Lockheed L-1011 TriStar

The Lockheed L-1011 TriStar, said as "El-ten-eleven," is a wide-body trijet built in the United States for medium-to-long routes. It was the third wide-body airliner to start flying passengers, following the Boeing 747 and the McDonnell Douglas DC-10. The plane can hold up to 400 people and fly more than 4,000 nautical miles. Its three Rolls-Royce RB211 engines are placed with one under each wing and a third in the back of the fuselage, fed by an S-shaped duct on top. The TriStar also has autoland, an automatic descent system, and could be fitted with a lower-deck galley or lounge. Lockheed made the L-1011 in two body lengths. The first version, the L-1011-1, flew in November 1970 and began carrying passengers for Eastern Air Lines in 1972. A shorter, longer-range model, the L-1011-500, first flew in 1978 and entered service with British Airways the next year. The original-length TriStar also came as the heavier L-1011-100, the more powerful L-1011-200, and the upgraded L-1011-250. After production, some L-1011-1s were converted into the L-1011-50 and L-1011-150 with higher takeoff weights. Sales of the TriStar suffered because of two years of delays caused by money and development problems at Rolls-Royce, the only engine supplier. From 1968 to 1984, Lockheed built 250 TriStars at its plant in Palmdale, California, north of Los Angeles. When production stopped, Lockheed left the commercial airplane business because sales were below what it had hoped. As of 2026, just one L-1011 remains in service, named Stargazer. **Development**

**Origins**

During the 1960s, American Airlines asked Lockheed and its rival Douglas (later McDonnell Douglas) to build an airliner that could carry 250 passengers across the United States. Lockheed had not made a civilian plane since the L-188 Electra in 1961. The Electra, designed in the 1950s, used turboprop engines—a technology Lockheed had used successfully on the C-130 Hercules military transport. Even after Lockheed fixed vibration problems that caused early crashes, the big-airliner market was moving to jets like the Boeing 707 and Douglas DC-8. Lockheed won military jet contracts with the C-141 StarLifter and pushed into very large jets with the C-5 Galaxy, which used high-bypass turbofan engines. Boeing lost that military contract but later captured a much bigger civilian market with its 747 wide-body. Lockheed, having run into trouble with some military programs, was keen to re-enter the civilian market with a smaller wide-body jet. Its answer was the L-1011 TriStar. Douglas answered American Airlines with the DC-10, a similar three-engine plane of about the same size. Though alike, the two planes took very different engineering paths. McDonnell, which had just taken over Douglas, ran the DC-10 development on a tight budget, refusing cost overruns even if it meant cutting corners on safety, and reused technology from the DC-8. Lockheed, on the other hand, aimed to use the most advanced technology available, and when that didn't exist, it invented it for the L-1011, aiming for lower noise, better reliability, and higher efficiency than first-generation jets. The name TriStar came from a contest among Lockheed employees. All this advanced technology made the TriStar expensive. The TriStar's design had two aisles, room for up to 400 passengers, and three engines. Lockheed first thought of making it a "jumbo twin" with two engines, but chose three to give enough thrust for existing runways. Also, before the FAA set Extended Operations rules in the 1980s, two-engine jets could not fly more than 60 minutes from an airport, which ruled out trans-oceanic routes. The main visible difference between the TriStar and its rival DC-10 is where the center engine sits: the DC-10 puts it above the fuselage for simplicity and lower cost, while the TriStar buries it in the rear fuselage with air coming in through an S-duct, which cuts drag and improves stability. Lockheed kept pressure loss in the S-duct close to that of a straight duct by limiting the curve. Using the S-duct also made the airframe lighter than a straight-duct design would have. Research during the L-1011's design showed that the S-duct's losses were more than offset by these savings. Another big difference was that Lockheed chose the Rolls-Royce RB.211 as the only engine for the L-1011. The RB.211 was an advanced three-spool turbofan with a carbon fiber fan, promising better efficiency and power-to-weight ratio than competing engines like the General Electric CF6 used on the DC-10. In theory, the triple spool could match or beat double-spool engines while having a smaller cross-section that reduced drag. American Airlines showed strong interest in the L-1011 but ended up choosing the DC-10, after pushing Douglas to lower its price.