Questions tagged [boeing-707]

The Boeing 707 was a narrowbody quadjet airliner formerly produced by boeing; it was Boeing's first commercial jet. Though not the first jetliner, it became the first one to become commercially successful, and is credited with ushering in the jet age.

The 707 (alongside its sister, the KC-135 tanker aircraft) was developed from the one-off 367-80 (or "Dash 80"), a proof-of-concept for a Boeing jet-powered transport, which made its maiden flight on 15 July 1954. While the KC-135 was essentially a straight tanker conversion of the 367-80, the 707 was redesigned early in development to use a significantly-wider fuselage in response to customer demand, allowing it to use six-abreast seating (three columns of seats on each side of a single central aisle); the 707 also had longer wings than the 367-80.

First flying on 20 December 1957, and entering revenue service on 26 October 1958, the 707 was the fifth jetliner in the air (following the de-havilland-comet, Avro Canada Jetliner, sud-caravelle, and Tupolev tu-104), and the third in revenue service (after the Comet and Tu-104). 865 707s were built until production ended in 1979, plus 154 of the smaller, shorter-range boeing-720, a 707 derivative; military versions of the 707 remained in production until 1991.

In its early years, the 707 mainly competed with the Douglas dc-8, which entered service eleven months after the 707, along with (to a much lesser extent) the later models of the Comet.

Seven major civilian versions of the 707 were produced:

• The 707-120 was the first 707 version (produced from 1957 through 1960, and entering service in October 1958), which carried up to 189 passengers. Powered by Pratt & Whitney JT3C turbojet engines, it required a water-injection system in order to take off safely at maximum weight, and had a relatively short range (generally having to stop partway for fuel on transatlantic and transpacific routes). 63 were built (most of which were later converted to 707-120Bs), including seven 707-138s (a shorter-fuselage, longer-range 707-120 variant built especially for Qantas).
• The 707-320 was derived from the 707-120 by stretching the fuselage, the wings, and the vertical and horizontal-stabilizers, and replacing the engines with more powerful JT4A turbojets; the larger wings increased its fuel capacity compared to the 707-120, allowing it to fly transoceanic routes without making a fuel stop en route. Despite the longer fuselage, its maximum passenger capacity remained at 189 (as would that of all 707s until the 707-320C), the same as that of the 707-120. 69 707-320s were built from 1957 through 1963; the type entered revenue service in August 1959.
• The 707-220 featured the more powerful engines of the 707-320 (which it postdated, despite its lower version number), but without the latter version's various stretches. It was designed for so-called "hot and high" operations (operations from high-altitude airports under conditions of high ambient temperature, both of which decrease air density, and, thus, aircraft performance; an example would be Mexico City in the summer), but was quickly rendered obsolete by the advent of the 707-120B (see below), and only five were built (one of which was destroyed in a training accident before it could be delivered), all for Braniff, with the first entering service in December 1959.
• The 707-420 was the first turbofan-powered 707, using the Rolls-Royce Conway engine; it was otherwise identical to the 707-320, with the exception of a larger vertical-stabilizer, modified rudder controls, and a small ventral fin under the tail (all added to meet British certification requirements), the former two of which would be adopted as standard on all 707s. 37 707-420s were built from 1960 until 1963, all for foreign airlines, with the type entering service in March 1960.
• The 707-120B, which carried its first passengers in March 1961, was similar to the 707-120, but used Pratt & Whitney JT3D turbofans, which were quieter, more powerful, and more fuel-efficient than the 707-120's JT3Cs, had a larger tail, and used the more aerodynamically-efficient wing pioneered by the 720 instead of the original 707-120 wing. The water-injection system was also removed, as the more powerful engines eliminated the need for it. 78 707-120Bs were built new from 1960 through 1969, including six short-bodied, long-ranged 707-138Bs for Qantas (which were to the 707-120B what the original 707-138 was to the 707-120), but the changes could also be applied to already-built 707-120s, and 39 of the latter (including all seven 707-138s) were converted to 707-120B standard.
• The 707-320B was based off of the 707-320, with the "B" indicating - as with the 707-120B - that this was now a turbofan aircraft, using the same JT3Ds as the 707-120B. Unlike with the 707-120B, the 707-320B's other aerodynamic improvements (mainly drag-reducing modifications to the wings) could not be retrofitted to an already-built 707-320, and all 175 707-320Bs were new builds.
• The 707-320C was the final, and most-produced, civilian 707, with 335 being built up until 1979. It was designed to be easily converted from a passenger to a cargo aircraft and vice versa (hence the "C", for "convertible"); however, the vast majority were used (at least at first) solely as passenger aircraft. The 707-320C's maximum passenger capacity was greater than that of all previous 707 variants (219 rather than 189), due to it bearing a greater number of emergency exits.
• In the late 1970s, Boeing explored the possibility of building a new 707 variant: the 707-700, which would have been powered by the much more efficient General Electric/SNECMA CFM56 high-bypass turbofan. A single aircraft was built to 707-700 standard, but, after testing, it was converted to a 707-320C and sold; however, the experience gained with the CFM56 from the 707-700 program was put to valuable use when the U.S. Air Force began reengining its KC-135s (which are, you will recall, a close sister to the 707) with the CFM56, starting in 1980, and the CFM56 was also chosen to power all post-1980 military 707s.

Boeing removed the 707 from its product offerings in 1980 (except for the military variants). By then, the market it had originally filled had mostly passed to large widebody (twin-aisle) aircraft, such as the boeing-747, and the 707 was left without a direct replacement (although the boeing-757, introduced into service in 1983, comes close).

To learn more about the 707, see Wikipedia.