Boeing 767

Development

Background

In 1970, the 747 entered service as the first wide-body jetliner with a fuselage wide enough to feature a twin-aisle cabin. Two years later, the manufacturer began a development study, code-named 7X7, for a new wide-body jetliner intended to replace the 707 and other early generation narrow-body airliners. The aircraft would also provide twin-aisle seating, but in a smaller fuselage than the existing 747, McDonnell Douglas DC-10, and Lockheed L-1011 TriStar wide-bodies. To defray the high cost of development, Boeing signed risk-sharing agreements with Italian corporation Aeritalia and the Civil Transport Development Corporation (CTDC), a consortium of Japanese aerospace companies. This marked the manufacturer's first major international joint venture, and both Aeritalia and the CTDC received supply contracts in return for their early participation. The initial 7X7 was conceived as a short take-off and landing airliner intended for short-distance flights, but customers were unenthusiastic about the concept, leading to its redefinition as a mid-size, transcontinental-range airliner. At this stage the proposed aircraft featured two or three engines, with possible configurations including over-wing engines and a T-tail.

By 1976, a twinjet layout, similar to the one which had debuted on the Airbus A300, became the baseline configuration. The decision to use two engines reflected increased industry confidence in the reliability and economics of new-generation jet powerplants. While airline requirements for new wide-body aircraft remained ambiguous, the 7X7 was generally focused on mid-size, high-density markets. As such, it was intended to transport large numbers of passengers between major cities. Advancements in civil aerospace technology, including high-bypass-ratio turbofan engines, new flight deck systems, aerodynamic improvements, and more efficient lightweight designs were to be applied to the 7X7. Many of these features were also included in a parallel development effort for a new mid-size narrow-body airliner, code-named 7N7, which would become the 757. Work on both proposals proceeded through the airline industry upturn in the late 1970s.

In January 1978, Boeing announced a major extension of its Everett factory—which was then dedicated to manufacturing the 747—to accommodate its new wide-body family. In February 1978, the new jetliner received the 767 model designation, and three variants were planned: a 767-100 with 190 seats, a 767-200 with 210 seats, and a trijet 767MR/LR version with 200 seats intended for intercontinental routes. The 767MR/LR was subsequently renamed 777 for differentiation purposes. The 767 was officially launched on July 14, 1978, when United Airlines ordered 30 of the 767-200 variant, followed by 50 more 767-200 orders from American Airlines and Delta Air Lines later that year. The 767-100 was ultimately not offered for sale, as its capacity was too close to the 757's seating, while the 777 trijet was eventually dropped in favor of standardizing the twinjet configuration.

Design effort

In the late 1970s, operating cost replaced capacity as the primary factor in airliner purchases. As a result, the 767's design process emphasized fuel efficiency from the outset. Boeing targeted a 20 to 30 percent cost saving over earlier aircraft, mainly through new engine and wing technology. As development progressed, engineers used computer-aided design for over a third of the 767's design drawings, and performed 26,000 hours of wind tunnel tests. Design work occurred concurrently with the 757 twinjet, leading Boeing to treat both as almost one program to reduce risk and cost. Both aircraft would ultimately receive shared design features, including avionics, flight management systems, instruments, and handling characteristics. Combined development costs were estimated at $3.5 to $4 billion.

Early 767 customers were given the choice of Pratt & Whitney JT9D or General Electric CF6 turbofans, marking the first time that Boeing had offered more than one engine option at the launch of a new airliner. Both jet engine models had a maximum output of 48,000 pounds-force (210 kN) of thrust. The engines were mounted approximately one-third the length of the wing from the fuselage, similar to previous wide-body trijets. The larger wings were designed using an aft-loaded shape which reduced aerodynamic drag and distributed lift more evenly across their surface span than any of the manufacturer's previous aircraft. The wings provided higher-altitude cruise performance, added fuel capacity, and expansion room for future stretched variants. The initial 767-200 was designed for sufficient range to fly across North America or across the northern Atlantic, and would be capable of operating routes up to 3,850 nautical miles (7,130 km; 4,430 mi).

The 767's fuselage width was set midway between that of the 707 and the 747 at 16.5 feet (5.03 m). While it was narrower than previous wide-body designs, seven abreast seating with two aisles could be fitted, and the reduced width produced less aerodynamic drag.