The 707 Family

The Boeing 707, the pioneer of the sweptback wing which included podded engines, borrowed from the B-47 military bomber, was the plane that really ushered the Jet-Age. Early 1950, together with its rival the Douglas DC-8, they were largely responsible for the explosive growth of air travel at prices the average citizen could afford. It also enabled Boeing to take the lead from Douglas as the world’s leader in commercial air transport. The 707 fuselage size set the standard for three more highly successful Boeing projects such as the B727, B737 and B757.
The "Seven Oh Seven" laid the foundation for Boeing’s preeminence of the worlds jetliner market during the 1980s and 90s, although Douglas with its sleek DC-8 jetliner gave the Seattle based manufactory a hard race. Boeings final 707 production total was nearly double the numbers of the DC-8, although 10% were dedicated military airframes. (A total of 1,010 were delivered) Boeing also offered a smaller, faster version of the aircraft that was marketed as the Boeing 720.
Although only a single company still operates the 707 in a passenger configuration, the type remains popular with numerous all cargo operators. The one-time ruler of the airways now remains active in military service. Although it was not the first commercial jet in service, the 707 was the first to be commercially successful, and is generally credited as ushering in the Jet Age.

Development

The 707 was based on an aircraft known as the 367-80. The "Dash 80" took less than two years from project launch in 1952 to rollout on 14 May 1954. This was powered by the Pratt & Whitney JT3C engine, which was the civilian version of the J57 used on many military aircraft of the day, including the B-52 bomber.

The prototype was conceived for both military and civilian use: the USAF was the first customer for the design, using it as a KC-135 Strato-tanker midair refueling platform. It was far from certain that the passenger 707 would be profitable. At the time, Boeing was making nearly all of its money from military contracts: its last passenger transport, the Boeing 377 Stratocruiser, had netted the company a $15 million loss before it was purchased by the Air Force as the KC-97 Stratotanker.

The 132 inches (3,350 mm) fuselage of the Dash 80 was only wide enough to fit 2+2 seating (in the manner of the Stratocruiser). Boeing soon realized that this would not provide a viable payload, so decided to widen the fuselage to 144 in (3,660 mm), the same as the KC-135 Stratotanker, which would allow six-abreast seating and the shared use of the KC-135's tooling. However, Douglas had launched its DC-8 project with a fuselage width of 147 in (3,730 mm). The airlines liked the extra space, and so Boeing was obliged to increase the 707's cabin width again, this time to 148 in (3,760 mm). This meant that little of the tooling that was made for the Dash 80 was usable for the 707.

The first flight of the first production 707-120 took place on 20 December 1957, and FAA certification followed on 18 September 1958. A number of changes were incorporated into the production models from the prototype. A Krueger flap was installed along the leading edge. The height of the vertical fin was increased, and a small fin was added to the underside of the fuselage, and acted as a bumper during excessively nose high takeoffs.

While the initial standard model was the 707-120 with JT3C engines, Qantas ordered a shorter body version called the 707-138 and Braniff ordered the higher-thrust version with Pratt & Whitney JT4A engines, the 707-220. The final major derivative was the 707-320 which featured an extended-span wing and JT4A engines, while the 707-420 was the same as the -320 but with Rolls-Royce Conway turbofan engines, in response to a request from Air Canada. British certification requirements relating to engine-out go-around also forced Boeing to increase the height of the tail fin on all 707 variants, as well as add a ventral fin.

Eventually, the dominant engine for the Boeing 707 family was the Pratt & Whitney JT3D, a turbofan variant of the JT3C with lower fuel consumption as well as higher thrust. JT3D-engined 707s and 720s were denoted with a "B" suffix. While many 707-120Bs and 720Bs were conversions of existing JT3C-powered machines, 707-320Bs were only available as new-built aircraft as they had a stronger structure to support a maximum take-off weight increased by 19,000 lb (8,600 kg), along with minor modifications to the wing.

The final 707 variant was the 707-320C, (C for "Convertible") which was fitted with a large fuselage door for cargo applications. This aircraft also had a significantly revised wing featuring three-section leading-edge flaps. This provided an additional improvement to takeoff and landing performance, as well as allowed the ventral fin to be removed (although the taller fin was retained). 707-320Bs built after 1963 used the same wing as the -320C and were known as 707-320B Advanced aircraft.

Production of the passenger 707 ended in 1978. In total, 1,010 707s were built for civil use, though many of these found their way to military service. The purpose-built military variants remained in production until 1991. Traces of the 707 are still found in the 737, which uses a modified version of the 707's fuselage, as well as essentially the same external nose and cockpit configuration as the 707. These were also used on the previous Boeing 727, while the Boeing 757 also used the 707 fuselage cross-section.

Operational History

The first commercial orders for the 707 came on 13 October 1955, when Pan Am committed to 20 707s and 25 Douglas DC-8s, a dramatic increase in passenger capacity over its existing fleet of propeller aircraft. The competition between the 707 and DC-8 was fierce. Several major airlines committed only to the DC-8, as Douglas Aircraft was a more established maker of passenger aircraft at the time. To stay competitive, Boeing made a late and costly decision to redesign and enlarge the 707's wing to help increase range and payload. The new version was numbered 707-320.

Pan Am was the first airline to operate the 707; the aircraft's first commercial flight was from New York to Paris on 26 October 1958 with a fuel stop in Gander, Newfoundland. American Airlines operated the first domestic 707 flight on 25 January 1959. Airlines which had only ordered the DC-8, such as United, Delta and Eastern, were left jet-less for months until September and lost market share on transcontinental flights.

The 707 quickly became the most popular jetliner of its time. Its popularity led to rapid developments in airport terminals, runways, airline catering, baggage handling, reservations systems and other air transport infrastructure. The advent of the 707 also led to the upgrading of air traffic control systems to prevent interference with military jet operations.

As the 1960s drew to a close, the exponential growth in air travel led to the 707 being a victim of its own success. The 707 was now too small to handle the increased passenger densities on the routes for which it was designed. Stretching the fuselage was not a viable option because the installation of larger, more powerful engines would in turn need a larger undercarriage, which was not feasible given the design's limited ground clearance. Boeing's answer to the problem was the first twin aisle airliner the Boeing 747. The 707's first-generation engine technology was also rapidly becoming obsolete in the areas of noise and fuel economy.

Trans World Airlines flew the last scheduled 707 flight for passengers by a US carrier on 30 October 1983, although 707s remained in scheduled service by airlines from other nations for much longer. For example Middle East Airlines (MEA) of Lebanon flew 707s and 720s in front-line passenger service until the end of the 1990s. Since LADE of Argentina took its 707-320B from regular service in 2007, Saha Airlines of Iran is the last airline to keep 707s in scheduled passenger service. Saha's 707-320C is listed for the nightly domestic flight between Tehran and Kish Island as well as a weekly flight between Tehran and Mashhad on Friday morning plus ad-hoc flights to numerous other airports in Iran when needed, as of November 2008.

In 1984, a Boeing 720 that was flown by remote control was intentionally crashed at Edwards AFB as a part of the FAA and NASA Controlled Impact Demonstration program. The test provided peak accelerations during a crash. Honeywell operated the last Boeing 720 in operation in the United States, flying out of Sky Harbor airport in Phoenix. The aircraft had been modified with an extra engine nacelle to allow testing of a turbine engine at altitude, operating on special certification allowing it to be used for experimental use. The aircraft's experimental flight certification was set to expire in 2008, and the 720 is being replaced by a Boeing 757. This 720B was sadly scrapped on June 21 and 22, 2008.

         

The 707 family (Civilian use only)

367-80 (Dash-80): The original prototype jet transport layout. Used to develop the 707, it was fitted with four Pratt & Whitney JT3C engines producing 10,000 lbf (44.5 kN). First flight was 15 July 1954.

707-120: 69 of the first production 707s were built, with a longer fuselage and greater wingspan than the original Dash-80. A full set of rectangular cabin windows was included for the interior, which was capable of a seating 179 passengers. The version was designed for transcontinental routes and often required a refueling stop when used on the North Atlantic route. It was fitted with four Pratt and Whitney JT3C-6 turbojets, civilian versions of the military J57 model, which produced 12,500 lbf (55.6 kN) each, allowing a 257,000 lb (117,000 kg) takeoff gross weight. First flight was on 20 December 1954. Other major orders were the launch order for 20 707-121 aircraft by Pan American and an American Airlines order for 30 707-123 aircraft.

707-138: Qantas has been assigned the Boeing customer number of 38. The 13 -138 were based on the -120 but had a 10 ft (3.05 m) reduction to the rear fuselage and were capable of increased range.
707-220: Designed for hot and high operations with powerful Pratt & Whitney JT4A-3 turbojets, only five of these were produced. All were for Braniff International Airways and carried the model number 707-227. This version was made obsolete by the arrival of the turbofan-powered 707-120B.

707-320 Intercontinental: A stretched version of the turbojet-powered original model, powered by JT4A-3 turbojets producing 15,800 lbs each. The interior allowed for up to 189 passengers due to a 100-inch (2,500 mm) stretch, while a longer wing carried more fuel, increasing range by 1,600 miles (2,600 km) and allowing the aircraft to operate as true transoceanic aircraft. Takeoff weight was increased to 316,000 lb (143,000 kg). First flight was on 11 January 1958, and 69 turbojet -320s were produced.

707-120B: The first major upgrade to the design was a re-engined JT3D-3 turbofans, which were quieter, more powerful, and more fuel-efficient, producing 18,000 lbf (80.1 kN) each. The aircraft also received extra leading-edge slats, and the tail-plane was enlarged. A total of 72 of these were built, and many more were converted from 707-120 aircraft, including Qantas' aircraft, which became 707-138B aircraft upon conversion. The first flight of the -120B was on 22 June 1960.
707-320B: A re-engined version of the stretched a/c was undertaken in parallel with the -120B, using the same JT3D-3 turbofans and incorporating many of the same airframe upgrades as well. Takeoff gross weight was increased to 335,000 lb (152,000 kg). 175 of the 707-300B aircraft were produced, as well as upgrades from original -320 models. One of the final orders was by the Iranian Government for 14 707-3J9C aircraft capable of VIP transportation, communication, and in-flight refueling tasks.
707-320B Advanced: A minor improvement made available to -320B aircraft, adding three-section leading-edge flaps. These reduced takeoff and landing speeds, and also altered the lift distribution of the wing, allowing the ventral fin found on earlier 707s to be removed. The same wing was also used on the -320C.
707-320C: A convertible passenger/freight configuration which became the most widely produced variant of the 707, the -320C added a strengthened floor and a new cargo door to the -320B model. 335 of these variants were built, including a small number with up-rated JT3D-7 engines and a takeoff gross weight of 336,000 lb (152,000 kg). Despite the convertible option, a number of these were delivered as pure freighters.
707-420: A version of the 707-320 originally produced at specific request for BOAC and powered by Rolls-Royce Conway 508 turbofans, producing 17,500 lbf (77.8 kN) each. Although BOAC initiated the program, Lufthansa was the launch customer and Air India was the first to receive a 707-420 on February 18 1960. A total of 37 were built to this configuration.

707-700: A test aircraft used to study the feasibility of using CFM International's CFM56 engines on a 707 airframe and possibly retrofitting them to existing aircraft. After a testing in 1979, N707QT, the last commercial 707 airframe, was refitted to 707-320C configuration and delivered to the Moroccan Air Force as a tanker aircraft. Boeing abandoned the program, since they felt it would be a threat to the Boeing 757 program. The information gathered in the test led to the eventual retrofitting program of CFM56 engines to the USAF C-135/KC-135R models, and some military versions of the 707 also used the CFM56. Ironically the Douglas DC-8 "Super 70" series by Cammacorp did develop commercially, extending the life of DC-8 airframes in a stricter noise regulatory environment. So there are today more DC-8s in commercial service than there are 707s.
720: Originally designated 707-020 but later changed for marketing reasons, was a modification of the 707-120 designed for medium-range operation from shorter runways. It was lighter and faster than the Boeing 707 and had a simplified wing design. This model had few sales but was still profitable due to the minimal R&D costs associated with modifying an existing type. The 720 was used before the Boeing 727 replaced it in the market. First flight was on 23 November 1959, and 64 of the original version were built.

720B: The turbofan-powered version of the 720, with JT3D-1-MC6 turbofans producing 17,000 lbf (75.6 kN) each. Takeoff gross weight was increased to 235,000 lb (107,000 kg). 88 of these were built in addition to conversions of existing 720 models.

From Wikipedia, the free encyclopedia
Operators/Survivors Although 707s are no longer employed by major airlines, 19 aircraft remain in commercial use, mainly with air cargo operators.
As of January 2009, commercial operators of the Boeing 707 include: Hewa Bora (4), Saha Air (3), Sudanese State Avtn (2), Johnson Air (1), Aerogem (1), Azza (1), Beta Cargo (1), Mid Express (1), Etram Air Cargo (1), Libyan VIP (1), Romavia VIP(1), Sudan Airways (1), TAAT (1), Mali Government (1) and Wimbi Dira (1)
American actor John Travolta owns an ex-Qantas 707-138B, registration N707JT
A total of 69 examples are in service with non-airline operators.
Credit: Andre van Loon/ Guy van Herbruggen/Servaas Verbrugge www.airlinerlist.com
Black and White pictures + Boeing Adds: Jan Boon Collection
For a full list of operators and survivors see:
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