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L-1011 Tristar

Development of the Lockheed L-1011 Tristar began in 1966 when American Airlines announced a need for a short to medium-range, large-capacity transport. In March of 1968, production began when Lockheed received orders for their design from TWA and Eastern Airlines. Although Production was slowed when Rolls- Royce, the developer of the L1011's engines, was forced to declare bankruptcy, Lockheed managed to deliver the Tristar for operation with Eastern and TWA in 1972. The longer-range L1011-200 came in 1977 and the L1011-250, which featured larger fuel-capacity, started operations with Delta Airlines in 1986. The original version of inter-continental L1011-500 was delivered to British Airways in 1979 and the next year Pan Am put the extended wing version into service.

The L-1011 did not succeed in the market. Though the program went through development and production, Lockheed constructed only 252 of these airliners, rolling out the last in 1983. The program did not earn back its development costs; in fact, this firm sold few if any at a profit, for this company faced strong competition first from the DC-10 and later from the Boeing 767 and Airbus A-300. Hence to win further sales, Lockheed had to offer prices that were very low. The program had received over $1.7 billion at the time of the near-collapse of Rolls; the final losses, at the time of program cancellation, came to $2.5 billion. With this, Lockheed retired from the ranks of the commercial planebuilders and proceeded to make its living entirely as a military contractor.

The Lockheed L-1011 and the McDonnell Douglas DC-10 are wide-body transports in a weight class between that of the 707 and the very heavy 747. Both aircraft are powered by three high-bypass-ratio turbofan engines located in a new configuration arrangement; one engine is mounted under each wing, and the third engine is mounted at the rear of the aircraft. The L-1011 and the DC-10 were initially designed to an airline requirement for a high-capacity transport with transcontinental range, but growth versions of each are presently available with intercontinental capability. Initial flights of' both aircraft occurred in 1970. An early version of the DC-10 entered airline operation in 1971, and the L-1011 began service in 1972. Both aircraft are in wide Use throughout the world.

The L-1011 features two engines in underwing nacelles and one engine mounted on top of the fuselage forward of the swept fin, with the jet efflux below the rudder through the tail cone. The circular wide-body fuselage has low-set wings at the midway point. The swept tailplane is low set on either side of the rear fuselage below the fin. Refuelling pods are under the wings.

The three-engine configuration employed on the aircraft, in which two of the engines are located near the aircraft center of gravity, offers ail advantage in aircraft balance over an arrangement in which all three engines are mounted at the rear of the fuselage (Boeing 727, for example). Placement of two of the engines under the wing also allows the horizontal tall to be mounted in the highly desirable low position, as contrasted with the T-tall arrangement. The large lateral distance between the wing-mounted engines, however, causes larger yawing moments following loss of' power of one of these engines as compared with a similar power loss in the rear-mounted engine arrangement.

The method of mounting the rear engine is seen to be quite different on the L- 1011 and the DC-10. The L-1011 utilizes a mounting arrangement similar to that of the Boeing 727. The center engine is mounted in the aft end of the fuselage and is connected through an S-shaped duct to the large inlet mounted on top of the fuselage. In contrast, the center engine of the DC-10, including inlet and exhaust nozzle, is integrated with the fin above the fuselage. The engine efficiency resulting from this straight inlet-engine-nozzle configuration, as compared with the S-shaped duct arrangement, was thought to more than offset the structural complexity (and probable weight increase) of integrating the engine with the fin. The high performance of both aircraft, however, suggests that either method of engine installation can be made to operate successfully.

The Lockheed L-1011-200 is powered with three Rolls-Royce RB.211-524 engines of 48 000 pounds thrust each. The McDonnell Douglas DC-10-30 is powered by three General Electric CF6-50CI engines of 52 500 pounds thrust each but is also available with a version of the Pratt & Whitney JT9D engines.

The main landing gear of the L-1011 has two struts to which are attached four-wheel bogies. The aerodynamic design of the jet transport is conventional. The wings have about 35 of sweepback with aspect ratios in the range of 7.0 to 7.5 and feature transonic airfoils of advanced design. The wings have double-slotted trailing edge flaps and leading-edge slats. Lateral control is provided by a combination of ailerons and spoilers. The spoilers are also used to control lift and drag when deployed symmetrically. Longitudinal control of the L-1011 is provided by a variable incidence stabilizer to which the elevator is mechanically linked. The maximum lift-drag ratio of the aircraft is estimated to lie in the range between 17.0 and 17.5.

The original Tristar , with a fuselage length of 54.17m (177ft 8.5in) and up to 400 seats, was the L1011-1, with a gross weight of 195,045kg (430,000lb). This was followed in 1974 by the L1011-200 with RB.211-524 engines rated at 213.6kN-222.4kN (48,000-50,000lb) and maximum take-off weight of up to 216,363kb (477,000lb) depending on fuel capacity. With the same higher operating weights and increased fuel capacities but the lower-rated 22B engines the aircraft was designated L1011-100. The first flight of a Tristar with 524 engines was made on 12 August 1976. In 1976 Lockheed launched the L1011-500, which combined higher weights and enlarged fuel capacity with a shorter fuselage to achieve very long ranges. Advanced aerodynamic features were also introduced in the L1011-500, including active controls, resulting in a 2.74m (9ft) increase in wing span and a reduction in tail plane area.. The first L1011-500 flew in October 1978, with 222.4kN (50,000lb) 524B engines but without the extended wingtips, which were first flown in November 1979. The designation L1011-250 applies to conversions of the L1011-1 to have the same 524B4 engines as used in the L1011-500, allowing maximum take-off weight to be increased to 224,985kg (496,000lb). Fuel capacity is also increased. Conversion of six L1011-1s to 250 standard for Delta Airlines began in 1986. Other L1011-1 conversions included the L1011-50, increasing maximum weight from 195,047kg (430,000lb) to 204,119kg (450,000lb), and the L1011-150, with a 10% increase in range.

At a gross weight of 468,000 pounds and with a maximum payload of 74,200 pounds, the L-1011-200 is capable of flying for a distance of 4,884 miles. With a maximum fuel load and a reduced payload of 42,827 pounds, the range is 6,204 miles. The aircraft is capable of carrying 400 economy-class passengers in a 10-abreast double-aisle configuration. An interesting feature of the interior design of the L-1011 is the location of the galleys below the passenger deck; food service is provided to the passenger cabin by means of elevators.

The economical cruising speed of the L-1011 is 567 miles per hour at 31 000 feet, which corresponds to a Mach number of 0.84. The takeoff field length of 8070 feet is relatively short compared with 10,370 feet for the DC-10-30 and 10 450 feet for the 747. The values of gross weight, payload weight, and range of the DC-10-30 are significantly larger than the corresponding values for the L-1011-200. A comparison of the values of the wing loading and thrust loading of the two aircraft clearly shows why the takeoff distance of the DC-10-30 is greater than that of the L-1011 - 200. The cost-economical cruising speeds of the two aircraft are comparable.

Pegasus is a winged small launcher, airdropped from a modified Orbital Sciences Corporation L-1011 Tristar aircraft. It can carry payloads weighing 850-1,050 lbs to LEO of 100 nautical miles. Pegasus, available in two models, has flown eight missions since 1990, with two failures of its XL version.

The RAF operates a number of Tristar aircraft in the transport role. The Tristar C2s are dedicated transport aircraft and can carry 265 passengers and 16 tonnes (35,000 lbs) of freight over ranges in excess of 4,000 miles. The other two variants, the K1 and the KC1, are dual role and capable of providing air-to-air refuelling from a pair of centerline fuselage hoses. The K1 can carry 204 passengers; however, the KC1 has a large freight door and can carry 20 cargo pallets, 196 passengers or a combination of mixed freight and passengers. The VC10 and Tristar fleets are based at RAF Brize Norton in Oxfordshire.



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