AIRCRAFT
The first of Boeing's jetliners and the first US jet transport to enter service, the 707 (most commonly spoken as the "Seven Oh Seven") was a four-engined passenger jet developed by Boeing in the early 1950s. In order to become a new major player in the commercial airplane business, Boeing was quick to take notice of customers‚ desires, and although the 707 was not the first jet airliner in service (that distinction belongs to the De Havilland Comet), it was the first to be commercially successful.The 707 had its origins in design studies conducted by the company in the late 1940s and early 1950s for a new tanker for the USAF as a successor to the C-97/KC-97 family. From a number of turboprop and turbojet designs studied, Boeing selected its 367-80 for prototype construction, and this aircraft, which later became best known simply as the Dash 80, made its first flight on July 15, 1954, from Boeing‚s Renton facility, south of Seattle. Forerunner of the more than 14,000 Boeing jetliners built since, it was powered by four Pratt & Whitney JT3C turbojets. This engine was the civilian version of the J57 used on many military aircraft of the day including the F-100, F-101, F-102, and the B-52.
The 367-80 successfully demonstrated its potential to the U.S. Air Force, which subsequently purchased many hundred 367-80-derived KC-135A Stratotankers and related reconnaissance and special-purpose variants, similar in size and configuration to the prototype.
For more details of the 367-80, and the KC-135A tanker, please see below.
For airline use, however, Boeing made the late and costly decision to widen the fuselage by 6 inches (150 mm) so as to be a little wider than the Douglas DC-8. The new commercial project became identified as the model 707. With 13,000 lb (5,897 kg) thrust JT3C6 engines, the aircraft was offered in a long-body version, and a short-body version whose rear fuselage was 10 feet shorter and which had an increased range. It was the long-body version that Pan American World Airways chose when it placed a launching order on October 13, 1955 (more than three years after the Comet had become the first passenger jet to enter service - on May 2, 1952).
The first two 707s were flown on December 20, 1957, and February 3, 1958, and the model, which was capable of a seating 179 passengers, was certificated on September 23, 1958.
Commercial aviation history was made October 26, 1958, when Pan American made the first revenue flight of a 707, inaugurating transatlantic jet service between New York and Paris. However, the range of the airplane was not enough to cover the distance nonstop, and it made a stop at Shannon in Ireland.
American Airlines operated the first transcontinental 707 flight on January 25, 1959, and the 707 quickly became the most popular jetliner of its time, edging out its main competitor, the Douglas DC-8.
Boeing adopted a series of designation suffixes by which the first one or two number of a three-digit group indicated the model variant and the last one or two numbers served as a means of identifying the particular customer. Most early orders were for the so-called long-body variant of the 707 referred to as the 707-120, which had a MTOW of 257,000 lb.
Thus the model designation of Pan Am's 20-airplane launch order was 707-121 where the final 1 was Pan Am‚s reference number. Similarly, the model designation of American Airlines 30-aircraft order was 707-123. Qantas ordered 13 of the short-body version of the -120, and this model designation was 707-138, where 38 was Qantas‚ reference number. In total, 69 model -120s were built.
The 707's engines could not supply sufficient bleed air for pressurization without a serious loss of thrust, so the aircraft instead used engine-driven turbocompressors to supply high-pressure air for this purpose. 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 commercially successful airplane to use podded engines.)
With the same fuselage length as the long-body -120, the 707-220 introduced 15,800 lb. (7,167 kg.) thrust JT4A-3 or -5 engines. It was designed for hot and high operations, and the first flight was on June 11, 1959. Only five of these were ultimately 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.
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 a yaw damper system for the B-47, which lent itself 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 two of the four engines off the wing. The plane, a brand new 707-227 N7071 destined for Braniff, crash landed on a river bed north of Seattle at Arlington, Washington, killing four of the eight occupants.
In his autobiography, Boeing test-pilot Alvin "Tex" Johnston described a Dutch Roll incident he experienced as a passenger on an early commercial 707 flight. As the aircraft's movements gradually became more severe, he went to the cockpit and found the crew frantically attempting to resolve the situation. He introduced himself and relieved the ashen-faced captain who immediately left the cockpit feeling sick. Johnston quickly stabilized the plane, and later even landed it for the crew.
The same engines that were used on the model -220, or the more powerful 16,800 lb (7,620 kg) thrust JT4A-9 or 17,500 lb. (7,938 kg) thrust JT4A-11, were then adopted for the third model, the 707-320, which first flew on January 11, 1959. This had the fuselage lengthened by 100 inches to accommodate up to 189 passengers, and a larger wing to cope with the higher weights. With these improvements, which allowed increased fuel capacity from 15,000 gallons to more than 23,000 gallons, the 707 had a truly intercontinental range of over 4,000 miles (an increase of 1,600 miles) in a 141-seat (mixed class) seating configuration. Take-off weight was increased to 316,000 lb, and 69 model -320s were produced.
The 707-320 was followed on May 20, 1959, by the first 707-420. This was a version of the -320 originally produced at the specific request of BOAC (British Overseas Airways Corporation, now British Airways) and powered by Rolls-Royce Conway 508 turbofans, producing 17,500 lb (7,038 kg) each. Although BOAC initiated the program, Lufthansa was the launch customer and Air India was the first to receive the model on February 18, 1960. A total of 37 were built to this configuration.
In 1957 Boeing offered a short-medium-range version of the basic 707 aircraft designated the 720, featuring a fuselage 1 ft. 8 in. (0.51 m.) longer than that of the short-body 707-120 used by Qantas, a lightened structure, lower fuel capacity, 12,000 lb (5,443 kg) thrust JT3C-7 engines and extended chord on the inboard wing leading edges.
The 720 was originally designated the 707-020 but this was later changed for marketing reasons. It was designed for operation from shorter runways, and was faster than the 707. 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 until the Boeing 727 replaced it in the market. First flight was on 23 November 1959 and 64 of the original version were built.
In 1960 Boeing introduced the first major upgrade to the range by producing versions of the 707 and 720 with the newly developed JT3D-1-MC6 turbofan engines producing 18,000 lb thrust. These provided lower fuel consumption, reduced noise and further increased range to about 6,000 miles. The turbofan-engine models were identified by a B designation suffix. The 707-120B also received extra leading edge slats and the tailplane was enlarged. 72 of these were built, and many more were converted from 707-120 aircraft, including Qantas' aircraft, which thus became 707-138Bs. The first flight of the -120B was on June 22, 1960.
The first 720B flew on October 6, 1960. It had new low-drag wingtips with a span increase of 3 ft 3.5 in (1.0 m), and to improve takeoff and landing performance, it had slotted leading-edge flaps and improved trailing-edge flaps. Takeoff gross weight was increased to 235,000 lb. Eighty-eight of these were built in addition to conversions of existing 720 models.
The model 707-320B first flew on January 31, 1962. It had the same JT3D-3 turbofans as the 707-120B and incorporated many of the same airframe upgrades as well. Take off gross weight was increased to 335,000 lb. 175 of the 707-320B aircraft were produced, as well as upgrades from original -320 models. The US military designation for the cargo version of the 707-320B is C-18. 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.
Boeing also introduced the 707-320B Advanced. This had some minor improvements including 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 707-320C. This was a convertible passenger/freight configuration which ultimately became the most widely produced variant of the 707. It added a strengthened floor and a new side-loading 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. Despite the convertible option, a number of these were delivered as pure freighters. The 707-320C first flew on February 19, 1963.
As mentioned above, the first model of the Boeing 707 was certificated on September 23, 1958, and revenue service was inaugurated by Pan American on October 26, 1958 across the North Atlantic. Key dates for other variants were: Model 707-220, certificated on November 5, 1959, with first service by Braniff on December 20, 1959; Model 707-320, certificated on July 15, 1959, with first service by Pan American on October 10, 1959; Model 707-420, certificated on February 12, 1960, with first service by BOAC in May, 1960; Model 720, certificated on June 30, 1960, with first service by United on July 5, 1960; Model 707-120B certificated on March 1, 1961, and Model 720B certificated on March 3, 1961, with first services by American Airlines on March 12, 1961; and Model 707-320B, certificated on May 31, 1962, with first service by Pan American in June, 1963.
Three 707-120s and two 707-320Bs, all highly customized, were delivered to the Military Airlift Command of the U.S. Air Force for transporting high-profile government officials. Starting in 1962, the two 707-320Bs, designated VC-137s, formed the presidential fleet. "Air Force One" is the air-traffic-control call sign of any USAF aircraft carrying the President of the United States. While these planes are officially referred to as "Air Force One" only while the president is on board, the term is commonly used to describe either of the two aircraft normally used and maintained by the U.S. Air Force solely for the president. Since its inception, Air Force One has been a symbol of presidential power and prestige.
After operating in that role for more than 30 years, the two VC-137s were replaced in 1990 by two 747-200s designated as VC-25s. Each of these is capable of flying 12,600 km (7,800 miles) (roughly one-third the distance around the world) without refueling and can accommodate more than 70 passengers. Each VC-25A costs approximately US$325 million.
Later military applications of the 707 were the E-3 Airborne Warning and Control System or AWACS (used by the U.S. Air Force, NATO, the Saudi government and the British and French air forces for airborne surveillance, command and control) and the E-6 used by the U.S. Navy for submarine communications.
As the 1960s drew to a close, the exponential growth in air travel led to the 707 being a victim of its own success. It 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 747. The 707's first-generation engine technology was also rapidly becoming obsolete in the areas of noise and fuel economy.
Production of the passenger 707 ended in 1978. In total, 1,010 were built for civil use, though many of these later found their way to military service. The purpose-built military variants remained in production until May 1991.
The 707-700 was a test aircraft used to study the feasibility of using CFM International's CFM56 powerplants on 707 airframes and possibly retrofitting them to existing aircraft. After testing in 1979, the last commercial 707 airframe N707QT, 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 this test program, since they felt it would be a threat to their 757 program. The information gathered in the test, however, 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 707s.
Other variants, some with lengthened fuselages, designated up to 707-820, also remained in the project stage.
As of October 2006, 68 model 707s were reported to be remaining in airline service and many more are still flying, mainly aircraft converted for air freight transport and also some military aircraft.
Traces of the 707 are found in the 727 and 737, which use a modified version of the 707's fuselage, as well as essentially the same external nose and cockpit configuration. The Boeing 757 also uses the 707 fuselage cross-section.
Model 367-80
The 367-80, nicknamed the "Dash 80," was the prototype from which the 707 was developed. The go-ahead to build it was announced by Boeing on August 30, 1952, as a company-financed $16 million investment. The one-off airplane rolled from the factory less than two years later, on May 14, 1954. Its first flight from Renton Field, south of Seattle, on July 15 marked the 38th anniversary of The Boeing Company. Powered by four Pratt & Whitney 10,000 lb (44 kN) thrust JT3C turbojets, mounted in pods under wings swept back 35 degrees, the Dash 80 established the classic configuration for jetliners to come.
At Seafair on August 6, 1955, Tex Johnston, the Boeing test-pilot, performed a barrel roll in the Dash-80 at 500 feet. This story appears on a video called 'Frontiers of Flight - The Jet Airliner,' produced by the National Air and Space Museum in association with the Smithsonian Institution in 1992. The roll can be viewed on video at AviationExplorer.com. To date Johnston is the only pilot to have performed this in a four engine jet transport. (Other big four engine jet aircraft have done barrel rolls; for instance, the Avro Vulcan XA890 was rolled by Roly Falk on the first day of the 1955 Farnborough Air Show, but it was a bomber).
The Dash-80 also set new speed records. One such was on March 11, 1957, when it flew nonstop on a press demonstration flight from Seattle to Baltimore in 3 hours 48 minutes at an average speed of 612 mph.
During its early years, the airplane was the center of attraction in the aviation world, giving many airline pilots, airline executives, and military and government officials their first taste of jet flying.
The model was retained as a Boeing test aircraft and underwent major structural and aerodynamic changes in the course of developing and testing advanced aircraft features. Many test programs were aimed far beyond aircraft flying today, such as airborne simulation of flight characteristics and systems concepts for a U.S. supersonic transport.
The Dash 80 flew with a fifth engine mounted on the aft fuselage to test installation feasibility for the tri-jet 727, and with three different types of engines installed at the same time. It investigated engine thrust-reversers, engine sound-suppressors, rigs designed to cause in-flight engine icing conditions, air conditioners, and wing flap and slat modifications.
It was also used to test radar and radar antennas, and even different paints. In one test series for landing gear, it was outfitted with oversized tires; it landed and took off from mud fields barely able to support the weight of passenger automobiles.
It also flew special landing-approach studies at Moffett Field, California, for the National Aeronautics and Space Administration. A high-lift, slow speed system featuring special wing flaps for direct-lift control was used in steeper-than-usual landing approaches designed to alleviate community noise in airport areas.
After accumulating approximately 3,000 hours of flight over a period of 18 years, it was turned over to the Smithsonian Air and Space Museum in May 1972.
In May 1990, under an arrangement with the Smithsonian, Boeing returned the airplane to Seattle for full restoration after it had spent 18 years in the Arizona desert. The refurbished Dash 80 made a special fly-over of the five Boeing facilities in the Puget Sound area on July 15, 1991, to commemorate the 75th anniversary of The Boeing Company and the 37th anniversary of its own first flight. The airplane is now on view at Boeing Field.
Another aircraft type that traces its ancestry to the 707 prototype is the U.S. Air Force KC/C-135 tanker-transport/cargo airplane, similar in size and configuration to the prototype. Boeing built 820 of these aircraft for the Strategic Air Command and the Military Air Transport Service (predecessor of the Military Airlift Command). The KC/C-135 series was initially designated within Boeing as the model 717. In January 1998, the 717 model number was reassigned to the commercial line for the MD-95 regional jetliner following Boeing's merger with McDonnell Douglas.
Following the success of the 707, Boeing went on to develop a whole family of commercial jetliner models. Today, Boeing jetliners account for a large majority of the world's commercial jet fleet.
Total deliveries of the civil 707 were 1,010. As of October 2006, 68 Boeing 707 aircraft (of any variant) were reported to be remaining in airline service.
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