Lockheed L-1011 TriStar
The Lockheed L-1011 TriStar is an American medium-to-long-range, wide-body trijet airliner built by the Lockheed Corporation. It was the third wide-body airliner to enter commercial operations, after the Boeing 747 and the McDonnell Douglas DC-10. The airliner has a seating capacity of up to 400 passengers and a range of over. Its trijet configuration has three Rolls-Royce RB.211 engines with one engine under each wing, and a third engine center-mounted in the rear fuselage with an S-duct air inlet on the top of the fuselage. The aircraft has an autoland capability, an automated descent control system, and available lower deck galley and lounge facilities.
The L-1011 TriStar was produced in two fuselage lengths. The original L-1011-1 first flew in November 1970 and entered service with Eastern Air Lines in 1972. The shortened, longer range L-1011-500 first flew in 1978 and entered service with British Airways a year later. The original-length TriStar was also produced as the high gross weight L-1011-100, the up-rated engine L-1011-200, and the further upgraded L-1011-250. Post-production conversions for the L-1011-1 with increased takeoff weights included the L-1011-50 and L-1011-150.
The L-1011 TriStar's sales were hampered by two years of delays due to developmental and financial problems at Rolls-Royce, the sole manufacturer of the aircraft's engines. Between 1968 and 1984, Lockheed manufactured a total of 250 TriStars, assembled at the Lockheed plant located at the Palmdale Regional Airport in southern California north of Los Angeles. After L-1011 production ended, Lockheed withdrew from the commercial aircraft business due to its below-target sales. As of 2025, only one L-1011 is in service, as Stargazer.
Development
Origins
In the 1960s, American Airlines approached Lockheed and competitor Douglas with the need for an airliner that could carry 250 passengers on transcontinental routes. Lockheed had not produced civilian airliners since 1961 with the L-188 Electra. In the 1950s the Electra was designed for turboprop propulsion, which Lockheed successfully used on the C-130 Hercules military transport. Even after the Electra overcame vibration problems that caused several crashes early in its career, the market for large airliners would soon shift over to jet airliners such as the Boeing 707 and Douglas DC-8. Lockheed won contracts for jet military transports with the C-141 StarLifter, and pioneered very large jet transports with the large C-5 Galaxy with its high-bypass turbofan engines. Boeing lost the military contract, but its private-venture 747 would later capture a much larger civilian airliner market for wide-body airliners.Having experienced difficulties with some of its military programs, Lockheed was eager to re-enter the civilian market with a smaller wide-body jet, and its response was the L-1011 TriStar. Douglas Aircraft answered American Airlines with the DC-10, which had a similar three-engine configuration and dimensions. Despite their similarities, the L-1011 and DC-10's engineering approach differed greatly. McDonnell, who had recently taken over Douglas Aircraft, directed DC-10 development on a "very firm budget, and cost overruns were unacceptable even at the expense of safety", and the conservative approach meant reusing Douglas DC-8 technology. By contrast, Lockheed would "take the most advanced technology of the day and when that technology was lacking, Lockheed created it" for the L-1011 to give it lower noise emissions, improved reliability, and higher efficiency over first-generation jet airliners. The TriStar name was selected in a Lockheed employee naming contest for the airliner. The advanced technology that went into the TriStar resulted in a high purchase price.
The TriStar's design featured a twin-aisle interior with a maximum of 400 passengers and a three-engine layout. The TriStar was originally conceived as a "jumbo twin", but a three-engine design was ultimately chosen to give the aircraft enough thrust to take off from existing runways. Also, before the establishment of Extended Operations standards by the FAA in the 1980s, commercial jets with only two engines were not allowed to fly more than 60 minutes away from an airport, making trans-oceanic flights impossible. The main visible difference between the TriStar and its similar trijet competitor, the McDonnell Douglas DC-10, is the center engine position: the DC-10's engine is mounted above the fuselage for simplicity of design and more economical construction, while the TriStar's engine is installed in the rear fuselage with air entering through an S-duct for reduced drag and improved stability. Lockheed was able to keep the pressure loss in the S-duct similar to that in a straight duct by limiting the duct curvature. Incorporating the S-duct made the airframe lighter than with a straight duct installation. The research undertaken during the design of the L-1011 indicated that losses of using an S-duct were more than compensated for by the above savings. A further major difference between the L-1011 and the DC-10 was Lockheed's selection of the Rolls-Royce RB.211 as the only engine option for the L-1011. As originally designed, the RB.211 turbofan was an advanced three-spool design with a carbon fiber fan, which would have better efficiency and power-to-weight ratio than any competing engine like the General Electric CF6 that powered the DC-10. In theory, the triple spool would produce the same or more power as existing double spool engines while having a smaller cross section that would reduce drag.
American Airlines opted for the Douglas DC-10, although it showed considerable interest in the L-1011. American intended to convince Douglas to lower its price for the DC-10, which it did. Without the support of American, the TriStar was launched on orders from TWA and Eastern Air Lines.
Although the TriStar's design schedule closely followed that of its competitor, McDonnell Douglas beat Lockheed to market by a year due to delays in powerplant development. In February 1971, after massive development costs associated with the RB.211, Rolls-Royce went into receivership. This halted L-1011 final assembly and Lockheed investigated the possibility of a US engine supplier. However the engineering was finalized at that stage in the TriStar's development and its S-duct, which was designed to fit the smaller cross-section of the triple spool RB-211 engine that would have reduced drag, was too small in diameter to accommodate an existing double spool engine. One option presented was potential outsource of RB-211 production to Canadian manufacturer Orenda Engines.
The British government agreed to approve a large state subsidy to restart Rolls-Royce operations on condition that the U.S. government guarantee the bank loans Lockheed needed to complete the L-1011 project. Despite some opposition, not least from the then Governor of California, Ronald Reagan, the U.S. government provided these guarantees. For the rest of the RB.211 project, Rolls-Royce remained a government-owned company.
Production
The TriStar's internal Lockheed model number is L-093. The TriStar was manufactured in Lockheed facilities in Burbank and Palmdale, California. The prototype L-1011 first flew on November 16, 1970. The L-1011 was certified on April 14, 1972, with the first airliner delivered to Eastern Air Lines on April 26, 1972. In 1972, its unit cost was US$20 million. To further publicize the new aircraft, an L-1011, possibly the prototype, was taken on a world tour during 1972 by famed Lockheed test pilot Tony LeVier. In a demonstration by test pilots LeVier and Charles Hall, 115 crew members, employees, and reporters embarked on the TriStar for a 4-hour, 13-minute flight from Palmdale to Dulles Airport "with the TriStar's AFCS feature engaged from takeoff roll to landing", and Lockheed touted it as "a groundbreaking moment: the first cross-country flight without the need for human hands on the controls".Lockheed discovered fairly early on that the TriStar suffered from higher than estimated structural weight, engine weight, and specific fuel consumption. To rectify this problem and to meet performance guarantees, Lockheed developed a structural kit that allowed maximum takeoff weight to be increased on production aircraft from. However, the weight problems affected the weight and desirability of early production L-1011-1 aircraft, known as Group 1.
Group 1 aircraft have an Operating empty weight of, about higher than later aircraft, while Group 2 aircraft have an OEW of, some lower. These aircraft, in general, also have different center of gravity envelopes with the forward center of gravity limit on the early aircraft being more restrictive at higher gross weights. Groups 1 and 2 aircraft are upgradeable only to -50 or -150 specifications, although the Group 1 aircraft still maintain their operating disadvantages. All L-1011-1 aircraft from serial number 1052 onwards are Group 3 aircraft and are fully upgradeable to all variants up to -250 specification.
Costs at Rolls-Royce were controlled and its efforts largely went into the original TriStar engines, which needed considerable modifications between the L-1011's first flight and service entry. The competition, notably General Electric, was very quick to develop its CF6 engine with more thrust, which meant that a heavier "intercontinental" DC-10-30 could be more quickly brought to market. The flexibility afforded to potential customers by a long-range DC-10 put the L-1011 at a serious disadvantage. Rolls-Royce went on to develop the high-thrust RB.211-524 for the L-1011-200 and -500, but this took many years.
The resultant delay in Lockheed and Rolls-Royce offering a high gross variant with a longer range, coupled with the TriStar's delayed introduction, meant that only 250 TriStars were sold compared to over 400 DC-10s. Lockheed needed to sell 500 airliners to break even, but in 1981, the company announced production would end with the delivery of the 250th and last L-1011 on order in 1984.
The TriStar's failure to achieve profitability caused Lockheed to withdraw from the civilian aircraft business. The TriStar's rivalry with the DC-10 has been seen as a "case study in what can happen when two manufacturers attempt to split a market that simply could not support both aircraft". Lockheed lacked the resources to follow up with several proposals based on the TriStar wing and airframe, including a wide-body twinjet and a stretched quad-jet. McDonnell Douglas was also financially weakened and could only develop the MD-11, a refinement of the DC-10, instead of an all-new design to challenge the next generation of twinjets like the Boeing 777.
Ultimately, both the L-1011 and the DC-10/MD-11 were doomed by this next generation of widebody twinjets such as the Boeing 777 and the Airbus A330 - as the rules on ETOPS gradually extended to longer distance routes - thanks largely to the improving reliability and performance of jet engines which made trijet aircraft less cost efficient to operate; widebody twinjets become the dominant configuration for long haul operations.