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By
Wikipedia,
The McDonnell Douglas DC-10 is a three-engine medium- to long-range widebody airliner, with two engines mounted on underwing pylons and a third engine at the base of the vertical stabilizer. The model was a successor to the company's DC-8 for long-range operations, and competed in the same markets as the Airbus A300, Boeing 747, and Lockheed L-1011 Tristar, which has a similar layout to the DC-10. Production of the DC-10 ended in 1989 with 386 delivered to airlines and 60 to the U.S. Air Force as air-to-air refueling tankers, designated the KC-10 Extender. The DC-10 was succeeded by the related McDonnell Douglas MD-11 which entered service in 1990. DevelopmentFollowing an unsuccessful proposal for the US Air Force's CX-HLS (Heavy Logistics System) in 1965, Douglas Aircraft began design studies based on its CX-HLS design. In 1966, American Airlines offered a specification to manufacturers for a widebody aircraft smaller than the Boeing 747 but capable of flying similar long-range routes from airports with shorter runways. The DC-10 became McDonnell Douglas's first commercial airliner after the merger between McDonnell Aircraft Corporation and Douglas Aircraft Company in 1967. The DC-10 first flew on 29 August 1970 and entered commercial service with launch customer American Airlines on 5 August 1971 on a round trip flight between Los Angeles and Chicago, nearly a year before the Lockheed L-1011 Tristar (which was built to a similar specification). The similarity to the L-1011 in terms of passenger capacity and launch in the same time frame resulted in a head to head sales competition which affected profitability of the aircraft. The launch customers for the DC-10 were American Airlines and United Airlines with orders for 25 and 60 respectively of the Series 10 model. Eventually, the DC-10 was able to distinguish itself from its competitors with a second engine supplier, which has the possible effect of controlling costs due to competition, as well as earlier introduction of longer range variants than the L-1011.
The first DC-10 version was the "domestic" series 10 with a range of 3,800 miles (6,112 km). The series 20 (only ordered by Northwest Orient and Japan Airlines) had a typical load range of 5,750 mi (9,265 km) or a maximum payload range of 4,673 mi (7,520 km). The series 30 had a typical load range of 6,220 mi (10,010 km) or a maximum payload range of 4,604 mi (7,410 km). The series 20 was powered by Pratt & Whitney JT9D engines, whereas the series 10 and 30 engines were General Electric CF6. Before delivery of its aircraft, Northwest's president asked that the "series 20" aircraft be redesignated "series 40" because he argued that the aircraft was much improved over the original design. The FAA issued the Series 40 certificate on 27 October 1972. One of the main visible differences between the models is that the series 10 has three sets of landing gear (one front and two main) while the series 30 and 40 have four gear (one front, three main). The center main two-wheel landing gear (which extends from the center of the fuselage) was added to accommodate the extra weight by distributing the weight and providing additional braking. The 446th and final DC-10 rolled off the production line in December 1988 and was delivered to Nigeria Airways in July 1989. The DC-10 was assembled at McDonnell Douglas's Douglas Products Division in Long Beach, California. Even as the final few DC-10 deliveries were occurring, McDonnell Douglas had already started production of the DC-10's successor, the MD-11. Although superficially similar, the MD-11 was longer and featured a two-crew flight deck, updated avionics, and other improvements. However, the MD-11 was not as successful as the DC-10, owing to airlines keeping their first generation widebodies in service longer, increased competition from Airbus and Boeing, and the MD-11's initial failure to meet promised performance specifications. Design
The DC-10 is a low-wing cantilever monoplane with a conventional tail unit with a single fin and rudder. It is powered by two turbofan engines mounted on underwing pylons and a third engine at the base of the vertical stabilizer. It has a retractable tricycle landing gear. The later series 30 and 40 have an additional two-wheel main landing gear. It was designed to be a medium to long-range airliner with a widebody fuselage to seat over 250 passengers. It is operated by a flight-crew of three located on the flightdeck in the nose on the same level as the passenger cabin. The fuselage has underfloor stowage for cargo and baggage. Service issuesDespite its troubled beginnings in the 1970s, which gave it an unfavorable reputation, the DC-10 ultimately proved a reliable aircraft, much loved by engineers and pilots. The original DC-10-10's notorious safety record continuously improved as design flaws were rectified and fleet hours increased. In fact, the DC-10's lifetime safety record at 2003 is comparable to similar second-generation passenger jets. Increased inspections and modifications made the DC-10 among the safest aircraft for passenger travel. Cargo doorsThe DC-10 was designed with cargo doors that opened outward instead of inward-opening "plug-type" doors. Using outward-opening doors allowed the cargo area to be completely filled, as an inward-opening door would need to swing into the cargo area, rendering that space unusable. To secure the door against the outward force caused by the pressurization of the fuselage, outward-opening doors rely on a heavy locking mechanism. In the event of a complete door lock malfunction, there was potential for explosive decompression. This was discovered in 1972 following an incident aboard American Airlines Flight 96, but no mandatory repair order was issued until the Turkish Airlines Flight 981 crash in 1974. The cargo door on all DC-10s then underwent a redesign that added an extra lock safety device to the system. Hydraulic systemOther initial design problems included its lack of locking flap mechanisms designed to maintain their position in the event of a hydraulic failure. The lines from all three independent and redundant hydraulic systems were located in close proximity, directly beneath the tail engine. Later DC-10s and the MD-11 incorporated hydraulic fuses to prevent such catastrophic loss of control in event of a hydraulic rupture. Engine pylonsAlthough the design of the engine pylons was adequate, it was not designed to facilitate easy maintenance; the original procedure for an engine change was to detach the engine from the pylon first, which was tedious and time-consuming due to tight tolerances. To save time and costs, American and Continental Airlines both started to use a faster procedure, instructing their mechanics to remove the engine with pylon as one unit using forklift trucks. McDonnell-Douglas advised against this procedure. This procedure was very difficult to execute successfully and led to damage that was the principal cause of the crash of American Airlines Flight 191. In November 1979, the FAA fined American Airlines $500,000 for using this faulty maintenance procedure. Continental Airlines was fined $100,000 on a similar charge. Insulation blanketsAn acoustic/thermal insulation material known as metallized polyethylene terephthalate or metallized Mylar was used on some DC-10s. In the investigation of the crash of Swissair flight 111, Mylar was found to be flammable. In an Airworthiness Directive in November 2000, the FAA ordered this insulation to be removed by June 2005. (The FAA estimated a cost of $991,010 per airplane.) The high cost of complying with the Airworthiness Directive was a factor for some airlines to prematurely withdraw the airplane from passenger service. Variants
The DC-10 was manufactured in a number of different variants:
Incidents and accidentsAs of August 2008, the DC-10 was involved in 55 incidents, including 30 hull-loss accidents, with 1,261 fatalities. Cargo door problemThe outward-opening cargo door design problem was first identified on 12 June 1972, when American Airlines Flight 96 lost its aft cargo door after takeoff from Detroit, Michigan, but the crew, led by captain Bryce McCormick, was able to perform an emergency landing with no further incident, despite being unable to use most of the aircraft's control surfaces - the first use of engine differential thrust to save a DC-10, but not the last. Before Flight 96 took off, an airport employee had forced the door shut, weakening the locking pin and causing the door to blow out as the plane reached altitude.
Although many carriers voluntarily modified the cargo doors and re-trained their ground crews, there was not yet a mandatory redesign of the system. Severe design problems still persisted with the aircraft's cargo doors, and two years after the American Airlines incident, an almost identical cargo door blow-out caused Turkish Airlines Flight 981 to crash into a forest near the town of Ermenonville shortly after leaving Orly Airport in Paris on 3 March 1974. 346 people were killed in one of the deadliest air crashes of the twentieth century, recorded in Aviation History books as the "Ermenonville air disaster". The circumstances surrounding this crash were similar to those surrounding the previous accident; however, a modified seating configuration on the Turkish aircraft exacerbated the effects of decompression which caused the floor of the aircraft to collapse into the cargo bay. As part of the DC-10 design, vents were not present to allow the pressure between the cargo and passenger compartments to equalize. Control cables running through the floor of the plane were severed when the floor collapsed and this rendered the aircraft uncontrollable. In the aftermath of this crash, all DC-10s underwent a mandatory door redesign. American Airlines Flight 191In 1979, with the cargo door issues resolved, DC-10s (all series) around the world were grounded following the crash of American Airlines Flight 191. Flight 191 lost its number one wing engine after taking off from O'Hare International Airport in Chicago, USA, 25 May 1979. As the engine separated upwards, it ripped through the leading edge of the wing, rupturing hydraulic lines which caused a hydraulic cylinder that locked the port wing slats to fail. As airspeed was reduced per AA emergency climb-out procedures, the slats retracted, the left wing stalled, the plane rolled left and crashed before the flight crew could recover. All 271 people on board, plus two on the ground, were killed in this accident; the worst single plane crash in America. The United States National Transportation Safety Board (NTSB) officials discovered that a maintenance procedure was the culprit: American Airlines mechanics had removed the engine and its pylon together, rather than removing the engine from the pylon then the pylon from the wing, as recommended by McDonnell Douglas. This was done using a forklift and the pylon was inadvertently cracked in the process. The short-cut procedure, thought to save several man hours on maintenance, was used by three major airlines, although McDonnell Douglas advised against it. Although McDonnell Douglas was not directly at fault for the pylon separation, it redesigned the DC-10 to allow more redundancies in the hydraulic systems. The Chicago incident also highlighted a major deficiency in the DC-10 design—its lack of a locking mechanism to maintain the position of the leading-edge slats in the event of a hydraulic or pneumatic failure. Other wide-body aircraft of the day carried such a feature, but it was omitted from the DC-10. Another deficiency highlighted in the NTSB report was the vulnerable placement of wiring at the leading edge (front) of the wing. When the engine pulled up and over the wing, it tore out these wires, thus rendering vital warning instruments in the cockpit inoperable. Other aircraft of this era typically placed this kind of wiring in the center of the wing, in a less vulnerable position. In addition, the captain's stick-shaker - a stall-warning device - was powered by the left engine, and was therefore inoperative, so there was no warning that the plane was stalling. American Airlines had chosen a configuration in which only the captain's controls had a stick-shaker, and, as the first officer was the one flying the plane, a working stick-shaker might not have saved the aircraft. Following the Chicago crash, the type certificate of the DC-10 was withdrawn by the FAA, grounding the aircraft, on 6 June 1979. The aircraft resumed service after modifications which prevented the slats retracting in the event of a hydraulic leak. United Airlines Flight 232Another instance of a DC-10 crash was the Flight 232 disaster at Sioux City, Iowa, USA, on 19 July 1989. After the #2 engine (tail engine) suffered an uncontained fan disk failure in flight which ruptured critical hydraulic lines, the crew, led by Captain Al Haynes and assisted by a senior pilot flying as a passenger (Dennis E. "Denny" Fitch), performed an emergency landing by varying remaining engine power to control the plane. Although the aircraft was destroyed with the loss of many lives, the crew flew the aircraft onto the runway in a partially controlled manner and 185 of the 296 people on board survived. The Sioux City crash concerned investigators because the total loss of hydraulic pressure aboard the DC-10 was considered nearly impossible. The design had lines from all three independent and redundant hydraulic systems in close proximity, directly beneath the #2 (tail) engine. Debris from the #2 fan disk separation failure penetrated all three lines resulting in total loss of control to the elevators, ailerons and rudder. Other notable accidents and incidentsOther than the American Airlines, Turkish Airlines and United Airlines crashes well covered by the media and mentioned above, many other DC-10s were lost in different types of accidents. Other notable incidents involved DC-10s.
The Air France Concorde crash of 2000 was attributed to a fragment of titanium that fell from the thrust reverser of a Continental Airlines DC-10 that had taken off some four minutes earlier. This fragment was traced to a third party parts replacement which had not been approved by the FAA. Sources: [1] and Jet Airliner Production List Operators
On 8 January 2007, Northwest Airlines retired its last remaining DC-10 being used for scheduled passenger service, replacing it with an Airbus A330 for a route between Minneapolis-St. Paul and Honolulu, thus ending the aircraft operations with all major airlines. Regarding the retirement of Northwest's DC-10 fleet, Wade Blaufuss, spokesman for the Northwest chapter of the Air Line Pilots Association said, "The DC-10 is a reliable airplane, fun to fly, roomy and quiet, kind of like flying an old Cadillac Fleetwood. We're sad to see an old friend go." "The DC-10 is going to be remembered as a better cargo plane than passenger plane," said Richard Aboulafia, an analyst at the Teal Group. In November 2006, ATA Airlines announced it had purchased seven of Northwest's remaining DC-10s, to replace ATA's L-1011 airplanes. Omni Air International purchased six of Northwest's DC-10 aircraft. The aging models are now largely being used as dedicated freight aircraft. American Airlines and United Airlines have sold their large DC-10-10 fleets to cargo carrier FedEx. Many have been modernized to MD-10s by adding a glass cockpit, which eliminates the need for a flight engineer. Other DC-10 aircraft continue in charter and cargo services with their three-person flight deck configuration. Omni Air International and World Airways, continue to operate the DC-10 on charter passenger services as well as for the Air Mobility Command. Biman Bangladesh Airlines operates five DC-10-30s as one of their primary passenger aircraft as of 2009. Non-airline operators include The Royal Netherlands Air Force with three DC-10-30CFs converted to KDC-10 flying tankers, the USAF with its 59 KC-10, the 10 Tanker Air Carrier with its modified DC-10-10 used for fighting wildfires, and Orbis International, which uses a single DC-10-10 converted into a flying eye hospital. As of July 2008, there were 158 DC-10s in service with commercial operators, including FedEx Express (85), Omni Air International (12), Arrow Air (8), World Airways (6), Centurion Air Cargo (5), Biman Bangladesh Airlines (4), Avient Aviation (4) and others with fewer aircraft. SpecificationsDeliveriesSee alsoRelated development Comparable aircraft External links
Text from Wikipedia is available under the Creative Commons Attribution/Share-Alike License; additional terms may apply.
Published in July 2009. Click here to read more articles related to aviation and space!
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