Boeing 727-200

The Boeing 727 is a narrowbody trijet developed to serve shorter routes and smaller airports than Boeing's larger 707. Boeing launched the program in 1960 with orders from Eastern Air Lines and United Air Lines, and the first 727 flew on 9 February 1963, entering service with Eastern in early 1964. The design used three rear-mounted Pratt and Whitney JT8D engines and advanced wing high-lift devices to combine jet speed with the ability to operate from relatively short runways.

The original model, retrospectively the 727-100, was soon joined by a stretched version. The 727-200 first flew in July 1967 and entered service with Northeast Airlines in December 1967, lengthening the fuselage by about six metres and increasing seating accordingly. A later development, the 727-200 Advanced, added higher operating weights, more fuel and greater range, and became the definitive version of the aircraft. The -200 series went on to account for the majority of all 727s built.

Through the 1960s and 1970s the 727 became a mainstay of US domestic aviation and a common sight internationally. Its ability to serve airports without extensive ground equipment, thanks to built-in airstairs, and its strong short-field performance made it versatile across a wide range of routes. It sold in large numbers: production ran until 1984 and totalled 1,832 aircraft, and the 727 is widely cited as the first jet airliner to exceed 1,000 sales, remaining the best-selling jetliner until it was overtaken by the Boeing 737.

The 727's rear ventral airstair, which folds down beneath the tail, features in one of aviation's best-known unsolved cases. In November 1971 a hijacker travelling under the name Dan Cooper, later widely known as D.B. Cooper, commandeered a Northwest Orient 727, collected a ransom of 200,000 US dollars, and parachuted from the lowered aft airstair while the aircraft was in flight; he was never identified. The incident prompted the fitting of a device, known as the Cooper vane, that prevents the aft airstair from being deployed while airborne.

The 727's commercial decline was driven mainly by economics and regulation. Its three older-generation engines burned more fuel than the newer twin-engine jets that succeeded it, and tightening noise rules made the type expensive to operate without hush kits or re-engining. US carriers progressively withdrew the 727 from passenger service through the 1990s and into the early 2000s; Delta Air Lines, among the last major US operators, retired its final 727s from passenger service in 2003. Many airframes went on to second careers as freighters, and a dwindling number remain in cargo, private or government use today.

The 727's defining feature is its three-engine tail arrangement. Two Pratt and Whitney JT8D engines are mounted in pods on either side of the rear fuselage, while a third is buried in the tail and fed by an air intake at the base of the vertical fin through an S-shaped duct. The horizontal stabiliser sits at the top of the fin in a T-tail layout, clear of the engine exhaust.

The wing was designed for both cruise efficiency and low-speed performance. It used a combination of leading-edge slats and Krueger flaps together with triple-slotted trailing-edge flaps, an unusually elaborate high-lift system for its time, giving the 727 good short-field capability and a steep approach ability. This let it serve shorter runways and airports that other jets of its size could not easily use.

For self-sufficiency at less-equipped airports, the 727 carried built-in airstairs, including a distinctive retractable stairway under the tail, so it could load and unload passengers without ground stairs or jet bridges. The fuselage shared its upper cross-section and six-abreast seating with the 707 and 737, which gave Boeing manufacturing commonality across the three types. An auxiliary power unit allowed the aircraft to operate independently of ground power.

In its heyday the 727 was operated by nearly every major US airline, including Eastern, United, American, TWA, Delta, Northwest and Braniff, as well as many carriers in Europe, Latin America, Asia and Africa. It served as a workhorse of domestic trunk networks and shorter international routes for decades.

As passenger operations wound down, large numbers of 727s were converted into freighters, and cargo operators kept the type flying well after airlines had retired it from passenger service. Today the 727 has essentially disappeared from scheduled passenger flying; only a small and shrinking number remain in service as freighters or in private, charter and government roles, often in parts of the world with less stringent noise regulation. Its legacy is that of one of the most widely produced and widely flown jetliners of its era.

The giveaway is the three-engine tail arrangement combined with a T-tail. Two engines sit in pods on the sides of the rear fuselage, and a third is buried in the tail, fed through an S-duct whose intake sits at the base of the vertical fin. The horizontal stabiliser is mounted at the top of the fin, well above the engines.

This layout separates the 727 from twin-engine rear-engined jets such as the DC-9 and MD-80, which look similar but have only two engines and no centre intake at the fin base. It also differs from four-engine jets like the 707 and DC-8, whose engines hang under the wings. The most similar-looking types are other trijets, notably the Hawker Siddeley Trident and the Soviet Tupolev Tu-154.