McDonnell Douglas DC-9

The McDonnell Douglas DC-9 (initially known as the Douglas DC-9) is a twin-engine, single-aisle jet airliner. It was first manufactured in 1965 with its maiden flight later that year. The DC-9 was designed for frequent, short flights. The final DC-9 was delivered in October 1982.

The DC-9 was followed in subsequent modified forms by the MD-80, MD-90 and Boeing 717. With the final two deliveries of the 717 in 2006, production of the DC-9/MD-80/90/717 aircraft family ceased after 41 years and nearly 2,500 units built.

Design and development
During the 1950s, Douglas Aircraft began studying a short-medium range airliner to complement its higher capacity, long range DC-8. A medium range, four-engine design was studied as the Model 2067, but it did not receive enough interest from airlines and was abandoned. Then in 1960, Douglas signed a two-year contract with Sud Aviation for technical cooperation. As part of the agreement Douglas would help market and support the Sud Aviation Caravelle along with license-production of an American version if orders were high enough. However, no orders were received and Douglas returned to its design studies after the two years.

In 1962, early design studies were underway. The first version seated 63 passengers and had a gross weight of 69,000 lb (31,300 kg). This design was changed into what would be initial DC-9 variant. Douglas officially gave approval to produce the DC-9 on April 8, 1963. Unlike the competing but slightly larger Boeing 727 trijet, which used as many 707 components as possible, the DC-9 was an all-new design. The DC-9 features two rear fuselage-mounted Pratt & Whitney JT8D turbofan]] engines, relatively small, efficient wings, and a T-tail. The DC-9's maximum takeoff weight was limited to 80,000 lb (36,300 kg) for a two-person flight crew by Federal Aviation Agency regulations at the time. DC-9 aircraft have 5 seats across for economy seating. The airplane seats 80 to 135 passengers depending on version and seating arrangement. (Note: DC stands for Douglas Commercial. )



The DC-9 was designed for short to medium routes, often to smaller airports with shorter runways and less ground infrastructure than the major airports being served by larger designs like the 707 and DC-8. Consequently, accessibility and short field characteristics were called for. The tail mounted engine design facilitated a clean wing designs without engine pods, which had numerous advantages. First, flaps could run the entire span of the wing, unimpeded by pods on the leading edge and engine blast concerns on the trailing edge. This simplified the design, improved airflow at low speeds and enabled lower takeoff and approach speeds, thus lowering field length requirements and keeping wing structures light. The second advantage of the tail-mounted engines was the reduction in foreign object damage from ingested debris from runways and aprons. Third, the absence of engines in underslung pods provided a reduction in ground clearance, making the aircraft more accessible to baggage handlers and passengers. Turnarounds were simplified by built-in airstairs, including one in the tail, which shortened boarding and deplaning times. The problem of deep stalling, revealed by the loss of the BAC One-Eleven prototype in 1963, was overcome through various changes, including the introduction of vortilons, small surfaces beneath the wing's leading edge used to control airflow and increase low speed lift.

The first DC-9, a production ship, flew in February 1965. The second DC-9 flew a few weeks later and entered service with Delta Air Lines in late 1965. The initial Series 10 would be followed by the improved -20, -30, and -40 variants. The final DC-9 series was the -50, which first flew in 1974.

The DC-9 was a commercial success with 976 built when the production ended in 1982. The DC-9 is one of the longest lasting aircraft in operation. Its reputation for reliability and efficiency drove strong sales of its successors well into the 21st century. The DC-9 family is one of the most successful jet airliners with a total of over 2,400 units produced; it ranks third behind the second place Airbus A320 family with over 4,000 produced, and the first place Boeing 737 with over 6,000 produced.



Studies aimed at further improving DC-9 fuel efficiency, by means of retrofitted wingtips of various types, were undertaken by McDonnell Douglas. However these did not succeed in demonstrating significant benefits, especially with existing fleets shrinking. The wing design makes retrofitting difficult.

Legacy
The DC-9 was followed by the introduction of the MD-80 series in 1980. The MD-80 series was originally called DC-9-80 series. It was a lengthened DC-9-50 with a higher maximum takeoff weight (MTOW), a larger wing, new main landing gear, and higher fuel capacity. The MD-80 series features a number of variants of the Pratt & Whitney JT8D turbofan engine having higher thrust ratings than those available on the DC-9.

The MD-80 series was further developed into the McDonnell Douglas MD-90 in the early 1990s. It has yet another fuselage stretch, a glass cockpit (first introduced on the MD-88) and completely new International Aero V2500 high-bypass turbofan engines. In comparison to the very successful MD-80, relatively few MD-90 examples were built.

The final variant of the DC-9 family was the MD-95, which was renamed the Boeing 717-200 after McDonnell Douglas's merger with Boeing in 1997 and before aircraft deliveries began. The fuselage length and wing are highly similar to those found on DC-9-30 aircraft, but much use was made of lighter, modern materials. Power is supplied by two BMW/Rolls-Royce BR715 high bypass turbofan engines.

China's Comac ARJ21 is derived from the DC-9 family. The ARJ21 is built with manufacturing tooling from the MD-90 Trunkliner program. Consequently it has the same fuselage cross section, nose profile, and tail.

Series 10
The original DC-9 (later designated the Series 10) was the smallest DC-9 series. The -10 was 104.4 ft (31.8 m) long and had a maximum weight of 82,000 lb (37,000 kg). The Series 10 was similar in size and configuration to the BAC One-Eleven and featured a T-tail and rear mounted engines. Power was a pair of 12,500 lbf (56 kN) Pratt & Whitney JT8D-5 or 14,000 lbf (62 kN) JT8D-7 engines. A total of 137 were built. Delta Air Lines was the initial operator.

The Series 10 was produced in two main subvariants, the Series 14 and 15, although of the first four aircraft, three were built as Series 11s and one as Series 12. These were later converted to Series 14 standard. No Series 13 was produced. A passenger/cargo version of the aircraft with a 136 x 81 in side cargo door forward of the wing and a reinforced cabin floor, was certificated on March 1, 1967. Cargo versions included the Series 15MC (Minimum Change) with folding seats which can be carried at the rear of the aircraft, and the Series 15RC (Rapid Change) with seats removable on pallets. These differences disappeared over the years as new interiors have been installed.

The Series 10 was unique in the DC-9 family in not having leading edge slats. The Series 10 was designed to have short takeoff and landing distances without the use of leading edge high-lift devices. Therefore, the wing design of the Series 10 featured airfoils with extremely high maximum lift capability in order to obtain the stalling speeds necessary for short field performance.

Series 10 features
The Series 10 has an overall length of 104.4 feet (31.82 m), a fuselage length of 92.1 feet (28.07 m), a passenger cabin length of 60 feet (18.29 m), and a wingspan of 89.4 feet (27.25 m).

The Series 10 was offered with the 14,000 lbf (62 kN) thrust JT8D-1 and JT8D-7.

All versions of the DC-9 are equipped with an AlliedSignal (Garrett) GTCP85 APU as standard which is located in the aft fuselage.

The Series 14 was originally certificated at an MTOW of 85,700 lb (38,900 kg) but subsequent options offer increases to 86,300 and 90,700 lb (41,100 kg). The aircraft's MLW in all cases is 81,700 lb (37,100 kg). The Series 14 has a fuel capacity of 3,693 US gallons (with the 907 US gal centre section fuel). The Series 15, certificated on January 21, 1966, is physically identical to the Series 14 but has the increased MTOW of 90,700 lb (41,100 kg). Typical range with 50 passengers and baggage is 950 nmi (1,760 km), increasing to 1,278 nmi (2,367 km) at long range cruise. Range with maximum payload is 600 nmi (1,100 km), increasing to 1,450 nmi (2,690 km) with full fuel.

The DC-9 Series 10, as with all later versions of the DC-9 is equipped with a two crew analog flightdeck.

The aircraft is fitted with a passenger door in the port forward fuselage, and a service door/emergency exit is installed opposite. An airstair installed below the front passenger door was available as an option as was an airstair in the tailcone. This also doubled as an emergency exit. Available with either two or four overwing exits, the DC-9-10 can seat up to a maximum certified exit limit of 109 passengers. Typical all economy layout is 90 passengers, and 72 passengers in a more typical mixed-class layout with 12 first and 60 economy-class passengers.

All versions of the DC-9 are equipped with a tricycle undercarriage, featuring a twin nose unit and twin main units.

Series 20
{C This was designed to satisfy a Scandinavian Airlines request for improved short field performance by using the more powerful engines and improved wings of the -30 combined with the shorter fuselage used in the -10. Ten Series 20 aircraft were produced, all of them Model -21.

In 1969 a DC-9 Series 20 at Long Beach was fitted with an Elliott Flight Automation Head-up display by McDonnell Douglas and used for successful three month-long trials with pilots from various airlines, the Federal Aviation Administration, and the US Air Force.

Series 20 features
The Series 20 has an overall length of 104.4 feet (31.82 m), a fuselage length of 92.1 feet (28.07 m), a passenger cabin length of 60 feet (18.29 m), and a wingspan of 93.3 feet (28.44 m).

The DC-9 Series 20 is powered by the 15,000 lbf (67 kN) thrust JT8D-11 engine.

The Series 20 was originally certificated at an MTOW of 94,500 lb (42,900 kg) but this has been increased to 98,000 lb (44,000 kg), some 8% up on the higher weight Series 14s and 15s. The aircraft's MLW is 95,300 lb (43,200 kg) and MZFW is 84,000 lb (38,000 kg). Typical range with maximum payload is 1,000 nmi (1,900 km), increasing to 1,450 nmi (2,690 km) with maximum fuel. The Series 20, using the same wing as the Series 30 and indeed the Series 40 and 50, has a slightly lower basic fuel capacity than the Series 10 (3,679 US gallons).

Series 20 milestones

 * First flight: September 18, 1968.
 * FAA certification: November 25, 1968.
 * First delivery: December 11, 1968 to SAS
 * Entry into service: January 27, 1969 with SAS.
 * Last delivery: May 1, 1969 to SAS.

Series 30


The -30 was the definitive series, produced to counter Boeing's 737 twinjet, with 662 produced, accounting for about 60% of production. The -30 entered service with Eastern Airlines in February 1967 with a 3 ft (0.9 m) and full-span leading edge slats, improving takeoff and landing performance. Gross take-off weight was typically 110,000 lb (50,000 kg). Engine options for Models -31, -32, -33 and -34 included the P&W JT8D-7 and JT8D-9 rated at 14,500 lbf (64 kN) of thrust, or JT8D-11 rated at 15,000 lbf (67 kN) of thrust.

The Series 30 was designed to incorporate extremely effective leading edge devices in order to reduce the landing approach speeds exhibited by the Series 10, at substantially higher maximum landing weights. The addition of full-span leading edge slats reduced approach speeds by 6 knots, despite the gross weight being 5000 lbs greater. The full span slats offered a significant weight advantage over slotted Kreuger flaps, since the wing leading edge structure associated with the slat is a more efficient torque box than the structure associated with the slotted Kreuger. The wing also had a 6% increase in wing chord, all ahead of the front spar. This increase in wing chord allowed the 15% chord slat to be incorporated.

Series 30 subvariants
{C The Series 30 was produced in four main sub-variants.


 * DC-9-31: Produced in passenger version only. The first DC-9 Series 30 flew on August 1, 1966, and the first delivery was made to Eastern Airlines on February 27, 1967 following certification on December 19, 1966. Basic MTOW of 98,000 lb (44,000 kg) and subsequently certificated at various increased weights up to 108,000 lb (49,000 kg).


 * DC-9-32: Introduced in the first year of production (1967). Certificated March 1, 1967. Basic MTOW of 108,000 lb (49,000 kg) and subsequently increased to 110,000 lb (50,000 kg). A number of cargo versions of the Series 32 were also produced including:
 * 32LWF (Light Weight Freight) with modified cabin but no cargo door or reinforced floor, intended for package freighter use.
 * 32CF (Convertible Freighter), with a reinforced floor but retaining passenger facilities
 * 32AF (All Freight), a windowless all-cargo aircraft.


 * DC-9-33: Following the Series 31 and 32 came the Series 33, intended for passenger/cargo or all-cargo use. Certificated on April 15, 1968, the aircraft's MTOW was increased to 114,000 lb (52,000 kg), MLW to 102,000 lb (46,000 kg) and MZFW to 95,500 lb (43,300 kg). JT8D-9 or -11 (15,000 lbf (67 kN) thrust) thrust) engines were used. In addition, the wing incidence was increased 1.25 degrees, to reduce cruise drag. Only 22 were built, as All Freight (AF), Convertible Freight (CF) and Rapid Change (RC) aircraft.


 * DC-9-34: The last version of the aircraft to be developed was the Series 34, intended for use on longer range routes with an MTOW of 121,000 lb (55,000 kg), an MLW of 110,000 lb (50,000 kg) and an MZFW of 98,000 lb (44,000 kg). The DC-9-34CF (Convertible Freighter) was certificated April 20, 1976, while the passenger followed on November 3, 1976. The aircraft is equipped with the more powerful JT8D-9s with the -15 and -17 engines as an option. It also included the wing incidence change introduced on the DC-9-33. Twelve were built, five as convertible freighters.

Series 30 features
The DC-9-30 was offered with a selection of variants of JT8D including the -1, -7, -9, -11, -15 and -17. The most common on the Series 31 is the JT8D-7 (14,000 lbf (64 kN) thrust) was standard, with the -11 also offered. The Series 33 was offered with the JT8D-9 or -11 (15,000 lbf (67 kN) thrust) engines and the heavyweight -34 with the JT8D-9, -15 (15,000 lbf (67 kN) thrust) or -17 (16,000 lbf (71 kN) thrust) engines.

Series 40
This further lengthened version entered service with SAS in March 1968. With a 6 ft 6 in (2 m) longer fuselage, accommodation was up to 125 passengers. The -40 was fitted with Pratt & Whitney engines of between 14,500 and 16,000 lbf (64 and 71 kN). A total of 71 were produced.

Series 50
The -50 was the largest DC-9 to fly. It features an 8 ft 2 in (2.49 m) fuselage stretch and seats up to 139 passengers. It started revenue service in August 1975 with Eastern Airlines and included a number of detail improvements, a new cabin interior, and more powerful JT8D-15 or -17 engines in the 16,000 and 16,500 lbf (71 and 73 kN) class. McDonnell Douglas delivered 96, all as Model -51. Some visual cues to distinguish this version from other DC-9 variants include side strakes (fins) below the side cockpit windows and thrust reversers rotated about 22 degrees on the original configuration. However various maintenance replacements have seen the thrust reversers in the same position as the -30 and -40.



Military and government


C-9: Several -30 series with side cargo door were purchased by the US armed forces. The C-9A Nightingale medical evacuation configuration was for the U.S Air Force. The C-9B Skytrain II was for the U.S Navy and Marines, used for fleet logistics support moving both personnel and light cargo. The VC-9C is a VIP transport version for the US Air Force, used to transport Cabinet members and other high-ranking officials.

Versions of the DC-9 are also used by the Kuwait Air Force.

Operators


A total of 129 DC-9 aircraft (all variants) were in commercial service as of November 2011, including Delta Air Lines (25), Aserca Airlines (17), USA Jet Airlines (7), Everts Air Cargo (5), Aeronaves TSM (4), Astral Aviation Cargo (4), LASER Airlines (4), and other operators with fewer aircraft.

Delta Air Lines has, since acquiring Northwest Airlines, operated a fleet of DC-9 aircraft, most of which are over 30 years old. With severe increases in fuel prices in the summer of 2008, Northwest Airlines finally began retiring its DC-9s, switching to Airbus A319s that are 27% more fuel efficient.

Because of the usage of the aging JT8D engines, as of late 2000s DC-9s are considered gas guzzlers when compared to other more recent airliner designs. Studies aimed at improving DC-9 fuel efficiency, by means of retrofitted wingtip extensions of various types, have not succeeded in demonstrating significant benefits.

With the existing DC-9 fleet shrinking, modifications do not appear to be likely to occur, especially since the wing design makes retrofitting difficult. Thus, DC-9s are likely to be further replaced in service by new Boeing 737, Airbus A320, Embraer E-Jets aircraft, or the new, emerging Bombardier CSeries airliner. However, it is probable that a modest number of DC-9s will continue to productively fly for many years to come. As the Northwest/Delta merger progresses, Delta has pulled several stored DC-9s back into service.

One ex-SAS DC-9-21 is operated as a skydiving jump platform at Perris Valley Airport in Perris, California. With the steps on the ventral stairs removed, it is the only airline transport class jet certified to date by the FAA for skydiving operations as of 2008.

Accidents and incidents
As of March 2009, the DC-9 has been involved in 117 incidents, including 101 hull-loss accidents, with 2,135 fatalities.

Notable accidents

 * On October 1, 1966, West Coast Airlines Flight 956 crashed with eighteen fatalities and no survivors. This accident marks the first loss of a DC-9.
 * On March 9, 1967, TWA Flight 553 fell to earth in a field in Concord Township, near Urbana, Ohio, following a mid-air collision with a Beechcraft Baron, an accident which triggered substantial changes in air traffic control procedures.
 * On March 17, 1969, Viasa Flight 742 crashed into the La Trinidad neighborhood of Maracaibo during a failed take-off. All 84 people on board the aircraft as well as 71 people on the ground were killed. At that time Viasa Flight 742 was the worst disaster in aviation history.
 * On June 27, 1969, Douglas DC-9-31 N906H of Hawaiian Airlines collided on the ground with Vickers Viscount N7410 of Aloha Airlines at Honolulu International Airport. The Viscount was damaged beyond repair.
 * On September 9, 1969, Allegheny Airlines Flight 853, a DC-9-30, collided in mid-air with a Piper PA-28 Cherokee near Fairland, Indiana. The DC-9 carried 78 passengers and 4 crew members, the Piper one pilot. The occupants of both aircraft were killed in the accident and the aircraft were destroyed.
 * On February 15, 1970, a Dominicana de Aviación DC-9 crashed after taking off from Santo Domingo. The crash, possibly caused by contaminated fuel, killed all 102 passengers and crew, including champion boxer Teo Cruz.
 * On May 2, 1970, an Overseas National Airways DC-9, wet-leased to ALM Dutch Antilles Airlines and operating as ALM Flight 980, ditched in the Caribbean Sea on a flight from New York's John F. Kennedy International Airport to Princess Juliana International Airport on Sint Maarten. After three landing attempts in poor weather at Sint Maarten, the pilots began to divert to their alternate of Saint Croix, U.S. Virgin Islands but ran out of fuel 30 mi (48 km) short of the island. After about 10 minutes, the aircraft sank in 5,000 ft (1524 m) of water and was never recovered. 40 people survived the ditching, 23 perished.
 * On November 14, 1970, Southern Airways Flight 932, a DC-9, crashed into a hill near Tri-State Airport in Huntington, West Virginia. All 75 on board were killed (including 37 members of the Marshall University Thundering Herd football team, eight members of the coaching staff, 25 boosters, and others).
 * On January 26, 1972, Jugoslovenski Aero Transport Flight 367, DC-9-32 registration YU-AHT, was destroyed in flight by a bomb placed on-board the aircraft. The sole survivor was a flight attendant, Vesna Vulović, who holds the record for the world's longest fall without a parachute when she fell some 33,000 ft (10,000 m) inside the tail section of the airplane and survived.
 * On December 20, 1972, North Central Airlines Flight 575, DC-9-31 registration N954N, collided during its takeoff roll with Delta Air Lines Flight 954, a Convair CV-880 that was taxiing across the same runway at O'Hare International Airport in Chicago, Illinois. The DC-9 was destroyed, killing 10 and injuring 15 of the 45 people on board; two people among the 93 aboard the Convair 880 suffered minor injuries.
 * On July 31, 1973, Delta Air Lines Flight 723, DC-9-31 registration N975NE, crashed into a seawall at Logan International Airport in Boston, Massachusetts, killing all 83 passengers and 6 crew members on board. One of the passengers initially survived the accident but later died in a hospital.
 * On September 11, 1974, Eastern Air Lines Flight 212, a DC-9-30 crashed just short of the runway at Charlotte, North Carolina, killing 71 out of the 82 occupants.
 * On 30 October 1975, an Inex-Adria Aviopromet DC-9-32 hit high ground during an approach in fog near Prague-Suchdol, Czechoslovakia. 75 people were killed.
 * On September 10, 1976, an Inex-Adria Aviopromet DC-9 collided with a British Airways Trident over the Croatian town of Vrbovec, killing all 176 people aboard both aircraft.
 * On April 4, 1977, Southern Airways Flight 242, a DC-9-31, crash landed onto then a highway in New Hope, Georgia, US. The crash and fire resulted in the death of both flight crew and 61 passengers. Nine people on the ground also died. Both flight attendants and 20 passengers survived.
 * On June 26, 1978, Air Canada Flight 189, a DC-9 overran the runway in Toronto after a blown tire aborted the takeoff. Two of the 107 passengers and crew were killed.
 * On September 14, 1979, Aero Trasporti Italiani Flight 12, a DC-9-32 crashed in the mountains near Cagliari, Italy while approaching Cagliari-Elmas Airport. All 27 passengers and 4 crew members died in the crash and ensuing fire.
 * On June 27, 1980, Aerolinee Itavia Flight 870, a DC-9-15 suffered an in-flight explosion and crashed into the sea near the Italian island of Ustica. All 81 people on board were killed. The causes of this accident are still unclear.
 * On June 2, 1983, Air Canada Flight 797, a DC-9 experienced an electrical fire in the aft lavatory during flight, resulting in an emergency landing at Cincinnati/Northern Kentucky International Airport. During evacuation, the sudden influx of oxygen caused a flash fire throughout the cabin, resulting in the deaths of 23 of the 41 passengers, including Canadian folk singer Stan Rogers. All five crew members survived.
 * On August 31, 1986, Aeroméxico Flight 498]] collided in mid-air with a Piper Cherokee over the city of Cerritos, California, then crashed into the city, killing all 67 aboard the aircraft, 15 people on the ground, and all 3 in the small plane.
 * On 4 April 1987, Garuda Indonesia Flight 035, a DC-9-32, hit a pylon and crashed on approach to Polonia International Airport in bad weather with 24 fatalities.
 * On December 3, 1990, Northwest Airlines Flight 1482, a DC-9-14, went on the wrong taxiway in dense fog at Detroit-Metropolitan Wayne County Airport, Michigan (DTW). It entered the active runway instead of taxiway instructed by air traffic controllers. It collided with a departing Northwest Boeing 727. Nine people were killed.
 * On July 2, 1994, USAir Flight 1016 crashed in Charlotte, North Carolina while performing a go-around because of heavy storms and wind shear at the approach of runway 18R. There were 37 fatalities and 15 injured among the passengers and crew. Although the airplane came to rest in a residential area with the tail section striking a house, there were no fatalities or injuries on the ground.
 * On May 11, 1996 ValuJet Flight 592 crashed in the Florida Everglades due to a fire caused by the activation of chemical oxygen generators illegally stored in the hold. The fire damaged the plane's electrical system and eventually overcame the crew, resulting in the deaths of 110 people.
 * On October 10, 1997, Austral Flight 2553, DC-9-32 registration LV-WEG, en route from Posadas to Buenos Aires, crashed near Fray Bentos, Uruguay, killing 74 people (69 passengers and 5 crew).
 * On February 2, 1998, Cebu Pacific Flight 387 crashed on the slopes of Mount Sumagaya in Misamis Oriental, Philippines, killing all 104 people on board. Aviation investigators deemed the incident to be caused by pilot error when the plane made a non-regular stopover to Tacloban.
 * On November 9, 1999, TAESA Flight 725 crashed a few minutes after leaving the Uruapan Airport en-route to Mexico City. 18 people were killed in the accident.
 * On October 6, 2000, Aeroméxico Flight 250 en route from Mexico City to Reynosa, Mexico, could not stop before the runway ended and it crashed into houses and fell into a small canal, killing four people from the houses. None of 83 passengers and 5 crew members were killed, though four people on the ground were. The runway had seen heavy rainfall as a result of Hurricane Keith.
 * On April 15, 2008, a Hewa Bora Airways DC-9 crashed into a residential neighborhood, in the Goma, Democratic Republic of the Congo, resulting in the deaths of at least 44 people.
 * On July 6, 2008, USA Jet Flight 199, a DC-9-15F, after taking off from Shreveport, LA airport bound for Saltillo, Mexico crashed and burned. The captain was killed and first officer was seriously injured. The cause of the crash is under investigation.

Specifications

 * Cabin cross section:
 * External width: 10 ft 11.6 in (3.34 m)
 * Internal width: 10 ft 3.7 in (3.14 m)
 * External height: 11 ft 8 in (3.6 m)
 * Internal height: 6 ft 9 in (2.06 m)

Sources: McDonnell Douglas DC-9 data.