the DC-9 family, which was more than double the number of its nearest competitor. However, following decades of intense competition between the two airliners, the DC-9 would eventually be overtaken as the world's best selling airliner by Boeing's 737.
From the onset of its development, the DC-9 had been intended to be available in multiple versions to suit varying customer requirements; the first stretched version, the Series 30, with a longer fuselage and extended wing tips, flew on August 1, 1966, entering service with Eastern Air Lines in 1967. The initial Series 10 was followed by the improved [|-20], [|-30], and [|-40] variants. The final DC-9 series was the [|-50], which first flew in 1974.
Production
The DC-9 series, the first generation of the DC-9 family, would become a long term commercial success for the manufacturer. However, early production of the type had come at a higher unit cost than had been anticipated, leading to DC-9s being sold at a loss. The unfavorable early economics of the type negatively impacted Douglas, pushing it into fiscal hardship. However, the high customer demand for the DC-9 made the company attractive for either an acquisition or a merger; Douglas would merge with the American aerospace company McDonnell Aircraft to form McDonnell Douglas in 1967.The DC-9 family is one of the longest-lasting aircraft in production and operation. It was produced on the final assembly line in Long Beach, California, beginning in 1965, and later was on a common line with the second generation of the DC-9 family, the MD-80, with which it shares its line number sequence. Following the delivery of 976 DC-9s and 108 MD-80s, McDonnell Douglas stopped series production of the DC-9 in December 1982. The last member of the DC-9 family, the Boeing 717, was produced until 2006. The DC-9 family was produced in total units: 976 DC-9s, 1191 MD-80s, 116 MD-90s, and 155 Boeing 717s. This compared to 2,970 Airbus A320s and 5,270 Boeing 737s delivered as of 2006.
Enhancement studies
Studies aimed at further improving DC-9 fuel efficiency, by means of retrofitted wingtips of various types, were undertaken by McDonnell Douglas, but these did not demonstrate significant benefits, especially with existing fleets shrinking. The wing design makes retrofitting difficult. Between 1973 and 1975, McDonnell Douglas studied the possibility of replacing engines on the DC-9 with the JT8D-109 turbofan, a quieter and more efficient variant of the JT8D. This progressed to the flight-test stage, and tests achieved noise reduction between 8 and 9 decibels depending on the phase of flight. No further aircraft were modified, and the test aircraft was re-equipped with standard JT8D-9s prior to delivery to its airline customer.Further developments (DC-9 family)
Two further developments of the original or first generation DC-9 series used the new designation with McDonnell Douglas initials followed by the year of development. The first derivative or second generation was the MD-80 series and the second derivative or third generation was the MD-90 series. Together, they formed the DC-9 family of 12 aircraft members, and if the DC-9- designation were retained, the family members would be: First generation, second generation, and third generation. The Series 10 was the smallest family member and the Series 90 was the largest.Second generation (MD-80 series)
The original DC-9 series was followed in 1980 by the introduction of the second generation of the DC-9 family, the MD-80 series. This was originally called the DC-9-80. It was a lengthened DC-9-50 with a higher maximum takeoff weight, a larger wing, new main landing gear, and higher fuel capacity. The MD-80 series features a number of variants of the JT8D turbofan engine that had higher thrust ratings than those available on the original DC-9 series. The MD-80 series includes the MD-81, MD-82, MD-83, MD-88, and shortest variant, the MD-87.Third generation (MD-90 series)
; MD-90The MD-80 series was further developed into the third generation, the MD-90 series, in the early 1990s. It has yet another fuselage stretch, an electronic flight instrument system, and completely new International Aero V2500 high-bypass turbofan engines. In comparison to the very successful MD-80, relatively few MD-90s were built.
; Boeing 717
The shorter and final variant, the MD-95, was renamed the Boeing 717 after McDonnell Douglas's merger with Boeing in 1997 and before aircraft deliveries began. The fuselage length and wing are very similar to those of the DC-9-30, but much use was made of lighter, modern materials. Power is supplied by two BMW/Rolls-Royce BR715 high-bypass turbofan engines.
; Comac ARJ21
China's Comac ARJ21 is derived from the DC-9 family. The ARJ21/C909 is built with manufacturing tooling from the MD-90 Trunkliner program. As a consequence, it has the same fuselage cross-section, nose profile, and tail.