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McDonnell Douglas MD-80 / MD-90
The MD-80 series was derived from the DC-9 and it was introduced commercially in October 1980 by Swissair. The MD-80 series was followed in modified form by the MD-90 in 1989 and the MD-95/Boeing 717 in 1998. BackgroundDouglas Aircraft developed the DC-9 in the 1960s as a short-range companion to their larger DC-8. The DC-9 was an all-new design, using two rear fuselage-mounted turbofan engines, and a T-tail. The DC-9 has a narrow-body fuselage design with a 5-abreast seating, and holds 80 to 135 passengers depending on seating arrangement and aircraft version. The MD-80 series was the second generation of the DC-9. It was originally called the DC-9-80 series and the DC-9 Super 80 and entered service in 1980. The MD-80 series was then developed into the MD-90 entering service in 1995. The last variant of the family was the MD-95, which was renamed the Boeing 717-200 after McDonnell Douglas’s merger with Boeing in 1997. 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 3,000 produced, and the first place Boeing 737 with over 5,000 produced. MD-80 seriesThe MD-80 series is a mid-size, medium-range airliner that was introduced in 1980. The design was second generation of the DC-9 with two rear fuselage-mounted turbofan engines, small, highly efficient wings, and a T-tail. The aircraft has a distinctive 5-abreast seating in coach class. It was a lengthened DC-9-50 with a higher maximum take-off weight (MTOW) and the ability to carry more fuel. The airplane series was designed for frequent, short-haul flights for 130 to 172 passengers depending on plane version and seating arrangement.
The Series 80 featured a fuselage 14 feet 3 in (4,34 m) longer than the DC-9-50. The DC-9 wings were redesigned by adding sections at the wing root and tip for a 28% larger wing. The initial Series 80 first flew October 19, 1979. It entered service in 1980. Originally it was certified as a version of the DC-9, but was changed to MD-80 in July 1983, as a marketing move. New versions of the series were initially the MD-81/82/83 and the shortened MD-87, even though their formal certification was DC-9-81/82 etc. Only the MD-88 was given an "MD" certification, as was later the MD-90. The MD-80 versions have cockpit, avionics and aerodynamic upgrades along with the more powerful, efficient and quieter JT8D-200 series engines, which are a significant upgrade over the smaller JT8D-15, -17, -11, and -9 series. The MD-80 series aircraft also have longer fuselages than their earlier DC-9 counterparts, as well as longer range. The MD-80’s production ended in 1999. Notably, some customers American Airlines and Alitalia still, as of 2007, refer to the planes in fleet documentation as "Super 80" or "SP80". This model is still flown extensively by American Airlines and Delta Air Lines on domestic routes. Comparable airliners to the MD-80 series include the Boeing 737 (in particular, the 737-400 variant) and Airbus A320. The MD-80 series has been used by airlines around the world. Major customers include Aeroméxico, Allegiant Air, American Airlines, Austrian Airlines, Avianca, Belle Air,Delta Air Lines, Swissair, Alitalia, Spanair, Scandinavian Airlines System (SAS), Finnair, Iberia, Japan Air System (JAS), China Eastern Airlines, China Northern Airlines, Alaska Airlines, Korean Air, Austral Líneas Aéreas, and Viking Airlines. Many of the airlines have, however, started to retire the type in the 2000s. A number of variants were proposed that never saw production. One proposal was the MD-94X which was fitted with an unducted fan engine. The MD-81 was used as a testbed for unducted fan engines, such as the GE 36 and the Pratt and Whitney/Allison 578-DX. The MD-90 is a mid-size, medium-range airliner that was developed from the MD-80 series. It is a 5 feet longer, updated version of the MD-88 with a similar electronic flight instrument system (EFIS), (glass cockpit) and even more powerful, quieter and fuel efficient IAE V2500 engines. The MD-90 features seating for 153 to 172 passengers depending on seating arrangement.
MD-90 production ended in 2001 due to internal competition with Boeing’s own 737-800 after Boeing and McDonnell Douglas merged in 1997. The final 20 MD-90s were built under contract in China under the Trunkliner program.The MD-90 is the least successful member of the DC-9 family with 117 planes sold. The main competitors of the MD-90 included the Airbus A320 and the Boeing 737-800. MD-90 major customers include Delta Air Lines, Saudi Arabian Airlines and Japan Air System (JAS). Of special note is that Delta Air Lines had initially placed a large order for the MD-90 to replace some aging Boeing 727s. After the Boeing-McDonnell Douglas merger, Delta canceled their remaining MD-90 orders in favor of the Boeing 737-800. In December 2007, a total of 1,051 MD-80 and MD-90 aircraft (all variants) were in airline service, including American Airlines (301), Delta Air Lines (133), Alitalia (74), Scandinavian Airlines System (42), and Japan Airlines (39). In addition, 80 other operators fly smaller numbers of the types MD-95The MD-95 was developed to replace early DC-9 models, then approaching 30 years old. The project was a complete overhaul the original DC-9 and reinventing it for modern transport. The aircraft is slightly longer than the DC-9-30 and is powered by new Rolls-Royce BR715 engines. The MD-95 was renamed Boeing 717 after the McDonnell Douglas—Boeing merger in 1997. A total of 156 717-200 airplanes were produced from 1998 to 2006. Incidents and accidentsAs of May 2007, there were a total of 22 hull-loss occurrences involving MD-80s, with 966 fatalities. Also, the MD-90 was involved in one hull-loss occurrence, with one fatality. Notable incidents
Service issuesAlthough the MD-80 series and MD-90 have proven to be safe during service, Airworthiness Directives resulting from accident reports have added repair costs to address issues. Horizontal stabilizer JackscrewThe MD-80 series and MD-90 uses a single Jackscrew to actuate the horizontal stabilizer and is not fail-safe, as opposed to the redundant dual jackscrew design found on the DC-10 and MD-11.[19] As the crash of Alaska Airlines Flight 261 demonstrated, the failure of the jackscrew could jam the horizontal stabilizer, pushing the airplane into a non-recoverable dive. Due to criticality of this part for safe flight, it is imperative to ensure it is well lubricated to minimize wear on the screw thread. However this was not done on a routine basis due to the inherent nature of a T-tail design meant that it was impossible to service from the ground and a cherry picker was required to perform any inspection and lubrication. McDonnell-Douglas initially recommended an "end play" check interval of 7000 hours which was subsequently found to be grossly inadequate. Following the crash of Alaska 261, the acme nut and jackscrew recovered from the airplane were found to be completely wornand found to be the cause of the crash due to inadequate maintenance. The FAA subsequently ordered airlines to inspect and lubricate the jackscrew every 650 hours (the original Airworthiness Directive’s ordered an interval of 2000 hours which was found to be inadequate still). Insulation blanketsAn acoustic/thermal insulation material known as metallized polyethylene terephthalate or Mylar was used on MD-80s and MD-90 until 1996 which was subsequently found to be flammable in the investigation of the Swissair Flight 111 crash. The FAA ordered that said insulation be removed by June 2005. The cost of complying with the Airworthiness Directive (FAA estimates a cost of $545,919 per airplane) has caused some difficulty to airlines. Specifications
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The McDonnell Douglas MD-80 and MD-90 are twin-engine, medium-range, single-aisle commercial jet airplanes. The MD-80 aircraft was originally part of the DC-9 line when first delivered before being later renamed. The MD-80 series and MD-90 have seating capacity up to 172 passengers. They have a common cabin layout that seats 140 passengers on scheduled flights and 161 or 165 on low-cost or charter flights.
The development of MD-80 series began in the 1970s as a growth version of the DC-9 Series 50. Availability of new Pratt & Whitney JT8D higher bypass engines drove early studies including designs known as Series 55, Series 50 (Re-fanned Super Stretch), and Series 60. The design effort focused on the Series 55 in August 1977. With the projected entry into service in 1980, the design was marketed as the "DC-9 Series 80". Swissair launched the Series 80 in October 1977 with an order for 15 plus an option for five.
The MD-90 was launched in 1989, first flew in 1993 and entered service in 1995. The MD-90 came in two versions: -30 and -30ER. The -30 had a range of 2,400 miles (3,860 km). The -30ER had a higher gross weight and range up to 2,750 miles (4,426 km) with an auxiliary fuel tank. An even longer range version, the -50 was offered but was not ordered.