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Lockheed L-1011 TriStar
Lockheed L-1011 TriStar
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The Lockheed L-1011 TriStar (pronounced "El-ten-eleven")[1] 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 4,000 nautical miles (7,410 km; 4,600 mi). Its trijet configuration has three Rolls-Royce RB211 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.

Key Information

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.[2] As of 2025, only one L-1011 is in service, as Stargazer.

Development

[edit]

Origins

[edit]

In the 1960s, American Airlines approached Lockheed and competitor Douglas (later McDonnell Douglas) with the need for an airliner that could carry 250 passengers on transcontinental routes.[3] 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.[4][5][6] 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.[7] 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[8] 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.[citation needed] The advanced technology that went into the TriStar resulted in a high purchase price.[citation needed]

TWA Lockheed L-1011-1 Tristar twin-aisle cabin in 1972
Lockheed L-1011 TriStar front view showing 3-engine layout
The S-duct configuration with the air intake offset above the rear engine

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.[7] 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.[9][10] 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.[11] A further major difference between the L-1011 and the DC-10 was Lockheed's selection of the Rolls-Royce RB211 as the only engine option for the L-1011.[12][13] As originally designed, the RB211 turbofan was an advanced three-spool design with a carbon fiber fan,[14] 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.[8][9]

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.[15] Without the support of American, the TriStar was launched on orders from TWA and Eastern Air Lines.[citation needed]

Prototype L-1011 TriStar being prepared for its first flight test in 1970

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 RB211, Rolls-Royce went into receivership.[16][17] This halted L-1011 final assembly and Lockheed investigated the possibility of a US engine supplier.[18] 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.[9] One option presented was potential outsource of RB-211 production to Canadian manufacturer Orenda Engines.[19]

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.[Note 1] Despite some opposition, not least from the then Governor of California, Ronald Reagan, the U.S. government provided these guarantees.[21] For the rest of the RB211 project, Rolls-Royce remained a government-owned company.[22]

Production

[edit]
An L-1011-1 of Pacific Southwest Airlines at Lockheed's Palmdale plant

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.[23] The L-1011 was certified on April 14, 1972, with the first airliner delivered to Eastern Air Lines on April 26, 1972.[23] In 1972, its unit cost was US$20 million (~$113 million in 2024).[24] 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 [Automatic Flight Control System] 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".[3]

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 (MTOW) to be increased on production aircraft from 409,000 to 430,000 pounds (186,000 to 195,000 kg). However, the weight problems affected the weight and desirability of early production L-1011-1 aircraft, known as Group 1 (serial numbers 1002 through to 1012).[citation needed]

Group 1 aircraft have an Operating empty weight (OEW) of 252,700 pounds (114,600 kg), about 12,700 pounds (5,800 kg) higher than later aircraft, while Group 2 aircraft (serial numbers 1013 through 1051) have an OEW of 247,000 pounds (112,000 kg), some 4,700 pounds (2,100 kg) 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 (serial numbers 1002 to 1051) are upgradeable only to -50 or -150 specifications, although the Group 1 aircraft (up to serial number 1012) 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.

British Airways L-1011 TriStar in Landor livery in 1986

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 RB211-524 for the L-1011-200 and -500, but this took many years.[25]

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.[9] 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.[26][27]

The TriStar's failure to achieve profitability caused Lockheed to withdraw from the civilian aircraft business.[2] 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 (one of the quadjet proposals consisting of two underwing engines and two rear fuselage-mounted engines). 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.[8]

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.

Design

[edit]

Engines

[edit]

The RB211 and its features, despite the delays in its development, provided the L-1011 with then-unmatched fuel economy and noise levels.[28]: 23 

Reversers and nozzle

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The two parts of the bypass thrust reverser are shown in their operating positions. The black grid of turning vanes allows the air to escape in a forward direction and the usual rearward flow of air for forward thrust is stopped by the blocker doors visible inside the duct.

The RB211 has thrust reverse using the bypass air from the fan. Reverse is selected when the engine is at idle. An escape path for the air is opened up around the nacelle and blocker doors close off the duct just behind. The air passes through a grid of turning vanes which send the air in a forward direction for reverse thrust. Initially the RB211 design also had thrust reversal for the core exhaust. Aerodynamic interference with the flaps diminished the braking effect from the flaps, so the core flow reverser was deleted; in its place an 11-degree afterbody was incorporated, which improved the specific range by 1.5%. Further improvements led to a 15-degree afterbody, enabling the L-1011 "to beat its predicted specific air range at 0.85 Mach by between 3.5 and 5.5 percent, the exact figure depending on cruise weight."[28]: 26–27 

All-flying tail

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Instead of the trimmable horizontal stabilizer (THS) found on most jetliners of its time, the L-1011 incorporated an all-flying tail – a stabilator. The aft portion had a geared (anti-servo) elevator that was linked to and moved with the stabilator, changing the stabilator's camber and improving the overall control surface effectiveness. Lockheed's main drive away from a THS was "[eliminating] mis-trim and runaway trim problems that have contributed to a number of accidents in the past."[28]: 30–31 [29] The fact that the elevators are not moved directly led to the failure in recognizing the jamming (trailing edge up) of the left elevator aboard Delta Air Lines Flight 1080 in 1977.[30]

Fuel system

[edit]

The L-1011-1 has four wing tanks; each inboard tank feeds the respective wing engine, and the two outboard tanks feed the tail engine via a flow equalizer.[28]: 33  The additional center tank of the long-range variants, which is two halves, is located between the wing halves. Each center tank half acts as additional capacity to its adjacent inboard wing tank; filling it by way of ejector pumps. When the center tank is filled, it is used to crossfeed all three engines in flight (by way of the ejector pumps and crossfeed valves) until the center tank is empty and the remaining tanks are equalized.[31]

Coach cabin of a TWA L-1011 TriStar in 2–5–2 layout

Landing gear

[edit]

The nose landing gear had two attachment points forward and aft, allowing a short-enough tug to push or pull the plane from directly underneath, a feature to allow operations where there wasn't enough forward space at some airports, which was more common at the time.[28]: 34 

Electrical system and avionics

[edit]
The L-1011 TriStar's three-crew flight deck

The L-1011 was the first jetliner to have an integrated drive generator (IDG).[28]: 34 

The FMS on the L-1011, certified by the FAA in September 1977, offered many features that have since become common. The features were aimed at greatly reducing crew workload and improving fuel efficiency. Of those are a Mach/IAS cruise control, an automatic Rough Air Mode that detects turbulence and adjusts the engine power setting accordingly, and a descent mode that figures out the optimum location to start a descent by "back computing" from a preselected point, allowing "on-altitude and on-speed" arrival.[28]: 36–38 

The L-1011 also featured a highly advanced autopilot system and was the first widebody to receive FAA certification for Cat-IIIc autolanding, which approved the TriStar for completely blind landings performed by the aircraft's autopilot in zero-visibility weather.[32] The L-1011 used an inertial navigation system to navigate;[33][34] this included aligning the navigation system by entering current coordinates of longitude and latitude.[8]

It also had a unique direct lift control (DLC) system, which allowed for smooth approaches when landing, without having to use significant pitch changes while on the approach path.[35][36] DLC helps maintain the aircraft on the glideslope during final approach by automatically deploying spoiler panels on the wings. Thus, rather than maintaining the descent by adjusting pitch, DLC helps control the descent while maintaining a more consistent pitch angle, using four redundant hydraulic systems.

Other components and systems

[edit]

The APU, which was the Pratt and Whitney ST6L,[37] was capable of operating up to 30,000 feet; its two square-shaped inlet doors are situated on the bottom fuselage on the aircraft's centerline towards the rear of the plane.[28]: 28  Compared to the typical three-system of its era, the L-1011 had four independent 3,000-psi hydraulic systems.[28]: 29 

Part of the production process also used a unique autoclave system for bonding fuselage panels together; this made the L-1011 extremely resistant to corrosion.

Operational history

[edit]

Commercial

[edit]
An Eastern Air Lines L-1011 TriStar in St. Louis in 1972. This aircraft would become the first L-1011 and first wide-body hull-loss as Eastern Air Lines Flight 401.

TWA heralded the TriStar as one of the safest aircraft in the world in promotional literature in the 1980s when concern over the safety record of the McDonnell Douglas DC-10, flown by rival airlines, was at its peak.[23] The L-1011 has been involved in five fatal accidents, only one of which was due to a problem with the aircraft.[38]

Delta Air Lines was the type's largest customer.[39] Delta retired its TriStars in 2001 to replace them with the Boeing 767-400ER. Cathay Pacific eventually became the largest non-U.S. operator of the type by acquiring many of the Eastern Air Lines examples when Eastern went bankrupt, operating as many as 21 aircraft. Cathay Pacific retired its L-1011s in October 1996 and replaced the type with the Airbus A330-300. TWA retired its remaining L-1011s in September 1997.

To secure the Japanese market, Lockheed secretly bribed several members of the Japanese government to subsidize All Nippon Airways' purchase of L-1011s; this caused a significant scandal when the bribes were uncovered.[40][41] The discovered scale to what has become known as the Lockheed bribery scandal led to the arrest of Japanese Prime Minister Kakuei Tanaka, as well as several other officials.[42] Within Lockheed, board chairman Daniel Haughton and vice chairman and president Carl Kotchian resigned their posts on February 13, 1976.[43] Tanaka was eventually tried and found guilty of violating foreign exchange control laws but was not charged with bribery, a more serious criminal offense.[44][45] Crucially for Lockheed, the fallout from the scandal included the loss of a contract worth over $1 billion.[46]

The Soviet Union at that time lacked a widebody airliner. Development of its own Ilyushin Il-86 was delayed;[47][48] consequently, in the mid-1970s, the Soviets started negotiations to buy 30 TriStars and license-produce up to 100 a year.[49][50] The talks collapsed as US President Jimmy Carter made human rights an important consideration in US foreign policy.[51][52] The TriStar was also listed by the Coordinating Committee as embodying advanced technology forbidden for sale to potential enemies, which presented a serious obstacle to the export deal.

The last three airlines to operate the L-1011 in scheduled service were Brussels Airlines (codeshare with Hewa Bora Airways), Thai Sky Airlines, and Lloyd Aereo Boliviano, with final flights in August 2007, February 2008, and May 2008, respectively.[53] In later years the L-1011 has been used by smaller start-up carriers, particularly in Africa and Asia. These operators mainly do their business in the ad hoc charter and wet leasing businesses. ATA Airlines (formerly known as American Trans Air) fleet included over 19 TriStars, but operations dwindled to only three L-1011-500s before the company's shutdown in April 2008.

Military

[edit]

The TriStar has also been used as a military tanker and passenger/cargo aircraft. The British Royal Air Force had nine aircraft of four variants. The aircraft were six ex-British Airways and three Pan Am L-1011-500s.[54][55][56] All of the aircraft served with No. 216 Squadron, and were based at RAF Brize Norton. The TriStar was replaced in RAF service by the Airbus A330 MRTT under the Future Strategic Tanker Aircraft program.[57] 216 Squadron was officially disbanded on March 20, 2014, and flew its last sorties with the TriStar on March 24, 2014.[58]

Other

[edit]
Northrop Grumman's L-1011-100 "Stargazer" preparing for a flight, with the fuselage lifted to make the room for mounting Pegasus XL rocket

In the early 1990s, Orbital Sciences began to use a converted L-1011-100 named Stargazer to launch Pegasus rockets into orbit around Earth. This venture effectively rendered the small Scout rocket obsolete.[59][60] This aircraft was also used in support of the X-34 and X-43 programs. NASA performed aerodynamic research on Orbital Sciences' L-1011 in 1995.[61] In 2014, three L-1011s in the world were airworthy.[62] As of 2019, Stargazer is the only active L-1011.[63]

Variants

[edit]

The earlier versions of the L-1011, such as the -1, -100, and -150 can be distinguished from the later models by the design of the middle engine nacelles. The earlier version nacelle has a round intake, whereas the later models have a small vertical fin between the bottom of the middle engine intake and the top of the fuselage.

The two L-1011 aircraft delivered to Pacific Southwest Airlines were configured with internal airstair doors that led into an entry hall in what was normally the forward lower baggage hold. This was to allow operations from airfields that did not have terminal buildings with jet bridges. These two aircraft were later in service with Aeroperú and Worldways Canada.

L-1011-1

[edit]
A Thai Sky Airlines L-1011-1 at Hong Kong International Airport in 2005

The L-1011-1 (FAA certification L-1011-385-1) was the first production model of the L-1011, designed for short- and medium-range flights. This variant served as the basis for subsequent variants. This type was purchased by Air Canada, ANA, Cathay Pacific, Eastern, and other operators with regional trunk routes requiring a widebody aircraft. Pacific Southwest Airlines purchased two L-1011-1 models with lower deck seating.[64] This variant was also one of the few widebodies to have the option for a full-height built-in airstair.[23]

The L-1011-1 was first delivered to Eastern Air Lines on April 5, 1972. A total of 160 L-1011-1 TriStars were built before production ended in 1983, although the majority of these, 119 or 75% of the total, were completed during a four-year period from 1972 to 1975. Most sales of the L-1011-1 were to US operators, with just three airlines, Delta, Eastern, and TWA, taking delivery of 110 combined. A further two aircraft were placed with a fourth US airline, Pacific Southwest Airlines.[23]

L-1011-100

[edit]
Trans World Airlines L-1011-100 TriStar

The L-1011-100 (FAA certification L-1011-385-1-14) was the second production model of the L-1011 and first flew in 1975 and featured a new center fuel tank and higher gross weights that increased the aircraft's range by nearly 930 miles (1,500 km). Launch orders for the L-1011-100 were placed by Saudia and Cathay Pacific, for two each, in May 1974. Deliveries began in June 1975.

The variant was also purchased by several airlines with longer-range routes, such as TWA, Air Canada, and BEA (which merged with BOAC to form British Airways). The first two L-1011-100s (serial numbers 1110 and 1116) were delivered new to Saudia with the same fuel capacity as the L-1011-1 (FAA certification L-1011-385-1-14); these were later upgraded to L-1011-200 specification.

L-1011-50

[edit]

The L-1011-50 was an upgraded version of the L-1011-1 with an increase in maximum takeoff weight from 430,000 pounds (195,000 kg) to either 440,000 pounds (200,000 kg) or 450,000 pounds (204,000 kg). Fuel capacity was not increased. The -50 was available only as a conversion package for the L-1011-1 and was never built new.

L-1011-150

[edit]

The L-1011-150 was a development of the L-1011-1 with its maximum takeoff weight increased to 470,000 pounds (210,000 kg). It was available only as a conversion for the L-1011-1. The -150 involves the conversion of Group 1 and Group 2 L-1011-1 aircraft to an MTOW of 470,000 pounds (210,000 kg), an increase of 40,000 pounds (18,000 kg), about 10%, from the L-1011-1, giving the aircraft a slightly better range than the -50, but without the additional center-section fuel tank, less than the L-1011-100 aircraft. The first aircraft was converted by MBB at Lemwerder in Germany during the winter of 1988–89 and was subsequently handed over to Air Transat of Canada on May 11, 1989.

L-1011-200

[edit]
A Saudia L-1011-200 TriStar at London Heathrow Airport, 1985

The L-1011-200 (FAA certification L-1011-385-1-15), the third production model of the L-1011, was introduced in 1976. Although otherwise similar to the -100, the -200 uses Rolls-Royce RB.211-524B engines to improve its performance in hot and high-altitude conditions. Gulf Air used -200 models to replace its earlier-generation Vickers VC10 fleet.

Other than the engines, the basic TriStar -200 is identical to the -100, with center-section fuel, having a MTOW of 466,000 pounds (211,000 kg), and fuel capacity of 26,400 US gallons (100,000 L) as the -100. An increase of gross weight to 474,000 pounds (215,000 kg) is possible, with the heavier aircraft offered by Lockheed as -200I or -200(Improved). Saudi Arabian Airlines (Saudia) was a launch customer for the -200 series and operated a sizable fleet until 1998. A total of 24 L-1011-200 aircraft were built new, with the first delivered to Saudia on May 28, 1977. Like other TriStar improvements, a conversion program has also been offered.

L-1011-250

[edit]

The L-1011-250 was an upgrade developed for late-model L-1011-1 aircraft and all L-1011-100 and L-1011-200 aircraft. The more powerful engines, lengthened wing, active-load-control ailerons and other systems that had been developed for the L-1011-500 were adapted into the baseline model. The changes resulted in increases in maximum takeoff weight to 510,000 pounds (230,000 kg) and fuel capacity from 23,600 US gal (89,335 L) to 31,632 US gal (119,735 L). This variant also used the upgraded RB211-524B4I engine, which could be easily retrofitted to the existing RB211-524B powerplants of the L-1011-200, but it required a re-engining on the L-1011-1 and L-1011-100, which used the original RB211-22B. The conversion allowed the L-1011 to match the performance of the long-range McDonnell Douglas DC-10-30. Although it could be applied to all L-1011 models, the upgrade was only undertaken by Delta on six late-model L-1011-1 aircraft.

L-1011-500

[edit]
A TAP Air Portugal L-1011-500 in 1990

The L-1011-500 (FAA certification L-1011-385-3) was the last L-1011 variant to enter production. It was a longer-range variant first flight-tested in 1978. Its fuselage length was shortened by 14 feet (4.3 m) and MTOW increased to allow higher fuel loads.[citation needed] More powerful RB.211-524 engines, increased wingspan, active-load-control ailerons and other improved systems were features introduced by Lockheed to exploit newly available technologies in the late 1970s. The -500 variant was popular among international operators and formed a significant portion of the L-1011 fleet of Delta and British Airways. However, it entered service seven years after the similar DC-10-30 entered service.[citation needed]

A Luzair L-1011-500 Tri Star while on approach to Gatwick Airport.

The TriStar 500 first flew on October 16, 1978, with the first delivery to British Airways on April 27, 1979. It entered service with British Airways on May 7, 1979, flying between London and Abu Dhabi. The last L-1011 produced was a TriStar 500, operated by the Las Vegas Sands.[citation needed]

Dimensions

[edit]

The TriStar 500 has an overall length of 164 feet 2 inches (50.04 m) and wingspan increased to 164 feet 4 inches (50.09 m) (early TriStar versions originally had the TriStar 1 wing with a span of 155 feet 4 inches (47.35 m)).

Flying surfaces

[edit]

Lockheed developed some aerodynamic improvements for the TriStar 500 which included a modified wing-to-body fairing, a fillet below the central intake, extended wingtips, and "active ailerons" or active control system (ACS). The new fairing reduced drag, while the fillet reduced noise in the rear cabin. The wingtip extensions increased aspect ratio, thus reducing induced drag, but resulted in increased bending. The ACS developed to solve this, provided gust alleviation, improving ride during flight, reduced fuel burn, and increased fatigue life.

Earlier TriStar 500s were delivered with the standard wing; these were later retrofitted with ailerons and extended wingtips. Pan Am was the first customer to order the -500 with the extended wingtips and active ailerons. Aircraft serial number 1176, the first for Pan Am, was the first TriStar 500 to be fitted with them as standard.

Powerplant

[edit]
An Air Lanka L-1011-500 TriStar ferrying an extra engine.

The TriStar 500 is equipped with higher thrust RB211-524B engines. Initially rated at 50,000 lbf (220 kN) thrust each, the higher-thrust 53,000 lbf (240 kN) -524B4 Improved (also referred to as the -524B4I) later became available, which also had improved fuel efficiency.

Performance

[edit]

Originally certified with an MTOW of 496,000 pounds (225,000 kg), an increased MTOW of 504,000 pounds (229,000 kg) was later certified in 1979, and all earlier production aircraft were certified at this weight. A further increase, to 510,000 pounds (230,000 kg), is also available, and most TriStar 500s are thought to have had this increase. Standard fuel capacity is 31,600 US gallons (120,000 L), giving the TriStar 500 a range of about 5,200 nautical miles (9,600 km) with 246 passengers and baggage.

Cabin

[edit]

The TriStar 500's maximum passenger capacity is 315, although no aircraft were operated with that number of seats. A typical two-class layout might include 21 First Class and 229 Economy Class for a maximum of 250 passengers. More spacious three-class layouts used on longer routes include 233 with 12 First Class, 32 Business Class, and 189 Economy Class with Delta Air Lines. The aircraft is equipped with six exits, two fewer than the long-body TriStars, thus reducing the exit limit maximum.

Operators

[edit]

One L-1011 TriStar is in service as of 2024 which is the Stargazer air-launch mothership, operated by Northrop Grumman Space Systems.[65][66][67]

Accidents and incidents

[edit]
The burnt out fuselage of the TriStar involved in Saudia Flight 163. After carrying out an emergency landing at Riyadh International Airport due to an in-flight cargo fire, a failure by the crew to carry out the emergency evacuation procedures led to all 301 people on board perishing from the flames and smoke.

As of December 2011, the L-1011 has been involved in 35 aviation occurrences,[68] including 10 hull-losses,[69] with 540 fatalities.[70] Of the four pioneering widebody aircraft (Boeing 747, McDonnell Douglas DC-10, L-1011, and Airbus A300/A310 family), the Lockheed L-1011 had comparatively few accidents and a better safety record than its competitors.[71][72][73]

  • On December 29, 1972, Eastern Air Lines Flight 401, an L-1011, crashed in the Florida Everglades as a result of the flight crew's failure to monitor the flight instruments during a malfunction of the landing gear position indicator system. The crash resulted in 101 fatalities, and was the subject of two TV movies, Crash and The Ghost of Flight 401. It was also the subject of a Mayday episode.[74][75]
  • On April 19, 1974, an L-1011 owned by TWA with the fleet number of 11007 caught fire at Logan Airport in Boston. It had landed four hours previously and there was no one on board. It was subsequently written off.[citation needed]
  • On April 12, 1977, Delta Air Lines Flight 1080, on takeoff from San Diego, had a left stabilizer jammed undetected in the full trailing-edge-up position.[76] This failure resulted in a large noseup and rolling moment that almost exceeded the capability of the flight controls.[77] The airplane was just about to stall in the clouds when Captain Jack McMahan,[78] with unusual insight, reduced power on the wing engines and began using the throttles to supplement the remaining flight controls, using differential and collective engine thrust.[79] Cabin crew moved all the passengers forward in the cabin to redistribute weight and help get the nose down. Steve Heidt, the flight engineer, said, "It probably didn't help much, but in that situation, we figured every little bit would help."[76] All the way from San Diego to Los Angeles, the aircraft flew with its pitch controlled by differential thrust between tail and wing engines, while the left roll tendency was compensated by wing differential thrust, and made a successful emergency landing in Los Angeles.[80] According to an incident analysis by Warren VanderBurgh, comprehensive crew training played a critical role in control recovery.[81]
  • On August 19, 1980, a fire destroyed the L-1011-200 used for Saudia Flight 163 on the ground after the pilots made an emergency landing at Riyadh's former International Airport due to fire in the rear of the aircraft. Delays in initiating the evacuation of the aircraft led to the deaths of all 301 occupants.[82][83]
  • On December 23, 1980, Saudia Flight 162, an L-1011, had a tire explode and penetrate the passenger cabin whilst in flight. The aircraft lost cabin pressure and two passengers were ejected through a hole in the cabin floor. The aircraft was later repaired and returned to service.[84]
  • On September 22, 1981, Eastern Air Lines Flight 935 departed Newark, New Jersey, and suffered an uncontained failure of its number two (tail) engine at 14,500 feet (4,400 m), while en route to San Juan, Puerto Rico.[85][86] The fragments from that engine damaged three of its four hydraulic systems resulting in fluid loss in them. The rudder pedals also jammed. The fragments struck but did not puncture the lines for the other hydraulic system; the captain was able to safely land the aircraft at John F. Kennedy International Airport, with some limited use of the outboard spoilers, the inboard ailerons and the horizontal stabilizer, plus differential engine power of the remaining two engines. There were no injuries. The L-1011 having four hydraulic systems (instead of three like the DC-10) allowed for a safe landing.[87][88]
  • On May 5, 1983, Eastern Air Lines Flight 855, an L-1011 with registration N334EA, while flying from Miami to Nassau, shut down the number 2 engine due to low oil pressure and began a return to Miami. Both of the remaining engines later failed. Without power, Flight 855 descended from 13,000 to 4,000 feet (1,200 m) before the number 2 engine was restarted and the aircraft landed in Miami without injuries. Incorrect engine maintenance had led to the loss of oil on all three engines.[89]
  • On April 5, 1984, a Saudia Lockheed L-1011 TriStar on final approach to Damascus from Jeddah was hijacked by a Syrian national. The hijacker demanded to be taken to Istanbul, Turkey, but changed his mind and requested to go to Stockholm. After landing in Istanbul to refuel, the pilot pushed the hijacker out the emergency exit whereupon he was arrested.[90]
A British Airtours TriStar overran the runway at Leeds Bradford International Airport in 1985.
  • On May 27, 1985, British Airtours Flight 101, registration G-BBAI, from Palma Airport, Mallorca, Spain overran the runway on landing at Leeds Bradford International Airport, West Yorkshire, United Kingdom. 12 of the 412 people on board suffered minor injuries when exiting down steep rear ramps. The aircraft was severely damaged,[91] but was eventually repaired and returned to service.[92]
  • On August 2, 1985, Delta Air Lines Flight 191, an L-1011, crashed while approaching Dallas/Fort Worth International Airport in microburst conditions. Eight of 11 crew members and 128 of the 152 passengers on board died, as well as one person on the ground after his vehicle was struck by the L-1011.[93][94]
  • On October 18, 1985, a Jordanian Airlines L-1011 experienced an inflight fire at 24,000 feet while on approach to Singapore. The fire burned through the rear pressure bulkhead, causing explosive depressurization of the cabin. The air rushing out of the cabin extinguished the fire, saving the aircraft. All 118 passengers and crew survived. The aircraft was later repaired and placed back into service.[95][96]
  • On May 3, 1986, Air Lanka Flight 512 (now SriLankan Airlines), an L-1011, was destroyed on the ground in Colombo, Sri Lanka, after a bomb exploded in the rear cargo hold, severing the tail and resulting in 21 deaths.[97]
  • On June 28, 1991, LTU International L-1011 registration D-AERI, suffered an interior fire during maintenance in a hangar at Düsseldorf Airport. Four engineers escaped injury, and the aircraft was declared a total loss.[98]
  • On July 30, 1992, TWA Flight 843, an L-1011, had its takeoff aborted by the captain after liftoff from John F. Kennedy International Airport, in response to a false stall warning. The aircraft landed too hard, breaking a wing spar and starting a fire. All 292 passengers and crew evacuated safely, with only 10 minor injuries. The airliner was destroyed by fire.[99]
  • On August 23, 1995, Delta Air Lines Flight 157, an L-1011 TriStar 1, suffered a rapid decompression after the pressure bulkhead failed. The flight crew initiated an emergency descent to 14,000 feet, and the plane landed safely at Los Angeles International Airport with no deaths or injuries to the 226 passengers or 10 crew. The aircraft was substantially damaged and later written off.[100]

Aircraft on display

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Tristar at the Royal Saudi Air Force Museum, Riyadh

Specifications

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Lockheed L-1011-500 TriStar blueprint drawing
L-1011 Specifications[115]
Variant L-1011-1 L-1011-200 L-1011-500
Cockpit crew Three
Seating 256 (mixed-class) 246 (mixed-class)
Exit limit 400[a] 330[a]
Interior width 18 feet 11 inches (5.77 m)
Length 177 ft 8+12 in (54.17 m) 164 ft 2+12 in (50.05 m)
Wingspan 155 ft 4 in (47.35 m) 164 ft 4 in (50.09 m)
Height 55 ft 4 in (16.87 m)
Wing area 3,456 sq ft (321.1 m2) 3,541 sq ft (329.0 m2)
MTOW 430,000 lb (200,000 kg) 466,000 lb (211,374 kg) 510,000 lb (231,332 kg)
OEW 241,700 lb (110,000 kg) 248,400 lb (113,000 kg) 245,400 lb (111,000 kg)
Fuel capacity 23,814 US gal (90,150 L) 26,502 US gal (100,320 L) 31,642 US gal (119,780 L)
Engines (×3) Rolls-Royce RB211-22 RB211-524B
Thrust (×3) 42,000 lbf (187 kN) 50,000 lbf (222 kN)
Mmo[116] Mach 0.90 (516 kn; 956 km/h)
Max speed[b] 539 kn (998 km/h) 539 kn (998 km/h) 539 kn (998 km/h)
Cruise[c] 520 kn (963 km/h) 515 kn (954 km/h) 525 kn (972 km/h)
Stall[d] 108 kn (200 km/h) 110 kn (204 km/h) 114 kn (211 km/h)
Range[e] 2,680 nmi (4,963 km) 3,600 nmi (6,667 km) 5,345 nmi (9,899 km)
Ferry range[f] 4,250 nmi (7,871 km) 4,935 nmi (9,140 km) 6,090 nmi (11,279 km)
Ceiling[116] 42,000 ft (12,800 m) 43,000 ft (13,100 m)
  1. ^ a b 10-abreast
  2. ^ 26,200 ft (8,000 m)
  3. ^ 30,000 ft (9,100 m)
  4. ^ max. landing weight, flaps and gear down
  5. ^ max. passengers + baggage
  6. ^ max. fuel

Deliveries

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1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 Total
17 39 41 24 16 12 8 14 24 28 13 5 5 3 249

Notable appearances in media

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See also

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References

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Further reading

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia
from Grokipedia
The Lockheed L-1011 TriStar is a wide-body, medium- to long-range developed and produced by the from 1968 to 1984. Powered exclusively by three high-bypass turbofan engines, with the tail-mounted unit featuring an innovative intake, the incorporated advanced features such as Category IIIB capability and a direct lift control system for precise handling. The first flew on November 17, 1970, and it entered commercial service on April 26, 1972, with as the launch customer. Conceived in the mid-1960s to serve high-density routes with up to 250 passengers in luxury, the TriStar was Lockheed's entry into the competitive widebody market dominated by the and McDonnell Douglas DC-10. Its development was hampered by severe delays stemming from Rolls-Royce's technical challenges and subsequent bankruptcy in 1971, which necessitated U.S. government financial intervention to sustain the program. Despite these innovations earning praise for reliability and crew appeal, only 250 units were built across variants including the standard -1, hot-and-high -200, and extended-range -500, far short of projections. The TriStar's commercial underperformance, exacerbated by high production costs, limited , and the absence of a freighter variant, resulted in substantial losses that compelled Lockheed to abandon altogether. Principal operators included , , and , with service persisting into the 2000s for some carriers and military conversions. While a technical triumph in and efficiency, the program's failure underscored the perils of supply chain dependencies and over-reliance on unproven technologies in a rapidly evolving industry.

Development

Origins and Market Context

In the mid-1960s, Lockheed, having shifted focus to after the Electra's production ended in 1961, sought to diversify by re-entering the commercial jet market amid surging global air travel demand. Airlines required efficient for medium-capacity routes that did not warrant the 747's high-volume, long-haul focus, which Pan American Airways had ordered in April 1966 for up to 500 passengers. specifically approached Lockheed and Douglas in the early 1960s for a smaller alternative capable of carrying about 250 passengers over transcontinental or medium transoceanic distances, such as New York to or to , emphasizing short-field performance and economic viability. Lockheed's response targeted this niche against competitors like the quadjet and the rival trijet , which American selected in 1968. The trijet layout was chosen to optimize range, , and runway performance for routes balancing efficiency with regulatory demands for engine redundancy on extended overwater flights, where twinjets faced restrictions under FAA rules limiting diversions. This configuration avoided the higher fuel consumption and maintenance complexity of four engines while enabling quieter cabins and better overall economics than larger jets amid pre-1970s fuel . Initial design studies began around 1966, leading to formal proposals by 1968 that incorporated advanced to appeal to carriers prioritizing reliability and passenger comfort. The program launched on , 1968, secured by ' order for 50 aircraft and ' commitment for 33 more, positioning the L-1011 to capture market share in a sector projected to grow with expanding international networks.

Design and Engineering Decisions

The Lockheed L-1011 TriStar's design emphasized aerodynamic efficiency and pilot workload reduction through innovative control surfaces, including an all-flying tail, or , which replaced the conventional trimmable horizontal stabilizer to provide enhanced and precise handling without the added weight and complexity of separate and stabilizer mechanisms. This configuration allowed the entire horizontal tail to pivot as a unit in response to inputs, contributing to smoother pitch control particularly during high-speed flight and . Complementing this was the direct lift control (DLC) system, which deployed outboard spoilers symmetrically to modulate lift directly without altering pitch attitude, enabling finer adjustments to descent rate and glideslope during approach and landing for reduced vertical touchdown scatter and improved passenger comfort. Cabin design prioritized passenger comfort and , accommodating 250 to 400 passengers in a twin-aisle layout depending on configuration, with no entry doors positioned over the wings to facilitate unobstructed evacuation slides and optimal class zoning. The propulsion arrangement, featuring two engines under the wings and a third rear-mounted via an , positioned powerplants away from the , significantly lowering cabin noise levels compared to contemporaries and enhancing the onboard experience. This rear-engine placement also supported a cleaner underfuselage profile, aiding ground clearance and maintenance access while aligning with Lockheed's philosophy of integrating military-derived redundancy principles into for robust structural integrity, though specific fail-safe adaptations drew from the company's experience with large like the C-5 Galaxy. These choices reflected Lockheed's commitment to advancing and reliability in widebody airliners, prioritizing first-flight efficiency and long-term operational economics over simpler designs, even as they introduced complexities in integration. The resulting balanced high-capacity interiors with aerodynamic refinements, such as a with extended span options for better lift-to-drag ratios in later variants, though the baseline emphasized stability over extreme range at the expense of higher development risks.

Rolls-Royce RB211 Engine Challenges

Lockheed selected the turbofan for the L-1011 TriStar in March 1968, opting for this unproven design over established alternatives from and due to promises of superior from its high-bypass ratio, reduced via advanced fan , and lighter weight enabled by innovative composite materials. The 's three-spool and initial plan for Hyfil carbon-fiber fan blades positioned it as a technological leap, but this choice locked Lockheed into sole dependency on Rolls-Royce, forgoing that competitors like the enjoyed with multiple suppliers. Development encountered severe technical obstacles, particularly with the fan blades, as the original narrow-chord Hyfil composites failed bird-strike and durability tests, necessitating a costly redesign to wider-chord blades that increased weight and complexity while requiring extensive revalidation. These issues delayed RB211 from the targeted 1970 timeline to March 1972, stalling TriStar and integration since the prototype's November 1970 used incomplete engines. The redesign's overruns, estimated at hundreds of millions in unrecovered costs, stemmed from the engine's ambitious specifications exceeding Rolls-Royce's prior experience with high-bypass fans. By February 1971, these escalating costs triggered Rolls-Royce's bankruptcy, with the company citing RB211 losses exceeding £100 million as the primary cause, threatening the entire TriStar program amid Lockheed's own financial strains. The government nationalized Rolls-Royce and provided a £130 million to ensure continuity, while the administration under President Nixon exerted diplomatic pressure on Britain to honor contracts, averting potential cancellation of 50 TriStar orders worth $750 million. This intervention preserved the engine supply but imposed renegotiated terms, including price hikes that further burdened Lockheed without resolving underlying certification setbacks.

Production Delays and Financial Strain

The prototype Lockheed L-1011 conducted its first flight on November 16, 1970, from the company's Palmdale, California facility, marking the start of flight testing for the widebody airliner. This event followed assembly at Plant 10 in Palmdale, where production ramp-up had begun amid efforts to meet launch customer commitments. Extensive testing, encompassing thousands of hours to validate the aircraft's advanced , direct-lift control, and structural integrity, extended the certification timeline. The granted type certification in April 1972, approximately 17 months after the , delaying entry into service relative to competitors like the McDonnell Douglas DC-10. Initial deliveries commenced shortly thereafter, with Eastern Air Lines receiving the first production L-1011-1 on April 26, 1972, enabling revenue operations on routes such as to New York. However, these production delays compounded financial pressures at Lockheed, as manufacturing scale-up at Palmdale strained cash flows amid fixed tooling and labor commitments. By mid-1971, cumulative overruns had escalated program costs well beyond initial estimates of around $1 billion, prompting Lockheed to seek emergency financing. The U.S. government approved $250 million in loan guarantees under the Emergency Loan Guarantee Act of 1971, averting potential and enabling completion of certification and early deliveries. Total development expenditures ultimately surpassed $2 billion, reflecting the high fixed costs of certifying such an ambitious design in a competitive market.

Technical Features

Airframe and Aerodynamics

The Lockheed L-1011 TriStar featured a conventional fabricated from aluminum materials with a circular cross-section optimized for pressurization and structural efficiency. The baseline L-1011-1 measured 54.17 meters (177 feet 8 inches) in overall length, while the stood at 47.34 meters (155 feet 4 inches) across production models. Fuselage modifications in variants included stretches to 56.95 meters (186 feet 10 inches) in the L-1011-200 for increased capacity and shortenings to 50.05 meters (164 feet 2 inches) in the L-1011-500 to enhance fuel capacity and range. The wing design incorporated advanced high-lift devices, including nine leading-edge slats with on inboard sections and Fowler flaps on outboard panels, enabling effective takeoff and landing performance on shorter runways. Aerodynamically, the sections delayed drag divergence at cruise speeds, reducing and supporting efficient long-range operations. The clean wing, unencumbered by forward engine nacelles, further minimized interference drag. Unique to the TriStar's trijet layout, the center engine mounted in the tail cone received airflow via an intake elevated above the fuselage, which protected against ground debris ingestion while contributing to overall drag reduction of up to 4 percent compared to alternative configurations. This placement enhanced yaw stability and significantly lowered cabin noise levels by distancing engines from passenger areas. The 's curvature maintained pressure losses akin to straight ducts, preserving engine performance without compromising aerodynamic efficiency.

Propulsion and Power Systems

The Lockheed L-1011 TriStar utilized three Rolls-Royce RB211-22B high-bypass ratio engines, each delivering 42,000 lbf (187 kN) of , with the configuration consisting of two under-wing engines and one center-mounted in an at the rear . These engines incorporated reversers on all three units to enhance braking performance during landing, and their design included features such as extended fan cowls to suppress noise from the cold stream exhaust. The RB211's innovative three-spool —comprising low-, intermediate-, and high-pressure sections—enabled higher thermodynamic and lower specific fuel consumption than two-spool rivals, though real-world operations revealed that the layout imposed inherent penalties in overall compared to emerging twin-engine designs due to the additional drag and weight of the third engine. The aircraft's fuel featured four main wing tanks and auxiliary center-section tanks, providing a baseline capacity of 23,814 gallons (90,150 liters) for the L-1011-1, with later variants expanding this through additional tanks or higher-density fuel allowances. Automated transfer logic governed fuel sequencing, drawing from outboard tanks to supply the center engine and while pumping from inner center tanks (1A and 3A) to inboard tanks (1 and 3) to preserve longitudinal center-of-gravity limits during flight. This prioritized engine-specific feeds—left tank to left engine, right to right, and outboards to center—while incorporating cross-feed capabilities for imbalance correction, though empirical data from service indicated occasional manual interventions were needed under asymmetric failure conditions to avoid exceeding CG envelopes. Electrical power generation relied on three engine-driven integrated drive generators (IDGs), each rated at 90 kVA and 400 Hz, providing constant-frequency output via variable-speed drives to support , lighting, and hydraulic pumps. The tail-mounted ST6L-73 (APU), comprising a section with axial and centrifugal compressors driving pneumatic and electrical loads up to 90 kVA, served as the primary ground power source and in-flight backup, with its location forward of the center inlet ensuring accessibility but exposing it to potential risks during high-power operations. In practice, the APU's reliability supported extended ground operations, yet its single-unit design represented a absent in dual-APU contemporaries, constraining dispatch flexibility under certain regulatory minima.

Avionics and Flight Control Systems

The Lockheed L-1011 TriStar incorporated the (AFCS), a highly redundant setup that automated many flight phases to minimize pilot workload and improve handling qualities. This system featured triple hydraulic channels and dual-dual computing architecture, enabling fail-operational performance even after a . The AFCS integrated functions that permitted hands-off operation from cruise descent through , a capability advanced for its era. Central to navigation was the inertial navigation system (INS), which relied on gyroscopic sensors aligned to the aircraft's initial longitude and latitude for dead-reckoning over long distances without ground-based updates. This setup supported precise positioning in oceanic or remote routes, reducing dependence on radio aids. The TriStar achieved FAA certification for Category IIIB upon entering service in April 1972, allowing automatic landings with decision heights as low as 50 feet and down to 150 meters. This was the first such approval for a widebody , leveraging redundant altimeters, localizer/glideslope receivers, and flight directors for zero-visibility operations when equipped. Later variants and operators extended to full Category IIIB with zero decision height. Flight controls included an all-flying , or , hydraulically actuated without a separate , which enhanced pitch stability and responsiveness compared to conventional trimmable stabilizers. Elements of the AFCS incorporated fly-by-wire assist functions, including direct lift control that used electronically managed spoilers to adjust lift independently of pitch for precise handling—a feature not present in the DC-10—as well as early digital signaling akin to partial for stabilizer positioning, predating widespread adoption in commercial airliners. The system's active controls also foreshadowed collision avoidance through envelope protection limits on bank angles and speeds.

Other Innovations and Systems

The Lockheed L-1011 TriStar incorporated a center fuselage-mounted body with two wheels alongside the primary wing-mounted main landing gears featuring four-wheel bogies, facilitating short-field operations by distributing weight more evenly on runways or unprepared surfaces. This configuration supported takeoff and landing distances reduced by up to 1,000 feet compared to competitors without body gear. The braking system included autobrakes that automatically applied a pilot-selected deceleration rate upon —typically 8-12 feet per second squared—and anti-skid protection operating on individual wheels for both primary and backup modes, enhancing stopping performance and tire longevity on contaminated runways. Environmental controls relied on an integrated pneumatic system (IPS) that bled hot, pressurized air from the engines to drive cabin packs, outflow valves for pressurization, and dedicated cooling for avionics bays, achieving cabin altitudes equivalent to 8,000 feet (2,440 meters) at a 41,000-foot cruise while minimizing compressor workload. Pressurization redundancy featured dual outflow valves with automatic, standby, and manual modes, capable of maintaining differential pressures up to 8.9 psi, while passenger oxygen deployed via ceiling-mounted masks linked to chemical generators providing 12-22 minutes of flow at 15,000 feet equivalent. Hydraulic and electrical systems emphasized quadruple redundancy informed by Lockheed's military transport designs, such as the C-5 Galaxy, to ensure fail-operational integrity. Four independent hydraulic circuits—each with separate reservoirs, engine-driven pumps, and accumulators—powered flight surfaces, gear extension/retraction, and brakes, allowing full control retention after loss of any three systems, unlike the three-system setup in rival aircraft. Electrical distribution utilized four engine generators plus an APU unit feeding 115/200 VAC buses with automatic load shedding and transfer capabilities, supporting ancillary functions like power and anti-icing without single-point vulnerabilities.

Variants

L-1011-1 Baseline

The L-1011-1 constituted the initial production variant of the Lockheed TriStar series, establishing the standard configuration referenced in subsequent derivatives. Optimized for short- to medium-range routes, it accommodated 256 passengers in a typical two-class layout comprising and sections. This baseline model featured a of 430,000 pounds and a range of approximately 2,680 nautical miles with full passenger complement, positioning it 250 nautical miles shorter than comparable competitors like the for similar payloads. The certified the L-1011-1 on April 14, 1972, enabling commercial operations shortly thereafter. The first delivery occurred to on April 5, 1972, followed by initiating passenger service the same year. Delta received its initial aircraft and commenced revenue flights on December 15, 1973. Production of the L-1011-1 totaled 160 units, accounting for the majority of the TriStar family built before overall program cessation in 1984. These aircraft primarily served U.S. carriers on domestic and transcontinental routes, underscoring the variant's role as the foundational TriStar .

Extended Range and Capacity Variants

The L-1011-100 variant extended operational range through auxiliary fuel tanks integrated into the wing structure, providing approximately 930 additional nautical miles over the baseline model's capabilities. This modification supported transatlantic and longer domestic routes, with fuel capacity enhancements enabling greater flexibility for operators like . The L-1011-200 incorporated upgraded Rolls-Royce RB211-524 engines featuring pinion gearing to deliver higher thrust ratings, particularly optimized for hot-and-high airport performance. These engines allowed a maximum range of 4,918 nautical miles with full loads and 3,680 nautical miles with maximum passenger payload, facilitating service on extended routes in challenging climates. The L-1011-500 featured a shortened fuselage measuring 164 feet 2 inches in length—reduced from the standard 177 feet 8 inches—to improve aerodynamic efficiency and fuel economy for ultra-long-haul operations. First entering with on May 7, 1979, operating the London Heathrow to route, the -500 prioritized range over cabin volume while maintaining reliability. Across these variants, capacity enhancements focused on high-density seating arrangements, with the airframe certified for up to 400 passengers in all-economy configurations to maximize revenue on dense short-to-medium sectors. Operators such as Eastern Air Lines implemented such layouts, balancing the TriStar's spacious twin-aisle interior against demand for higher load factors. This flexibility complemented range improvements, allowing airlines to adapt the aircraft for varying mission profiles without structural redesigns.

Specialized Modifications

![Royal Air Force Lockheed L-1011 TriStar K1]( The L-1011-50 represented a specialized upgrade to the baseline L-1011-1, featuring reinforced and an increased of up to 466,000 pounds (211,000 kg), enabling enhanced short-field performance and greater payload capacity compared to standard models. This variant was primarily implemented through conversions rather than new manufacturing, with limited adoption due to the TriStar program's overall production constraints. In the military domain, the Royal Air Force procured nine second-hand L-1011-500 aircraft from and Pan American World Airways between 1982 and 1984, converting six to tanker-transport roles. The TriStar K1 configuration, used on three airframes, included two underwing hose-and-drogue refueling pods for operations, supporting RAF strategic airlift and tanker missions primarily with No. 216 Squadron at until retirement in 2014. These conversions involved minimal external modifications beyond the refueling equipment, preserving the aircraft's commercial fuselage while adapting it for defense needs. A unique civilian adaptation emerged with the Stargazer, an L-1011-100 (manufacturer serial number 1012) acquired by in 1992 and modified in 1994 by Marshall Aerospace. This conversion reinforced the upper fuselage to carry the air-launched rocket, enabling satellite deployments from altitudes over 40,000 feet (12,000 m); the aircraft conducted its first Pegasus launch in 1994 and continues operations under as of 2024, marking the last flying TriStar. Lockheed explored unbuilt concepts such as convertible freighter variants, including proposals for rapid passenger-to-cargo reconfiguration, but market demand and the program's cessation precluded development.

Operational History

Commercial Deployment


Eastern Air Lines became the launch customer for the Lockheed L-1011 TriStar, taking delivery of the first production aircraft on April 6, 1972, and commencing commercial passenger service on April 26, 1972, with flights between Miami and New York. The airline initially deployed the TriStar on high-density domestic routes, including shuttle services, leveraging its capacity for up to 256 passengers in a typical three-class configuration.
Delta Air Lines assembled the largest TriStar fleet, operating up to 70 at its peak, with service beginning in 1973 on domestic and transatlantic routes such as to and New York to . Other major U.S. operators included (TWA), which flew 39 TriStars primarily on transatlantic services like New York to and , and Pacific routes to and , and Eastern, which expanded to 44 for intra-U.S. and Latin American flights. Internationally, utilized TriStars for European and transatlantic operations from , while employed them on Pacific routes from to the and Europe. In service, the TriStar demonstrated operational advantages including dispatch reliability rates of 98.9 percent, surpassing initial targets, which supported consistent schedule adherence. Its low noise certification—takeoff at 98.0 dB, sideline at 96.9 dB, and approach at 100.2 dB—enabled access to noise-sensitive urban airports and curfew-restricted slots, such as those at London Heathrow. A total of 250 TriStars entered commercial service worldwide, serving peak operations through the on medium- to long-haul routes. By the and early , most fleets were retired as airlines shifted to twin-engine jets offering superior under extended-range twin-engine operational performance standards (ETOPS), with Delta completing phase-out in 2001.

Military and Research Applications

The Royal Air Force operated nine L-1011-500 TriStars in dual-role configurations as air-to-air refueling tankers and troop transports from 1983 to 2014. Six aircraft were acquired from British Airways in December 1982, with three additional units purchased from Pan American Airways in 1984. Variants included the K1 and KC1 for refueling duties equipped with hose-and-drogue systems, and the C2 and C2A for passenger and cargo transport capable of carrying up to 265 personnel or 16 tonnes of freight over 4,000 miles. These aircraft supported operations by delivering over 250,000 troops and supplies globally, including during conflicts in the Falklands, Gulf War, and Afghanistan. The fleet was retired following the final operational flight on March 24, 2014. NASA utilized modified L-1011 TriStars for aeronautical research programs focused on enhancing efficiency and safety. In the late 1970s, a cooperative -Lockheed effort tested active controls on the L-1011 to improve energy efficiency through automated flight management. Subsequent projects included vortex flow using smoke generators to study aerodynamic wakes, aiding in the understanding of trailing vortices for safer spacing. In 2012, an L-1011 supported the Adaptive Performance Optimization experiment, employing variable camber to reduce drag and fuel consumption by adapting to flight conditions in real-time. The Stargazer, registered N140SC, represents the sole remaining airworthy L-1011, converted in 1994 by Orbital Sciences (now ) into a launch platform for the XL rocket. This modification enables air-launch of small satellites into from altitudes above 40,000 feet, supporting scientific and commercial payloads since its first mission in 1994. As of August 2025, Stargazer continues operations from , with recent flights confirming its ongoing role despite the last launch occurring in 2021.

Retirement and Final Uses

The majority of L-1011 TriStars were retired from passenger service by major airlines in the late 1990s and early 2000s, driven by high operating costs, engine maintenance challenges, and the rise of more efficient twin-engine widebodies. Delta Air Lines conducted its final revenue passenger flight with the type on July 31, 2001, operating TriStar 1 N728DA on a roundtrip from Atlanta to Orlando. Smaller operators and charters extended use into the mid-2000s, with the last documented commercial passenger operations concluding around 2008. Post-retirement, dozens of airframes were ferried to storage facilities, including the Southern California Logistics Airport in Victorville, California, where they underwent part-out, disassembly, or long-term desert preservation amid harsh environmental conditions accelerating corrosion. Efforts to repurpose surplus TriStars as freighters faced significant barriers, including the aircraft's structural weight limitations, inferior payload-range capabilities compared to the DC-10, and elevated maintenance demands from the complex intake on the tail-mounted RB211 engine, which complicated inspections and increased downtime costs. Lockheed explored conversions, such as modifying 13 ex-Delta airframes in the early , but secured no firm customers, limiting successful freighter adaptations to a handful operated briefly by niche cargo firms like Kitty Hawk International. The absence of a dedicated freighter variant or certified passenger-to-freighter program further diminished viability against competitors with established conversion ecosystems. On the ground, retired TriStars found roles in training and simulation. The FAA's Aircraft Rescue and Fire Fighting Research Facility at utilizes an L-1011 equipped with fire-hardened test chambers to simulate onboard blazes and evaluate suppression systems, supporting ARFF protocol development. Other airframes served as fire training hulks for emergency responders, undergoing controlled burns to practice widebody incident response. One early , derived from Delta's fleet, was retained for instructional purposes at the Delta Flight Museum. In flight, a single modified L-1011-100, designated Stargazer (N140SC), continues specialized operations as of 2025, launching Pegasus XL rockets for from sites like , marking the type's sole remaining airworthy example outside preservation.

Safety and Incidents

Accident Statistics

A total of 250 Lockheed L-1011 TriStar aircraft were produced between 1970 and 1984. Over its operational history from 1972 into the 2000s, the type was involved in 35 reported occurrences, including 10 hull losses, resulting in approximately 540 fatalities. The hull loss rate stood at 4% of the fleet (10 out of 250 aircraft), lower than the McDonnell Douglas DC-10's rate of about 7.4% (33 es out of roughly 446 produced). Fatality rates per million flight hours were estimated at 66 for the L-1011, comparable to the DC-10's 74 but slightly higher than the 747's 61 as of the late ; however, the L-1011 exhibited no recurrent design-related failures akin to the DC-10's cargo door issues, with most losses attributed to external factors such as adverse weather or crew errors by official investigations.
MetricL-1011 TriStar Value
Total Produced250
10
Total Occurrences35
Fatalities~540
Hull Loss Rate (% of fleet)4%

Notable Incidents and Lessons Learned

On December 29, 1972, , operating a Lockheed L-1011-1 (N310EA) from New York to , crashed into the approximately 18 miles northwest of , killing 101 of the 176 occupants. The (NTSB) determined the probable cause as the flight crew's failure to monitor the aircraft's following an inadvertent disconnection of the during troubleshooting of a burned-out nose landing gear position indicator light bulb. The crew's fixation on the minor equipment malfunction, compounded by inadequate cross-checking and breakdown in crew coordination, allowed the aircraft to descend unnoticed from 2,000 feet into the swamp. This accident highlighted deficiencies in (CRM), prompting the FAA to mandate enhanced training protocols emphasizing altitude awareness, instrument monitoring, and assertive communication among crew members to prevent distraction-induced deviations from basic flight duties. On August 19, 1980, , a Lockheed L-1011-200 (HZ-AHK) en route from to , experienced an in-flight originating in the aft compartment shortly after takeoff, prompting an emergency return to where it landed safely but failed to evacuate, resulting in the deaths of all 301 occupants from and toxic gases. The Saudi accident investigation attributed the 's initiation to a possible oxygen system leak or , but the catastrophe ensued post-landing due to crew incapacitation from heat, fumes, and hydraulic failures exacerbated by the flight engineer's erroneous shutdown of packs, which caused cabin overpressurization and trapped smoke. Contributing factors included the captain's decision to taxi to a remote area before evacuation, cultural cockpit hierarchy inhibiting junior crew input, and inadequate smoke penetration barriers in holds. The incident underscored the critical need for improved compartment isolation, rapid evacuation drills overriding non-essential procedures, and CRM adaptations to address authority gradients in diverse crews, influencing global standards for post-fire evacuation and smoke hazard mitigation in . On August 2, 1985, , a Lockheed L-1011-1 (N726DA) approaching , encountered a microburst windshear during , leading to a loss of control, impact with the ground short of the runway, and a subsequent fireball that killed 134 of the 163 occupants and one person on the ground. The NTSB identified the primary cause as the flight crew's penetration of a thunderstorm's rain shaft into an undetected microburst, producing downdrafts exceeding 30 knots and windshear gradients that overwhelmed the 's performance margins despite go-around attempts. Contributing elements were the lack of onboard predictive windshear detection systems and insufficient meteorological awareness of microburst hazards at the time. This event catalyzed FAA requirements for predictive windshear installation on transport-category , mandatory windshear escape maneuver training, and enhanced deployment to forecast and alert on microbursts, significantly reducing windshear-related accidents thereafter.

Evaluation of Safety Features

The Lockheed L-1011 TriStar featured a fail-operational system certified for Category IIIA operations from initial delivery in 1972, permitting automatic landings with visibility as low as 700-foot runways visual range and no decision height, thereby mitigating risks associated with fog or heavy precipitation that historically contributed to runway excursions or . This capability was enhanced by inertial navigation and triple-channel redundancies, allowing continued safe descent and touchdown even after failure of one or two channels. Flight control systems incorporated triple hydraulic independence and fail-operational active controls, tested extensively in NASA-Lockheed programs starting in the early 1970s, which preserved maneuverability and stability during dual hydraulic or electrical outages, averting potential loss-of-control scenarios in over 99% of simulated failure modes per Lockheed certification data. Built-in test equipment further supported rapid fault isolation, reducing downtime and enhancing overall dispatch reliability to levels exceeding 99% for major operators by the late 1970s. Notwithstanding these advances, the aircraft's intricate and propulsion architecture imposed elevated training requirements, with pilots needing 50-100 additional simulator hours compared to contemporaries like the for proficiency in automated modes, potentially straining airline resources and introducing latent procedural vulnerabilities if recurrent training lapsed. The configuration of the center engine, optimized for reduced drag and noise, nonetheless facilitated axial fire propagation from fan blade failures to structures due to constrained and limited compartmentalization, manifesting in infrequent but high-severity thermal events that necessitated post-1980 design retrofits like enhanced firewalls. Delta Air Lines, which operated 59 TriStars from 1979 to 2001, commended the type's hydraulic and electrical redundancies for enabling uneventful continuations after isolated failures, attributing dispatch reliability rates above 98% to inherent system robustness rather than exceptional maintenance. These features collectively elevated safety benchmarks, informing FAA evolution toward Category IIIB/C mandates in the and fail-operational criteria for future widebodies, as validated through TriStar service data integrated into advisory circulars.

Economic Performance

Sales Figures and Market Competition

Lockheed delivered a total of 250 L-1011 TriStar to airlines between 1972 and 1984. In direct competition within the widebody market segment, McDonnell Douglas produced 446 DC-10s, encompassing 386 commercial passenger variants and 60 military KC-10 Extenders. The , targeting a larger very-long-range segment, achieved far greater volume with 1,574 units built over its production run from to 2023.
Aircraft ModelTotal Units Produced/Delivered
Lockheed L-1011 TriStar250
(incl. KC-10)446
1,574
The TriStar's limited was exemplified by its loss of a pivotal order from in 1970, which opted for the DC-10 after evaluating competing bids. Contributing to the DC-10's edge, it achieved FAA certification and entered commercial service on August 5, 1971, nearly a year ahead of the TriStar's first revenue flight on April 26, 1972. The DC-10 also benefited from a lower , estimated at around $18-20 million per unit in early 1970s dollars, compared to the TriStar's higher cost of approximately $20-25 million, reflecting the latter's more advanced and direct-lift engine design. Despite these challenges, the TriStar secured regional successes, particularly with , which expanded its fleet to a peak of around 56 units, representing the largest operator of the type and leveraging it for domestic and transatlantic routes. However, persistent development delays, including engine certification issues extending into 1972, constrained broader global adoption against the earlier-established DC-10.

Financial Impact on Lockheed

The development of the Lockheed L-1011 TriStar incurred substantial cost overruns, ultimately resulting in approximately $2.5 billion in program losses for the company, exacerbated by delays from engine supplier Rolls-Royce and constraints. To achieve , Lockheed required sales of around 500 units, but production totaled only 250 before cessation in 1984, leaving the program far short of financial viability. In July 1971, amid acute liquidity crises tied to the TriStar and concurrent military program shortfalls like the C-5A Galaxy, Lockheed faced imminent bankruptcy, prompting Congress to enact the Emergency Loan Guarantee Act, which authorized up to $250 million in federal guarantees for private loans to the firm. This intervention, approved by President Nixon on August 2, 1971, provided critical short-term relief, particularly as the winding down of U.S. involvement in the diminished anticipated military procurement revenues. The TriStar's fiscal burden precipitated Lockheed's permanent withdrawal from the commercial airliner sector following the program's end, redirecting corporate resources toward military contracts that ensured long-term stability, such as developments including the F-117 . By 1976, the airliner line had already accrued nearly $1 billion in pretax losses, underscoring its role in reshaping the company's strategic priorities away from civilian aviation.

Causal Analysis of Commercial Failure

Lockheed's strategic decision to center the L-1011 design around the unproven engine, selected for its promised efficiency gains via composite fan blades, exposed the program to severe delays when Rolls-Royce encountered technical hurdles and filed for on February 4, 1971. This event necessitated a and of Rolls-Royce, postponing TriStar certification and first delivery until April 1972, over a year after the competing entered service in August 1971. Lockheed's predominant background, exemplified by projects like the C-5 Galaxy, fostered a culture accustomed to flexible funding and extended development cycles, which ill-prepared the company for the rigid timelines and cost sensitivities of commercial certification under FAA oversight. The TriStar's engineering emphasis on cutting-edge features, such as an advanced capable of Category III landings and direct lift control for superior low-speed handling, elevated manufacturing complexity and resulted in direct operating costs that exceeded those of the simpler DC-10 by margins operators found prohibitive for medium-haul routes. Maintenance burdens were amplified by the configuration's three engines and intricate systems, deterring airlines seeking parity with the DC-10's lower per-flight-hour upkeep, particularly as fuel prices surged following the . Lockheed's failure to pivot toward more efficient twin-engine derivatives, unlike Boeing's subsequent 767, locked the TriStar into a niche eroded by rising costs and evolving regulatory preferences for etops-capable twins. By the time production peaked, the widebody market had bifurcated: the dominated high-density long-haul, while the DC-10 captured demand with earlier availability and broader adaptability, leaving insufficient volume for the late-entering TriStar despite its technical refinements. This misalignment, compounded by Lockheed's over-optimism in forecasting 400-500 sales based on pre-delay orders, culminated in only 250 units built, forcing the company to absorb losses exceeding $2.5 billion in today's dollars and exit entirely by 1984.

Legacy

Technological Influence

The Lockheed L-1011 TriStar pioneered advanced automatic flight control systems (AFCS), incorporating electronic interfaces that served as precursors to technology, thereby enhancing precision handling and operational efficiency. This system allowed for automated descent control and integration with inertial navigation, reducing pilot workload and improving fuel economy through optimized flight paths. A key innovation was the TriStar's CAT-IIIB capability, certified in 1972, which enabled fully automatic in low-visibility conditions down to 50-foot decision heights, setting early benchmarks for redundant, fail-operational landing systems later refined in aircraft like the A320 and 777. The dual-dual architecture provided the necessary redundancy for such operations without reliance on flight management systems, influencing the evolution of digital autoland standards. In partnership with , Lockheed evaluated active controls on the L-1011, including gust load alleviation and direct lift control, which demonstrated potential for reduced structural weight and improved ride quality, concepts that informed energy-efficient flight control advancements in subsequent widebody designs. These tests, conducted in the 1970s, yielded data on maneuver load alleviation, contributing to the foundational understanding of systems. The TriStar's configuration emphasized thrust balance and for transoceanic routes under pre-ETOPS regulations, highlighting efficiency trade-offs in engine placement that, despite the later dominance of high-bypass twins, provided analytical insights into integration for medium- to long-range operations. Operational data from the fleet, which achieved dispatch reliability rates of up to 99.98% over extended service, supported refinements in reliability modeling and practices across the industry. The aircraft's integrated drive generator, the first in a jetliner, further advanced electrical power systems reliability.

Preservation Efforts

As of 2025, the sole airworthy Lockheed L-1011 TriStar is the Stargazer (N140SC), operated by to serve as a launch platform for rockets from modified underbelly pylons. This aircraft, originally delivered in 1978, undergoes specialized maintenance to remain flight-capable for these missions, with its last recorded flight activity noted in late 2024 awaiting further operations. No other L-1011 airframes are certified for flight, as the fleet's retirement has led to widespread scrapping or storage without active upkeep. Approximately five L-1011 airframes are preserved for static display in museums and aviation sites worldwide. The Delta Flight Museum in exhibits the nose section of the original (Ship 1), allowing visitors to explore early instrumentation from the 1970 first flight. In , the Royal Saudi features a former L-1011-200 as a prominent , showcasing the aircraft's external structure and historical . Additional preserved examples include one at the Atlantic Canada Aviation in Enfield, , highlighting regional aviation heritage. Efforts to restore additional airframes to operational condition encounter formidable obstacles, including the scarcity of obsolete spare parts after over four decades since production ended in , and escalating costs for overhauling engines amid the retirement of remaining users. These factors render full restorations economically prohibitive for most private or institutional collectors, limiting preservation to static exhibits rather than flyable replicas. Preserved TriStars contribute to educational initiatives through museum displays that demonstrate advanced 1970s and design principles. Complementing physical artifacts, virtual recreations such as the iniBuilds L-1011 add-on for , teased for release in 2025, enable detailed simulation of the aircraft's , inertial navigation, and engine integration for training and historical study.

Cultural Depictions

The Lockheed L-1011 TriStar appeared in the 1992 action film , where a specific aircraft (N309EA, later operated by ) served as the hijacked plane central to the plot involving terrorists seizing control mid-flight. The film's depiction emphasized the aircraft's size and layout in high-stakes sequences, reflecting early perceptions of widebody jets as vulnerable to such threats. A BWIA International Airways L-1011 also featured briefly in the 2003 comedy Old School, appearing in a takeoff scene that highlighted the type's distinctive trijet configuration amid the film's nostalgic tone. Among aviation enthusiasts, the TriStar earned the nickname "Whisperliner" from Eastern Air Lines, coined for its exceptionally quiet passenger cabin and takeoff noise levels enabled by the Rolls-Royce RB211 engines' design. This moniker persists in online forums and historical accounts, symbolizing the aircraft's advanced noise suppression as a hallmark of its engineering focus on passenger comfort. In 2020s retrospective videos on platforms like , the TriStar is frequently portrayed by aviation historians as an "over-engineered masterpiece," crediting its pioneering and systems while attributing its limited production to Rolls-Royce delays and competition from the McDonnell Douglas DC-10. These depictions underscore a narrative of technical brilliance overshadowed by commercial misfortunes, appealing to niche audiences valuing over figures.

Specifications

The baseline Lockheed L-1011-1 TriStar measured 177 feet 8 inches (54.17 meters) in length, had a of 155 feet 4 inches (47.34 meters), and stood 55 feet 4 inches (16.87 meters) in . It was powered by three Rolls-Royce RB211-22B high-bypass engines, each rated at 42,000 pounds-force (187 kilonewtons) of . Performance characteristics included a maximum operating speed of Mach 0.90, a service ceiling of 42,000 feet (12,800 meters), and a range of approximately 4,000 nautical miles (7,410 kilometers) with a typical load of 216 passengers.
SpecificationValue
Maximum takeoff weight430,000 pounds (195,000 kilograms)
Fuel capacity23,700 U.S. gallons (90,000 liters)
Wing area3,456 square feet (321 square meters)

References

  1. https://commons.wikimedia.org/wiki/File:RSAF_Museum_Lockheed_L-1011_Tristar.jpg
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