The Boeing 707 is a four-engine commercial passenger jet airliner developed by Boeing in the early 1950s. Its name is most commonly pronounced as "Seven Oh Seven". Boeing delivered a total of 1,010 Boeing 707s, which dominated passenger air transport in the 1960s and remained common through the 1970s. Boeing also offered a smaller, faster version of the aircraft that was marketed as the Boeing 720.
Although it was not the first commercial jet in service, the 707 was among the first to be commercially successful, and is generally credited as ushering in the Jet Age. It established Boeing as one of the largest makers of passenger aircraft, and led to the later series of aircraft with "7x7" designations.
The 707 was an outgrowth of the Boeing Model 367-80. The "Dash 80" took less than two years from project launch in 1952 to rollout on May 14, 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 F-100 fighter and the B-52 bomber.
The prototype was conceived as a proof of concept aircraft for both military and civilian use: the United States Air Force was the first customer for the design, using it as the KC-135 Stratotanker 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-inch (3.35 m) fuselage of the Dash 80 was only wide enough to fit two-plus-two seating (in the manner of the Stratocruiser). Answering customers demands and under Douglas competition, Boeing soon realized that this would not provide a viable payload, so decided to widen the fuselage to 144 in (3.66 m), 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 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 (3.76 m). This meant that little of the tooling that was made for the Dash 80 was usable for the 707. The extra cost meant the 707 did not become profitable until some years after it would have if these modifications had not been necessary.
The first flight of the first production 707-120 took place on December 20, 1957, and FAA certification followed on September 18, 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. British certification requirements relating to engine-out go-arounds 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 707-320B series enabled non-stop westbound flights from Europe to the US west coast.
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. The Chinese government sponsored development of the Shanghai Y-10 during the 1970s, which was a near carbon-copy of the 707; however, this did not enter production.
The first commercial orders for the 707 came on October 13, 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 October 26, 1958 with a fuel stop in Gander, Newfoundland. American Airlines operated the first domestic 707 flight on January 25, 1959. Continental Airlines introduced its first two 707 aircraft into scheduled service three months later--the first U.S. carrier to employ the type widely in domestic service. Airlines which had only ordered the DC-8, such as United, Delta and Eastern, were left jetless 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 October 30, 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 scrapped on June 21 and 22, 2008.
The 707's used engine-driven turbocompressors to supply high-pressure air for pressurization. The engines could not supply sufficient bleed air for this purpose without a serious loss of thrust. On many commercial 707s the outer port (#1) engine mount is distinctly different from the other three, as this is the only engine not fitted with a turbocompressor.
The Boeing 707 was the first jet airliner to use podded engines. The De Havilland Comet and Tupolev 104 had engines buried into the wing root.
The 707 wings are swept back at 35 degrees and, like all swept-wing aircraft, displayed an undesirable "Dutch roll" flying characteristic which manifested itself as an alternating yawing and rolling motion. Boeing already had considerable experience with this on the B-47 and B-52, and had developed the yaw damper system on the B-47 that would be applied to later swept wing configurations like the 707. However, many new 707 pilots had no experience with this phenomenon as they were transitioning from straight-wing propeller driven aircraft such as the Douglas DC-7 and Lockheed Constellation.
On one customer acceptance flight, where the yaw damper was turned off to familiarize the new pilots with flying techniques, a trainee pilot exacerbated the Dutch Roll motion causing a violent roll motion which tore three of the four engines off the wings. The plane, a brand new 707-227 N7071 destined for Braniff, crash landed on a river bed north of Seattle at Arlington, Washington, killing two of the four occupants.
In his autobiography, test pilot Tex Johnston described a Dutch Roll incident he experienced as a passenger on an early commercial 707 flight. As the aircraft's movements didn't cease and most of the passengers became ill, he suspected a misrigging of the directional autopilot (yaw damper). He went to the cockpit and found the crew unable to understand and resolve the situation. He introduced himself and relieved the ashen-faced captain who immediately left the cockpit feeling ill. Johnston disconnected the faulting autopilot and manually stabilized the plane "with two slight control movements".
Pratt & Whitney, in a joint venture with Seven Q Seven (SQS) and Omega Air, has developed the JT8D-219 as a re-engine powerplant for Boeing 707-based aircraft, calling their modified configuration a 707RE. Northrop Grumman has selected the -219 to re-engine the United States Air Force’s fleet of 19 Joint Surveillance Target Attack Radar System (E-8 Joint STARS) aircraft, which will allow the JSTARS more time on station due to the engine's greater fuel efficiency. NATO also plans to re-engine their fleet of E-3 Sentry AWACS aircraft. The -219 is publicized as being half the cost of the competing 707 re-engine powerplant, the CFM-56, and is 40dB quieter than than JT3D engines that are being replaced.
The 367-80 (Dash-80) was 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.
The 707-120 was the first production 707 variant. The vairant featured 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 refuelling 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 December 20, 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. The first revenue service of a 707 was on October 26, 1958. A total of 69 were built.
The 707-138 was based on the -120 but had a 10 ft (3.05 m) reduction to the rear fuselage and were capable of increased range. It was a variant for Qantas and included Boeing customer number of 38 for Qantas. A total of 13 -138s were built.
The 707-120B was the first major upgrade to the design was a re-engining with 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 tailplane 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.
The 707-220 was designed for hot and high operations with powerful Pratt & Whitney JT4A-3 turbojets, only five of these were produced, however only four were ultimately delivered with one being lost during a test flight. 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.
The 707-320 Intercontinental is a stretched version of the turbojet-powered original model, powered by JT4A-3 turbojets producing 15,800 lbst 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 January 11, 1958, and 69 turbojet -320s were produced.
The 707-320B is a re-engined, stretched version 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 inflight refuelling tasks.
The 707-320B Advanced iss a slightly improved version of the -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.
The 707-320C has 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 uprated 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.
The 707-420 is 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 programme, 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.
The 707-700 was a test aircraft used to study the feasibility of using CFM International's CFM56 powerplants 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. (This purchase was considered a "civilian" order and not a military one.) 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.
The 720 was originally designated 707-020 but later changed for marketing reasons. It 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. At one point in the promotion stage to airlines it was known as the 717, although this was the Boeing model designation of the KC-135 and remained unused for a commercial airliner until it was applied to the MD-95 following Boeing's merger with McDonnell Douglas.The 720 was used before the Boeing 727 replaced it in the market. First flight was on November 23, 1959 with 64 of the original version built.
The 720B was 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.
The militaries of the United States and other countries have used the civilian 707 aircraft in a variety of roles, and under different designations. (Note: The U.S. Air Force's C-135 Stratolifter is not a 707 variant, but was developed in parallel to the 707 from the original Boeing 367-80.). The Canadian Armed Forces also operated Boeing 707 with designation CC-137 Husky (707-347C) from 1972 to 1997.
The VC-137C variant of the Stratoliner was a special-purpose design meant to serve as Air Force One, the secure transport for the President of The United States of America. These models were in operational use from 1962 to 1990. The two aircraft remain on display: SAM 26000 is at the National Museum of the United States Air Force near Dayton, Ohio and SAM 27000 is at the Ronald Reagan Presidential Library in Simi Valley, California.
In the 1980s, the USAF acquired around 250 used 707s to provide parts for the KC-135E Stratotanker program.
Although 707s are no longer employed by major airlines. 63 aircraft remain in commercial use, mainly with air cargo operators. As of August 2007, commercial operators of the Boeing 707 with more than one aircraft include: African Airlines International (4), Air Charter Express (2), Angola Air Charter (3), Azza Transport (2), Beta Cargo (4), Hewa Bora Airways (3), Interair (2), Iraqi Airways (2), Libyan Arab Airlines (4), Saha Airlines (4), Sky Aviation FZE (2), Skymaster Airlines (5), Sudan Airways (2), Sudanese States Aviation (2) and TMA (5). American actor John Travolta owns, and is qualified to fly as second in command, an ex-Qantas 707-138B, registration N707JT.
The list of customer codes used by Boeing to identify specific options and trim specified by customers was started with the 707, and has been maintained through all Boeing's models. Essentially the same system as used on the earlier Boeing 377, the code consisted of two digits affixed to the model number to identify the specific aircraft version. For example, Pan American Airlines was assigned code "21." Thus a 707-320B sold to Pan Am had the model number 707-321B. The number remained constant as further aircraft were purchased, thus when Pan American purchased the 747-100 it had the model number 747-121.
Accidents and incidents
As of May 2007, the 707 has been in a total of 166 hull-loss occurrences with 2,733 fatalities.
Aircraft on display
The 707 is mentioned in the songs "Boeing Boeing 707" by Roger Miller; "Jet Airliner" performed by The Steve Miller Band and written by Paul Pena; and "Early Morning Rain," written by Gordon Lightfoot and popularized by artists such as Elvis, Bob Dylan, and Peter, Paul and Mary.
Published in July 2009.
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