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The McDonnell Douglas MD-11 is a three-engine medium- to long-range widebody jet airliner, manufactured by McDonnell Douglas and, later, by Boeing Commercial Airplanes. Based on the DC-10, it features a stretched fuselage, increased wingspan with winglets, refined airfoils on the wing and smaller tailplane, new engines and increased use of composite materials. Two of its engines are mounted on underwing pylons and a third engine at the base of the vertical stabilizer. It also features an all-digital glass cockpit that decreases the flight deck crew from the three required on the DC-10 to two by eliminating the necessity for a flight engineer.

MD-11
KLM MD-11 departing Amsterdam Airport Schiphol
Role	Wide-body jet airliner
National origin	United States
Manufacturer	McDonnell Douglas/Boeing
First flight	January 10, 1990
Introduction	December 1990 with Finnair
Status	In service
Primary users	FedEx Express UPS Airlines World Airways Lufthansa Cargo
Produced	1988–2000
Number built	200
Developed from	McDonnell Douglas DC-10

Development

Origins

Although the MD-11 program was launched in 1986, McDonnell Douglas started to search for a DC-10 derivative as early as 1976. Two versions were considered then, a DC-10-10 with a fuselage stretch of 40 feet (12 m) and a DC-10-30 stretched by 30 feet (9.1 m). That later version would have been capable of transporting up to 340 passengers in a multi-class configuration, or 277 passengers and their luggage over 5,300 nautical miles (9,800 km). At the same time, the manufacturer was searching to reduce wing and engine drag on the trijet. Another version of the aircraft was also envisaged, the "DC-10 global", aimed to counter the risks of loss of orders for the DC-10-30 that the Boeing 747SP and its range were creating. The DC-10 global would have incorporated more fuel tanks.

 

Flight deck

 

While continuing its research for a new aircraft, McDonnell Douglas designated the whole program as the DC-10 Super 60, having previously been known for a short time as DC-10 Super 50. The Super 60 was to be an intercontinental aircraft incorporating many aerodynamic improvements on the wings, and a fuselage lengthened by 26 feet 8 inches (8.13 m) to allow up to 350 passengers to seat in a mixed class layout, compared to the capacity of 275 in the same configuration of the DC-10.

Following more refinements, the DC-10 Super 60 project was proposed, as of 1979, in three distinct versions like the DC-8. The DC-10-61 aimed to be a medium-range aircraft, able to carry 390 passengers (mixed class) or 550 passengers (all-economy) on an airframe lengthened by 40 feet (12 m), similar to the Boeing's later 777-300 and Airbus A340-600. Like for the DC-8, the series 62 was proposed as a long-range aircraft stretched by 26 ft 7 in (8.10 m) and capable to carry up to 350 passengers (mixed class) or 440 passengers (all-economy), similar to the later Boeing 777-200 or the Airbus A330-300/A340-300/500. And finally, the series 63 would have incorporated the same fuselage as the DC-10-61 as well as all the aerodynamic refinements of the -62. After the three accidents in the 1970s (Turkish Airlines Flight 981, American Airlines Flight 191, and Air New Zealand Flight 901) which received great media coverage, the trijet program was seriously damaged by doubts regarding its structural integrity. For these reasons, and due to another downturn in the airline industry, all work on the Super 60 was stopped.

In 1981, a Continental DC-10-10 (registration number N68048) was leased to conduct more research, particularly the effects the then newly-designed winglets could have on aircraft performance. Different types of winglets were tested during that time in conjunction with NASA. McDonnell Douglas was again planning new DC-10 versions that could incorporate winglets and more efficient engines developed at the time by Pratt & Whitney (PW2037) and Rolls-Royce (RB.211-535F4). The manufacturer finally rationalized all these studies under the MD-EEE (Ecology-Economy-Efficiency) designation, that was later modified to MD-100 following some more changes. The MD-100 was proposed in two versions: the Series 10, having an airframe shorter by 6 ft 6 in (1.98 m) compared to the DC-10 and seating up to 270 passengers in a mixed class configuration; and the Series 20, incorporating a fuselage stretch of 20 ft 6 in (6.25 m) over the DC-10 and able to seat up to 333 passengers in the same kind of configuration as the Series 10. Both versions could be powered by the same engine families as the actual MD-11 plus the RB.211-600. But the situation for the manufacturer, and the airline industry in general, did not look bright. No new DC-10 orders were received, and many among the observers and customers doubted that the manufacturer would be around for much longer. Thus, the Board of Directors decided in November 1983 to cease once more all work on the projected new trijet.

EVA Air Cargo MD-11F

 

The following year was fruitful as airlines placed repeat orders for the MD-80 series jets that had helped the manufacturer through the past difficult years. No new orders for the DC-10 were received, which inspired McDonnell Douglas even more to create a replacement. However, the production line was nonetheless kept active thanks to an earlier orders from the U.S. Air Force for 60 KC-10A tankers. McDonnell Douglas was still convinced that a new derivative for the DC-10 was needed, as shown by the second-hand market of its Series 30 as well as for the heavier DC-10-30ER version. Thus, in 1984 a new derivative aircraft version of the DC-10 was designated MD-11 for the first time. From the very beginning, the MD-11X was conceived in two different versions. The MD-11X-10, based on a DC-10-30 airframe, offered a range of 6,500 nautical miles (12,000 km) with passengers. That first version would have had a Maximum Take-Off Weight (MTOW) of 580,000 pounds (260,000 kg) and would have used CF6-C2 or PW4000 engines. The MD-11X-20 was to have a longer fuselage, accommodating up to 331 passengers in a mixed class layout, and a range of 6,000 nautical miles (11,000 km).

As more orders for the DC-10 were received, McDonnell Douglas used the time gained before the end of DC-10 production to consult with potential customers and to refine the proposed new trijet. In July 1985, the Board of Directors finally authorized the Long Beach plant to offer the MD-11 to potential customers. At the time, the aircraft was still proposed in two versions, both with the same fuselage length, a stretch of 22 ft 3 in (6.78 m) over the DC-10 airframe, as well as the same engine choice as the MD-11X. One version would have a range of 4,780 nautical miles (8,850 km) with a gross weight of 500,000 pounds (230,000 kg) and transport up to 337 passengers, while the second would carry 331 passengers over 6,900 nautical miles (12,800 km). A year later, as several airlines had committed for the MD-11, the situation was looking optimistic. The aircraft was now a 320 seater baseline and defined as an 18 ft 7 in (5.66 m) stretch over the DC-10-30 powered by the new advanced turbofans offered by the major engine manufacturers and giving it a range of 6,800 nautical miles (12,600 km). Other versions, such as a shortened ER with a range of 7,500 nautical miles (13,900 km), an all cargo offering a maximum payload of 200,970 pounds (91,160 kg) and a Combi with a provision for ten freight pallets on the main deck, were proposed. Further growth of the aircraft was also foreseen, such as the MD-11 Advanced.

Design phase

A MD-11 (left) and DC-10 comparison

 

Finally, the MD-11 was launched on December 30, 1986 with commitments for 52 firm orders and 40 options in three different versions (passenger, combi and freighter) from ten airlines (Alitalia, British Caledonian, Dragonair, FedEx Express, Finnair, Korean Air, Scandinavian Airlines System, Swissair, Thai Airways International, and VARIG) and two leasing companies (Guinness Peat Aviation and Mitsui). Orders from Dragonair, Scandinavian and UTA, an undisclosed customer, were canceled by 1988. Assembly of the first MD-11 began on March 9, 1988, and the mating of the fuselage with wings occurred in October that year. First flight was originally planned to occur in March 1989, but numerous problems with the manufacturing, delays with suppliers producing essential components and labor industrial actions delayed the ceremonial roll out of the prototype until September of that year. The following months were used to prepare the prototype for its maiden flight, which finally happened on January 10, 1990. The first two aircraft manufactured were intended for FedEx and thus, were already fitted with the forward side cargo door. They remained with the manufacturer as test aircraft until 1991 before being completely converted to freighters and delivered to their customer. FAA certification was achieved on November 8, 1990 while the European Joint Aviation Authorities (JAA) certified the MD-11 on October 17, 1991 after approximately 200 separate issues were resolved.

Yugoslav Airlines, which was already flying several DC-10s, was to become the first customer of the MD-11. Three aircraft were manufactured but were never delivered due to war in Yugoslavia. The first MD-11 was delivered to Finnair on December 7, 1990 and it accomplished the first revenue service by an MD-11 on December 20, 1990, carrying passengers from Helsinki to Tenerife in the Canary Islands. MD-11 service in the U.S. was inaugurated by Delta Air Lines, also in 1990. It was during this period that flaws in the MD-11's performance became apparent. It failed to meet its targets for range and fuel burn. American Airlines in particular was unimpressed, as was Singapore Airlines, which canceled its order for 20 aircraft. American Airlines cited problems with the performance of the airframe and the Pratt & Whitney PW4000 engines as reasons of the cancellation while the Singapore Airlines stated that the MD-11 could not operate on the airline's long haul routes. Pre-flight estimates indicated that the P&W-powered MD-11 was to have a 7,000 nautical miles (13,000 km) range with 61,000 pounds (28,000 kg) of payload. With the Phase 1 drag reduction in place then, the aircraft could only achieve its full range with 48,500 pounds (22,000 kg) of payload, or a reduced range of 6,493 nautical miles (12,025 km) with a full payload.

Finnair MD-11 decorated with Moomin characters.

 

In 1990, McDonnell Douglas, along with Pratt & Whitney and General Electric began a modification program known as the Performance Improvement Program (PIP) to improve the aircraft's weight, fuel capacity, engine performance, and aerodynamics. McDonnell Douglas worked with NASA's Langley Research Center to study aerodynamic improvements. The PIP lasted until 1995 and recovered the range for the aircraft. However, by this point sales of the MD-11 had already been significantly impacted. The MD-11 was one of the first commercial designs to employ a computer-assisted pitch stability augmentation system that featured a fuel ballast tank in the tailplane, and a partly computer-driven horizontal stabilizer. Updates to the software package made the plane's handling characteristics in manual flight similar to the DC-10, despite a smaller tailplane to reduce drag and increase fuel efficiency.

Schematic of the McDonnell Douglas MD-11, side, top, front, cross-section views.

 

After McDonnell Douglas merged with Boeing in 1997 the new company decided that MD-11 production would continue, though only for the freighter variant. However, in 1998 Boeing announced it would end MD-11 production after filling current orders. The last passenger MD-11 built was delivered to Sabena in April 1998. Assembly of the last two MD-11s were completed in August and October 2000; they were delivered to Lufthansa Cargo on February 22, and January 25, 2001 respectively. Production ended because of lack of sales, resulting from internal competition from comparable aircraft, such as the Boeing 777 and Boeing 767-400 and external competition from the Airbus A330/A340. The trijet design of the MD-11 made it inherently less fuel efficient than similar-sized twin-engine jets.

McDonnell Douglas and later Boeing performed studies on the feasibility of removing the tail engine and making it a two engine plane, but nothing came of it. McDonnell Douglas originally projected that they would sell more than 300 MD-11 aircraft, but only 200 planes were built. The MD-11 was assembled at McDonnell Douglas's Douglas Products Division in Long Beach, California (later Boeing's facility).

Design

Engine#2 mounted at the base of the vertical stabilizer.

 

The MD-11 is a medium to long-range widebody airliner, with two engines mounted on underwing pylons and a third engine at the base of the vertical stabilizer. It is based on the DC-10, but featuring a stretched fuselage, increased wingspan with winglets, refined aerofoils on the wing and tailplane, new engines and increased use of composites. The winglets are credited with improving fuel efficiency by about 2.5%. The MD-11 has a smaller empennage than the DC-10 it is based upon.

The MD-11 features a two-crew cockpit that incorporates six interchangeable CRT-units and advanced Honeywell VIA 2000 computers. The cockpit design is called Advanced Common Flightdeck (ACF) and is shared with the Boeing 717. Flight deck features include an Electronic Instrument System, a dual Flight Management System, a Central Fault Display System, and Global Positioning System. Category IIIb automatic landing capability for bad-weather operations and Future Air Navigation Systems are available.

The MD-11 incorporates hydraulic fuses not included in the initial DC-10 design, to prevent catastrophic loss of control in event of a hydraulic failure.

Variants

The MD-11 was manufactured in five variants.

• MD-11 (131 built): the Passenger variant, sometimes referred to as MD-11P, was produced from 1988 to 1998. It was the first version on offer at launch of the aircraft in 1986, and was delivered to American Airlines (19), Delta Air Lines (17), Swissair (16), Japan Airlines (10); KLM (10), and other airlines with fewer aircraft.
• MD-11C (5 built): the Combi was the third variant on offer at launch in 1986 and was designed to accommodate both passengers and freight on the main deck, which featured a rear cargo compartment for up to ten pallets, each measuring 88 by 125 inches (2.2 m × 3.2 m) or 96 by 125 inches (2.4 m × 3.2 m). The main deck cargo compartment was accessible by a large rear port side cargo door, which measured 160 by 102 inches (4.1 m × 2.6 m). The main deck cargo volume was 10,904 cubic feet (308.8 m³). Additional freight was also carried in below-deck compartments. The MD-11C could also be configured as an all passenger aircraft. All five aircraft were manufactured between 1991 and 1992 and delivered to Alitalia, the only customer for that variant. In 2005 and 2006 the airline converted them to full-freighter configurations to be operated by Alitalia's cargo division. Following that division's closure, the five aircraft were returned to their lessor in January 2009.
• MD-11CF (6 built): the Convertible Freighter variant was launched in 1991 by an order from Martinair for 3 aircraft plus two options. The MD-11CF feature a large forward port side cargo door (140 by 102 inches (3.6 m × 2.6 m)) located between the first two passenger doors, and can be used in an all passenger- or in an all cargo-configuration. As a freighter, it can transport twenty six pallets of the same dimensions (88 by 125 inches (2.2 m × 3.2 m)) or 96 by 125 inches (2.4 m × 3.2 m)) as for the MD-11C and MD-11F for a main deck cargo volume of 14,508 cubic feet (410.8 m³) and offers a maximum payload of 196,928 pounds (89,325 kg). All six MD-11CFs were delivered to Martinair (4) and World Airways (2) during 1995. The two World Airways aircraft have been converted to freighter-only in 2002.

Interior of a MD-11 in service with Finnair in 2008

 

• MD-11ER (5 built): the Extended Range version was launched by the manufacturer at the Singapore Air Show in February 1994. The MD-11ER incorporates all the Performance Improvement Program (PIP) options, including a Maximum Take-Off Weight of 630,500 pounds (286,000 kg) and an extra fuel tank of 3,000 US gallons (11,000 l)) in the forward cargo hold to offer a range of 7,240 nautical miles (13,410 km), an increase of 400 nautical miles (740 km) over the standard passenger variant. MD-11ERs were delivered between 1995 and 1997 to Garuda Indonesia (3) and World Airways (2). As of February 2007, only one Finnair MD-11ER has been converted to MD-11 with the removal of the extra fuel tank.
• MD-11F (53 built): the Freight transport aircraft was the second variant on offer at launch in 1986 and was the last and longest (1988–2000) manufactured version. The all-cargo aircraft features the same forward port side cargo door (140 by 102 inches (3.6 m × 2.6 m)) as the MD-11CF, a main deck volume of 15,530 cubic feet (440 m³), a maximum payload of 200,151 pounds (90,787 kg) and can transport 26 pallets of the same dimensions (88 by 125 inches (2.2 m × 3.2 m) or 96 by 125 inches (2.4 m × 3.2 m)) as for the MD-11C and MD-11CF. The MD-11F was delivered between 1991 and 2001 to FedEx Express (22), Lufthansa Cargo (14), and other airlines with fewer aircraft.

A MD-11BCF of Aeroflot Cargo

• MD-11 Boeing Converted Freighter (BCF) - Boeing and its group of international affiliates offer a conversion of used passenger airliners into freighters. The MD-11BCF is one of the models offered.

Note: Some or all the features of the MD-11ER, including the higher MTOW of 630,500 lb (286,000 kg), part or all of the PIPs aerodynamic improvements packages and composite panels were fitted to later built MD-11s (except the extra fuel tank), and could be retrofitted to any of the variants, except for the PIP Phase IIIB larger aft engine intake. Some airlines, such as Finnair, Martinair and FedEx have made the structural changes required to allow their aircraft to have the higher MTOW. Swissair's 16 newly delivered aircraft were retrofitted with all the features except for the extra fuel tank and were so-designated MD-11AH for Advanced Heavy.

Undeveloped variants

After ending the MD-12 program, McDonnell Douglas focused on 300-400–seat MD-11 derivatives. At the 1996 Farnborough International Air Show, the company presented plans for a new trijet with high-seating and long-range named "MD-XX". It was offered in the MD-XX Stretch and MD-XX LR versions. The MD-XX Stretch version was to have a longer fuselage than the MD-11 and seat 375 in a typical 3-class arrangement. The MD-XX LR was to have a longer range and be the same length as the MD-11; it was to have typical 3-class seating for 309. However, the MDC board of directors decided to end the MD-XX program in October 1996, because the financial investment was too large for the company.

Operators

In July 2011, 181 MD-11 aircraft (all variants) were in commercial service, with FedEx Express (63), UPS Airlines (38), Lufthansa Cargo (18), World Airways (16), KLM Royal Dutch Airlines (10), EVA Air (8), and other operators with fewer aircraft of the type.

Most of the airlines who ordered the MD-11 for their long-haul passenger flights had replaced it with Airbus A330, A340 and Boeing 777 aircraft by the end of 2004. Some carriers converted their MD-11s to freighters such as China Eastern Airlines and Korean Air. Korean Air announced as early as December 1994 its intention to convert its five passenger MD-11s to freighters for medium-range cargo routes. In 1995 American Airlines agreed to sell its 19 aircraft to FedEx, with the first MD-11 being transferred in 1996. Japan Airlines (JAL) announced the replacement of its 10 MD-11s in 2000; these aircraft were being converted into freighters and sold to UPS.

In February 2007 TAM Linhas Aéreas began operating the first of three leased MD-11s in intercontinental service following a 2006 order for four 777-300ERs to be delivered in 2008. In May 2007, Finnair announced the sale of their last two MD-11s to Aeroflot-Cargo to become part of the Russian airline cargo fleet in 2008 and 2009. Varig retired the MD-11 from its fleet in June 2007 after sixteen years of services.

Two MD-11s were also operated in a VIP configuration, one by Saudia Royal Flight for members of the Royal family, and one by Mid East Jet for ASACO Aviation, both are now stored.

Safety issues

The MD-11 has had problems with its flight control systems, problems that have resulted in multiple accidents and incidents since the aircraft's introduction. The initial design of the slat/flap lever in the cockpit was conducive to accidental dislodgement by crew in flight. The defect has been corrected since 1992. In the early 2000s, Boeing improved the flight control software at the urging of the FAA to reduce the possibility of violent unintentional pitch movements.

In an effort to improve fuel efficiency, McDonnell Douglas designed the MD-11’s center of gravity to be much further aft than other commercial aircraft. This significantly reduces the margin for error during the takeoff and landing phases. A number of operators have introduced special training to assist crews in safely handling the MD-11's critical phases of flight.

Specifications

Deliveries

Source

http://en.wikipedia.org/wiki/MD-11